Scour reduction by minor spur dike

One of the common methods of river improvement and bank protection is using spur dikes. Building spur dikes makes the flow path to be modified. Concentrating the flow in the middle part of the river causes the river side not to be washed out. The new flow path makes the river bed next to the end of the spur dikes to be washed out. Usually the spur dikes are built in group because of extending the protected zone. The stability of these spur dikes against the river flow depends on stability of the first spur dike. The purpose of this laboratory research is to investigate different ways for reduction of erosion in the first spur dike. It is suggested to use a shorter (minor) spur dike at the upstream part perpendicular to the flow direction. Aim in this research، it is intended to find the optimum distance between shorter spur dike and first spur dike in order to have minimum erosion in the first spur dike. From the hydraulics point of view، L’/L (the length of shorter spur dike to the length of first spur dike)، X/L (the distance between first spur dike and shorter spur dike to the length of first spur dike) and Froude number has been studied and results has been presented in the form of equations.