OXBOW RESTORATION PROJECT RECONNECTING TO OUR RIVER AND OUR HABITAT

Transcription

1 OXBOW RESTORATION PROJECT RECONNECTING TO OUR RIVER AND OUR HABITAT John O Meara, Jane Tesner, Razik Alsaigh Environmental Consulting & Technology, Inc Washington Blvd., Suite 3500 Detroit, MI And Tilton & Associates, Inc. 501 Avis Dr., Suite 5C Ann Arbor, MI ABSTRACT The Rouge Oxbow Restoration Project is located at the Henry Ford Museum & Greenfield Village (HFMGV) adjacent to the Rouge River in Dearborn, Michigan. Until recently, the water quality of the Rouge River had degraded significantly as a result of pollutant loadings from various sources. In addition, development within the watershed had resulted in a significant reduction in the percentage of pervious area tributary to the River. A flood control project on the River was constructed in the 1970s to prevent flooding in the river basin. One of the main features of the project was the enlargement and concrete realignment of the approximately 9 miles of the original river. Consequently, a number of river meanders were cut off, creating several shallow oxbow wetlands. The main objective of the Oxbow Restoration Project is to enhance the ecological viability of this western-most Oxbow by creating valuable fish and wildlife habitat, restore functioning riverine wetlands that have been lost due to channelization and improve water quality. Secondary objectives include additional flood storage, providing educational/interpretative opportunities and improved aesthetics of the channel and upland island. The project will be completed in three phases: Phase I - Oxbow Restoration; Phase II - Combined Sewer Overflow (CSO) Modifications; and, Phase III - Open Cut Connection to the Rouge. An existing storm sewer will provide river water to the Oxbow during Phase I and a siphon will connect the wetlands on both sides of the existing CSO until Phase II. Phase I will provide restoration of the Oxbow Wetlands similar to riverine wetlands common in southeast Michigan rivers. The restoration will provide a 2,200-ft channel that will vary in width from 15 to 105 feet and depths of 3 to 6 feet. The channel will be surrounded by 3 acres of submergent and emergent wetland systems that provide habitat for various fish and aquatic species. Aquatic habitat will be enhanced by appropriate placement of woody material (shelter) and submergent plant species in and near deeper pool areas with plants such as Pickerel Weed, Arrow Arum, Water Lily, and Water Plantain. The wetland will transition to 10 acres of existing and proposed upland woodlands and open areas and will be planted with various tree, shrub, grass and wildflower species. Bioengineering techniques will provide stabilization of slope areas. Plant species have been chosen to reflect historic southern Michigan riverine wetland and floodplain systems, as well as including species that were utilized by the indigenous people (primarily Potowatomi and Chippewa) for food, medical and cultural materials. Upon

2 stabilization, certain fish species will be introduced to the oxbow wetlands, including bass, channel catfish and bowfin. Various wildlife anticipated to use these habitat areas include macroinvertebrates, amphibians, reptiles, waterfowl and small mammals such as black crowned night heron, wood duck, frogs, turtles, mink, and muskrat. Upon completion of construction, the oxbow upland will have a new educational program based on the people that originally occupied the area and their use of the river, developed and implemented by HFMGV. It is anticipated that project will also be utilized by the adjacent Henry Ford Academy for biological/ecological studies, including water quality/quantity monitoring, botanical and wildlife surveys. Phase I restoration is estimated to take 6 to 9 months to construct with an additional 2 years establishment period prior to Phases II & III. This time shall allow the wetland system to stabilize and be maintained accordingly. Phase I construction will begin in May 2001 and therefore the restoration, less establishment, should be completed by the end of KEYWORDS River restorations, wetlands, ecology restoration, habitat restoration BACKGROUND The Rouge Oxbow Restoration Project is located at the Henry Ford Museum & Greenfield Village (HFMGV) adjacent to the Rouge River in Dearborn, Michigan. HFMGV STUFF. Figure 1: Rouge River Location Map Figure 2: Site Location Map Until recently, the water quality of the Rouge River had degraded significantly as a result of pollutant loadings from various sources. Additionally, because of its characteristics and its watershed, the lower reaches of the Rouge River had always been susceptible to flooding. The flat river slope and the meandering channel could not pass the large flows associated with major precipitation events. Upstream urbanization continued to exacerbate this problem culminating in the floods of the local communities. The tremendous financial impact from these floods caused the communities to seek help from the federal government. The resulting flood control project

3 was authorized by the Flood Control Act of 1962 to prevent flooding of the Dearborn/Melvindale area of the Rouge River. The project was completed in the mid The basis of design for the project was to enlarge the cross sectional area of the river channel, to reduce the flow resistance through the use of concrete, and to realign (straighten) the main channel of the river from the navigation turning basin at the Detroit-Dearborn city limit to Michigan Avenue in Dearborn. The channel realignment reduced the channel length from 5.8 miles to 4.2 miles by straightening the meandering channel. Consequently, a number of oxbow bends were cut off from the realigned channel. Figure 3 shows the United States Army Corps of Engineers (USACOE) channelized plan drawing of the area. Figure 4 and 5 show the channelized portion of the Rouge River. In addition, development within the watershed had resulted in a significant reduction in the percentage of pervious area tributary to the River. Figure 3: USACOE Channelization Plan (From USACOE Rouge River Flood Control Project The resulting concrete channel was hydraulically efficient and cost effective. Unfortunately, it also destroyed the aquatic habitat and all but precluded the passage of most fish from the abundant Detroit River to the upper reaches of the Rouge River. In an effort to provide habitat, resting locations for potential migratory fish, recreational opportunities and to restore wetland area, Wayne County, Michigan and the Henry Ford Museum & Greenfield Village (HFMGV) have undertaken the restoration of the Oxbow. The Project discussed in this paper retains the flood control characteristic of the original project while helping to restore some of the habitat destroyed by channelization

4 PRE-RESTORATION CONDITIONS General Conditions The width of the oxbow bend prior to the channel improvement ranged from 75 to 150 feet (ft), and the preconstruction oxbow bottom elevation ranged from 568 to 570 ft-ngvd. The length of the oxbow was about 2,980 ft. Figure 6 provides an aerial view of the oxbow area prior to any construction activities. A major Combined Sewer Overflow (CSO) outlet owned and operated by the City of Dearborn also transects the oxbow. The construction of the CSO discharge required to transect the oxbow island was performed as part of the original flood control project. Fill material has been placed in the oxbow on several occasions since the channel was constructed. The former oxbow channel area has been filled in to various elevations ranging from 573 to 579. The typical fill elevation was about 576 ft-ngvd. The type of fill materials in the oxbow, include earth, bricks, concrete, steel bars, tree branches, coal piles, refrigerators and other urban debris, including the paverbial kitchen sink. Wetlands Conditions Two major features contribute to the conditions of the preconstruction wetlands. First, the Figure 6: Aerial View of Oxbow Area water input for the wetland was limited to precipitation events and surface water flow, including storm water discharge from culvert outlets. The second feature was the presence of construction debris and fill material within various portions of the channel. These two factors combined to influence the wetland conditions. The water input encouraged the oxbow to become a forested wetland including large deciduous trees and shrub material. There was little groundcover vegetation to provide food and shelter for wildlife. There were areas of standing water especially during the spring months, but the areas were vulnerable to drying out towards the end of the summer. The water depths in these wetlands were shallow and variable and therefore did not provide suitable habitat for fish and amphibians. The fill material

5 had interrupted contiguous portions of the wetland, thus creating smaller wetlands throughout the oxbow channel. Due to the nature of some of the fill material, vegetation was unable to establish in these areas. Figure 7: Pre-Construction Oxbow Channel Figure 8: Pre-Construction Oxbow Channel Some of the wetland vegetation species included the following: Silver maple (Acer saccharinum), FACW Green Ash (Fraxinus pensylvanica), FACW Cottonwood (Populus deltoids), FAC+ Wildlife within the oxbow channel potentially included woodland species such as opossum (Didelphis virginiana), chipmunk (Tamias striatus), fox squirrel (Sciurus niger), raccoon (Procyon lotor), and various bird species such as downy woodpecker (Picoides pubescens) and white-breasted nuthatch (Sitta carolinensis). Hydroperiod Conditions The flood flows and flooding levels expected for a range of return periods in the Rouge River at HFMGV are given below. The long-term average Rouge River level of feet (Dearborn datum) was to be used for the design.

6 Table 1: Flood Flows and Flooding Levels Return Period Flood Flow (cfs) Flooding Level (feet- Dearborn datum) (Years) 1 1, , , , , Return Period Flood Flow (cfs) Flooding Level (feet- Dearborn datum) (Years) , , , RESTORATION PLAN The main objective of the Oxbow Restoration Project was to enhance the ecological viability by creating valuable fish and wildlife habitat, restoring functioning riverine wetlands that have been lost due to channelization and improving water quality. Secondary objectives included additional flood storage, providing educational/interpretative opportunities and improved aesthetics of the channel and upland island. The project is being completed in three phases: Phase I - Oxbow Restoration; Phase II - Combined Sewer Overflow (CSO) Modifications; and, Phase III - Open Cut Connection to the Rouge. An existing storm sewer will provide river water to the Oxbow during Phase I and a siphon will connect the wetlands on both sides of the existing CSO until Phase II. The final conceptual plan and cross sections of the oxbow are shown in Figure 9, 10, and 11. Figure 9: Final Design Layout

7 Figure 9: Final Design Layout Figure 11: Conceptual Cross-Sections

8 Phase I Restoration Ecology Phase I will provide restoration of the Oxbow Wetlands similar to riverine wetlands common in southeast Michigan rivers. The restoration is providing a 2,200-ft channel that will vary in width from 15 to 105 feet and depths of 3 to 6 feet, with some deeper holes for fish habitat. The channel is be surrounded by 3 acres of submergent and emergent wetland systems that provide habitat for various fish and aquatic species. Aquatic habitat is being enhanced by appropriate placement of woody material (shelter) and submergent plant species in and near deeper pool areas with plants such as Pickerel Weed, Arrow Arum, Water Lily, and Water Plantain. The wetland will transition to 10 acres of existing and proposed upland woodlands and open areas and will be planted with various tree, shrub, grass and wildflower species. Figure 11: Conceptual Cross-Sections Figure 10: Conceptual Cross-Sections Figure 12: Water Lily Bioengineering techniques are being used to provide stabilization of slope areas. Plant species have been chosen to reflect historic southern Michigan riverine wetland and floodplain systems, as well as including species that were utilized by the indigenous people (primarily Potowatomi and Chippewa) for food, medical and cultural materials. Figure 13: Water Plantain Upon stabilization of the wetland, certain fish species will be introduced to the oxbow wetlands, including bass, channel catfish and bowfin. Various wildlife anticipated to use these habitat areas include macroinvertebrates, amphibians, reptiles, waterfowl and small mammals such as black crowned night heron, wood duck, frogs, turtles, mink, and muskrat.

9 Phase I Restoration Hydraulics Prior to channelization of the Rouge River, most of the HFMGV property drained into the oxbow through several 12 to 24 inch diameter storm drain outlets. When the Rouge River channel was constructed in the early 1970's, most of the storm drainage was rerouted to the Suwanee Lagoon (another former oxbow) on the HFMGV property. The Suwanee Lagoon overflows into a storm water pump station which is located near the lagoon on the Greenfield Village side of the oxbow. The pump station lifts overflow from the Suwanee Lagoon into a discharge manhole, then flows by gravity from the discharge manhole into a junction chamber and then into a 60 inch storm drain which outlets to Rouge River channel. A section of the 60 inch diameter storm drain in the bottom of the oxbow channel is being removed to provide the hydraulic connection. Two headwalls are being constructed on the 60 inch diameter storm drain: a headwall for discharges into the oxbow wetland from the Suwanee Lagoon pump station; and headwall for discharges from the oxbow to the Rouge River channel. The storm water pump station will remain in-service when the oxbow is restored. Drainage from HFMGV will be pumped into the oxbow, flow through the wetland oxbow, and subsequently flow to the Rouge River by gravity through a portion of the existing 60 inch diameter drain outlet which is to remain. The water level in the oxbow will be equalized to the river level through this 60 inch diameter connection. The City of Dearborn has a Combined Sewer Overflow (CSO) outfall which crosses Greenfield Village. Prior to the Rouge River channelization, this CSO outfall discharged into the oxbow. When the Rouge River was channelized, the outfall was extend about 970 feet with a 12 foot diameter conduit from the Greenfield Village side of the oxbow to the river channel. The CSO outfall is directly in the way of restoring the oxbow channel. In Phase I, the oxbow is still divided into two sections by the CSO outfall. In order to provide to provide a water supply to the east section of the oxbow, a 36- inch diameter siphon conduit under the CSO outfall is being constructed The 36-inch siphon under CSO outfall will connect two 4 foot diameter manholes risers which will always be underwater. Phase I Educational/Recreational Programming Upon completion of construction, the oxbow upland will have a new educational program based on the people that originally occupied the area and their use of the river, developed and implemented by HFMGV. It is anticipated that project will also be utilized by the adjacent Henry Ford Academy for biological/ecological studies, including water quality/quantity monitoring, botanical and wildlife surveys. The oxbow restoration provides a unique opportunity within the HFMGV to provide passive recreational and educational opportunities. The structure of activities at the HFMGV provides a forum for experiencing a variety of natural ecosystems. Passively, the restoration efforts can be viewed from the rail cars on the passenger railroad as well as from observation areas on the upland area interpretive displays. The educational opportunities arise from historical interpretations that can be drawn from the setting including utilizing signage, activities, and

10 specialized displays (i.e. a Native American birch canoe anchored at the shore of the oxbow channel). Educational opportunities also exist with the close proximity of the Henry Ford Academy in the village. Students and educators may elect to participate in monitoring the growth and success of the restoration project via vegetation monitoring, water quality sampling, water flow monitoring, wildlife monitoring, etc. Many subjects can make use of the various natural areas in the channel area to enhance learning, such as math, science, art, history, engineering and music. Phase I Construction Conventional excavation equipment is being used to remove the fill material within the oxbow channel. Using such equipment as backhoes and dozers makes this much more of a straight forward grading project and allowed a wider range of qualified contractors to bid on the project. Initial construction activities began in July 2001, with an extensive clearing and grubbing operation. This was intended to not only reestablish the limits of the channel but to also provide for specified forested habitat zones. Figure 14: Clearing & Grubbing Figure 15: Habitat Half of the fill that was removed was used to structure areas within the upland area. However, soils/sediment that was mixed in with the urban fill (debris, brick, concrete, mortar and tree branches) was hauled off to a landfill for disposal, avoiding the difficult and costly task of separating out the urban material. Figure 16: Excavation

11 At the time that this paper was being written the following construction activities were still to be completed: Construction of the siphon with manhole risers under the 12-foot diameter Dearborn CSO outfall. Removal and disposal of approximately 160 feet, 60-inch RCP storm sewer. The hydraulic connection to the Rouge River. Placement of habitat augmentation and wetland seeding and plantings. Stocking the oxbow with fish. Wetland Maintenance Phase I restoration is estimated to take 3 to 6 months to construct with an additional 2 years establishment period prior to Phases II & III. This time shall allow the wetland system to stabilize and be maintained accordingly. Phase I construction began in July 2001 and therefore the restoration, less establishment, should be completed by the end of ACKNOWLEDGEMENTS Wayne County Department of Environment would like to thank Environmental Consulting & Technology, Inc. of Detroit, Michigan and Tilton & Associates of Ann Arbor, Michigan for their leadership, design, and construction oversight for this project. Additionally, this project has been funded in part by grants, from the State of Michigan under its Clean Michigan Initiative and from the USEPA. REFERENCES U.S. Army Engineers District, Detroit, CORPS of Engineers (1972) Rouge River Flood Control Project I:\PROJECTS\Oxbow Construction\Public\WEF Watershed 2002 paper.doc