History of Water Runoff Control
For the past two decades the rate of land development across the country has been more than two times greater than the rate of population growth. If left unchecked, the increase in impervious surface associated with this development will increase stormwater volume and degrade water quality, which can harm lakes, rivers, streams and coastal areas.
The stormwater pollution problem has two main components: the increased volume and rate of runoff from impervious surfaces and the concentration of pollutants in the runoff. Both components are directly related to development in urban and urbanizing areas. Together, these factors cause changes in hydrology and water quality that result in a variety of problems, including habitat modification and loss, increased flooding, decreased aquatic biological diversity, and increased sedimentation and erosion. Effective management of stormwater runoff offers a multitude of possible benefits, including protection of wetlands and aquatic ecosystems, improved quality of receiving waterbodies, conservation of water resources, protection of public health and flood mitigation.
In addition to chemical pollutants in stormwater, the physical aspects related to urban runoff, such as erosion and scour, can significantly affect a receiving water’s fish population and associated habitat. Alteration in hydraulic characteristics of streams receiving runoff include higher peak flow rates, increased frequency and duration of bankfull and subbankfull flows, increased occurrences of downstream flooding, and reduced baseflow levels. Traditional flood control measures that rely on the detention (storage) of the peak flow have been characteristic of many stormwater management approaches. They have generally not targeted pollutant reduction and in many cases have exacerbated the problems associated with changes in hydrology and hydraulics.
Increasing stormwater runoff levels also are negatively impacting aging and outdated storm sewer systems across the country, particularly in urban areas. Municipalities will either be forced to replace and update their sewer systems at enormous cost to their residents or manage their stormwater runoff in other ways.