Are coastal protective hard structures still applicable with respect to shoreline changes in Sri Lanka?

Monitoring the changes in coastlines is an important matter and has been the subject of great concern in recent years. The Western and North-Western provincial coasts of Sri Lanka are economically significant and have a highly dynamic nature. This study used satellite images from the Google Earth platform to analyze the changes occurring in the coastal zone during the period between 2005 and 2019 on the Western and North-Western provincial coasts of Sri Lanka. The results revealed that the average coastal erosion rates are -1.21±0.04 m yr-1 in Kalutara, -0.54±0.63 m yr-1 in Colombo, and -0.7±0.58 m yr-1 in Gampaha district. Puttalam district showed a 0.26±0.07 m yr-1 average accretion rate, while the highest accretion rate (0.95 ± 0.58 m yr-1) was evident in the coastal region of Wilpattu National Park, an area that has few anthropogenic interventions. The application of hard structures to mitigate the effect of coastal erosion has increased within the past 15 years. At the end of 2019, the country mainly used revetments up to 23,554 m in length (occupying 9.05% of the total study area), consisting of 18,960 m in the Western province (7.29%) and 4,594 m in the North-Western province (1.76%). The Western province has applied more hard structures at a higher rate than the North-Western province due to mega-development projects. Overall, anthropogenic activities are affecting coastal erosion in that area more than natural or global scenarios, and the applied hard structures have little capability to control erosion.