It is critical that stormwater runoff (SWRO) be managed properly if we are to have water quality suitable for human consumption, fish production, recreational uses, and plant and animal habitats. As more undeveloped areas are developed, the natural arresting factors we have had for SWRO control are diminished. Flattening the topography of the land and paving surfaces causes SWRO velocities to increase. Also, as pockets and depressions in the earth's surface, as well as steep cliffs are removed, SWRO velocities are increased. As the velocity increases, the erosive power of the SWRO becomes greater. Carried away with the runoff then from this accelerated SWRO are suspended solids and other pollutants which negatively impact water quality.
Also, prior to development of land parcels, the tree canopies and forest undergrowth slowed the rainfall's velocity, as did the other features previously noted. This then allowed the rainfall to infiltrate the earth's surface where solids and pollutants were removed and the ground water levels were recharged. But removal of trees and vegetation takes away a natural habitat's ability to slow SWRO. This SWRO slowing occurs naturally as plants provided surfaces for water to accumulate and then evaporate as well as to be absorbed by plant root systems. Following root absorption, the water is returned to the atmosphere by transpiration.
Without these naturally occurring features, the SWRO flow to receiving waters such as streams, lakes, and the oceans is increased and the SWRO flow to the ground area where the rainfall occurred is diminished. Both surface waters and ground waters then are negatively impacted. Since about 50% of the U.S. population relies upon surface water for drinking and other potable uses, and 50% relies upon groundwater, it is imperative that SWRO be managed properly to positively impact all drinking water supplies.
There are three primary means of reducing the quantity and improving the quality of SWRO. The first choice should be to reduce or eliminate the SWRO at its source. If either the pollutants can be eliminated or their effects sufficiently minimized, then SWRO is not a problem from pollution runoff bit it may still be a problem due to the erosive nature of the runoff. When preventive measures cannot achieve the desired source reduction or maintain water quality in the SWRO, then the second set of strategies should be employed. These generally seek to increase the amount of pervious soil to enhance water infiltration thus reducing both the quantity of SWRO and the pollutant load being carried offsite. Finally, when the first two control strategies are not sufficient to control SWRO, best management practices designed to contain the SWRO and subsequently either remove the pollutants and sediment or allow the SWRO to infiltrate the ground must be employed. This paper addresses the last of the three strategies - best management practices (BMP's).
