Waipi o Valley Flood Damage Reduction and Stream Stabilization Preliminary Investigation

Transcription

1 Prepared for: Prepared by: Mauna Kea Soil and Water AECOM Conservation District Honolulu, HI Kamuela, HI January 2012 and Stream Stabilization Preliminary Investigation

2 Prepared for: Prepared by: Mauna Kea Soil and Water AECOM Conservation District Honolulu, HI Kamuela, HI January 2012 and Stream Stabilization Preliminary Investigation Prepared By Stephen Blanton, PE, CFM Reviewed By Ardalan Nikou, PE

3 EXECUTIVE SUMMARY The Waipi o Valley and Wailoa Stream are repeatedly exposed to rapid influxes of sediment from frequent landslides in the upper valley. As sediment is transported downstream into the lower valley where channel slopes are less, the larger bedload material is deposited within the channel. The result is channel migration as the stream adjusts to new flow paths. The November 2006 earthquake caused several large slope failures in the upper valley. The amount of sediment, gravels and large boulders entering the stream due to the earthquake has caused an increase in the instability of the valley. The project is intended to develop alternatives at the Kawashima Waterhead and Linda Beech Crossing that will provide solutions to stabilize the Wailoa Stream channel. At both locations, deposition and channel migration are adversely affecting the local taro farmers ability to supply adequate irrigation to the taro fields. Additionally, bank erosion is affecting levees designed to protect the fields during high flow events. Existing site conditions at the Kawashima Waterhead include a widening of the stream channel, which results in multiple flow paths and deposition of gravel. The original auwai (irrigation canal) has breached downstream of the waterhead, requiring repeated repairs, which consist of placing rocks to hold flow in the auwai. The Linda Beech Crossing site is used by local farmers to cross the Wailoa Stream in order to access fields on the west side of the valley. Historically, the stream channel in the area migrated across a wide swath. Recently, the stream migrated approximately 200-feet to the east, creating a new channel with a much steeper slope, which is capable of transporting the increased sediment load. The concern lies with what happens when the river corrects itself, perhaps by creating a new channel and adversely affecting adjacent taro fields and abandoning waterheads/ auwai. For both locations, multiple design alternatives were developed to establish a stable channel geometry, which will transport the sediment load through the project reach, while also providing reliable diversion of flow in the auwai. Using field-identified, stable stream sections as a blue print, bank full geometry for the two project sites were estimated, and design alternatives were developed to reconstruct stable channel geometry. To address the streambank erosion concerns at the two sites, the alternatives use rock vanes to redirect the erosive velocities of the stream away from the bank and into the center of the river. The vanes are also used to develop flow conditions within depositional zones to increase the sediment transport through the reach. Stakeholders reviewed the initial alternatives for the two sites. Following review of the alternatives, the stakeholders selected hybrids of the alternatives as the final site design, which involved elements of multiple alternatives. Table ES-1 below contains the estimated costs associated with each of the alternatives for the two project sites as well as the final selected designs. As presented, each alternative provides additional elements to the project site. ii

4 EXECUTIVE SUMMARY Table ES-1: Estimated Costs Associated with Each Alternative Alternatives Location Total Construction Cost Total for Design and Construction 1 Stable Channel Design Kawashima Waterhead $620,000 $790,000 2 Waterhead Re-design Kawashima Waterhead $820,000 $1,040,000 3 Including Rock Vanes Kawashima Waterhead $642,000 or $842,000 $870,000 or $1,070,000 4 Stabilize Current Channel Linda Beech Crossing $1,170,000 $1,490,000 5 Plug Side Channel Linda Beech Crossing $440,000 $560,000 6 Restore Old Channel Linda Beech Crossing $1,420,000 $1,800,000 Selected Design for Kawashima Kawashima Waterhead $830,000 $1,050,000 Selected Design for Linda Beech Linda Beech Crossing $870,000 $1,110,000 iii

5 CONTENTS EXECUTIVE SUMMARY ii ACRONYMS AND ABBREVIATIONS vii 1.0 INTRODUCTION BACKGROUND Kawashima Waterhead Linda Beech Crossing Previous Studies STAKEHOLDER INPUT EXISTING CONDITIONS INVENTORY AND ANALYSIS Bankfull Identification Kawashima Waterhead Field Observations Planform Particle Size Distribution Longitudinal Profile and Cross-section Linda Beech Site Field Observations Planform Particle Size Distribution Longitudinal Profile and Cross-section Stability Analysis Sediment Capacity Sediment Competency Hydrology Flood Frequency Estimates Flow Duration Hydraulic Modeling Downstream Boundary Condition Wailoa Stream Mouth Blockage HEC-RAS Modeling at Kawashima Waterhead HEC-RAS Modeling at Linda Beech Crossing ALTERNATIVES ANALYSIS Kawashima Site Sediment Transport and Streambank Stabilization Streambank Erosion Protection Linda Beech Site Sediment Transport and Streambank Stabilization Alternatives Determination and Description Kawashima Waterhead Linda Beech Site Comparison of Alternatives Work on Other Areas of Wailoa Stream PROJECT COSTS Considerations Site Access and Equipment Mobilization Material Availability Construction Estimates Potential Cost Impacts Estimated Costs for Design and Construction 6-2 iv

6 Contents 6.2 Estimated Costs for Planning and Permitting SELECTED ALTERNATIVES Kawashima Waterhead Linda Beech Crossing Final Design Complete Plans and Specifications Design-Build PERMITTING REQUIREMENTS NEPA Requirements National Pollutant Discharge Elimination System (NPDES) Permit for Storm water Associated with Construction Activities NPDES General Permit for Construction Activity Dewatering Effluent Department of the Army Permit Water Quality Certification, Section Stream Channel Alteration Permit Conservation District Use Permit Endangered Species Act Section 7 Consultation National Historic Preservation Act Section 106 Consultation PROJECT IMPLEMENTATION AND FUNDING OPPORTUNITIES Federal U.S. Department of Agriculture Natural Resources Conservation Service U.S. Fish and Wildlife Service U.S. Army Corps of Engineers U.S. Environmental Protection Agency National Oceanic and Atmospheric Administration Hawai i Congressional Delegation State of Hawai i Department of Health Department of Land and Natural Resources Coastal Zone Management Program Department of Agriculture Mauna Kea Soil and Water Conservation District State Legislature County of Hawai i Non Governmental Organizations Big Island Resource Conservation and Development Hawaii Community Foundation Other Foundations Implementation Process Water Committee Plan Preparation Environmental Review Design Permitting CONCLUSIONS REFERENCES 11-1 APPENDICES A B Stakeholder Meeting Notes Alternative Designs v

7 Contents C Conceptual Plans FIGURES 1 Vicinity Map Lo i in the Waipi o Valley Waipi o Valley Site Locations (Aerial Date 2002) Kawashima Waterhead with Manuwai Flow Split at Linda Beech Crossing Lane s Diagram Bare Valley Walls Resulting from Landslide Looking Upstream at the Kawashima Waterhead where Flows Reconverge Facing Towards Bank Erosion Area on the Left Bank above the Waterhead Looking Upstream from a Pool Located Just Upstream of the Flow Split Kawashima Waterhead Pebble Count Section Upstream of Kawashima Waterhead Section at the Flow Split of Kawashima Waterhead Looking Upstream from the Flow Split in the Active Channel Looking Downstream at the Right Split Channel Pebble Count Upstream at the Linda Beech Site Pebble Count Downstream at the Linda Beech Site Cross-section Upstream of Flows Split at Linda Beech Site Cross-section of Left Split Channel at Linda Beech Site Cross-section of Right Split Channel at Linda Beech Site Kawashima Site, Unit Stream Power (lb/ft/sec) vs. Discharge (cfs) Linda Beech Site, Unit Stream Power (lb/ft/sec) vs. Discharge (cfs) The Wailoa Stream Watershed Island of Hawai i Hydrologic Regions Flow Duration Curve for the Wailoa Stream Waipi o Valley Hydraulic Model Layout Kawaihae Tide Prediction for Late May Accumulated Material at Wailoa Stream Mouth Wailoa Stream Accumulated Material Modeled in HEC-RAS Wailoa Stream Water Surface Profile HEC-RAS Results at Kawashima Waterhead Site HEC-RAS Results at Linda Beech Crossing Site Stable Cross-section Upstream of Kawashima Waterhead Site Existing Cross-section at Kawashima Waterhead Site 5-3 vi

8 Contents 36 Typical Cross-section of Proposed Conceptual Cross-Section at Kawashima Waterhead Unit Stream Power versus Discharge Relationship of Upstream Stable Section Compared with Proposed Typical Section Detail of Soil Layer Lifts Method of Streambank Stabilization (Source - VDEQ 2004) Typical Vane (J-Hook type) Configuration (Source - NRCS 2007) Typical Cross-section for Implementation on Left Branch of Linda Beech Site Unit Stream Power versus Discharge Relationship of Upstream Stable Section Compared with Proposed Typical Section Example Detail of a Permanent Ford 5-12 TABLES 1 Additional Studies Related to the Waipi o Valley Planform Characteristics for the Two Project Sites Geomorphic Properties of the Wailoa Stream through the Kawashima Waterhead Site Planform Characteristics for Linda Beech Site Geomorphic Properties of Wailoa Stream through the Linda Beech Site Shear Stress Analysis of the Wailoa Stream at the Linda Beech and Kawashima Properties USGS Wailoa Stream Flow Gage Summary Wailoa Stream Estimated Peak Flows Tidal Elevations for Kawaihae HEC-RAs Results for Kawashima Waterhead Project Reach HEC-RAS Results for Linda Beech Project Reach HEC-RAS Hydraulic Parameter Results at Kawashima Waterhead Flow Split Evaluation at Linda Beech Crossing Alternative Selection Evaluation for the Kawashima Waterhead Site Alternative Selection Evaluation for the Linda Beech Site Estimated Cost for Alternative No Estimated Cost for Alternative No Estimated Cost for Alternative No Estimated Cost for Alternative No Estimated Cost for Alternative No Estimated Cost for Selected Design at Kawashima Waterhead Site Estimated Cost for Selected Design at Linda Beech Site 7-3 vii

9 ACRONYMS AND ABBREVIATIONS % percent ARMD Agricultural Resources Management Division BIRC&D Big Island Resource Conservation and Development BKF bankfull BMP Best Management Practice CDUP Conservation District Use Permit cfs cubic feet per second Crest Coastal Resilience Networks CWA Clean Water Act CWB Clean Water Branch CWRM Commission on Water Resource Management CY cubic yard CZM coastal zone management DA Department of the Army DBEDT Department of Business, Economic Development and Tourism DLNR Department of Land and Natural Resources Dmax largest measured particle size DOA Department of Agriculture, State of Hawai i DOH Department of Health, State of Hawai i DPW Department of Public Works, County of Hawai i EA Environmental Assessment EIS Environmental Impact Statement EQIP Environmental Quality Incentives Program EWP Emergency Watershed Protection FONSI Finding of No Significant Impact fps feet per second ft feet foot ft/ft feet per foot ft 2 square feet HCF Hawaii Community Foundation HEC Hydrologic Engineering Center Hrs Hawaii Revised Statutes JD jurisdictional determination lb/ft 2 pounds per square foot LHD Lower Hamakua Ditch LiDAR light detection and ranging Lm meander length mi 2 square mile MKSWCD Mauna Kea Soil and Water Conservation District mm millimeter MOU memorandum of understanding NEPA National Environmental Policy Act NHPA National Historic Preservation Act NMFS National Marine Fisheries Service NOAA National Oceanic and Atmospheric Administration NOI Notice of Intent NPDES National Pollutant Discharge Elimination System NRCS National Resource Conservation Service NWP Nationwide Permit OCCL Office of Conservation and Coastal Lands PAS Planning Assistance to the States viii

10 Acronyms and Abbreviations RAS RC Rc/Wbkf SCAP SHPD SMP SSCBMP U.S. USACE USDA USFWS USGS WARSSS Wblt WHIP WO WQC WSE WSP River Analysis System radius of curvature ratio of radius of curvature to bankfull width Stream Channel Alteration Permit State Historic Preservation Division Stream Management Plan Site-specific Construction Best Management Practices United States United States Army Corps of Engineers United States Department of Agriculture United States Fish and Wildlife Service United States Geological Survey Watershed Assessment of River Stability and Sediment Supply belt width Wildlife Habitat Incentives Program Watershed Operations Water Quality Certification water surface elevation Watershed Surveys and Planning ix

11 1.0 INTRODUCTION Waipi o Valley, on the northern coast of the Island of Hawai i (Figure 1), is an important cultural and economic resource to native Hawaiians, the County of Hawai i, and the State of Hawai i. Native Hawaiian cultural traditions place Waipi o as the wellspring of the political dynasties that consolidated power in the islands, and as the source of the traditional kalo-based society and economy. The Wailoa Stream system, which winds through Waipi o Valley and outlets at Waipi o Bay, is one of the most managed stream segments in the state. Hawaiians have cultivated kalo for over 1,000 years in Waipi o, sustaining populations in the thousands. Management of the dynamic stream processes and equitable allocation of water for irrigation required intensive and sophisticated management to successfully continue kalo production for a millennium. The decline of traditional cultural practices and conversion to modern forms of kalo cultivation came with the transition to single farmers with less communal involvement in farming. The traditional methods to manage the stream and to make and implement water allocation decisions also have suffered. A number of damaging floods in the past 50 years have made farmers keenly aware of the need to manage the river system to protect their fields against severe flood effects and to recover quickly from inevitable flood events. Floods in 1979, 1986, and 1989 caused considerable damage to taro lo i by avulsion of the stream and deposition of bedload in the lo i. During much of the 20th century, farmers used heavy equipment, such as bulldozers, in the river system to remove gravel bars and to repair streambanks following a storm for flood protection of the taro lo i. In the 1990s, complaints to the United States (U.S.) Army Corps of Engineers (USACE), under provisions of the Clean Water Act (CWA), halted the ability of farmers to manage the river with heavy equipment. Since the cessation of unpermitted mechanical stream maintenance, the natural stream tendencies for braiding in some reaches and meander in other reaches have increased the flooding and erosion problems for many taro farmers. The Waipi o kalo farmers are attempting to organize themselves and develop modern environmental principles to manage the streams in Waipi o to support kalo cultivation, while being mindful of traditional practices. They have requested stream analysis, sustainable solutions to flooding and bank erosion, and assistance to complete permit applications and execute the terms of the permits. The U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS), in partnership with other organizations, such as Friends of the Future and the Mauna Kea Soil and Water Conservation District, has assisted the Waipi o farming community to progress toward their stream management goals. In 1999, at the request of the Waipi o Taro Farmers Association, Waipi o Valley was included in the project area for the NRCS Lower Hamakua Ditch (LHD) Watershed project. NRCS offered technical assistance to the Waipi o taro farming community for stream management and maintenance activities. In 2006, NRCS, with significant stakeholder input, completed the Waipi o Valley Stream Management Plan (SMP), which provides a framework for stream management to increase resilience of the taro lo i and farm improvements to flood damage. The SMP provided the contacts and processes for acquiring permits for maintenance activities and discussed the community organization s need to implement the management plan. The SMP identified the major problem areas for Waipi o farmers. The problem areas included: The blockage at the rivermouth, which increased flooding in the lower part of the valley. Gravel bars and islands in the midstream, approximately one mile upstream of the rivermouth, are reducing flood capacity and are causing bank erosion, including bank erosion near the Kawashima farm. 1-1

12 The unstable road crossing that requires constant maintenance. The intake to the major auwai system at the Kūnaka split is unstable and is threatening to direct the river into the auwai system. The meandering stream reach near the Linda Beach Crossing, which has caused considerable damage due to streambank breaches that pour floodwater and bedload into neighboring taro lo i. In 2009, NRCS assisted the Waipi o community in acquiring the necessary permits and approvals to clear the sand and rocks from the rivermouth to reduce flood damage and lower the stream surface elevation by as much as 5 feet (ft). This effort was conducted in partnership with the State of Hawai i Civil Defense, which was able to extend the State s Emergency Declaration for the October 2006 earthquake. The present study focuses on two of the most severe problem areas identified in the SMP. The study will develop conceptual solutions or alternatives for the stream problems near Kawashima farm and at the Linda Beach Crossing. 1-2

13 January 2012 Figure 1: Vicinity Map 1-3

14 2.0 BACKGROUND The is concerned with providing a reliable source of irrigation water to the valley taro farmers from the Wailoa Stream, while also addressing approaches to reduce damages to property resulting from flooding events. The production of taro requires a steady flow of water to pass through the lo i (Figure 2), supplying needed nutrients to the growing plants. Flow from the Wailoa Stream is diverted to the fields throughout the valley using auwai (irrigation canals). The diversion point of each of the auwai is referred to as a waterhead. In the Waipi o Valley, waterheads are generally cut through the existing stream bank to connect the river and irrigation system. Flow diverted from the river into the fields is returned to the river after passing through the fields. Figure 2: Lo i in the Waipi o Valley As identified in the Request for Proposal, the efforts associated with this project will investigate alternatives for reducing flood damage and stream erosion, with the goal of adding protection for the water supply system in the valley. For this project, efforts will focus on two sites: the Kawashima Waterhead and Linda Beech Road Crossing. Figure 3 illustrates the location of the two sites within Waipi o Valley. 2-1

15 Figure 3: Waipi o Valley Site Locations (Aerial Date 2002) 2.1 KAWASHIMA WATERHEAD The Kawashima Waterhead site is experiencing channel migration and bank erosion within the stream reach. Channel migration has resulted in multiple channels and both vegetated and gravel islands. The multiple channels and islands have directly affected the waterhead s ability to maintain adequate irrigation levels to the taro farmers. Current mitigation efforts require manual placement of a manuwai (rock weir) in the channel to maintain the water level at the waterhead. Figure 4 shows the hand-placed rock material. 2-2

16 Figure 4: Kawashima Waterhead with Manuwai Downstream of the waterhead, bank erosion is threatening the stability of levees and the stream bank that protect the taro fields during high flow events. Large trees have grown along the levees and the natural bank. As the banks continue to erode, many of the trees are being undercut, threatening failure of the bank and resulting in the tree falling into the river. Trees falling into the river may result in localized flow conditions that increase the likelihood of bank erosion. The project goal for the Kawashima site is to return the stream to a historic condition so that the waterhead functions appropriately without continual placement of rock in the channel, and to protect the small levees downstream of the waterhead. 2.2 LINDA BEECH CROSSING The Linda Beech Crossing site refers to a ford used to drive across the stream to access farmland on the other side. The channel in the area is unconfined and historically meandered across the valley. As the river abandons channels and creates new ones, flows are divided between two or more channels and the river channel invert adjusts. The changes in the river channel location and elevation adversely affects the ability of local auwai to divert flows. Taro farmers in the area are currently concerned that the river migration increases the chance that high flows may be directed toward existing lo i. Past flooding events that have reached lo i have resulted in crop loss and damage to farm facilities. Currently upstream of the crossing, a manuwai (Figure 5) has been placed by farmers. 2-3

17 Figure 5: Flow Split at Linda Beech Crossing The project goal at the Linda Beech Crossing site is to develop an approach to maintain the stream in a control zone in order to provide greater protection of property and crops as well as providing a reliable access location across the Wailoa Stream. 2.3 PREVIOUS STUDIES The issue of maintaining the Wailoa Stream and protecting taro production has been ongoing for many years. Previous efforts have been conducted to investigate these issues and provide approaches for addressing the problems (Table 1). One of the goals of this project is to build off previous efforts related to the Waipi o Valley and the Wailoa Stream. Two recent studies, described below, have addressed the erosion and channel instabilities facing the valley. In these two studies, actions were prepared to remedy the site-specific issues. Since the two reports were published, the 2006 earthquake occurred, which affected the sediment volume and size distribution entering the Wailoa Stream system. Waipio Valley Planning Assistance to States Study Waipio, Hawaii (USACE 2002). This report provides technical support in the development of alternative plans for stream maintenance and flood control in the Waipi o Valley. The Kawashima and Linda Beech Crossing locations were identified in the study report. For the Kawashima site, the study identifies gravel bar development and streambank erosion as issues adversely affecting the site. At the Linda Beech Crossing location, the study also identifies the presence of gravel bars and channel instability. The study provides a list of proposed actions that generally focus on removal of the accumulated gravels. 2-4

18 Waipio Valley Stream Management Plan (NRCS 2006). The management plan was developed and finalized in 2006 by the NRCS. The plan s intended purpose is to assist the taro farmers and residents of the valley in maintaining the river and complex irrigation system in a manner that meets the needs of the valley community, while also addressing environmental and legal limits of available actions. The plan is an excellent resource on the history of the valley from both a cultural and environmental resources approach. Table 1: Additional Studies Related to the Waipi o Valley Year Document Title 1946 Stearns, H. T. and G. A. MacDonald Geology and Ground-Water Resources of the Island of Hawaii. Hawai i Division of Hydrography, Honolulu Lennox, C. G A report to the Trustees of the Bishop Museum on the resources of the Waipio Valley, Island of Hawaii, their past and present uses and an analysis of the problems facing their fuller use in the future. Honolulu; Bishop Museum (unpublished) 1970 MacDonald, G. A., A. T. Abbott, and F. L. Peterson Volcanoes in the Sea, The Geology of Hawaii. 2nd ed. Honolulu: Univ. of Hawai i Press 1975 Yoshimura, Phillip A Master Plan proposal for Waipio Valley, Hawaii. Hamakua District Development Council Cordy, Ross A Regional Synthesis of Hamakua District, Hawaii Island 1997 Englund, R. A. and R. Filbert Native and Exotic Organisms Study in the Kaiwainui, Alakahi, Koiawe, and Lanakea Streams, Lower Hamakua Ditch Watershed Project, County of Hawaii. Pacific Aquatic Environmental, Inc United States Department of Agriculture, Natural Resources Conservation Service (USDA NRCS) Lower Hamakua Ditch Watershed Plan and Final Environmental Impact Statement Englund, R. A. and D. J. Preston Biological Assessment of the Lower Hamakua Ditch on the Hawaiian Stream Fly and other Aquatic Insects. Hawai i Biological Survey, Bishop Museum. Honolulu: USDA NRCS. February 1999 Dizol, L., D. Hegger, H. Keehne, K. Kinjo, M. Le Maitre, K. McKeague, S. Prasai, A. Resture, C. Shen, and X. Xing. (1999). Waipi o Valley: Towards community planning and ahupua a management. Planning Practicum, Department of Urban and Regional Planning, University of Hawai i United States Department of Agriculture, Natural Resources Conservation Service (USDA NRCS) Wailoa River Trip Report Waipio Valley: Stream Overlaying Methodology 2001 The Waipio Valley Restoration Project: Hydrological and Biological Assessment of Wailoa River and Hi iawe Stream 2001 R. A. Englund, C. Imada, D. J. Preston, N. L Evenhuis, R. H. Cowie, C. Puttock, K. Arakaki, and J. Dockall Native and Exotic Organism Study: Lower Wailoa River, Waipi o Valley, County of Hawai i. Hawai i Biological Survey, Bishop Museum. Honolulu. November CWRM Stream Channel Alteration Permit for Removal of Gravel Bars 2002 Waipio Stream Cross Section Survey (2 parts) 2002 Department of Urban and Regional Planning (DURP) Waipi o Valley: Towards Community Planning and Ahupua a Management, Phase II. University of Hawai i. Honolulu Source: NRCS

19 3.0 STAKEHOLDER INPUT Recognizing and attempting to address the concern of all stakeholders to the greatest extent possible is key to developing successful projects. Due to the cultural, economic, and environmental importance of the Waipi o Valley, many groups are included as stakeholders for this project. These groups include federal, state, and local agencies, local farmers and landowners. A stakeholder s meeting was held prior to the beginning of major efforts associated with the Waipi o Valley project. The meeting was held on November 16, 2010 near the mouth of the Wailoa Stream. The AECOM project team, NRCS and Mauna Kea Soil and Water Conservation District (MKSWCD) personnel, and taro farmers attended the meeting. The purpose of the initial meeting was to obtain input from the people who may be directly affected by the project and to discuss the issues, history and concerns of the stakeholders. The outcome of the November 16, 2010 meeting was a list of concerns that would need to be addressed in the development and assessment of the project alternatives. The major project issues are listed below: Clearing of the rivermouth to reduce backwater flooding. Stakeholders are interested in keeping the approach simple. Sediment will be stored within the floodplain and used for road maintenance. The meeting minutes and list of attendees for the meeting is located in Appendix A. Stakeholder involvement also included a review of the interim project report as well as a decision on selected alternatives for the two project sites (Section 7.0). 3-1

20 4.0 EXISTING CONDITIONS INVENTORY AND ANALYSIS In order to understand the interaction between the river and the land within the Waipi o Valley and the impacts on the farming community, it is important to understand the natural dynamics of a river system. All river systems exist in a state of dynamic equilibrium, which refers to a system s ability to maintain a generally consistent balance related to a set of characteristics. Lane (1955) defined this balance in a river system as a relationship between sediment load, sediment size, stream slope, and discharge (Figure 6). Any change in one of these parameters will result in a natural adjustment in one or more of the other parameters to balance out the system. If the adjustment is not made, the result will be either degradation or aggradation of the river. Figure 6: Lane s Diagram For the Wailoa Stream, a major variable in the Lane relationship is sediment load and size. Because of the Waipi o Valley s steep valley walls, events of mass wasting and landslides can abruptly alter the volume and size of sediment entering the system. Figure 7 illustrates a typical slide within the valley. As the sediment from these slides work through the Waipi o Valley, the river system adjusts to allow the increased material load to be transported to the ocean. The ability of the river to transport the material being delivered from upstream can be described by its capacity and competency. Competency is a measurement of a river s ability to transport the largest particle delivered from upstream, while capacity is a measurement of the total volume or load of sediment that can be carried by the stream. Capacity can be evaluated based on a channel s unit stream power, while competency can be measured based on its shear stress. When the size and/or load of material delivered from the watershed exceeds the channel s current capacity and competency, the channel will seek an equilibrium by increasing its shear stress and unit stream power, which it does by adjusting its hydraulic geometry. These adjustments are accomplished through phenomenon such as avulsion to increase the slope and aggradation of the floodplain to increase the channel depth. The adjustments tend to have adverse consequences of bank erosion due to mid-channel and transverse 4-1

21 bar formations that redirect flows to the bank, etc. These processes are prevalent in the Waipio Valley and are the primary mechanisms causing channel avulsion and bank erosion. Figure 7: Bare Valley Walls Resulting from Landslide In October 2006, a larger earthquake occurred, centered near the north shore of the Island of Hawai i. The quake caused multiple landslides throughout the Big Island, including the Waipi o Valley. Figure 8 shows an example of how landslides provide increased sediment load to a river system. As shown in the photo, taken approximately 6 months after the quake, the river valley is still blocked with material. The remaining volume of material shown in the photo will continue to be transported downstream, influencing the dynamic equilibrium of the stream. Proposed solutions at the Linda Beech site and Kawashima Waterhead have been based on our understanding that this increase in bedload will continue to occur. The basis of these proposed solutions is to promote the transport of the increase in bedload size and volume through adjustments in channel geometry and planform. Additionally, the solutions present concepts that may be used in other problematic reaches of the Wailoa Stream. 4-2

22 Figure 8: Landslide Blocking Stream in Upper Watershed With an understanding of the natural processes occurring in the valley, the following analysis describes the existing site conditions, geomorphology and stream stability of the Wailoa Stream at the Kawashima Waterhead, the Linda Beech site and areas immediately upstream and downstream of these sites. The analysis is based on site observations and review of topographic and geomorphological data obtained during site visits in March and April of The geomorphic and channel stability analysis generally follows the methods described by Rosgen in Watershed Assessment of River Stability and Sediment Supply (WARSSS) (Rosgen 2006). 4.1 BANKFULL IDENTIFICATION Essential to any geomorphological evaluation of a river is the identification of the bankfull (BKF) elevation and discharge. BKF discharge is the flow that transports the majority of a stream s sediment load over time, and thereby forms and maintains the channel. The term BKF is often used interchangeably with other terms, including channel-forming discharge and effective discharge. However, in the river processes field, BKF has become the most widely used term to define the channel-forming flow. The BKF stage and its associated discharge serve as consistent morphological indices, which can be related to the formation, maintenance, and dimensions of the channel. The term BKF was initially used to describe the incipient elevation on the bank where flooding begins. In many stream systems, the BKF stage is associated with the flow that just fills the channel to the top of its banks, and at a point where water begins to overflow onto a floodplain. However, if a stream becomes incised because of changes in the watershed or anthropogenic changes to the 4-3

23 channel or floodplain, the BKF channel is often located at an elevation that is lower than the top of bank. The BKF stage of a river is found through identification of BKF indicators. Typically, BKF indicators are manifested in several river features, which include: Tops of the highest active depositional features such as point bars Slope breaks or changes in particle size distribution Evidence of inundation features such as benches Visible line where perennial or woody vegetation begins to grow above an area of deposition ( vegetation line ) When a river is incised or entrenched, several of the above indicators are required to identify and validate the BKF stage. Because all of these features are subject to variation along even a relatively short section of a river, one should select only those features that strongly indicate the presence of BKF. Once enough indicators have been identified and checked for consistency, the elevations of these indicators can be measured in the field, and plotted on a graph to determine the average BKF slope. BKF was identified on a field visit made in March of BKF features were typically manifested as the top of bank of the river and the tops of depositional areas, such as point bars. Some areas of the river are partially incised, in which case, BKF indicators coincided with a lower point than top of bank, usually the top of a depositional feature. Based on measurements of BKF elevation and geomorphic parameters of the Wailoa Stream, BKF discharge has been estimated at approximately 500 cubic ft per second (cfs). Since no gage data was available for the site, this value was obtained by using the Manning s resistance equation coupled with field measurements of slope, hydraulic radius, and the D84 particle size. 4.2 KAWASHIMA WATERHEAD The following discussion describes the geomorphology of the channel at the Kawashima Waterhead, based on analysis of data obtained by AECOM in March and April of Field Observations The Kawashima Waterhead site is characterized by a split in flow of the Wailoa Stream channel at a point where flows are diverted into an auwai that supplies water to the Kawashima lo i. The active channel is divided into several smaller channels: 1) a channel that flows to the left (looking downstream) and becomes an auwai to the Kawashima lo i and 2) the active channel of the Wailoa Stream to right. In addition, there is development of a smaller channel between these two that also receives some of the split flow. Approximately 164 ft downstream, a portion of flow from the left channel returns to the main channel through an auwai, converging back with the right channel into a single-thread channel (Figure 9). Throughout this area of split flow, significant deposition and aggradation of bedload in the channel is occurring. Most notably, there is an island located on the left branch of the channel between the splitting of flow and the waterhead. Based on the presence of mature tree growth on this island, it appears that it was once the relict left bank of the stream. In addition, a depositional bar, composed largely of gravel and cobble, is located on the right branch of the channel and appears to be a relatively recent deposit. A line of younger, woody vegetation confirms the recent aggradation and shift in alignment of the right bank floodplain. In addition to the areas of deposition, there is an area of significant bank erosion upstream of the waterhead on the left bank (looking downstream), where flows are directed towards the outside meander. This situation appears to have been created by the relatively tight meander bend and areas of split flow just downstream of the bank. A toppled java plum tree is located on this eroding bank (Figure 10). 4-4

24 Downstream of the waterhead, along the left bank, considerable bank erosion is occurring. The left bank contains a small levee that maintains high flows in the channel. During high flow event in the Wailoa Stream, BKF is not allowed to spread out over the floodplain, increasing shear stress along the banks. Upstream and downstream of the area of split flow, BKF was observed as coinciding with the top of bank of the channel (Figure 11). Within the area of split channels, BKF was observed as coinciding with the top of the vegetated island. Figure 9: Looking Upstream at the Kawashima Waterhead where Flows Reconverge 4-5

25 Figure 10: Facing Towards Bank Erosion Area on the Left Bank above the Waterhead 4-6

26 Figure 11: Looking Upstream from a Pool Located Just Upstream of the Flow Split In general, it was observed that the channel upstream and downstream of the flow split is adequately moving bedload material. However, in the area of the waterhead, there is significant aggradation as evidenced by the development of a depositional bar on the right channel. This is presumably due to the splitting of flows and the high volume of flow diverted into the auwai, which is likely decreasing the channel s ability to move sediment through the system. This presumption was analyzed in more detail with a competency and capacity analysis, and is further described in Section Planform An important element of a stream s geomorphology is its planform, which describes the pattern of a channel s bends and meanders as it moves across and down its valley. The four delineative criteria that are measured from a river s planform (sinuosity, meander wavelength, radius of curvature and belt width), were measured on the Wailoa Stream at the Kawashima site from aerial photography of the Waipi o Valley. The planform of the Kawashima site is characterized by a left-hand meander in the stream and a larger right-hand meander approximately 300 ft downstream, where flows reconverge. Generally, the planform of the Wailoa Stream through the Kawashima Waterhead area has smaller measurements of radius of curvature and belt width than elsewhere on the Wailoa Stream. The meander just before the flow split has a radius of curvature of approximately 63 ft. This radius is significantly lower than other parts of the Wailoa Stream upstream and downstream, where radii range between 185 ft and 411 ft. Similarly, the belt widths of the meanders though the Kawashima site range between 69 ft and 82 ft, whereas elsewhere on the Stream, they range from 100 ft to 356 ft. When belt widths and radius of curvature are low relative to a channel s BKF width, this can be a sign of instability and 4-7

27 channel adjustment. In particular, a ratio of radius of curvature to BKF width (Rc/Wbkf) less than 1.5 can indicate an extreme amount of near bank stress on a meander (Rosgen 2006). With an approximate BKF width of 50 ft, the Rc/Wbkf ratio of the meander just upstream of the Kawashima flow split is approximately 1.3. Thus, the high degree of near bank stress created by the tight meander may help to explain the extensive bank erosion that was observed. The planform variables, including channel sinuosity, are provided in Table 2. Table 2: Planform Characteristics for the Two Project Sites Site RC(ft) Wblt (ft) Lm(ft) Sinuosity Rc/Wbkf Kawashima Waterhead Other Parts of Wailoa Stream Lm RC Wblt meander length radius of curvature belt width Wblt/Bankfull Width Particle Size Distribution An analysis of a stream s particle size distribution is important in determining stability, calculating BKF discharge and mean velocity, and classifying the channel. To determine the particle size distribution at the Kawashima site, a standard 100-sample pebble count was performed in the streambed. The data shows that the active channel bed is largely composed of gravel and cobble with a small amount of sand. The median (D50) particle size of the bed is approximately 54.5 millimeters (mm), while the D100 (maximum particle size of the bed) is approximately 198 mm. The distribution of particle sizes is displayed in Figure 12. Figure 12: Kawashima Waterhead Pebble Count 4-8

28 4.2.4 Longitudinal Profile and Cross-section A longitudinal profile of the Wailoa Stream was surveyed from approximately 400 ft upstream of the flow split, and ending approximately 300 ft downstream of where the split channels reconverge. The data collected along this profile includes BKF elevation, channel thalweg, and water surface elevation. Analysis of the profile shows that, upstream and downstream of the waterhead there are noticeable pool and riffle features. However, within the waterhead area itself, there is a lack of consistent bedform in the channel. Moreover, there is noticeable decrease in the water surface slope of the channel from upstream to where the flow splits. Upstream of the flow split, the average water surface slope is approximately ft/ft, whereas in the split channels, the average water surface slope lessens considerably, with only about ft/ft in the right split channel at the waterhead. Downstream, where the channels converge, the water surface slope steepens again to approximately ft/ft. As shown in the stability analysis included in subsequent sections, this decrease in the water surface slope is likely a result of the splitting in flow at the site, as the channel bed has aggraded due to inability of the split channels to carry the sediment load being delivered from upstream. In addition to the longitudinal profile, cross-section data was obtained for the channel at the Kawashima site both upstream of the flow split and within the split channels themselves (see Figure 13 and Figure 14). Based on examination of these cross-sections, the stream is slightly incised and slightly entrenched throughout its entire length (entrenchment ratio of 4 to 12). This means that the stream is neither vertically constrained (incised) nor horizontally constrained (entrenched), and above-bkf flows can readily access the floodplain above the stream. However, in spite of this sign of relative stability, there is a noticeable difference in the channel sizes upstream of the waterhead and within the split channels, as was visually observed during field visits. The BKF width upstream, before the flows split, is approximately 42 ft with a cross-sectional area of approximately 94.2 square ft (ft 2 ) and a BKF mean depth of approximately 2.3 ft. In contrast, the right split channel at the waterhead has a BKF width of only approximately 20 ft, a BKF area of approximately 42 ft 2 and a BKF mean depth of approximately 2.1 ft. The width/depth ratio of the upstream channel is considerably higher at 18 compared with 9.3 downstream. Based on these parameters, the channel upstream of the flow split classifies as a C4 channel, according to the Rosgen system of Classification of Natural Rivers (Rosgen 2006). Downstream, the smaller width/depth ratios give the split channels a classification of an E4. The geomorphic parameters obtained from the pebble count, longitudinal profile, and cross-section are summarized in Table 3. Table 3: Geomorphic Properties of the Wailoa Stream through the Kawashima Waterhead Site. Reach Kawashima (Upstream) Kawashima (Right Split Channel) BKF Width (ft) Entrenchment Ratio Mean Depth (ft) Max Depth (ft) Width /Depth BKF Area (ft 2 ) D50 (mm) D100 (mm) Slope (ft/ft) LINDA BEECH SITE AECOM obtained geomorphological data of the existing channel in March and April of During these visits, a pebble count was obtained, and a longitudinal profile was surveyed. Cross-section data is a combination of field surveys and LiDAR. 4-9

29 Figure 13: Section Upstream of Kawashima Waterhead Figure 14: Section at the Flow Split of Kawashima Waterhead Field Observations The Linda Beech site, like the Kawashima Waterhead, is characterized by a splitting of streamflow that has created two active channels (hereafter referred to as left channel and right channel, facing downstream). Both the left and right channels flow for approximately 2,000 ft before converging downstream. Approximately 100 ft downstream of the split, a gravel road crosses the two channels at a ford. In addition to the two split channels, there is an abandoned relict channel to the 4-10

30 west, which branches off upstream of the road crossing. The relict channel is approximately 1,200 ft long before it joins with the left channel downstream. Analysis of historical aerial photographs show that the relict channel was active as recently as 2003 and was comprised of several meander bends that were bypassed by the currently active channel. The primary stream stability issue observed at the Linda Beech site is that the left split channel is significantly smaller than it is upstream and, as will be described in the next section, appears to lack the ability to transport the sediment load from upstream. Furthermore, it was observed that most of the flow is bypassing the right split channel and flowing into the left channel, further exacerbating the problem. Over time, it can be expected that the left channel will continue to aggrade and widen as it seeks a channel form with the necessary capacity to transport the sediment load. As with the Kawashima site, BKF was identified as typically coinciding with the top of bank and very little incision was observed, particularly upstream of the flow split (Figure 15). In addition, just upstream of the flow split, the channel appears to be stable and is actively moving its bedload. After the split, however, the left channel is significantly narrower than it is upstream, while the dimensions of the right channel are similar to the dimensions upstream (Figure 16). Figure 15: Looking Upstream from the Flow Split in the Active Channel 4-11

31 Figure 16: Looking Downstream at the Right Split Channel Planform The planform at the Linda Beech site is characterized by the presence of several meanders in the left and right split channels before they converge downstream. Generally, the left and right channels have slightly smaller radius of curvatures relative to other parts of the Wailoa Stream (with the exception of the Kawashima Waterhead). This may indicate higher amounts of near bank stress on some parts of these split channels. The planform parameters for these channels are summarized in Table 4, along with parameters for other stretches of the Wailoa Stream outside the Linda Beech and Kawashima sites. Table 4: Planform Characteristics for Linda Beech Site Site RC(ft) Wblt (ft) Lm)(ft) Sinuosity Rc/Wbkf Linda Beech Left Channel Linda Beech Right Channel Other Parts of Wailoa Stream Wblt/Bankfull Width ,

32 4.3.3 Particle Size Distribution To determine the particle size distribution of the Wailoa Stream through the Linda Beech site, pebble counts were obtained in both an upstream riffle section and downstream within the left split channel. The upstream pebble count shows that the bed upstream is relatively coarser than downstream, and consists of a mixture of gravel, cobble, and sand with some larger boulders and bedrock outcroppings. The median particle size (D50) from this count is approximately 38 mm. Pebble counts obtained in the downstream split show a somewhat less coarse channel than upstream, primarily composed of gravel, cobble, and sand. The median bed particle size here is similar to the median size upstream, at approximately 35 mm. However, the largest particle is smaller at approximately 186 mm. The distribution of particles from both pebble counts is shown in Figure 17 and Figure 18. Figure 17: Pebble Count Upstream at the Linda Beech Site Longitudinal Profile and Cross-section A longitudinal profile of Wailoa Stream was surveyed from the location where the main channel splits from the relict channel to approximately 200 ft downstream of the gravel ford, along the right channel. Analysis of this data shows a series of riffles and pools along this reach, with riffles generally steepening in the right channel compared with upstream. Pool depths were approximately 4 to 5 ft and riffles were approximately 2.5 to 4.5 ft deep. The average water surface slope appears to remain relatively constant throughout the profile, even after the splitting of flow, with an average slope of approximately 0.01 ft/ft. In addition to the longitudinal profile, cross-section data was obtained and examined for the Linda Beech site (see Figure 19 through Figure 21). Analysis of this cross-section data shows that, as was observed in the field, the channel upstream of the flow split is considerably larger than the left split channel. Upstream, the channel has a BKF width of approximately 42.4 ft, with an area of 110 ft 2 and a mean depth of approximately 2.6 ft. In contrast, the left split channel has a BKF width of approximately 19.5 ft, an area of 41.4 ft 2 and a mean depth of approximately 2.1 ft. Limited data was available for the right split channel and relict channels, however, they appear to be larger than the left channel. At the point where the channel splits, the right channel has a BKF width of approximately 46 ft, an area of approximately ft 2 and a mean depth of approximately 2.7 ft. 4-13

33 The relict channel appears wider, with a width of approximately 62 ft, an area of 103 ft 2 and a width/depth ratio significantly higher than upstream, at approximately 38 compared with 16. Figure 18: Pebble Count Downstream at the Linda Beech Site. Entrenchment ratios in the upstream channel, at approximately 24, indicate that the channel is not horizontally constrained within its valley. Based on this entrenchment value, the median particle size and the width/depth ratio measurements, the channel upstream of the split classifies as a C4 stream. The left split channel, with its lower width/depth ratio, classifies as an E4 stream. The right channel, similar to the upstream portion, classifies as a C4 stream. A geomorphic summary of this reach is shown in Table 5. Table 5: Geomorphic Properties of Wailoa Stream through the Linda Beech Site Location Linda Beech (Upstream Section) Linda Beech (Left Split Channel) Linda Beech (Right Split Channel) BKF Width (ft) Entrenchment Ratio BKF Mean Depth (ft) BKF Max Depth (ft) W/D BKF Area (ft 2 ) D50 (mm) D100 (mm) BKF Slope (ft/ft) Bedrock

34 Figure 19: Cross-section Upstream of Flows Split at Linda Beech Site Figure 20: Cross-section of Left Split Channel at Linda Beech Site 4-15

35 Figure 21: Cross-section of Right Split Channel at Linda Beech Site Stability Analysis A key to predicting river instability and associated loss of physical and biological function rests with the ability of a river to move the sediment size and load made available from its watershed. Transport physics, sediment size, sediment load, increases in the magnitude and duration of streamflow and the stability of streambanks and beds, all influence the contribution of sediment from channel processes (Rosgen 2006). How a stream will accommodate this delivered sediment load is dependent on the particle size and magnitude of the sediment load and the stream s competency and capacity to handle the load Sediment Capacity To further validate the stability issues observed in the Wailoa Stream at both the Kawashima and Linda Beech sites, a sediment transport analysis was undertaken using the POWERSED model, as described in the WARSSS methodology (Rosgen 2006). POWERSED uses data of channel geometry and slope, flow data from a gage site, and suspended sediment and bedload transport data to estimate the relative sediment transport capacity of a channel. The key to the model is the ability to compare an upstream, reference cross-section with a downstream, unstable crosssection. The reference cross-section must be a section that is considered relatively stable, in that it is moving the sediment load being produced by the watershed without aggrading or degrading. The model evaluates the relationship between unit stream power and sediment transport at the reference section, then uses this relationship with the calculated unit stream power of the altered section to evaluate whether the altered section has the capacity to move the sediment load being produced by the watershed. A channel that lacks the capacity to move the sediment load is expected to aggrade, while one with too much capacity is expected to degrade. To conduct the POWERSED analysis, reference cross-section data for the areas upstream of the Kawashima Waterhead and the flow split at the Linda Beech site were input into the software program RiverMorph. The program uses hydraulic measurements from the cross-section data, coupled with the BKF discharge and average water surface slope measurements to estimate the unit stream power of the channel at incremental stages up to the BKF stage. From the sediment rating 4-16

36 curve and flow duration curve, a relationship between sediment transport and unit stream power is developed. For the Wailoa Stream, a flow duration curve based on long-term recorded data was not available, nor was any data of suspended sediment and bedload collected due to time and budget constraints. However, since the goal of the stability analysis was a relative comparison of two sections rather than absolute estimates of sediment transport, assumed values based on site conditions were used for sediment and bedload material size. Additionally, the POWERSED model allows the use of a flow-duration curve from a river in a similar physiographic province, which has been normalized based on BKF discharge, to substitute for a flow duration curve of the actual river being studied. For this relative analysis, the flow duration curve from the Hanalei River on the Island of Kaua i was used and normalized based on the Hanalei s BKF discharge of approximately 4,000 cfs. At the Linda Beech site, a cross-section surveyed approximately 150 ft upstream of the flow split appeared to be a stable cross-section based on field observations. This was used as the stable section for the purposes of the POWERSED analysis. The downstream cross-section, for comparison at the Linda Beech site, was in the left split channel, which is approximately 400 ft downstream of the split. At the Kawashima Waterhead, the stable cross-section used was a section approximately 500 ft upstream of the waterhead, located on a riffle. Based on field observations, the section had no signs of instability. The unstable section used in the analysis was the right channel located at the waterhead, approximately 30 ft downstream of the split. For purposes of this analysis, the upstream and downstream cross-sections were assumed to have the same BKF discharge. In reality, however, the flow in the downstream cross-sections is split between several channels. Analyzing the downstream sections as though they were carrying the BKF discharge is necessary to understand how their current shape and slope deviates from the stable channel form. The POWERSED results show a reduction in sediment transport capacity in the split channels at both the Kawashima and Linda Beech sites. The cause of this reduction is apparent when looking at a graph of unit-stream power versus discharge for the upstream stable and downstream unstable channels (Figure 22 and Figure 23). Due to the smaller BKF area of the split channels compared with the upstream single-thread channel, there is a sharp reduction in unit stream power in the split channel. The flows enter the floodplain well before the upstream section, resulting in a significant reduction in velocity and stream power, with a resulting reduction in sediment transport capacity. At the Linda Beech site, the downstream split channel has a cross-sectional area of approximately 41.4 ft 2, while the channel upstream of the breach has an area of approximately 110 ft 2. At the Kawashima site, the downstream split channel has a cross-sectional area of approximately 42.3 ft 2, while upstream the area is approximately 95 ft 2. In addition, the decrease in slope at the Kawashima Waterhead, as described earlier, also contributes to the difference in sediment transport capacity between the upstream and split channels. 4-17

37 8 g ( ) Unit Power (lb/ft/s) Stable Discharge (cfs) Altered Figure 22: Kawashima Site, Unit Stream Power (lb/ft/sec) vs. Discharge (cfs) Figure 23: Linda Beech Site, Unit Stream Power (lb/ft/sec) vs. Discharge (cfs) Based on the results of the POWERSED analysis, the split channels at both the Kawashima Waterhead and Linda Beech site lack the necessary sediment transport capacity to move the sediment load of the Wailoa Stream, and can therefore be expected to aggrade and adjust until a stable channel form is reached. Any measures to stabilize the stream and prevent future aggradation at these locations should attempt to mimic the stable channel form found upstream Sediment Competency The objective of this analysis is to determine the required depth and/or slope of a stream channel necessary to move the largest particle made available from its upstream reach at the BKF stage. If the channel dimensions and slope are not sufficient to transport the largest particle size, aggradation potential exists. If the depth and/or slope create excess shear stress that potentially transports sizes 4-18

38 greater than the largest measured particle size (Dmax) of the bed, then potential degradation is predicted. A pebble count was obtained at both the Kawashima and Linda Beech sites, yielding maximum particle size measurements for these sites. Measurements of hydraulic radius and slope were obtained from cross-section and longitudinal profile data obtained at these locations. Using this data, sediment competency was evaluated using dimensional shear stress calculations by finding the critical shear stress that would be required to move the largest measured particle. Dimensional shear stress is found by the following equation: Where: Rs = shear stress (pounds per square ft [lb/ft 2 ]) = specific gravity of water (62.4 pounds per cubic ft) R = hydraulic radius (ft) s = average BKF slope (ft/ft) Calculations of critical shear stress were used with a relationship of shear stress to particle size as shown in the Shields relation (Leopold et al. 1964) and the Rosgen Colorado Data (Rosgen and Silvey 2005). Rosgen found that the Shields relation generally underestimates particle sizes of heterogeneous bed material in the shear stress range of 0.05 lbs/ft 2 to 1.5 lbs/ft 2, and developed a revised shields curve based on data collected in Colorado ( Colorado Data ). Where the critical shear stress fell within this range, the Colorado Data trendline was used in place of the Shields relation to determine the maximum moveable particle size. Competency was compared between upstream, stable sections, and downstream, split sections for both the Kawashima and Linda Beech sites. The same cross-sections as described above in the Sediment Capacity analysis were used. Table 6 displays the measurements of mean depth, water surface slope, the largest measured particle and the resulting critical shear stress at these sections along with the predicted largest moveable particle and the shear stress, mean depth and slope required to initiate movement of the largest measured particle. Table 6: Shear Stress Analysis of the Wailoa Stream at the Linda Beech and Kawashima Properties Location Linda Beech Upstream Section Linda Beech Split Channel (Left hand) Kawashima Upstream Section Kawashima Waterhead Section Hydraulic Radius(ft) Water Surface Slope (ft/ft) Critical Shear Stress (lbs/ft 2 ) Largest Measured Particle (Dmax) (mm) Predicted Largest Moveable Particle (mm) Predicted Shear Stress Required to Initiate Movement (lbs/ft 2 ) Predicted Mean Depth Required to Initiate Movement of Dmax (ft) Predicted Slope Required to Initiate Movement of Dmax (ft/ft)

39 These results indicate that the split channel at the Kawashima Waterhead lacks the necessary competency to move the largest particle being delivered from upstream (Dmax measured at 198 mm), whereas an upstream riffle section, which was observed to be stable, has the necessary competency to move the particle size. The change in competency is due to a drop in shear stress caused by a decrease in the slope and mean depth of the channel, and diversion of flow to the left split channel/ auwai. The width of the channel increases without a significant increase in crosssectional area at BKF, thus making the hydraulic radius, and consequently the shear stress, lower and decreasing the stream s ability to move large particles. At the Linda Beech site, the results indicate that the upstream channel has relatively sufficient competency to move the largest particle delivered from upstream without aggrading or degrading. The left split channel also appears to have sufficient competency to move the largest measured particle found in that reach, which is likely due to the lower width/depth ratio that is creating a relatively high hydraulic radius for the size of the channel. However, as shown in the capacity analysis, the smaller size of the channel, which lacks the capacity for BKF flow, over time, will not be able to move the sediment load delivered from upstream. Therefore, any repair work done at this location would be best to mimic the geometry of the upstream stable section to the maximum extent possible. This can be accomplished through either an increase in hydraulic radius or slope. A change in slope would require grading a new channel with an increased sinuosity, which would be a more labor-intensive and expensive undertaking, and not practical given the location of the channel. A change in hydraulic radius, on the other hand, could be accomplished simply by increasing the width and depth of the left split channel. 4.4 HYDROLOGY The Wailoa Stream watershed (Figure 24) covers an approximate area of 24.6 square miles (mi 2 ). The Wailoa Stream is 12.8 miles long, extending from the mouth in Waipi o Bay to its headwaters. Within the watershed, there are multiple United States Geological Survey (USGS) flow gages in the upper watershed, none of which provide a long-term record of the flow characteristics of the stream valley. The USGS did operate a flow gage on the Wailoa Stream (# ) sporadically within the last century. The location is shown on Figure 24, with a summary of the gage data presented in Table 7. Table 7: USGS Wailoa Stream Flow Gage Summary Gage ID Gage Name Drainage Area Period of Record Wailoa Stream near Waipi o, HI 14.3 mi i2 August 1901 January 1902 (prior to diversions) July 1911 December 1912 October 1964 September 1969 The quality of the recorded data was rated as poor by the USGS because of the short period of record and the multiple water diversions within the upper watershed Flood Frequency Estimates With limited available flow data available for the Waipi o Valley project area, the estimation of peak flows associated with various return periods was determined using regional regression equations. The estimated flows will be used in the hydraulic model of the Waipi o Valley waterways to estimate flow depths and velocities. These results are necessary for the development of conceptual-level mitigations for the Kawashima and Linda Beech project locations. 4-20

40 USGS Gage Figure 24: The Wailoa Stream Watershed In 2010, the USGS published the document, Flood-Frequency Estimates for Streams on Kaua i, O ahu, Moloka i, Maui, and Hawai i, (Oki et al. 2010). Using the available recorded stream flow gage data throughout the State, the USGS developed relationships between watershed size, annual precipitation, and peak flows related to flood events. The Waipi o Valley is located in the Hydrologic Region, Hawai i, Northern (Region 9) as shown in Figure 25. Based on the Region 9 regression equations resulting from the USGS efforts, peak flows were estimated at two locations within the Waipi o Valley. The Upper area flows represent flow rates tributary to approximately the Linda Beech Crossing project location. The Lower area flows represent flows for the entire watershed delineated from the mouth of Wailoa Stream. The flow peaks for the 2- through 500-year flood events are presented in Table 8. Table 8: Wailoa Stream Estimated Peak Flows Estimated Peak Flow (cfs) Regression Equation Upper Lower Equation Variables Q 2 = (DRNAREA )(PRECIP ) 4,170 4,845 DRNAREA: Drainage Area Q 5 = 1.12 (DRNAREA )(PRECIP ) 7,261 8,941 Upper: 14.4 mi 2 Q 10 = 3.16 (DRNAREA )(PRECIP ) 9,758 12,337 Lower: 24.6 mi 2 Q 25 = 9.55 (DRNAREA )(PRECIP ) 13,396 17,385 PRECIP: Mean Annual Rainfall Q 50 = 19.1 (DRNAREA )(PRECIP ) 16,037 21,152 Upper:139 inches Q 100 = 36.3 (DRNAREA )(PRECIP ) 19,211 25,692 Lower: 119 inches Q 500 = 126 (DRNAREA )(PRECIP ) 26,600 36,

41 Figure 25: Island of Hawai i Hydrologic Regions Flow Duration A flow duration curve is used to illustrate the percentage of time that flows occurring in a stream or river are equaled or exceeded. Typically, the shape of the curve related to high flows can be used as an indicator of the type of floods the stream experiences. For small watersheds, a steep curve for high flows indicates rain-caused floods with no snow melt. Within the lower flows, a flat curve indicates that flows are sustained throughout the year due to natural or artificial stream regulation, or large groundwater contributions. Using the recorded flow data, the USGS estimated the flow durations for the Wailoa Stream. Figure 26, a flow duration curve, illustrates the hydrologic characteristics of the Waipi o Valley. Based on the presented data, the flow rate corresponding to the 1 percent exceedance frequency is 441 cfs. The 1% values would translate to having flows of 441 cfs or greater in the stream for approximately 3.7 days a year. As presented earlier, the BKF flow was estimated to be 500 cfs. So it can be expected that for the Waipi o Valley, flows contributing to the movement of sediment (BKF), happens less frequently. 4-22

42 Figure 26: Flow Duration Curve for the Wailoa Stream 4.5 HYDRAULIC MODELING The Wailoa Stream through the Waipi o Valley is a very high-energy system. During flood flows, the stream conveys large flows at high velocities, having the capacity to transport large quantities of sediment and bed material. To develop a better understanding of the energy associated with the river as well as floodwater elevations, a hydraulic model of the complex riverine environment found in the Waipi o Valley was created using the HEC-RAS modeling program developed by the USACE. HEC RAS is a one-dimensional hydraulic model used to estimate flow depths, velocity, and other parameters in a riverine environment. The USACE developed a geographic information system interface for the HEC-RAS program, HEC- GeoRAS, to create the channel geometry input files as well as map the model results. For the Waipi o Valley project, light detection and ranging (LiDAR) topographic data was interfaced with the HEC-GeoRAS program. Figure 27 shows the plan view of the project area, including survey data locations, cross-section delineation, and the topographic surface resulting from the LiDAR data set. As shown in Figure 27, the Wailoa Stream and the numerous auwai and flow splits created a complex riverine environment where flows split from (bifurcate) and return (confluence) throughout the valley. The largest flow split is the Kūnaka Channel represented in the figure as Split. An additional flow split was incorporated into the model at the Linda Beech Crossing to represent the current flow split condition at that location. The cross-section geometry used to represent the hydraulic character of the stream were developed using LiDAR data provided by the USACE and survey data collected by AECOM. For the Kūnaka Channel cross-section, data was taken from previous NRCS efforts associated with the development of the Management Plan (NRCS 2006). 4-23

43 January 2012 Figure 27: Waipi o Valley Hydraulic Model Layout The LiDAR data was used to represent the floodplain data across the valley floor, and the AECOM survey data was used to provide the additional detail related to the actual stream channel. Due to the dense vegetation within the valley, many LiDAR data elevation points were associated with the elevation of the vegetation canopy, not the ground level. As a result, the cross-section LiDAR data had to be edited to filter out the vegetation, prior to incorporating it into the model Downstream Boundary Condition HEC-RAS is a generally a step-backward model, meaning the water surface elevation calculations start at the downstream end of the model and then work upstream. In order to effectively model the 4-24

44 hydraulic characteristics of the Wailoa Stream, it is important to define a starting point, water surface elevation (WSE), that is representative. The downstream end of the model represents the location where the Wailoa Stream discharges into the ocean. To estimate a reasonable starting WSE related to tidal conditions, a tidal gage at Kawaihae, near the northern tip of the Island of Hawai i, was used. As the predicted tidal chart in Figure 28 illustrates, a typical tidal cycle includes: Higher High, High, Low, and Lower Low tides. Figure 28: Kawaihae Tide Prediction for Late May 2010 The data shown in Figure 28 above was generated by the National Oceanic and Atmospheric Administration (NOAA), based on recorded tide data from the recording gage at Hilo Harbor. NOAA also produced tidal data for the Kawaihae location based on the period of record of the Hilo data. The data results are shown in Table 9. Since HEC-RAS is a backwater model, the higher the starting water surface elevation is, the higher the upstream flood levels will be. To provide for a conservative result, the modeling efforts assumed a starting water surface elevation based on the mean higher high water (MHHW) value of 4.95 ft. Table 9: Tidal Elevations for Kawaihae Tide Elevation MLLW Datum Elevation NAVD88 MHHW Mean Higher High Water MHW Mean High Water MTL Mean Tide Level MLW Mean Low Water MLLW Mean Lower Low Water NAVD88 North American Vertical Datum of 1988 Combined with the peaks flows presented in Table 9 and the bank full flow of 500 cfs, the developed HEC-RAS model was used to assess the existing hydraulic characteristics at the Kawashima and Linda Beech project sites. The model was also used to investigate the impacts of the accumulated material at the mouth of the Wailoa Stream. As there are not records associated with flows and flood elevations in the stream, the HEC-RAS model was not calibrated. The Manning s roughness coefficient used in the model was based on published estimated values for natural streams (Chow 1959) and professional judgment. 4-25

45 4.5.2 Wailoa Stream Mouth Blockage Although not specifically called out as a project site, Stakeholder concerns regarding the sediment accumulation at the rivermouth causing increased flooding impacts in the lower valley, were investigated. Figure 29 illustrates how material transported by the Wailoa Stream is deposited where the river energy meets the ocean. As material accumulates at the rivermouth, the elevation of the material creates a backwater condition in the stream. Figure 29: Accumulated Material at Wailoa Stream Mouth Using the HEC-RAS model, the impacts of the accumulated material and the resulting backwater conditions were investigated. During the initial phases of the project, the AECOM team surveyed a cross-section that represented the highest point of the existing accumulated material. The surveyed cross-section was modeled in HEC-RAS as an in-line weir. This modeling approach allows for greater computation stability and simplifies the process of modeling the existing and proposed conditions. The resulting cross-section associated with the deposited material is shown in Figure 30. The gray area reflects the accumulated material when compared to the cross-section geometry of the cross-section upstream of the material. As part of the investigation on the impacts of the accumulated material on the modeled water surface elevation in the Wailoa Stream, the material shown to be impeding flow was revised to an elevation of 3 ft, removing almost the entire blockage caused by the accumulated material. The HEC-RAS modeling results for the lower reaches of Wailoa Stream are shown in Figure 31. As the water surface profile illustrates, the accumulated material affects the lower portion of the stream. The backwater impact from the accumulated material extends upstream to approximately where the 4-26

46 river heads west, away from the road (~Cross-section 960). For the scenarios shown, with existing conditions compared to cleared out conditions, the BKF WSE is lowered from 7.4 ft to 5.0 ft. For the shown 100-year flow, the WSE was reduced from 13.9 ft to 13.3 ft. Once the flow depth in the river reaches the top of the bank where the adjacent floodplains become inundated, the impact from the accumulated material is lessened as the flooding spreads across the valley floor HEC-RAS Modeling at Kawashima Waterhead The HEC-RAS model for the Kawashima Waterhead project site was used to estimate flow depths and velocities for a range of flow conditions. The model results provide design parameters for stable channel design and level of bank protection required for engineering potential alternatives to address bank erosion at the site. As Figure 32 illustrates, the cross-section near the current waterhead contains three channels. During high flows, the WSE is high enough that the individual channels act as one. During lower flows, the three channels can act as individual channels, each with a different water surface elevation and velocity. For the purpose of the HEC-RAS model, it was assumed the three channels would maintain the same WSE across all channels, as shown in the figure. What the modeling results show in Figure 32, is that the right channel (looking downstream) has the highest flow velocities. The higher velocities indicate the most efficient flow path for moving both water and sediment. The values presented in Table 10 illustrate how the hydraulic character of Wailoa Stream changes within the Kawashima project reach. Upstream of the auwai, the flow velocities for all modeled events are high, approximately 7 ft per second (fps) and greater. At the cross-section where there are three flow paths (the wider channel sections), the results are lower flow velocities for the BKF event, which would result in bed material being deposited. Downstream of the auwai, where the left bank levee is showing signs of erosion, the velocity results illustrate how the in-channel velocities increase quickly from the BKF to 2-year, and then as flows overtop the banks, the velocities (and stream energies) drop, resulting in deposition of material. At the cross-section downstream of the auwai, these flow characteristics have resulted in a gravel bar developing, which forces flows to the left bank, increasing the risk of erosion. 4-27

47 waipio Plan: LB1_EX_W eir 5/24/2011 River = Waipio Reach = Lower Reach RS = 4 IS This weir replaces cross section 4.01 Legend Ground 20 Ineff Bank Sta 15 Elevation (ft) Station (ft) Figure 30: Wailoa Stream Accumulated Material Modeled in HEC-RAS 4-28

48 January 2012 Legend WS 100Year - EX1 WS 100Year - dredge1 30 WS Est. Bank Full - EX1 WS Est. Bank Full - dredge1 Ground 20 Elevation (ft) Main Channel Distance (ft) Figure 31: Wailoa Stream Water Surface Profile 4-29

49 Figure 32: HEC-RAS Results at Kawashima Waterhead Site 4-30

50 Table 10: HEC-RAs Results for Kawashima Waterhead Project Reach WSE (ft) Velocity (fps) Near the Original Auwai Inlet BKF Year year year year Year Upstream of Current Manuwai BKF Year year year year Year Bank Erosion Downstream of Auwai BKF Year year year year Year HEC-RAS Modeling at Linda Beech Crossing For the Linda Beech project site, the HEC-RAS existing conditions modeling efforts were used to determine the flow velocities, flow depths, and the flow split between the Wailoa Stream and side channel. As the existing conditions results show, the reach upstream of the flow split currently provides adequate flow velocities to transport material through the cross-section. At the flow split, the velocities quickly drop as the channel size increases, allowing for deposition of the bed material and resulting in the active migrating channel that exists. Under existing conditions, the HEC-RAS results indicate that the right channel is currently capturing more than half of the total flow for the larger flow events. At lower flows, the left channel still maintains a higher amount of flow. As the flow depths at the Linda Beech project site increase, the flow spreads across the entire valley floor, forming a single channel, so the distribution of flow between the right and left channels is not discernable even though the model result indicates the split (Figure 33 and Table 11). 4-31

51 January 2012 Figure 33: HEC-RAS Results at Linda Beech Crossing Site 4-32

52 Table 11: HEC-RAS Results for Linda Beech Project Reach WSE (ft) Velocity (fps) Flow (cfs) Upstream of Crossing BKF Year , year , year , year , Year , at the Flow Split BKF /204 2-Year ,917/2, year ,31/5, year ,836/7, year ,979/9, Year ,370/10,

53 5.0 ALTERNATIVES ANALYSIS As defined, the goal of this preliminary investigation is to identify, develop, and assess measures to stabilize the stream and reduce potential damage caused by flooding events, maintaining the flow and function of the auwai currently serving the taro lo i adjacent to the river. Based on analysis of existing conditions regarding the watershed hydrology, the river hydraulics, and the geomorphology of the project reaches, the AECOM team developed and assessed three alternatives at the Kawashima and Linda Beech sites that meet the project goals. The alternatives presented below address transport of sediment and bedload through the main channel and downstream of the proposed repair areas. Both the Kawashima and Linda Beech sites have common elements present in all alternatives: 1) Redefine the Wailoa Stream with one channel rather than the multiple split channels that currently exist, and 2) Redefine the channel with a stable geometry. The variable elements of each alternative deal with the use of structures to help prevent erosion on outer meanders and, in the case of the Kawashima site, the type of auwai that should be implemented at the site. The variable elements at each site are intended to provide a greater level of repair and function in the channel, but with an added cost and difficulty of implementation. Thus, the following discussion is intended to compare the relative cost-benefit of each of the alternative design elements at both sites. 5.1 KAWASHIMA SITE Sediment Transport and Streambank Stabilization A consequence of the split of streamflow at the Kawashima site is the loss of stream energy, which reduces the river s ability to transport bedload through the main stem of the Wailoa Stream. The loss of stream power and critical shear stress at the BKF discharge has caused aggradation and the development of depositional bars within the channel. Moreover, the split in streamflow has caused flows to be directed against the left bank at the waterhead, causing bank erosion. To provide greater sediment transport capacity and competency through the Kawashima Waterhead area, it is important to have a channel geometry that accommodates bank full flows and the resulting ability to transport bed material. To accomplish this, the flow capacity of the river needs to be the estimated bank full flow of approximately 500 cfs, and the channel needs to have the geometry similar to that of a stable section of the river. For these purposes, a stable section is a cross-section that can carry the sediment load delivered from upstream, while neither aggrading nor degrading the stream. A stable cross-section was identified upstream of the split channel and is described in the previous discussion of existing conditions (Figure 34). The channel through the Kawashima Waterhead (Figure 35) should be redefined into a single channel with dimensions that mimic this stable geometry. The channel should be designed with the top of bank equal to the BKF elevation, and planted with native, perennial vegetation to stabilize the channel banks and provide increased floodplain roughness for above-bkf flows. The planform of the channel should be reconfigured to match existing values of radius of curvature, belt width and meander length found on more stable parts of the river. Finally, the profile of the reconfigured channel needs to be such that it mimics the natural pool-riffle sequence found upstream. This is important for both habitat and stream stability. Certain bedform features, such as pools, riffles and glides, provide critical habitat for fish and other aquatic organisms. From a stability perspective, the presence of a varied bedform with pools and riffles promotes distribution of energy, energy dissipation and bedload sorting within the channel. Table 12 contains the existing hydraulic conditions at the Kawashima site, as well as the defined stable reach of Wailoa Stream upstream of the Kawashima Waterhead. As the data shows, the current channel width at the waterhead is approximately double the width of the defined stable channel upstream of the waterhead. 5-1

54 Legend WS Alternative Q 0 ft/s 1 ft/s ft/s 3 ft/s 4 ft/s 5 ft/s Ground Ineff Bank Sta Elevation (ft) Figure 34: Stable Cross-section Upstream of Kawashima Waterhead Site Station (ft) 5-2

55 40 30 Legend WS Alternative Q 1.0 ft/s 1.5 ft/s 2.0 ft/s 2.5 ft/s 3.0 ft/s 3.5 ft/s 4.0 ft/s Ground Bank Sta 20 Elevation (ft) Figure 35: Existing Cross-section at Kawashima Waterhead Site Station (ft) 5-3

56 Table 12: HEC-RAS Hydraulic Parameter Results at Kawashima Waterhead Cross-section Flow Velocity (fps) Channel Width (ft) Stable (Cross-section 2091) Kawashima (Cross-section 1885) Streambank Erosion Protection The existing split channel is located along the outside bank of a meander in the river alignment. Immediately upstream of the waterhead on the left bank, the stream bank is experiencing erosion, resulting in near vertical banks and a deep thalweg along the toe of the bank. While flows typically are directed against meanders of rivers, instability in the bedform can accelerate and exacerbate bank erosion, such as where a mid-channel bar forms and increases the near bank stress against the outer meander. In the case of the Kawashima site, the aggradation in the channel has directed flows against the outer meander and increased the near bank stress against this bank. If left unaddressed, the continued erosion of the stream bank may adversely affect the auwai and any stabilization measures conducted on the main channel of the Wailoa Stream. Therefore, as part of the Kawashima Waterhead alternative development, it is proposed that the streambank be stabilized through some combination of laying back the banks to a stable angle and redirecting streamflow away from the outer meander with the use of rock vanes. Vanes correctly placed within an alluvial stream system are used to transfer the energy of the stream toward the center of the channel. The redirecting of stream energy (erosive velocities) away from the banks, moves the thalweg and the associated high shear stress towards the center of the channel, directing the flow to the low-energy point bar (inside meander). One of the benefits of using vanes, as compared with simply hardening the streambanks, is that the relocated stream energy stays within the local area and is not transferred upstream or downstream. 5.2 LINDA BEECH SITE Sediment Transport and Streambank Stabilization As with the Kawashima site, the main issue at the Linda Beech site is the splitting of stream flow, which has led to the development of channels that lack the necessary competency and capacity to carry the sediment delivered from upstream. As previously discussed, an upstream, stable section exhibits the necessary geometry to transport the sediment load, whereas the split channels downstream lack the same geometry. In order to remedy the issues at the Linda Beech site, the primary solution is to redirect flow into a single channel, using a channel plug to block flows from reentering the other split channel. The alternatives presented below vary in whether the flow is to be redirected into the active, left-hand channel, or into the inactive, relict channel to the west. In addition, to improve sediment transport competency and capacity in the channel in which flow is directed, it is recommended that the geometry of a stable, upstream section be replicated down the length of the new reach. However, this would involve the labor-intensive effort of reshaping the active channel. Thus, an alternative is presented where reshaping of the channel would not be performed. In addition to the stream stability issues at the Linda Beech site, any work at the site also needs to address the issues with the Linda Beech Road Crossing, which is a primary access route for residents to reach the west side of the valley. According to the Waipi o Valley Stream Management Plan, this ford sometimes becomes too deep for vehicular crossing during high flows, and the rocks that make up the ford are often washed downstream during high events (NRCS 2006). To remedy this problem, the channel should be widened in this area such that the mean depth of the crossing is decreased, while still maintaining BKF flow capacity. The channel competency will be decreased for a short distance due to the widening. However, this could allow the opportunity to use this area as a bedload trap, another possible management solution mentioned in the Waipi o Valley Stream Management Plan. 5-4

57 5.3 ALTERNATIVES DETERMINATION AND DESCRIPTION The alternatives developed for the and Streambank Stabilization are presented in Sections and below. Conceptual drawings for each of the alternatives are provided in Appendix B. Each of the alternatives incorporate similar design elements, with the cost and level of effort being the major difference. Table 13 contains the HEC- RAS results for the alternatives at the Linda Beech site, illustrating the dynamics of the anticipated flow splits. Table 13: Flow Split Evaluation at Linda Beech Crossing At the Flow Split Existing Condition (cfs) Post Condition (cfs) BKF Year 1,917 1, year 4,331 4, year 5,836 5, year 6,979 7, Year 8,370 8,597 The post condition results indicate that for BKF (500 cfs) and flows less than BKF, the majority of the flow stays within the Wailoa Stream. For larger flow events, the flow is spread across the entire valley; hence, the actual distribution of flow is not discernible Kawashima Waterhead Alternative 1 Alternative 1 involves realigning the existing, multi-thread channel into a single channel and building a new channel with a geometry that replicates the sediment transport characteristics of a stable cross-section. This will ensure that sediment efficiently moves through the channel in the future, in order to avoid a similar unstable situation as currently exists due to deposition of sediment. Figure 36 displays a typical, stable cross-section that could be implemented at the site, based on upstream stable geometry. This cross-section is 40 ft wide, has a maximum depth of 3.1 ft and a mean depth of approximately 2.2 ft. The side slopes of this cross-section are 3:1. To verify its stability, the proposed cross-section was compared in the POWERSED model with a cross-section upstream of the flow split that was observed to be relatively stable. As shown in Figure 37, the cross-section matches the discharge to unit-stream power relationship for flows up to BKF, meaning that it will transport the same amount of sediment over time as the upstream section, and therefore promote stream stability. Realigning the channel would involve both fill and cut, with an effort to balance the two, in order to avoid having to import any outside fill material, which would be impractical at this location. The existing gravel bar would be removed and used as backfill for areas to the right and left of the new channel. Areas of cut on the right bank would be used to fill areas on the left bank between the auwai and the new channel. As mentioned in the discussion of existing conditions, there is a relatively tight meander bend just upstream of the flow split that has a radius of curvature to BKF ratio indicative of high near bank stress. The realigned channel would be designed to increase the radius of curvature such that the stress on the left outer meander (currently eroding) would be decreased. The criteria for other planform variables on the realigned channel would be taken from other, more stable parts of the Wailoa Stream. 5-5

58 Figure 36: Typical Cross-section of Proposed Conceptual Cross-Section at Kawashima Waterhead Figure 37: Unit Stream Power versus Discharge Relationship of Upstream Stable Section Compared with Proposed Typical Section In addition to the realignment of the channel, the outer meander on the left bank upstream of the waterhead would be stabilized by building back the bank at lower slope and constructing the bank with soil layer lifts, gravel or toe wood and planting with native vegetation. A soil layer lift is a bioengineering technique that uses layers of soil wrapped in geotextile fabric, such as coir fiber matting, and planted with perennial vegetation. These wrapped layers provide increased resistance to shear stress in high-energy areas of a river such as outer meanders. An example of one type of soil layer lift is shown in Figure 38. Gravel could also be used to build back and stabilize this bank, as there is an abundance of this material deposited along the Kawashima Reach. The rock toe will provide additional protection against under-cutting of the new banks. As with the other techniques, vegetation would be planted on the rebuilt bank, and, as the vegetation matures, it will provide greatly increased stability. These bio-engineering techniques are by no means the full extent of what could be done to stabilize the bank on the Kawashima site. They could, however, be implemented with materials that are available in the Waipi o Valley, while minimizing the material that must be transported in. 5-6

59 Figure 38: Detail of Soil Layer Lifts Method of Streambank Stabilization (Source - VDEQ 2004) A final critical element of this alternative is the reconstruction of the existing auwai. The auwai would be rebuilt in its natural state, meaning it would follow the design of what currently exists. It would only be modified to account for the realignment of the Wailoa Stream. Further investigation and data would be needed prior to final design in order to complete the design of the natural auwai. A conceptual alignment drawing for the realigned channel is shown in Appendix B. Alternative 2 Alternative 2 follows the same design elements of Alternative 1, in that the channel would be realigned through the Kawashima site, the left bank outer meander would be stabilized with bioengineering solutions and the waterhead/ auwai would be reconfigured to account for the realignment of the river. However, in this alternative, a more sophisticated auwai design is proposed. Rather than a natural auwai in the form of a ditch, a pipe culvert would be placed at the waterhead and extend down the existing auwai, several hundred feet, before discharging into the existing auwai. The culvert would have a sediment trap installed near the inlet, which would need to be periodically maintained and cleaned out to ensure continual functioning of the system. The final design of this system would ensure that adequate flows are maintained in the auwai. The advantage of using a pipe culvert is that it allows for a predictable amount of flow to be maintained to the downstream taro lo i, while ensuring that the main channel does not have an opportunity to bypass its current alignment and create instability issues downstream. Alternative 3 Alternative 3 is an add-on to either Alternative 1 or Alternative 2 for upstream flow deflection using rock vanes. The purpose of these rock vanes is to provide added stability to the rebuilt outer meander on the left bank. The vanes would deflect flow towards the lower-energy inner meander (point bar side), and thus decrease the shear stress experienced on the rebuilt banks. In addition, 5-7

60 the vanes would provide stability while vegetation matures. An example of a J-Hook type of vane, taken from the NRCS National Engineering Handbook, Part 654, is shown in Figure 39 (NRCS 2007). At the Kawashima Waterhead, upstream of the existing flow split, a series of rock vanes would be constructed on the left bank outer meander of the river. The rock vanes would extend into the river channel about 1/3 of the total channel width, extend upstream from the BKF elevation at about a 5% to 7% slope, and would be angled from the bank with less than a 25 degree angle. The rocks used to construct the vanes could potentially be pulled from the existing depositional areas of the river, at the Kawashima Waterhead, or upstream or downstream of the site, where larger, boulder-class stones are present. The vanes are presented as an alternative element because they are not necessary to the stability of the outer meander, but would provide additional protection. They would also increase the cost and labor of the stabilization efforts at the Kawashima site. Moreover, construction of these rock vanes often requires a higher degree of contractor sophistication and experience Linda Beech Site Alternative 4 The first alternative at the Linda Beech site would involve diverting the flow, which is split into two channels, into only the left (westernmost) active channel, and rebuilding this channel with a geometry that replicates sediment transport characteristics of a stable cross-section upstream. As described above, a stable section has been identified that possesses the necessary competence and capacity to move the sediment load being delivered from upstream. The current left branch of the channel does not possess this competence and capacity, and thus, reshaping the channel to an efficient geometry would greatly increase its future stability, once all flow is concentrated into that channel. A conceptual, typical cross-section has been developed to illustrate the stable channel form that could be implemented along this left branch, and is shown in Figure 40. This cross-section was run in the POWERSED model to compare its sediment transport ability with that of the channel upstream. As shown in Figure 41, the cross-section possesses the same stream power at various stages of flow as upstream, indicating that it would be able to match the stable sediment capacity of the upstream channel. The cross-section has a width of 40 feet, a maximum depth of 2.5 ft and 3:1 side slopes. There is 2 ft to the toe of the side slopes, but it is recommended that an additional 0.5 ft be graded to define the thalweg of the channel. The total BKF area is approximately 81 ft 2. The material that is cut from the left channel would be used to backfill the right channel. To divert flow into the left channel, a channel plug would be installed in the right branch of the channel at the current split location. The purpose of the plug is to prevent the flow from cutting back into the right channel. The channel plug would be composed of a relatively impervious material and would extend a sufficient distance to prevent the flow from recutting into the old channel. Vegetation should be planted on the plug to provide increased stability. Once vegetation has matured, it should fully prevent the flow from reentering the right channel. 5-8

61 Figure 39: Typical Vane (J-Hook type) Configuration (Source - NRCS 2007) 5-9

62 Figure 40: Typical Cross-section for Implementation on Left Branch of Linda Beech Site Figure 41: Unit Stream Power versus Discharge Relationship of Upstream Stable Section Compared with Proposed Typical Section 5-10

63 To create a shallow ford (Figure 42) at the Linda Beech Crossing, the channel would be widened through the ford section in order to decrease the mean depth of the channel in that reach. This widening would be done on a riffle section of the existing left branch of the channel. Currently, the ford has a maximum depth of approximately 3.5 ft during BKF flow. If the typical section described above is widened from 40 ft to 60 ft, the maximum depth during BKF flow could be decreased to 2 ft, with an average depth of 1.6 ft, while still maintaining BKF flow. One consequence of this widening would be a decrease in channel competency within this reach. However, this could prove to be an added benefit, as the widened area could act as a bedload trap, and would help to prevent the stones used to stabilize the ford from washing dowstream. Large bedload particles deposited in this section, due to the drop in competency, could be periodically removed in order to increase the sediment transport efficiency of the channel downstream. To verify this approach, competency was calculated for the typical ford cross-section described above. The widening of the channel at the ford would decrease the competency such that only a 156-mm particle could be moved during BKF flows (approximately 0.5 ft). Thus, particles over this size would be deposited in this ford area and could be periodically removed. This calculation provides a good guideline for the size of the stone needed to stabilize the crossing. Finally, as an optional element of this alternative, rock vanes can be installed upstream of the flow split in order to provide increased stability, and to help direct flows away from the right channel. The vanes would need to contain rocks that are sized sufficiently to prevent mobilization downstream, meaning that they would need to be larger than the D100 of the channel. Alternative 5 Alternative 5 has the same elements as Alternative 4, except that in this alternative, the left channel into which flows would be directed would not be reshaped with an upstream stable geometry. Instead, the channel would be allowed to establish a stable channel form on its own over time. This approach is riskier than Alternative 4 because it directs river flow into a channel that does not possess adequate geometry to move sediment efficiently. However, this would be the simplest approach, in that a minimal amount of earthwork would be required. The right channel would remain in its current state beyond the channel plug, and would essentially become an ox-bow pond. As with Alternative 4, the ford would be stabilized by widening the channel in an existing riffle section of the river. The artificially-widened area would double as a ford and a bedload trap, and could be periodically maintained by removing bedload from the river. This may assist in stabilizing the channel bed by compensating for the lack of stable geometry. An optional element with this alternative is the use of rock vanes, sized and located in the same manner as described in Alternative 4. Alternative 6 Alternative 6 is similar to alternatives 4 and 5, except that in this alternative, the flow would be directed to the relict channel located to the west of the active channel. Analysis of historical aerial images for this site show that, up until recently, the Wailoa Stream flowed through this relict alignment. The advantage of diverting flow into the relict channel, versus the active left-hand channel, is that the relict channel is larger and already possesses a more appropriate geometry for the flow and sediment transport than the split channels. However, the original instability that caused the channel to avulse would still be present. Moreover, the relict channel is now filled with fine sediment. Thus, as with Alternative 5, the risk of instability may be too great in this alternative to make it the preferred alternative. Leading into the final design stage, further evaluation will be needed to determine the risk of future instability and any actions that could be taken to mitigate this risk. As with the previous two alternatives, a channel plug would need to be constructed to block flows from entering the currently active channel. 5-11

64 Figure 42: Example Detail of a Permanent Ford 5-12

65 5.4 COMPARISON OF ALTERNATIVES The primary goal of the Waipio Valley Flood Damage Reduction and Stream Stability project is to stabilize the stream and reduce damage caused by past flooding events. The key to meeting this goal is to select an approach that anticipates the river s energy, and is designed to withstand the forces of the Wailoa Stream during high flows. Also important is the ability to maintain the stream channel geometry that effectively transports sediment through the system, rather than allowing sediment to be deposited in the current reaches. In making the final recommendation for the preferred alternative at each site, several criteria were developed to provide a method of evaluation. For each of the criteria, a rating system was developed that attempts to apply a relative value, ranging from 1-3, with 3 being the greatest advantage. The alternative with the highest summation of values provides the greatest benefit for achieving the project intent. The developed alternatives presented in this section are all feasible as far as constructability, but they do differ in other aspects. The following are the criteria developed for evaluation and selection. Kawashima Waterhead Site Maintain Flow and Functionality of Waterhead and Auwai Although the primary focus of this project is stream stability, the existing functions of the Kawashima Waterhead must be maintained in order to ensure adequate irrigation of downstream taro patches. Alternative Description 1 The use of a natural auwai that will maintain functionality. This auwai will have a similar shape and function as the current auwai, however, it will be located further upstream where the current left branch of the channel flows. The drawback to this approach is that the auwai could potentially divert excessive flows from the main channel, thus potentially diminishing the ability of the main channel to carry sediment. 2 A more sophisticated auwai using a culvert with sediment trap. The advantage of this more detailed design is that flows can be more easily controlled. Only the amount needed for irrigation can be diverted, thus allowing maintenance of flows in the channel. 3 This alternative will have either of the above waterhead and auwai configuration. 2/3 Rating 2 3 Risk of Future Instability The instability of the existing channel, with its bar formation and aggradation, is a result of the channel s inability to proficiently carry its sediment load. This criterion assesses the potential of the proposed solution to create further instability. Since the only difference between Alternative 1 and 2 is the type of auwai used, they have been given the same rating. Alternative Description 1 The channel will maintain sediment transport through the reach. The eroding bank on the left outside meander will be stabilized with bio-engineering techniques, however, no in-channel protection such as vanes will be used, and thus the risk of continued instability is greater than if they were utilized. In addition, keeping the waterhead and auwai in its current state may create more diversion of flow from the main channel than is necessary, and may potentially undermine sediment transport capacity and competency, creating a risk of future instability. 2 The channel will maintain sediment transport through the reach. The erosional bank on the left outside meander will be stabilized with bio-engineering techniques, however no in-channel protection such as vanes will be used. 3 The channel will maintain sediment transport through the reach. The erosional bank on the left outside meander will be stabilized with bio-engineering techniques and rock vanes, ensuring greater stability of the bank as the vanes give permanent vegetation time to mature. Rating

66 Construction Cost The primary differences between the cost estimates for the alternatives lie in the type of auwai used, and whether or not rock vanes are used. Section 7.0 details the considerations used to develop the cost estimate and provides the estimated cost to construct each alternative. Alternative Description 1 This alternative requires an estimated 335 cubic yards (CY) of excavation and 604 CY of backfill to realign and shape the proposed channel. The stabilized vegetated streambank is the largest single line item in the cost estimate at $175,800 2 This alternative requires 335 CY of excavation along with 1,172 CY of backfill material to construct the structure required to block the existing breach channel. 3 This has the same cost as the two alternatives above with the addition of rock vanes. 2 Rating 3 2 Table 14 is a summary of the criteria ratings for each alternative. Table 14: Alternative Selection Evaluation for the Kawashima Waterhead Site Criteria Alternative 1 Alternative 2 Alternative 3 Maintain Flow and Functionality of Waterhead and Auwai 2 3 2/3 Risk of Future Instability Construction Cost Linda Beech Site Risk of Future Instability- This criterion assesses the potential of the proposed solution to create further instability. Alternative Description 4 By replicating the stable channel geometry from upstream, the channel will maintain sediment transport through the reach. A channel plug will ensure that the channel does not recut into the right channel. 5 The left channel will not be reshaped with stable geometry. Thus, the risk of future instability is greater. However, the use of the ford crossing as a bedload trap area may prevent excessive deposition and aggradation. 6 Flow will be directed back into the relict channel to the west. Although this channel will not be reshaped to ensure stable geometry, it was the original channel course at one point. Thus, it has similar flow and sediment transport characteristics as upstream. However, the original cause of instability in this channel would still be present and may need to be addressed. Rating Construction Cost The primary difference between the alternatives at this site is the amount of earthwork required to construct the alternative. Section 7.0 details the considerations used to develop the cost estimate and provides the estimated cost to construct each alternative. Alternative Description 4 Because of the filling of the side channel, the amount of fill required for this alternative is high at 2,000 CY. The amount of excavation would be 989 CY. 5 This alternative limits the impact of construction by focusing on the reach near the channel split. Excavation is limited to 370 CY and the required backfill is only 393 CY. 6 Excavation of the previous stream channel will require an estimated 2,200 CY to provide adequate conveyance through the reach. Backfill of 1,114 CY will be needed to limit flow into the side channel. Rating Table 15 provides a summary of the criteria ratings for each alternative. 5-14

67 Table 15: Alternative Selection Evaluation for the Linda Beech Site Criteria Alternative 4 Alternative 5 Alternative 6 Risk of Future Instability Construction Cost Wailoa Stream Mouth Maintaining the accumulation of rock at the Wailoa Stream mouth will lessen the inundation potential of high flow events along the lower reach of the Valley. Controlling the amount of material that accumulates currently is addressed by manually removing the rocks from the beach. Another method would be to capture larger rocks further up in the watershed, removing them from the system before they reach the beach. As part of the Linda Beech Crossing site alternative, the proposed ford would incorporate a widened section of stream immediately upstream. As the ford acts like a low dam, slowing flow velocities, the larger material would accumulate in the designated area upstream. As the material accumulates, a maintenance program would require periodic removal of the material. The rock material could be used to fill potholes in the roads on the Valley floor, or could be placed in the floodplain to add roughness features. During high flow events, the added roughness elements would reduce flow velocity across the floodplain, reducing the potential of the stream to develop new channels. 5.5 WORK ON OTHER AREAS OF WAILOA STREAM Besides the proposed alternatives presented above at the Kawashima and Linda Beech sites, there are other stretches of the Wailoa Stream that were observed to have stability issues and could benefit from stabilization, but which are beyond the analysis of this particular report. In particular, downstream of the Kawashima Waterhead, the channel is at times overly-wide and its width/depth ratio exceeds that of the stable form observed upstream. These areas, which occur intermittently along the channel, could be stabilized using the same processes as described at the Kawashima Waterhead. 5-15

68 6.0 PROJECT COSTS 6.1 CONSIDERATIONS Waipi o Valley is very isolated, and access to the site is restricted by a steep and narrow road. The proposed alternatives utilize onsite materials to the extent possible. The following sections discuss factors that will affect the cost of constructing the proposed alternatives. The final subsection provides a conceptual-level construction cost estimate for each alternative Site Access and Equipment Mobilization The proposed project site is located off Waipi o Valley Road, approximately 50 miles northwest of Hilo, Hawai i. Refer to Appendix B, Sheet 2 for proposed access routes to the project sites. Mobilization costs can be minimized by scheduling successive phases of work Material Availability Material availability in Waipi o Valley is grossly limited, mainly due to the difficulty in transporting material through the steep, narrow Waipi o Valley Road. Imported materials should be avoided whenever possible. For the same reason, ready-mix concrete is not available in Waipi o Valley. To the extent practical, earthwork quantities should be balanced throughout the project; that is, cut volumes should match fill volumes. Green waste should be chipped on site and offered to farmers as composting LARGE ROCK RIP-RAP Rip-rap should be obtained from local borrow sites within Waipi o Valley. Hauling the material in from outside sources is not a feasible option. Another possible option to obtain rip-rap material would be to widen the existing Waipi o Valley Road, and use the excavated rock on the project. Such a task would most likely need to occur under a separate project. However, if the two projects were coordinated, then the rip-rap issue would be resolved Construction Estimates Conceptual-level construction cost estimates for the proposed alternatives are provided below to assist with project planning and funding acquisition. Material quantities were estimated from the dimensions shown on the conceptual plans (Appendix B). Construction unit costs were based on cost data obtained from multiple sources, including local material suppliers, local contractors, recent construction bids from similar or nearby projects, and cost data reference manuals. The following sources contributed to the preliminary cost estimates: Royal Contracting (Contractor, Honolulu, Hawai i) Isemoto Contracting Co., Ltd. (Contractor, Hilo, Hawai i) Kaikor Construction (Contractor, Honolulu, Hawai i) Past Project Bid Results Kaumuali i Highway Emergency Slope Stabilization, Hawai i Department of Transportation, 2007 Past Project Bid Results Kilauea Stream Debris and Sediment Removal, Department of Land and Natural Resources, 2009 Past Project Bid Results Emergency Earthquake Rockfall Repairs at Various Locations on Hawai i Belt Road Route 19, Hawai i Department of Transportation, 2010 Naval Facilities Engineering Command Cost Data Book, Potential Cost Impacts Additional factors that have been considered in the cost estimates are as follows: 6-1

69 Limited availability of materials and heavy equipment Time and cost to mobilize heavy equipment Cost to develop and maintain access routes for use during construction, and cost for post construction restoration of these areas Potential need for biological and/or archeological monitoring services during construction Utilization of Best Management Practices (BMPs) during construction to prevent any environmental pollution from entering Wailoa Stream. These temporary measures could consist of silt fences, turbidity curtains, sand bags, and sedimentation ponds. Additional unknown natural risks, such as maintaining the vegetated bank for 90-days or until the vegetation is established. Unexpected flooding could wipe out the pre-established vegetation. A potential alternative is to use rip-rap to avoid plant establishment Estimated Costs for Design and Construction Conceptual-level cost estimates are presented in Table 16 through Table 21 for each engineering design alternative. The costs of the final remedial designs may vary from the conceptual-level estimates due to other factors including land acquisitions, community needs, environmental issues, aesthetics, and local politics. Table 16: Estimated Cost for Alternative No. 1 Item No. LS Item Mobilization/ De-mobilization (25% of all other items) Installation, Maintenance, Monitoring, and Removal of BMP Approximate Quantity Unit Unit Price Amount 1 LS $113, $113,000 1 LS $125, $125, Clearing and Grubbing 7,693 ft 2 $1.50 $11, Channel Excavation 335 CY $75.00 $25, Channel Backfill 604 CY $ $75, Vegetated Stabilization Streambank 1 LS $175, $175, Rock Rip-rap, In Place Complete 13 CY $ $7, Site Restoration 1 LS $30, $30,000 Sub-Total $563,765 Contingencies (@ 10%) $56,376 Total Construction Cost $620,141 Additional Costs Rounded $620,000 Engineering (7% of total construction cost) $43,400 Construction Engineering (15% of total construction cost) $93,000 lump sum Contract Administration (0.4 x 85% of construction engineering) $31,620 Total for Design and Construction $788,020 Rounded $790,

70 Table 17: Estimated Cost for Alternative No. 2 Item No. Item 1.0 Mobilization/ De-mobilization (25% of all other items) 2.0 Installation, Maintenance, Monitoring, and Removal of BMP Approximate Quantity Unit Unit Price Amount 1 LS $150, $150,000 1 LS $125, $125, Clearing and Grubbing 10,172 ft 2 $1.50 $15, Temporary Coffer Dams 1 LS $40, $40, Channel Excavation 335 CY $75.00 $25, Channel Backfill 1,172 CY $ $146, Vegetated Stabilization Streambank 1 LS $175, $175, Rock Rip-rap, In Place Complete 13 CY $ $7, Culvert 172 Lin. Ft. $ $17, Inlet/outlet headwall 2 Each $8, $16, Site Restoration 1 LS $30, $30,000 Sub-Total $748,683 Contingencies (@ 10%) $74,868 Total Construction Cost $823,551 Additional Costs Rounded $820,000 Engineering (7% of total construction cost) $57,400 Construction Engineering (15% of total construction cost) $123,000 Contract Administration (0.4 x 85% of construction engineering) $41,820 Total for Design and Construction $1,042,220 Rounded $1,040,000 Table 18: Estimated Cost for Alternative No. 3 Item No. Item Approximate Quantity Unit Unit Price Amount 1.0 Rock vanes or stream barbs 2 Each $10, $20,000 Sub-Total $20,000 Contingencies (@ 10%) $2,000 Total Construction Cost with Alt. No. 1 $642,000 Total Construction Cost with Alt. No. 2 $842,000 Additional Costs Engineering (7% of total construction cost) $58,940 Construction Engineering (15% of total construction cost) $126,300 Contract Administration (0.4 x 85% of construction engineering) $42,942 Total for Design and Construction with Alt No. 1 $870,000 Total for Design and Construction with Alt No. 2 $1,070,

71 Table 19: Estimated Cost for Alternative No. 4 Item No. Item 1.0 Mobilization/ De-mobilization (25% of all other items) 2.0 Installation, Maintenance, Monitoring, and Removal of BMP Approximate Quantity Unit Unit Price Amount 1 LS $213, $213,000 1 LS $125, $125, Clearing and Grubbing 24,737 ft 2 $1.50 $37, Channel Excavation 989 CY $75.00 $74, Channel Backfill 2,007 CY $ $250, Vegetated Stabilization Streambank 1 LS $316, $316, Site Restoration 1 LS $30, $30, Rock vanes or stream barbs 2 Each $10, $20,000 Sub-Total $1,066,956 Contingencies (@ 10%) $106,696 Total Construction Cost $1,173,651 Additional Costs Rounded $1,170,000 Engineering (7% of total construction cost) $81,900 Construction Engineering (15% of total construction cost) $175,500 Contract Administration (0.4 x 85% of construction engineering) $59,670 Total for Design and Construction $1,487,070 Rounded $1,490,

72 Table 20: Estimated Cost for Alternative No. 5 Item No. Item 1.0 Mobilization/ De-mobilization (25% of all other items) 2.0 Installation, Maintenance, Monitoring, and Removal of BMP Approximate Quantity Unit Unit Price Amount 1 LS $80, $80,000 1 LS $125, $125, Clearing and Grubbing 5,158 ft 2 $1.50 $7, Channel Excavation 371 CY $75.00 $27, Channel Backfill 393 CY $ $49, Vegetated Stabilization Streambank 1 LS $60, $60, Site Restoration 1 LS $30, $30, Rock vanes or stream barbs 2 Each $10, $20,000 Sub-Total $400,287 Contingencies (@ 10%) $40,029 Total Construction Cost $440,316 Additional Costs Rounded $440,000 Engineering (7% of total construction cost) $30,800 Construction Engineering (15% of total construction cost) $66,000 Contract Administration (0.4 x 85% of construction engineering) $22,440 Total for Design and Construction $559,240 Rounded $560,

73 Table 21: Estimated Cost for Alternative No. 6 Item No. Item 1.0 Mobilization/ De-mobilization (25% of all other items) 2.0 Installation, Maintenance, Monitoring, and Removal of BMP Approximate Quantity Unit Unit Price Amount 1 LS $258, $258,000 1 LS $125, $125, Clearing and Grubbing 34,799 ft 2 $1.50 $52, Channel Excavation 2,206 CY $50.00 $110, Channel Backfill 1,114 CY $ $111, Vegetated Stabilization Streambank 1 LS $584, $584, Site Restoration 1 LS $30, $30, Rock vanes or stream barbs 2 Each $10, $20,000 Sub-Total $1,291,299 Contingencies (@ 10%) $129,130 Total Construction Cost $1,420,428 Additional Costs Rounded $1,420,000 Engineering (7% of total construction cost) $99,400 Construction Engineering (15% of total construction cost) $213,000 Contract Administration (0.4 x 85% of construction engineering) $72,420 Total for Design and Construction $1,804,820 Rounded $1,800, ESTIMATED COSTS FOR PLANNING AND PERMITTING The estimated costs for processing permits that are anticipated for this project are presented below. See Section 1.0 for detailed discussion of each permit. National Environmental Policy Act (NEPA) compliant Environmental Assessment (EA) Average cost = $75,000-$100,000 Assumptions: An EA will suffice. If it is determined that an Environmental Impact Statement (EIS) is required, the cost would increase significantly depending on the resource impacted. Includes cost for conducting Section 7 Endangered Species Act consultation with the United States Fish and Wildlife Service (USFWS). Includes informal consultation only. Includes a biological resources reconnaissance survey. No special-status species are present. If such species are identified, additional surveys would be required. Includes Section 106 National Historic Preservation Act (NHPA) consultation with the Stare Historic Preservation Office. Includes preparation of an Archaeological Assessment and Cultural Impact Assessment. Does NOT include cost to conduct intrusive archaeological field surveys. 6-6

74 Includes cost for up to one public meeting. NPDES NOI-C Permit for Storm Water Associated with Construction Activities Average cost = $10,000-$12,000 Assumptions: Wailoa Stream is a Class 2 waterbody; therefore, it would be covered under the General Permit Does NOT include cost for development of the Site-Specific BMP Plan, which is required for permit application processing. An additional $5,000 would be required to prepare the Site-Specific BMP Plan. Information required for completion of the Site-Specific BMP Plan would be supplied by the client. NPDES NOI-G Permit for Construction Dewatering Average cost = $8,000-$10,000 Assumptions: Includes cost to collect one representative water sample and have it analyzed per State of Hawai i Department of Health (DOH) Clean Water Branch (CWB) rules. Does NOT include cost for development of a Site-Specific BMP Plan and Dewatering Plan, which are required for permit processing. An additional $5,000 would be required to prepare the Site-Specific BMP Plan. Information required for completion of the Site-Specific BMP Plan would be supplied by the client. The client or the construction contractor would be required to supply the Dewatering Plan for inclusion in the permit application packet. United States (U.S.) Army Corps of Engineers (USACE), Section 404 Permit Average cost = $12,000-$15,000 Assumptions: Consultation with the USACE will result in a determination that the proposed project qualifies for coverage under one or more Nationwide Permits. Includes the cost to prepare the Preconstruction Notification. If the jurisdictional determination identifies a requirement for an Individual Permit, the cost would increase to approximately $25,000-$35,000 depending on the level of public involvement required. 6-7

75 Water Quality Certification, Section 401 Average cost = $15,000-$20,000 Assumptions: Does NOT include cost for development of a Site-Specific BMP Plan and Mitigation/ Compensation Plan, which are required for permit processing. An additional $5,000 would be required to prepare the Site-Specific BMP Plan. An additional $5,000 would be required to prepare the Mitigation/Compensation Plan. Information required for completion of the Plans would be supplied by the client. Collection of water quality samples/data is NOT included. The monitoring requirements would be determined through the permitting process. Water Quality Monitoring (i.e., collecting water samples, analyzing water samples, weekly reporting) can average $5,000/week. Stream Channel Alteration Permit Average cost = $4,000-$6,

76 7.0 SELECTED ALTERNATIVES Following the submittal of the Interim Report to the MKSWCD, a review by the stakeholders was conducted. One of the purposes of the stakeholder review was to verify that the assumptions, that were the basis of the alternative development, coincided with the stakeholder knowledge of the Waipi o Valley and Wailoa Stream. A second purpose of the stakeholder review was not only to allow the stakeholders the opportunity to review the developed alternatives, but also to allow them to make a selection of the approach to move forward with for each of the two project sites. The stakeholder review resulted in the development of hybrid alternatives at both the Kawashima and Linda Beech sites. The selected designs took different elements from the alternatives and created final approaches that met the physical needs of addressing the stream s energy, and the ability of the valley residents to utilize their lands. Following are short descriptions of the Selected Designs, along with cost estimates (Table 22 Kawashima Site, Table 23 Linda Beech Site). Conceptual Plans are provided on sheet 11 and 12 in Appendix C. 7.1 KAWASHIMA WATERHEAD The selected design is based on Alternative 1, where the approach is to return the project area to historic conditions and stabilize the channel and auwai alignments. In addition to the Alternative 1 design elements, rock vanes will be installed upstream of the bend to protect against future stream bank erosion. New elements for the site are concrete pilings. The pilings are to be placed across the auwai and will serve to trap and redirect floating debris. The Kawashima Waterhead selected design will include stream bank protection downstream of the waterhead. Approximately 500-ft downstream of the auwai, the left bank is experiencing bank erosion. The selected design will also incorporate a combination of rock vanes and bank protection measures for this stream section. The intent of the rock vanes will be to direct erosive flows away from the left bank toward the center of the stream. Bank protection measures similar to the approach at the waterhead itself will also be used to repair existing erosion locations and provide additional bank protection along the stream reach. 7.2 LINDA BEECH CROSSING For the Linda Beech site, the stakeholder review resulted in a selected design based on Alternative 4. However, the selected design will eliminate the backfill of the right channel. The originally proposed backfill created a situation where a ford on the right channel would not be needed. Because the backfill is not being incorporated into the selected design, the creation of a new ford will be necessary. If the channel plug is extended downstream far enough, the ford could be created on top of it. Otherwise, a ford that is similar in design to the one proposed in the main channel can be used. 7.3 FINAL DESIGN The conceptual plans for the Selected Designs (Appendix C) are intended to support permitting and the initial phases of project implementation. As funding becomes available and the project moves towards actual construction, the Selected Designs will require additional effort to bring the plans to a construction-ready level. The final design and construction phase can take two directions: Complete, construction-ready plans and specifications, or a design-build approach Complete Plans and Specifications This is the standard project delivery method, in which the owner contracts with separate entities for the final design and for the construction work. First the design consultant would prepare final plans and specifications based on the preliminary recommendations presented in this report. The plans and specifications would clearly define the scope of the work to be performed so that a contractor could provide a bid to perform the work. The design consultant would remain impartial throughout the project construction phase and look out for the interests of the owner. 7-1

77 7.3.2 Design-Build Under this project delivery method, the design and construction services are contracted to a single entity, also known as a design build contractor. The benefits include minimized risks for the project owner, reduced delivery schedule by overlapping the design phase and construction phase, greater opportunity to design the project more efficiently, and reduced design fees and construction costs. Working in a natural environment, using natural materials and having on-site construction flexibility built into the design-build method, may expedite decisions required due to unforeseen challenges. This assumes on-site personnel are experienced in the types of elements being constructed. Table 22: Estimated Cost for Selected Design at Kawashima Waterhead Site Item No. Item 1.0 Mobilization/ De-mobilization (25% of all other items) 2.0 Installation, Maintenance, Monitoring, and Removal of BMP Approximate Quantity Unit Unit Price Amount 1 LS $150, $150,000 1 LS $125, $125, Clearing and Grubbing 7,693 ft 2 $1.50 $11, Channel Excavation 335 CY $75.00 $25, Channel Backfill 604 CY $ $75, Vegetated Stabilization Streambank 1 LS $175, $175, Rock Rip-rap, In Place Complete 13 CY $ $7, Site Restoration 1 LS $30, $30, Concrete Piles for Trash Rack 4 Each $20, $80, Rock vanes or stream barbs 7 Each $10, $70,000 Sub-Total $750,765 Contingencies (@ 10%) $75,076 Total Construction Cost $825,841 Additional Costs Rounded $830,000 Engineering (7% of total construction cost) $58,100 Construction Engineering (15% of total construction cost) $124,500 Contract Administration (0.4 x 85% of construction engineering) $42,330 Total for Design and Construction $1,054,930 Rounded $1,050,

78 Table 23: Estimated Cost for Selected Design at Linda Beech Site Item No. Item 1.0 Mobilization/ De-mobilization (25% of all other items) 2.0 Installation, Maintenance, Monitoring, and Removal of BMP Approximate Quantity Unit Unit Price Amount 1 LS $158, $158,000 1 LS $125, $125, Clearing and Grubbing 9,327 ft 2 $1.50 $13, Channel Excavation 989 CY $75.00 $74, Channel Backfill (for channel plug only) 295 CY $ $36, Construct Ford Crossing 1 LS $15, $15, Vegetated Stabilization Streambank 1 LS $316, $316, Site Restoration 1 LS $30, $30, Rock vanes or stream barbs 2 Each $10, $20,000 Sub-Total $789,841 Contingencies (@ 10%) $78,984 Total Construction Cost $868,825 Additional Costs Rounded $870,000 Engineering (7% of total construction cost) $60,900 Construction Engineering (15% of total construction cost) $130,500 Contract Administration (0.4 x 85% of construction engineering) $44,370 Total for Design and Construction $1,105,770 Rounded $1,110,

79 8.0 PERMITTING REQUIREMENTS While developing and assessing alternatives to meet the project goals is challenging, getting a project ready for construction also requires meeting the regulatory requirements through preparation and submittal of all required permits. The following section provides an overview for the anticipated permits required for construction of the and Stream Stabilization Project. 8.1 NEPA REQUIREMENTS The purpose of the NEPA as implemented by the Council on Environmental Quality Regulations (40 Code of Federal Regulations Parts [1997]) is to ensure that adequate analysis of potential environmental impacts of proposed Federal actions projects and public disclosure of how this information is used in decision making. EAs and Environmental Impact Statements (EIS) are the documents prepared in order to assist in disclosure and decision making. The State of Hawai i has enacted a parallel system for the documentation and disclosure of environmental impacts (known as Hawaii Revised Statutes [HRS] Chapter 343 ), however, if this project uses federal funding, and falls within a National Wildlife Refuge, a NEPA-compliant (Federal) document would need to be prepared. An EA is a document that is prepared to determine whether the various alternatives considered for the project will have any significant adverse impacts to the environment. Various studies are commissioned (biological, archaeological, etc). The public and various agencies are consulted through a public review process. An EA ends in one of three ways: 1) Finding of No Significant Impact (FONSI), 2) commitments to mitigation for impacts accompanied by a FONSI, or 3) a requirement to prepare an EIS. The EIS document is much more robust, and includes an in-depth analysis of the various alternatives, and fully discloses the impacts (short-term, long -term, and cumulative) for each of the alternatives. The end result, after public and agency input, is a Record of Decision, indicating what alternative is chosen. An agency may elect to proceed directly with an EIS if significant adverse impacts are anticipated with the implementation of the proposed action. The preparation of an EA, including associated studies requires months, whereas the minimum time to prepare an EIS is 18 months NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) PERMIT FOR STORM WATER ASSOCIATED WITH CONSTRUCTION ACTIVITIES What is it? The purpose of the NPDES permit is to control water pollution by regulating point sources that discharge pollutants into waters of the United States. The NPDES permit is authorized under the CWA, and reviewed and approved by the DOH CWB. This particular permit pertains to the water that leaves a construction site as a result of rainfall ( stormwater ). There are two classes of permits: General and Individual. The General Permit is intended for routine projects in areas where there are no sensitive water resources. The Individual Permit is for construction projects that discharge to Class 1 or Class AA waters. When is it required? When a project disturbs greater than one acre of land, an NPDES stormwater permit is required. Whether the waterbody ultimately receiving the stormwater runoff is Class 1 or 2 (freshwater), Class A or AA (marine), or is otherwise protected (i.e., reserve) determines if an Individual Permit or General Permit applies. 8-1

80 What is the process? Once a determination has been made regarding the classification of the receiving water, if the project qualifies for General Permit coverage, a Notice of Intent (NOI) General Form and Site-Specific Construction Best Management Practices (SSCBMP) Plan must be completed and filed with CWB along with a $500 permit application filing fee. A Signatory and Certification Statement is also prepared and submitted. The SSCBMP Plan involves quantifying the amount of stormwater discharge that the project will produce and defining its path through the project site and into the receiving waters. SSCBMPs must be thoroughly defined to ensure that receiving waters of the United States are not adversely impacted. After a completed permit application is submitted to DOH, a response is usually given within days. If an expedited turnaround is needed, a telephone call to CWB to inform them of the situation early in the planning process usually results in CWB conducting a quicker review. Submitting a SSCBMP Plan with the initial submission is now required to expedite the processing of the application. The process is similar if the project requires an Individual Permit. A Signatory and Certification Statement and Individual Application Form must be submitted along with a $1,000 filing fee. The review and approval period, however, is extended, lasting as long as 4 6 months. Part of the processing requires a 30-day public notice and comment period (publication of notices in the newspaper are an additional $1,400 at the applicants expense). A public hearing may be required. Note 1. If an Individual Permit is required, both the discharge associated with Stormwater Associated with Construction Activities (discussed in this section), as well as discharges of Construction Activity Dewatering Effluent (discussed next) can be addressed/combined in the same application for coverage under a single Individual Permit. Separate applications are only required for General Permit coverage. Note 2. If a series of related projects a) will be executed (and completed) within a 5 year period, b) have plans ready for concurrent submission in the application packet, and c) any one of them requires an Individual Permit; it would be advisable to apply for an Individual Permit that covers all the actions as a time and cost saving measure. Where are the forms? Form C = NPDES GENERAL PERMIT FOR CONSTRUCTION ACTIVITY DEWATERING EFFLUENT What is it? The purpose of the NPDES permit is to control water pollution by regulating point sources that discharge pollutants into waters of the United States. The NPDES permit is authorized under the CWA, and reviewed and approved by the DOH CWB. The Construction Activity Dewatering Effluent permit pertains to water removed from the construction site and then returned to the waterbody (stream, river, lake, etc.). Similar to that discussed previously, there are two classes of permits: General and Individual. The General Permit is intended for routine projects in areas where there are no sensitive water resources. When is it required? When a project requires returning construction site water to a waterbody (stream, etc), an NPDES dewatering permit is required. Whether the waterbody ultimately receiving the stormwater runoff is 8-2

81 Class 1 or 2 (freshwater), Class A or AA (marine), or is otherwise protected (i.e. reserve) determines if an Individual Permit or General Permit applies. What is the process? Once a determination has been made regarding the classification of the receiving water, if the project qualifies for dewatering General Permit coverage, a NOI General Form and NOI Form G (NOI-G) form for dewatering effluent associated with construction activities must be completed and filed with CWB along with a $500 permit application filing fee. The NOI-G involves disclosing the dewatering discharge information, and testing for water quality parameters. Water quality data representative of existing conditions must be submitted with the application. If none is available, a water sample must be collected and analyzed by a qualified laboratory. After a completed permit is submitted to DOH, a response is usually given within days. If a quicker turnaround is needed, a telephone call to CWB to inform them of the situation early in the planning process usually results in CWB conducting a quicker review. Submitting a site-specific SSCBMP plan with the initial submission is encouraged and will also expedite the processing of the application. As mentioned above regarding the stormwater NPDES Permit, the process is similar if the project requires an Individual Permit. See the notes in the previous section, as they apply in this instance as well. Where are the forms? DEPARTMENT OF THE ARMY PERMIT What is it? The purpose of a Department of the Army (DA) permit is to determine a project s probable impact on the public interest and to identify possible environmental consequences. Under the CWA and Rivers and Harbors Act, the USACE regulates activities in waters of the United States, which generally includes coastal and inland waters, as well as rivers and streams feeding these water bodies. In the case of rivers, the horizontal extent (width) of the USACE s jurisdiction extends to the ordinary high water mark. Jurisdiction is also extended to wetlands adjacent to any of these water bodies. In the State of Hawai i, given the proximity of the ocean, rivers and nearly all streams (intermittent and perennial) come under the jurisdiction of the USACE. Further, it is possible that a Wetland Delineation will be required prior to the commencement of any construction activities if the project area is within a wetland. When is it required? Any project that places materials into the waters of the United States (temporarily or permanently) requires both a DA Permit and more than likely a Section 401 Water Quality Certification (WQC) (discussed below). If projects are limited in size, routine maintenance, emergency repairs, etc., a less rigorous review of the application is possible by following the jurisdictional determination (JD) process. What is the process? The USACE has a Nationwide Permit (NWP) Program to streamline the evaluation and approval process throughout the nation for certain types of activities that have only minimal impacts to the 8-3

82 aquatic environment such as routine maintenance. The first step in obtaining a DA permit is to obtain a JD from the USACE. If you feel your project could fall under a NWP, your JD should present that and request concurrence from the USACE. If the USACE determines that a NWP would be allowable, the permit process is very straight forward. Permitting may begin after the Corps claims jurisdiction over the proposed water body. The DA permit involves describing the dredged and/or fill material to be discharged, describing the structures to be constructed, and identifying environmental effects, alternatives, and mitigation measures. After the permit is submitted a public notice is issued and a 30-day comment period begins. A public hearing may be required. A completed application must be submitted to the Corps at least 45-days prior to breaking ground at the project site. For activities relating to farming, ranching, and or silviculture, certain activities are exempt and will not require a DA authorization under Section 404 of the CWA (33 Code of Federal Regulations 323.4). However, to qualify for this exemption, the activities must be part of an established (i.e., ongoing farming, silviculture, or ranching operation). The work for this project may not qualify for an exemption. Where are the forms? WATER QUALITY CERTIFICATION, SECTION 401 What is it? A WQC ensures that state water quality standards are upheld, and further sources of pollution are not created throughout a project. If the Corps takes jurisdiction over the proposed project, Section 401 of the CWA may also apply. A WQC is obtained from the CWB. A SSCBMP Plan and a Mitigation/ Compensation Plan must be thoroughly defined to ensure that receiving waters of the United States are not adversely impacted. When is it required? Any project that places materials into the waters of the United States (temporarily or permanently) requires both a DA Permit and more than likely a Section 401 WQC. Only minor maintenance activities are exempted from the 401 WQC process. What is the process? The completed permit application and $1,000 filing fee are submitted to the DOH CWB. A SSCBMP Plan and possibly a Mitigation/Compensation Plan must be thoroughly defined to ensure that the subject waters are not adversely impacted. After the permit application is complete, a public notice is issued in a local newspaper (at the expense of the applicant) and a 30-day comment period begins. A public hearing may be required. The WQC process can take up to 12 months to complete depending on the complexity of the project. CWB is now more closely reviewing and commenting on recent WQC submittals. Where are the forms? gov/health/environmental/water/cleanwater/forms/pdf/cwb-wqc.pdf 8.6 STREAM CHANNEL ALTERATION PERMIT What is it? A Stream Channel Alteration Permit (SCAP) is issued in order to protect, enhance, and reestablish, where practical, beneficial instream uses of water including the creation of a permit system to regulate the alteration of stream channels. 8-4

83 What is the process? The Hawai i Department of Land and Natural Resources (DLNR) Commission on Water Resource Management (CWRM) will determine if a SCAP is required for the proposed project and will administers the permit. A $25 filing fee must be submitted with the completed application. After CWRM approves the SCAP, they will publish a public notice and solicit comments. The total time frame is approximately 180 days. Where are the forms? CONSERVATION DISTRICT USE PERMIT What is it? The State of Hawai i has designated various lands (both public and private) throughout the Islands as set aside for Conservation District Use. Within the Conservation District, areas are divided into subzones that are afforded escalating levels of protection (General, Resource, Limited, Protected, and Special). Only certain activities are permitted within the Conservation District, and the list becomes progressively restrictive depending on the subzone. When is it required? A project is required to submit a Conservation District Use Permit (CDUP) when any Conservation District land is used that is not permitted by the State Land Use Law. All ocean water and submerged lands in Hawai i are part of the Conservation District. What is the process? The DLNR Office of Conservation and Coastal Lands (OCCL) is the accepting authority for the CDUP permit. To confirm that a CDUP is necessary, the project proponent must submit a Request for Information to OCCL. OCCL will respond within 30 days with a determination if a permit is necessary. A CDUP can take up to six months for processing and can require up to $1,000 in filing fees depending on the size of the project. Where are the forms? ENDANGERED SPECIES ACT SECTION 7 CONSULTATION What is it? The Endangered Species Act, Section 7, requires consultation with the National Marine Fisheries Service (NMFS) or USFWS when an action may affect listed species, or surrounding endangered species habitat. When is it required? Any project that requires a federal permit, occurs on public lands, and/or publicly funded must proceed with a Section 7 consultation. In certain instances even privately funded activities or on private land must conduct a consultation. 8-5

84 What is the process? A biological assessment must be prepared to disclose the projects potential effects on listed species and their surrounding habitat. After the biological assessment is submitted, NMFS or USFWS will respond with a biological opinion that may include a number of project alternatives. This process is frequently initiated through the DA permit application process, depending on the size of the project. 8.9 NATIONAL HISTORIC PRESERVATION ACT SECTION 106 CONSULTATION What is it? National Historic Preservation Act (NHPA) Section 106 requires consultation with the State Historic Preservation Division (SHPD) when a proposed project may affect historic properties included on the National Register of Historic Places, properties located on tribal lands, or when a Native Hawaiian organization places religious or cultural significance to a property. When is it required? Consultation is required when a proposed project may affect historic properties, which generally include structures greater than 50 years old, properties located on tribal lands, or when a Native Hawaiian organization places religious or cultural significance to a property. What is the process? A letter to SHPD must be prepared explaining the proposed project and its possible effects on the above stated items. SHPD will respond with a letter that may include a number of alternatives and suggestions. 8-6

85 9.0 PROJECT IMPLEMENTATION AND FUNDING OPPORTUNITIES A search for potential funding programs and sources for implementation of any proposed improvements was conducted. The search considered the multiple land parcels with different owners and lessees, multiple project purposes, and governmental programs. Potential funding opportunities are described below, categorized by government level or as Non- Governmental Organization. Eligibility of the funds to be used for planning, design, and installation is also discussed. 9.1 FEDERAL U.S. Department of Agriculture Natural Resources Conservation Service The NRCS administers programs created by two federal acts that can provide technical and financial assistance. However, appropriations for NRCS programs have been impacted in recent years by the federal budget crisis and may not be a good source for timely and adequate funding for the Waipio projects WATERSHED AND FLOOD PREVENTION ACT, PUBLIC LAW Much of the earlier work conducted by NRCS in the period 1995 to 2006 was carried out under LHD Watershed project. The Watershed Programs provide assistance to communities by evaluating the water resources problems and opportunities in a watershed-scale or regional-scale evaluation. The Waipi o projects will be evaluated as a component of the larger LHD Watershed or as a part of a new Waipi o or North Hawai i Watershed. Eligible purposes include agricultural water management, water quality improvement, flood control, and watershed restoration. The Watershed Surveys and Planning (WSP) Program can fund technical studies, development of project plans, and preparation of EAs or EISs for authorized water resources projects. Generally, up to 100% of the study and planning costs can be provided through the WSP Program. The local sponsors will be responsible for funding nonfederal requirements, such as unique aspects of the state EIS process. The request for study or planning authorization is submitted by the sponsoring local organization to the NRCS Director for the Pacific Islands Area. WSP Program funds can be used for plan and EIS preparation. Funding for the WSP Program has not been appropriated by Congress since However, the WSP Program remains authorized and eligible for Congressional fund appropriation. The Watershed Operations (WO) Program can fund installation of completed Watershed Plans and, potentially, other complying water resources projects. Generally, the WO Program will fund between 50% and 100% of the design, construction, and engineering costs of structures, depending on the project purpose, and the local sponsor will be responsible for the remainder of design, construction, and engineering costs. In addition, the local sponsors are responsible for acquisition of land rights, permits and approvals, and operation, maintenance, and replacement for the life of the project. The request for authorization of a project is submitted by the sponsoring local organization to the NRCS Director for the Pacific Islands Area. WO Program funds can be used for design and construction of the alternatives. Funding for the WO Program has declined sharply in the past decade with an authorized project backlog of approximately $1 billion in the nation. The WO Program remains authorized and eligible for Congressional fund appropriation

86 The Emergency Watershed Protection (EWP) Program is a disaster recovery program, which authorizes NRCS to immediately assist with and provide funding for situations involving threats to life and property caused by natural disasters. Waipi o has received assistance through the EWP program following storms in 1979, 1986, 2002, and While an emergency declaration is not necessary for the application, a singular, identifiable natural disaster event is needed to trigger the application process. Applications for assistance need to be submitted within 60 days of the event. NRCS can reimburse up to 75% of the project costs and up to 90% in certain limited-resource situations. EWP funds can be used to design and install alternatives to restore the area to predisaster conditions. EWP funds cannot be used for alternatives that modify or improve the stream from the predisaster configuration. Contact with State or County Civil Defense or any NRCS Office can start the assistance process following a disaster event FARM BILL CONSERVATION PROGRAMS The 2008 Farm Bill provides NRCS with authority and funding for several programs that may be applied to portions of the Waipi o projects. These programs are delivered to individual agricultural producers and landowners and managers. The Environmental Quality Incentives Program (EQIP) provides technical and financial assistance to agricultural producers to reduce erosion, improve air and water quality, and improve natural habitat for at-risk wildlife. The EQIP program will likely be limited to the privately-leased parcels of the Waipi o project area. Assistance through EQIP can be requested by the landowner or manager from the NRCS Waimea Field Office. The EQIP program cannot be used to plan or install the entire alternatives to provide stream stability. However, they can be used to adjunct the alternatives to provide wildlife habitat or conservation treatment of neighboring farmland. The USDA and Congressional staffers are currently working on program rules for the next Farm Bill, likely in There is much speculation about where the requisite budget cuts will fall in the new Farm Bill. The conservation titles of the Farm Bill may be heavily affected. The Wildlife Habitat Incentives Program (WHIP) provides technical and financial assistance to land owners for improvement of habitat for nationally and locally important wildlife species. While the land does not have to be in agricultural production, the land must be privately owned. Improvements can include wetland creation and enhancement for native waterfowl habitat. Assistance through WHIP can be requested by the landowner or manager at the NRCS Waimea Field Office. As with the EQIP program, the WHIP program can be used to enhance wildlife habitat and aquatic ecosystems in the project areas of the alternatives. Other Farm Bill Programs may apply to the Waipi o Project area. Contact the NRCS Waimea Field Office for further information about Farm Bill Programs U.S. Fish and Wildlife Service The USFWS Fisheries and Habitat Conservation Division administers programs and participates in partnerships that may assist with implementation of repairs to the breach. Purposes for the involvement of the Division will include protection and improvement of habitat for native stream organisms, such as the four species of o opu. The USFWS offers a financial assistance program through the National Fish Habitat Action Plan. The maximum grant is $250,000. Application for the grant should be made through the Hawai i Fish Habitat Partnership. The National Fish Habitat Action 9-2

87 Plan can provide financial assistance to parts of the alternatives to ensure aquatic habitat and migratory passages are maintained. mid= U.S. Army Corps of Engineers The USACE administers programs to assist communities with water resources problems. The Planning Assistance to the States (PAS) Program can provide USACE technical assistance to prepare a planning-level analysis and documents. Federal funding is limited to $500,000 annually, although most projects receive considerably less in funding, and must be cost-shared at a 50% federal-local ratio. This program would be valuable if the current stream repair projects are expanded to include other stream and subwatershed areas in Waipi o. The PAS program can fund preliminary studies of Waipio streams and problem areas. The USACE provides water resources project implementation assistance through the Continuing Authorities Program. The Program is a collection of water resource project authorities provided in various congressional acts. The CAP is intended to implement smaller projects that do not have to be authorized by Congress. The program can be used for streambank modifications and improvements and ecosystem restoration. The process for project implementation will require Congressional authorization of the project and appropriation of funds. The CAP can provide funds for planning, design, and construction of the alternatives. USACE assistance can be requested from the Civil and Public Works Branch located at Fort Shafter, Hawai i U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is charged with oversight and coordination responsibilities to ensure protection and restoration of the nation s environmental resources. Region 9 serves Arizona, California, Nevada, Hawai i and the U.S.-affiliated Pacific Islands. The EPA offers an array of watershed and water quality funding programs The most well-known of the programs is the CWA Section 319 program which is administered by the DOH. Other EPA funding programs that may be considered in Waipi o include the Targeted Watershed Grants, Wetlands Programs, National Estuary Program, and Regional Grants. The Section 319 Program will not be able to fund the installation of the alternatives due to their main purposes of bank stabilization and flood protection rather than water quality improvement. Associated projects, such as vegetation and filter strips on upstream and downstream streambanks, may qualify for Section 319 program funding. The EPA administers the CWA State Revolving Loan Fund. Loan funds can be used to finance construction projects for water conservation, and watershed and estuary protection. Elements of the Waipio project may be able to qualify for these loan programs National Oceanic and Atmospheric Administration The NOAA, an agency of the Department of Commerce, is a key federal player in the conservation and management of coastal resources. The mission of the NOAA Coastal Services Center (CSC) is 9-3

88 to support the environmental, social, and economic well being of the coast by linking people, information, and technology. The NOAA Pacific Services Center administers the Coastal Resilience Networks (CRest) Program which helps communities to become more resilient to coastal threats which include storms, flooding, sea level rise, and climate change. Applicants can request between $100,000 and $350,000 per year for a single project. The CRest program can fund planning and implementation of the alternatives, however, within the $350,000 per year limitation. Contact the NOAA Pacific Services Center for more information regarding the CRest Program. [email protected] Hawai i Congressional Delegation Hawai i s Congressional delegation has taken a strong interest in solving the water resources problems that exist in the state. Special Appropriation Acts are often passed by Congress to direct agencies to provide financial or technical assistance to a project without being a part of an established program. In this way, they are able to direct federal technical and financial resources to assist local governments and organizations. Contacts with Senator Daniel Inouye, Senator Daniel Akaka, and Representative Mazie Hirono (2nd Congressional District) should be made whenever major program requests are made to federal agencies STATE OF HAWAI I Department of Health The DOH s CWB administers the federal CWA, Section 319(h) grants program. Grants are provided to local governments and other organizations to prevent and/or reduce nonpoint source pollution to improve water quality of receiving water bodies. A wide range of activities can be funded by the 319 grant, including management or improvements to reduce nutrient or sediment runoff, control of invasive alien species and restoration of native vegetation in critical areas of the watershed, and modification of watershed improvements to include nonpoint source pollution controls. The 319 grant may require prior preparation of a EPA-approved watershed plan or prior establishment of water quality baselines. The Section 319 Program will not be able to fund the installation of the alternatives due to their main purposes of bank stabilization and flood protection rather than water quality improvement. Associated projects, such as vegetation and filter strips on upstream and downstream streambanks, may qualify for Section 319 program funding. prc/index.html Department of Land and Natural Resources The DLNR administers many state and federal programs to assist landowners and land managers with land management issues. A listing of the programs is found on the Division of Forestry and Wildlife website, which also includes a link to a detailed listing for federal and state incentives programs for land management on private lands

89 9.2.3 Coastal Zone Management Program The Hawai i Coastal Zone Management (CZM) Program is located in the Department of Business, Economic Development and Tourism s (DBEDT) Office of Planning. While the CZM Program does not directly administer funding assistance programs, the CZM program engages in partnerships for protection and enhancement of coastal and watershed resources. These partnerships are important sources of legislative funding requests. The State CZM program also serves as the pathway to NOAA technical and financial resources made available through the federal CZM Act. Grants for projects related to water quality improvement and stormwater management have been available nationally through the CZM program Department of Agriculture The Hawai i Department of Agriculture (DOA) is involved in many aspects of taro production and marketing in Waipi o. However, the DOA is not involved in the irrigation water supply to the farms. The DOA s Agricultural Resources Management Division (ARMD) manages and operates the State s ten agricultural parks and five Irrigation water systems throughout the state. The LHD, which uses the streams at the back of Waipi o Valley is managed by the DOA ARMD. The ARMD receives legislative appropriations for capital improvements and emergency repairs for its land and water facilities. The ARMD can be the local sponsoring organization for a federal program, such as the NRCS Watershed programs Mauna Kea Soil and Water Conservation District The MKSWCD, is a quasi-governmental sub-unit of the State of Hawai i, authorized by Chapter 180 of the HRS. The MKSWCD is one of six Districts on the Big Island and has responsibility for north and northcentral land areas on the Big Island. The Soil and Water Conservation Districts are supervised by a volunteer Board of Directors. The mission of the MKSWCD is to assist landowners and users to preserve and protect soil and water resources. It does so through programs promoting application of best management practices on individual properties and through partnerships in projects involving larger areas with multiple landowners and land users. The MKSWCD has managed and administered contracts and funds for many large area projects including the Pelekane Bay Watershed and the Wai ula ula Watershed. Requests for assistance from the MKSWCD can be made directly to the Board of Directors State Legislature Many capital improvement and significant repair projects on state-owned land will require a separate line item appropriation by the Legislature. The operating and capital improvement budget requests are submitted by the departments at the beginning of the legislative session. If the improvement is included in the department budget request, contact with State Representatives and Senators who are in a position to advocate or vote upon the request is important. As the rules for legislative action and the committee structure are often complicated, guidance from the requesting department and community lobbying organizations should be sought. (link to Legislative directory) 9-5

90 9.3 COUNTY OF HAWAI I The County of Hawai i has been supportive of efforts by the Waipi o community to improve infrastructure and recover from damaging storms. The County has consistently sent representatives to community meetings. The County may have interest in water quality effects of the projects in Waipi o Valley and might partner with associated projects for water quality improvement. Contact with the Mayor, key County Council members, and Director and leadership staff at the Department of Public Works (DPW) and Planning Department can be made to inform them of the project and to enhance partnership relations. County DPW projects have included extensive road and stream modification and improvement projects around Hawaii Island. Planning and installation of the alternatives can be conducted by the County DPW with authorization and funding provided by the County Council. 9.4 NON GOVERNMENTAL ORGANIZATIONS Big Island Resource Conservation and Development The Big Island Resource Conservation and Development (BIRC&D) an independent, nonprofit, nonpartisan, community-based organization focused on the prudent use of natural and human resources on the Island of Hawai i. The BIRC&D is a nonprofit 501(3)(c) since 1993 and has the capacity to apply for and administer government and private grants. They have partnered with a long list of government agencies and nongovernmental organizations. Projects administered through the BIRC&D have included plans and studies and improvement projects. To receive BIRC&D assistance, a project application is made to the RC&D Council, which decides on approval and further steps to identify funding sources Hawaii Community Foundation The Hawaii Community Foundation (HCF) is the top granting foundation in Hawai i with an annual giving of nearly $25 million. HCF aggregates diverse fund sources and manages assets of other private foundations. Environmental grants are one of the many areas for which the HCF provides funding. Two current grant programs that support community-based implementation projects are the Group 70 Foundation Fund and the HFC/NOAA Community-based Coastal Restoration Grant Program. The funding opportunities through the HCF will likely continue to change with the priorities of the private foundations. The HCF program has been used for both planning and implementation of environmental projects Other Foundations A number of other private foundations offer grants to community-based organizations for beneficial projects in Hawai i. Environmental projects constitute a relatively small portion of the grants, with education and community enhancement being the largest sectors of grant opportunities. Most foundations require the applicant to be a nonprofit with a 501(3)(c) tax status. A listing of Hawai i foundations and the level of annual grant-giving is shown below. Foundation Name Total Annual Giving Harold K. L. Castle Foundation $7,494,846 Atherton Family Foundation $4,526,762 McInerny Foundation $3,174,045 The Victoria S. and Bradley L. Geist Foundation $1,636,101 Alexander & Baldwin Foundation $1,618,235 Hawaiian Electric Industries Charitable Foundation $1,433,590 Bank of Hawaii Charitable Foundation $1,247,

91 First Hawaiian Foundation $1,184,344 Barbara Cox Anthony Foundation $1,065,793 Cooke Foundation, Limited $1,052,982 Hindu Heritage Endowment $1,048,958 George N. Wilcox General Trust $867,634 HMSA (Hawaii Medical Service Association) Foundation $780,611 Hung Wo and Elizabeth Lau Ching Foundation $725,050 Leburta Atherton Foundation $598,000 The James and Abigail Campbell Family Foundation $588,000 The Cades Foundation $532,000 J. Watumull Fund $505,000 The Kosasa Foundation $491,000 Finance Factors Foundation $441,132 The Richard T. Mamiya Charitable Foundation $360,526 Antone and Edene Vidinha Charitable Trust $329,200 Teresa F. Hughes Trust $320,000 First Insurance Company of Hawaii Charitable Foundation $319,954 Servco Foundation $293,895 Samuel N. and Mary Castle Foundation $277,500 Fred Baldwin Memorial Foundation $238,106 The Earl and Doris Bakken Foundation $190,931 Na Lei Aloha Foundation $184,240 George P. and Ida Tenney Castle Trust $152,000 The Edward and Peggy EU Foundation $68,630 George F. Straub Trust $50,000 Hawaii People's Fund $45,000 Hawaii National Foundation $16, IMPLEMENTATION PROCESS This section provides a basic roadmap for the implementation of stream stabilization project in Waipi o. It is important to have a clear understanding of the different phases for implementation and their elements in order not to be stymied at a later time for failing to complete an earlier requirement. While a generalized sequence of phases is described below, there certainly will be circumstances that will require deviation from the roadmap Water Committee The Water Committee of the Waipi o Community Circle or similar group should be charged by the community to implement the Waipi o Stream Stabilization Project. The group should be expanded to include representatives of major stakeholder groups in Waipi o. The Water Committee should invite representatives from the County, State, and Federal agencies that have programs for planning and installation or have expertise in the discipline areas that are needed to formulate and implement the project. A position should be established to be responsible for maintaining the documents and records of the Water Committee, ensuring necessary announcements and notices are made, and serving as the point of contact and clearinghouse for the Waipi o Stream Stabilization Project. A basic agreement on the project objectives and major elements of the project should be struck among the Water Committee members and government and organization members. A memorandum of understanding (MOU) can be used to document the agreement on objectives and describe the major elements to be pursued by the Water Committee. The MOU can also describe the roles and responsibilities of each member and schedule the tasks and milestones for the project. The Water Committee should prepare a Statement of Need for the project which can be used to request program assistance from agencies and nongovernmental organizations. The Statement of Need can be based on the and Stream Stabilization 9-7

92 Preliminary Report and the Waipi o Valley Stream Management Study. The Statement of Need should include a problem statement, descriptions of efforts that have been undertaken, partnerships that support action, possible solutions to the problem, and resources and funding required to address the problem. The Statement of Need can also be used to include the Waipi o Stream Stabilization Project into State and County resource and area plans which are often updated on five to ten year cycles. The Statement of Need can be summarized on a flyer-type Fact Sheet that can be widely distributed and easily understood. Another early task of the Water Committee will be to establish support for the project alternatives among the many stakeholders of the stream stabilization project and Waipi o Valley residents and visitors. Informational meetings and media announcements can be used to generate public understanding of the project. It is important that stakeholders understand that the project is still developing during the early planning phase and that they will able to have input to ensure that their interests are protected or advanced Plan Preparation A formal, detailed Plan should be prepared for the project to reduce misunderstandings and uncertainties. The Plan will provide a consistent description of the project, especially to reviewers. The Water Committee should identify and pursue programs or funding sources to assist with the Plan development. When completed, the Project Plan should include the information about the project that is required by the funding programs or agencies, be able to serve as the basis to determine environmental and social impacts for the environmental review document, and provide the preliminary information to complete engineering and structural designs. The Plan should also make the compelling case that the project is needed and will describe the consequences of no action. Selection of the alternative will be made during the Plan preparation process. More design details are added at this stage. Preliminary design drawings can be prepared to be inserted into the Plan Environmental Review The nature and magnitude of the projects proposed in Waipi o and the environmental and cultural sensitivity of the location will warrant considerable environmental evaluation, review, and disclosure of effects prior to implementation If State or County land or funds are used in implementation, the Hawai i environmental review process, as directed by HRS, Chapter 343, will be triggered. A Hawai i EA or EIS will need to be prepared. If a federal funding program is used in implementation, a federal EA or EIS will be prepared as directed by the National Environmental Policy Act. The State and federal documents are similar and can be prepared concurrently as a joint document. The environmental review should occur concurrently with the preparation of the Plan. Initial contacts with regulatory agencies and stakeholder groups will likely provide broad boundaries or constraints for the project. The Plan will often need to be adjusted to these constraints. If the EA or EIS is complex, it will likely be prepared by a specialized consultant through a contract administered by a partner agency or by the Water Committee. Identification of permit requirements is also done at this time. Often the environmental tasks can be combined with the Plan preparation task in a single contract Design Once the Project Plan and Final EA or EIS are completed and approved, the design can be finalized to provide construction drawings for installation. Important information for the designers provided by the Project Plan will include performance criteria, capacity requirements, regulatory requirements, and limitations developed by the EA or EIS. The final design will be used to estimate the installation cost of the project. The estimated cost will be used to request funding from funding sources and to obtain a contractor for the installation. 9-8

93 9.5.5 Permitting The environmental concerns that are discussed in the EA or EIS must be specifically addressed and have mitigation plans prepared for any adverse effects when applying for permits from government agencies. Many permits will likely not be acquired until final designs are completed and affected properties are fully identified. It is recommended that plans for permit acquisition are discussed early in the planning and design phases to avoid potential roadblocks. Consult with agencies prior to submitting permit applications to familiarize agency personnel with the project, to ensure that the project is within permit parameters, and to ensure the completeness of the permit application. Many delays in permit issuance stem from requests for additional information. The permit time clock is often stopped during information requests. 9-9

94 10.0 CONCLUSIONS Frequent influxes of sediment resulting from erosion in the upper watershed creates conditions of geomorphic instability within the Waipi o Valley. The instability has led to adverse affects within the valley, including streambank erosion, increased flood risks, and channel migration. AECOM investigated the geomorphology of the river valley, as well as the hydrology and hydraulics of the stream and watershed, to develop alternatives that address the current issues in the valley. The existing conditions assessment resulted in the identification that the current stream geometry at the two project sites was oversized, causing reduced flow velocities. The lower velocities resulted in increased deposition of sediment and bedload at the two sites. Based on stable stream channel sections identified near the two project sites, new channel geometries were established. The basis of the alternative development was to provide for a channel geometry that would transport anticipated sediment loads through the project sites, instead of allowing deposition. Along with the channel geometry, additional elements were also developed for the two sites that would address streambank erosion and stabilize the channel migration. The elements identified at each project site can be implemented individually, or as a whole, depending on the level of funding available for implementation. Rock vanes are recommended to be used to increase the hydraulic characteristics of the project reaches for transporting the anticipated sediment and bed loads through the valley. The dynamic nature of the stream will likely continue and sediment pulses will continue to push through the system. The alternatives presented here are intended to provide control points within the valley to protect critical irrigation and valuable farmland. The elements associated with the alternatives can be designed for use in multiple locations throughout the watershed and should be considered a tool to local farmers residences. 10-1

95 11.0 REFERENCES Chow, V. T Open Channel Hydraulics. New York: McGraw-Hill Book Co. Lane, E. W The Importance of Fluvial Morphology in Hydraulic Engineering. American Society of Civil Engineering Proceedings 81, 745: Leopold, L. B., G. M. Wolman, and J. P. Miller. (1964). Fluvial processes in geomorphology. San Francisco, CA: W. H. Freeman. USDA-NRCS, Waipi o Valley Stream Management Plan. Natural Resources Conservation Service. Kamuela, HI. USDA-NRCS National Engineering Handbook Part 654: Stream Restoration Design. Oki, D. S., S. N. Rosa, and C. W. Yeung Flood-frequency estimates for streams on Kaua i, O ahu, Moloka i, Maui and Hawai i, State of Hawai i. U.S. Geological Survey Scientific Investigation Report , 121 p. Rosgen. D Watershed Assessment of River Stability and Sediment Supply. Ft Collins, Co: Wildland Hydrology. Rosgen, D. L. & H. L. Silvey. (2005). The reference reach field book. Fort Collins, CO: Wildland Hydrology Books. Virginia Department of Environmental Quality (VDWQ) The Virginia Stream Restoration & Stabilization Best Management Practices Guide. s 11-1

96 Appendix A Stakeholder Meeting Notes

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98 and Stream Stabilization Preliminary Investigation Island of Hawaii Meeting Minutes Date: September 13, 2011 Location: Teleconference, various locations Subject: Draft report comments Remarks: 1. For the Linda Beech Site: a. AECOM should move forward with a modified version of Alternative 4, with the river channel shaping, but without the backfilling of the right channel. The right channel is need to provide water to the farmers. b. Compacted rock should be used at the ford crossing, not concrete. 2. For the Kawashima Site: a. AECOM should use a hybrid using Alternative 1 as the starting point and adding rock vanes upstream of the waterhead. b. AECOM should add concrete piling in front of the waterhead intended to redirect debris/trees downstream. Wood is not recommended to construct vanes or piles. Piles should be aligned with the edge of the stream so that debris is deflected downstream. c. AECOM should add bank protection/vanes/etc downstream of the waterhead near the coconut trees to address current erosion issues. d. A culvert is not preferred by the farmers due to maintenance issues. Farmers prefer to keep an open ditch system. 3. For the final report, AECOM should add a Selected Designs section that included drawings related to the final site plans and also updated Selected Design cost estimates.

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100 Appendix B Alternative Designs

101 UNITED STATES DEPARTMENT OF AGRICULTURE NATURAL RESOURCES CONSERVATION SERVICE WAIPI'O VALLEY FLOOD DAMAGE REDUCTION AND STREAM STABILIZATION PRELIMINARY INVESTIGATION HAMAKUA, HAWAII PREPARED BY: LOCATION MAP INDEX TO DRAWINGS APPROVALS

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111 Appendix C Conceptual Plans

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