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Flood-Impacts on Sediment and Contaminants (Coupled Models Simulation) ?Lower Darby Creek Area (LDCA), PA - SHC10.4.1.4 for Partners
Citation:
Whung, P., J. Barber, B. Pluta, A. Ithier, J. Essoka, M. Mehaffey, S. Woznicki, AND A. Shabani. Flood-Impacts on Sediment and Contaminants (Coupled Models Simulation) ?Lower Darby Creek Area (LDCA), PA - SHC10.4.1.4 for Partners. Region 3 Partners' Meeting, Virtual, Virtual, June 21, 2022.
Impact/Purpose:
The purpose of this presentation is to share our FY22 SHC10.4.1.4 Sub-Product "Flood-Impacts on Sediment and Contaminants (Coupled Models Simulation) Lower Darby Creek Area (LDCA), PA" with the partners and seek for their additional inputs before our Product delivery.
Description:
The Lower Darby Creek Area (LDCA) Site is located in Darby Township and Folcroft Borough in Delaware and Philadelphia counties, Pennsylvania. The Site consists of two separate landfills, the Clearview and Folcroft Landfills. This Phase 2 Lower Darby Creek Area flood vulnerability research extends the 2D modeling domain near the confluence with the Delaware River and will include analyses of landside flooding as well as the influences of dynamic tidal and sea-level rise (SLR) on multiple flood-returning periods (i.e., 10-yr, 100-yr, and 500-yr flood). Six contaminants of concerns (i.e., arsenic, benzo(a)pyrene, chromium, dioxins, lead and total PCBs) were simulated in this study. LDCA Surface sediment contaminant concentrations have been collected in various sampling campaigns between 2002 and 2016. Surface sediment contaminants conditions in major upstream and downstream tributaries (i.e., Darby, Cobbs, Hermesprota and Muckinipattis creeks) and urban background samples from Korman Suites were used as baseline concentration assumptions for tributaries. For research approach, we developed an External Coupler to link hydrodynamic (HEC-RAS) and fate-and-transport models (WASP) to simulate flood-induced sediment and contaminants transport. A Python version of the External Coupler is published in Journal of Flood Risk Management. Our preliminary key results of the influence of dynamic tidal and sea-level rise on 10-, 100-, 500-yr flood-induced sediment and contaminants redistributions at LDCA are (1) Surface sediment volume transport pattern is not a good surrogate for redistribution patterns of contaminants in the sediment, (2) Hydrodynamic mixing of water, suspended sediment in water, and surface sediment is one of the primary drivers in redistributing contaminants, (3) Initial concentration and spatial patterns of the contaminants in surface sediment plays an important role in contaminant concentration changes at the end of flood simulation period, (4) Tributary (input) concentration of the contaminants in surface sediment also plays an important role in contaminant concentration changes at the end of flood simulation period, (5) SLR low (0.5 m) and high (1.5 m) scenarios have minimal dynamic effects on 10-, 100- and 500-yr floods, hence flood-induced redistributions of surface sediment are similar with and without SLR scenarios, (6) 10- and 100-yr flood induced contaminants’ redistribution patterns are similar between with and without SLR L/H scenarios, (7) Contaminants’ redistribution patterns of 500-yr flood with and without L/H SLR scenarios are similar for arsenic, dioxin, tPCB and B(a)P but have noticeable differences in lead and chromium, (8) One potential reason is lead and chromium are the two toxics with significant tributary input during flooding. This illustrates the importance of collecting tributary data during prominent flood events in sampling design to more adequately examining severe flood impacts on mobility of sediment and contaminants in sediment, (9) Regarding the dynamic tidal influence on 10-, 100- and 500-yr flood-induced sediment and contaminants transport, the simulations show net amount of sediment accumulation declined with increasing flood magnitudes, (10) Larger amounts of sediment were flushed downstream out of the model grid toward the Delaware River, (11) Five of the six contaminants surface sediment concentrations were projected to decrease on average, with the largest percentage decrease occurring for B(a)P, and (12) Only lead concentrations increased on average across the model domain likely due to high concentrations in tributary inflows. Larger amounts of sediment were flushed downstream out of the model grid toward the Delaware River.