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Erosion and Sedimentation
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Erosion and Sedimentation

Erosion is the wearing away of soil by water, wind, and other forces. Any disturbance of natural terrain, vegetation, or the pathway taken by stormwater runoff may result in erosion. Soil erosion caused by human activity is a significant source of sediment and pollutants entering Long Island Sound.

When farmers clear land to grow cultivated crops or when livestock overgraze pasture, soil is subject to erosion because removal of the protecting plant cover allows the soil to wash away. The result can be a decrease in productivity of the land. When logging roads and skid trails are poorly designed or located, sediment from increased erosion pollutes streams and erosion delays regrowth of the forest.

Streambanks in already-developed areas are especially subject to erosion by forceful runoff. Rain striking hard surfaces like pavement runs off rapidly rather than soaking into the ground. On reaching streambanks, it flows over the edges forcibly enough to wear away the soil.

Erosion is especially noticeable when land is bulldozed for development without control of runoff and erosion. We've all seen muddy water filling gutters near a construction site. The resulting flooding can damage property and pollute waterways. When it reaches natural waters, runoff from development sites can destroy wetlands, smother aquatic life, and dirty the water.

Eroded sediment can remain suspended in streams and reservoirs for a while, blocking out sunlight and reducing biological activity. Once it settles to the bottom, sediment reduces the capacity to hold flood flows. As a result, flooding is more likely to occur, and the damage it causes will be worse.

Long-term accumulations of sediment become a serious problem for shallow coastal regions and embayments. Sediment can destroy fish spawning areas and choke out marine life essential to the food web of the Sound.

Many difficult questions remain about the management of contaminated sediments, especially where they have become contaminated with heavy metals, pesticides, and other pollutants. To what extent do the pollutants trapped in sediments reenter the water column and reach fish and shellfish? Should polluted sediments be dredged up or is it safer to leave them undisturbed?

There is little doubt, however, that preventing soil erosion and sedimentation is more effective and cheaper by far than curing it once it has occurred. Most erosion problems can be controlled economically by methods available right now. If you are a farmer with an erosion problem, contact your conservation district or local U.S. Dept. of Agriculture Soil Conservation Service Office to get technical help with conservation practices.

If you are a concerned citizen, keep your eyes on the land in your backyard and in your community. The most critical erosion danger is from improper controls at development sites. While most states in the watershed have laws to deal with this problem, monitoring and enforcement are often inadequate. If you notice an erosion problem, consult your local conservation commission or wetlands commission to find out what is being done or can be done about it. Alert citizens' action groups if public attention is needed. Some suggestions for what you can do to prevent erosion in your own backyard are given later in The Soundbook.

Soundkeeper, Inc.