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You are here : eLibrary : IAHR World Congress Proceedings : 35th IAHR Congress - Chengdu (2013) : THEME 5 - FLUVIAL HYDRAULICS AND RIVER MANAGEMENT : Adaptation-to-capacity Length for Fluvial Sediment Transport
Adaptation-to-capacity Length for Fluvial Sediment Transport
Author : Zhijing Li, Zhixian Cao, Gareth Pender and Peng Hu
Over the last several decades, various sediment transport capacity formulations have been used by geomorphologists and engineers to calculate fluvial morphological changes. However, it remains poorly understood if the adaptation to capacity could be fulfilled instantly in response to differing inflow discharges and sediment supplies, and thus if the calculation of morphological changes in rivers based on the assumed capacity status is justified. The recent theoretical work on the multiple time scales of fluvial processes have revealed that bed load sediment transport can adapt to capacity sufficiently rapidly and yet this is not the case for suspended sediment transport. Here we present an extended work along this line. The distance required for sediment transport to adapt to capacity (i.e., adaptation-to-capacity length) of both bed load and suspended sediment transport, in line with reduced or increased sediment supply from the upstream, is computationally studied using a coupled shallow water hydrodynamic model. It is found that the adaptation-to-capacity length generally decreases as the Rouse number increases, irrespective of whether the sediment supply increases or reduces, and notably, for zero sediment supply cases, a unified relationship is found between the adaptation-to-capacity length and the Rouse number. Quantitatively, the adaptation-to-capacity length of bed load sediment is limited to tens of times of the flow depth, whilst that of suspended sediment increases substantially with decreasing Rouse number and can be up to hundreds of times of the flow depth. The present finding concurs with the recent time scale analysis that bed load sediment transport can adapt to capacity much more rapidly than suspended sediment transport, and it facilitates a quantitative criterion on which the applicability of bed load or suspended sediment transport capacity for natural rivers can be readily assessed.
File Size : 472,211 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 35th IAHR Congress - Chengdu (2013)
Date Published : 18/07/2016
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