Flow over weirs using upstream and downstream levels. National Rivers Authority river flow forecasting system

The theory of flow over compound Crump and Flat-vee weirs under non-modular conditions is presented. This theory is employed to develop software for weir flow estimation using upstream and downstream (or crest) measurements of river level. Application of the software to 19 weirs in the Yorkshire Region is demonstrated for the flood of 26-29 August 1986. First, it is used to assess the severity of backwater effects at each site. Second, the software is used to explore the prospect of developing a single rating relation, based on upstream levels only, under non-modular flow conditions. A set of Appendices provides details of the software, weir configuration data and a guide to how the software may be used.