In the autumn of 2005 the National Oceanic and Atmospheric Administration (NOAA) and the USGS entered an agreement to cooperate on a pilot project to issue debris flow warnings for recently burned areas in eight counties of southern California (NOAA-USGS Debris-Flow Task Force 2005; USGS 2005). Rainfall monitoring and forecast is provided by the NWS for the area. Forecasts are issued twice a day and updated if the weather conditions vary. Precipitation monitoring is conducted in real time at the local Weather Forecast Offices using rain gauge networks, NWS doppler radars, and satellite estimates. Several rainfall thresholds have been provided for Southern California (Campbell, 1975; Cannon and Ellen, 1985, Wieczorek 1987; Cannon, 1988; Wilson and Wieczorek, 1995) and the system is currently implemented considering intensity duration thresholds (Cannon and Gartner, 2005; Cannon et al., 2008). The debris-flow warning system has four warning levels and uses the same terminology as in NWS hazardous weather messages (“outlook,” “watch,” and “warning”). Information about the warning level issued is disseminated to emergency management personnel and the public through the NWS Advanced Weather Information Processing System. The joint NOAA–USGS effort has issued numerous watches and warnings for potential debris flows from the winter of 2005 (Restrepo et al. 2009) to the present.