Quantifying Impacts of Development on Floodplain Evolution and Projections of Future Flood Hazard: Applications to Harris County, TX
Master of Science
This thesis investigates the impacts of urbanization patterns and development activity on evolving flood hazard in the Houston region. Characterized by mild topography and a climate prone to high-intensity rain events, as well as a regulatory atmosphere that has encouraged decades of urban sprawl, Houston serves as an ideal case study area to examine how historical development practices and future growth estimates impact riverine flood hazard. While it has been well-documented that urbanization can increase runoff volume and peak flows, there has been little research investigating urbanization impacts on floodplain extent. It is crucial to understand the relationship between development activity and floodplain evolution in order to characterize the effectiveness of existing flood management infrastructure as well as the impacts of regional development planning and policy. First, historical development impacts are examined in the Brays Bayou watershed by utilizing a physic-based hydrologic model and steady-state hydraulic model to evaluate changes in floodplain from 1970's to current conditions. Results indicate that historical development has resulted in severe increases in floodplain extent and exponential impacts to residential flood exposure. Next, an integrated framework that links land use projection modeling with hydrologic and hydraulic modeling is developed and applied to the Cypress Creek watershed to project increases in flood hazard associated with future development. Utilizing output from an urban growth model, future land use scenarios for the year 2050 are developed, and flood hazard projections are made through integrated hydrologic and 1D/2D hydraulic modeling. A novel methodology for representing on-site detention features, based on current county development regulations, is proposed and applied within the hydrologic modeling framework to ultimately produce realistic estimates of future flood hazard in Cypress Creek based on both regional patterns of development as well as site-scale development policies.
hydrology; hydraulics; floodplain; land use change