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CHAPTER IV

COASTAL GEOLOGY & GEOMORPHOLOGY

4.1 INTRODUCTION

The present chapter deals with detailed study on the coastal geomorphology of

Kanyakumari coast through the versatile satellite technology. The Coastal Geomorphology

and coastal processes and geomorphic features have been studied by various researchers,

leading to the recognition and understanding of the evolution of various coastal landforms

and beach processes. Geomorphology is defined as the science of land formations of the

earth ultra structure. The analysis of the surface forms of the earth is a direct form of interpre-

tation of the land correspond to earth features through space images. Moreover this chapter

deals with the genesis of relief forms of the surface of the earth’s upper crust. Certain natural

causes are responsible for the forms of the surface of the earth. Recently, as part of coastal

zone management strategy, these studies were carried out for sustainable use of coastal re-

sources and to identify the coastal vulnerability areas. Many Geomorphologists are partic-

ularly interested in the potential for feedbacks between climate and tectonics mediated by

geomorphic processes. Coastal landforms are influenced and controlled by proximity to the

sea. Such kind of landforms are continuously modified or changed by various factors like

erosion, transport and deposition by waves, tides and ocean currents. And these processes

made up of coastal landform features such as coastal dune, mangroves, salt marshes, wet-

lands, etc., are not only producing the resources, but also safeguarding the environment

of the coastal zone. Understanding of seashore- land interaction features such as shelf,

shore, coast and beach characteristics is essential to achieve this.

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4.2 Indian coast

In the Indian context, the West coast is characterized by both emergent and submerg-

ing features owing to long-term changes in sea level, climate, lithology, structure and neo-

tectonic movements. Nevertheless, submerging features like estuaries, marshes, tidal

swamps, mud flat deposits, spits and bars, etc. dominate some of the coastal regions.

4.3 Kanyakumari Coast

One of the remarkable differences of the West coast from East coast is that it is devo-

id of deltas. Over population along the study area coast has placed a high pressure on the

landscape, and yet humans are drawn to extend their activities to the coastal areas in order to

meet the needs for industrial, agricultural, tourist, fisheries activities and also for residential

purposes. Kanyakumari coast, at the South West part of India is characterized by wave domi-

nated coast. The coast receives normal rainfall (>1400mm/year) and semi arid to humid cli-

matic conditions occur along the low altitude to high. Generally the study area falls in ex-

treme temperature (32ºC) on summer. The coastal tract is highly dissected and the landscape

is the result of extensive denudation under the tropical climate during Tertiary (Subra-

manian & Rao, 1984). The west coast is opined as tectonically stable. Therefore, sea level

change observed along the coast is chiefly due to glacio-eustatic impact. The barrier spit

developed along the West coast of India denotes the emergent nature of the coast. Continen-

tal shelf, in general means, the marine floor between the shoreline and the submarine contour

of 100 fathoms (183m/600ft). Shelf around India covers an area is three million sq.km. The

continental shelf bordering the West coast of India is remarkably straight which was re-

sulted from faulting during the Pleistocene (Krishnan, 1960).

Along the West coast from Kanyakumari to the North, the shelf gradually widens

from about 60- 80 km to over 320 km off Gulf of Cambay region in the North. The topogra-

phy of the inner shelf along the West coast of India is relatively uneven. Shore parallel sand

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rich deposits in the continental shelf of Kumari coast have been reported earlier. The offshore

bars are common features along the gently sloping shelves where the sediments are churned

up and piled landward by the shore approaching waves. Offshore bars are not likely to

grow in shelves, which are uneven or inclined (Ahmed, 1972).

This chapter gives attention to the study of the entire coastline by Remote Sensing

technique since the conventional, continuous and simultaneous survey method which is

time consuming and expensive. Besides the Remote Sensing technique, because of synop-

tic view and repetitive coverage providing enormous spatial, spectral and temporal informa-

tion, it has been accepted as a potential tool to understand the coastal landforms and dynamic

nature of coastal processes. Indian Remote Sensing satellites have played a valuable role in

providing information on various components of the coastal landforms. In the present study,

various periods of IRS series satellite images and ASTER images have been used for de-

tailed mapping of coastal landform. The geology, geomorphology and evolution of the Indian

coast have been contributed in detail by various authors, (Nasir et al., 1992; Johannessen et

al., 1993; Ahmad and Neil 1994; Gangadharabhat, 1995; Tripathy et al., 1996; Loveson and

Rajamanickam, 1998 a; Babu Madhavan, et al., 1999; Chandrasekar, et al., 2000; Thanika-

chalam and Ramachandran, 2002 and Mitra et al., 2002). In addition, Extensive work has

been done on coastal systems using Remote Sensing and GIS (Klemas et al., 1993; Donog-

hue et al., 1994; Fedra 1994; Mumby et al., 1998; Bettinetti et al., 1996; Everitt et al., 1996

and Frithy and Oregan, 1996; Sherin and Edwardson 1996;El Raey et al.,1997;Krishnan et

al.,1997;Williams and Lyon ,1997;Jayappa et al.,2006;Avinash Kumar et al.,2010;Pandiaraj

et al.,2010; Babu Madhavan et al., 1999; Sundar and Shetye, 2005; Sourav Sahai et al., 2005;

Roberto Graciottii,2008;Thanikachalam and Ramachandran, 2003; Hurban et al,2008 and

Sridhar et al., 2010). A considerable amount of work has been done on tectonic setting

control on the beach placer formations Johnson, (1972); Vaidyanadhan (1978); Wagle

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(1982); Rajamanickam et al, (1982). Ahmed (1972) has broadly classified the entire coast of

India into different geomorphologic units. Neo-tectonic and geomorphologic features have

also been studied in Indian coast by using satellite images and geophysical data. Rajamanick-

am (1983) and Wagle and Gujar (1989) have brought out the influence of geomorphologic

and tectonic control in the mineralization of the western shelf of India. Srinivasan and

Srinivasan (1990) have broadly classified the Tamilnadu coast on the basis of structural li-

neaments into eight blocks. Loveson et al., (1996) has classified the entire southern Tamil-

nadu coast on the basis of structural lineaments.

The geomorphology classes were classified and grouped using various sources of data

and image interpretation with proper rectification from the Arc GIS. Afterwards various

tools were applied to demarcate coastal geomorphology and a map is generated using in-

tersect operation of Arc GIS 10 Software. The areal extent of each classes were calculated

and tabulated in Table 4.1.The interpretation of multi-dated IRS series satellite images,

ASTER image, SOI topo sheets, geological maps, hydrographical charts and other existing

reports in the following sections are discussed 1) Geology 2) Coastal structure and tectonic

study and 3) Geomorphology.

4.4 Geology of the study area

4.4.1 General

The basement of the study area consists of Charnockite, Granite Gneiss, Leptinite,

Leptinitic Gneiss, Peninsular Gneiss, Laterite, Warkalli Sandstone, Variegated clay, river

alluvium, etc. Two types of Aeolian deposits in the South Travancore, the red sands forming

the Teris and white sands forming - the coastal dunes. The geological formations represented

in Kanyakumari district are Archaean metamorphic rocks, Warkalli beds considered Tertiary

in age, and two types of blown sands consisting of the red teris (older) and the white coast

dunes. Archaean gneisses are by far the most dominant rocks in the area and form the lofty

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ridges of the Western Ghats, which separate Kanyakumari from Tirunelveli district. In the

low flat area lying between the Western Ghats and the Arabian Sea, the gneisses are very

much reduced by erosion and appear as subdued hills. The terrain comprises largely of Pre-

cambrian crystalline rocks of Charnockites, Khondalites and Migmatitic gneisses. Beach de-

posits are derived from the adjacent hinterlands mainly from Charnockites, Khondalites,

Biotite gneisses. The topography is mild with an elevation not exceeding 60 m at places in

the coastal belt in which crystalline rocks are highly weathered to laterite (GSI, 1999).

The basement rocks are overlain by red soil , lateritic soil, clayed soil, river allu-

vium and coastal alluvium, black, red and red sandy soils of thickness ranging from 1

to 1.5 m in most places. The area is underlain by the peninsular gneissic terrain of India.

Sediments of Miocene were also deposited and identified as the Warkalli sandstones. Al-

so, the sands of recent origin are noticed along the coast. In general, according to the GSI, the

geological formations in the study area comprises of unconsolidated sandy formation of dif-

ferent depositional environment belonging to quaternary age (Fig.4.1). The alluvial deposits

are comprised of interlayer clay, silt, sand, gravel and pebble beds. Borehole lithology de-

picts that the aquifer material comprises of fine to coarse grain sand, sandy clay, clayed

sand and small patches of clay occurring as lenses. The clay that exists as thin lenses or

small patches was mostly deposited in fluvial and shallow marine environments. These for-

mations overlie the Charnockites of Archean age, Charnockites existing below this

formation function as impermeable strata or bed rock (Perumal et al., 2008). Lateral de-

posits or bay deposits of sand, zircon, rutile, ilmenite and garnet minerals are very common

phenomena along the entire coast of Kanyakumari. Near Manavalakurichi, monazite is de-

posited (Chacko, 1966). Bulk of the gneisses in the southern part of Tamil Nadu is made up

of garnet-biotite gneiss and garnetiferous quartzo-feldspathic gneiss representing the migma-

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tised and retrograded equivalents of Charnockite and Khondalite groups (Narayanaswamy

and Purnalakshmi, 1967, Narayanaswamy 1971).

4.4.2 Geological formations:

The present study of geological formation as originated by four groups such as Aeo-

lian, Fluvial, Fluvio-marine and Marine which indicated ages with three divisions of study

areas namely Kanyakumari – Rajakkamangalam, Rajakkamangalam –Colachel and Cola-

chel–Thengapattanam. The detailed geological formations of the study area are as follows:

a) Kanyakumari-Rajakkamangalam division

Predominantly Kanyakumari to Rajakkamangalam area is occupied by Charnockite

group of rocks and alluvium formations. Recent origin of calcareous limestone is noticed

near Kanyakumari. The cape itself consists of low gneiss rocks, backed up by a palm-grown

sand hill, about 30 m high. A pair of very small rocky islands rises out of the sea a few hun-

dred meters east of the Cape. About 6.5 km north-north-east from the Cape, stands the little

stone-built fort of Vattakottai, which is built upon a small patch of calcareous sandstone, full

of marine shells, exposed in the most along the north face of the long curtain wall which

joins Vattakottai fort with the extensive series of fortifications known as “Travancore lines”.

The marine limestone traced for nearly 0.8 km inland in the bottom of the moat. The sand-

stone here contains many well-preserved marine shells, all of living species; but further west,

where the bed is exposed below the Helix bed in the moat; the enclosed shells are all broken

and continued. The surface of sandstone, as seen at the end of the little backwater, is raised

but a very little distance above the sea-level, probably not more than 1.2 to 1.5 m at the out-

side. The rise of the ground along the moat is extremely small and even at the furthest point

from the sea at which the sandstones are exposed the elevation is probably not more than 3

to 3.6 m at most, which would correspond with the top of the sandstones as seen in the little

cliff at Cape Comorin.

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The small Teri immediately behind the Cape Comorin is a very poor specimen of its

kind, and in fact, hardly deserves to rank as one owing to its pale colour and poverty in

iron sand. But it could not classified as a coast dune, as it consists mainly of siliceous sand.

The true dune at the Cape mainly consists of calcareous sand composed of shells, Corallines,

Nullipores etc. At Kovalam, the highly calcareous beach sand which forms many low hil-

locks has been solidified in several places into coarse shell limestone.

The immense wealth of shell fish of all kinds, added to large quantities of Corallines

and Nullipores, incessantly thrown up by the surf, furnishes an abundant supply of

calcareous sand for the formation of this travertine, which forms a bank more than a 1.6 km

long and rising some 20 m or more above the sea at its highest point. Its inland extent cannot

be ascertained, as it is covered by loose sands. It is probably only extends 275 m to 350 m

inland and abuts against a low ridge of gneiss. The grits contain many large clay balls of

blue or mottled colour. A considerable quantity of blown sand fringes the coast from the

Muttom headland Eastward to Cape Comorin, and between Pallam, Keezhamanakudy and

Chottavillai forms some considerable hills. Some years back group of people from Nainapu-

thoor, Veeraregupathynagar etc., lived by collecting shells from the nearshore area of the

region to utilize for various purposes of house white washing.

b) Rajakkamangalam-Colachel division

The charnockite group of rocks is well exposed around Rajakkamangalam, Mut-

tom and Manavalakurichi areas. It consists mainly of Charnockite, Pyroxene granulite and

their associated rock types with Migmatites. Granite gneiss North to North West and South to

South East are established between Rajakkamangalam to Colachel. Colachel area is covered

by the thick lateritic soil dotted with a few rocky outcrops. The Warkalli beds of tertiary

age are exposed as the capping, southwest of Colachel near the coast. It is equivalent of the

Cuddalore sandstone. Tertiary rocks, mainly sandstones and clays occur in a chain of

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plateau–remnants lying parallel to the West coast. Along the West coast of Kanyakumari

District, a sequence of sandstone and clay with thin lignite seams is recorded. These are

correlated to Warkhalli beds of Mio-Pliocene age of South Kerala and are similar to

Cuddalore Formation.

c) Colachel -Thengapattanam

This division has to formed teris overlain all the older formations, mostly the plateau

– remnants. The coastal tract contains limestone and calcareous sandstones which are covered

by sand dunes. Four patches of Teri (loose red sands) are available at Melmidalam, Midalam,

Manavalakurichi and Muttom respectively. The loose red sand is derived from the weathering

of the fixed Teris. The red loam is quite distinct from the local soil, and constitutes a separate

formation, deposited unconformably on the underlying rocks to which it bears no apparent

resemblance. At the Southernmost point of Killiyoor patch, the grits become coarsely

Conglomeratic over a small area. A little to the north of the grits, when resting on the basset

edge of a bed of granular quartz rock, present the characters of a perfect arkose, made up of

the angular gneiss debris. In places this Arkose might be most easily mistaken for a granit-

ic rock. A distinctly conglomeratic character is shown by the grit beds close to Midalam.

This Midalam patch of Warkilli sandstones is on its southern side deeply cut into by a gully

which exposes regular cliffs with from 10 m to 13 m of coarse or conglomeratic mottled grits,

capped by thick red soil. The various rocks occur off the coast opposite Muttam, Colachel,

Simon Colony, Kodimunai, Vaniakudy, Kurumpanai, Midalam and Enayam which are the

culminating points of reefs formed by ridges of gneiss running parallel with the coast.

d) In the hinterland

The hinterland consists of Khondalite suite of Archean age composed of quartzite

of Arenaceous facies, calc- silicates with pockets of crystalline limestone representing

calcareous facies and Quartz Garnet Sillimanite Graphite Schists and Gneisses or argillaceous

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facies. Charnockite intrudes into Khondalites in some places. Muttom and adjacent areas

are characteristised by extensive occurrence of fine sandy loam known as Teris. Their genetic

properties are disputed, though generally an Aeolian origin is ascribed to them. The vegeta-

tion is of semi arid type and the topography is similar to Bad Lands of the United States.

A syenite body, belonging to the group of alkaline rocks of Precambrian Early Paleozoic

Taphrogenic magmatism, is present around Puttetti in the Western part of the

Kanyakumari district area, which is an important geological feature from the viewpoint of

radioactive mineral concentration (Semonov et al., 1997). The heavy minerals are abundant

in the pegmatite veins within Precambrian rocks in the hinterlands as reported through the

geological studies on samples (Mahadevan et al., 1956). To the south of Kottar, the grits are

to be seen in stream beds opening to the Parakay tank, and in a series of deep rain gullies on

the eastern slope of a large red soil plateau to the South West of Parakkai.

4.5 Structure and Tectonic study

Coastal tectonic studies have been conducting and reported from different parts of the

world (Inman and Nordstorm, 1971; Michel and Reading, 1969; Putnam et.al., 1960; Cotton,

1952; Innocenti and Pranzini, 1993). Rajamanickam et al., (1981); Rajamanickam and Love-

son (1990) have studied the implication of tectonism in relation to mineralisation and geo-

morphology along the western shelf of the India. Chandrasekar et al., (1996) has made an

attempt to ascertain the geomorphologic control in the development of heavy mineral placers

along the west coast of Tamil Nadu and Kerala. Loveson et al., (1996) have delineated five

block movements for the southern Tamil Nadu coast. The resultant effects are reflected in the

disposition and complex configuration of the coastline. It is suggested that the Quaternary

movements in coastal areas are mainly of epiorogenic type with vertical uplift and subsidence

throughout the coastline of India. The study of structural and tectonic history indicates

several episodes of deformation, which caused repeated folds, faults, joints and fracture

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systems. The trend of foliation in gneisses is with steep dips on the eastern side. The peculiar

deposition of feldspathic granites over a large portion of this area is suggestive of the

fact that rocks have been sharply folded isoclinically causing repetition of bands. The

trend of folds is aligned in North West– South East direction. Subsequently, this might have

been subjected to cross folding. The straight west coastline without any break is itself

suggestive of faulted one and faulting would have taken place during the Pliocene period.

Peninsular gneisses occupy the largest area in the study places. The general trend of

the strike of the area is NNW to SSE, Garnetiferrous with Sillimanite , Graphite

Gneiss and Garnetibiotite Gneiss are the two major groups identified in this area.

4.6 Kanyakumari Shoreline Alignment

The Kumari shoreline can be perfectly straight only if the land on which water rests is

perfectly smooth and straight. Such a smoothness and straightness can result only where a

submarine floor is recently emerged or where the shoreline is formed by the seaward margin

of offshore bars and spits etc. The latter features themselves occur near recently emergent

shore and shallow shelf. The persistence of this straightness is probably, therefore indicative

of some definite, regular and strong trimming and straightening by marine action. Such an

action might be implicit in longshore drift. This occurrence of straight shoreline against a

crenellated and indented coastal interior is suggestive of the strong role of marine action in

shoreline straightness. The Kumari shore is probably analogous to the sub-mature stage of a

submerge shoreline where there will be an outer and an inner shoreline. Kumari shore can be

regarded as a compound shoreline. The waves generated by the monsoon might have been

responsible for the formation of bars and spits. The shore alignment of an area is of great

economic and human significance. A straight shoreline helps inter visibility both by daylight

or lighthouses located at fairly distant points. It is marked by a highly regular outer shoreline

representing the seaward margin of the offshore bars, where the inner shoreline of the la-

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goon is often highly irregular and rocky and steep having dominantly a submerging aspect.

The shoreline has a dominant emergent aspect viz. a remarkably straight shoreline, domin-

ance of offshore bars largely driven to mainland and a gentle offshore profile. However, be-

hind the straight bars and spits there are numerous water bodies of irregular plan. They

represent drowned mouths of the torrents that descend the Western Ghats. Apart from irre-

gularities of plan, the entire coast is generally deep and rocky, resulting from the subsidence

of a dissected terrain.

4.7 Geomorphology

The coastal geomorphology is right to informative of coastal morphology (appear-

ance), morphometry (dimensions and slope values), morphogenetic (origin/genesis)

and morphochronology (the age) of each form. Representation of these details is an involved

and complicated matter on illustrated and explained. Geomorphic processes are influenced by

tectonics, climate, ecology, and human activity and equally many of these drivers can be

affected by the ongoing evolution of the Earth's surface (Hotten,1856), for example, via

isostasy or orographic precipitation. Various models have been introduced to monitor

changes in coastal landforms using remote sensing; these models are based on pre classifica-

tion techniques or post classification techniques (Green, Kempka, and Lackey, 1994).

The prepared geomorphology map of the study area is depicted in fig. (4.2). The

following pages are given in detail study of coastal geomorphology of Kanyakumari Dis-

trict. Table 4.1 shows areal extent of each coastal geomorphological feature for the present

condition (2012). The coast at Kanyakumari, Agastheeswaram and Kadiapatnam consists of

rocky cliffs. Mangroves (at Manakudi, for example), salt marshes and coconut plantations are

further features in the study area. The coastline between Kanyakumari and Kadiapatnam

consists of sheet rocks. Well developed sand dunes are present along the coastline near

Tamaraikulam and Thengampudur (Chandrasekar et al., 2007). Coastal resources viz., coral

94

reefs, seagrasses, mangroves, and coastal land features viz., sandy beach, mudflats and salt

pan/aquaculture ponds were classified and assessed in the Palk Bay region of the south-east

coast of India using IRS LISS III satellite image (1996, 2000, 2002 and 2004) by Sridhar et

al., (2010). The coastal geomorphological features observed in the study area are Beach,

Sand flat, Sand sheet, Mangroves, Salt marsh, Creeks, Tanks, Swale, River, Shoals, Sand

dune, Beach ridges, Salt pan, Salt affected land with scrub, Dense scrub with vegetation,

cropland, high water line and low water line. The geomorphology map of the four coastal

sectors such as Thengapattanam, Colachel, Rajakkamangalam and Kanyakumari of the study

area is given in fig (4.3) respectively.

4.8 Classification of Landforms

In order to understand the landforms systematically in the context of the origin of

landforms, a genetic classification is generally accepted as most appropriate. Table 4.2

shows the major natural processes, which result in various forms with a few typical exam-

ples at local and regional scale. The coastal lowlands of Kanyakumari with elevation up to 20

m from MSL (except Cuddalore sandstone uplands which rise up to 80 m) exhibit wide rang-

ing features to marine origin. The shore zone part of the area consists of long sandy barrier

beaches and beach ridges interspersed with low beach cliff. As the coast is of open nature,

wave dominated forms are abundant. The geomorphic features of tectonic origin, viz: dis-

sected uplands and pediments; fluvial origin viz. flood plains, palaeo channels, river beds,

sand bars etc. and fluvio-marine and marine origin like deltaic plains, beach ridges and

swales, tidal flats, mangroves, creeks, beaches, etc. were interpreted from the above digitally

enhanced images using tone, texture, association, size, shape and other photo recognition

elements. Such interpreted geomorphic features were digitized and GIS layer was generated.

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Table 4.1 Coastal Geomorphology units for Kanyakumari -Taingapattanam

Coastal stretch (Area in Km2)

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Table 4.2 Classification of various natural processes in the study area

Process Erosional Features Depositional Features

Aeolian Teri sand Sandy plain, Sand dunes

Fluvial Pediment Alluvial plain, Deltaic plain, Delta,

River, Riverine plain, Flood plain

Fluvial- marine Estuary Shoal

Marine

Cliff, Cliff terraces, swale,

Wave cut platforms, Head-

lands and bays, Rocky isl-

ands, Rocky shore

Sandy Beaches, Coastal plain, Beach

ridges, Marshy/swampy, Tidal flats,

Mud flats, Salt flat, lagoon, Spit,

Sand Bars, Cusps, Creek

4.8.1 Aeolian Process

Aeolian landform is a feature of the Earth's surface produced by either the erosive or

constructive action of the wind. The word derives from Aeolus, the Greek god of the winds.

Wind erosion processes consist of abrasion, the scouring of exposed surfaces by the sand-

blasting action of wind-borne material; and deflation, the removal of sand-sized and smaller

particles by the wind. Wind transportation causes attrition of the moving particles, which rub

one another and develop characteristic surface frosting and pitting.

4.8.1.1 Teri sand

Teri dune complex is an undulating terrain having loose heaps of red color sand and

silt dust of Aeolian origin. They represent Pliestocene to Recent age of formation (Loveson,

1993; Loveson et al., 1990). According to Atomic Minerals directorate, a potential heavy

mineral rich zone was identified near Enayam, Kanyakumari district, Tamil Nadu, where

total heavy minerals (THM) associated with teri sands were of the order of 35%. Preliminary

estimation indicated a reserve of 2.2 million tonnes THM with 79% titanium minerals. The

hinderland of Enayam are named as red sand (Chentaraiin vernacular), Theri (Teri name may

97

derived from this name), Keezhkulam, Thope, Thozhicode, Devicode, Alanchi, another

Chentarai near Reetapuram etc. Through some creeks, rare earth minerals reach Thengapatta-

nam, Melmidalam, Midalam and Kurumpanai coasts. A very thin bed of conglomeratic grit

underlies the Teri, or red sand-hill, capping the high ground north of the Muttom headland.

The base of the lower bed is hidden by sands, but from the proximity of the gneiss it cannot

exceed 5 or 6 feet in thickness, while the overlying shell bed measures about the same. It is

overlaid in its turn by a massive bed 6 to10 feet thick locally of a kind of travertine formed of

altered blown sand, composed mainly of fully and fragmented shells.

The same may be said of the Teri resting on the south-eastern extremity of the Cola-

chel sandstone plateau. To the Northwest of Colachel are two much smaller Teris at the dis-

tance of 5 and 7 km respectively. In both of these also the area of the fixed sand far exceeds

that of the loose. Here the fixed part has undergone tremendous erosion and is traversed by

long and deep rain Guillies with vertical sides up to 20 or 25 feet high at Alanchi. Scientific

investigations revealed a rich mineral content that includes Quartz, Monazite, Garnets, Silli-

manites, Ilmenite and Zircon, leading to the establishment of the Indian Rare Earth Complex

at Manavalakurichi. Teri sand populated 6.9 km2 within the study area. Some of the Teri

sand locations are given in plate 4.1.a, b.

4.8.1.2 Sand dune

A dune consisting of loose sand piled or heaped up the wind, commonly found

along the low lying seashore above high tide level, more rarely on the border of large

lake or rivers valley, as well as in various exerts regions and generally wherever

there is abundant dry surface during some part of the year. Many large dune fields are

believed to have originated when sea level was lower and sediment supply was greater (Cart-

er, 1988). The stability of dunes varies greatly, usually depending on vegetation cover. Dunes

in arid climates are often not vegetated and are mobile. However, coastal dunes are normally

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vegetated by plant species adapted to the harsh coastal environment. In many areas, dunes

serve a vital role in protecting inland areas from storm surges, wave attack and Tsunami

(Chandrasekar et al., 2007). Dunes have rich amount of loose sand formed by Aeolian ac-

tivity. The coastal dunes are made of dry sands blown to the backshore area. The coastal

dunes are noticed in Therivilai Kudiyiruppu, near Thengamputhoor, Chettikudiyirupu, Pot-

tayadi near Agasthesswaram, Palloor, Kannakurichi, Ananthanadar kudiyirupu, Sankaran-

kuzhi. A large parabolic dune alongwith dune complex is observed in Chotavilai beach.

Migration of dune is noticed between these regions. The height of the dune rose up to 2 to 4

m near Chotavilai, Pallam and Rajakkamangalam. The sand dune engaged in 0.31 km2 in the

study area. The sand dune situated in Pallam is given in plate 4.2. Natural dunes are stationed

at Chottavilai, Pallam, Manakudy, Keezha Manakudy and Kovalam villages. Nowadays, In-

dian Rare Earth Ltd, Manavalakurichi established artificial dunes at Chinnavilai, Periavilai,

Parapattu and Veetumadai by dumping processed and waste white sand after separating min-

erals.

4.8.1.3 Sandy Plain

Sandy plain presents in Ramanthurai, Enayam Puthenthurai, Kodimunai, Simon

Colony, Colachel, Kotipad, Puthoor, Thalakulam, Pallavilai, Parapattu, Periavilai, Chinnavi-

lai, Ammandivilai, Muttom, Pillaithope, Azhikal, Rajakkamangalam, Manakudy, Kovalam,

Kanyakumari, Achankulam and Panchalingapuram. Natural and artificial structures play a

vital role in the formation of coastal plain in the study area. Natural rocky shore in the Head-

lands at Kurumpanai, Kodimunai, Colachel and Muttom act to drive the longshore drift,

coastal plain settled in the eastern side. Artificial Groins structure placed in Enayam, Kurum-

panai, Vaniakudy, Kodimuani, Simon Colony, Periakad, Kovalam and Kanyakumari regains

coastal plain in the eastern side of structure. The sandy plain of Enayam beach is given in

plate.4.3a.

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Due to accretion of sand at Muttom beach, a long sandy plain situated between

east of Muttom, 4 km long sandy plain in Pillaithope - Azhikal found out. Also sandy plain

regained in the eastern side of Groin structure along the study area as in plate 4.3.b which

can be stationed at Periakad, Enayam, Vaniakudy and Kovalam. The sandy plain filled in

10.32 km2 in the study area.

4.8.2 Fluvial Process

Fluvial is a term used to refer to the processes associated with rivers and streams and

the depositional landforms created by them. Fluvial processes comprise the motion of sedi-

ment and erosion or deposition (geology) on the river bed.

4.8.2.1 Pediment

A pediment is a gently inclined erosional surface carved into bedrock. It develops

when running water erodes most of the mass of the mountain. Pediment is isolated residual

hillocks being remnants of weathering and denudation. This area is mostly barren rocky

and usually smooth and rounded small hills as a result of continuous processes of pedimen-

tation. The altitudinal variations are relatively high for rolling plain and are about 5 -10 m. In

this horizon are exists irregular dissected portions with a number of gully are present. Pe-

diment placed in 0.18 km2 in the study area. Due to undulated surface of the study area, pe-

diment stationed at large area. The pediment at Maruthuvalmalai is shown in plate 4.4. Pe-

diment thickly deposited in Maruthuvamalai, Mukilanvilai and near Madusoodanapuram.

4.6.2.2 River

The major river in the district is Thamiraparani locally known as Kuzhithuraiar.

This river has two major tributaries with the Pechiparai Dam and Perunchani Dam respec-

tively built across them, Kodayar and Paraliyar. There are many tributaries for the Kodayar

River of which Chittar River I and Chittar II, with their dams are the major ones. The origin

of Thamiraparani River is in the Western Ghats and the river confluences with Arabian Sea

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near Thengapattanam, about 56 kms west of Kanyakumari town. Valliar, another small river

and its tributary Thoovalar, originate from the Velimalai Hills, collect the drainage from P.P.

Channel and its branches, ayacuts (irrigated area under a tank) and confluence with the

Arabian Sea in Kadiapattinam. The Pazhayar River, another small river, starts at Shorlacode,

about 18 kilometres North-West of Nagercoil. This is mainly a drainage river, mostly collect-

ing the drainage of Thovalai, Ananthanar and N.P Channels. The Pahrali River also flows

through the district. The river landform settled in 1.33 km2 along the study area. The satellite

image of Thampiraparani is given in plate 4.5. Pazhayar River starts from Mahenrdagiri and

confluences at Manakudy estuary. These all rivers distributaries formed various fluvial and

fluvial-marine land forms and finally designated in the Lakshadweep Sea.

4.8.2.3 Riverine Plain

The riverine plain settled on the banks of rivers. Swamithope and Thamaraikulam

plain is found on the banks of Palayar River. Ammandivilai plain is located on the banks of

Valliyar. Thengapatanam plain is resided on the banks of Thamiraparani. The riverine plain

covers an area of 1.27 km2 in the study area. These riverine plain are generally found along

the river banks. The space image of this landform is well shown in plate 4.6.

4.8.2.4 Flood Plain

Flood plain is the youngest geological unit and including various landforms formed

by fluvial action. This consists of sand, silt and clays and facilities channel bed infiltration. It

is a highly permeable zone helping in partial bank recharge and subsurface flow groundwater

occurs under semi-confined to perched water table conditions with shallow water levels.

Groundwater prospects in flood plains are almost invariably found to be good (Sharma and

Jugran 1992). Flood plain posted in 7.76 km2

in the study area. Whereas the settlements such

as Ramanthurai, Villarivilai, Enayam Thope, Thenguvilai, Elluvilai, Devikode, Alanchi,

Reethapuram, Colachel, Kotilpad, Vettumadai, Kunnankad, Puthukulam,Thalakulam, Putta-

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lam and Kalkerampottal regions. In Puttalam, floodplain regions were converted into Salt

pans as land use of this, which are given in plate 4.7.

4.8.2.5 Alluvial Plain

The Alluvium with intervening crystalline outcrops are noticed as patches in west of

Kanyakumari, Puvankudiyiruppu, Mangavilai, South Surankudi, Thoppur, Vembanoor, Kan-

nakurichi, Attinkarai, Thalakulam, Ottapanavilai, Painkulam etc. The shallow alluvial aqui-

fers along Tamirabarani and Valliyar rivers serve as an important source of domestic wa-

ter, irrigation development for Kanyakumari district. Alluvial plain ascertained as 34.22 km2

in the study area. In these cultivated lands are predominate for crop. The alluvial plain area of

Thalakulam is given in Plate 4.8.

4.8.2.6 Deltaic Plain

The major freshwater wetlands of this district include Parakkai and Pulluvilai region.

Deltaic plain placed in 27.09 km2

along the river beds. This wide area is support to grown

plantation crops and other crop activities. The deltaic plain of Parakkai is given in Plate 4.9.

4.8.2.7 Delta

A delta is a landform that is formed at the mouth or at the source of a river where that

river flows into an ocean, sea, estuary, lake, or reservoir. Deltas are formed from the deposi-

tion of the sediment carried by the river as the flow leaves the mouth of the river. Over long

periods of time, this deposition builds the characteristic geographic pattern of a river delta.

Deltas are typically classified according to the main control on deposition, which is usually a

river, waves, or tides. The study area has posted 0.32 km2 as delta. The delta region placed in

Pottayadi, Nalloor, Parapu vilai and Karkadu. Most of these regions are open land and other

bushes covered. This exposed land of Delta region of Nalloor is given in plate 4.10.

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4.8.3 Fluvio – Marine origin

Fluvio – marine landforms are formed by the joint action and process of a river and

the sea, as in the deposits at the mouths of rivers.

4.8.3.1 Estuary

Dalrymple, Zaitlin, and Boyd (1992) felt that the interaction between river and marine

processes was an attribute essential to all true estuaries. The definition of estuary is as: the

seaward portion of a drowned valley system which receives sediment from both fluvial and

marine sources and which contains facies influenced by tide, wave, and fluvial processes. The

estuary is considered to extend from the landward limit of tidal facies at its head to the

seaward limit of coastal facies at its mouth. There are two important riverine

ecosystems, which confluence with Arabian Sea. They are; Thengapattanam estuary, formed

by the confluence of river Tamirabarani in between Thengapattinam and Eraiummanthurai.

Manakudy estuary formed by the confluence of river Pazhayar in between East and West

Manakudy villages. It covers 0.26 km2 along the study area. The Thengapattanam estuary is

given in plate 4.11.

4.8.3.2 Shoal

A shallow land mass of river valley sandy elevation of the bottom of a body of water,

constituting a hazard to navigation; a sandbank or sandbar. The Pazhayar river line has shoal

fluvial - marine system which is given in plate 4.12. Shoal occupies 0.024 km2 in the study

area.

4.8.4 Marine Origin

The characteristic features and patterns of land in a coastal zone subject to marine

and sub-aerial processes of erosion and deposition. They are subject to processes of erosion

and deposition as produced by winds, waves, tides, and river drained. The interactions of

these processes and the coastal environments produce a wide variety of landforms. It besides

103

raising 50,000 mangrove species to the length of 8 to 10 km in Manakudi estuary, now it

saplings (mangroves) on the banks of Rajakkamangalam estuary to the length of 2 km

and around the ponds within the premises of Manonmaniam Sundaranar University’s Ma-

rine Centre for Biotechnology in Rajakkamangalam area. Sea stacks, sea arches and wave cut

platforms are formed by erosive action at the base of the headlands.

4.8.4.1 Coastal Plain

A coastal plain is an area of flat, low-lying land adjacent to a seacoast and separated

from the interior by other features. Coastal plain - a plain adjacent to a coast dry land,

ground, solid ground, terra firma, earth, land - the solid part of the earth's surface; Coastal

plain settled as the largest geomorphological unit in the study area. It occupies 67.25 km2

along the study area. These coastal plain generally occupies Puthukadai, Killiyoor, Painku-

lam, Keezhkulam, Pallapallam, Alanchi, Reethapuram, Colachel, Mondaikad, kallukootam,

Konankad, Karruparai, Thirunainarkurichi, Vellamadi, Vembanoor, Sadayalputhoor, Allen-

kottai, Ganapathipuram, Melakrishnanputhor, Puthur,Themgamputhoor, Madhusoodanapu-

ram, Therivilaikudiyiruppu, Agasteeswaram, Perumalpuram, Chandayadi etc for varieties of

usages. The satellite image of coastal plain of Thengamputhoor is shown in plate 4.13.

4.8.4.2 Beach ridge

Beach ridges are moderately undulating terrain features of marine depositional type,

formed during Pleistocene to recent age, in the plains of the study area. They are low, essen-

tially continuous beach or beach dune materials (sand, gravel and shingle) heaped up by the

action of wave and currents on the backshore of a beach beyond the present limit of storm

waves or the reach of ordinary tides. Along the central Kerala coast, the coast-parallel beach

ridges are reported to be the product of regressive and transgressive episodes during the Ho-

locene (Mallik and Suchindan, 1984). Beach ridges are also seen in the study area with inter-

vening sandy plains occurring parallel or sub-parallel to the shore formed by periodic wave

104

impounding actions. They are followed in the backshore by sandy plains and are disconti-

nuous in nature. A characteristic feature of this geomorphic unit is the series of beach

ridges and swales which are roughly aligned parallel to the coast. The beach ridges ascer-

tained as 7.21 km2 in the study area. Ridges are presents in Kundal, Panchalingapuram,

Kalkerampottai, Mangavilai, Manikattipottal, Palapallam, Oothukuzhi, Osaravilai, Panavilai

etc. The beach ridge in the study area is given in plate 4.14.

4.8.4.3 Swale

A low tract of land, especially when it is moist or marshy a long, narrow, usually shal-

low trough between ridges on a beach, running parallel to the coastline. A shallow trough

like depression that carries water mainly during rainstorms or snow melts. A Swale is a ditch

on the contour. It does not get direct water, but holds it and allows it to gradually infiltrate

the soil down-slope of it. Soil and water run-off are caught in the swale which becomes a fer-

tile area. Gradual infiltration of water and nutrients and the dead roots of plants growing in

the swale, slowly improve soil structure down-slope. The swale geomorphological system

presents Manakudy, Pallam, Kesavan Puthenthurai, Eathamozhi etc. It occupies an area of

2.15 km2

along the study area. The swale system in the Pallam is given in Plate 4.15.

4.8.4.4 Marshy/ Swampy

Coastal salt marshes are low-lying meadows of herbaceous plants subject to periodic

inundations. During the constructional phase of a coastline, a marsh develops when sediment

deposition exceeds sediment removal by waves. Three critical conditions are required for

marsh formation: abundant sediment supply, low wave energy, and a low surface gradient.

Once sediment accumulation reaches a critical height, the mud flats are colonized by halo-

phytic plants that aid in trapping sediment when flooding occurs and add organic material to

the substrate. Swampy found in Thengapatanam, Colachel and Rajakkamangalam coasts.

105

Swampy nature of coast in Colachel is given in plate 4.16. It populated with 1.1 km2 area

along the study area.

4.8.4.5 Mud flat

Mudflat is a flat area containing a fluid to mixture of finely derived particles of solid

material mainly silt and clay water. They are always associated with silted environments like

lagoons, estuaries and other embankments. Mudflats are formed by the deposition of fine in-

organic material and organic debris in particulate form. Mud flats are wide expense of deposit

of clay, silt, ooze, etc (Davies 1972). Mudflat area is available at Manakudy, Pozhikarai and

Periakad regions. Mudflat in Periakad is given in Plate 4.17. It placed in an area of 0.038

km2.

4.8.4.6 Salt pan

At Kovalam, a salt pan to produce salt near the coast. The salt pan at Kovalam is given in

Plate 4.18. It placed an area 2.7 km2

in the study area. It generally used salt production land

much used.

4.8.4.7 Lagoon

Lagoons are water bodies which are surrounded by sands and gets water supply

through different inlets (creeks) during high tides. The key peculiarity exhibited by

A.V.M. canal, these water bodies is that they exhibit the combination of lagoon and estuary.

Nair and Padmalal (1998) suggested that the uplifting of the coast as a factor responsible for

the creation of lagoon-estuary combination. Valliar River adjoins at Kadiapatanam exhibits

lagoon character for more than 6 months in a year. Minor estuaries Pammpoori Vaikal at

Colachel and Pantri Vaikkal at Rajakkamangalam are two prominent lagoons in the study

area are shown in plate 4.19. Lagoon placed in an area of 0.36 km2 along the study area.

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4.8.4.8 Sand Bar

Thengapatnam estuary 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. It is

formed by the confluence of Thamiraparani River with the Lakshadweep Sea at Thengapatta-

nam. The mean depth, when the bar remains open, is about 1.5 metres. Manakudy estuary

has sand bar on the beach. Sand bar settled in an area of 1.36 km2 in the study area. The sand

bar found in the Thengapatanam estuary is given in plate 4.20. While the tides will generally

affect and changing the pattern of the sand bars.

4.8.4.9 Creek

The important lowland marine landforms are water bodies and wet-lands. Many

creeks flow in the kanyakumari coast from Melmidalam to Kovalam. Among these, Ariyan-

kal mandapam is the prominent creek shown in plate 4.21. Creeks occupies an area of 0.42

km2 in the study area.

4.8.4.10 Rocky shore

A rocky shore is an intertidal area of seacoasts where solid rock predominates. Rocky

shores are biologically rich environments, and make the ideal natural laboratory for studying

intertidal ecology and other biological processes. Because they are so accessible, they have

been studied for a long time and their species are well known (Connell, 1972, Lewis, 1964).

At Colachel, the outlying rocks form a partial breakwater, within which landing is compara-

tively easy. The Class Rocky Shore includes wetland environments characterized by bedrock,

stones, or boulders which singly or in combination have an area cover of 75% or more and

area coverage by vegetation of less than 30%. The rocky shore presence in Kanyakumari,

Kovalam, Muttom, Kadiapatanam, Colachel, Simon Colony, Kodimunai, Vaniakudy,

Kurumpanai and Midalam. The Rocky shore well developed in Kadiapatanam is given in

Plate 4.22. Rocky shore situated in 0.58 km2 in the study area.

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4.8.4.11 Sandy Beach

Beach is defined as a gently sloping accumulation of unconsolidated sediment at the

edge of a sea or other large body of water (including lakes and rivers). The landward limit

may be marked by an abrupt change in slope where the beach meets another geomorphic fea-

ture such as a cliff or dune. Beach is a temporary or short lived deposit on the shore. Sandy

beaches are the product of waves interacting with a sandy beach at the shoreline. Sanguthurai

Beach is about 8 km from Nagercoil is a palm-fringed and sandy beach. It has a huge white

pillar with a tiny black conch built during the Chola period. The Chothavilai beach is one

among the most important beaches in the district of Kanyakumari, Tamilnadu. It’s recognized

as one of the longest beaches of Tamil Nadu; the Chothavilai Beach is situated about 10 ki-

lometers from Kanyakumari close to Sanguthurai beach. The beach has shallow water and

high sand dunes on the background. The studies shows that the presence of sandy beach

along the entire study area. It occupies 2.94 km2. The Chotavilai sandy beach is given in plate

4.23 and it is one of the coastal resorts in the South India.

4.8.4.12 Cliff

Sea cliffs are the most spectacular geomorphic features found along the world’s coas-

tlines. This section concentrates on bedrock cliffs, with bedrock defined as “the solid rock

that underlies gravel, soil, or other superficial material” (Bates and Jackson 1984). Cliffs are

often found along shores where wave erosion rather than deposition is the dominant coastal

process. Exposed bedrock, high relief, steep slopes, and deep water are typical features of

erosional shorelines (de Blij and Muller 1993). Sea cliffs found in Kovalam and Kanyakuma-

ri coasts. Remote sensing study inferred that 0.21 km2 area of cliff settled along the study

area. The sea cliff at Kanyakumari is shown in plate 4.24. This erosional feature shows high

impact of change of coastline of entire coast of Kumari.

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4.8.4.13 Tidal Flat

Tidal flats, also referred to as inter-tidal zones, are the areas located between the high

and low water levels of shorelines. The inter-tidal zone is a shoreline landform that results

from the deposition of suspended sediments by tidal movement (Odum, 1989; Jo and Jo

1999; Kim et al 2003; Won and Kim 2003; Lee and Kim 2004). The morphology, areal

change and waterline of tidal flats of Coromandel coast of Tamil Nadu have been studied by

using satellite images (Sanjeevi, 1996). It is found like shallow, often muddy, part of fore-

shore, which is covered and uncovered by the rise and fall of the tide. The sizeable presence

of tidal flat filled in Midalam, Melmidalam, Helen Nagar and Enayam etc. Tidal flat sited in

Helen Nagar is given in plate 4.25. The Remote Sensing studies revealed that Tidal flat oc-

cupies 0.51 km2. Tidal flat purely affect and change the landforms due the spring and low

tides.

4.8.4.14 Cusps

Rajan et a1, (1992) attributed beach cusps are shoreline formations made up of vari-

ous grades of sediment in an arc pattern. The horns are made up of coarser materials and the

embayment contains all the finer grain sediment. They can be found all over the world and

are most noticeable on shorelines with coarser sediment such as pebble beaches, however

they can occur with sediment of any size. They nearly always occur in a regular pattern

with cusps of equal size and spacing appearing along stretches of the shoreline. The cusp

formation in between Kovalam and Keezha Manakudy shore is given in plate 4.26 and

which inhabitated in 0.025 km2. It is the tip of the coast and nip end of the coast. It mostly

found along the curvatures of coastline. It may be determines the shape of the coastline.

4.8.4.15 Groins

A groin is a rigid hydraulic structure built from an ocean shore (in coastal engineer-

ing) or from a bank that interrupts water flow and limits the movement of sediment. A groin

109

creates and maintains a wide area of beach or sediment on its updrift side, and reduces ero-

sion on the other. It is a physical barrier to stop sediment transport in the direction of long-

shore drift (also called longshore transport). This causes a build-up, which is often accompa-

nied by accelerated erosion of the downdrift beach, which receives little or no sand from

longshore drift . Groins do not add extra material to a beach, but merely retain some of the

existing sediment on the updrift side of the groins. About a mile from the Cape and beyond

the fishing village, a sandy spit ending in a line of locks runs out into the sea, and beyond

this point is an anchorage with sandy bottom to which native crafts run for shelter when the

weather hinders them from rounding the Cape. A sand spit like structure developed at

Kovalam shore and Kodimunai shore due to groin structure. The groin at Perikad is shown

in plate 4.27. The groins occupies in 0.42 km2 along the study area.

4.8.4.16 Rocky Islands

Numbers of rocky islands are present at Enayam, Kurumpanai, Kodimunai and

Colachel. The rocky islands present in Enayam are given in plate 4.28. At Kadiapatnam, the

Crocodile rock is exhibited here. The Crocodile Rock lies South-west at a distance of about

4.5 miles. A part of this appears above water sometimes; but it does not break at all times nor

is it visible at high water when the sea is smooth. The coast from here as far as Cape Comorin

is low and sandy close to the sea, rising in a gentle activity to the base of the mountains si-

tuated a few km inland. Three kilometres from the shore lies a rock called Adumeichan

Parai or Melakkal, 186 m2

in area and rising 2 metres above sea level. The sea is 20 m deep

in this place. Another rock, 2 km east of the above rock, is Kelakkal, about 45 m2 in area.

According to local tradition, the land extended up to these two rocks in ancient times. The

first mentioned rock, Adumeichan Parai, is so named because of the belief that sheep grazed

there earlier. There is an area 0.19 km2 rocky islands settled in the study area. The offshore

110

islands in the Kanyakumari area are probably the remnants of the headlands that were

detached either due to erosion or tectonic activity. All the plates are given in Annexure 1 B.

4.9 Conclusion

The use of Remote Sensed data, allowing a regional synoptic recognition, it provides

a complete geological and geomorphological characterization of regions of interest. They also

provide the details of coastal landforms to map up to microlevel classification of beaches

However, better accuracy in conjunction with relevant ground truth data could obtained. So

far, there is no earlier studies in the region are undertaken using satellite images. The high

resolution satellite images have provided the coastal landforms of Kanyakumari coast in

greater detailed study. The Kanyakumari - Thengapattanam coast under study is a typical

coastal stretch with many unique characteristics. This coast is noted for the occurrence of

unique in many ways. The occurrence of placer deposits along the Kadiapatanam - Midalam

is another feature of this coast. Estuaries, creeks and lagoons occupy most of the coasts of

the study area. Kanyakumari sector is occupied by ponds, salt pans, cliffs, Manakudy Estu-

ary regions and Palayar deltaic region. Mud flats, ridges, Swale systems, cusp and sandy

plain are the significant geomorphological features of Rajakkamangalam region. The Rocky

shore, offshore islands, creeks, alluvial plains and Teri sand are important in Colachel sector.

The Thengapattanam sector engulfed with the sandy plain, Thengapattanam estuary, offshore

islands, Teri sand and tidal flats. This chapter gives a detailed description of the coast which

highly wave dominated, hence the coastal lands are of exposed to frequent erosion and

accretion.