The main purpose of this study is to understand the stabilizing effect of ground-sills on the riverbed through a series of flume model experiments. From results, although check dams have the ability to control upstream sediment transport, the mass energy produced by the free fall of the overtopping discharge still causes strong local scour downstream of the structure, and this scour leads to the instability of the check dam. Therefore, this study conducted model experiments on various types of serial ground-sills to determine the appropriate spacing to best protect the downstream bed. Based on the observations and analysis of channel geomorphology and sedimentation, this study concluded the following results: 1) Serial ground-sills reduces the sediment transport ability perfectly, especially under a mild channel gradient equipped with 2-4 times the average channel width interval. But for steep slopes, it is suggested that the proper spacing should be shortened to 1-2 times the average channel width. 2) Ground-sills can effectively protect the streambed from scouring under a suitable equipped condition and the concepts of guiding scour and riverbed inertia were used in the analysis of optimal ground-sill spacing.
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