Sediment dynamics of Negombo Lagoon Ooutlet, Sri Lanka

This paper presents a 2DH modelling approach used to investigate sediment dynamics and potential morphological changes of the Negombo lagoon outlet, Sri Lanka. Schematised wave, wind and river-inflow parameters were imposed representing the present day forcing scenario. The model was initially calibrated against the measured water level and velocity data, and then implemented to observe sediment dynamics and morphodynamics. Northward alongshore transport in this area changes to the west-east orientation at the outlet and is interrupted by the lagoon sediment export. Channels at the lagoon end have different transport capacities. Residual transport showed a sediment exporting system in the lagoon. One-year period of morphological evolution suggested that the narrow connecting channel between the lagoon and the sea experiences erosion and sedimentation in front of the lagoon entrance. Also, erosion at the apex of the western headland provides sediment to south and north therein.