| Riverbed girdles are constructed to prevent bed-degradation and local scour around foundation of revetments in small and medium-sized rivers. Theplane shape of riverbed girdle is basically set straight across the channel, but some kinds of upstream-pointing weir have been used for the purpose of channel stabilization in North-America. Local scour downstream of the riverbed girdle make drop and disturb the passage of aquatics at normal stage of water. In this study, effects of the plane shape of a riverbed girdle on movable-bed are experimentally examined. Three types of plane shape are examined, straight type, upstream-pointing type and split type. In cases with upstream-pointing types and split types, large scour holes made by parallel helicoidal motion of flow are observed. It was shown that apex angle have an effect on local scour at the tip of riverbed girdles. |
