GENERAL TWO-POINT METHOD FOR DETERMINING VELOCITY IN OPEN CHANNEL.

The generally accepted procedure is to average velocity measurements at 0. 2D and 0. 8D, measured vertically from the water surface,or alternatively to measure velocity at a position equal to 0. 6D, where D is the total depth of flow. In some situations, one may wish to measure at depths other than 0. 2D and 0. 8D. For instance, a temporary stream gage may be continuously monitoring velocity with two probes located at fixed vertical positions. As the total depth changes, the relative measurement position changes. This paper presents a general two-point method that can be used to determine the depth-averaged velocity when measurements at two arbitrary but known depths are available.