EFFECT OF CHANNEL LENGTH ON BED LOAD TRANSPORT

Abstract

The work reported in this thesis is an experimental Investigation regarding the effect of channel length on bed load transport. The main objective was to collect accurate data on the bed'load transport rate of a sediment over a wide range of flow conditions for different lengths of alluvial channel and to determine the equilibrium length of an alluvial channel. The equilibrium length is a mobile bed length of channel beyond which the transport rate is in equilibrium. Experiments were performed in a rectangular flume 30.0m long, 0.20m wide and 0.50m deep for different lengths of mobile bed which are 28.47m, 21.35m, 14.24m and 7.12m. The observations of bed load transport rate were taken at two different slopes and eight different discharges. The uniform sediment of geometric mean size as 1.673mm and relative density as 2.65 was used for this investigation. The data were collected at equilibrium condition at which the input sediment rate Is equal to output sediment rate. The observed bed load transport rates were compared with computed bed load transport rates by the methods of Samaga (11) Meyer-Peter & Muller (5) and Garde & Albertson (4), and found to be in good agreement for full length data, whereas the transport rates of shorter lengths were found to be less. Although equilibrium lengths could not be obtained in the experiments for most of the flows test, the result were extrapolated to obtain them. A tentative predictor is proposed which needs further confirmation from data of different sediment sizes