ABSTRACT
The main purpose of treating stormwater is to reduce its adverse impacts on the beneficial uses of receiving waters. Therefore, it is important in any urban stormwater study to assess the detrimental effects that runoff is actually having on a receiving water. Urban receiving waters may have many beneficial-use goals, including:
• stormwater conveyance (flood prevention) • biological uses (warm water fishery, biological integrity, etc.) • noncontact recreation (linear parks, aesthetics, boating, etc.) • contact recreation (swimming) • water supply
Two joint research projects recently funded by the U.S. Environmental Protection Agency (EPA
) examined the historical development of stormwater management programs and modifications that should be incorporated into future design procedures. The projects found that, with full development in an urban watershed and with no stormwater controls, it is unlikely that any of the above listed uses can be fully obtained. With less development and with the application of stormwater controls, some uses may be possible. It is important that unreasonable expectations not be placed on urban waters, as the cost to obtain these uses may be prohibitive. With full-scale development and lack of adequate stormwater controls, severely degraded streams will be common. However, stormwater conveyance and aesthetics should be the basic beneficial-use goals for all urban waters. Biological integrity should also be a goal, but with the realization that the natural stream ecosystem will be severely modified with urbanization. Certain basic controls, installed at the time of development, plus protection of stream habitat, may enable partial use of some of these basic goals in urbanized watersheds. Careful planning and optimal utilization of stormwater controls are necessary to achieve these basic goals in most watersheds. Water contact recreation, consumptive fisheries, and water supplies are not appropriate goals for most urbanized watersheds. However, these higher uses may be possible in urban areas where the receiving waters are large and drain mostly undeveloped areas.
