Study of Scour and Flow Patterns around Triangular-Shaped Spur Dikes

Abstract

River bank erosion can upset the balance of the river and its aquatic habitat, as well as the lands and facilities adjacent to the river. As hydraulic structures, spur dikes are constructed perpendicularly to erodible river banks in an attempt to divert the flow toward the middle of the channel as a measure for reducing and controlling river bank erosion. The expansion of the scour hole at the tip of the spur dike can lead to structure failure. Inclining the horizontal crest of the rectangular spur dikes (called triangular-shaped spur dike) can reduce the scouring at their tips. There are limitations on the design criteria for this newly-introduced structure. In the present study, the scour patterns developed around triangular spur dikes were examined under different hydraulic conditions and compared these patterns with those obtained for common type of spur dikes (rectangular spur dikes). The three-dimensional velocity components around triangular and rectangular spur dikes were also measured. According to the results, maximum scour hole depth and volume were smaller in the triangular spur dikes than in their rectangular counterparts. Quantitatively, on average, maximum scour hole depth and volume in the former were, respectively, 44% and 70% less than those in the latter. Based on the analyzed the flow patterns, it is recommended that the spacing between the triangular spur dikes should not exceed 5.5 times the effective length of the structure.