Experimental study on effect of minor spur dike to reduce main spur dike scouring

Spur dikes are used widely to prevent outer bank river bends and path-modification river projects. Local scouring in spur dile nose is due to contraction and strong eddy is among the important problems occurring in designing Super dikes. Experimental study has been done on effect of length and alignment of minor spur dike to reduction of main spur dike scouring. In order to do this study a shorter spur dike was used in two stages، one perpendicular and one angled to flow channel direction. By non dimensional parameters، contraction ratio L/B=0. 3، 0. 35، 0. 4، 0. 45، (L=length of spur dike، B=width of channel)، Length ratio L’/L=0. 5، 0. 6، 0. 7، (L’= length of minor spur dike) and distance ratio x/L=0. 5، 1، 1. 5، 2، 2. 5 have been studied. Scour depths at nose of minor and main spur dike have been measured. Data collection were fitted by regression analysis and a relation for reducing scour depth at nose of first spur dike is provided، with and without minor spur dike.