Effect of Vegetated Floodplain on Abutment Scour in Compound Channels

Bridge failures due to scour at bridge abutments clarify importance of scour prediction and scour countermeasures. Most of bridge abutments are located in floodplains. One of common cases in floodplains is the existence of vegetation cover. Scope of this study is investigation on effect of vegetated floodplain on vertical wall abutment scour in compound channels. Results show, for constant abutment length and flow depth, with increasing the vegetation concentration, scour depth decreased with an increasing rate. For constant vegetation concentration and abutment length, with increasing the flow depth, effect of vegetation in reduction of scour depth decreased. In abutment with the lengh of 26 cm and concentration with s=8, with increasing the flow depth from 4.8 to 11.8 cm, percentage reduction in scour depth decreased from 40 to 22 percent. Also, vegetation reduces scour hole dimensions and has effect on downstream topography.