Drainage System / NPDES


20x20 Watershed Boundary

Watershed Boundary

20x20 NPDES Boundary

National Discharge Elimination System (NPDES) Boundary

20x20 FEMA Flood Zone

Flood Zone, designated by the Federal Emergency Management Administration (FEMA)

20x20 Drainage Inspection

Drainage Site Inspection

20x20 NPDES Outfall

Drainage System Outfall

20x20 Inlet 2

Drop Inlet or Catch Basin

20x20 Man Hole (2)

Man Hole, Junction Box, or Other Drainage System Access Point

20x20 Stream

Creek, River, or Naturally-Occurring Stream

20x20 NPDES Open Channel

Ditch or Other Open Channel

20x20 NPDES Closed Conduit

Below-Ground Drainage Conduit

Alternate Views of the Map

Map Information

The above map displays municipal storm drainage systems that fall within the NPDES priority mapping boundaries, as well as related features, such as streams, conduits, inlets, outfalls, and water quality testing points.


The National Pollutant Discharge Elimination System (NPDES) refers to the network of municipal storm drainage systems that carry storm water away from our streets and into local streams. State and Federal laws require that local municipalities map these systems, such that pollutants detected in local streams can be traced to potential sources. The pink shaded areas represent the regions where NPDES mapping is required.

This map is intended to show the destination of storm water. Mapping is not complete in all areas and may contain inaccuracies. This information should never be used to make parcel-specific decisions or replace a field survey. Also note that the County only maps areas that are within its jurisdiction.

GIS Data

The data layers used on this map can be downloaded and imported into various GIS applications. Data files are in compressed ("zipped") shapefile format.

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Contact Information

Business Hours
Monday – Friday
8:00 AM – 5:00 PM
Contact us by Phone
Office Location
La Plaza B
2300 County Center Drive
Suite B 100
Santa Rosa, CA 95403
38.462023, -122.725381

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