A Study on Crenulate - Shaped Bays in Coastline of Sri Lanka

Abstract

Various research studies have been reported in the literature investigating the crenulate-shaped bays that are frequently seen in coastlines all over the world and these coastal bays are recognized as the most stable naturally forming beaches under oblique wave attacks mostly due to swell dominant seas. Although many crenulated bays exist in Sri Lanka coastline, no considerable attention has been given so far to investigate their characteristics. The authors have studied the temporal and spatial variations of crenulated bays in many parts of the coastline of Sri Lanka using Google Earth images. Based on the detailed analysis carried out to investigate the shape of the bay profiles using empirical formulations, a hyperbolic tangent formula has been identified as the best fit for crenulated bays in the coastline of Sri Lanka. Considering various coastal sectors and monsoon seasons, different relationships have been derived between the coefficients a and b of the hyperbolic tangent formula. A relationship that has been developed co-relating the coefficient a with few coastal parameters is also discussed. Since many parts of the Sri Lanka coastline are subjected to severe erosion despite the construction of a variety of shore protection structures in traditional ways, a new approach is suggested for carrying out such work where the coastal structures will be aligned in predetermined directions depending on the coastal stretch so that stable crenulated bays will be naturally formed in between these structures, stabilizing the entire coastal stretch. This approach will be very useful in managing coastal erosion problem in the future.