Interference processes on scouring at bed sills

摘要

The local scouring downstream of bed sills forming a sequence for bed stabilization in steep channels has been investigated in a laboratory flume. The initial bed slopes ranged from 0.078 to 0.148. The bed alluvium was characterised by a non-uniform grain size distribution. The results show that when the ratio between the critical water depth h_c and the sill spacing L rises above a characteristic value the scouring dynamics become heavily affected by the presence of the downstream sill, associated with the onset of a form of "interference" which renders the scouring process less effective. The difference with an "undisturbed" case is demonstrated. Self-affinity of scour holes is confirmed and the scour length appears to be the reference parameter from which the scour depth might be evaluated.