The case studies demonstrate that the range of measures known as "pollution prevention" dramatically and cost-effectively reduce the quantity and concentration of pollutants winding up in stormwater. While the rain cannot be controlled, its stormwater impacts can, to a large degree, be managed. Management, planning, development design, or material substitution or reduction that incorporates stormwater pollution prevention before an activity takes place, are almost always the most effective and cost-effective means to reducing stormwater pollution. However, in already highly urbanized areas, such measures may not be possible. In such cases, several communities have found treatment of runoff with structural measures to be an effective alternative. Based on the study communities should focus on prevention-based approaches, through regional and watershed planning, local zoning ordinances, preservation of natural areas, stormwater-sensitive site design, widespread compliance with dumping and connection prohibitions, erosion prevention, and broad-based education as it is significantly more effective than treatment of polluted runoff.