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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 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, , 673 571, India b Karunya University, Karunya Nagar, Coimbatore, 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 drive-in beach of 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, 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 , 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, 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. During the subsequent northeast monsoon and fair weather season, the entire beach regained its original width. A part of the beach which was badly eroded during the previous southwest monsoon remained unfit for vehicle driving. This paper discusses the changes experienced by this beach during the southwest monsoon of 2013 and also during the subsequent northeast monsoon and fair weather non-monsoon periods. An attempt has been made to understand the characteristics of the reformed beach, which is not fit for beach driving.

2. Study Area

The Muzhappilangad drive-in beach lies between 11° 46΄ 50˝ and 11° 48΄ 29˝ N and is situated in the district of Kerala State on the southwest coast of India (Fig 1). This stretch of 3 km long beach is bounded by headlands on both the northern and southern sides. On both the sides, two coastal water bodies separate the beach from the headlands. The inlet on the northern side is very narrow while that on the southern side is the estuary of Ancharakandi River having a width of 300 m. The river has a drainage area of 412 km2. The Muzhappilangad drive-in beach is one of the major recreational/tourist destinations of the Malabar region of Kerala State. It is well connected by road (NH 66) and rail network. Beside the headland on the southern side, an island which is located about 250 m off the coast having 300 m length and a rock outcrop also provide protection to the beach. Generally, three distinct seasons are experienced along the southwest coast of India, namely severe wave active southwest monsoon season (June-September), moderate wave active northeast monsoon season (October-December) and mild wave active non-monsoon season (January-May). This beach is situated in a micro tidal region, the range of spring tide being about 1.2 m. Irrespective of the seasons, waves approach perpendicular to the coast. Since this is a pocket beach, the alongshore sediment transport is insignificant and the material movement is mainly restricted to onshore- offshore transport.

Fig. 1 Location map of the study area 360 P.K. Abdulla et al. / Aquatic Procedia 4 ( 2015 ) 357 – 364

Waves with height less than 1.5 m are experienced on this beach even during the southwest monsoon. The monsoon wave causes offshore transport of the materials and during the northeast and non-monsoon seasons, the materials transported offshore are brought back to the beach. Generally, this beach is subjected to wave action normal to the shore. Depending on the season, different types of wave breaking (spilling, plunging and surging) are experienced along the coast. Mainly plunging and surging type waves break along the Kerala coast during the southwest monsoon. At Muzhappilangad, irrespective of the seasons, only spilling breakers are observed. After the erosion of 2013, plunging breakers are also observed at some portions of the eroded beach while spilling breakers are observed at the stretch of the beach on the southern side and eroded stretch of the beach on the northern side. Gradual rebuilding of the beach changed the wave breaking pattern. By the end of northeast monsoon season, the spilling breakers were observed along the entire length of the beach. On an average 100 vehicles frequent the beach every day. Apart from this, 40 fishing boats with outboard engine operate form the beach. There are also 3 resorts with a total of 15 rooms on this beach.

3. Methodology

Beach profiling at regular spacing (100 m) has been carried out along the coast during May 2011when the beach width has been maximum. Just after the erosion of September 2013, a beach survey is conducted. The extent of this survey was limited due to heavy wave breaking near the shore. The stretch of beach on the northern side had practically disappeared. Beach survey has been again carried out during May 2014 after the beach regained its width. Besides the survey of beach stretch, sediments are sampled at regular spacing along the beach and across the beach at different depths. Samplings have been carried out both in 2012 and 2014: October and December during the northeast monsoon season for 2012 and in May for 2014. A core cutter having a height of 13 cm with 2.5 cm dolly has been used for extracting samples from the surface, 45 cm and 90 cm below the surface. Samples could not be extracted where the sediment is in the submerged condition. Sampling is done along three rows nearly parallel to the shoreline. Considering the physical nature of the beach, more samplings are made during May 2014 for a few transects. Sampling has not been carried out during the ebbing stage of tide and also when the beach is flooded with high wave uprush.

4. Analysis and Result

The sediments are analysed for grain size distribution by dry sieving. Set of sieves used are 4.75mm, 2mm, 1mm, 0.5mm, 0.25mm, 0.100mm, 0.075mm and 0.040mm. Grain size distribution curves are drawn from which d50, d16 and d84 are obtained and σ is calculated. The beach at Muzhappilangad is having very gentle slope; the beach survey revealed that difference between the beach profiles at different locations is very small. The result of beach survey of May 2011 is presented in Fig 2 a. The variation of particle size of sediment sampled in 2012 from the beach surface, 45 cm and 90 cm below the surface are presented in Fig 3 a. For better representation of the sediment samples, both d50 and σ of the particle sizes are used. Typical gradation curves for the sediments sampled are shown in Fig 4 a; gradation curves are for sediment samples having (a) minimum d50, (b) maximum d50, (c) minimum σ and (d) maximum σ. Extent of beach survey conducted during September 2013 was limited due to heavy wave breaking near the shore and very limited beach width available particularly on the northern side; details are presented in Fig 2 b. Locations of erosion, type of breakers observed at different reaches of the beach subsequent to the erosion are also marked in Fig 2 b. The results of the beach survey carried out during May 2014, after the beach regained its width, is presented in Fig 2 c; the results show that the width of the beach in May 2014 is more than that of the beach available during May 2011. Along with the beach survey during May 2014, sediments are sampled at regular spacing along the beach and across the beach at different depths; locations of sampling sites are shown in Fig 3 b. The variation of the particle size (both d50 and σ) of sediment sampled from the beach surface, 45 cm and 90 cm below the surface are presented in Fig 3 b, 3 c and 3 d respectively. Based on the erosion experienced during September 2013 and the type of breakers observed subsequently, the beach can be divided into three zones, namely eroded northern portion with spilling type breaker, severely eroded portion with plunging breaker and seasonally changed beach with spilling breakers on the southern side. These zones are given in on Fig. 2 b. Gradation curves for typical beach sediments P.K. Abdulla et al. / Aquatic Procedia 4 ( 2015 ) 357 – 364 361 from the three zones sampled during 2014 are shown in Fig 4 b, 4 c and 4 d. The gradation curves are for sediment samples having (a) minimum d50, (b) maximum d50, (c) minimum σ and (d) maximum σ.

Fig. 2 Contour map of the beach at different periods

5. Discussion

The sediments of Muzhappilangad beach is uniformly graded fine sand with d50 range from 0.11 mm to 0.33 mm and σ value generally varies between 1.13 and 2.84. Pattern of sediment size distribution observed is similar at the surface and two other depths before the occurrence of recession. At a few locations, particularly near the rocky outcrop, the sediment samples with bigger particle size have been obtained, as indicated by higher value of σ. The σ values of less than 1.44 are obtained for 85 % of the sediment samples. Based on the erosion of September 2013 and subsequent changes in the wave breaking pattern, beach can be divided into three zones (Fig. 2 b). Core cutter sampling covered all these zones; details of sediments sampled from these three zones are given in Table 1. Details of sediments sampled within the respective zones during 2012 are also given in Table 1.

Table 1. Details of sediments sampled from three zones during May 2014 and 2012 During May 2014 (numbers) During May 2012 (numbers) Zone 1 Zone 2 Zone 3 Zone 1 Zone 2 Zone 3 Surface 4 12 18 6 3 8 45cm below 2 9 14 4 2 5 90 cm below 4 5 2 1 3 Total 6 25 37 12 6 16 362 P.K. Abdulla et al. / Aquatic Procedia 4 ( 2015 ) 357 – 364

3000 3000 d50 surface sample noo σ surfaces

3 2 1 0.15 Shoreline 1.22 0.13 1.20 0.111.13 0.11 1 1 1.27 0.121.720.19 1.19 1.64 0.18 0.16 0.18 0.14 Zone I 3 2 1 2 6 5 4 1.41 1.41 1.12 1.24 0.13 2.84 0.21 1.73 0.33 0.18 0.20 0.33 0.23 4 3 2 1 3 1.35 0.15 1.56 0.21 1.35 1.57 0.16 1.28 1.18 1.54 0.20 0.17 0.20 0.42 0.31 5 4 3 2 1 4 1.14 1.41 1.54 1.43 1.40 8 9 7 2000 2000 1.440.17 1.210.16 1.27 0.19 1.220.16 1.310.15 0.16 0.26 0.28 sample no Zone II 3 2 1 5 1.41 1.41 σ surfacesu d50 surface 1.26 σ 0.50. m depth d50 0.5 m depth 0.90.0 m depth d50 0.9 m depth 0.17 0.17 σ 2 1 1.19 1.08 6 0.20 N 3 0.17 0.18 7 1.15 2 1 N 1.25 1.10

Shoreline 12 11 10 0.16 0.17 0.18 3 2 1 8 1.15 0.17 1.180.17 1.17 0.13 1.08 1.25 1.74 1.16 0.16 1.19 0.14 1.18 0.19 0.21 0.20 0.16 0.17 0.16 1000 1000 5 4 3 2 1 9 1.14 1.20 1.11 1.05 1.08 15 14 0.20 0.18 0.17 13 3 1 10 1.33 0.16 Zone III 1.19 2 1.250.16 1.24 0.16 1.05 1.24 1.240.19 1.20 0.16 1.13 0.16 1.31 0.13 0.22 0.19 2 1 1.24 1.16 11

Shoreline

17 16 2.50 0.20 1.19 0.16 1.32 0.14 0 0 100 75 50 25 0 100 75 50 25 0

Fig 3 a Variation of d50 and σ of beach Fig 3 b Variation of d50 and σ of beach sediment during 2012 Oct-Dec sediment during 2014 May

3000 d50 45cm4 depth 3000 sample no d50 90cm9 depth

σ 45cm45 depth sample noo σ 90cm90 depth

Shoreline 0.21 Shoreline 1 1 1 1.18 1 0.18 Zone I 3 2 1.24 1 2 Zone I 3 2 1 2 0.32 0.30 0.22 0.31 4 3 2 1 3 4 3 2 1 3 1.46 1.31 1.27 1.40

0.19 0.38 0.41 0.38 0.41 0.29 5 4 3 2 1 4 5 4 3 2 1 4 1.53 1.95 1.29 1.77 1.23 1.94 2000 2000

036 Zone II 0.36 5 0.32 3 2 1 Zone II 3 2 1 5 1.56 1.10 1.35

0.16 2 1 1.27 6 2 1 6 3 0.17 0.28 7 2 1 3 2 1 7 N 1.43 1.10 N

0.17 0.19 3 1 0.19 2 8 3 2 1 8 1.14 1.24 1.13 0.19 0.19 0.19 0.15 1000 5 4 3 2 1 9 0.21 0.19 0.19 1000 1.16 1.10 1.15 1.11 5 4 3 2 1 9 0.16 0.17 0.19 1.05 1.08 1.05 3 2 1 10 Zone III 1.14 1.07 1.17 Zone III 3 2 1 10

0.19 0.20 2 1 11 0.19 1.17 1.10 2 1 11 1.23 Shore line Shoreline

0 100 75 50 25 0 0 100 75 50 25 0

Fig 3 c Variation of d50 and σ of beach Fig 3 d Variation of d50 and σ of beach sediment during 2014 May sediment during 2014 May

P.K. Abdulla et al. / Aquatic Procedia 4 ( 2015 ) 357 – 364 363

The range of values for d50 and σ of the sediments sampled from the three zones prior to the erosion (2012) and after the beach is reformed (May 2014) is summarised in Tables 2 and 3 respectively.

100 100 Zone 1 84 84

5050 5050 d50 min, σ min [1 Surface] d50min , σ min [2 (1) Surface ] Finer (%) d50 max [4 Surface ] Finer (%) d50 max [1 (1) 45cm ] σ max [5 Surface] σ max [2 (2) Surface] 16 16

0 0 0.01 0.1 1 10 0.01 0.1 1 10 Particle size(mm) Particle size(mm)

Fig 4 a Gradation curve for typical sediment samples:2012 Oct- Fig 4 b Gradation curve for typical sediment samples:2014, Zone 1 Dec

100 Zone 3 84

50 50 d50 min [9 (1) 45cm ]

Finer (%) Finer d50 max [7 (1) 45cm ] σ min [9 (2) Surface ] 16 σ max [8 (1) Surface]

0 0.01 0.1 Particle size(mm) 1 10

Fig 4 c Gradation curve for typical sediment samples:2014, Zone II Fig 4 d Gradation curve for typical sediment samples: 2014, Zone III

Table 2. Range for d50 (mm) for the sediment samples collected from the three zones during 2014 and 2012 May 2014 During October-December 2012 Zone I Zone II Zone III Zone I Zone II Zone III Surface 0.14-0.18 0.16-0.42 0.16-0.22 0.11-0.33 0.16-0.19 0.13-0.20 45cm below 0.18-0.21 0.19-0.41 0.15-0.28 0.12-0.21 0.15-0.16 0.14-0.19 90 cm below - 0.29-0.41 0.19-0.21 0.16-0.18 - 0.13-0.19

Table 3. Range for σ for sediment samples collected from the three zones during 2014 and 2012 May 2014 During October-December 2012 Zone I Zone II Zone III Zone I Zone II Zone III Surface 1.12-1.41 1.14-1.54 1.05-1.74 1.13-2.84 1.21-1.44 1.15-2.50 45cm below 1.18-1.24 1.10-1.95 1.07-1.43 1.27-1.72 1.22-1.31 1.16-1.32 90 cm below - 1.23-1.94 1.05-1.23 1.57-1.64 - 1.13-1.31

It can be seen that the particle size of the beach sediments has undergone significant changes after the erosion with respect to that prior to 2013. The changes are more noticeable in zone II than zone I. However, in zone III, the change in values of d50 and σ is very nominal. From Figs 3 b, 3 c and 3 d, it can be seen that d50 and σ for sediments sampled towards the shoreline have undergone major changes in comparison to that existing prior to September 2013. 364 P.K. Abdulla et al. / Aquatic Procedia 4 ( 2015 ) 357 – 364

6. Conclusion

The drive-in beach at Muzhappilangad was having uniformly graded fine sand before the changes took place in wave breaking pattern. The stretch was protected by the headlands on both sides and the island and the rock outcrop on the southern side. Wave action normal to the coast results in onshore-offshore movement of the sediment. Mild wave action, gentle shore slope and low wave steepness result in spilling type of wave breakers on this beach. These are the factors which contributed to the formation of a unique beach which behaved like a firm surface. Severe erosion at one stretch of the beach caused changes in the wave breaking pattern. The stretch where plungers are observed, the sediments have higher values for d50 and σ. Smooth driving of two-wheel drive vehicles was not possible in this stretch of the beach due to higher size of sediment particle. Seasonal and normal erosion during the monsoon months with spilling breakers does not cause any change to the beach sediment size as indicated by the values of d50 and σ and hence the characteristics of this unique beach have been maintained. The study highlights the impact of breaking wave pattern on particle size of sediments of Muzhappilangad drive-in beach.

Acknowledgement

This work is part of the project entitled ‘Study on the Characteristics of the Drive-in Beach at Muzhappilangad, Kerala’ funded by Kerala State Council for Science Technology and Environment (KSCSTE). Authors are thankful to the Executive Director, CWRDM for providing all support for the study and for the permission to publish this paper.

References

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