Evaluating the Effects of Groundwater on Runoff Modeling

Surface runoff models can provide useful predictions about the flow of runoff through a watershed. They can help develop plans and control methods for releasing excess flow into the environment at predevelopment levels to reduce flooding and erosion downstream. The Moore’s Mill Creek Watershed is located in Lee County in east Alabama. Rapid development in the watershed has caused a large amount of sediment to wash off into Moore’s Mill Creek, and thus it has been classified as an impaired stream under section 303(d) of the Clean Water Act. It is expected that the increase in impervious surfaces has contributed to an increase in runoff, resulting in higher concentrations of Total Suspended Solids (TSS) in the creek. An ongoing project is built on previous research for the upper reaches of the Moore’s Mill watershed which was calibrated using PCSWMM. The model has been recently improved to include parameters for groundwater-surface water interactions assuming a uniform SWMM aquifer object to improve the description of hydrograph’s recession.

The current objective of this project is to expand the model to include the entirety of the Moore’s Mill watershed for the future purpose of developing the model to predict the concentration of TSS throughout Moore’s Mill Creek. Data will be collected at several points along the creek for water depth and rainfall. Parameters for groundwater and land use will be calibrated to best fit the hydrograph recession curves. A comparison will be drawn between two versions of the model that do and do not account for groundwater interactions. It will be determined how significant groundwater interactions are to SWMM predictions of surface water runoff. It will also be determined if the single uniform aquifer is applicable to the entirety of the Moore’s Mill watershed.