Long-Term Performance of a Flood Alert System and Upgrade to FAS3: A Houston, Texas, Case Study

The second-generation radar-based flood alert system (FAS2) has been operational for more than a decade, and provides accurate advanced warning to the Texas Medical Center (TMC) in the Brays Bayou watershed of southwest Houston. Over the past nine years, FAS has generally predicted floods with average differences of 0.88 h in time of peak and 3.6% in peak flows and a R2 value of 0.90 for the overall performance. After years of urbanization in the watershed, the hydrologic model as a core engine in the system has been updated with recent routing information and loss rate factors to provide more reliable prediction information. Recently, the system has been upgraded into its third generation (FAS3) by incorporating a hydraulic prediction tool—FloodPlain Map Library (FPML)—so that mapped warning information in geographic information systems (GIS) and Google Maps can be provided to emergency personnel in real time. In addition to briefly reviewing the theory and design of the flood warning system for Brays Bayou, this paper focuses on recent improvements with a summary of the flood alert system’s performance over the past years, including three recent major events: Hurricane Ike on September 13, 2008, a smaller event on April 27–28, 2009, and a complex event on July 2, 2010.