Changes to a Drive-In Beach in Southwest India Due to Severe Erosion and Subsequent Reformation
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Available online at www.sciencedirect.com ScienceDirect Aquatic Procedia 4 ( 2015 ) 357 – 364 INTERNATIONAL CONFERENCE ON WATER RESOURCES, COASTAL AND OCEAN ENGINEERING (ICWRCOE 2015) Changes to a Drive-in Beach in Southwest India Due to Severe Erosion and Subsequent Reformation P K Abdullaa*, C V Pravya Jayaraja, M T Priyalakshmia, K Chandrana, E J Jamesb a Centre for Water Resources Development and Management, Kunnamangalam, Kozhikode 673 571, India b Karunya University, Karunya Nagar, Coimbatore, Tamil Nadu 641 114, India Abstract Driving in beach, a fascinating recreational activity is in vogue in a few special beaches in the world. Management plans are formulated for these beaches to overcome the adverse impact of beach driving on the overall coastal ecosystem and to ensure the safety of both the passengers and others who frequent the beach. The management plans for drive-in beaches often deal with the vehicle conditions such as tyre pressure, number of driving wheels and their dimensions and also the environmental conditions of the beach such as wave conditions, storms and stages of tide. However, such a management plan has not been formulated for the Muzhappilangad drive-in beach of Kerala on the southwest coast of India. Generally, this beach experiences only normal changes during the monsoon. However, during the 2013, a portion of the beach underwent severe recession which lead to the ban of vehicles to the eroded part of the beach. A portion of subsequently reformed beach became unfit for vehicle driving. Erosion brought changes to the wave breaking pattern. Plunging waves are observed at some stretches of the eroded beach; spilling breakers continued on either sides of this portion. After reformation, spilling breakers are observed in the entire length of the beach. Samples extracted from three depths by core cutter prior to erosion and after reformation revealed that the mean diameter and standard deviation of the particle changed significantly at the severely eroded portion where plunging breakers are experienced whereas; at other portion of the reformed beach, the changes in the particle size is very nominal. ©© 20152015 The The Authors. Authors. Published Published by byElsevier Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license (Peerhttp://creativecommons.org/licenses/by-nc-nd/4.0/-review under responsibility of organizing committee). of ICWRCOE 2015. Peer-review under responsibility of organizing committee of ICWRCOE 2015 Keywords: Drive-in beach, Wave breaking; Grain size; Beach recession, Malabar coast Nomenclature d16 – size of 16 percentile of the sediment sample d50 – mean diameter, size of 50 percentile of the sediment sample d84 – size of 84 percentile of the sediment sample σ – standard deviation of particle size in the sediment sample which is defined as square root of the ratio between d84 and d16 * Corresponding author. Tel.: +91-495-2351825; fax: +91-495-2351808. E-mail address:[email protected] 2214-241X © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015 doi: 10.1016/j.aqpro.2015.02.048 358 P.K. Abdulla et al. / Aquatic Procedia 4 ( 2015 ) 357 – 364 1. Introduction Beaches are often preferred recreational places and tourist destinations. Number of well known recreational/tourist destinations exist on the coastline of many countries. The coastline of India is about 7530 km of which 5440 km is of the mainland and remaining is of the Lakshadweep, the Andaman and Nicobar groups of Islands. Many beautiful and virgin beaches exist along the coastline of India. Fishing, playing games such as beach volley, bathing both under the sun and in the sea, swimming, surfing, enjoying sea breeze and scenic beauty during sunrise/sunset are some of the recreational activities on the beach. Recreational value of a beach depends on factors such as cleanliness, virginity of beach, wave condition, slope of the beach, tidal range and size of the beach sediment. Suitability of a beach for recreational activities like bathing, swimming and surfing depends on the wave condition, the type of wave breakers and width of surf zone. Generally, sandy beaches are preferred as a recreational place/tourist destination. The sediment sample of sandy beach may contain pebbles, different sizes of sand particles, silt and clay. The preferred beach is the one in which the littoral sediment does not contain finer materials like silt and clay or in which their presence is insignificant. Beach sediments usually have a few relatively large particles covering wide range of diameter and many small particles within a small range of diameter. Typically, the littoral materials are sand with sizes between 0.1mm and 1.0 mm (USACE 1984). The size distribution of a sand sample from beach can generally be expressed either as well sorted or well graded. Driving in the beach is a passion for many. With the advancement in automobile engineering, beach driving has become one of the preferred recreational activities in selected beaches. A few beaches spread out in different continents are well known for beach driving. Daytona beach of Florida (http://www.floridarambler.com/florida- best-beaches/the-ultimate-scenic-drive-volusia-beaches/ ), South Padre Island Beach of Texas, Cape Hatteras National Seashore of North Carolina, Lancelin Beach, Wedge Island, Ledge Point Beach of Australia are some of the known drive-in beaches (www.4wdivingaustrilia.com/travel-western-austrilla). In India, beach driving is in vogue in a few beaches; Dhanushkodi in Tamil Nadu, Mandarmani in West Bengal and Muzhappilangad in Kerala are a few such beaches in India fit for driving vehicles. Over the years, adverse impacts of beach driving on coastal ecosystem are observed. Some of the adverse impacts reported are: (a) acceleration of erosion of shoreline and sand dune, (b) damages to the beach and sand dune vegetation, (c) prevention of new born hatchlings of sea turtles from reaching the sea, (d) sand compaction causing hindrance to making the nests by sea turtles and (e) effect on habitat suitability due to the lights of the vehicles at night (http://www.seaturtle.org/PDF/ Ocr/Anon_2010_USGSTechReport.pdf#page=7). To mitigate these impacts, different management plans have been formulated for the beaches. These plans often stipulate total ban on beach driving in some beaches or in a portion of certain beaches and also ban on driving during some periods of the year. Considering the safety of both the passengers and others frequenting the beach, driving is permitted subject to certain conditions. The conditions generally imposed on the vehicles include tyre pressure, number of driving wheels and their diameter and width. The environmental conditions of the beach considered in the management plan generally cover the wave conditions, storms and stages of tide. Depending on these conditions, a suitable zone will be generally demarcated for beach driving. Depending on the wave condition, beach slope and degree of exposure to the waves, littoral material undergoes continuous sorting and grading. The sorting takes place in such a manner that the coarse sediments are generally in zones where maximum wave energy is dissipated and fine materials find their place in sheltered areas. Along and across the beach face, grading and sorting of littoral materials vary with time. Wave climate of a place varies with the season and also with factors such as offshore slope and degree of exposure to the wave action. Size of beach sediments varies both along and across the coast and it also varies with time based on the wave conditions. Depending on the wave conditions, beach width changes; it recedes during severe wave active period and advances during mild wave active and clam periods. Waves cause changes in the beach slope and higher waves cause steeper beach slope. Mean diameter (d50) of the particle of the beach sediment is related to the slope of the beach face; the d50 of the sediment increases with the beach slope (Sunamura 1975). A few studies have been reported on drive-in beaches of Florida (http://www.seaturtle.org/PDF/Ocr/Anon_2010_USGSTechReport.pdf#page=7), Australia (Schlather et al 2008) and Israel (Kilot et al 2011). These studies mainly focused on the impact of beach driving on biotic system of the coast such as vegetation and marine species and physical system such as shoreline changes and sand dune erosion. Kerala State is situated on the southwest coast of India, between 8˚ 18′ - 12˚ 48′ N latitude and 74˚ 51′ - 77˚ 24′ E longitude, sandwiched between the Arabian sea on the west and the Western Ghats on the east and the State has 560 P.K. Abdulla et al. / Aquatic Procedia 4 ( 2015 ) 357 – 364 359 km long coastline. Eighty percent of Kerala coast is sandy in nature and about 360 km of coastline is reported to be prone to erosion (Kumar et al 2006). Many recreational and tourist destinations, both virgin and protected, exist along this coast. In Kerala, vehicular traffic is permitted in the “drive-in beach” at Muzhappilangad on the Malabar coast in southwest India. No restrictions are imposed on the vehicles to drive in this stretch. Ordinary two-wheel drive vehicles used on the hard surface are generally run on this beach. In most of the drive-in beaches, only four wheel drive vehicles with lesser tyre pressure (between 10 to 20 psi) are allowed (www.4wdivingaustrilia. com/4x4/my-hilux). For many years, Muzhappilangad beach experienced only normal changes during the intense wave period. However, during the southwest monsoon of the year 2013, a portion of the beach underwent severe recession which lead to the ban of vehicles in that stretch of the beach.