Wave and Littoral Processes at Thengapattanam Coast, Kanyakumari District, Tamil Nadu State, SW India

Wave and Littoral Processes at Thengapattanam Coast, Kanyakumari District, Tamil Nadu State, SW India

^*1C. Hentry, ¹G.D. Gena and ²S. Saravanan

¹St. Jude’s College, Thoothoor – 629 176, Kanyakumari Dist, Tamilnadu, India

²Centre for Geo – Technology, Manonmanium Sundaranar University, Tirunelveli – 627 012. Tamilnadu, India

*Corresponding author

DOI: https://doi.org/10.51584/IJRIAS.2024.909048

Received: 09 September 2024; Accepted: 17 September 2024; Published: 21 October 2024

ABSTRACT

The field investigations were carried out on the beach profiles, breaking wave parameters and longshore currents for a period of 25 months from December 2006 to December 2008 to study the beach dynamics of Thengapattanam coast, Kanyakumari district, Tamilnadu state, SW India. The Thengapattanam beach is well known for its long history, estuary, tourism, manmade structures and fishing activities. Monthly measurements were prepared on littoral environmental observations (LEO) and beach level variations.  Longshore sediment transport rates were estimated based on the observed data. The estimated annual gross longshore sediment transport rate was higher due to recent manmade structures   and the net transport was towards southerly direction . The beach profile level was lowest in July and high in April and the variation was   35 m. The total volume of sand transported was 840 m³/yr during 2007 and 710 m³/yr during 2008. The wave heights varied between 0.4 to 2.5 m during 2007 and 0.45 to 1.8 m during 2008, whereas wave period was between 8 sec to 15.5 sec and 7 sec to 21 sec for 2007 and 2008 respectively. The study concluded that the beach is experiencing significant erosion. Thengapatanam beach   is being subjected to erosion phase during both monsoon seasons and get stable profiles by fair weather seasons. Longshore currents were stronger in June, July and August and steady during rest of the year. The net southerly transport was 1.2*10⁶ m³/yr during 2007 and 0.577*10⁶ m³/year during 2008. The volume variations of the sediments, an account of accretion/erosion were estimated considering the January 2007 profile as the base reference over which the values of other months were compared. The study area is highly vulnerable due to its erosion and other factors.

Keywords: Longshore current, sediment transport, beach profile, LEO, breaking waves etc.

INTRODUCTION

Inlets are important economically to many littoral states because harbours are often located in the back bays, requiring that the inlets are maintained for commercial navigation. A better understanding of inlet sedimentation patterns and their relationship to tidal and other hydraulic processes can hopefully contribute to better management and engineering design. Beaches and sediment movement along the shore have been subjects of popular and scientific interest for over a century. Beaches are popular recreation areas and of vital economic importance to many states [1]. Beaches are critical buffer zones protecting wetlands and coastal plains from wave attack. One feature of coastal areas that is often studied and analyzed are the profiles of beaches, cliffs and coastal landforms. These cross sections through coastlines can give a good idea as the changes that can occur over time at one point on the coast, either in the shape of a beach or cliff, or on its size and volume. Careful examination of the sediment transport pattern is very essential to maintain   the balance and the stability of the coastline.

India has a long coastline of over 6000 km along the mainland in addition to that of the Andaman and Nicobar Islands in the Indian ocean and Lakshadweep islands in the Arabian sea. The vast coastal zone has been playing a major role in the economic development of the country since ancient times by its contribution to sea trade, fishing, ocean industry and human settlement. But coastal   ecosystem is under threat due to anthropogenic activities, increased human settlement, industrial pollution, manmade structures etc. The geomorphology of beach is controlled mainly by the wave characteristics and the nearshore sediment transport. The hydrodynamic process in the surf zone is quite complex due to wave breaking, presence of   longshore and onshore – offshore currents, littoral sediment transport, erosion or  accretion of beach   sediments etc. Responding   to the   various   forces acting in the surf zone, the coast readjusts itself and tends to be in a   dynamic equilibrium.  Longshore current plays a predominant role in transporting the sediment in the beach. For practical purposes, the average longshore current measured in the surf zone would be sufficient for estimating the sediment transport rate.

With regards to the measurement of beach profiles, Delgado and Lloyd (2004) describe  in their paper  one of the simplest  methods of measuring  beach profiles[2]. Cooper et al. (2000)  briefly explained the history  of beach  profile measurement   in their paper on the measurement, theory and analysis  of beach profiles [3]. Pickett   et al. (1997) describes the application  of the  model  in the of the  the  beach profiles  of the Bay of Plenty, New  Zealand [4]. Krause   and Soares  (2004)  described  a beach profile  monitoring  programme  for the  state  of  Para  in northern Brazil , which was the investigation of coastal  morphodynamics  to be undertaken  in an  area  of extensive mangrove  forest [5].  Lacey  and  Peck (1998)  documented  morphological   changes occurred on  on the beaches  of   Rhode Island  by observed term periodic  cycles [6].  Saravanan and Chandrasekar (2010) studied the monthly and seasonal variation in beach profile along the coast of Tiruchendur and Kanyakumari, India [7]. Larson et al. (2000) analyzed the relationship between wave action and beach profiles [8]. The  longshore  current    velocity  varies  across the surf zone, attaining the maximum value close to the wave breaking point [9]. The sediment transport between Kanyakumari  to Trivandrum  is  southerly  from May to  December  and northerly  from January to  April [10]. Wind, waves and tides are the important factors responsible for the movement of material on the beach and the resultant sediment distribution [11]. The variation in grain size for any type of beach is primarily a function of variation in wave height and to a lesser degree, the wave period [12]. The textural parameters, in addition to the degree of sorting, also reflect the mode of transportation and the energy levels of transportation media. The grain size and grain size distribution of sediments can be utilized for assessing the energy conditions prevailing along the coast. Nevertheless, grain size parameter provides an insight, into the mode of sediment transportation and deposition. The references used to study beach profile studies and earlier profile studies at nearby study area.

The main objective of this paper is to monitor the beach profile changes, to estimate longshore current and sediment transport   from measured wave data and Littoral Environmental Observation (LEO) data and to ascertain what changes have occurred in Thengapattanam  beach profile shapes   on a temporal scale using beach profile data  from December  2006 to December 2008. Also, the aim of the present investigation is to determine statistically the significant variations in grain size distribution of the beach sediments along the location under study. In order to get a comprehensive picture about the seasonal changes in the size characteristics of the sediments along the beach, average moment measure statistics viz. mean, standard deviation, skewness and kurtosis were computed.

Study area details

Kanyakumari is the smallest district situated in the southwest of Tamil  Nadu, South India   with a land spread  of 1,684 km². It has almost all ecosystems – forests, wetlands, freshwater resources, marine etc. The coastal ecosystem   of this district comprises 68 km in length and is studded with 44  44 coastal  villages. Since this district is situated at the extreme south of the Indian subcontinent, the coastline is formed nearly by the three seas, namely the Arabian Sea, the   Indian Ocean and the Bay of Bengal. But the main part of the coast faces the Arabian Sea. The coastal landscape of Kanyakumari District is mainly composed of beach ridges of rocky, sandy, clay in salt pan region and swampy nature in the estuarine regions. The coastal geomorphologic features observed in the district are Teri sand, sand dune, sandy plain, pediment, river side plain, flood plain, alluvial plain, deltaic plain, estuary, beach ridge, swampy, mudflat, saltpan, lagoon, sandbar, creek, rock shore, sandy beach, cliff, tidal flat, cusp, groins, off shore hillocks etc. The 68 km long coast has a heavy concentration of fisher folk, almost one village per 1.5 km. Coastline of Kanyakumari coast is exposed   to relatively  higher waves  than the rest  of the  Indian  coast  due to its direct  exposure  to  the  Indian  ocean . The oceanography of this region is controlled by three different seasons a) Southwest monsoon (June to September) b) Northeast monsoon (October to December) c) fair-weather period (February   to May). In the Indian Ocean mixed tides are mainly semi-diurnal type. The tidal range  along  the  west  coast  of   India  increases  from  0.65 m  to  0.76 m towards  south.

The study area, Thengapatanam beach is a beautiful town located in latitude  N 8⁰ 14^’27.1’’ and longitude E 77⁰10’ 7.3’’ on the shores of Arabian Sea in the southern part of  Kanyakumari district in Tamil nadu. It is an open coast with deep in bathymetry and the transect of the proposed research area is shown in fig 1. The history of this beautiful coastal town dates back to more than 2000 years to the reign of Chera Kings.  It was, then an important port of Chera Nadu, when trade relations boomed with the Middle East and the Arab world.  There was direct cargo boat service between Thengapattinam and other foreign maritime towns around the world.  Part of the culture and tradition found here was inherited through its trade relations with the Arab world.  The king Cheraman Perumal had passed through this tiny town when he went to Mecca to embrace Islam after witnessing the moon splitting miracle.  It was part of the Travancore State until 1956 before it merged with Tamil Nadu. This Muslim town has a Juma Masjid known as Valiya Palli, which is more than 1200 years old. It is a coastal town which is 35 km away from Nagercoil, headquarters of Kanyakumari District and 45 km away from Trivandrum, capital city of Kerala.  It shares borders with Mullimoodu and Erayummanthurai on the western side, Panankalmukku and Mulloorthurai on the east, Amsi on the north and the Arabian Sea on the south.  It is well connected with nearby villages and town by road and waterways.  It is a flat, plain land with intermittent rocky hills – Chentapalli rock – on the eastern side and Aarttupalli rock on the western side. The Kovalam – Colachel Canal, popularly known as AVM Canal (Ananda Victoria Martanda Varma Canal) which passes through this town linking up to Kanyakumari was encroached by settlers.  This waterway was operation from Mandaikadu to Poovar 70 years ago.  In some places it is filled with coconut trees and suffered encroachment.  AVM Canal merges with Kuzhithurai River at Thengapattanam and known as Valliyar.  AVM canal which connects the Thengapattinam estuary of Thamiraparani River, Kanyamuari District and Neyyar river Estuary at Poovar of Neyyatinkara, Kerala.  The AVM canal runs along the west coast. The canal well served the freshwater needs of the local people. The drainage channels from the paddy fields and AVM canal are the main sources for the flow of sewage and domestic wastewater into the estuary. AVM canal is used for retting activities round the year (www.kanyakumari.nic.in).

During Southwest and Northeast monsoons, it overflows and causes much damage to the lives and properties of those who live on the banks of the river. During the rest of the period the river is almost dry. The alluvial soil along the coastal strip is well adapted for the cultivation of paddy and coconuts.  “Thengapattinam”, ‘Thennaipattinam” and “Thenpattinam” are the other relevant names of this town, it is called so because of the dense coconut groves found everywhere here. Thengapatnam estuary is one of the major estuaries in Kanyakumari District, Tamil nadu as shown in plates 1a,b. It is a bar-built estuary and sand bar is a permanent barrier, which prevents the entry of sea water during post monsoon and pre monsoon season. Near shore bathymetry is depth with   19 m from   200 m distance from the shore.  The terrain comprises largely of Precambrian crystalline rocks of charnockites, khondalites and migmatitic gneisses. According to Raju and  Singh [13], Thengapatanam hinterlands’ have radioactivity of  1.87 Gy/h and Thengapatanam beach sector 0.64 Gy/h. Now, Government  of Tamil nadu  constructs  a fishing harbour  in  the Thengapattanam  estuary is underway. Therefore the observations will be more useful to monitor the possible coastal changes resulting during and after the construction of fishing harbour.

MATERIALS AND METHODS

The beach profiling measurements were made out at Thengapatanam beach every month from December 2006 to December 2008 at the lowest tide level. So that the maximum lengths of the beach cross section was exposed for the measurement. At times, inner bars were accessible and the measurements were carried out. The stake and horizon method [14] was adopted to measure the sand level at the transect with the fairly fixed reference point. The profile direction was kept perpendicular to the coast and all the measurements made at the station.  Monthly  changes    for  25 months  in  beach  levels were  measured  at  the study area  at every 5m  interval  along  a transect  from  backshore  dune  to seaward  till  1m water depth during  the low tide. Surveyor’s dumpy level   and a graduated staff   were used for   measuring beach levels. Heights  of 10 consecutive breakers were  usually  measured  and the  average of  them were  noted as significant  wave height  at breaking. Total  time required  for  10 waves  to break  was noted  using a  stop watch  and the average  was considered  as breaking wave  period. Long shore current velocity and direction were measured by using current meter.  Based on the data collected, the long shore sediment transport rates were computed using the Walton’s   equation [15],

Q = ( 1290 ρgH_bWVC_f ) / (0.78 (5л/2)(V/V_o))

Where,  Q is the longshore  sediment  transport  rate  in m³/year,  ρ is density  of sea water  = 1025 kg/m³, g – acceleration  due to gravity = 9.81 m/sec²,  C_f  is the  friction  coefficient  = 0.01, H_b is  breaking wave height in meter, W  is  surf zone  width  in meter, V is the measured  longshore  current  velocity  in m/sec  and  V/Vo  is the  theoretical dimensionless  current velocity = 0.4  [16]. From  the   data  collected  during  these  surveys, the  monthly  and  seasonal  beach  profile  variations  are  graphically  represented  to show  the variability  in beach  profile  configuration. From  these  data, changes  in the  volume  of  sediments  are  calculated  using  a  computer  package  to  scrutinize  the  temporal  variation  in  figs 2 a,b. [17].

Monthly beach sediment samples were collected over a period of 12 months (Dec 2006 to Nov 2007) from the berm, low tide, mid tide and high tide regions of  the transect during low water level when the beach exposure was maximum above the water line. Total of 48 (12*4) samples were collected and analyzed for the present study. Sieve analysis was carried out to study the grain size distribution. Beach samples were subjected to size analysis by the simple sieving method. The samples were collected by scoop sampling. Approximately 1 kg in weight was washed free of salt, silt and clay and finally oven dried. From that 100 gm was separated by the conning and quartering method. Shells and shell fragments, if any present in the samples were separated by hand-picking method, as the presence of this would distort the trend of analysis. The samples were then sieved for 15 minutes in a semi automatic, motor driven mechanical Ro-Tap sieve shaker using a set of standard ASTM sieves (mesh nos. 40, 60, 80,100,120,140,170,200,230 and pan). The weight of each fraction representing a particular grain size was measured using an electronic balance. The graphic mean, median, standard deviation, skewness and kurtosis were calculated based on the formula of Folk and Ward [18].

RESULTS AND DISCUSSION

Beach profile studies

The variations in monthly beach levels at Thengapatanam beach are shown in Table 1, 2 for the years 2007 and 2008 respectively. The drawings  of beach  level variations for   25 months  from December  2006  to December  2008 for  SW, NE monsoons and fair weather seasons  during  2007, 2008 years   are given in  figs (3 – 10). Beach  level  variations  at Kolachel  were presented  earlier  by  Jena and  Chandra Mohan [19]  as  beach level was low in  September  and high in  April. Kaliasundaram et al.[20]reported that the erosion was taking place at Colachel at a rate of 1.2 m/year. Relative  changes  in the  volume of sediment  per meter  length of the  beach up to   1m water depth  at  Thengapattanam  were  estimated  and presented   in  table 3 .Volume  changes  over an annual cycle  were  estimated  at   840 m³/yr for the year  2007  and  710.64 m³/yr     for the  year 2008. The volume changes of the study area for months are given in fig 11.

The beach level   is at the lowest in July and August for both years   and at the highest in March and April. Normally beach levels  are at  the  lowest  in the  southwest monsoon   period  for  majority of west coast  beaches  also found to continue their erosion  processes during the northeast  monsoon  period also . But, the  present study  established  that   the  variation  of  beach   levels over an  annual cycle  showed that the  Thengapatanam beach is experiencing significant erosion. The beach profile is highly influenced by estuary connected by Thamiraparani river mouth. The  beach width ( m) , mean  slope  angle (deg) and  total  cross sectional  area (m²/m)  of  the  beach  for  various months are given in table 4. The maximum  beach width  per  meter  of  beach  was determined  as  59.88 m  during  July 2007  and  50.14 m during  March 2008.The minimum beach width  obtained  as 24.23 m in July  2007 and  26.31  m in  June  2008. The mean slope of the beach Vs months are given in fig 12. The slope variation has maximum during June and July months and minimum  during April. The high slope angled Thengapattanam beach is given in plate 2.

Breaker characteristics

The  variation  of  breaking wave  height, period and  the width of  a surf zone   are  measured  and presented  as Littoral Environmental Observations in  table 4.The maximum  wave height  is measured  as 2.5 m in June  2007  and  1.8 m in July  2008. The wave height remained below 0.8 m in the fair weather    season.  Usually the study area has plunging breaker type except November and December which have surging wave type. The variation of wave height for different months is given in fig 13. The  wave period  persisted  high  during  the southwest  monsoon  season  months  June  to  August  and  spilling  breaker occurred during    January  and February. The relation connecting   between period Vs month is given in fig 14. The surf zone width was larger during June to August at about 60 to 100m. The surf zone width was only about 5 to 20 m during November to February. The study of surf zone Vs month is given in fig 15. The floodplain region and wave cut platform of study location is given in plate 3 and plate 4.

Wave refraction 

Wave refraction phenomenon is an important process responsible for effecting changes in coastal configuration. Based on wave atlas, wave refraction pattern prepared for the Indian coast, the predominant deep water wave direction is 210⁰ with reference to north with period 8 sec.  The bathymetry points are collected by NIO was considered for extracting digital bathymetry using Arc Map software.  Numerical refraction procedure is adapted from Mahadevan [21]. Referring to Fig.16 for waves coming from 210⁰ during southwest monsoon, convergence of wave orthogonal or concentration of wave energy is observed along the stretch of Muttom, Kadiyapattinam and Enayam.  Immediately adjacent to the convergence zone, there is a wave divergence zone in the Colachel and Thengapattanam and south of  Muttom.  The sediments, eroded in the wave convergence zone, find the way to get deposited on the beach situated along the wave divergence of region.  In southwest monsoon period the refracted wave orthogonal for the SSW direction and for the periods 8 sec is shown in fig 16.

Longshore current

Longshore currents are generated due to waves breaking at an angle to the shoreline. The shape of the coastline, beach face slope, estuary, nearshore profile, bathymetry, presence of sand bars and shoals significantly influence the distribution of longshore currents. The measured    longshore   current velocity and direction are shown in table 4 and longshore current for months are drawn in fig 17. The study indicates that the average longshore current velocity   remains 0.2m/sec in the fair weather season. The  variation  in the  longshore  current  velocity  and  direction  is expected to occur  due  to the change  in coastal  geomorphology   and nearshore  bathymetry. The study also indicates that the Thengapattanam beach is quite sensitive to the both (SW & NE) monsoons. The variation  in the  near shore   bottom  topography  , variation  of  breaker height , presence  of   wind set up , rip currents and manmade  structure like  RMS wall etc. plays an important  role  in the formation of   longshore  current. Longshore current was predominantly in the southerly direction except months of   January to April.  Anyhow the difference in the  distribution  of longshore   current  direction  could not  much   influence  the redistribution  of littoral  sediment  within the  study region,  leading  to erosion  of the  coast over an  annual  cycle.

Longshore sediment transport

The longshore sediment   transport rates are estimated   using   Walton’s equation and   presented in table 4. Earlier  the  annual  longshore sediment transport  rate of Colachel   from April 1995  to April  1996  was  estimated  at  0.9*10⁶ m³/yr and  net  transport was  0.3*10⁶ m³/yr by  Jena and Chandramohan  [19]. Hentry et al.[22] assessed the longshore sediment transport rate relatively high, about 0.9*10⁶m³/yr during 2007 and 0.3*10⁶m³/yr during 2008. Now  the  present  study  assessed  the longshore  sediment  transport  rate  of Thengapatanam coast is,  about  1.17* 10⁶  m³/yr  during  2007  and  0.57*10⁶ m³/yr  during  2008.  The longshore sediment   transport rate was lowest in November, January and February. Chandramohan and Nayak [23] reported that the annual net transport at the tip of India peninsula near Kanyakumari was negligible and southerly direction. Now, the present study  also  indicates that the net sediment transport near Thengapatanam is in the southerly direction.  The presence of estuary in the  Thengapatanam coast  plays a very important  role in the coast . The damming across the Thamiraparani river and river bed sand mining in the estuarine region blocks the sediments to reach the coast which maintains the coast as the erosional   coast in the region. Also the manmade structure RMS wall enhances the erosion in the long run. The sediment transport rate for various months   is given in fig 18.

Grain size analysis

The monthly variation of graphic mean, standard  deviation , skewness  and  kurtosis were calculated for the samples from  different locations are presented in fig 19 & fig 20 for  mean size, fig 21  for sorting,  fig 22 for skewness   and  fig  23 for Kurtosis. The monthly grain size analysis of sediments of   all   locations in the entire study area is given in table 5. The mean values of grain size analysis of   sediments for all 12 months are given in table 6. At Thengapattanam, the average value of the mean grain  size  shows the presence of’ medium size sand to coarse size  (0.27 mm – 0.57mm) except in May where fine sand is present (0.21 mm). The maximum grain size in June, July and October shows the severe erosion during these months. The sorting values show moderately well sorted to moderately sorted nature during SW monsoon. The samples show negatively skewed nature during most of the period except during November and December, they are symmetrical. This shows that the beach in general undergoes erosion during the period of study.

CONCLUSIONS

The  study  of  beach  profiles  over time  highlights  the  annual  variations  in the beach  shape  and the level  caused  by varying  wave  and weather  conditions.  The  correlation  between  the beach  profiles and  a number of other factors  including wave height, wave period , surf zone width,  weather  conditions  and  human interventions   are studied. The present study also brings out the nature of the wave climate acting on the coastline. The net sediment transport near Thengapattanam is in the southerly direction. From the monthly wave breaker height   analysis, it is evident that this  beach has all typical characteristics of a high energy beach with the onset of monsoon, an increase in southerly drift  value is observed . Factors like steep slope of the shelf and open sea conditions must lead to the accumulation of the coarse grained sediment in the foreshore region of the study location. The foreshore samples are negatively skewed, indicating the prevalence of high energy conditions. The RMS walls put along the coast enhance the erosion recently. The erosion is very high in all months except March to May during 2007 and 2008. The damming of Thamirabharani River causes sediment starved shoreline; low lying topography and highly damaged toe of the RMS (Rubble Mount Sea) wall in the beach are the major reasons for very high erosion hazard of this beach. The present study indicates that Thengapatanam  beach is erosional over  the annual cycle. The heavy mineral deposits  ilmenite presents  in the  mid tide  region  and  garnet  in the  low tide  region  of the  study area. In Thengapattanam, seawalls are fully slumped. Many sections of the seawall are getting severely damaged during every monsoon. The same situation is repeated year after year. Additional stones are stacked where ever the seawalls get damaged. In many places the seawalls are sinking. In some places seawalls have collapsed during monsoon and got submerged in the sand during fair season. The huge  RMS wall is shown in plate 5 . The studies have revealed that this coast has been showing eroding tendencies for the last 30 years. The coast which maintained a wide beach is now devoid of beaches. Coastal armoring structures cause reflection in wave energy, which can increase seaward erosion of these structures. High wave energy condition and steep slope close to the seawall causes high energy dissipation on the seawalls. Ramanthurai – Thengapattanam Arayan thope is proposed to be protected from erosion with groin structures. Beach nourishment is recommended at the down drift end to prevent erosion of the adjoining area. While construction of dams across rivers is unarguably necessary for irrigation and electricity generation, there should be adequate provision for letting water through the downstream courses at least during peak flows, so that deltas are not starved of   the much needed sediment inputs for coastal stability. Similarly, remobilization of sediments that are currently trapped in reservoirs may also be accomplished through appropriate engineering methods, which would have a double benefit of maintaining the reservoir capacity as well as sediment budget at the deltas and littoral drift in the coast.

ACKNOWLEDGEMENT

The authors are thankful to The Joint Secretary, University Grants Commission, SERO, Hyderabad for providing the financial assistance under Minor Project Scheme (MRP.812/05, Link No.1812.0).

REFERENCES

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Table 1 Beach Profile Survey (m) at Thengapattanam (Dec 2006 to Dec 2007)

Table 2 Beach Profile Survey (m) at Thengapattanam (Jan 2008 to Dec 2008)

Table 3 Beach morphology study  at Thengapattanam

Table 4   Littoral  Environment  Observation at  Thengapattanam

Table 5   Grain size analysis at Thengapattanam (Dec’2006 – Nov’2007)

Table 6 Mean  grain size analysis of sediments along Thengapattanam (Dec’06 – Nov’07)

Fig.1 Location of the Study area

Fig 2 (a) Home Page of the Sand Volume Calculation Package

Fig 2 (b) Options Available in the Sand Volume Calculation Package

Fig 3 Beach profile Survey along the study area (2007)

Fig 4 Beach profile Survey along the study area (SW Monsoon 2007)

Fig 5 Beach profile Survey along the study area (NE Monsoon 2007)

Fig 6 Beach profile Survey along the study area (Fair weather 2007)

Fig 7 Beach profile Survey along the study area (2008)

Fig 8 Beach profile Survey along the study area (SW Monsoon 2008)

Fig 9 Beach profile Survey along the study area (NE Monsoon 2008)

Fig 10 Beach profile Survey along the study area (Fair Weather 2008)

Fig 11 Beach Sediment Volume changes along the study area

Fig 12 Beach slope angle along the study area

Fig 13 Wave height along the study area

Fig 14 Wave period along the study area

Fig 15 Beach surf zone width along the study area

Fig 16 Wave Refraction pattern along the West Coast of India (SSW 8 secs)

Fig 17 Longshore current along the study area

Fig 18 Sediment transport along the study area (+ Southerly direction, Northerly direction)

Fig 19 Mean size of sediments (mm) along the study area (Dec’06 – Nov’07)

Fig 20 Mean size of sediments (Ø) along the study area (Dec’06 – Nov’07)

Fig 21 Mean sorting of sediments along the study area (Dec’06 – Nov’07)

Fig 22 Skewness of sediments along the study area (Dec’06 – Nov’07)

Fig 23 Kurtosis (Ø) of sediments along the study area (Dec’06 – Nov’07)

Plate 1 a, b Estuary regions in the study area

Plate 2 High slope angled beach at Thengapattanam

Plate 3 Flood plain at Thengapattanam (SW monsoon)

Plate 4 Wave cut platform shows heavy mineral deposit layers  in the  study  area

Plate 5 R.M.S. Huge Wall enhances the erosion at Arayan  Thope,  Thengapattanam