Flood Forecast Tools

The Flood Control District is continually looking for ways to provide information to help the citizens make decisions during storms and potential flooding conditions. We now obtain detailed forecast data from the National Weather Service Advance Quantitative Precipitation Information (AQPI) system on an hourly basis. We then process this data and provide it via links on our RainMap. Go to our RainMap and find the following links:

You will also see the following links that have information based on our own rain gauges and the AQPI forecast data.

These tools can be used with the 7-5-3-2 protocols to assess the likelihood of flooding.

On occasion, the AQPI data will be incomplete and our tools may not show the full forecast. We view these tools frequently and make adjustments as soon as possible. We have no control over the AQPI forecast data we receive, though we can contact them when we notice problems.

Contra Costa Rain Gauges Spreadsheet

CCGauges spreadsheet.xls (Download 0.54 MB)
This spreadsheet reference the Flood Control District Rain gauge RainTable. It does not include the locations used in the above mentioned QPF Tool for General Locations to show the 2-hour forecast. This spreadsheet is simpler and lighter. It does calculate the Year to Date (YTD) percent normal rainfall for the county rain gauge locations.

When to consider taking action.

Contra Costa County is susceptible to flash flooding. If you live in a flood prone area, you should have a personal evacuation plan and keep an eye on the weather and the antecedent conditions.

As the storm progresses, the following approximate trigger intensities historically have produced local flooding:


1.00" in a 2-hour period, 0.70" or more in a 1-hour period 


0.60 to 0.70 in a 2-hour period, or 0.40" or more in a 1-hour period.

See instructions on accessing the National Weather Service web sites below. You should review your personal evacuation plan and take precautions to protect personal property if you sense flooding may occur. 

Other Factors

In addition to antecedent rainfall conditions, several other factors can also contribute to flooding. These factors include
  • debris blockage of drainage infrastructure and
  • sudden localized downpours that are not detected by rain gauges.
This antecedent conditions information should be used in conjunction with small stream advisory warnings broadcast/posted by the National Weather Service as well as common sense.

The Contra Costa County Flood Control & Water Conservation District (FC District) is not responsible for predicting flooding, warning property owners of eminent flooding, or ordering evacuations. The above information is presented to provide an indication of potential for flooding based on experience and review of limited historic rainfall data. The FC District does not warranty, guarantee, or certify the accuracy of the rainfall data. The data accuracy and availability can be compromised due to equipment failure, power loss, equipment defects, loss of calibration, or Internet/radio communication equipment failure of equipment provided by others.