Modeling ice jam release waves with consideration for ice effects

The sudden release of a river ice jam can produce a dramatic ice run and rapidly rising water levels, resulting in a significant threat to human safety and property. Therefore, it is highly desirable to have reliable forecasting models for these events. Previous investigations suggest that models should consider the effects of ice to achieve accurate prediction of such events; however, the effects of ice on the propagating release wave are not yet well understood. This paper explores the extent of ice complexity necessary to successfully model ice jam release events. Simplified ice effects were incorporated into a fully dynamic one-dimensional hydraulic model. In the model, ice mass continuity is solved with the total ice-water mass and momentum equations in an uncoupled sequence. The ice momentum effects are empirically considered by introducing ice resistance and ice diffusion terms into the model. A hypothetical ice jam release is simulated to illustrate the model's performance in comparison with published results for a more sophisticated ice process model which considers ice effects deterministically, and the proposed model is shown to perform well. In addition, application of the proposed model to two actual ice jam release events further proves the applicability of this approximate formulation for modeling ice jam release events. From these results it appears that ice effects are most significant in the first few jam lengths of propagation, as noted by other researchers for field events.