International Dredging Review

International Dredging Review

Corps Restoring Lost Wildlife Habitat In Upper Mississippi River

Originally presented at the Western Dredging Association Midwest Chapter Meeting October 1 & 2 St. Paul Minnesota

By Don Powell St. Paul District U.S. Army Corps of Engineers

The Upper Mississippi River System consists of 1300 miles of waterways from Cairo Illinois to Minneapolis Minnesota. This multi-use river system supports navigation and recreation supplies drinking water and provides significant resource benefits for 500 species of fish and wildlife. Legislation in 1986 established the Environmental Management Program (EMP) for the purposes of restoring protecting and monitoring the natural resources of the system. The EMP is a partnership effort involving federal and state agencies and the public put into effect by the Corps of Engineers. It has become the most significant effort to restore and protect the natural resource values of the Upper Mississippi River.

The program includes construction of habitat projects that are designed to benefit fish and wildlife by restoring lost habitat or protecting existing habitat. Typical projects include one or more of the following features:
– islands to alter sediment transport reduce wave action and restore diversity;
– control structures on inlets to regulate flow and sediment input to the backwaters;
– water level management to simulate natural hydrologic cycles and to provide optimum growing conditions;
– stabilization of shorelines to reduce loss of terrestrial habitat or prevent an increase of sediment into backwaters; and
– backwater dredging to remove accumulated sediments and restore adequate depth for fish.

Since the creation of Pool 8 in the 1930’s about 80 percent of the island landmass in the pool had been lost to erosion. Aquatic plants and habitat diversity were also lost. The Pool 8 Islands project protects and restores islands and several miles of islands have been restored protecting more than 1500 acres of backwater.

The Polander Lake project combines habitat restoration with the channel maintenance program. Unloading a dredged material placement site provided 175000 cubic yards of material to construct islands in the 1000-acre backwater lake.

“Seed islands” are also being used. Small rock fill mounds — 200 feet long and two feet above water — are designed to modify flow velocities. They are placed in areas where sediment will settle out using natural river forces to build an island.

Erosion is occurring at many existing islands and side channel openings. Habitat projects stabilize the shorelines to protect terrestrial and backwater habitat.

Low dissolved oxygen levels in lakes downstream of Dam 4 were hampering fish productivity. A habitat project installed gated culverts through the dam to supply fresh water to the lakes.

Dredging in the Big Lake backwater area was done to restore fish habitat and the material was pumped to an unused channel maintenance placement site for re-vegetation.

Water level management can be used to restore or create habitat. This can be done on a small scale by diking off small areas to provide optimum water levels for the growth of vegetation for migratory birds or on a pool scale by modifying operation of the dams.

River managers have developed maps for Pools 1 through 11 showing desired future conditions. The pool plans will be used as a tool to formulate prioritize and select new habitat projects.

Illustrations: The completed Stoddard project in Pool 8. This 500-acrea area is Phase II of a five-phase island restoration project in Pool 8. In 1999 J.F. Brennan Company dredged sand into the traditional island area where the average water depth was three to four feet. Dikes were then bulldozed around the edges and fines pumped in. After drying through the winter the level was raised more and grasses planted. One local citizen watched the progress of the project and expressed gratitude that the area had been restored to the way it was 50 years ago when he was a child. Phase I is a 1000-acre restoration on the west side of the navigation channel.

The Stoddard Island project shown in its original state in 1964 at the start of the restoration in 1991 and a year after completion in 1999. Stoddard Wisconsin is in Pool 8 at river mile 687 10 miles downstream of LaCrosse. The pictures are oriented with north at the top. After the land mass was restored the native grasses and willows were planted which are thriving providing habitat for migrating waterfowl and other wildlife. Though the Corps doesn’t directly monitor the effects on fish the increase in people fishing in the area is a good indication that fish have also come back to the area.