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Title: Upper Mississippi River System Environmental Management Program Definite Project Report/Environmental Assessment (SP-19) : East Channel Habitat Rehabilitation and Enhancement Project, Pool 8, Upper Mississippi River, La Crosse County, Wisconsin and Winona County, Minnesota
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: The East Channel Habitat Rehabilitation and Enhancement Projects consists of a number of small projects located in the upper portion of pool 8 of the Upper Mississippi River. The study investigated habitat conditions and concerns at six locations in upper pool 8: Interstate 90 Bay, Head of East Channel, Lower Island 98, Minnesota Island, Smith Slough,·and French Slough. The habitat concerns at Interstate 90 Bay, Lower Island 98, and Minnesota Island are primarily related to bank erosion. At Interstate 90 Bay, erosion of a peninsula is threatening the existence of the bay and the habitat values it provides to the fishery resources of upper pool 8. At Lower Island 98 and Minnesota Island, erosion is resulting in the long term loss of island habitat that provides habitat diversity and ancillary benefits by maintaining the East Channel as a large side channel. The Head of East Channel provides high quality fish overwintering habitat. The concern was with sedimentation and maintaining fish access to this area. The concern at Smith Slough was with sedimentation and the ability of the slough to sustain itself as a running slough. Smith Slough provides a substantial amount of flow to French Slough. Habitat concerns identified for the upper portion of French Slough included localized dissolved oxygen depletion problems and a lack of bathymetric diversity. Much of this area is relatively shallow with a single deep area that exhibits stratification and anoxic conditions during the winter. The plan formulation process considered a number of alternatives for the habitat problems and opportunities at each of the study locations. At Interstate 90 Bay, the alternatives focused on stabilizing the eroding peninsula and restoring portions already lost. At Lower Island 98 and Minnesota Island the only options were no action or bank stabilization. At the Head of East Channel, a closure structure was evaluated as a method of reducing sedimentation, and dredging was evaluated as a measure to insure adequate fish access to this area. For Smith Slough, a number of measures were identified to either reduce sedimentation or increase water depths. Dredging was considered for the upper portion of French Slough to increase bathymetric diversity. No action was determined to be the best course of action for the Head of East Channel, Smith Slough, and French Slough. The sedimentation problem at the Head of East Channel does not appear significant because the natural closing off of the small side channel at the head of this area. Fish access to the Head of East Channel appears adequate at present. The situation will need monitoring by resource management agencies to determine if fish access to this area is self maintaining or deteriorating. Dredging in Smith Slough would be costly and not a permanent solution to maintaining the slough. Constructing low level berms (to maintain more high flow in the slough) would have unacceptable impacts on riparian habitats and adjacent wetlands. Controlling sediment inputs to Smith Slough would be difficult, and would reduce flows, which in turn could further aggravate sedimentation in the slough. As with the Head of East Channel, resource management agencies will monitor conditions in Smith Slough to determine if the recent sedimentation is a reflection of the natural pattern of sedimentation and scour that occurs in riverine settings. A culvert was installed in the lock and dam 7 dike in 1994 to provide additional flow to the upper portion of French Slough. It is determined that no further action should take place in this area until the effects of this added flow on the slough can be evaluated. The recommended plan for the Interstate 90 Bay is to stabilize the peninsula using rock bank protection and restore a portion of the peninsula lost to erosion using a rock breakwater. The Interstate 90 Bay has been identified by the Wisconsin Department of Natural Resources as a staging area for spawning walleye and as important habitat for young-of-the-year walleye and sauger. Other studies have identified the importance of this type of habitat many species of fish. Maintaining and restoring a portion of the bay will provide substantial benefit to the fishery resources of upper pool 8. The recommended plan for Lower Island 98 and Minnesota Island is to stabilize these islands using rock bank protection. Both of these islands are "high" islands when compared to most Mississippi River floodplain islands. They support mast producing trees such as oaks and other vegetation more typical of drier sites. As such, they increase habitat diversity in this portion of upper pool 8. In addition, these island help define the East Channel which provides its own unique habitat values to the area. Stabilizing these islands is considered important to maintaining habitat diversity in upper pool 8.
Description: Definite Project Report with Integrated Environmental Assessment
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Environmental Documents

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