Evaluation of relative hydrologic effects of land use change and subsidence using distributed modeling
Bedient, Philip B.
Doctor of Philosophy thesis
The present research employs remote sensing data and advanced hydrologic modeling to improve the spatial representation of an urban watershed, Whiteoak watershed, located northwest of downtown Houston, TX. During the last thirty years, upstream Whiteoak experienced rapid growth that locally altered its topographic and hydrologic parameters through land use change and subsidence. This study examines whether land use change and subsidence contributed to the increased flooding occurrences of the last decade in the area, amplifying the impact of moderate and extreme rainfall events. Detailed digital elevation data acquired from a 2001 Light Detection and Ranging (LIDAR) survey of Harris County, NEXRAD radar rainfall data, satellite land cover data, historical areal photos, and subsidence contours provide the main topographic and hydrologic parameters that support the analysis. All data sets are compiled in a GIS environment, processed, transformed into grid format, and imported into a physics-based, fully distributed hydrologic model, Vflo(TM). After setting up and calibrating the Whiteoak Vflo model, the analysis focuses on an upstream area located in the center of the subsidence bowl. Quantitative results indicate that continuing subsidence since 1978 did not significantly impact the local peak flows. On the other hand, the combined effect of upstream channel modifications and land use change over the same time period increased considerably the peak flows at the 100 year level.