Impacts on Surface Infiltration and Runoff Generation in an Urban Coastal Environment from Integrated Modeling of Antecedent Groundwater Condition Scenarios
Image credit: AGUAbstract
The effectiveness of existing stormwater management methods in the Mid-Atlantic Coastal Plain is threatened under future conditions. Greater precipitation depths and more frequent groundwater flooding increase the demand on stormwater systems, while urbanization, reductions in recovery time between storms, and damage to plants from exposure to saline water reduce their effectiveness. We have coupled EPA’s Stormwater Management Model (SWMM) and USGS’s MODFLOW to study the combined effects of changes seen in several environmental drivers like sea and groundwater level rise, increasing groundwater salinity, and changing precipitation patterns near Dover, Delaware. Preliminary model results show a connection between groundwater level and runoff generation after rainfall. Because the groundwater table is so shallow in the study area, potential infiltration volume at the land surface is limited by the thickness of the vadose zone. If the groundwater table reaches the land surface, infiltration halts and all additional rainfall goes to runoff, even over pervious areas, until the groundwater level subsides. Here, we explore results from coupled model simulations of typical and extreme antecedent groundwater and weather conditions drawn from the historical record and the predicted future. Results can be used to assess the resilience of existing stormwater infrastructure to this coastal stressor, which can only be evaluated using integrated models such as this SWMM-MODFLOW model.
Austin K. Farnum
PhD Student
Omowumi Erukubami
PhD Candidate
Dannielle Pratt
Postdoctoral Researcher
