SonomaCountyRecovers: Official recovery information for Sonoma County fires

Rainfall and Stream Gauges Provide Early Flood Monitoring System for Flash Floods and Debris Flows in Burn Areas

Posted on April 5, 2018


 

Press ReleaseSANTA ROSA – A series of rain and stream flow gauges have been installed within and downstream of the areas burned by the devastating October wildfires, providing real-time data to weather forecasters who are responsible for sending out alerts to residents when flashfloods or debris flows may be imminent. The gauge installations enhance Sonoma County’s ability to monitor for potential dangers during rain storms and trigger advanced warnings based on better thresholds.

A system of 10 stream/rain gauges and 12 rain-only gauges were installed in locations throughout the Nuns and Tubbs fires burn areas, and along streams within and downstream of the burn areas. The data from the gauges is used by the National Weather Service (NWS) in developing their hazardous weather advisories, alerts and warnings. The real-time rainfall and streamflow data is also available to the public at https://sonoma.onerain.com/.

“The benefit of the expanded rain and stream gauge network is situational awareness,” said Brian Garcia, Warning Coordination Meteorologist with the National Weather Service. “Knowing what is going on in real time is vitally important to the issuance of life-saving warnings, such as flash flood warnings. During rain storms we continually monitor the network of instrumentation across Sonoma County to maintain situational awareness.”

Many properties in the areas in the areas burned by the wildfires, and downstream of those areas, are at risk for flash flooding, mudflows and debris flows during periods of intense rainfall. Wildfires can dramatically alter the terrain and soil conditions and leave the ground unable to absorb water, creating ideal conditions for flash flooding and mudflows.

City and County officials are working collaboratively on numerous fire recovery fronts, including efforts to protect the watershed and communicate with residents in the burn areas about the importance of signing up for alerts and remaining vigilant about weather conditions. The new rain and stream gauge system and website was installed by the Sonoma County Water Agency as part of an early warning system for flooding, and to improve its overall flood control capabilities.

“This system of gauges allows us to monitor streams and rainfall in real-time and gives us a more accurate picture of conditions in the burn areas and downstream in areas that are vulnerable to flooding,” said Jay Jasperse, Sonoma County Water Agency Chief Engineer. “We can also start to gather historical flow data along more streams, which is critical for our stream maintenance and flood control operations.”

In addition to the new https://sonoma.onerain.com/ website, county and city officials have mailed a second postcard to property owners and residents living in or near the fire burn areas. The postcards include brief descriptions of how to be prepared for flash floods and mudflows, and how to stay informed about potential emergency events. More information about being prepared, including a map identifying post-fire hazard assessments, is available at www.sonomacountyrecovers.org

A multi-agency analysis was used to create post-fire hazard assessment maps, which identified the locations within the burn areas that are at risk for flash floods, mudflows and debris flows:

  • Flash floods are a rapid flooding of a low-lying area in less than six hours, which can be caused by intense rainfall. Flash floods are known to roll boulders, tear out trees and destroy buildings and bridges.
  • Mudflows are rivers of liquid and flowing mud on the surface of normally dry land, often caused by a combination of vegetation loss and subsequent heavy rains. They can cause significant damage.
  • Debris flows are a moving mass of mud, sand, soil, rock and water. They can travel very quickly, and can be very powerful and destructive.

Residents are encouraged to be prepared at all times:

    • Keep your cell phone turned on at all times to receive Emergency Alerts and Warnings from the NWS. For information on NWS Advisories and Watches visit: weather.gov/alerts.
    • To be notified by Sonoma County first responders in the event of an emergency, sign up for Sonoma County Alerts at: SoCoAlert.com.
    • The Sonoma County Sheriff’s Department rebroadcasts NWS advisories, alerts and warnings. To receive alerts from the Sheriff’s Dept. and other public safety agencies visit: local.nixle.com/sonoma-county-sheriffs-office/
    • Visit the Early Flood Monitoring website to see rainfall and stream levels at specific sites within and near the burn areas: Sonoma.onerain.com
  • In areas where there is limited cell service, or in the event of a power outage, you can receive Emergency Alerts from the NWS using NOAS All-Hazard Radios, which rely on batteries.

 

For information about being prepared visit: https://www.sonomacountyrecovers.org/rain-ready/

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