Tracking Runoff

Blizzards and frigid winds have people at home.  An indoors way to ease cabin fever tedium can be to identify where the deep snows will be going as warmer weather returns.

When snows melt and rains fall, street drains dump dirty runoff into nearby streams with no treatment.  Pollutants accumulate to form sediment bars in slow sections of streams, which can increase flooding and property damages during big storms.  Thousands of tons of sediment also pile up in water bodies, spurring weeds and toxic algae blooms that spoil swimming, fishing, boating and other recreation uses.

A main aim of federal and state stormwater regulations is to disconnect streets from streams.  Proposed EPA stormwater (MS4) permits will require towns to identify “Directly Connected Impervious Area” and track changes in DCIA.  Proposed rules also require permittees to report pollutant reductions attained through stormwater Best Management Practices (BMPs).

EPA Watershed IC mapEPA New England’s website has community maps and statistics showing DCIA, which can be downloaded at .  The DCIA maps and statistics can help identify the sources of runoff that harm specific streams and lakes.  Communities can also use DCIA data to:

  • Estimate pounds of pollutants dumped into local waters each year
  • Choose the best places and types of BMPs to capture polluted runoff

DCIA analysis can target runoff remedies to realize more clean water for less cost.  Street drainage areas that are not connected to local waters can be lower priorities, allowing attention to focus on storm drain systems with greater impacts.  For more details about tracking runoff and stormwater site selection, email:


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