Southeastern Section - 68th Annual Meeting - 2019

Paper No. 28-4
Presentation Time: 9:00 AM


KUHL, Hannah, M.S. in Environmental Studies, College of Charleston, 66 George Street, Charleston, SC 29424, ELLIS, Kathryn K., McCormick Taylor, 1441 Main Street, Suite 857, Columbia, SC 29201, KUHL, Hannah, Marine Resources Research Institute, South Carolina Department of Natural Resources, 217 Fort Johnson Rd, Charleston, SC 29412, ROBINSON, Joshua, Robinson Design Engineers, 10 Daniel Street, Charleston, SC 29407, GREENFIELD, Dianne I., Environmental Sciences Initiative, CUNY Advanced Science Research Center, Earth and Environmental Sciences, Queens College, 85 Nicholas Terrace, ASRC Room 5.318, New York, NY 10031 and CALLAHAN, Timothy J., Geology and Environmental Geosciences, College of Charleston, 66 George Street, Charleston, SC 29424

Changes in the natural environmental related to urbanization lead to anthropogenic stress in coastal regions, such as increases in stormwater volume and pollutants entering aquatic ecosystems. These stresses can be observed as alterations in the hydrology and ecology in tidal creeks and salt marsh wetlands. In this study, we collected and modeled hydrology data for five different ebb-dominant tidal creeks along the central coast of South Carolina. Water velocity and cross-sectional area of flow were observed under a variety of tidal conditions over multiple years using an acoustic Doppler current profiler (ADCP). Hydraulic geometry relationships were developed using measurements of width, depth and velocity to estimate the discharge of tidal creeks. Total discharge volume (or tidal prism) and nutrient loading was calculated from modeled time-discharge regression equations. Estimates of runoff volume entering the creek system were modeled for four different unit hydrograph design storm events (corresponding to local standards for volume and peak flow reduction requirements). These tidal flow and stormwater runoff models were also used to evaluate the thresholds at which stormwater runoff volume surpasses the volume of the tidal prism, which could result in depression of salinity levels and/or increase in pollutants that would be detrimental to the biota of these tidal creek ecosystems. A presumptive total maximum daily load (TMDL) for total nitrogen (TN) and total phosphorus (TP) was developed for four of the creeks using the results. The goal was to inform regulators and managers about potential numeric criteria for these nutrients in estuarine waters in this region. Understanding these relationships between hydrology, water quality, and development in tidal creek watersheds will help managers protect the resiliency and productivity of these valuable ecosystems.