Wave–current-surge interaction in a changing climate over a shallow continental shelf region

Abstract Wave climate over the North Indian Ocean region experienced a paradigm shift in the recent past, indicating an increase in the extremes. Wind-waves and swell climatology have shown an increasing trend over this region, having direct implications on the coastal zone dynamics surrounding the mainland and island features. The present study aims to investigate the wave–current-surge interaction characteristics over a shallow continental shelf region between India and Sri Lanka using the state-of-art coupled ADCIRC-SWAN model. In particular, a case study performed during tropical cyclone Madi (2013) demonstrates the extreme wave–current-surge interaction mechanism over varying nearshore bathymetric features. Study investigated the wave reflection and transmission characteristics in both the absence and presence of the proposed navigation channel (known as Sethusamudram project) in a coastal vulnerability context. Construction of the channel may result in westward shift of hazardous coastal water zones attributed to storm tides. The navigation channel expects to enhance both extreme waves and storm surge by 1% and 4%, respectively. Synthetic experiments, considering an increase in sea level rise by 0.4 m expected by 2050, indicate that wave activity can increase by 3% with marginal variations in storm tide. Simulations performed with a 7% rise in tropical cyclone intensity reveals a substantial increase in storm surge (10%) and significant wave (20%) heights along the coastal belt.