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Management of Coral Reefs in Gulf of Mannar using Remote Sensing and GIS Techniques – with Reference to Coastal Geomorphology and Land Use


Off shore islands and coral reefs
A chain of 21 low islands has been observed along the offshore region of Gulf of Mannar(Table 3). It extends from south of Rameswaram to Tuticorin. All islands are made up of a calcareous framework of dead reef and sand. They have a low and narrow sandy coast and some of them have rocky coast. Around all offshore islands, well-developed coral reefs have been noticed. Geomorphologically, coral reefs in this area are of fringing type, though some patchy corals are also observed in between Appa Island and Pilliyarmuni Island, and in some areas like Bharathi nagar coast and southeast coast of Kariya Shuli Island.

Wave cut platform

Table 3. Areal Distribution of Offshore Islands and Types of Reefs and their Areal Extent
Sl. No Islands Island Area(km˛) Coral Reef
Reef type Area(km˛)
1 Van Island 0.245 Fringing type 1.090
2 Koswari Island 0.241 Fringing type 1.474
3 Kariya Shuli Island 0.166 Fringing type 0.702
4 Uppu Tanni Island 0.377 Fringing type 0.644
5 Shalli Island 0.126 Fringing type 0.249
6 Nalla Tanni Island 1.248 Fringing type 1.250
7 Anaipar Island 0.229 Fringing type 0.888
8 Palliyarmunai Island 0.134 Fringing type 0.687
9 Appa Island 0.410 Fringing type 3.612
10 Talairi and Valai Island 1.072 Fringing type 9.268
11 Muli Island 0.170 Fringing type 1.208
12 Musal Island 1.836 Fringing type 27.73
13 Manalli Island 0.353 Fringing type
14 Manalli Putti Island 0.037 Fringing type
15 Pumurichan Island 0.187 Fringing type 8.320
16 Kovi Island 0.482 Fringing type
17 Kursadi Island 0.740 Fringing type
18 Shingle Island 0.191 Fringing type 1.023
19 Near Bharathi nagar --- Patchy type 0.131
20 Between Appa Island and Pilliyarmunai Island --- Patchy type 3.981
21 Southeast of Kariya Shali Island --- Patchy type 0.969

Wavecut platforms are common in the coast of Mandapam, Ramaswami Madam, Pudumatam, Valinokkam etc. At Pudumadam coast, hard and tough sandstone platform occupies the intertidal zone. South of Valinokkam coast very extensive wavecut platform has been observed and erosional features are widely seen.

Sea cliff and sea cave
Along the coast of Gulf of Mannar cliffs have been observed in Mandapam, Rameswaram, Pudumatam and Appa Island coastal areas. Generally the sea cliff and caves are made up of calcareous sandstone and located at the high water level. Due to intensive action of waves on cliffs, at some places, sea caves are formed. Such caves have been observed near Mandapam coastal area and Southwestern and Southern coastal areas of Appa Island (Figure 3). At some places, these features have been destroyed due to slumping of upper cliff materials.


Figure 3 Sea caves and cliffs at Appa island coast

Waterlogged land
Water logged land is the area where the water is at or near the surface and has been stagnant for most part of the year. Such lands usually occupy low-lying areas, topographically. In the study area around the northern part of Rameswaram Island some waterlogged lands have been observed. In the areas like Pillaikulam, Surantidal and Mangaud, this type of features has been observed. The total water logged land in the study area has been calculated to be 5.96 km˛.

Strandlines
In the Gulf of Mannar coast from Tiruppullani to Mandapam, eight series of strandlines in curvilinear form have been observed. The general trend of the strandline is in the east to west direction. In the south of Rameswaram area also, curvilinear strandlines have been observed.

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