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Mapping Resources

The following is a selection of resources for those seeking more information on MS4-related mapping requirements.

Links to resources outside of DEP's website do not necessarily constitute an endorsement.


  • eMapPA
    This DEP application can be used to view urbanized areas (UAs) based on the 2000 and 2010 censuses along with other facilities and features. Note that use of the web-based GIS application may be more appropriate for Pollutant Reduction Plans because it does not include 2016 tentative stream impairments, which are not required to be addressed in the 2018-2023 permit term.
  • Model Map (PDF)
    An example map developed by DEP that illustrates the detail necessary to meet the basic requirements of MCM #3 as well as the advanced requirements for Pollutant Reduction Plans, TMDL Plans and Pollutant Control Measures for the forthcoming NPDES permit term. DEP has posted instructions (PDF) on how to use the Model Map.

Mapping Tools

  • EPA National Stormwater Calculator
    This calculator may be used to compute small site hydrology for any location within the US by estimating the amount of stormwater runoff generated from a site under different development and control scenarios over a long term period of historical rainfall.
  • EPA Stormwater Management Model
    A dynamic rainfall-runoff simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas.