By Emily Baker
Flooding continues to be a serious problem for many major urbanized cities. In particular, the City of Houston has encountered serious flooding over the last several decades, most recently from tropical storm Allison in 2001, a storm causing over $2 billion in damages in the Harris Gully area.
To improve flood alert capabilities, Nick Zheng Fang, a graduate student at Rice University studying civil and environmental engineering, has worked to integrate NEXRAD radar rainfall data, and detailed stormwater system data in GIS frame with VfloTM, an enhanced distributed hydrologic modeling tool, to achieve more accurate and timelier evacuation plans in cases of severe flooding in highly urbanized areas.
“The availability of NEXRAD radar data, GIS databases, accurate distributed hydrologic modeling tools and detailed stormwater system data have made the development of advanced stormwater modeling systems possible,” Fang said, recipient of a 2005-2006 Texas Water Resources Institute’s research grant.
Fang’s research under advising professor Dr. Philip B. Bedient has resulted in an updated hydrologic model of Harris Gully watershed in Houston, a subwatershed of Brays Bayou, which flows in large box-culverts underneath the Texas Medical Center. The medical center was extensively flooded during Allison; stormwater in Harris Gully overflowed, causing flooding of the streets and buildings around the medical center. The model represents the existing drainage network, incorporating representative sewer and road systems in the updated model. Stormwater sewer systems are not generally modeled as part of hydrologic flood analyses for urban watershed areas.
“We focused on development of an enhanced distributed hydrologic model for Harris Gully that better represents the stormwater drainage network than the existing one does,” Fang said. The use of VfloTM, a distribution model that preserves spatial variability by dividing the model domain into interconnected cells, helps researchers better understand the hydrologic and hydraulic response of Harris Gully in relation to Brays Bayou under severe weather conditions. Fang set up an updated hydrologic model by feeding higher spatial and temporal resolution precipitation data into the enhanced model.
“The increased information and accuracy of flood levels will provide Texas Medical Center decision-makers with more accurate flood warning information, enabling them to initiate timely evacuation plans under severe weather conditions,” he said.
Fang said while his study focuses on severe weather issues in the Houston area, an enhanced distributed hydrologic model benefits a wide variety of communities and builds a solid foundation for a future real-time flood alert system for areas as small as Harris Gully.
“Even though Harris Gully was initially chosen as our research testbed, technologies and methodology used in this research can be beneficially applied to any coastal areas frequently impacted by severe rainfall events and tropical hurricanes,” Fang said.
Fang’s research was funded by TWRI as part of the National Institutes for Water Research annual research program through the USGS. TWRI is the designated institute for water resources research for Texas. For more information on his research, visit USGS Research Grants.
