Design of Fishing Harbour Layout in High Littoral Drift Zone

Estimation of littoral drift and direction of net drift are needed for design of harbour projects. Different methods are used to study shoreline changes in the coastal area. Among them, mathematical modelling is considered as an effective technique. The current study addresses this issue through the use of mathematical models viz. spectral wave model to derive nearshore wave climate, Boussinesq wave model for evolving the harbour layout to provide adequate wave tranquillity in the harbour basin and one line model for prediction of shoreline changes in the adjacent shoreline of the project. In the present study, the mathematical models were applied for design of a layout for fishing harbour, on the West Coast of India in Kerala State. Different alternatives of the harbour layout were tested in order to reduce siltation in the harbour and also to achieve the desired tranquillity in the harbour basin. In the first alternative, the southern breakwater was extended by 340 m. However it was observed that after two to three years, the shoreline will advance and the drift will start entering the harbour basin. Therefore, in the second alternative, the mouth of the harbour was further taken into deeper water to minimize the drift entering in the harbour. With this alternative the wave tranquility studies showed that the layout is adequate to provide desired tranquility in the harbour basin and the wave heights will remain within 0.3 m almost round the year. Thus, mathematical modelling technique was used to evolve a harbour layout that satisfies the tranquillity criteria and also ensures minimum siltation in the harbour basin.