Simulating flooding where rivers flow into the ocean is challenging because existing Earth system models cannot adequately capture the complex interactions between river currents, tides and storm surges.

In response, researchers developed an expanded framework for the Energy Exascale Earth System Model (E3SM), incorporating advanced river and ocean models that improve the way such interactions are simulated. The work is published in the Journal of Advances in Earth System Modeling.

Compound flooding occurs when increased river discharge and ocean water levels interact over a coastal region. Current Earth system models are limited in accurately simulating these processes due to insufficient resolution in computational meshes and insufficient detail about how rivers and oceans are connected.

This study establishes a comprehensive framework for E3SM and demonstrates the framework’s ability to simulate a specific composite flood event in a Mid-Atlantic estuary. The framework combines atmosphere, land, river, and ocean models, each with its own level of detail near the shoreline, to account for their different physical processes.

The results show that the E3SM framework can reproduce river discharge and sea level variations reasonably well. By simulating the interaction between river and ocean, we can better understand the effects of coastal water on river discharge caused by tides and storm surges during a compound flood.

The simulation shows that compound flooding is most significant when a tropical cyclone produces the highest storm surge but moderate river discharge. This study demonstrates the ability of the E3SM model to accurately simulate the detailed coastal processes.