UPPER MISSISSIPPI RIVER - POOL 15
DRAFT POOL PLAN
Description of Pool 15:
Pool 15, the shortest impoundment in the Rock Island District, is the approximate 10.2 mile segment of the Mississippi River extending upstream from Lock and dam 15 in Rock Island, Illinois, to Lock and Dam 14 near LeClaire, Iowa. Bordered by the states of Iowa and Illinois, pool 15 includes ___ acres of public lands and waters. Although the project area is Pool 15, planning considerations extend to areas which impact pool resources, including watersheds, natural floodplains behind levees, and private lands within the pool.
Based on 1989 aerial photography, the Upper Mississippi River Environmental Program Habitat Needs Assessment (HNA) calculated acres in 18 land cover classes, including open water for this pool. Pool 15 is typified by the Fulton-Rock Island gorge of geomorphic reach 5, constricted, devoid of islands, and with habitat limited to main channel characters. For this reason, and because the pool is almost entirely industrial and urbanized, it encompasses little of the natural floodplain. Pool 15 inundates the Rock Island Rapids section of the river and contains Steamboat Era river regulating structures that may contribute to this Pools habitat value to fish and mussels. Tributaries to this Pool are Duck Creek, Crow Creek and Spencer Creek with drainage areas of 64.5, 18.8, and 19.7 square miles respectively. One Illinois tributary, Sugar Creek enters the pool with a drainage area of 6.1 square miles.
Features of this pool include its predominant rock substrate, a large mussel bed within the old steamboat channel, the presence of the Federally endangered Higgins’eye pearly mussel at the lower end of this bed, and the designation of Sylvan Slough, including the tailwater section, as a State of Illinois Mussel Sanctuary. In addition, where sediment has accreted in the lower third of the pool, conditions have been favorable for establishment and maintenance of important aquatic plants such as coontail, wildcelery, and sago pondweed. These plants have mostly disappeared below Pool 15. Beds of American lotus and arrowhead are found in the side channels of Campbell’s and Arsenal Islands.Public lands and waters within Pool 15 are limited to various parks and campgrounds
Resource Problems and Issues:
1. Fine sediments are accumulating at accelerated rates within backwaters and other floodplain sites due to high suspended sediment concentrations and the reduced sediment transport capability of the navigation project. High turbidity prevents colonization of aquatic plants. Primary concerns within Pool 15 are Campbell’s Island side channel and Sylvan Island side channel sedimentation.
2. Submergent aquatic vegetation has disappeared throughout the pool, although lotus and arrowhead have rebounded from the flood of 1993. Grazing, biomechanical disturbance, and water level fluctuation are suspected to be primary limiting factors, and limit the ability to maintain habitats critical to migratory birds must be maintained, especially aquatic food resources and woodlands. Examples of this may be found throughout the Pool.
3. Locks and Dams 14 and 15 restrain fish passage between pools.
4. Nuisance aquatic species such as grass carp, bighead carp, zebra mussels, and Eurasian milfoil are present. In addition, Reed’s canary grass and purple loosestrife are present and could become dominant in the absence of active control or eradication.
5. Industrial discharges into Pool 15 contribute to water quality and habitat problems which impact natural resources.
6. The current status of Pool 15 mussel community is unknown. More information is needed to better assess and manage Pool 15 mussel populations.
7. The current water management regime, especially the avoidance of seasonal low water, removes much potential for periodic regeneration of aquatic habitats. Also, rapid water level fluctuations affect life history cycles of fish throughout the year, but particularly during the spawning season.
8. After inundation, expanse areas of rapids & rock habitats where lost. These habitats support a very diverse community of macroinvertebrates and _______ fish.
1. Design and construction of projects to utilize the river’s hydraulic energy to open or maintain side channels can be accomplished to mitigate Resource Problem #1. Opportunities to maintain existing or improve degraded side channels include (a) erosion protection of key side channel shorelines, (b) experimental structures designed to alter flow and increase bathymetric diversity within side channels, (c) flow regulation into degraded side channels and (d) development of bathymetric and sediment transport models for Pool 15 to aid analysis and project design. Dredging can also restore side channel productivity, and is especially appropriate when used in combination with techniques which sustain the desired condition
2. Pool management, which effectively maintains emergent and submersed aquatic vegetation and forests, will insure availability of habitats critical to migratory birds (Resource Problem #2). Vegetation provides direct habitat benefits and positively influences other important resources, such as aquatic macroinvertebrates and fishes. Opportunities to restore or maintain aquatic vegetation include: (a) island maintenance or development to shelter aquatic areas, (b) water level management, especially to provide periodic low water elevations, and (c) actions within watersheds and the pool to lower turbidity and sedimentation rates, and (d) maintain critical backwater habitat units at select locations.
3. Appropriate operation changes at Locks and Dams 14 and 15 or their structures can improve fish passage (Resource Problem #3). Opportunitiies include the design and construction of ladders or amending lock or dam operation.
5. Watershed related water quality issues are addresses by several authorities, but river managers can influence effectiveness of local programs (Resource Problem #5). Opportunities to improve watershed impacts can include (a) collaborative efforts to reduce upland soil erosion, (b) improvements to lower tributary characters including floodplain restoration, (c) supporting efforts to solve specific water quality problems, such as industrial discharges, and (d) initiation of needed monitoring if information is not available.
6. A mussel inventory is needed to provide basic information on Pool 15 mussels (Resource Problem 6). Opportunities include (a) a collaborative inventory involving all agencies or (b) a contracted study funded by an applicable authority.
7. Timely water level fluctuation, planned within the constraints of the navigation system, can induce biological responses which rejuvenate aquatic habitats (Resource Problem #7). Opportunities include periodic reduced summer water elevation designed to mimic natural summer low flow events. Backwater areas in Pool 15 from the mid-Pool to the dam would benefit from periodic drying and sediment consolidation.[KM1]
8. Mitigation for lost ‘rapids’ habitat could be obtained from widening the rock wall at ________ (Resource Problem #8).
To facilitate planning and illustration, proposed projects are organized within geographical units. Geographical unit boundaries and the sites of Proposed Projects within Pool 15 may be located on the Desired Future Habitat Conditions maps, which follow this section.
Upper Pool 15:
Monitor habitat, flow and bathymetric characters in Sylvan Slough and select management objectives to maintain selected features. In the main channel construction or modification of various training structures will be used to maintain or improve fishery value.
Expand fish passage opportunity through Lock and Dam 15. The Arsenal Power Dam and the MidAmerican power dam.
Pool 15 Entire:
Complete bank stabilization or flow modifications at sites where rapid bank line erosion threatens pool diversity. The project should begin with a pool-wide inventory.
Review Pool 15 water management and determine feasibility, impacts and anticipated results of potential changes in water management, especially the partial restoration of seasonal low water elevations.
Inventory and assess mussel populations throughout the pool and design appropriate habitat management.
Pool 15 Watershed:
Use existing programs and incentives offered by federal, state, and county agencies and private groups to reduce the contribution of sediment from tributaries.
Request appropriate water quality authorities for assessment of urban and industrial discharges. Develop cooperative programs to resolve any problems for river resources.
Upper Mississippi River System:
Develop pool-wide environmental planning aids, including hydraulic models, topographic and bathymetric surveys, substrate maps and other information needed to facilitate engineered solutions for habitat diversity.
Design, construct and test structures to maintain or restore desired habitat features.
Expected or Desired Results:
1. A combination of engineered solutions, applied to select sites, will aid in the restoration and maintenance of important habitat features of side channels and backwaters impacted by accelerated sedimentation. Sediment accumulation attributed to the navigation project can be reduced at project sites to maintain or restore important habitat values. Aquatic values and the life span of targeted backwaters will be extended. Fish over-wintering habitats will be maintained within five-mile intervals. Side channels targeted for improved management of coarse sediments may be maintained indefinitely. Main channel training structures, however, will preclude much potential for large-scale regeneration of aquatic habitats, and the long-term trend to a less diverse system will continue.
2. Habitats critical to migratory birds, especially aquatic food resources and forests, will be extended and improved if the problems of suspended sediments and sustained high water elevations can be mitigated. Water management alternatives, even in small scale, promise important, periodic rejuvenation of aquatic vegetation.
3. Expected or desired results related to problems associated with the accumulation of coarse sediments are included in number 1 above.
4. Diverse forest communities can be developed on sites significantly elevated above the water table or they can be maintained on higher areas of the floodplain with careful management and intensive regeneration efforts. Sediment accumulation will slowly improve the woodland site index at some locations. There may be opportunities for forest restoration on lands currently in agricultural production within levee and drainage districts. Forest stand improvement goals will be established throughout the Pool.
5. Long-term improvement in watershed management and best management practices are expected to reduce sediment loads from immediate watersheds and the basin. River managers must ensure that river impacts are a measured cost of upland erosion and that Mississippi River natural resource and water quality issues are represented in planning and implementation of agricultural, urban and industrial watershed management. However, improving soil and water management on private lands throughout the basin is a complicated task and a decades old effort that will not soon be resolved. Accelerated sediment delivery will remain a problem.
6. The installation of fish passage structures or amended lock and dam operation may improve opportunity for fish movement between pools
7. Mussel populations and habitat will be monitored and best management guidelines will be established and implemented.
8. Expanding the vertical dimension of water level fluctuation via periodic summer draw-down will promote productivity of aquatic communities and improve fish and wildlife habitats and populations. A minimum 10-year draw-down cycle will be implemented.
Mitigate for rapids habitat - widen rock wall