Now showing 1 - 3 of 3
  • Publication
    Overbank flow depth prediction in alluvial compound channels
    Algorithms based on simple one-dimensional stage–discharge models for compound channels have been developed and tested for overbank flow data from the UK Flood Channel Facility and the University of Ulster channel with straight and meandering planforms. The proposed divided resistance approach takes into account the grain resistance, the bed form resistance and the roughness characteristics of the floodplain but it was found to give unsatisfactory prediction of the flow depth for compound channels with rough floodplains. A simple algorithm for stage–discharge prediction based on a lumped resistance approach was then proposed. It requires calibration of the overbank Manning n for a relative depth zero and a coefficient of proportionality, and this is achievable if measurements of the flow depth and velocity are taken for at least three overbank flow discharges. The application of the lumped approach to various flume and field data showed good agreement between the measured and predicted flow depths.
      564Scopus© Citations 10
  • Publication
    Discharge assessment in mobile-bed compound meandering channels
    (Institution of Civil Engineers, 2003-12-01) ; ; ;
    Many discharge prediction methods have been developed for compound meandering channels. Most of these methods have been found to produce reasonable results for fixed-bed channels, but the effects of the presence of a mobile main channel bed on discharge assessment have yet to be assessed. Sediment movement increases the complexity of experiments by facilitating the creation of bedforms, which alter flow resistance. The shape characteristics of these bedforms and their associated roughness are known to depend on channel stage and geometry, and to vary with flow conditions. This paper seeks to assess the performance of six discharge assessment methods using the Phase C mobile-bed meandering UK Flood Channel Facility (FCF) overbank flow data. The results show that the accuracy of the different methods depends heavily on the boundary roughness, and the James and Wark (1992) method performed most consistently for the range of floodplain configurations tested. A modification to this method is also presented that is shown to improve the accuracy of the predicted discharges.
      484Scopus© Citations 2
  • Publication
    Sediment transport formulae for compound channel flows
    Nine sediment transport formulae were reviewed and applied to both inbank and overbank flows in straight and meandering compound channels. The predictive capabilities of the formulae were evaluated using experimental data obtained from the large-scale UK Flood Channel Facility and the small-scale Ulster Channel. The Yang formula (1979) was found to give the best prediction for sediment discharge, performing well for both straight and meandering channels. The Schoklitch (1962) and Yang and Lim (2003) formulae also gave very good predictions for most of the data sets studied. The Ackers and White formula (1973) gave very good prediction for the large-scale facility but overpredicted the sediment discharge for the small-scale channel. The Karim and Kennedy (1981) formula could also be a good sediment discharge predictor, for the studied flow conditions, but the coefficient of proportionality used in the formula needs to be calibrated.
      894Scopus© Citations 4