Ice Jam Modelling and Field Data Collection for Flood Forecasting in the Saint John River, New Brunswick

Ice jams cause major flooding and severe damages to communities and infrastructure along the Saint John River. There is a growing need to develop capability in forecasting and analyzing icejam-related flood events. This capability is also essential in anticipating the potential for increased ice jam damages as a result of a changing climate. The HEC-RAS model, which can simulate ice jam configuration under steady-state conditions, has been calibrated for operational application along the international Saint John River from Dickey, Maine, USA, to Grand Falls, New Brunswick, Canada. Examples of model results are presented and the modelling experience gained to date is outlined. A potentially damaging consequence of jamming is the sharp wave that is generated upon ice-jam release. Such waves, called javes for short, propagate very rapidly and can greatly amplify flow velocity and hydrodynamic forces relative to runoff waves. As modelling capability is limited for such dynamic phenomena, a field data collection program was initiated in 2007 to measure jave characteristics during the spring breakup of the ice cover. This program involves deployment of portable pressure loggers at key locations along the river. Data recording can extend well beyond the breakup event to also capture the open-water, spring flood. Representative data are presented and jave properties are compared to those of post-breakup runoff waves. Future work towards improving modelling capability is discussed.