Abstract
Three models of flow resistance (a Keulegan-type logarithmic law and two models developed for large-scale roughness conditions: the full logarithmic law and a model based on an inflectional velocity profile) were calibrated, validated and compared using an extensive database (N = 1,533) from rivers and flumes, representative of a wide hydraulic and geomorphologic range in the field of gravel-bed and mountain channels. It is preferable to apply the model based on an inflectional velocity profile in the relative submergence (y/d90) interval between 0.5 and 15, while the full logarithmic law is preferable for values below 0.5. For high relative submergence, above 15, either the logarithmic law or the full logarithmic law can be applied. The models fitted to the coarser percentiles are preferable to those fitted to the median diameter, owing to the higher explanatory power achieved by setting a model, the smaller difference in the goodness-of-fit between the different models and the lower influence of the origin of the data (river or flume).
Highlights
Fluvial hydraulics must search for the solution to the problems related to prediction or determination of the relationship between flow discharge and hydraulic geometry; the sediment transport capacity of the flow; the erosion and sedimentation at the reach scale and the general dynamics of the fluvial geomorphology
The models fitted to the coarser percentiles are preferable to those fitted to the median diameter, owing to the higher explanatory power achieved by setting a model, the smaller difference in the goodness-of-fit between the different models and the lower influence of the origin of the data
The conclusions presented below were obtained from the evaluation of the flow resistance logarithmic model and the two other models developed for flows with high relative roughness conditions
Summary
Fluvial hydraulics must search for the solution to the problems related to prediction or determination of the relationship between flow discharge (or its mean velocity) and hydraulic geometry; the sediment transport capacity of the flow; the erosion and sedimentation at the reach scale and the general dynamics of the fluvial geomorphology. López Alonso et al / Invest Agrar: Sist Recur For (2009) 18(1), 81-91 der size) were not preferably studied, as this type of river was frequently found in less populated, higher and more peripheral regions, which, combined with the greater complexity of the hydro-geomorphologic processes that are found in these, meant that they were traditionally less well known than the alluvial plain sand-bed rivers In contrast with the latter, mountain coarse material-bed rivers are characterized by channels with a greater longitudinal gradient, larger size and more heterogeneous sediment, greater connection with the slope morphogenetic processes, greater relevance of bed load transport, flow with smaller relative submergence and different bed forms. This article is designed to contribute to improving our ability to predict the flow resistance in coarse material-bed rivers
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