3. Sources for the database on the ocean environs of the area - Index

To know about the ocean environment of Palk Bay, Adam’s Bridge (and Gulf of Mannar) in very definitive terms, we need to have a thorough database on: 1) the coast, 2) sea bed, 3) wave, tide & current dynamics, 4) sedimentation 5) tectonics and 5) meteorology of the area.

Let us index the most important research data so far collected by various researchers first; we shall involve ourselves in an elaborate discussion of these datasets and make our inferences in later chapters.

 

3.1. The Coast:

The geo morphological signatures available in this area that help explain the geological past of the area are:

1) The raised coral reef along Rameshwaram island; the now destroyed but well studied (Stoddart and Pillai,1972) raised coral reef that once existed at Manarkadu point at the east of Pamban pass in the Rameshwaram island, (C.S.G.Pillai, “Scleractinian Fauna” in thr proceedings of the workshop on ‘Biodiversity of Gulf of Mannar”, MSSRF, Feb’1998.) 

2) Existence of Beach Ridges up to 32 km inland from the present day coast (S.M.Ramasamy et al., ‘Rapid land building activity along Vedaranyam coast and its possible implications” Current Science, Vol.75, No.9, 10 November 1998),

3) Beach Ridge patterns between Nagapattinam and Rajamadam, from Rajamadam to Devipattinam, from Devipattinam to Kilakkarai (V.J.Loveson et al., ‘Remote Sensing applications in the study of sea level variation along the Tamilnadu coast, India” in G.Victor Rajamanickam ed., ‘Sea level variation and its impact on coastal environment”, Tamil University, Thanjavur, 1990, p-185-186),

4) Beach Terraces around Pamban island (G.Victor Rajamanickam et al., “Results of Radiocarbon Dating from some beach terraces around Rameshwaram island, Tamil Nadu” in G.Victor Rajamanickam ed., ‘Sea level variation and its impact on coastal environment”, Tamil University, Thanjavur, 1990, p-390-393),

5) Presence of Micro-deltas formed by small rivers (V.J.Loveson et al., “Environmental impact of micro-deltas and swamps along the coast of Palk Bay, Tamil Nadu, India”, in G.Victor Rajamanickam ed., ‘Sea level variation and its impact on coastal environment”, Tamil University, Thanjavur, 1990, p-166), 

Other than these geo-morphological signatures, there are also other evidences that throw light on the environmental history of the coast. They are:

1) Spit formation near Manamelkudi, Vedaranyam, Arimunai and Talaimannar,

2) Marine archeological studies conducted near Thondi, Periyapattinam and Kurusadai Island,

3) Usha Natesan’s study using remote sensing on the changing coastline of the area; Chandramohan et al’s study on the changing beach facies at Puduvalasai.

 

3.2 The Seabed:

Bathymetry data collected over the past century throw light on the changing depth of the sea. They also tell us the dramatic differences in water depths among the Bay of Bengal, Gulf of Mannar, Adam’s Bridge and the Palk Bay.

Soil and subsoil studies conducted so far in this area are very minimal to help understanding the soil structure of the seabed of this area.

3.3. Studies on Waves, Tides and Currents:

Studies on waves, tides and currents are minimal for this area. NEERI has done wave studies while doing the EIA.

3.4. Sedimentation Studies:

Attempts to calculate the total sedimentation load for the Palk Bay have been made by Chandramohan et al; studies on sedimentation dynamics have been attempted by Agarwal, Loveson et al., and Jena (in Gulf of Mannar using bathymetric map of different years);   Studies to determine the pattern of movement of the sediments during various seasons have been made by Chauhan et al., N.Chandrasekaran, Sanil Kumar et al., Usha Natesan etc.; Hydrobiological study by Murthy and Udayavarma is also worth mentioning here. Studies conducted by NEERI for the EIA also includes in it sedimentation studies. We may also include here the radiotracer studies conducted at the Adam’s Bridge area by the Pallavan Transport Consultancy Services in the year 1996.

 

3.5. Tectonics and Volcanism:

Studies on this topic are minimal. Data on the earthquakes over the past century is available. Study on the sea bed morphology of GOM had been initiated by the Indian Ocean Expedition of 1975; Murthy et al. have expanded that study; Cursory data on Tsunami is available.

3.6. Meteorology:

Extensive data is available on this topic from India Meteorological Department (IMD). Many researches and descriptions on the monsoons, inter-monsoonal periods, depressions and cyclones are available.