PNNL

The Science

Simulating flooding where rivers meet the ocean is challenging because existing Earth system models struggle to capture the complex interactions between river flows, ocean tides, and storm surges. In response, researchers developed a comprehensive framework for the Energy Exascale Earth System Model (E3SM), incorporating advanced river and ocean models that improve how such interactions are simulated. This new framework accurately reproduces river discharge and ocean water levels, as well as significantly improving representation of their interactions. This research development marks a significant advancement in resolving the complex physics in coastal zones.

The Impact

The existing Earth system models are limited at simulating riverine and coastal flooding at the terrestrial–aquatic interface, especially during hurricane events. To overcome such limitations, this study presents recent model developments incorporated into a unified framework to better represent multiscale coastal processes. The new capabilities include novel uses of high-resolution, regional-refined computational meshes, two‐way coupled river–ocean models, and the E3SM ocean model with tide and surge explicitly resolved. This novel methodology demonstrates its efficacy in capturing the interactive processes at the river–ocean interface, providing valuable insights into flood modeling and revealing the nonlinear impacts of river discharge and storm surge.

Summary

Compound flooding happens when elevated river discharge and ocean water levels interact in a coastal zone. There are limitations in current Earth system models to accurately simulate these processes because of insufficient resolutions in the computational meshes and insufficient details on how rivers and oceans are connected. This study creates a comprehensive framework for E3SM and demonstrates the framework’s ability to simulate a specific compound flooding event in a Mid‐Atlantic estuary. The framework combines atmosphere, land, river, and ocean models—each with its own level of detail near the coastline—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 forced by tides and storm surges during a compound flooding event. The simulation reveals that compound flooding is most significant when a tropical cyclone produces the highest storm surge but moderate river discharge. This study demonstrates the capability of the E3SM model to accurately simulate the detailed coastal processes.

PNNL Contact

Zeli Tan, zeli.tan@pnnl.gov, Pacific Northwest National Laboratory

Funding

This work was supported by the Earth System Model Development program area of the U.S. Department of Energy, Office of Science, Biological and Environmental Research program as part of the multi-program, collaborative Integrated Coastal Modeling project.