Numerical Modelling of Tidal Inlet Dynamics

Tidal inlets are ecologically sensitive coastal features, where its opening along the shoreline permits free exchange of water through flooding and ebbing flow. The shoreline openings may constitute bays, lagoons, marsh or estuaries. The formation of sandbars, spits, and shoals is more common at the inlet mouth particularly along the coasts dominated by longshore sediment transport. These formations act as a barrier, blocking the entrance of tidal inlet and thus restricting flow/exchange of water. The sandbar and spit formation are usually minimized by construction of a pair of training walls, prior to which monitoring the local hydrodynamics at the inlet vicinity is essential. In the case where the tidal inlet meets an estuary, the volume of water exchanged at the inlet mouth are governed by the inlet dimensions and rate of littoral transport. After a comprehensive discussion on the hydrodynamics and morphodynamics of estuaries, its application is considered through a detailed investigation of a micro-tidal inlet at the Arasalar estuary, a tributary of the Cauvery river, in Karaikal (10° 54′ 52″ N; 79° 51′ 09″ E), situated along the southeast coast of the India. The numerical model using the finite volume method is applied to estimate the siltation rate and its distribution within the domain, driven by the tide-induced currents and riverine discharge and validated through field measured data. This chapter provides the procedures to be followed in identifying the problem of siltation and arriving at a suitable mitigation measures to reduce siltation within the inlet to facilitate smooth navigation.