Instantaneous water surface and bed scour profiles using video image analysis

In steady open-channel flow, the use of a conventional point gauge to obtai n the water surface profile yields reasonably accurate results. However, in unsteady and quasi-steady flows, the point gauge is not of much use. Furth ermore, in flow fields where there is significant bed scour, it is often of interest to the hydraulic engineer to obtain the instantaneous bed scour p rofile during the scouring process. In most quasi-steady flows involving be d scour, the water surface profile continuously readjusts itself in respons e to the changes in the bed profile. To carry out a proper analysis of the entire flow field, it is necessary to obtain both the instantaneous water s urface and the corresponding bed scour profiles. The development of a nonin trusive video image analysis procedure to simultaneously obtain the water s urface and bed scour profiles in a two-dimensional flow field is presented in this paper. A computer program entitled PROSCAN has been developed to ex tract the water surface and bed scour profiles from digitized video images of the flow field. The use of PROSCAN is demonstrated by obtaining the inst antaneous water surface and bed scour profiles for a two-dimensional flow f ield downstream of a sluice gate.