Experiment on streambed armoring with clusters and its influence on bed-load dynamics

Understanding bed-load dynamics over armored streambeds with particle clusters has been a longstanding challenge for river engineers. A flume experiment was conducted to investigate the processes of bed coarsening and cluster formation as well as their influences on bed-load dynamics. During the experiment, the experiment gradually increased inflow discharge from 80 to 145 L/s over 16 h, then maintained a steady discharge of 150 L/s for approximately 32 h. Continuous photographic analysis identified four periods of streambed armoring: (1) bed coarsening, (2) emergence of prototype clusters, (3) interconnecting of neighboring clusters, and (4) formation of mature clusters with high flow belts. Bed surface coarsening, dominant in P1-P2, increasingly restricted bed-load movement. In periods P3-P4 phases, coarsening ceased, while particle clustering intensified, further impeding bed-load transport. To quantify particle clustering, we enhanced the K parameter to parameter by incorporating the diameters of key particles. Our research reveals that overlooking the inhibitory effect of parameters can lead to considerable inaccuracies in the estimation of bed-load transport rates during Period P3-P4, even when advanced surface-based transport models are used.