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

ABSTRACT 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 periods P3–P4, even when advanced surface-based transport models are used.