DCCM was tasked by the USACE ERDC Coastal Hydraulics Laboratory to utilize and test an in-development version of the Adaptive Hydraulics Model (AdH) software to complete a monolithic simulation of Hurricane Harvey compound flooding that occurred in August 2017.

Many efforts investigating the effects of compound flooding have relied on discrete models that simulate each flooding process separately. Consequently, they fail to mechanistically account for the complex interaction of multiple flood processes and the resulting impact on hazard estimates. Novel capabilities of AdH enable economical simulations of very large model domains while providing a high-resolution description of flood hazards in two dimensions. AdH provides the capability to simultaneously implement spherical coordinates and solve the shallow water equations and diffusive wave equations within a simulation. The combination of these capabilities makes AdH an effective model to simulate rainfall, overland flow, and storm surge to produce estimates that account for the interacting effects of pluvial, fluvial, and coastal flooding.

Model terrain derived from LiDAR provided a high-resolution description of topography and large river channel bathymetry was resolved. Spatially and temporally variable rain rates and wind fields within the model resolved heterogenic storm characteristics. Model results were compared to stage and discharge time series observations at over 30 locations throughout Harris County and Galveston Bay. Modeled peak stages are within 1 m of observed peaks at more than 80% percent of the stations.

The methods presented here can serve as a template for estimating flood hazards that result from compound flood events, and the results have documented the ability to mechanistically account for the interacting effects of multiple flood processes with a 2-D hydrodynamic model.