Before Settlement

Settlement & Industry

Channelization

Flooding

Human Impact

Current Management

Bibliography

Human Impact

Pollution ~ Sedimentation

Sedimentation is the largest pollutant of the river because of soil erosion from farmland, such as the farmland pictured to the left.   Row and small grain cropland is losing soil into the river faster than it can be replaced. Erosion from riverbanks and fragile bluffs contributes to 1/3 of the sedimentation into the river. Logged areas and construction site damages add to the already polluted waters (McKnight 44).

Some statistics on soil erosion are as follows:

50% of the region's crops are eroding faster than they can be replaced
88 million tons wash off the land each year
23% of the row and small grain cropland are using techniques to prevent erosion(McKnight 52)
5% to 9% water lost to sedimentation
22 to 49% estimated to be lost in the next 50 years
900,000 cubic yards (150 football fields piled three feet deep) of sediment dredged annually to maintain navigation between Rock Island and St. Paul

Problems Sediment Causes in the River

-Makes water murky, blocking light that aquatic plants need to grow
-Covers plants and animals
-Fills in backwaters, pools, and other areas where fish and wildlife congregate
-Pollutants such as heavy metals and nutrients attach to the sediment and contaminate the river bottom where they settle (McKnight 45).

Increased navigation on the Mississippi River has lead to problems with sedimentation in the water. When  the channels were placed on the river, they caused a decrease in the width of the river.  Wing dams helped increase the speed of the water, which allowed the river to carry more sediment. However,  in the places where the water was calm, the sediment settled to the bottom. Thus, between and behind wing dams, sand and plants began to fill the space in between, causing the river’s banks to move inward (Anfinson 7).

According to the Upper Mississippi River Conservation Committee (UMRCC) website, "unless current sedimentation rates in UMR backwaters are reduced many wetland and aquatic habitats will be converted to less-desirable upland habitat types in the next few decades." The UMRCC have created an Environmental Management Program (EMP) to deal with this problem. U.S. fish and wildlife along with the Army Corp of Engineers and the five states in the Upper Mississippi River Valley (Minnesota, Wisconsin, Illinois, Iowa, and Missouri) will collect sediment data and try to find management alternatives to restore backwater wetlands.