Boise River Riparian Corridor Stewardship Plan

Transcription

1 Boise River Riparian Corridor Stewardship Plan Barber Park to Glenwood Bridge / West Boise Wastewater Treatment Facility September 05 Authority: Section of the Water Resource Development Act of 974 Planning Assistance to States

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3 TABLE OF CONTENTS ACRONYMS AND ABBREVIATIONS. v SECTION.0 - INTRODUCTION. Purpose and Location.... Riparian and Riverine Sustainability Plan... SECTION.0 - BOISE RIVER RIPARIAN PLANT COMMUNITIES COVER TYPE MAPPING. Methodology.... Floodplain Cover Types Vegetation Condition Class Condition Class Condition Class Condition Class Boise River Corridor Cover Types Descriptions Cover Type - Mature Cottonwood Cover Type a - Mature Cottonwood-River Edge Cover Type - Immature Pole Cottonwood Cover Type 4 - Cottonwood or Willow Seedlings Cover Type 5 - Abandoned Channels with Mix of Willows Cover Type 6 - Herbaceous Wetland Vegetation Cover Type 6a - Herbaceous Upland Vegetation Cover Type 7 - Exposed Cobble Riverbed Cover Type 8 - Main Channel Water Surface Cover Type 9 - Off Main Channel Water Surface Cover Type 0 - Agricultural Field Cover Type - Domestic or Commercially Developed Land Cover Type a -Former Gravel Pit Filled with Water or Constructed Pond / Lake Relationship of Vegetation Cover Type to Boise Development Code Section D. Class A Lands and Waters Areas Extremely Important for Preservation Section D. Class B Lands and Waters Areas Moderately Important for Preservation... 9 i

4 .5. Section D.4 Class C Lands and Waters Areas Least Important for Preservation..9 SECTION.0 COVER TYPE MAINTENANCE AND RESTORATION. Vegetation Condition Class.... Cover Type Changes from 00 to Condition Class by Cover Type in Cover Type - Mature Cottonwood Existing Conditions Recommended Maintenance and Restoration Actions Cover Type a - Mature Cottonwood-River Edge Existing Conditions Recommended Maintenance and Restoration Actions Cover Type - Immature Pole Cottonwood Existing Conditions Recommended Maintenance and Restoration Actions Cover Type 4 - Cottonwood or Willow Seedlings Existing Conditions Recommended Maintenance and Restoration Actions Cover Type 5 - Abandoned Channels with Mix of Willows Existing Conditions Recommended Maintenance and Restoration Actions Cover Type 6 - Herbaceous Wetland Vegetation Existing Conditions Recommended Maintenance and Restoration Actions Cover Type 6a - Herbaceous Upland Vegetation Existing Conditions Recommended Maintenance and Restoration Actions Cover Type 7 - Exposed Cobble Riverbed Existing Conditions Recommended Maintenance and Restoration Actions Cover Type 8 - Main Channel Water Surface..... Existing Conditions..... Recommended Maintenance and Restoration Actions.... Cover Type 9 - Off Main Channel Water Surface..... Existing Conditions... ii

5 .. Recommended Maintenance and Restoration Actions....4 Cover Type 0 - Agricultural Field Existing Conditions Recommended Maintenance and Restoration Actions....5 Cover Type - Domestic or Commercially Developed Land Existing Conditions Recommended Maintenance and Restoration Actions....6 Cover Type a - Former Gravel Pit Filled with Water or Constructed Pond / Lake Existing Conditions Recommended Maintenance and Restoration Actions... SECTION HABITAT ENHANCEMENT PLAN 4. Habitat Improvements Black Cottonwood Regeneration Considerations Sexual Reproduction Asexual Reproduction Recommendations Yellow-billed Cuckoo... 6 SECTION TOOLS TO ASSIST WITH PEOPLE MANAGEMENT 5. Signage Brushing Restoration and Fencing Formalize Some Informal Trails Close and Restore Unacceptable Trails SECTION INVASIVE PLANT MANAGEMENT 6. Management Methods Early Detection Rapid Response (EDRR) Inventory and Monitoring Prioritization of Species and Sites Restoration Known Invasive Species Other Species of Concern False Indigo iii

6 6.. Silver Maple Russian Olive Black Locust Other Species SECTION PEST CONTROL PLAN 7. Beaver Canada Geese SECTION REFERENCES List of Tables Table - USGS Stream Gage Data at Glenwood Bridge... Table - List of Cover Types... 5 Table - Comparison of Cover Types: 00 and Table - Vegetation Condition Class Areas by 05 Cover Types... 4 Table 4- Suggested Plants Species for Riparian Habitat Restoration... 4 Table 6- Invasive Plant Species Present in Ada County, Idaho List of Photos Photo - Cover Type... 6 Photo - Cover Type a... 7 Photo - Cover Type... 8 Photo -4 Cover Type Photo -5 Cover Type Photo -6 Cover Type 6... Photo -7 Cover Type 6a... Photo -8 Cover Type 7... Photo -9 Cover Type Photo -0 Cover Type Photo - Cover Type Photo - Cover Type... 7 Photo - Cover Type a... 8 Photo 4- Successful unmowed buffer with young cottonwood growth Photo 5- Informal trail junction blocked by log with prompter sign Photo 5- Symbolic restoration/fencing treatment at informal trail junction... 9 Photo 6- Russian olive stand List of Appendixes Appendix A: Appendix B: Cover Type Maps with Vegetation Condition Class Geographic Information System Metadata iv

7 ACRONYMS AND ABBREVIATIONS Acronym/ Abbreviation Boise Parks cfs cm dbh EDRR ESA HGM IDA IDAPA m NMID USACE USFWS USGS Definition Boise Parks and Recreation Department cubic feet per second centimeters diameter at breast height Early Detection and Rapid Response Endangered Species Act hydrogeomorphic Idaho Department of Agriculture Idaho Administrative Procedures Act meters Nampa-Meridian Irrigation District United States Army Corps of Engineers United States Fish and Wildlife Service United States Geological Survey v

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9 . Purpose and Location SECTION.0 - INTRODUCTION In 00, the U.S. Army Corps of Engineers, Walla Walla District (USACE) completed an inventory of vegetation cover types and recommended maintenance and restoration measures to facilitate management needs identified in the Boise Parks and Recreation Department (Boise Parks) 999 Boise River Resource Management and Master Plan. The USACE inventory and recommendations were documented in the Boise Parks and Recreation Department, Stewardship Plan for the Riparian Corridor from Barber Park to Glenwood Bridge (USACE 00). Recently, Boise Parks has completed and Boise City has adopted an update to its Boise River Resources Management and Master Plan (Boise Parks 04) which includes a recommendation to update the 00 USACE inventory and stewardship plan. Boise Parks and USACE have partnered to complete the updated inventory. The USACE has conducted the study under the authority of section of the Water Resources Development Act of 974, as amended. The authority allows the USACE to assist States, local governments, and Indian Tribes with preparation of comprehensive plans for development, utilization, and conservation of water and related land resources. The updated vegetation cover type inventory will show the changes in cover types that have occurred since 00, providing the Boise Parks with information to inform future management actions and priorities. Vegetation condition class by cover types were also identified during the riparian inventory update. Vegetation condition classes identify the ecological condition of the existing vegetation and will assist Boise Parks with long-range planning to preserve values and conditions desired by local residents. The study area is located in Ada County and includes the communities of Boise and Garden City, Idaho. The inventoried area includes the Boise River Greenbelt and Cityowned lands for the Boise River corridor from the Nampa-Meridian Irrigation District (NMID) diversion at Eckert Road to Glenwood Bridge, delineated by a 00-foot setback from the 6,500 cubic feet per second (cfs) flow line on both sides of the river corridor. Additionally, the inventory included a,000-foot linear reach of City-owned lands along the Boise River at the West Boise Wastewater Treatment Facility, extending 00 feet from the 6,500 cfs flow line.. Riparian and Riverine Sustainability Plan Riparian habitats are critical components of western United States landscapes. Most aquatic resources are dependent on the health of riparian habitats and 80 to 90 percent of all terrestrial species are linked by life-cycle requirements to riparian areas. The hydrogeomorphic (HGM) approach to floodplain and riparian habitat assessment used in the 00 study employs a collection of concepts and methods used to develop and apply functional parameters to the process (Hauer, F.R. et al. 00). The approach

10 was initially designed to support the USACE Regulatory Program administration of section 404 of the Clean Water Act, which includes permit review to consider alternatives, minimize impacts, assess unavoidable project impacts, determine mitigation requirements, and monitor the success of mitigation projects. However, a variety of other potential applications for the approach have been identified such as designing mitigation projects, managing wetlands, and long-term monitoring of wetlands. The HGM functional approach was used in this study to support management, restoration, and sustaining riparian habitat. Maintaining characteristic plant communities is dependent on the site capacity to sustain native plant communities appropriate for the Boise River, despite a regulated hydrology and an altered floodplain. Vegetation is maintained by base conditions, especially water regime, nutrient cycling, soil development, and disturbance regimes. Maintaining a plant community characteristic to the floodplains of the region also requires vegetation regeneration processes that permit response to natural disturbance regimes (e.g. flooding, fire, herbivory) and climatic variations. Major changes in vegetation cover, composition (e.g. invasion by non-native plants and uncharacteristic native species), and structure are indications that these functions have been altered.

11 . Methodology SECTION.0 - BOISE RIVER RIPARIAN PLANT COMMUNITIES COVER TYPE MAPPING In 00, USACE identified riparian cover types on both sides of a 0-mile reach of the Boise River, extending from the NMID diversion downstream to Glenwood Bridge, using the HGM approach described by Hauer, F.R. et al. (00). The current effort updated the 00 riparian cover type inventory for the same area, and expanded the mapped area out to 00 feet beyond the 6,500 cfs flow line and also added a,000-foot linear reach of City-owned lands along the Boise River at the West Boise Wastewater Treatment Plant downstream of the Glenwood Bridge. USACE, other Federal agencies, and various academic entities developed the HGM to standardize riparian function and condition assessments. It was selected for the 00 inventory for its simple, straightforward classifying methodology, and the results have been used as a tool by Boise Parks since 00. USACE used the HGM method to complete the current effort to ensure consistency and the ability to directly compare current (05) conditions with those present in 00. The current study also used the process outlined in the USACE Wetlands Delineation Manual (USACE 987) and the Arid West Supplement (USACE 008) for classifying wetland cover types based on vegetation, hydrology, and soil characteristics. The 00 vegetation cover type polygons were used as the starting point for the current mapping effort. USACE used 0 color aerial orthophotography acquired by Boise City as the base layer. USACE personnel developed a draft cover type map from review of the 0 aerial photography and more recent Google Map and Google Earth imagery procured as recently as April 0, 05. Extensive field ground truthing site visits were conducted by USACE personnel May -5 and June 8- of 05 to update and validate the draft vegetation cover types and to determine vegetation condition class. Streamflow data during the 05 field visit was collected using the United States Geological Survey (USGS) stream gage at Glenwood Bridge to compare to flows during the 00 inventory (see table -). Streamflows were somewhat higher during both 05 site visits, compared to flows during the 00 survey. Table.. USGS Stream Gage Data at Glenwood Bridge (USGS 06000) Date CFS Date CFS Date CFS 5// /8/ /5/00 5 5// /9/ /6/00 9 5// /0/ /7/00 5/4/ // /8/00 0 5/5/ // /9/00 68

12 The HGM method divides the inventoried areas into vegetation plant communities. Each vegetation cover type has developed from the specific environmental conditions present. For example, an area with saturated soil conditions throughout the growing season would support wetland vegetation. An area receiving seasonal high water or groundwater would most likely support riparian vegetation. By identifying the specific vegetation cover types present within the riparian corridor as a result of specific environmental conditions, maintenance and restoration strategies can be more easily standardized.. Floodplain Cover Types The floodplains of the Northern Rocky Mountains are complex, both structurally and ecologically. Table - summarizes the most prevalent plant community cover types on the Boise River floodplain. Detailed descriptions of these cover types, which are the most common among floodplain-wetland complexes of alluvial gravel-bed rivers in the northwest, are provided in this section. All of these cover types are found along the Boise River study area except cover type. Two cover types (6 and ) have been modified (6a and a) to more specifically identify the riparian plant communities present in the Boise River floodplain.. Vegetation Condition Class The 05 study included an assessment of ecological condition class for the vegetation cover types to assist Boise Parks in managing their lands. Condition classes assess the ecological condition of the existing vegetation communities with respect to stability and resiliency. The condition classes represent tools for Boise Parks to assist with management decisions based on the ecological/biological conditions present. Attainment of a higher condition class may not necessarily be a management objective... Condition Class The existing plant community, both the overstory and understory, is dominated by native species, historic vegetation composition/structure exists, and the plant community is ecologically stable with high resiliency. Soils are fully functioning and in phase with vegetation development. Dominant ecological processes are fully functioning and plant communities are self sustaining... Condition Class The existing plant community is dominated by a mixture of native and non-native species, vegetation composition/structure is variable, and the plant community stability is ecologically indeterminate with moderate resiliency. The overstory generally contains some native species, but the understory has a significant component of non-native species. The site may have had significant soil alteration and may not be in phase with vegetation development. Plant community may regress due to past disturbances or may recover due to site amelioration treatments or natural disturbance processes. 4

13 Table -. List of Cover Types Cover Type a a 7 Description Mature conifer dominating the canopy with interspersed mature cottonwood. Soils generally developing an A horizon (layer of top soil). Mature cottonwood dominated greater than (>) 6 meters (m) in height and >5 centimeters (cm) diameter at breast height (dbh). May have early stages of conifers that have not reached the forest canopy or may be entirely devoid of conifers. Mature cottonwood river edge dominated >6 m in height and >5(cm) dbh. This cover type separates park land from the river. Since it is an edge and narrow in width, it contains a denser understory due to the availability of sunlight and, in some situations, irrigation. These areas contain great plant diversity and non-native species. Immature pole cottonwood -6 m in height and <5 cm dbh. May also have interspersion of willow. Soils are generally cobble-dominated, with fine sediments accumulating over the surface. Cottonwood or willow seedlings and early pioneer stages up to m in height. Substrate, often with exposed cobble, but may also include deposited silts and sands, not dark in color or organic, indicating very early soil development. Filled or partially filled abandoned channel dominated by a mix of willows, alders, shrubs, and interspersed herbaceous cover. Also, often the dominant cover type along the edge of backwaters. Soils are generally composed of deeper fines (>0 cm), with developing top soil. Herbaceous wetland vegetation dominated, but may have interspersion of an occasional shrub [less than (<) 0 percent of cover]. This cover type is often associated with an older, naturally-filled side channel or abandoned back channel, but may be on any surface type. Herbaceous vegetation dominated by upland vegetation such as grasses, rabbit brush, and sagebrush. Exposed cobble riverbed during base flows and inundated during most annual high flows. May have very sparse herbaceous vegetation or an occasional cottonwood or willow seedling composing <0 percent cover. 8 Main channel surface during base flow; may be in a single channel or may be braided with islands. 9 0 a Off main channel water at the surface during base flow; includes spring brooks, oxbows, scour depressions and ponds, non-flow-through downstream connected side channels, and disconnect side channels. Agricultural field may be meadow or plowed, often planted and hayed; may have origin as a forested surface, but is now logged, or may have been a natural meadow. Domestic or commercially developed land including homes, buildings, gravel pits, transportation corridors, etc. Former gravel pit filled with groundwater. This feature is functioning as a young man-made lake or pond... Condition Class The existing plant community is dominated by non-native species, there has been a major departure from historic vegetation composition/structure, and the plant community is ecologically unstable with low resiliency. Soils have had significant alteration and the plant community is dominated by invasive species. Site potential has been reduced from original conditions and major inputs of energy and/or time would be required to restore ecological structure and function. 5

14 .4 Boise River Corridor Cover Types Descriptions The following describes and provides representative photographs of the cover types found in the Boise River corridor. Photographs were taken during the spring in Cover Type - Mature Cottonwood (00: 5.9 acres; 05:. acres) Cover type consists of mature cottonwoods over 6 m in height, with a dbh greater than 5 cm. Shade controls the understory, which generally consists of shade-tolerant species or regeneration of overstory species in openings. Woody debris of all sizes may be found on the ground, which is important for soil development. This cover type provides both vertical and horizontal cover for a wide variety of wildlife species. Large mammals, such as deer, use these areas. Songbirds use the ground and various levels of canopy; and heron, owls, and raptors use the area for nesting and perching sites. Larger, more secluded areas are used by wintering bald eagles. Mature riparian habitat cycles nutrients, builds viable soils, and provides shade for the river that reduces water temperature and provides large woody debris to shape and create the river s unique habitat for fish and aquatic insects. Because it is the most mature stage of the riparian community, it is also the most difficult to reestablish. Photo -. Cover Type in the background 6

15 .4. Cover Type a - Mature Cottonwood-River Edge (00: 69.7 acres; 05: 0.7 acres) Cover type a has mature cottonwoods greater than 6 m in height, with a dbh over 5 cm. It generally separates the river from park lands or developed areas. Since it is an "edge" and narrow in width, it often contains a denser understory due to the availability of sunlight and water. These areas may contain great plant diversity and sometimes a high percentage of non-native species because of their proximity to developed areas. This cover type functions as a buffer between the river and developed upland areas. It provides many of the same functions as cover type (see section.4.). It cycles nutrients and builds viable soils, shades the river and reduces temperature, and provides large woody debris to shape and create the river's unique habitat for fish and aquatic insects. It also functions as a corridor, allowing fauna to move upstream and downstream and between large areas of habitat that provide life-cycle requirements. Aesthetically and biologically, it is a critical habitat for the river corridor. Photo -. Cover Type a 7

16 .4. Cover Type - Immature Pole Cottonwood (00: 4. acres; 05: 4. acres) Cover type consists of immature pole cottonwood to 6 m in height and less than 5 cm in dbh. It may also include a mixture of willow. Soils are generally cobble dominated, with fine sediments accumulating over the surface. This is an intermediate phase of floodplain development. Willow and cottonwood seedlings colonize newly eroded or deposited sediments. Herbaceous cover may occupy all or portions of the remaining exposed area. Willows are the first species to become established, and provide sediment traps to build soils. When conditions are favorable, cottonwoods gain control of the overstory and shade out competition. This cover type protects floodplain surfaces from erosion. Dense cottonwood stands with mixed shrubs and herbaceous cover provide excellent winter browse for big game (i.e., deer and moose). Small mammals find refuge in the dense cover, and birds feed on seeds and insects. Photo -. Cover Type 8

17 .4.4 Cover Type 4 - Cottonwood or Willow Seedlings (00: 8.0 acres; 05: 5. acres) Cover type 4 consists of cottonwood or willow seedlings up to m in height. Substrate soils often have exposed cobbles, but may also include deposited fines from flooding. Generally, soils exhibit minimal development due to recent deposition and frequent flooding. This cover type can develop within one growing season and be destroyed the next, but it will usually exist over several years with its growth dependent on moisture. Dry years will thin the stand, allowing other plants to grow larger. If protected from erosion, it may develop into cover type. This habitat provides cover for fauna, but only limited food. It provides important escape cover for young birds (e.g., ducks) and even mammals (e.g., deer). Its most important function is trapping debris and sediments. This is the phase that separates herbaceous cover from woody riparian cover. Photo -4. Cover Type 4 9

18 .4.5 Cover Type 5 - Abandoned Channels with Mix of Willows (00: 5.0 acres; 05:. acres) This cover type consists of filled and partially-filled abandoned channels dominated by mixed willows, alders, and shrubs (background), and interspersed with herbaceous cover (foreground). Cover type 5 is often the dominant cover type along the edge of backwaters. Soils are generally composed of deeper fines and development of a top soil horizon. These areas have great diversity and very high productivity. Settling organic matter is deposited in a wet, or seasonally moist environment. Deposited sediments usually provide a good seed bank for species found upstream. These are the herbaceous plants that provide important sources of nutrients. Shrubs, like alder, are nitrogen fixing and free nutrients for other terrestrial and aquatic plants. Shrubs, like silverberry, provide valuable food sources. Many of the floodplains mammals and birds use these areas for feeding. These areas will eventually progress to form the richest woody riparian plants due to their deep organic silts and water supply. Photo -5. Cover Type 5 0

19 .4.6 Cover Type 6 - Herbaceous Wetland Vegetation (00:. acres; 05:. acres) Herbaceous vegetation dominates cover type 6, but may have up to 0 percent shrub cover. This cover type is generally associated with naturally filled side channels or abandoned back channels, or other depressional locations. It may be dominated by emergent vegetation, such as cattails, sedges, rushes, and other wetland species. This cover type is very productive, and provides a wide range of wildlife values. Photo -6. Cover Type 6

20 .4.7 Cover Type 6a - Herbaceous Upland Vegetation (00: 57. acres; 05: 8.5 acres) Cover type 6a consists primarily of herbaceous vegetation (i.e., grasses, forbs) and may contain upland shrubs (i.e., rabbitbrush, sagebrush). This cover type may be associated with natural terraces which have not been altered by river flows or may be the result of development fills that have raised the ground surface above the area influenced by river hydrology. These areas receive moisture only from precipitation, not from surface or subsurface flows. This cover type may add species diversity but has been heavily impacted in many areas by the introduction of invasive species. Photo -7. Cover Type 6a

21 .4.8 Cover Type 7 - Exposed Cobble Riverbed (00: 0.5 acres; 05: 7. acres) Cover type 7 has exposed cobble riverbed during base flow, which is inundated during high flows. There may be very sparse herbaceous vegetation or an occasional cottonwood or willow seedling, composing less than 0 percent of the cover. These areas are usually well armored, and cause directional changes in flow. Exposed cobble shoals are used by waterfowl for resting and molting, and provide a good view of approaching predators. Photo -8. Cover Type 7

22 .4.9 Cover Type 8 - Main Channel Water Surface (00: 74.7 acres; 05: 05. acres) Cover type 8 consists of a main channel surface during base flow, and may be single channel or braided with islands. Healthy natural channels consist of pools and riffles, have diverse vegetated shoreline, and contain woody debris. They may have small or large secondary channels. The channel depicted in the photo is a channel located in the vicinity of the West Boise Wastewater Treatment Facility. Photo -9. Cover Type 8 4

23 .4.0 Cover Type 9 - Off Main Channel Water Surface (00: 0.5 acres; 05:. acres) Cover type 9 provides off-channel water at the surface during base flow. This includes spring brooks, oxbows, scour depressions and ponds, and non-flow-through downstream connected side channels and disconnected side channels. These are special habitat that provide a diversity of unique environments. Spring brooks or creeks are often spawning and rearing habitat for fish, such as cutthroat, brook, rainbow, and brown trout. Because these areas are fed by groundwater, they tend to maintain relatively constant temperatures. Quite often, they remain ice free, even in subfreezing temperatures. The constant high-quality water serves as a nursery area for many species of fish. Waterfowl seek out these areas when other waterways are frozen. The rich water provides many species of aquatic plants and benthic insects. Photo -0. Cover Type 9 5

24 .4. Cover Type 0 - Agricultural Field (00:.4 acres; 05: 4.5 acres) Agricultural field, cover type 0, may be a meadow or plowed, and are often planted and hayed. These areas may have originally been forested areas that were logged, or they may have been a natural meadow. Photo -. Cover Type 0 6

25 .4. Cover Type - Domestic or Commercially Developed Land (00: 65.0 acres; 05: 8.8 acres) Cover type has domestically or commercially developed land including homes, buildings, parks, gravel pits, transportation corridors, etc. Photo -. Cover Type 7

26 .4. Cover Type a - Former Gravel Pit Filled with Water or Constructed Pond / Lake (00: 65. acres; 05: 75.8 acres) Former gravel quarries filled with groundwater or human constructed lakes and ponds make up cover type a. Constructed depressions that intercept alluvial groundwater aquifers can be productive aquatic environments. If the quality of the groundwater is high, a productive freshwater lake can develop. Depressions that intercept groundwater usually become surface discharge areas. These areas do not generally have surface inlets, but surface outlets can form from improved hydraulic passage of the water downgradient. Discharge streams can function as spring creeks, and may have spawning and rearing value. Because these ponds and lakes are closed systems, many management options exist. Photo -. Cover Type a 8

27 .5 Relationship of Vegetation Cover Type to Boise Development Code The Boise City Development Code (Ch , March 0) articulates goals and provides maps for flood protection, fish and wildlife, recreation amenities, and development opportunities. Classifications for lands and waters that provide natural resource functions and values, including the preservation of fish and wildlife amenities were developed as part of the Code. Sections.5. through.5. describe classifications along the Boise River. The use of the Boise Development Code classifications in combination with the vegetation condition class described in section. is recommended to determine management direction and goals. Vegetation condition classifications define the ecological conditions while the Development Code classifications define the management focus..5. Section D. Class A Lands and Waters Areas Extremely Important for Preservation Class A lands and waters are areas that provide extremely important habitat for fish and wildlife, as well as for flood control and protection. The objective is to preserve and protect these lands for their benefits to fish and wildlife in general, and to protect bald eagle, great blue heron, trout, and waterfowl habitat in particular. These areas include, but are not limited to, floodways, diverse plant communities, riparian plant communities, wetlands, eagle winter habitat, islands in the river, and trout spawning areas. Cover types through 9, with the exception of cover type 6a, are considered Class A lands..5. Section D. Class B Lands and Waters Areas Moderately Important for Preservation Class B lands and waters are areas that provide a good potential for improvements to natural resource functions and values. The objective for these lands is to invite development plans which demonstrate improvement to natural resource functions and values, and mitigate negative impacts to existing natural resource functions and values. These areas include, but are not limited to, agricultural lands, gravel pit ponds, and small lakes. Cover types 6a and 0 through a are considered Class B lands..5. Section D.4 Class C Lands and Waters Areas Least Important for Preservation Class C lands and waters are areas that provide limited fish and wildlife habitat. Development should provide landscaping and habitat improvements. These are areas where current uses preclude enhancement of fish and wildlife habitat, diversion dams, residential and commercial development, lands surrounding gravel ponds, and former industrial areas. Cover type is considered the main Class C land. 9

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29 SECTION.0 COVER TYPE MAINTENANCE AND RESTORATION Maintenance and restoration measures are recommended for areas along the Boise River to encourage the perpetuation of desired vegetation communities. Measures are recommended by cover type so that appropriate management practices can be made in the proper locations. The determination of vegetation condition class provides a useful tool for prioritizing areas most in need of management actions. The updated cover type maps (appendix A), which also display condition class, provide locations for improvements and restoration activities. These changes are recommended to improve the ecological function of the vegetation on City of Boise lands along the Boise River.. Vegetation Condition Class Vegetation condition class was previously described in section.. Maps in appendix A show the condition class for the cover types mapped during May and June 05 site visits. Delineations for condition class were modified with a + or - to indicate the observed ecological trends based on the site visits. A + condition class location indicates a plant community currently dominated by an overstory of desired, native tree species (i.e., black cottonwood, willows) and an understory with a mixture of native and non-native species, but it appears that desired, native understory species will remain a major component and influence future overstory composition. Maintenance of existing conditions would likely result in the plant community moving towards condition class, with little additional input of management actions. A - condition class location indicates a plant community currently dominated by an overstory of desired, native tree species (i.e., black cottonwood, willows) and an understory with a mixture of native and non-native species, but it appears that undesired, non-native understory species may outcompete desired native species and may comprise a future overstory dominated by invasive species. These areas likely will require the implementation of significant management actions in the future to prevent them from moving toward condition class. A condition class location indicates a plant community currently dominated by an overstory of desired, native tree species (i.e., black cottonwood, willows) and an understory with a mixture of native and non-native species that could either improve or decline depending on a number of factors. These areas should be monitored to detect ecological trends, either toward condition class or, to determine the level of management action necessary to achieve desired objectives.

30 . Cover Type Changes from 00 to 05 Table - shows the representative areas by vegetation cover type from both the 00 and 05 studies. It must be noted that the 00 survey used a 70-foot setback from the 6,500 cfs watermark, while the 05 survey used a 00-foot setback from the 6,500 cfs watermark. The 05 survey also included the additional area adjacent to the West Boise Wastewater Treatment Facility. Also, as table - shows, streamflows in 05 were higher than during the 00 survey, which may affect the amount of certain cover types, such as cover type 7. Consequently, it is not possible to directly compare the data from the two survey efforts, but trends are apparent. One of the biggest cover type changes from 00 to 05 is the increased amount of developed lands, cover type. Much of this increase may be attributed to the increased study area resulting from the changed setback distance from 70 to 00 feet, but some of it is likely due to increased park development and development of other cover types (agricultural fields, herbaceous upland vegetation, etc.) which have reduced in area since 00. The amount of cover type, mature cottonwood, has decreased from 00, but some of this decrease may be due to the increase in river edge mature cottonwood, cover type a, resulting from development of transportation corridors (trails/roads) and parks within former larger cottonwood blocks, creating more edge forest. The amount of herbaceous wetland vegetation, cover type 6, increased significantly, likely due to restoration activities to develop new wetlands in park areas. Most of the other cover types remained at similar areas as observed in 00, when the size of the increased study area is considered.. Condition Class by Cover Type in 05 Table - shows the vegetation condition class identified during the 05 study by cover type. Condition class was not determined for cover types 7, 8, and 9 which are aquatic environments resulting from stream processes and river flows, and consequently are not generally subject to terrestrial management actions. Condition class for cover types 0,, and a were by definition all determined to be condition class, since they have purposely been altered from the dominant natural environmental processes, functions, and structure to emphasize other resource objectives.

31 Table -. Comparison of Cover Types: 00 and 05 Cover Type 00 Area 05 Area Change 00 to 05 acres percent acres percent percent - Mature Cottonwood %. 9.7% -8.9% a - Mature Cottonwood-River Edge % % +.5% - Immature Pole Cottonwood 4..7% 4..% +0.5% 4 - Cottonwood or Willow Seedlings % % -0.4% 5 - Abandoned Channel with Mix of Willows %. 0.% -0.5% 6 - Herbaceous Wetland Vegetation..%..% +0.9% 6a - Herbaceous Upland Vegetation % 8.5.7% -4.7% 7 - Exposed Cobble Riverbed 0.5.% 7..6% -0.7% 8 Main Channel Water Surface % % -0.6% 9 - Off Main Channel Water Surface 0.5.%..9% +0.6% 0 - Agricultural Field.4.8% % -.4% - Domestic or Commercially Developed Land % 8.8.5% +4.% a - Former Gravel Pit Filled With Water or Constructed Pond / Lake % % -0.% Total Area

32 Table -. Vegetation Condition Class Areas by 05 Cover Types Cover Type - Mature Cottonwood (. acres) a - Mature Cottonwood-River Edge (0.7 acres) - Immature Pole Cottonwood (4. acres) 4 - Cottonwood or Willow Seedlings (5. acres) 5 - Abandoned Channel with Mix of Willows (. acres) 6 - Herbaceous Wetland Vegetation (. acres) 6a - Herbaceous Upland Vegetation (8.5 acres) 7 - Exposed Cobble Riverbed (7. acres) 8 Main Channel Water Surface (05. acres) 9 -Off Main Channel Water Surface (. acres) 0 - Agricultural Field (4.5 acres) - Domestic or Commercially Developed Land (8.8 acres) a - Former Gravel Pit Filled with Water or Constructed Pond / Lake (75.8 acres) Condition Class Area (acres) Percent of Cover Type 46..8% % 70.5.% % % % % % % %.5 6.8% % % % %.9 56.% %.0 9.6% % 0. 5.% % % % % 0..5% % % 0.5.% -.7.0% % % %.0 5.6% - 0..% % N/A % N/A % N/A. 00.0% % % % 4

33 .4 Cover Type - Mature Cottonwood.4. Existing Conditions Cover type, the most abundant cover type in 00 comprising 5.9 acres (8.6 percent), has decreased to. acres (9.7 percent) of the area surveyed in 05. Less than 5 percent of this cover type is in condition class or +, indicating deteriorating ecological conditions. Over 4 percent of this cover type is in condition class - indicating a strong potential that invasive, non-native species will occupy these areas in the future if actions aren t taken. Understory species including false indigo, black locust, silver maple, Siberian elm, etc. have the potential to outcompete regenerating black cottonwood and willow. Many of the overstory black cottonwood is reaching the end of their life span with little regeneration present in the understory. If this condition is not addressed within the next 0-0 years, many of these sites will convert to other, less desirable cover types dominated by non-native species..4. Recommended Maintenance and Restoration Actions Mature riparian habitat are maintained by flooding disturbances creating openings and hydrologic conditions supporting regeneration of cottonwood and willow. Within the study area, river flows are affected by the irrigation and flood risk management operations of Lucky Peak, Arrowrock, Anderson Ranch Dams. Some sections of the river have been channelized and many sections have partial levees restricting river flows. Although the river is not totally altered from its original state, many natural disturbance processes are no longer occurring. To maintain/restore this cover type to desired conditions, the following actions are recommended: Access to major riparian habitat should be limited, and the number of volunteer trails should be reduced. Unnecessary trails should be closed with signage, barriers, vegetation plantings, and fencing. Soil decompaction and planting of native vegetation on unwanted trails is recommended. Planting open areas with native species should occur where resource damage is taking place. Treatment of unwanted invasive species should be conducted to reduce competition to desirable native species, primarily black cottonwood and willow. Mowing along edges of cover type should be reduced to allow existing regeneration of black cottonwood and willow to continue development. Remove and or reattach tree cages that are girdling desired native overstory trees. Initiate an aggressive planting program with desired native species in condition class - areas, after treatment of invasive species has been conducted. 5

34 .5 Cover Type a - Mature Cottonwood-River Edge.5. Existing Conditions Cover type a occupied 69.7 acres (7.8 percent) of the study area in 00 and 0.7 acres (0. percent) of the area surveyed in 05. Less than 0 percent of this cover type is in condition class or +, indicating deteriorating ecological conditions. Over 50 percent of this cover type is in condition class - or indicating a strong potential that invasive, non-native species will occupy these areas in the future. Due to the narrow configuration of this cover type occurring along the river edge in linear strips, additional light reaches the understory prompting the growth of undesirable, non-native species in disturbed areas. Understory species including false indigo, black locust, silver maple, Siberian elm, etc. have the strong potential to outcompete regenerating black cottonwood and willow. Many of the overstory black cottonwood are reaching the end of their lifespan with little regeneration present in the understory. Encroaching vegetation (non-native species) from developed park areas is moving into many of these areas due to their narrow, linear configuration resulting in increased edge exposed to disturbed areas with invasives. If these conditions are not addressed within the next 0-0 years, many of these sites will convert to other, less desirable cover types dominated by non-native species..5. Recommended Maintenance and Restoration Actions Mature riparian habitat are maintained by flooding disturbances creating openings and hydrologic conditions supporting regeneration of cottonwood and willow. This narrow cover type has been greatly impacted by human activities and disturbances that have resulted in a proliferation of non-native species in the understory. To maintain/restore this cover type to desired conditions, the following actions are recommended: Access into and across this narrow cover type should be limited as much as possible, and the number of volunteer trails should be reduced. Unnecessary trails should be closed with signage, barriers, vegetation plantings, and fencing. Soil decompaction and planting of native vegetation on unwanted trails is recommended. Planting open areas with native species should occur where resource damage is taking place. Treatment of unwanted invasive species should be a high priority to reduce competition to desirable native species, primarily black cottonwood and willow. Mowing along edges of cover type a should be reduced to allow existing regeneration of black cottonwood and willow to continue. Remove and or reattach tree cages that are girdling desired native overstory trees. Initiate an aggressive planting program with desired native species in condition class - and areas, after treatment of invasive species has been conducted. 6

35 .6 Cover Type - Immature Pole Cottonwood.6. Existing Conditions Cover type occupied 4. acres (.7 percent) of the study area in 00 and 4. acres (. percent) of the area surveyed in 05, showing a modest increase. More than 6 percent of this cover type is in condition class, indicating fully functioning ecological conditions in those areas. Less than 7 percent of the cover type is in condition class - or, indicating a low potential that invasive, non-native species will occupy this cover type in the future. However, over 55 percent of this cover type is in condition class. These areas should be monitored to detect ecological trends toward condition class or.since the understory contains a mixture of native and nonnative species, future stand composition could either be desired native or non-native species, depending on environmental conditions and management actions over time..6. Recommended Maintenance and Restoration Actions Immature pole cottonwood communities are a desired early to mid-seral stage for riparian cover types. Though the current area in cover type is small, it is important to maintain these sites over time to replace late seral stage cottonwood communities in cover types and a which are declining. This cover type, like many riparian cover types, has been greatly impacted by human activities which have resulted in the introduction of non-native species in the understory. To maintain/restore this cover type to desired conditions, the following actions are recommended: Access into and across this cover type should be limited as much as possible, and the number of volunteer trails should be reduced. Unnecessary trails should be closed with signage, barriers, vegetation plantings, and fencing. Soil decompaction and planting of native vegetation on unwanted trails is recommended. Ongoing monitoring of understory species composition in condition class areas is critical to determine if native species are maintaining their ecological roles or if non-native species are starting to dominate the understory. Treatment of unwanted invasive species should be a high priority to reduce competition to desirable native species, primarily black cottonwood and willow..7 Cover Type 4 - Cottonwood or Willow Seedlings.7. Existing Conditions Cover type 4 occupied 8.0 acres (0.9 percent) of the study area in 00 and 5. acres (0.5 percent) of the area surveyed in 05, showing a modest decrease. More than 56 percent of this cover type is in condition class, indicating fully functioning ecological conditions in those areas. Over 4 percent of the cover type is in condition class - or, indicating a low to moderate potential that invasive, non-native species will occupy significant areas of this cover type in the future. Almost 0 percent of this cover type is in condition class. These areas should be monitored to detect ecological trends toward condition class or. Since the understory of over 4 percent of this cover type contains a mixture of native and non-native species, future stand composition could 7

36 either be desired natives or non-native species, depending on environmental conditions and management actions over time..7. Recommended Maintenance and Restoration Actions Cottonwood and willow seedling communities are a desired early seral stage for riparian cover types. Though the current area in cover type 4 is small, it is important to maintain these sites over time to eventually replace late seral stage cottonwood communities in cover types and a which are declining. This cover type, like many riparian cover types, has been greatly impacted by human activities that have resulted in the introduction of non-native species in the understory. To maintain/restore this cover type to desired conditions, the following actions are recommended: Access into and across this cover type should be limited as much as possible, and the number of volunteer trails should be reduced. Unnecessary trails should be closed with signage, barriers, vegetation plantings, and fencing. Soil decompaction and planting of native vegetation on unwanted trails is recommended. Ongoing monitoring of understory species composition in condition class areas is important to determine if native species are maintaining their ecological roles or if non-native species are starting to dominate the understory. Treatment of unwanted invasive species should be a high priority to reduce competition to desirable native species, primarily black cottonwood and willow. A planting program for black cottonwood and willow should be implemented in suitable areas over the next 0-0 years to create more areas of cover type 4 to replace declining stands of black cottonwood and willow in cover types and a..8 Cover Type 5 - Abandoned Channels with Mix of Willows.8. Existing Conditions Cover type 5 occupied 5.0 acres (0.6 percent) of the study area in 00 and. acres (0. percent) of the area surveyed in 05, showing a significant decrease, though amounts in both years were small. More than 76 percent of this cover type is in condition class, indicating fully functioning ecological conditions in those areas. Over 4 percent of the cover type is in condition class - or, indicating a low potential that invasive, non-native species will occupy major areas of this cover type in the future. Since the understory of over 4 percent of this cover type contains a mixture of native and non-native species, future stand composition could either be desired natives or nonnative species, depending on environmental conditions and management actions over time. 8

37 .8. Recommended Maintenance and Restoration Actions The area of cover type 5 is small and over 76 percent is in condition class, so little maintenance or restoration work is needed at this time. Natural processes are currently dominating, so management actions appear to be maintaining existing desired plant communities. The following actions are recommended: Ongoing monitoring of condition class areas should be conducted to determine if native species are maintaining their ecological roles or if non-native species are starting to invade. Treatment of unwanted invasive species should be a high priority to maintain native plant communities..9 Cover Type 6 - Herbaceous Wetland Vegetation.9. Existing Conditions Cover type 6 occupied. acres (. percent) of the study area in 00 and. acres (. percent) of the area surveyed in 05, showing a significant increase. Much of the increase is the result of restoration efforts. More than 85 percent of this cover type is in condition class, indicating fully functioning ecological conditions in those areas. About percent of the cover type is in condition class -, indicating a low potential that invasive, non-native species will occupy major areas of this cover type in the future. These areas should be monitored for possible invasion by non-native species..9. Recommended Maintenance and Restoration Actions The area of cover type 6 is relatively small but represents a critical habitat component for many organisms. Restoration activities to create more area of this cover type have occurred in recent years and efforts should be continued. Over 85 percent of the existing cover type is in condition class, so little maintenance or restoration work is needed at this time. Natural processes are currently dominating, so management actions appear to be maintaining existing desired plant communities. The following actions are recommended: Ongoing monitoring of condition class and - areas should be conducted to determine if native species are maintaining their ecological roles or if non-native species are starting to invade. Treatment of unwanted invasive species should be a high priority to maintain native plant communities. Continued development of additional areas of cover type 6 should be emphasized..0 Cover Type 6a - Herbaceous Upland Vegetation.0. Existing Conditions Cover type 6a occupied 57. acres (6.4 percent) of the study area in 00 and 8.5 acres (.7 percent) of the area surveyed in 05, showing a significant decrease. Much of the decrease is likely the result of conversion to other cover types, particularly 9