One important component of the HDSS is the Flash Flood Prediction Algorithm (FFPA). FFPA combines two main algorithms, one for QPE calculations and one for QPF calculations. The past and future values of total rainfall accumulation are compared in real-time to Flash Flood Guidance (FFG) values for delineated basins over the Veneto Region. Basins that are approaching or exceeding FFG values are warned upon through various display mechanisms. FFPA QPE calculations are based on the Quantitative Precipitation Estimation Using Multiple Sensors (QPESUMS) developed at NSSL. FFPA QPF calculations are based on the McGill Algorithm for Precipitation Nowcasting Using Semi-Lagrangian Extrapolation (MAPLE) developed at the University of McGill in Montreal. Further, rain gauge data are used in conjunction with the radar derived precipitation rates to reduced the biases inherent in the radar derived estimates.
It is well known that establishing FFG values is a very difficult task. The purpose of this paper is to present the FFPA and discuss the results of a study relating the total rainfall amounts derived from FFPA over a single basin to rain gauge amounts and river surges as measured by stream flow gauges. Using these data sources we work backward to established FFG values. If it can be shown that confidence can be found in the values derived in this manner, the same approach can be applied to the other basins that fall under the FFPA domain over the Veneto region.