Detached Segmented Submerged Breakwater Made of Geosynthetic Tubes for Kadalur Periyakuppam Coast, Tamilnadu:A Sustainable Shoreline Management Solution

Erosion and accretion are two major issues in shoreline management resulting from natural phenomena and/or manmade coastal interventions. Human interventions with the coastlines such as construction of breakwaters, seawalls, groins etc. are likely to transfer the problem to the adjacent shoreline. Impacts of installation of shore protection measures in one location may not be limited to the project site alone but may extend to a larger coastal stretch on both sides of the project site. Environmental concerns rising out of such issues have led to use of detached segmented submerged breakwaters. In recent times, geosystems such as geosynthetic bags, geosynthetic tubes and geosynthetic containers are increasingly used in the creation of offshore breakwaters. Kadalur Periyakuppam (KPK) is a cluster of three fishing villages, near Kalpakkam in Tamil Nadu. The shoreline at KPK is prone to erosion and the situation gets aggravated during cyclones resulting in large scale loss of beachfront. The sediment transport rates at KPK are estimated using Delft 3D software and analyzed using DETRAN. The studies indicate that long-shore transport is predominant throughout the year and onshore-offshore transport is dominant during monsoon and cyclones. At KPK, the offshore transport during cyclones is the major cause of erosion. Any obstruction to the long-shore transport may result in wide spread erosion to the north of the project site. Therefore a detached breakwater has been proposed as an alternative solution. Offshore breakwaters shall intercept the high energy waves thereby reducing the wave attack on the coast. The breakwater is proposed to be laid using geosynthetic tubes. When an alien material like geosynthetics is introduced to the natural sandy coastal area, it is observed to create ecological changes in the vicinity. In order to study the impact of manmade structures in the coast, a pilot study has been carried out to assess the faunal assemblage on a similar artificial submerged geosynthetic reef present in 6m water depths off Kovalam. The effect of the organisms on the strength of the geosynthetics has been assessed by testing geosynthetic bags deployed at wave breaking areas and also those exposed to direct sunlight. Preliminary studies indicate a positive effect on geosynthetics.