Stormwater is the water that runs off the land following rains. It is the primary source of most of the water in our rivers and streams. As the water runs over and off the land, it can pick up or dissolve substances from the surface it runs over. As it runs over soil, it picks small particles of soil and can dissolve minerals, including nutrients, from that surface. Water running over the ground can also carry bacteria from the soil and manures laying on the soil. The faster and deeper the water runs, the more soil, nutrients, bacteria and other materials it can carry with it.
Natural ground surfaces have spongy organic matter coverings of old leaves, twigs and branches. They are covered with networks of roots just below the surface and plants above the surface in most non-desert environments. These materials soak up rain and help it percolate into the soil. Organic particles in the soil bind the minerals and clays into larger particles that reduce erosion. When man disturbs these systems, we often create situations that allow rainwater to run swiftly over the ground. When this happens, erosion increases, stream beds are filled and downhill flooding often follows. While some erosion is natural, out-of-control erosion is a threat to both water quality and public safety. Most of Louisiana is made up of downstream deposits of eroded soil.
Water running over the ground -- or stormwater -- is considered to be non-point water in that it comes from widespread sources and not point sources such as wastewater treatment plants. Addressing non-point or stormwater pollution can best be addressed by looking at the type of land use associated with or generating the runoff. We will look at four types of land use for grouping the ways to help minimize the problems.
A stream or other water body can accommodate a certain amount of any pollutant from all sources -- whether it is nutrient, bacteria, sediment, metals or other chemical -- and still retain its ability to perform its designated use as water for fishing, swimming, boating or drinking. The program to determine these limits for every stream is called the Total Maximum Daily Load (TMDL) program. To learn more about this program, see:
Agriculture—Cultivating the land for crop production disturbs the soil surface and can cause increased erosion. Improper or over use of fertilizer or pesticides can cause stream degradation and/or fish kills. Intensive production of animals for meat can generate problems from improper grazing and disposal of manures. For insight into how Louisiana agriculture is addressing these problems, see:
Forestry—While forests are long-term, stable environments, harvesting pulp and timber and the subsequent replanting disturb the soil and can create conditions for soil erosion and organic matter loss to streams. To see how the forest industry is acting to reduce these problems, see:
Urban Stormwater---Urban areas with their concentrations of people, vehicles, homes, parking lots, streets, small and large business, industry and sewage can create heavy loads of pollutants in their stormwater runoff. Most towns of more than 10,000 people now have a mandated Urban Stormwater Permit with mandated areas of responsibility to conduct programs in.
Homeowners play a very important role in the protection of urban stormwater since they control most of the land in an urban area. Their actions in and around their homes, lawns, gardens, driveways and vehicles can greatly affect the loads in the local stormwater. For more details on how to help protect your local waters, see:
Construction Stormwater -- Disturbing soil for the construction of streets, highways, parking lots, homes, subdivisions, shopping centers and commercial buildings can expose large areas of the soil surface to the rain and promote increased erosion. Any construction project that is part of any development plan larger than one acre is required to have a stormwater protection plan and to implement protective measures to reduce erosion. Local governments that have urban stormwater permits are required to enforce these federal and state regulations. To learn more about this program, see: