Sediment Load: Concentration and Transport

Abstract

Amount of suspended sediment in water is measured by collecting water samples from different depths during high and low tide . Rate of transportation of bed load has been computed using well accepted empirical equations. Suspended sediment amount ranges between 3.1 and 5.05 gm/l in non-monsoon season and 4.97 and 6.5 gm/l in monsoon season. During non-monsoon period, upstream penetration of suspended sediment is more during high tide (3.71 × 107 to 1.29 × 108 metric tons/year) than that is discharged towards downstream during low tide (2.5 × 107 to 1.0 × 108 metric tons/year) and accelerates the rate of sedimentation . But in monsoon, the transport of suspended sediment during high tide (7.5 × 107 to 2.45 × 108 metric tons/year) and low tide (7.3 × 107 to 2.3 × 108 metric tons/year) is almost equal which restricts the sedimentation rate. Rate of suspended sediment transport is strongly affected by variation of water discharge (r = 0.908) and moderately affected by sediment concentration (r = 0.553). Increasing tendency of water velocity and discharge towards downstream leads to the increase of bed load transport rate from Kolaghat to Geonkhali. It varies from 0.1905 to 6.52985 kg/m/sec, 0.5008 to 14.74893 kg/m/sec and 0.2318 to 6.31764 kg/m/sec in pre-monsoon, monsoon and post-monsoon season respectively. In non-monsoon season, the transport of bed load is more during high tide than during low tide, but the transport of bed load is almost equal in both the tidal phases in monsoon season.