Ice-jam model testing: Matapedia River case studies, 1994 and 1995

During the 1994 and 1995 spring breakup events, ice jams were formed on the lower Matapedia River and remained in place long enough to permit collection of detailed field data on jam thickness as well as on water surface elevations. Together with bathymetric data that were obtained in the following summers, the spring measurements form one of the most complete ice-jam data sets that have been obtained to date. This allowed examination of how well current understanding of the hydromechanics of ice jams, incorporated in a numerical model, can describe the results of the measurements. The availability of jam thickness data was particularly advantageous because it removed the ambiguity associated with model calibrations that are solely based on water level measurements. With suitable choice of the model parameters, the model reproduced the measured water level profiles of the jam very closely, while providing reasonable simulations of jam thickness. The selected values of the model parameters were consistent with values established by previous applications on other rivers, and almost identical between the two Matapedia jams, despite contrasts in jam severity and river flow. Model sensitivity was explored using the more complete 1995 data set and found to be moderate. The detail of the available data also made it possible to scrutinize hydraulic resistance characteristics of flows underneath ice jams, and confirm earlier formulations specifically designed to address extreme-roughness conditions.