SUSPENDED SEDIMENT CONCENTRATION DURING RIVER ICE BREAKUP

River ice breakup is known to be an important geomorphologic agent, cr eating numerous erosional and depositional features within river chann els and on adjacent floodplains. Despite such evidence, information ab out the suspended sediment concentration and bed load during breakup i s virtually nonexistent. Measurements of suspended sediment concentrat ion were made during the 1987 breakup of the Liard River, N.W.T., Cana da. Results showed a gradual rise during the pre-breakup period follow ed by an order of magnitude increase at the time of the major river-ic e run. The ice-affected peak concentration of 1067 mg/L falls within t he recorded range of annual open-water peaks that were produced by flo w events of 2-5 times greater discharge.