Mechanical processes are the dominant driver of river ice breakup at the confluence of the Liard and Mackenzie rivers. At this junction, the momentum of the spring freshet from the Liard River overcomes the structural integrity of the ice cover. A RIVICE model was developed to simulate ice jam breakup at this location. Unlike thermal breakups, mechanical events involve rapid ice movements and extensive ice runs, posing the greatest risk of catastrophic flooding to downstream communities. The main focus of the modeling framework is the interaction between the two river systems. At this confluence, the primary deriver, the Liard River, delivers high-momentum flows that lead to instability and mobilization of the more resistant ice at the Mackenzie River. To define the critical thresholds for mechanical failure, RIVICE is calibrated using historical discharge data, ice-jam water level profiles and remotely sensed data. In this research the effects of climate change were investigated following calibrating the RIVICE model. Impacts of projected increased discharges were investigated on the severity of ice jams. Results show that a more vigorous spring runoff increases the mechanical energy available to create thicker ice jams at the confluence. Findings of this study show that changes in runoff patterns increase the risk of mechanical ice jam flooding. These findings are of major importance providing an important tool for infrastructure planning and flood forecasting in ice-jam impacted rivers.