The primary tool used in the National Weather Service 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. 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.

The Severe Hazards Analysis and Verification Experiment (SHAVE) has been in operation at the National Severe Storms Laboratory since 2006. Undergraduate students use radar-based products and digital telephone databases, all accessible within Google Earth, in order to call and poll the public about the occurrence and severity of hail, wind, and now flash floods. This paper discusses the criteria used to prompt phone calls and the information requested from the public. We show statistics and make some initial inferences based on the flood calls that were made during the summer of 2008. It is envisioned that this database combined with streamflow observations and Storm Data reports will lead to better tools to predict the likelihood of flash floods.