Experimental Investigation of Bed Elevation Difference Effects on Erosion and Sedimentation Pattern for Intersecting Channels (Technical Note)

There are some intersecting channels which are seen during operation of open channel networks (Irrigation networks, drainage, navigation and…). It is possible to produce some bed elevation difference during construction and/or because of some reasons such as inaccuracy in implementation, natural action or human made mistakes. In this paper impact of some factors such as discharge ratio, bed elevation difference ratio, erodible and non-erodible bed and bed material grading is experimentally investigated on scour depth in a 90º confluence. The straight channel is 5m long and 30cm width and the intersecting channel is 2.5m long and 30cm width. After analyzing the results and comparing the topography when two channels have elevation difference with the case in which two channels have equal bed elevation, one can find that increasing the difference of bed elevation would result in scour depth increment by 78% while the same increment is less by 45% for the case in which the transverse channel is not erodible. This can be because of a jet flow in the case of non-erodible. Also, increment of flow velocity in the produced steep bed in confluence in the case of erodible bed for both channels, can increase the scouring hole depth.