Linking Continental-Scale Watershed Hydrologic and Coastal Hydrodynamic Models for Improved Water Level and Inundation Prediction in the Great Lakes

In an era of non-stationarity in coastal water levels, including sea-level rise as well as record low and record high water levels in the Great Lakes within the last ten years, accurate representation of coastal hydrology and hydrodynamic processes is critical for total water prediction in the coastal zone. The predominant approach to water prediction has been to isolate watershed hydrologic models from downstream coastal conditions (e.g. sea- or lake-level), and similarly to neglect land-surface runoff and coastal flooding in hydrodynamic forecast systems. As a result, the impacts of the current record-high water levels in the Great Lakes are not adequately captured by the existing suite of operational forecast models, in which increased coastal inundation, erosion, and beach hazards are being experienced by coastal communities. The goal of this effort is to improve water prediction in the coastal zone by linking the NOAA National Water Model (NWM) and the NOAA operational Great Lakes coastal hydrodynamics models, built on the Finite Volume Community Ocean Model (FVCOM). This project consists of three objectives: (1) aggregation of NWM streamflows into tributary inputs into FVCOM for improved lake-level prediction, (2) implementation of coastal water level conditions into NWM for improved streamflow prediction, and (3) extension of FVCOM model domains into the land-watershed for improved coastal flooding and water exchange. Model results are presented to highlight the impacts on coastal prediction as well as on implications for lake-management.