SUSPENDED SEDIMENT CONCENTRATION DURING RIVER ICE BREAKUP

River ice breakup is known to be an important geomorphologic agent, creating numerous erosional and depositional features within river channels and on adjacent floodplains. Despite such evidence, information about the suspended sediment concentration and bed load during breakup is virtually nonexistent. Measurements of suspended sediment concentration were made during the 1987 breakup of the Liard River, N.W.T., Canada. Results showed a gradual rise during the pre-breakup period followed by an order of magnitude increase at the time of the major river-ice run. The ice-affected peak concentration of 1067 mg/L falls within the recorded range of annual open-water peaks that were produced by flow events of 2-5 times greater discharge.