EFFECT OF ASPECT RATIO ON BED TOPOGRAPHY AND HYDRAULIC CHARACTERISTICS AROUND SPUR DIKES

the spur dikes has gathered great public attentions from a point of view not only in river engineering but also in water environment, because the spur dikes offers a comfortable environmento aquatic lives and plants as well as human beings in eco-systems. At present, some artificiality side-cavity has been constructed in the rivers for the purpose of the maintenance of the river environment. However, there is little information of form effects of the spur dikes on the bed shape and hydraulic characteristics. In this study, the bed topography and velocity in and around spur dikes in an equilibrium condition were measured with changing the aspect ratio (=streamwise distance of each spur dike/spanwise length of spur dike). It was found that the maximum depth of the scour hole increases with an increase of the aspect ratio and also that crest is located near the junction between the main-channel and side-cavity. The latter result is corresponding to the phenomenon of the Kiso River.