Drainage Area Maps

Drainage Areas
Almost every watershed in Contra Costa County has been identified with a number. We call these Drainage Areas. Drainage Areas are formed to collect fees from developers to pay for planned drainage infrastructure including detention basins, pipes, channels, and related costs. An unformed drainage area is a watershed that has been identified, but does not have development fees.

County Zones and Drainage Areas (PDF)

Drainage Area Maps
Copies of Drainage Area Maps are available by calling (925) 313-2000 and asking for the Flood Control Counter Duty person or by email. An electronic copy will be emailed.

  • The Drainage Area Boundary Map shows the legally described area for the DA Parcels within that Boundary. 
  • The Drainage Area Land Use (LU) Map shows the land use assumptions used in the hydrology calculations for the Drainage Area. The LU Map is based on General Plan at time of calculations.
  • The Drainage Area Hydrology Map shows the watershed and sub-watershed boundaries and assumed direction of drainage.
  • The Drainage Area Plan shows the proposed improvements to be funded by the drainage area, typically storm drain pipes and detention basins. The Hydrology Map and Plan maps are sometimes combined.