THE EFFECT OF MINOR SPUR DIKE ON SCOURING AT THE FIRST SPUR DIKE IN THE GRAVEL BED

Spur dikes are the most important river training structures. The main reasons for their usage are redirecting the flow of water and preserving the desired depth of a river or channel. Diversification of the flux is also a very important goal for spur dike planning. An experimental look on the effect of length and orientation of minor spur dike on scouring at the first spur dike in the gravel bed is presented in this paper. One of the important problems in spur dike design is a local scouring at the head of spur dike. This phenomenon is derived by area contraction and powerful vortex. This study is performed in the experimental flume. The spur dike used in this study was rigid, made of pressurized ply wood, straight and non-submerged. Four spur dikes with distance equal two times the first spur dike’s length and perpendicular to the flume’s wall are used in this study. Three different discharges are used in the gravel bed with constant slope. In all of the experimental studies performed, the method of reducing scouring at the head of spur dike and how the minor spur dike in the upstream end, can decrease the erosion at first spur dike is investigated. The ratio between lengths of minor spur dike to first spur dike length was recognized as a very important feature that results in preserving the head of the spur dikes from scouring.