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Title: Upper Mississippi River System Environmental Management Program Definite Project Report/Environmental Assessment (SP-9) : Lansing Big Lake Habitat Rehabilitation and Enhancement Project, Pool 9, Upper Mississippi River, Allamakee County, Iowa
Authors: United States. Army. Corps of Engineers. St. Paul District.
Keywords: Restoration ecology
Environmental protection
Environmental management
Mississippi River
Publisher: United States. Army. Corps of Engineers. St. Paul District.
Abstract: This study concentrates on 9,755 acres of backwaters, known as Lansing Big Lake, located in pool 9 of the Upper Mississippi River between river miles 664 and 670. The Lansing Big Lake area provides valuable and highly productive habitat for wildlife, including waterfowl, wading birds, muskrats, eagles, and a variety of fish. This backwater area is especially critical as a resting and feeding area during migration for diving ducks, tundra swans, Canada geese, and other waterfowl. Since inundation in the 1930's, there ts documented evidence that sediment has filled in aquatic habitat in the Lansing Big lake backwater area which has resulted in a dramatic loss of important aquatic habitat and an increase in less valuable marsh and bottomland forest habitat. It is projected that if historical habitat conversion rates continue, by the year 2040, existing aquatic habitat in the Big Lake area will decline by over 35%. However, there is evidence that the side channel openings which allow sediments to enter the backwaters are now eroding at a rapid rate which is allowing increasing amounts of sediment to enter and be deposited in the backwaters. The accumulative loss in aquatic habitat in the Lansing Big Lake area is a serious threat to fish and wildlife. In order to meet the overall goal of preserving and enhancing the existing aquatic habitat in the Lansing Big Lake area, it was determined that remedial actions should be taken to reduce the rate of backwater sedimentation. The plan formulation process considered a number of possible measures and then evaluated in detail 5 alternative plans for reducing sediment inflows to the project area. These alternatives presented an array of plans for reducing and stabilizing backwater inflows and evaluated the outputs and environmental effects of each plan. The selected plan, alternative 15, was found to best meet the project goal and objectives with miniminal adverse environmental effects. Construction of the selected plan would effectively return the Big Lake backwater inflow capacity to a pre-1980 condition and prevent further future side channel erosion. The selected plan reduces the sediments that are allowed to enter the Lansing Big Lake area by constructing side channel closures at 7 existing side channel openings and by stabilizing 3 side channels with rock liners. These structures are designed to restrict the inflows of sediment laden waters to the Lansing Big lake backwaters up to an 80,000 cfs discharge on the Mississippi River which is equivalent to a 66% annual discharge frequency. By Implementing the selected plan, 150 acres of critical aquatic habitat in the Lansing Big Lake area will be preserved during the project life (through year 2040). Beyond the project life, additional positive outputs of the project will also result. Specifically, at the end of the project life, the remaining aquatic habitat ln Lansing Big Lake would be deeper. In addition to this, the sedimentation rate into the future years beyond 2040 would be substantially reduced as compared to the without project condition. This would result in project outputs benefiting fish and wildlife well beyond the year 2040.
Description: Definite Project Report with Integrated Environmental Assessment
Rights: Approved for Public Release; Distribution is Unlimited
Size: 167 pages / 7.05 MB
Types of Materials: PDF/A
Appears in Collections:Environmental Documents

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