Truly effective stormwater control takes a systems approach, using a combination of preventive and management techniques that work together to minimize impact.
In undisturbed landscapes, rainwater runoff is part of the natural hydrologic cycle. Vegetation, soils, and a wide range of organisms filter, absorb, and use rainfall in their living processes. Evaporation and transpiration takes place. Excess precipitation infiltrates into groundwater and flows into surface waters, recharging aquifers and supporting aquatic life. The entire system is affected when the landscape is changed: impervious surfaces (paved streets, parking lots, rooftops, etc.) prevent runoff from percolating into the ground and cause it to pick up debris, sediments, chemicals, and other pollutants as it moves over the ground.
A Systems Approach
The NPDES Phase II rule, discussed in detail here, encourages a systems approach by defining the general requirements for how MS4s, industrial facilities, and developers should integrate stormwater management into their operations.