Development of Coastal Flood Forecast Capability for the National Water Model

Abstract:

Coastal flooding is becoming a major threat to populations in coastal areas. Rising sea levels and extreme events in recent years have shown how important it is to be able to provide accurate total water forecasts to those living near the coast. To protect coastal communities from tropical storms damages, accurate forecasts of total water level (i.e., a combination of tides, surge and freshwater components) are of vital importance to stakeholders that need to rapidly adopt strategies for potential flooding hazards. This project analyzes the influence of dynamical forcing conditions (wind, surge and river discharge) on total water level prediction in the continental United States (CONUS) by comparing two hydrodynamic models; the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM) and the U.S. Army Corps of Engineers (USACE) open source hydrodynamic software Adaptive Hydraulics (AdH), to demonstrate and evaluate multiple methodologies to improve predictions of total water level and coastal flood inundation forecasts, optimize runtime efficiency, and achieve accurate forecasts. A systematic set of scenarios is generated by coupling each of hydrodynamic models with different combinations of the National Water Model (NWM) with the Global Forecast System (GFS), and the Extratropical Surge and Tide Operational Forecast System (ESTOFS) or the Probabilistic Tropical Strom Surge (P-Surge) model. The NWM provides river channel discharge, and contributes the freshwater forcing for these two models. The GFS supplies the atmospheric forcing data in the form of wind speed and direction, and sea level pressure. In blue sky conditions, water level forecasts (up to 180 hours) from ESTOFS are used as the ocean forcing in these models, while P-Surge is incorporated, when available, during tropical storm conditions.