Control of River Bend Migration Using Trapezoidal Spur Shape

Abstract

This research introduces a new type of spur (trapezoidal shape) for control of lateral migration of river bend. Trapezoidal spurs (TS) were installed at four different spaces (4L, 5L, 6L, 8L) in a 90 degrees river bend. The same tests also repeated by installing the traditional types of spurs (rectangular shape) for comparison. TS were attached to the flume bank with angle of 30° from bank to the upstream. The effective length (L) of the spurs (perpendicular length from the bank to the spur’s tip) was equal to one fifth of flume width. Results show that generally the scour depth at the tip of TS significantly decreases compare to the RS. In space of 4L and 8L maximum scour depth was measured as 0.6 and 1.034 times of the effective length of structure. It seems that 4L is the most appropriate space of placing trapezoidal vanes in outer bank bend. It was observed, in the experiment using rectangular vanes, that scouring has been continued to the outer bank around the most vanes; and this scouring has occurred in both upstream and downstream of vanes tip. Maximum scour depth created in this experiment was measured as 1.804 times of structure effective length which has increased about 66.6% compared to using trapezoidal vanes with identical conditions.