Evaluating the Hydrodynamic Performance of Green and Gray Infrastructure in Urban Watersheds for the Greater Houston Region
Doctor of Philosophy
Flooding is the costliest hazard in the United States. Among the many flood prone areas in the nation, the Greater Houston Region is considered one of the most vulnerable, due to high intensity rainfall, flat topography, high imperviousness, and poor infiltration. Traditionally, Houston’s flood control strategy involves the implementation of gray infrastructure (e.g., channelization and detention basins). However, even after spending billions of dollars on numerous flood reduction projects, Houston continues to suffer from flood damages. Houston’s severe flooding issue has prompted various efforts to develop new flood control strategies. One alternative is Green Infrastructure, or Low Impact Development (LID), which consists of land development strategies aiming to preserve predevelopment hydrology. Originally designed to improve water quality, LID has also been shown to attenuate flood flows. Despite its popularity in the Northeast and the Northwest, the flood reduction benefits of LID in the Greater Houston Region are poorly understood. Moreover, most currently available models capable of simulating site-scale LID features are applied to small-scale study areas, providing limited insight at the watershed-scale. To bridge these knowledge gaps, this research proposes a method to model two site-scale LID features: green roofs and rain gardens at the watershed level. The hydrologic performance of an experimental watershed-wide LID implementation at The Woodlands is evaluated using a distributed hydrologic model. The findings suggest that LID features can be used able to reduce peak flow and runoff volume for smaller magnitude and intensity storms, but has limited effects for larger, more intense events. For comparison, this research also examines the hydrodynamic performance of gray infrastructure at two different scales of implementation: a catchment-wide flood reduction project at Brays Bayou and a local drainage improvement at Harris Gully. Due to the difference in application scales, floodplain analyses of both studies reveal varying degrees of flood reduction benefits. By understanding the flood reduction potential and limitations of green and gray infrastructure, this research can help floodplain managers and local stakeholders in the proper selection of flood control strategies.
green infrastructure; low impact development; gray infrastructure; hydrologic and hydraulic modeling