Development of a Coupled Hydrologic–Hydrodynamic–Wave Flood Forecasting System for Lake Champlain

The Lake Champlain-Richelieu River system is vulnerable to flooding caused by a combination of precipitation, snowmelt, and wind set-up and waves. In 2011 record lake levels occurred over several months caused by a rain falling on a extensive snowpack in the basin. The record flood of 2011 was further exacerbated, at times, by wind set-up, due to persistent winds from the south. Historical observations of Lake Champlain elevations at the Rouses Point, NY gage have shown that water levels there can increase by 6 to 12 inches when average south wind speeds over the lake range between 25 to 35 knots for durations of 6 hours or more. This led to extensive flooding along the Richelieu River in Quebec as well as around the shores of the lake. In response these events, the International Joint Commission has implemented a five year project to reduce the damages from lake floods. A main challenge to forecasting these events is the lack of forecast guidance that considers the effect of wind events on the lake. Therefore, advanced model forecast guidance is being developed to improve forecasts of the lake/river system. The modeling framework couples the Weather Research and Forecasting-Hydrologic distributed model (WRF-Hydro) with a hydrodynamic model based on the Finite Volume Community Ocean Model (FVCOM).Wind waves in lake are predicted by the wave model based on the WAVEWATCH III model. These models are selected because they form the basis for existing operational National Weather Service model guidance (i.e., the National Water Model, the Great Lakes Operational Forecast System, and the Great Lakes Wave Modeling system) and will be transitioned to future operational use by the Northeast River Forecast Center and the Burlington VT Weather Forecast Office. Inflows from the WRF-Hydro model will be provided to the FVCOM Lake Champlain model to improve water budgets in the hydrodynamic model and will form the basis for further model coupling. Configuration, hindcasts, and skill assessment of the hydrologic, hydrodynamic, and wave models for the Lake Champlain basin will be presented. The framework for the future coupled flood forecast guidance for the basin will be described.