Established natural drainage features have evolved to take care of existing runoff from wet weather events.  Natural features have evolved over time to handle storm water runoff at a given location.  Altering the terrain may reduce the effectiveness of these features and may also require introduction of new, artificial means of addressing stormwater management.
	If additional runoff volume is expected after development, natural features should be supplemented or enhanced to handle the additional flow.  For example, a detention or retention basin with a created wetland may augment existing surface water features.