Suspended sediment fluxes in a tropical estuary, west coast of India

Abstract

Annual transport processes of suspended sediments in Beypore estuary - a tropical estuary along the south west coast of India - were investigated based on time series measurements within the system. It's observed that the sediment transport was upstream during the premonsoon period and downstream during other seasons. Correlation between concentration and velocity at tidal frequencies established that the upstream movement of sediment was largely accomplished by tidal pumping. Maximum flux of the suspended sediment was obtained (1220.97 mg cm sup(-2) s sup(-1)) at the river mouth, during the monsoon period. High negative fluxes were obtained during premonsoon period (381.31 mg cm sup(-2) s sup(-1)) at the mouth of the estuary. During the months of low river flow, the estuary received net sediment inputs from the continental shelf and during high flows exported sediments to the continental shelf depending on the magnitudes of the floods. The major input of sediment from the watershed was 8.8 x 10 sup(4) tons. yr sup(-1) and the net sediment transported towards the continental shelf was estimated as 5.7 x 10 sup(4) tons. yr sup(-1). The net trapping of sediment in the lower estuary was approximately 3.1 x 10 sup(4) tons. yr sup(-1). It's confirmed that the estuary has a pronounced turbidity maximum zone at the bar mouth, where rapid short-term deposition of sediments occur during and following the monsoon freshet