Prioritization of Flood Forecasting and Precipitation Monitoring Locations for Vulnerable Communities.

An hierarchical analytical framework was applied to identify communities with the most pressing need for stream gages and weather stations, for improved flood forecasting services and gauge locations in Texas. The objective was to supplement the National Weather Service’s (NWS) Advanced Hydrologic Prediction Service (AHPS) that helps mitigate economic losses by providing flood and drought forecasts at over 7,800 points across the United States. The NWS-AHPS system provides flow forecasts and flood warnings for needs including emergency response, flood control, reservoir operation and more. Forecasts may include how high a river might rise, when it will reach its peak, where property will be flooded, and how long the flooding will continue. Information provided to water managers and emergency personnel supports decisions regarding evacuation of people and goods, or using reservoir storage capacity and operations to reduce flood impacts. Unfortunately, there is insufficient coverage across Texas, leaving some communities vulnerable to flood as exemplified by the Memorial Day floods in Wimberley last year.

Prioritization of stream gauges considers the socio-economic impact suffered by communities, available locations for stream gages (typically bridges and other areas with easy access to the river) in each prioritized watershed. For candidate locations, simulated flows at proposed monitoring sites were evaluated in a physics-based distributed model at 1-km resolution of the watersheds affecting Texas Communities. Runoff from rainfall input from an extreme storm event (Wimberley/Blanco May 23-24, 2015) was simulated for each vulnerable community. The relative magnitude of the peak flows, the volume of water produced by the event, and the lead time provided by each possible stream gage location will be considered in determining the optimum location for the stream gage in each watershed. In the example described above, a stream gage much further up in the watershed would have provided more lead time to the citizens of Wimberley, but may not have helped determine the extreme magnitude of the flood. In many watersheds, the locations evaluated provide lead-time and were recommended, while other watershed exhibited little or no lead time due to hydrologic/hydraulic characteristics relative to the vulnerable community forecast location.

This analysis identified, ranked, and recommended over 50 locations for installation of stream gauges. Gaps in rain gauge coverage were also analyzed and recommendation made. Enhancing the hydrometeorological monitoring network will assist the NWS in conducting its mission to mitigate loss of life and property damages caused by floods in Texas.