Design of coastal protective structure for waves and tsunami affected sea front

The recent Indian Ocean tsunami had devastating effect on the south coast of India. A coastal township located 65 Km. south of Chennai was severely affected by tsunami resulting in loss of lives and damage to the property. This coastal township spread over an area of about 5 Sq Km. is located on the sea front extending over 3.5 Km. along the coast. To mark the boundary of the coastal township, a rubble masonry boundary wall was constructed decade ago by the authorities. Natural supply of sediment by a river south of the coastal township ensured presence of 30 to 40m. wide beach in front of the boundary wall. An inlet is located midway on the 3.5 km stretch of the beachfront connecting a huge lake with the sea. Due to the breach of the boundary wall during tsunami, the authorities felt that a new concrete boundary wall shall be built to withstand tsunami and create additional beach features to reduce the intensity of incoming tsunami. This paper deals with a detail study on the characteristics of the beachfront, estimation of force induced by the tsunami on vertical wall, run up, design features for the concrete wall and associated modifications to the beach front which incorporates design of channel and sand dune along the beach. The paper further deals with the beach stabilization measures needed to ensure that the beach is never affected even during storms.