Numerical Wave Modelling for the Development of Fishing Harbour—Case Study

Abstract

Nearshore wave climate is an important factor for development of any port or harbour. Wave propagation inside the harbour should always be within the allowable safe limit for berthing of ships/boats. The wave propagation inside the harbour is minimised by providing proper sheltering through breakwater. The projection of breakwater should ensure minimum silt entry in the harbour, thereby reducing the dredging inside the harbour. Numerical modelling for present study is conducted for development of fishing harbour at Shiroor, Karnataka, on the west coast of India. Modelling is carried to derive the nearshore wave climate using Numerical spectral wave model (MIKE-21 SW). Wave propagation inside the fishing harbour was analysed using Numerical Boussinesq wave model (MIKE-21 BW) and the shoreline prediction by using LITPACK model. Near the point of interest at −7.5 m depth, the wave transformation studies indicated that predominant wave directions were from 225° N to 290° N directions, i.e. the site is exposed to predominant waves from SouthWest (SW) to WestSouthWest (WSW) directions and waves of significant height of about 3.0 m waves reach the proposed site. Wave climate inside the fishing harbour was assessed for the layout proposed by the project authority consisting of Northern breakwater of length of 205 m and Southern breakwater of length 315 m with 80 m wide opening from the westerly direction. The tip of the breakwater is proposed at (−) 3.3 m. The Numerical model studies carried out by using MIKE-21 BW model for this proposed layout indicated that the significant wave heights in the harbour basin would be are generally in the range of 0.25 m–0.10 m and the layout was adequate to provide desired tranquillity less than 0.3 m in the harbour basin for all the directions. Numerical model studies for shore line have shown that the net drift is towards the North direction and accretion would take place on the Southern side of South breakwater and erosion on the Northern side of North breakwater. Thus, the mathematical modelling studies to evolve fishing harbour layout satisfy tranquillity criteria and also ensure minimum siltation in the harbour basin. With the construction of proposed breakwater, there will not be significant changes in the existing shorelines on the North and South of breakwater.