Using a Distributed Hydrologic Model and Unsteady Hydraulic Model on the West Fork San Jacinto River
Blaney, Tom Michael
Master of Science
Spatially-distributed hydrologic models and 1D and 2D unsteady hydraulic models have successfully been used to replicate the flows and stages during flood events on creeks and bayous in the Houston area. This study applied these models to the San Jacinto River, a river system with thousands of square miles of drainage area, and hydrologically complex situations such as a dam at Lake Conroe, and the East and West Forks of the river intersecting at Lake Houston. Compared to other watersheds typically modeled in this area, the San Jacinto is much larger and more poorly monitored. A spatially-distributed hydrologic model, Vflo, was used to model patterns of rainfall and runoff in the West Fork San Jacinto River’s drainage area. HEC-RAS 1D unsteady hydraulic models were used to model flood heights along the West Fork, and a HEC-RAS 2D unsteady hydraulic model was used to model flood heights around Lake Houston. These models were able to provide a remarkable replication of the flows and flood heights that occurred during Hurricane Harvey within this river basin, with average NSE values of about 0.9. This study then used a land cover prediction model to estimate land cover in 2050 under various developmental regulations consisting of higher elevation requirements and restrictions on development within wetlands. Only regulations that completely prevented urban development in certain areas were found to affect the amount of development that occurred, reducing the increase in developed area from 63% to 55%. This land use data was then applied to the Vflo and HEC-RAS models, modeling the different peak flows and stages throughout the study area during 10- and 100-year flooding events under the different future land development conditions.