Impact of Geospatial Data Enhancements for Regional-Scale 2D Hydrodynamic Flood Modeling: Case Study for the Coastal Plain of Virginia

Hydrology in low-relief coastal plains is especially challenging to simulate in flood modeling applications. Two-dimensional (2D) hydrodynamic models are often necessary, but creating such models for regional-scale systems at a high spatial resolution presents significant data challenges. The objective of this research is to explore these challenges using a 2D hydrodynamic model built for a $\mathrm{5,800}\text{-}{\mathrm{km}}^2$ region in the coastal plain of Virginia as a case study. Systematic enhancements to the hydrodynamic model’s topographic, bathymetric, streamline, surface roughness, and rainfall representations are tested to assess their impact on the model’s predictive skill. Results showed that incorporating high-resolution terrain and land use data sets alone only produced minor improvements to model accuracy. However, the addition of river cross-section data collected through site visits and careful, detailed quality control (QC) of observed rainfall data produced much more substantial improvements to accuracy. Based on these findings, increased focus should be placed on integrating topographic and river bathymetric data sets for low-relief coastal plain regions along with improved methods for QC of observed rainfall data, especially for extreme weather events.