Spatial scale data requirements using NEXRAD (WSR-88D) for accurate hydrologic prediction in urban watersheds

The deployment of the WSR-88D (NEXRAD) radar by the National Weather Service in 1992 has created the possibility for enhancing flood warning systems. Due to the improved spatial resolution of the radar, a better hydrologic prediction is possible on a real-time basis. Rainfall rates can currently be derived from radar data real-time at a resolution of 16 km2, whereas post-processing of the radar data can yield rainfall rates at a resolution a small as 1 km2. This study examined the scale effects of the radar-rainfall input on the hydrologic prediction at two urban watersheds during two recent severe storms and compared the results the hydrologic prediction using rain gages and to the observed hydrograph. Small deviations were observed with the different grid scales, but these differences were considered minor compared to other unknowns in hydrologic modeling. Additionally, lead-times were quantified for both bayous