Hydrological simulation of extreme weather and long term erosion
The work is comprised of a hydrometeorological investigation of a major central Texas flooding event along with two studies using hydrological models to examine long term erosion from unit source and riverine sized watersheds. Tropical Storm Hermine produced a 500 year rainfall event in 2010 along a narrow portion of central Texas resulting in severe flash flooding. Analysis of meso and synoptic scale storm properties along with Weather Research and Forecasting simulations suggest terrain from the Balcones Escarpment aided in focusing precipitation in the region. Hydrological simulations using the Gridded Surface Subsurface Hydrologic Analysis model detailed the flood hydrology. The remaining chapters utilize quality empirical records to assess the ability of erosion simulations. Chapter three is concerned with a long term daily sediment records (12-51 years) from 5 unit-source watersheds in central Texas. The data are simulated with hydrological models and the role of large infrequent erosion events in the makeup of the overall soil loss record is examined. The work indicates the upper 10% of erosion events comprise roughly half of the long-term soil loss sum. Chapter four exploits a high quality empirical dataset of hydrographic bathymetric surveys to examine the accuracy of hydrological models empirically developed rating curves. The empirical dataset consisted of three hydrographic surveys spaced over fourteen years. The study found large underestimations in model simulations of sediment delivery to the reservoir when suspended sediments at the lake entrance were used for calibration.