Analytical and experimental study of bed load distribution at alluvial diversions

Analytical and experimental study of bed load distribution at alluvial diversions

Riad, K.

Thijsse, J.T. (promotor)

Civil Engineering and Geosciences

Hydraulic Engineering

1961-06-14

It has long been observed that at most canal bifurcations the water diverted to the branch does not carry sediment in direct proportion to the rate of flow. Usually, the major part of sediment reaching a bifurcation is diverted into the small branches. This phenomenon has always bothered engineers responsible for the maintenance of irrigation and navigation canals which branch off relatively large alluvial streams. Experimental studies of this problem have usually been limited to the use of fixed bed flumes in which the velocity of flow was measured at different sections in the vicinity of the bifurcation. The distribution of the velocity both vertically and horizontally were then determined and considered as the basis of comparison between different cases. Some investigators studied the pattern of flow near the bed either by the introduction of sediment particles or pottasium permanganate crystals. In the present experimental study, sand was used as bed material and measurements in any run were only taken after the sand movement had reached equilibrium, when the rate of sediment feeding was equal to the sum of the rates of sediment being trapped at the end of main and branch channels. The experimental set-up consisted of a straight flume 20 m long and 0.80 m wide which represented the main canal and a lO m. X 0.50 m flume which branched off the main flume at 45 degrees, 8.20 m. from the upstream end and which represented the branch canal. At first a series of tests was carried out without a sand bed in order to study the wall roughness. Then the sand bed was introduced and a series of tests was carried out to determine the effect of the ratio between branch and main canal discharges upon the sediment behaviour at the bifurcation. In order to control the rate of sediment diversion into a branch, some artificial means have to be applied. In this respect the writer has experimented with the application of dividing walls which direct the bottom flow and guide vanes which direct the surface flow. In general and within the scope of the experiments, the guide vanes gave the better results. Hence, tests were concentrated on the determination of the best location and direction for such vanes, and the results of these experiments led to the recommendations described on fig. 50.

sediment transport
bed load
river diversion
river morphology

http://resolver.tudelft.nl/uuid:66b299fb-d0f5-438b-bd02-0dd7b4d06c61

Waltman Delft

Institutional Repository

doctoral thesis

(c) 1961 Riad, K.