Using SWAT to Predict Pre- and Post-Development Hydrologic Regimes

摘要

Hydrology is greatly affected as watersheds transition from rural to suburban to urban. These changes in hydrology may increase flooding and erosion and have a detrimental impact on the aquatic life potential of the streams. These impacts are typically mitigated through the use of structural hydrologic controls such as detention or sedimentation-filtration basins or land use regulations. The impacts of structural controls are typically evaluated on a site-by-site basis using design storms or annual average rainfall. While both of these methods may be valid for sizing controls for a site, they fail to capture the overall changes in a watershed and the temporal changes in the hydrologic regime. This study used a sub-hourly version of the Soil and Water Assessment Tool (SWAT) modified for urban applications to examine the potential changes due to development in the Commons Ford watershed. The 5.9 km2 watershed is located west of Austin, Texas and is currently mostly rural woodlands consisting of eastern red cedar (Juniperus virginiana) and Ashe juniper (Juniperus asheii). The SWAT model was developed using local calibration parameters, existing land use, SSURGO soil data and local 15-minute rainfall. A SWAT model for the watershed was then developedusing a future land use scenario based on current regulations for the watershed but without required controls. Both models were run for twenty years. Differing levels of hydrologic controls were applied to the future development model in the form of sedimentation-filtration and retention-irrigation basins and combination of both. This was used to determine if structural controls may be used to return the hydrology to a pre-developed condition and if so, what type and level controls are needed.