Abstract
The aim of this study is to construct a modeling system that will assist flood risk management strategies in a coastal plain braided river system. The model configuration consists of a hydrodynamic model (ADCIRC) of the river basin that receives tidal forcing at the open boundary and river discharge forcing at upstream flux boundary. An unstructured mesh model resolving the Pearl River channels at higher resolution from the coastline to approximately 75km inland to upstream reaches of the river has been constructed. The modeling system produces water levels and currents throughout the Lower Pearl River Basin. Initial sensitivity analysis efforts on the channel model include consideration of low-flow, average-flow, and high-flow scenarios. Model results were found to be slightly sensitive to slope of river channels and bottom friction to control stability in predictions. The model results were shown to be highly sensitive to the bathymetry of the model that controls the discharge capacity of the narrow river channels and the channel model resulted in elevated currents and water levels under high flow conditions. A channel discharge capacity analysis was conducted and the results showed the need to construct a floodplain mesh around the channel model with more realistic bathymetry and topography so that the flooding scenarios could be modeled with wetting and drying capability of ADCIRC. An initial attempt to develop such a floodplain mesh has been made with preliminary results and more comprehensive validation of the developed floodplain modeling system will extend to reproducing events associated with the historical Hurricane Isaac that impacted the region in 2012. This modeling system will provide an important tool to decision makers that could be used in future flood risk management and mitigation efforts.
Highlights
The Lower Mississippi River Forecast Center (LMRFC) is one of 13 NOAA National Weather Service (NWS) centers in the United States that makes decisions on flood risk management control strategies and that is responsible for warning local authorities and emergency managers before and during flood events
At low flow conditions, simulated water levels and currents appeared reasonable while water levels and currents predicted in river channels started to rise to uncharacteristically high values for the average flow case
This study has shown the capability of Advanced Circulation Model, ADCIRC, in simulating riverine flow of a complex, braided river system, the Pearl River in the Lower Pearl River Basin
Summary
The Lower Mississippi River Forecast Center (LMRFC) is one of 13 NOAA National Weather Service (NWS) centers in the United States that makes decisions on flood risk management control strategies and that is responsible for warning local authorities and emergency managers before and during flood events. The historic hydrographs used by NOAA-NWS LMRFC to predict flood conditions in the Lower Pearl River Basin, south of Interstate-10, have been unreliable, and no numerical hydrodynamic model forecast capability currently exists To address this capability gap, federal and local government partners came together with research partners to address needs and interests in regards to flood risk management and mitigation with an objective to develop a modeling system that simulates existing conditions in the Lower Pearl River Basin for water levels and currents. This model will serve as a tool for analyses of past major events as well as a capability for predicting future events that will enable improved warning and management strategies.
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