Flood hydrographs in open channels

Abstract

For flow in open channels, rating curves are indicators by which readings of the flow depth are converted to discharge. Rating curves have unique relations when the flow is steady and uniform. For unsteady flows, produced by flood hydrographs, rating curves show characteristic loops, implying non-unique relations. In this paper, the passage of hydrographs is investigated, focusing on the basic hydraulic parameters, namely mean velocity, discharge and flow depth, and subsequently on other important parameters, such as friction velocity and friction coefficient. The sequence of arrival of their respective peaks is the subject of this investigation. A limited number of laboratory experiments using a simple channel geometry have been performed and are presented.