Evaluation of High-Resolution Flash Flood Forecasting in the Dallas–Fort Worth Metroplex

With increasing urbanization, there is an increasing need for high-resolution flash flood forecasting to provide time- and location-specific watches and warnings in densely populated areas. With advances in modeling, computing and communications, it is now possible to operate high-resolution hydrologic models in real time, and generate and disseminate the resulting products. Evaluation of such products, however, is a large challenge; compared to the nominal resolution of the products, the resolution at which traditional observations of water level or flow is available is much coarser. In this presentation, we describe an ongoing effort in the Dallas-Fort Worth Metroplex (DFW) area to evaluate the skill in streamflow prediction for urban catchments and its dependence on scale and physiography. The water level observations used are from a combination of the High Water Warning Systems operated by the cities and ultrasonic distance measuring sensors deployed on a number of bridges throughout DFW. We also compare the model-simulated soil moisture with the observed at a small number of locations to assess the quality of model states. The hydrologic models used are the NWS Hydrology Laboratory Research Distributed Hydrologic Model and WRF-Hydro used in the NWS’s National Water Model. The rainfall forcing is from the CASA WX network of X-band radars. At most locations, rating curves are not available for which we use an indicator statistics-based approach to relate simulated flow with observed stage. In this presentation, we share the preliminary results and identify issues and challenges.