Optimization of Length and Space on Groyne Transition (2004-2006)

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 ofthe first spur dike. ln this laboratory research the different ways for reduction of erosion in the first spur dike was investigated. lt is suggested to use a shorter spur dike at the upstream part inclined to the flow direction and towards the head of the first spur dike. 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. These have experienced with two movable bed flumes. Both have 25 m length, 0.8 in depth and one with 1.3 in width and other l.5 m width. The groins have been made by wood, Straight, rigid and Un submerged. Further Experiments have done on third flume. This flume has 20 m length, 0.6 m width and 0.5 m depth. Length of groin to flume width ratio is 1:3. Distances between four groins have chosen times length of groin. ln order to the effect of length and distance of minor groin, one groin with (l/3, %, 2/3) times major length with (1.5, 2, 2.5) times major length have tested with constant slope and difference discharge and bed materials by median size; d5O=0.l9, l and 3 mm. Depth scour in liont of groin noise compared at minor and major groin. Data experimental have analyzed and fitted on equations. The lowest depth scour belong to (1.5--2) length distance. The more minor length 4 causes further scouring on its noise groin and reduce major noise groin.