Yard clippings and leaves can wash into storm drains and contribute nutrients and organic matter to streams.  Grass clippings, leaves, and yard trimmings that are recycled or composted are a free source of nutrients for your yard, supplying not only carbon and nitrogen, but they also shade the soil and reduce the need for water.  To learn more about proper disposal of yard waste view the Piedmont Triad Yardstick Workbook (pdf). Water pollution problems from yard waste can be diminished by following these guidelines: Never rake or blow leaves and other debris into the street or storm drains Compost or mulch yard waste Cover piles of dirt or mulch being used in landscaping projects