TEMPORAL VARIABILITY IN BED LOAD TRANSPORT DURING ARMOR BREAKUP AND REFORMATION IN A DEGRADING CHANNEL EXPERIMENT

To study the effects of armor breakup and formation on the temporal variability of bed load transport, five groups of long-duration laboratory experiments were conducted. High resolution time series of bed load transport (1s) and bed load grain size distribution (10min) were measured by the sediment trap system at the outlet of the flume. The evolution of bed load transport rates in non-uniform bed exhibits more complex behavior even under constant flow conditions, and the evolution could be divided into three stages from a larger timescale. The infrequent bursts of bed load transport rates, caused by armor breakup, contribute to more than 10% of the total bed load mass in only 2-8 minutes, indicating their vital role in sediment transport. The changes in bed morphology are directly related to the strong autocorrelation and significant trends in bed load transport rates, while on a well-developed armor surface the bed load transport behaves more like a random process.