Browsing Center for Applied Coastal Research by Author "Deb, Mithun"
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ItemA surface porosity approach for eliminating artificial ponding in coastal salt marsh simulations(Coastal Engineering, 2022-11-23) Deb, Mithun; Kirby, James T.; Abdolali, Ali; Shi, FengyanHydrodynamic processes over marsh topography are significantly affected by surface defects such as cuts and rills on channel berms and platforms. These meter-scale features are often missing in the model representation due to the spatial resolution available from data sources, as well as incomplete resolution in the model grid itself. To minimize the artificial hydraulic isolation in the numerical models, we propose implementing an effective porosity algorithm on the marsh surface by considering the fine-scale topography over marsh depressions that control the drainage process. The modification is carried out to eliminate artificial ponding effects observed in model simulations in Bombay Hook National Wildlife Refuge, DE, USA using the original FVCOM code. Results from the revised and original FVCOM models are compared with pressure gauge data collected from an isolated depression in the marsh platform. The new implementations for proper wetting and drying are efficient and accurate for hydrodynamic modeling inside a complex salt-marsh system, which constitutes a major breakthrough in the context of increasing need for better understanding of physical and morphological changes in valuable coastal ecosystems. ItemSensitivity of tidal hydrodynamics to varying bathymetric configurations in a multi-inlet rapidly eroding salt marsh system: A numerical study(Earth Surface Processes and Landforms, 2021-12-22) Deb, Mithun; Abdolali, Ali; Kirby, James T.; Shi, Fengyan; Guiteras, Susan; McDowell, ConorWe describe the development of a high-resolution, two-dimensional hydrodynamic model for a multi-inlet rapidly eroding tidal wetland on the western shore of Delaware Bay, using the finite-volume, primitive equation community ocean model (FVCOM). Topo-bathymetric surveys, together with water surface and current velocity measurements during calm and stormy conditions, have been conducted to support model validation. The tested model is then used to quantify the tide-induced residual transport and asymmetry at major inlet entrances to determine the governing hydrodynamics. We chose a skewness method to calculate the tidal asymmetry and serve as a proxy for sediment transport estimates. The effects of the dredging of an artificial entrance channel and progressive channel deepening in shifting wetland hydrodynamics are shown by developing a scenario analysis. Model results show that the artificially dredged channel has altered the volume exchange at other inlet entrances and increased the net seaward export. The changes in the characteristic frequency of the frictional dissipation in the channel and the system's natural frequency are investigated using a simple ocean–inlet–bay analytical model. Subsequently, we have compared the channel friction scale to the inertia scale and observed that the new connection and gradual channel deepening reduce the overall frictional dominance. Ultimately, the study has shown how the short- and long-term channel bathymetry changes, mainly the artificially dredged channel and progressive channel deepening, can affect the connected system's net circulation and trigger internal marsh erosion.