National Weather Service United States Department of Commerce

NOAA

NOAA/USGS DEMONSTRATION
FLASH-FLOOD AND DEBRIS-FLOW
EARLY WARNING SYSTEM

USGS

Project Description

Once the smoke clears from a wildfire, the danger is not over!! Other hazards, such as flash floods and debris flows, now become the focus. Areas recently burned by wildfires are particularly susceptible to flash floods and debris flows during rainstorms. Just a short period of moderate rainfall on a burn scar can lead to flash floods and debris flows. Rainfall that is normally absorbed by vegetation can run off almost instantly. This causes creeks and drainage areas to flood much sooner during a storm, and with more water, than normal.

School Burn Area
November 2005 - School
Burn Area near Ventura, CA
Harvard Burn AreaAdditionally, the soils in a burn scar are highly erodible so flood waters can contain significant amounts of mud, boulders, and vegetation. The powerful force of rushing water, soil, and rock, both within the burned area and downstream, can destroy culverts, bridges, roadways, and structures, and can cause injury or death if care is not taken.
October 2005 - Harvard Burn Area near Burbank, CA  
Demonstration Warning System Operation
The National Oceanic and Atmospheric Administration (NOAA) and the United States Geological Survey (USGS) have established a demonstration flash-flood and debris-flow early-warning system for recently burned areas in southern California. The demonstration project covers eight counties within southern California. The National Weather Service (NWS) employs multiple forecasting and monitoring tools that identifies when both flash floods and debris flows are likely to occur based on comparisons between radar precipitation estimates and/or real-time rain gage accumulations and established rainfall intensity-duration Country Club Drive
October 18, 2005 - Debris flow that impacted Country Club Drive in Burbank, CA below the Harvard Burn Area
USGS Intensive Research Area
Intensive Research AreaAn Intensive Research Area (IRA) was proposed in USGS Circular 1283 as a research component of the Prototype Warning System to establish studies that could lead to advancements in the operation of the Prototype. The IRA is intended to provide links between detailed precipitation measurements and hillslope and channel monitoring that will lead to advancement in the understanding of post-fire runoff and erosion processes, and the development of flash floods and debris flows. This enhanced knowledge is expected to assist in the development of more refined warning models. In 2010, the station burn area in Los Angeles County was selected for the location of the IRA. The adjacent map shows the location of the Station Fire burn area.
Other Links
USGS Landslide Hazards Program
Warning System Report and Fact Sheets
Fire Boundary Map
Flash Flood and Debris Flow Guide