Simulating Compound Flooding Events in a Hurricane: Baroclinic Effects and Backwater Processes

Simulating compound flooding events in a hurricane: baroclinic effects and backwater process

Yinglong J. Zhang^a1, Fei Ye^a, Haocheng Yu^a, Weiling Sun^a, Saeed Moghimi^b, Edward Myers^b, Karinna Nunez^a, Ruoyin Zhang^c, Harry Wang^a, Arond Roland^d, Kevin Martins^e, Xavier Bertin^g, Jiabi Du^e, Zhuo Liu^a

1. Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA 23062, USA
2. Coast Survey Development Laboratory, NOAA, Silver Spring, MD 20910, USA
3. State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China
4. BGS IT&E, Darmstadt, Germany
5. EPOC (CNRS-Université de Bordeaux) - UMR5805, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
6. UMR 6250 LIENSs CNRS-Université de La Rochelle, Institut du Littoral et de l’Environement, 2 rue Olympe de Gouges, 17000 La Rochelle, France
7. Department of Marine Sciences, Texas A&M University at Galveston, Galveston, TX 7754, USA

Abstract for AMS 2020

Compound flooding is usually induced by the concurrence of coastal storm surge and heavy precipitation induced river flooding, with the former involving oceanic processes and the latter involving hydrological processes. We present a creek-to-ocean 3D baroclinic model based on SCHISM (Semi-implicit Cross-scale Hydroscience Integrated System Model) that aims to unite traditional hydrologic and ocean models in a single modeling platform, by taking full advantage of the polymorphism (i.e. a single model grid can seamlessly morph between full 3D, 2DV, 2DH and quasi-1D configurations). Using Hurricane Irene’s impact on the Delaware Bay as an example, a seamless 2D-3D model grid is implemented to include the entire US East Coast and Gulf of Mexico with a highly resolved Delaware Bay (down to 20-m resolution). The model is forced by flows from National Water Model (NWM) at the landward boundary. We demonstrate the model’s accuracy, stability and robustness with the simulation of the storm surge and subsequent river flooding events. Through a series of sensitivity tests, we illustrate the importance of including in the simulation the baroclinic effects, as provided by the large-scale Gulf Stream, in order to correctly capture the adjustment process following the main surge and the subsequent compound flooding events. The baroclinicity can explain up to 14% of the elevation error during the adjustment phase after the storm. Our results also confirm the occurrence of backwater effect into far upstream rivers and creeks and thus demonstrate the need for a dynamic two-way coupling between the hydrodynamic and hydrological models.