MUDBANKS OF THE SOUTHWEST COAST OF INDIA - VI - SUSPENDED SEDIMENT PROFILES

Physical factors influencing suspended fine sediment loads in the regi on of mudbanks off Alleppey on the southwest coast of India are examin ed. Sediment dynamics of mudbanks is known to be predominantly governe d by waves, and suspended sediment concentration in this area is close ly correlated to local entrainment and settling fluxes due to waves, w hich at times are modulated by effects of weak currents. A simple, sem i-empirical model that accounts for the vertical fluxes of fine, cohes ive sediment in water and across the water-fluid mud interface due to waves and a weak current has been formulated to simulate suspension co ncentration profiles. The model is initially tested against laboratory flume data on wave-induced entrainment of muds, which shows the impor tance of mud rheology in governing resuspension. The model is then use d to simulate suspended sediment concentration profiles measured near the Alleppey Pier under monsoonal waves that create mudbanks close to shoreline. Profiles are generated to represent five documented stages of mudbank evolution from formation to dissipation. Because the field data are very sparse in terms of spatial and temporal coverage, only a limited comparison of model and field is achieved. In spite of this l imitation, the exercise shows that it should be possible to obtain rea sonably reliable site-specific results on predicted profiles of suspen ded sediment over mudbanks, provided adequate field data are available for selecting representative values of the empirical parameters for c alibration of the model.