Flooding Information


90 percent of all natural disasters in California are flood-related. All rivers and creeks have floodplains that flood on a regular basis. This flooding is natural and serves a beneficial function. Unfortunately, floodplains have also been a prime area for development. As a result, many homes and other structures are currently in danger of flooding.

Floods in this area often occur with little or no warning; however, by being aware of your flood risk, you can prepare ahead of time to save lives and property.

For more information on flooding and flood risks, please visit the FloodSmart website. Additional information is also available from the California Department of Water Resources website on Flood Preparedness.

What causes flooding?

Floodwaters can cover many blocks to a depth of several feet. Flooding in our area can result from many different sources:

  • Backed-up creeks that overflow 
  • Drainage inlets/pipes may become blocked
  • Levees that break as a result of high tides, heavy rainfall, or rapid snowmelt
  • Heavy rainfall that overwhelms our storm drains or creeks
    • Please visit the "Documents and Standards" section of our Flood Control District webpage for guidelines on how to calculate the peak flow rates for a given watershed area using the Rational Method.

Flood Forecast Information

The Hydrology Section of the Flood Control Division and the Contra Costa County Flood Control and Water Conservation District collects and analyzes precipitation and runoff data. Visit the Flood Forecast Informationsection for such information on "live" rain gauge page, flood forecast tool, flash flood guidance, and weather links.

Flood Warning

If flooding occurs, the County will warn residents through radio, TV announcements, and emergency officials and vehicles. Please know the flood warning procedures and plan escapes to high ground.

The Office of Emergency Services has useful information, such as the Local Multi-Jurisdictional Local Hazard Mitigation Plan, Emergency Operations Plan, and Community Warning System.

Click here for the Flood Preparedness webpage.