Development and skill assessment of a real-time hydrologic-hydrodynamic-wave modeling system for Lake Champlain flood forecasting

In response to record-breaking flooding on Lake Champlain in 2011, the International Joint Commission launched a 5-year study to explore solutions to flooding in the binational Lake Champlain-Richelieu River (LCRR) basin. As a component of the study, a real-time flood forecasting modeling system was developed to provide short-term (5 days) water level and wave forecast guidance, intended to enhance flood preparedness by providing advanced warning of flooding to residents and other stakeholders within the basin. The system consists of a hydrodynamic model built on the Finite Volume Community Ocean Model (FVCOM) with one-way coupling to a WAVEWATCH III wave model. The National Water Model stream network was expanded to include the entire LCRR domain and is used to inform river inflows into the system. Water level output from the hydrodynamic model shows strong agreement with gauge observations at annual and short-term time scales, with an increasing negative bias at longer forecast horizons. Modeled significant wave heights compared well with observations from a wave buoy deployed as part of the study and also have a negative bias in the latter portions of the forecast. The scale of the errors in modeled water levels and wave heights is consistent with an underestimation of river inflow and wind speed inputs, respectively, based on validation of this model forcing against available observations. The development and validation of the LCRR modeling system serve as a precursor for the first operational real-time 3D hydrodynamic-wave forecast system for Lake Champlain.