Erosion & Sediment Control

Erosion and sedimentation are natural processes that take place in our environment every day. However, it can cause harmful effects to local water supplies and ecosystems if it occurs to an excessive degree. Construction, farming and timbering speed up natural erosion or create new sites for erosion by removing buffers and changing water flow patterns in an area. To mitigate a large part of the damage these practices cause, states and municipalities have created erosion and sediment control standards for contractors and operators to follow.

Significance

• Erosion is the wearing away of soil by water or wind. After soil has been worn away, it is washed away by runoff water and enters waterways. Lighter soil travels into larger or slower-moving bodies of water, while the heavier sediment is left behind. This process clouds the water and builds up the creek or stream floor. As the creeks and streams fill with sediment, the flow capacity of the stream is diminished, and the risk of flooding is increased. The sediment reduces the amount of light that aquatic plants can use for photosynthesis, spreads pollution and covers over breeding and feeding environments for fish and bottom dwellers. The effects of excessive erosion and sedimentation affect humans, plants and animals alike.

Effects

• In watershed areas for rivers and bays, such as the lower Mississippi River and the Chesapeake Bay, flooding and reduced water quality due to erosion can have serious impact. Maryland led the way to creating sediment control regulations, and other states followed. In 1972, the Clean Water Act established strong erosion and sediment control regulations to combat what it calls NSP, or non-point source pollution. NSP is a substance, such as erosion and sediment, that becomes a pollutant when carried off to another location.

Implementation

• Erosion control is not the same as sediment control. Erosion control is a set of practices that are put in place to prevent separation of the top layer of soil and keep it in place, preventing the development of sediment. Sediment control, by contrast, is a set of practices designed to trap any materials released through erosion and keep it from leaving the site or mixing with runoff and entering any bodies of water. Most land has an effective natural drainage pattern, so respecting that drainage pattern and using erosion control methods to work with it is usually better than changing the natural drainage pattern and installing sediment control. Sediment control is best used as a backup for an erosion control program.

Features

• Vegetation and trees help keep soil in place and prevent runoff by soaking up water. Natural land features such as rock outcroppings and inclines direct the flow of water. Natural mulch, such as leaves, pine bark or pinestraw, also retains soil. Silt fencing keeps sediment from washing into streets and stormdrains. Cloth laid over steep man-made slopes prevents rainwater runoff from washing dirt away from the slopes. Leaving plants in the fields during the winter and tilling them under in the spring prevents topsoil erosion.

Considerations

• Different municipalities have different requirements and procedures for handling erosion and sediment control. Some areas require a certain amount of undisturbed buffer alongside streams and creeks and the installation of silt fences along the edges of building lots on construction sites. Grading the land to drain into retention ponds instead of waterways to contain runoff is required by other areas. Timber cutters may be required to plant new trees in an area before moving on to another or to leave a certain number of trees. Most municipalities have some form of inspection process in place to ensure compliance with all local, state and national guidelines.