Radar-Based Flood Warning System Applied to Tropical Storm Allison

Abstract

Flood warning systems in urban areas have greatly improved in recent years with the advent of geographical information systems (GIS), radar-based rainfall estimation using next generation radar (NEXRAD), and delivery systems on the internet. The issue of flood warning and alert was brought to the forefront of public attention in Houston, Texas after the devastation resulting from the Tropical Storm Allison flood of June, 2001. This flood was reported by the National Oceanic and Atmospheric Administration as the most damaging urban flood in U.S. history, and certainly the most devastating event to impact Houston and Harris County with over $5 billion in total damages, and about 50,000 damaged structures. Over $1.5 billion in damages to the Texas Medical Center (TMC) alone were reported, with additional major impacts to the local community. While more traditional gage-based alert systems often provide flood notification to many people, the combination of GIS, NEXRAD, and the internet allows for the more efficient accumulation of rainfall data in real-time. This data can then be used in hydrologic models to estimate peak flows in a basin. This paper will illustrate the design, operation, and performance of an advanced flood warning system, developed for the TMC, which utilizes NEXRAD radar for hydrologic prediction in the Brays Bayou watershed of Houston, Texas. It will specifically document and review its use during the T.S. Allison storm event and other historical events.