Beach dynamics of Colachel open coast, Kanyakumari District (SW India)

Abstract

Summary. In order to study the beach dynamics of Colachel on the Kanyakumari coast, field investigations carried out on the beach profiles, breaking wave parameters and longshore currents for a period of 25 months from December 2006 to December 2008. Monthly measurements were made on littoral environmental observations (LEO) and beach level variations. Long shore sediment transport rates were estimated based on the observed data. The estimated annual gross long shore sediment transport rate was higher due to recent manmade structures and the net transport was towards west. The beach level was lowest in July and high in April and the range was 75 m. The total volume of sand transported is 1,810 m 3 only. The range of wave heights was between 0.5 to 2.5 m during 2007 and 0.5 to 2.2 m during 2008, whereas wave period was between 8 sec to 15.5 sec and 9.2 sec to 12.8 sec for 2007 and 2008 respectively. The study indicated that the beach is essentially stable but showing only seasonal fluctuations. Colachel, which is being subjected to erosion phase during Southwest monsoon season regained the profiles by January or February. Longshore currents were stronger in June, July and August and steady during rest of the year. The net westerly transport was approximately 0.9 10 6 m 3 during 2007 and 0.3 10 6 m 3 during 2008. This study aims at characterizing the dynamics of Colachel beach, an important natural harbor which lies close on the western side of the peninsular tip of India. The Tamilnadu state encircles nearly 1,000 km long coastline, extending approximately 355 km in Bay of Bengal, 275 km in Palk Pay, 315 km in Gulf of Mannar and 55 km in Arabian Sea. It comprises of rocks, islands, shoals, coral reefs, mangroves, salt marshes, estuaries, tidal inlets, sand dunes and wide beaches. The exchange of littoral drift between the west and east coasts, wave sheltering effect due to Srilankan Island, large sedimentation in Palk Bay, marine parks in Gulf of mannar, advancing sand spit from Dhanuskodi to Talai Mannar, and the long stretch of wide beautiful beaches north of Pondicherry are the exclusive characteristics of the Tamilnadu coast. The present paper is organized in three main sections. In this section, a characterization of the study area and its morphological evolution are presented, followed by a description of the wave climate at a location opposite to the beach. The results obtained for the longshore sediment transport, the beach profile characterization parameters and the littoral environmental observations are presented and discussed.