Shore protection against erosion along South west coast of India

One of the serious problems along the coastline of Tamilnadu in the Southwest of India (from 8° 05'30"N and 77°26'30"E to 8°16'N and 77°08'E) of length of about 60 Km has been continuous erosion. The acceleration of erosion is particularly, during the Southwest monsoon that is during May to September. From the past data collection, it is estimated that the erosion rate is of the order of about 0.4 m/year and landmass of about 440 hectares along the coast is affected by erosion over the past 11 years. In order to protect the coast from erosion, a seawall was contemplated as a possible coastal protective measure considering the environmental conditions. Poly propylene geotextile fabric has been placed between the existing soil bed and the base layer to act as a filter media. The seawall is proposed for a length of about 10 Km in 28 different villages along the coast, which were severely affected. The sea bed at certain stretches consists of a number of outcrops and the same time the littoral drift has been quite active and its net direction is towards East. In order to handle the erosion problem, in addition to the seawall as stated above, a groin field was designed and executed. The presence of the groin field lead to the trapping of sediment transport resulting in the shoreline advancement into the sea. As the fishing community wanted the beach that has been built up in between the groins to be used as their boat landing facilities, a few of the groin were bent normal to the predominant wave direction thereby serving as both shore protection measure as well as boat landing facility. The details of the different layers, laying of the geotextile and gabion boxes along with the placing of the armour layers for the seawalls and the design and placing of armour units for groins are discussed in paper.