Variability in wave refraction and resultant nearshore current patterns: Exposed versus sheltered beaches along north Karnataka, west coast of India

Abstract

For predominant waves approaching from directions varying between SW and WNW and periods varying from 6 to 11 sec, the refraction function (Kd) shows amplification of wave heights resulting in concentration of wave energy on headlands and reduction of wave heights in headland-bays and at river mouths. Certain stretches of open ocean beaches located on either side of the Kali River and the headland-bay beaches south of Karwar Head experience relatively higher wave heights for W and WSW waves, the latter being more prone to higher wave heights for waves from SW. The higher wave energy zones shift towards the central-northern sectors of the beaches, as the direction of wave approach changes from WNW to SW. The northern and southern stretches of headland-bay beaches receive partial shelter from the headlands for predominant waves approaching from northerly and southerly quadrants respectively. The Karwar port as well as agreater stretch of the Karwar-Kodibag beach being on the lee side of Karwar Head, receives good shelter for WSW and SW waves and only the extreme northern part of the Karwar Beach is affected by these waves. Southerly flowing longshore currents are generated along the coastline for WNW waves, except for the presence of converging currents along Karwar Beach and in the southern parts of headland-bay beaches. The southerly longshore current reverses to northerly flow along Karwar Beach, and zones of converging currents prevail along Ramnath-Sadashivgad beach in the north and at the Kali River mouth for W and WSW waves; for SW waves, converging currents prevail along the headland-bay beaches. The converging currents observed for W and WSW waves along these open ocean beaches are similar to those identified along similar beaches reported elsewhere on the west coast of India