Prediction of wind-wave climate along Karnataka coast

Abstract

Karnataka is a coastal state on the west coast of India along the Arabian Sea. The coast experiences a harsh wave climate during the southwest monsoons. Most of the coast is facing problems due to coastal erosion. Hence, in the present study, a numerical model has been set up using MIKE 21 Spectral Wave (SW) module to predict the wave climate. The wave climate along the Indian domain is simulated by wind speed datasets from Global Climate Model (GCM). Wind speed datasets from ERA-Interim is initially validated against in-situ measurement which had a correlation of 0.93. A hindcast study spanning 26 years based on 38 GCMs from different modelling institutes was performed. A comparison of wind speed datasets showed CMCC-CM RCP 4.5 wind projections were closer to ERA-Interim reanalyzed dataset and was used to predict the wave climate. The performance of the MIKE numerical model driven by CMCC-CM RCP 4.5 wind fields showed a correlation greater than 0.7 when validated against in-situ measurement. The numerical model simulations driven by wind speeds from CMCC-CM RCP 4.5 up to the year 2070 showed a gradual increase in the significant wave height which is indicative of the effects of climate change on the wave climate along the Karnataka coast. The projected significant wave height for 2070, when compared with the present wave climate, indicated an increase in the range of 10–21% at the six locations. The predicted wave pattern based on numerical simulations indicated a shift in the peak values in the monsoon month of June along the coast. The predicted wave parameters with a 10-year return period can be used for the design of coastal structures along the Karnataka coast.