Real-Time Flood Warning System—A Regional Flood Mitigation Tool for Houston, Texas

The role of flood warning systems as a non-structural flood mitigation tool is extremely important in flood prone urban centers such as Houston, TX, in which existing flood control infrastructure was proven insufficient to protect vulnerable areas from inundation, based on reported flood damages from severe storms in recent years. While flood warning systems currently exist for the Houston region, they are only focused on providing relevant information for selected watch points (i.e., real-time streamflow or stage). Additionally, these systems do not usually consider rainfall from tropical cyclone (TC) events, which although infrequent, could be devastating for the region. An effective watershed-wide flood warning system would require accurate flood warning information that extends beyond selected watch points to aid in evacuation planning, traffic rerouting, and emergency rescue operations. To address these shortcomings, a pilot study to develop a real-time, catchment-wide flood warning system on Brays Bayou watershed in Houston, TX is conducted using the HEC-RTS (Real Time Simulation) platform. Developed by the Hydrologic Engineering Center, HEC-RTS is designed to integrate various HEC software (e.g., HMS, ResSim, RAS, and FIA) with a flexible API (Application Programming Interface) that allows for scripting-based retrieval of observed and forecasted precipitation data and real-time production of different forecasting products. The objectives of this study are twofold: (1) to investigate the feasibility of using HEC-RTS for automated, real-time forecasting operations in the Houston region, and (2) to evaluate and determine the appropriate precipitation forecast product for daily convective events as well as TC events. For these purposes, various rainfall forecasting products such as NOAA’s QPF (Quantitative Precipitation Forecast) and HRRR (High-Resolution Rapid Refresh) in addition to TC rainfall predictions are compared to NEXRAD rainfall and rain gage data for several storm events. Using the most accurate forecasting products for the study area, forecasts of streamflow and stage conditions are simulated using a hydrologic model (HEC-HMS) and 1D unsteady hydraulic model (HEC-RAS), respectively. This study intends to provide real-time streamflow, stage, and floodplain maps of forecasted inundation for the entire Brays Bayou watershed, and to potentially expand the same framework to other flood-vulnerable watersheds in the region.