A. Natural drainage features, particularly vegetated drainage swales and channels, shall be protected because of their ability to infiltrate and attenuate flows and to filter pollutants. Runoff and pollutants generated from impervious surfaces shall not flow directly into storm sewers with no opportunity for attenuation, infiltration or filtration. Developments shall be designed to fit site topography and minimize the amount of grading on site.
B. Depressional storage areas have no surface outlet or drain very slowly following a storm event. They can be commonly seen as ponded areas in farm fields during the wet season or after large runoff events. The volume and release-rate characteristics of depressions should be protected in the design of the development site. The depressions shall be protected by simply avoiding the depression or by incorporating its storage as additional capacity in required detention facilities.