JP2.8 DEVELOPMENT OF A DETAILED DATABASE OF FLASH FLOOD OBSERVATIONS

The primary tool used in the National Weather Service (NWS) to provide guidance toward the likelihood of imminent flash flooding is the Flash Flood Monitoring and Prediction system (FFMP). FFMP “triggers ” when rainfall amounts exceed a 1-, 3-, or 6-hour accumulation threshold, or flash flood guidance (FFG), over basins less than 260 km2 in catchment area. It has been noted that legacy or county-wide FFG values are derived from soil states produced by the Sacramento model which operates on basins up to 4000 km2 at a 6-hourly time step. New, gridded approaches toward deriving FFG (GFFG) have emerged in order to address this scale mismatch. A high-resolution, accurate flash flood observation database was needed in order to evaluate the new GFFG methods relative to the legacy FFG approach