Environmental Impact Assessment for Proposed
               Sethusamudram Ship Channel Project




                       ...
Environmental Impact Assessment for
             Proposed Sethusamudram Ship Channel Project




                         ...
Contents


      Item                                                               Page
No.

      List of Figures       ...
2.2   Oceanographic Status in Project area along Route Alignment   2.2
Item                                                                      Page
No.

             2.2.1   Waves            ...
3.3.1.4   Manoli and Manoliputti Islands             3.38
                     3.3.1.5   Musal Island                     ...
3.5    Gulf of Mannar                                                    3.72
       3.6    Issues Related to Coral Reefs ...
5.    Socio-economic Environment                                              5.1 - 5.19
       5.1   Socio-economics of t...
7.3    Summary of Environmental Management Plan                            7.6
               7.3.1   Construction Phase  ...
2.14    Components of Currents near Surface off Pamban Pass
                  (Stn. C3) during Southwest Monsoon 2.56
 2.1...
2.33    Components of Currents near Bottom off Rameswaram
         Island South (Stn. C2) (GM) during Fair Weather        ...
3.1   Data Locations                                                     3.92
3.2   Variation in Salinity                 ...
Figure No.              Title                                           Page
No.

 3.8     Location of Corals in the Gulf ...
6.12    Bathymetry along the Proposed Channel                               6.34


Figure No.               Title         ...
List of Tables

Table No.                 Title                                            Page
No.

 1.1        Texture, ...
3.15       List of Zoolplankton at Different Locations                         3.131



Table No.                 Title   ...
Table No.                 Title                                              Page
No.

 3.37       Annual Primary Producti...
6.8        The Quantity of Dredged Material for 14 m Deep 500 Wide Channel 6.66


Table No.                 Title         ...
List of Plates

Plate No.                  Title                                               Page
No.



 4.1        Mer...
List of Drawings

Drawing No.                  Title

   2.1        General Bathymetry in Palk Bay

   2.2        Bathymet...
1. Introduction
1.1      Preamble
         Shipping plays a vital role in the development of the Indian Economy as the
cou...
The creation of a channel called quot;Sethusamudram Ship Channel quot;, now under
consideration of the Ministry of Shippin...
Environmental Impact Assessment studies followed by the Techno-Economic Viability
for the proposed quot;Sethusamudram Ship...
territorial waters of India. The latest study of the project was undertaken by the
Lakshminarayanan Committee constituted ...
- Satellite based differential global system
               - Improvements to Pamban light house

           •   Flotilla
...
three different drafts viz. 30, 31 and 35 feet were worked out alongwith cost estimates
for other components of the projec...
navigational route can be selected based on both environmental and technical
viability. The EIA studies recommended in IEE...
link between invertebrates and vertebrates, viz., hemichordata, cephalochordata and
urochordata have been recorded mostly ...
The coastal segment between Sippikulam and Naripaiyur is open without any
offshore islands or submerged coral banks and is...
between Mandapam tip and Pamban Island is attributed to a sand spit later emerging
as a high water land. The coastline bet...
bordering Gulf of Mannar, but very low and flat along the side bordering Palk Bay.
There is a marked depression in the san...
Palk Bay is very shallow and is largely occupied by sand banks and shoals
(Agrawal, 1988). Abundant growth of corals, oyst...
reveal that the coarse sand in the tidal zones reflect ample sediment supply during the
Northeast monsoons. A number of di...
roadways. The project will help in saving considerable foreign exchange through
reduction in oil import bill, and generate...
measures including impacts due to the disposal of dredged materials,
            consideration of alternatives, etc.

    ...
•   Assessment of impacts on food chain productivity, growth of benthos
           and vegetation, phytoplankton densities...
•    Delineation of hydrodynamic conditions (tide, current, wind and waves)
            including the pattern of movement ...
Collection of baseline data related to socio-economic profile of the study region
with reference to :

         •     Huma...
Environmental Management Plan (EMP) is to be drawn for the pre-
construction, construction and operational phases after id...
1.6.3 Dredging and Disposal Areas
         The disposal areas (within Indian territory) of the dredged materials are to be...
Fig. 1.2 : The Gulf of Mannar and Palk Bay/Palk Strait Area
Fig. 1.3 : The Study Area
Table 1.1

 Texture, Mineralogy and Elemental Composition of Sediments in Palk Strait

Statistical Parameters of Sediments...
2. Proposed Project and
                                              Oceanographic
                                      ...
NEERI has undertaken studies for assessing environmental status of the region and
have engaged services of National Ship D...
2.2.1.1 Wave Measurement
         The observations on wave measurement show that significant wave height
varied from 0.46 ...
m in southwest monsoon and 0.8-2.5 m in northeast monsoon, and around 1-2.2 m in
fair weather period.

         The wave c...
2.2.1.3 Wave Period
         During southwest monsoon, the wave period predominantly persisted 9 –10 s
between Vembar and ...
southwest/northeast monsoons becoming weaker between Dhanushkodi and
Arimunai. This phenomenon of sudden weakening of litt...
Although the longshore current was extremely weak along the sand spit
facing Palk Bay, it tends to be easterly during sout...
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EIA Full report of NEERI on Sethusamudram Channel Project
EIA Full report of NEERI on Sethusamudram Channel Project
EIA Full report of NEERI on Sethusamudram Channel Project
EIA Full report of NEERI on Sethusamudram Channel Project
EIA Full report of NEERI on Sethusamudram Channel Project
EIA Full report of NEERI on Sethusamudram Channel Project
EIA Full report of NEERI on Sethusamudram Channel Project
EIA Full report of NEERI on Sethusamudram Channel Project
EIA Full report of NEERI on Sethusamudram Channel Project
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EIA Full report of NEERI on Sethusamudram Channel Project

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EIA Full report of NEERI on Sethusamudram Channel Project

  1. 1. Environmental Impact Assessment for Proposed Sethusamudram Ship Channel Project Sponsor Tuticorin Port Trust, Tuticorin National Environmental Engineering Research Institute Nehru Marg, Nagpur - 440 020 August 2004
  2. 2. Environmental Impact Assessment for Proposed Sethusamudram Ship Channel Project Sponsor Tuticorin Port Trust, Tuticorin Point Calemer INDIA BAY OF BENGAL Palk Strait INDIA PALK BAY Tamil Nadu Mandapam Rameshwaram Mandapam Keelakkarai LANKA Valinokkam Terkmukkaiyur Vembar Vaipar SRI Tuticorin GULF OF MANNAR National Environmental Engineering Research Institute Nehru Marg, Nagpur - 440 020 August 2004
  3. 3. Contents Item Page No. List of Figures vi List of Tables xi List of Plates xv List of Drawings xvi 1. Introduction 1.1-1. 25 1.1 Preamble 1.1 1.2 Earlier Studies Involving Creation of Canal 1.3 1.3 Project Region 1.7 1.4 Geomorphology of Study Region 1.9 1.5 Environmental Impact Assessment (EIA) 1.14 1.5.1 Objectives of EIA Study 1.15 1.5.2 Scope of the Study 1.15 1.5.3 Plan of Work 1.16 1.5.4 Components included in the Study 1.17 1.5.4.1 Coastal Waster Environment 1.17 1.5.4.2 Marine Environment 1.17 1.5.4.3 Land Environment 1.18 1.5.4.4 Biological Environment 1.18 1.5.4.5 Socio-Economic and Health Environment 1.19 1.5.4.6 Ecological Risks 1.19 1.5.5 Environmental Management Plan 1.20 1.6 Techno-economic Viability 1.20 1.6.1 Traffic Potential 1.20 1.6.2 Alignment of Canal 1.20 1.6.3 Dredging and Disposal Areas 1.21 1.6.4 Cost Estimates and Economic Viability 1.21 1.7 Permits and Approvals 1.21 Figures 1.1-1.3 1.22-1.24 Table 2.1 1.25 2. Proposed Project and Oceanographic Environmental Setting 2.1-2. 104 2.1 Proposed Project 2.1
  4. 4. 2.2 Oceanographic Status in Project area along Route Alignment 2.2
  5. 5. Item Page No. 2.2.1 Waves 2.2 2.2.1.1 Wave Measurement 2.3 2.2.1.2 Wave Refraction 2.4 2.2.1.3 Wave Period 2.5 2.2.2 Tides and Currents 2.5 2.2.2.1 Longshore Currents 2.5 2.2.2.2 Currents Studies 2.7 2.2.3 Sediment Transport 2.12 2.2.3.1 Longshore Sediment Transport 2.13 2.2.3.2 Spit Configuration 2.22 2.2.4 Geological Strata along Navigational Channel in 2.23 Adams Bridge Area 2.2.5 Bathymetry and Shallow Seismic Survey in 2.25 Gulf of Mannar and Palk Bay Area 2.2.5.1 Bathymetry and Shallow Seismic Survey in Area Identified for Channel in Adam's Bridge 2.26 2.2.5.2 Bathymetry Survey of Area of 4 km. X 4 km. 2.36 2.2.5.3 Bathymetry and Seismic Survey along the Channel in Palk Bay Area 2.37 2.2.6 Selection of Route in Adam's Bridge Area 2.38 2.2.7 Navigation Route in Palk Bay and Palk Strait 2.38 2.2.8 Computation of Dredged Material 2.38 2.3 Environmental Setting in Project Area 2.39 Figures 2.1-2.51 2.44-2.98 Tables 2.1 - 2.6 2.99-2.104 3. Marine Environment 3.1-3.167 3.1 Physico-chemical Characteristics 3.1 3.2 Biological Characteristics 3.3 3.3 Biodiversity of Islands in Study Region 3.32 3.3.1 Mandapam Group 3.32 3.3.1.1 Shingle Island 3.35 3.3.1.2 Krusadai Island 3.35 3.3.1.3 Pullivasal and Poomarichan Island 3.36
  6. 6. 3.3.1.4 Manoli and Manoliputti Islands 3.38 3.3.1.5 Musal Island 3.39 Item Page No. 3.3.2 Marine Organisms Observed around the Mandapam Group of Island 3.40 3.3.3 Trend of Fish Catch in Mandapam Region 3.42 3.3.4 Keezhakarai Group 3.42 3.3.4.1 Mulli Island 3.43 3.3.4.2 Valai and Talairi Islands 3.44 3.3.4.3 Appa Island 3.45 3.3.4.4 Anaipar Island 3.46 3.3.5 Marine organisms recorded around Keezhakarai Group Islands 3.47 3.3.6 Vembar Group 3.48 3.3.6.1 Nallathanni Island 3.49 3.3.6.2 Pulivinichalli Island 3.49 3.3.6.3 Upputhanni Island 3.50 3.3.7 Marine Organisms around Vember Group of Islands 3.51 3.3.8 Tuticorin Group 3.52 3.5.8.1 Karaichalli Island 3.53 3.3.8.2 Vilanguchalli Island 3.53 3.5.8.3 Kasuwar Island 3.54 3.3.9 Marine Organisms 3.55 3.4 Palk Bay/Palk Strait 3.56 3.4.1 Marine Water Quality 3.56 3.4.2 Biological Productivity 3.56 3.4.2.1 Primary Productivity 3.57 3.4.2.2 Secondary Productivity 3.59 3.4.2.3 Tertiary Productivity 3.61 3.4.2.4 Benthos 3.61 3.4.3 Sponges and Corals 3.62 3.4.4 Fishing in Palk Bay 3.64 3.4.5 Marine Mammals 3.64 3.4.6 Distribution of Palk Bay Reef 3.65 3.4.7 Review of the Coral Reef Ecosystem of Palk Bay 3.66 3.4.8 Present Status of Palk Bay 3.69 3.4.9 Wildlife Sanctuary Adjoining Palk Strait 3.70
  7. 7. 3.5 Gulf of Mannar 3.72 3.6 Issues Related to Coral Reefs 3.73 3.6.1 Natural Stresses to Coral Reefs 3.74 3.6.2 Impacts of Human Activity on Coral Reefs 3.75 Item Page No. 3.6.2.1 Sedimentation 3.76 3.6.2.2 Runoff/Chemical Pollution/ Water Quality 3.77 3.6.2.3 Sewage 3.78 3.6.2.4 Temperature Stress and Bleaching 3.79 3.6.2.5 Coral diseases 3.80 3.6.2.6 Destructive fishing practices 3.80 3.7 Impacts in Palk Bay and Gulf of Mannar 3.82 3.8 Conservation 3.83 3.9 Future Direction 3.84 3.10 Strategies for Coral Reef Ecosystems in India 3.85 3.10.1 Analyzing the Short Comings in Coral Reef Conservation in India 3.85 3.10.2 Understand the Coral Reef Problems 3.85 3.10.3 Determine the True Economic Value of Coral Reefs in India 3.85 3.10.4 Coral Reef Conservation Education 3.87 3.10.5 Focus Management of Coral Reef around the Stakeholder 3.87 3.10.6 Incorporate More Coral Reefs in Marine Protected Areas 3.87 3.10.7 Control Managing Practices 3.88 3.10.8 Promote Sustainable Uses 3.89 3.10.9 Monitor the Effectiveness of Coral Reef Management in India 3.89 Figures 3.1-3.18 3.92-3.109 Tables 3.1-3.46 3.110-3.167 4. Land Environment 4.1 - 4.15 4.1 Objectives 4.1 4.2 Data Used 4.2 4.3 Hardware and Software Used 4.3 4.4 Selection of Study Sites 4.3 4.5 Methodology 4.4 4.6 Data Interpretation 4.6 4.7 Identification of Dumping Sites for Dredged Materials 4.8 Plates 4.1-4.4 4.10-4.13 Tables 4.1-4.2 4.14-4.15
  8. 8. 5. Socio-economic Environment 5.1 - 5.19 5.1 Socio-economics of the Fishing Community 5.1 5.2 Sample Survey 5.3 5.3 Existing Status 5.6 Tables 5.1 - 5.3 5.13-5.19 Item Page No. 6. Assessment of Environmental Impacts 6.1-6.77 6.1 General 6.1 6.2 Impact Networks 6.1 6.3 Impacts due to Land Based Facilities 6.2 6.4 Impacts due to Dredging 6.3 6.4.1 Dredged Material Disposal 6.7 6.4.1.1 Disposal on Land 6.7 6.4.1.2 Disposal in Sea 6.8 6.5 Impacts due to Road and Rail Traffic 6.12 6.6 Impacts on Productivity and Ecology in GOM/Palk Bay 6.12 6.7 Impacts on Hydrodynamic Conditions 6.15 6.7.1 Tidal Current Distributions – Before and After Dredging 6.16 6.7.2 The Salient Conclusions 6.18 6.7.2.1 Gulf of Mannar 6.18 6.7.2.2 Palk Bay 6.18 6.8 Socio-economic Impact 6.19 6.9 Analysis of Alternatives for Route Alignment 6.19 Figures 6.1-6.30 6.23-6.58 Tables 6.1 - 6.11 6.59-6.76 7. Environmental Management Plan 7.1-7.9 7.1 Construction Phase 7.1 7.1.1 Acquisition of Land for Onshore Facilities 7.1 7.1.2 Dredging Activity 7.1 7.2 Operational Phase 7.3 7.2.1 Route Alignment 7.3 7.2.2 Discharges from Ships 7.3 7.2.3 Maintenance Dredging 7.5
  9. 9. 7.3 Summary of Environmental Management Plan 7.6 7.3.1 Construction Phase 7.6 7.3.2 Operational Phase 7.7 8. Bibliography 8.1-8.7 List of Figures Figure No. Title Page No. 1.1 Shipping Routes in East Coast of India 1.22 1.2 The Gulf of Mannar and Palk Bay/Palk Strait Area 1.23 1.3 The Study Area 1.24 2.1 Measured Significant Wave Height 2.44 2.2 Measured Maximum Wave Height 2.44 2.3 Wave Refraction Between Tuticorin and Arimunai (NE Monsoon) 2.45 2.4 Wave Refraction Between Tuticorin and Arimunai (SW Monsoon) 2.46 2.5 Wave Refraction Between Tuticorin and Arimunai (SW Monsoon) 2.47 2.6 Wave Refraction Between Arimunai and Vedaraniyam 2.48 (NE Monso 2.7 Variation of Currents Off Arimunai in SW Monsoon 2.49 2.8 Components of Currents Near Surface off Arimunai (Stn. C1) during Southwest Monsoon 2.50 2.9 Components of Currents near Bottom Off Arimunai (Stn. C1) during Southwest Monsoon 2.51 2.10 Variation of Currents off Uthalai (GM)in SW Monsoon 2.52 2.11 Components of Currents near Surface off Rameswaram Island South (Stn. C2) (GM) during Southwest Monsoon 2.53 2.12 Components of Currents near Bottom off Rameswaram Island South (Stn. C2) (GM) during Southwest Monsoon 2.54 2.13 Variation of Currents off Pamban Pass in SW Monsoon 2.55
  10. 10. 2.14 Components of Currents near Surface off Pamban Pass (Stn. C3) during Southwest Monsoon 2.56 2.15 Variation of Currents off Tharuvai in SW Monsoon 2.57 2.16 Components of Currents near Bottom off Tharuvai (Stn. C4) during Southwest Monsoon 2.58 2.17 Variation of Currents off Arimunai in NE Monsoon 2.59 2.18 Components of Currents near Surface off Arimunai (Stn. C1) during Northeast Monsoon 2.60 Figure No. Title Page No. 2.19 Components of Currents near Bottom off Arimunai (Stn. C1) during Northeast Monsoon 2.61 2.20 Variation of Currents Uthalai (GM) in NE Monsoon 2.62 2.21 Components of Currents near Surface off Rameswaram Island South (Stn. C2) (GM) during Northeast Monsoon 2.63 2.22 Components of Currents near Bottom off Rameswaram Island South (Stn. C2) (GM) during Northeast Monsoon 2.64 2.23 Variation of Currents off Pamban Pass in NE Monsoon 2.65 2.24 Components of Currents near Surface off Pamban Pass (Stn. C3) during Northeast Monsoon 2.66 2.25 Variation of Currents off Tharuvai in NE Monsoon 2.67 2.26 Components of Currents near Surface off Tharuvai (Stn. C4) during Northeast Monsoon 2.68 2.27 Components of Currents near Bottom off Tharuvai (Stn. C4) during Northeast Monsoon 2.69 2.28 Variation of Currents off Arimunai in FW Period 2.70 2.29 Components of Currents near Surface off Arippumunai (Stn. C1) during Fair Weather 2.71 2.30 Components of Currents near Bottom off Arrippumunai (Stn. C1) during Fair Weather 2.72 2.31 Variation of Currents off Uthalai (GM) in FW Period 2.73 2.32 Components of Currents Near Surface off Rameswaram Island South (Stn. C2) (GM) during Fair Weather 2.74
  11. 11. 2.33 Components of Currents near Bottom off Rameswaram Island South (Stn. C2) (GM) during Fair Weather 2.75 2.34 Variation of Currents off Pamban Pass in FW Period 2.76 2.35 Components of Currents near Surface off Pamban Pass (Stn. C3) during Fair Weather 2.77 2.36 Monthly Sediment Transport Rate 2.78 2.37 Monthly Sediment Transport Rate 2.79 2.38 Monthly Sediment Transport Rate 2.80 2.39 Annual Net Sediment Transport Rate 2.81 Figure No. Title Page No. 2.40 Annual Gross Sediment Transport Rate 2.82 2.41 Location of Boreholes 2.83 2.42a Grain Size Distribution at BH1 at Surface and 2.5 m 2.84 2.42b Grain Size Distribution at BH1 at 5.0 m and 7.5 m 2.85 2.42c Grain Size Distribution at BH1 at 9.0 m and 12 m 2.86 2.43a Grain Size Distribution at BH2 at Surface and 2.5 m 2.87 2.43b Grain Size Distribution at BH2 at 5 m and 6.5 m 2.88 2.43c Grain Size Distribution at BH2 at 11 m 2.89 2.44a Grain Size Distribution at BH3 at Surface and 0.7 m to 8.5 m 2.90 2.44b Grain Size Distribution at BH3 at 8.5 m to 10 m and 10.5 to 12.7 m 2.91 2.45 Bathymetry Map of Gulf of Mannar (1975) 2.92 2.46 Bathymetry map of Tuticorin Coastal Region (1999) 2.93 2.47 Location of Proposed Site 2.94 2.48 Bathymetry Study Over 100 Line km Across the 20 km x 4 km line 2.95 2.49 Area Showing Bathymetry More than 12 m and Hard Strata in Palk Bay Area 2.96 2.50 Area Showing Bathymetry more than 10 m with Hard Strata at about 16 m depth in Palk Bay Area 2.97 2.51 Bathymetry along the Proposed Channel 2.98
  12. 12. 3.1 Data Locations 3.92 3.2 Variation in Salinity 3.93 3.3 Variation in Salinity and Silicate 3.94 3.4 Particle Size Distribution of Sediments (1-10 Sampling Stations) 3.95 3.5 Trophic Relations of Marine in Study Area of Sethu Samudram Ship Canal Project 3.96 3.6 Maximum Diversity Index values of Phytoplankton in 21 Islands of Gulf of Mannar 3.97 3.7 Maximum Diversity Index values of Zooplanktons in 21 Islands of Gulf of Mannar 3.98
  13. 13. Figure No. Title Page No. 3.8 Location of Corals in the Gulf of Mannar and the Palk Bay 3.99 3.9 Coral Reef and Seagrass Areas around the Islands of Gulf of Mannar 3.100 3.10 Maximum Diversity Index values of Corals in 21 Islands of Gulf of Mannar 3.101 3.11 Locations of Pearl Banks in the Gulf of Mannar 3.102 3.12 Chank Habitats in the Gulf of Mannar and the Palk Bay 3.103 3.13 Habitats of Sea Cow (Dugong-dugong) in the Gulf of Mannar and the Palk Bay 3.104 3.14 Habitats of Sea Weed, Sea Grass and Holothuria in the Gulf of Mannar and the Palk Bay 3.105 3.15 Maximum Diversity Index values of Seagrass in 21 Islands of Gulf of Mannar 3.106 3.16 Maximum Diversity Index values of Mangroves in 21 Islands of Gulf of Mannar 3.107 3.17 Locations of Mangroves in Gulf of Mannar and the Palk Bay 3.108 3.18 Maximum Diversity Index values of Corals, Mangroves and Seagrass in 21 islands of Gulf of Mannar 3.109 6 .1 Environmental Impact Network - Construction Phase 6.23 6.2 Environmental Impact Network - Post-Construction/ Operation Phase 6.24 6.3 Study Area for Route Alignment in Adam’s Bridge Area 6.25 6.4 Borehole Data in Adam’s Bridge Area 6.26 6.5 Bathymetry Along Line 1 6.27 6.6 Bathymetry Along Line 2 6.28 6.7 Bathymetry Along Line 3 6.29 6.8 Bathymetry Along Line 4 6.30 6.9 Bathymetry Along Line 5 6.31 6.10 Quantity Dredged Material along Various Tracks in Adam’s Bridge 6.32 6.11 The Alignment of the Proposed Channel 6.33
  14. 14. 6.12 Bathymetry along the Proposed Channel 6.34 Figure No. Title Page No. 6.13 Cross Section of Proposed Channel 6.35 6.14 3D Plume of Disposed Silt 6.36 6.15 Near Field 6.37 6.16 Far Field 6.38 6.17 Central Line Dilution 6.39 6.18 Geographical Domain Considered for Modelling 6.40 6.19 Locations for Current Measurements 6.41 6.20 Tidal Stream Observations 6.42 6.21 Tidal Stream Observation 6.46 6.22 Tidal Observations 6.50 6.23 Proposed Ship Navigation Alignment Considered for Modelling 6.51 6.24 Calibration Tide Heights 6.52 6.25 Calibration Currents 6.53 6.26 Spatial Current Predicted by the Model - Before Dredging 6.54 6.27 Spatial Current Predicted by the Model - After Dredging 6.55 6.28 Locations of Coral Reefs in the Modelling Domain (Adjoining Mandapam and Pambam Islands) 6.56 6.29 Locations of Coral Reefs in the Modelling Domain (Dhanushkodi Portion of Pambam Island) 6.57 6.30 Plan Showing Various Alignments of Sethusamudram Ship Canal Project and the Group of Islands (Marine Parks) in Gulf of Mannar 6.58
  15. 15. List of Tables Table No. Title Page No. 1.1 Texture, Mineralogy and Elemental Composition of Sediments in Palk Strait 1.25 2.1 Monthly Variation of Breaking Wave Height (m) 2.99 2.2 Monthly Variation of Wave Period (s) 2.100 2.3 Predominant Wave Characteristics Buoy Data Off Vembar from Wave Rider 2.101 2.4 Monthly Variation of Longshore Current (m/s) 2.102 2.5 Longshore Sediment Transport Rate 2.103 2.6 List of Islands in the Gulf of Mannar 2.104 3.1 Particulars of Sampling Locations along the Proposed Canal Alignment 3.110 3.2 Physico-chemical Quality of Marine Water 3.111 3.3 Marine Water Quality (Inorganic, Nutrient and Heavy Metals) 3.112 3.4 Sediment Quality 3.113 3.5 Gross Primary Productivity 3.115 3.6 Number of Species Recorded in the Gulf of Mannar Marine Biosphere Reserve during Different Periods 3.116 3.7 Status Report of Biota of Gulf of Mannar 3.117 3.8 Distribution of Phytoplankton in Gulf of Mannar (Number of Species Recorded During October '98, August '99) 3.124 3.9 Maximum Diversity Index Values of Phytoplankton in 21 Islands of Gulf of Mannar 3.125 3.10 Enumeration and Diversity of Phytoplankton 3.126 3.11 List of Phytoplankton Recorded 3.127 3.12 Distribution of Zooplankton in Gulf of Mannar (Number of Species Recorded During October '98, August '99) 3.128 3.13 Shannon Weaver Diversity Indice of Zooplankton Recorded at various Coastal Waters in India 3.129 3.14 Enumeration and Diversity of Zooplankton 3.130
  16. 16. 3.15 List of Zoolplankton at Different Locations 3.131 Table No. Title Page No. 3.16 Maximum diversity index values of Zooplankton in 21 island 3.17 Distribution of Benthic Organisms in Gulf of Mannar 3.133 3.18 Enumeration and Diversity of Macrobenthos 3.134 3.19 List of Macrobenthos Recorded 3.135 3.20 Density and Biomass of Meiofauna in Sediment Samples 3.138 3.21 Distribution Pattern of Corals, Live Corals (Percentage) and Seagrases 3.139 3.22 Maximum diversity index values of Corals in 21 island 3.23 List of Fishlanding Centres within Sethusamudram Ship Canal Zone 3.141 3.24 Shannon Weaver Diversity Index (H' value) for the Ornamental Fishes Recorded Around each Island in the Gulf of Mannar 3.143 3.25 Commercially Important Species Contributing to Fishery in the Gulf of 3.26 Major Fishing Gears used in the Gulf of Mannar and the Palk Bay 3.145 3.27 Marine Fish landings in the Gulf of Mannar during 1992-96 (In Tonnes) 3.146 3.28 Composition of Different Groups in Marine Fish Landings in the Gulf of Mannar (Catch in Tonnes) 3.147 3.29 Composition of Trawl Catches in the Gulf of Mannar 3.149 3.30 Composition of the Trawl Catches at Pamban, Rameswaram and Tuticorin 3.150 3.31 Pearl Oyster Paars in the Gulf of Mannar and the Palk Bay 3.151 3.32 Distribution of Seagrass in the Islands of Gulf of Mannar 3.152 3.33 Maximum diversity index values of Seagrass in 21 island 3.34 Maximum diversity index values of Mangroves in 21 island 3.35 Mangrove Species in Coasts of Palk Bay and Gulf of Mannar 3.155 3.36 Distribution of Mangrove Vegetation in the Islands of Gulf of Mannar 3.156
  17. 17. Table No. Title Page No. 3.37 Annual Primary Productivity (Gross) in Certain Marine Environments as Grams Carbon per square meter Sea Surface 3.157 3.38 Coral Fauna around the Mandapam Group of Islands 3.158 3.39 Summary of Underwater Observations on Shelter and Food of Various Coral Reef Associated Fauna in the Mandapam Group of Islands 3.159 Marine Water Quality in Palk Bay (Latitude 9O44’) 3.40 3.160 3.41 Distribution of Zooplankton in Palk Bay near the Proposed Channel 3.161 3.42 Distribution of Decapods in Palk Bay 3.162 3.43 Distribution of Desmospongiae and Corals in Palk Bay 3.163 3.44 Distribution (kg/hr) of Various Fishery Resources along Palk Bay SE Coast of India during 1985-90 3.165 3.45 Abundance of Demersal Finfish Resources (kg/hr) in SE Coast of India EEZ 3.166 3.46 Perches Abundance in kg along S.E. Coast (Palk Bay) 3.167 4.1 Land use/Land cover Status in Pamban Island, Based on the Satellite data of May, 2002 4.14 4.2 Land use/Land cover Classification System 4.15 5.1 Summary of Coastal Villages/Towns in the Study Area 5.13 5.2 Details of Coastal Towns/Villages in the Study Area (Palk Bay) 5.14 5.3 Details of Coastal Towns Villages in the Study Area 5.18 6.1 Bathymetry along Line: 1 6.59 6.2 Bathymetry along Line: 2 6.60 6.3 Bathymetry along Line: 3 6.61 6.4 Bathymetry along Line: 4 6.62 6.5 Bathymetry along Line: 5 6.63 6.6 Dredging Requirement for 10 m Depth (9.15 m draught) and 300 m Width Channel 6.64 6.7 Dredging Requirement of 12 m Depth (10.7 m draught) and 300 m Width Channel 6.65
  18. 18. 6.8 The Quantity of Dredged Material for 14 m Deep 500 Wide Channel 6.66 Table No. Title Page No. 6.9 Expected Number of Transits through Sethusamudram Channel 6.67 6.10 Inputs to Model for Dredged Material Disposal (12 m deep channel) 6.68 6.11 Maximum and Minimum Tidal Current (Speed) at Locations in Palk Bay and Gulf of Mannar 6.69 6.12 Speed and Direction of Currents for Patch-I - Before Dredging 6.70 6.13 Speed and Direction of Currents for Patch-II - Before Dredging 6.72 6.14 Speed and Direction of Currents for Patch-III - Before Dredging 6.74 6.15 Speed and Direction of Currents for Patch-IV - Before Dredging 6.76
  19. 19. List of Plates Plate No. Title Page No. 4.1 Merged FCC (IRS 1D PAN Sharpened LISS III) depicting Pamban Island 4.10 4.2 Merged Imagery (LISS III + PAN) depicting Western Surrounds of Sethusamudram Ship (Navigational) Canal route in Indian Water 4.11 4.3 Land Use/Land Cover Status in Pamban Island based on IRS 1D 4.12 (LISS III + PAN), May, 2002 4.4 Merged Data (PAN + LISS III) depicting degraded land, selected for dumping dredged material in Pamban Island 4.13
  20. 20. List of Drawings Drawing No. Title 2.1 General Bathymetry in Palk Bay 2.2 Bathymetry and Shallow Seismic Survey - South of Adam’s Bridge Line 1 2.3 Bathymetry and Shallow Seismic Survey - South of Adam’s Bridge Line 2 2.4 Bathymetry and Shallow Seismic Survey - South of Adam’s Bridge Line 3 2.5 Bathymetry and Shallow Seismic Survey - South of Adam’s Bridge Line 4 2.6 Bathymetry and Shallow Seismic Survey - South of Adam’s Bridge Line 5 2.7 Bathymetry and Shallow Seismic Survey - North of Adam’s Bridge Line 1 2.8 Bathymetry and Shallow Seismic Survey - North of Adam’s Bridge Line 2 2.9 Bathymetry and Shallow Seismic Survey - North of Adam’s Bridge Line 3 2.10 Bathymetry and Shallow Seismic Survey - North of Adam’s Bridge Line 4 2.11 Bathymetry and Shallow Seismic Survey - North of Adam’s Bridge Line 5 2.12 Bathymetry Survey in Palk Bay along Proposed Channel Alignment
  21. 21. 1. Introduction 1.1 Preamble Shipping plays a vital role in the development of the Indian Economy as the country has been gifted with a peninsular coastline of about 6,000 km, which is studded with 12 major and over 150 intermediary and minor ports. It also has a strategic location as one of the world's main sea routes and thus has a history of maritime trade with countries across the globe. It is, however, unfortunate that despite having such a coastline India does not have, within her own territorial waters, a continuous navigable sea route around the peninsula from the Gulf of Mannar to Palk Bay and vice-versa due to the presence of shallow (about 3 m) sand-stone reef called 'Adam's Bridge' at Pamban near Rameswaram between the south-eastern coast of India and Talaimann on the western coast of Sri Lanka. Consequently, the entire coastal traffic from the east coast of the country to the west and vice-versa has to go around Sri Lanka entailing an additional distance of more than 254-424 nautical miles and 21-36 hours of sailing time. The shipping routes and savings are shown in Fig. 1.1. The Gulf of Mannar, an inlet to the Indian Ocean between south-eastern India and western Sri Lanka, is bounded on the north-east by the island of Rameswaram, Adam's Bridge and Mannar. The Gulf is about 130-275 km wide and 160 km in length. The Palk Bay on the north of Gulf of Mannar is about 64-137 km wide and 137 km long and includes many islands of Sri Lanka. Furthermore, Adam's Bridge is a chain of shoals, nearly seven in all, located between India and Sri Lanka separating Palk Bay and Gulf of Mannar. It is about 30 km long and the sea across this portion is shallow with a depth of about 3-3.5 m only during high tides. Various committees that have deliberated the subject have observed that a shorter route through the Palk Bay is an important necessity to save time and foreign exchange spent on import of fuel for Indian ships, also the country can stand to gain revenue in foreign currency due to toll collections from International ships.
  22. 22. The creation of a channel called quot;Sethusamudram Ship Channel quot;, now under consideration of the Ministry of Shipping, Government of India, envisages construction of channel in stages and of varying lengths to suit different drafts ranging from 9.15 m to 12.8 m through dredging / excavation across the Adam's Bridge. It is proposed to study different alignments for the proposed channel in the light of representations from the public, the fisherman, the pilgrims and above all its techno-economic viability. The channel will originate from Tuticorin Harbour, extend north-east upto south of Pamban island, cut through Adams Bridge and proceed parallel to medial line of fishing between Sri Lanka and India before joining the Bay of Bengal channel. The width of channel will vary between 200 and 500 m and will require dredging to arrive at desired depth in the Adams Bridge and Palk Bay area. In GOM navigation depths will be used hence no dredging is required. The area engulfing the Adam’s Bridge known as ‘Sethusamudram’ has been derived from the Kings of Jaffna who were called 'Sethukavalar,' meaning protectors of Adam's Bridge and the Southern sea that surrounds the region. The Gulf of Mannar and Palk Bay/Palk Strait separated by Adam's Bridge are shown in Fig. 1.2. The proposed channel on commissioning will bring plenty of prosperity and industrial growth in the Indian hinterland lying along the proposed ship channel and the very presence of the short route would increase the turn-arounds of the coastal and international vessels. There are many other benefits which are difficult to quantify like (a) surge in the development of coastal trade, (b) development of Industries in Ramanathapuram and Tuticorin Districts, (c) amelioration of distress due to droughts visiting annually Ramanathapuram and Tuticorin Districts. • The project will further enable direct movement of Indian naval fleet between the east and west coast of the country instead of going around Sri Lanka. • The project opens up minor ports all along Tamil Nadu coastline upto the major port of Tuticorin and further west upto Colachal. The Tuticorin Port Trust, the nodal agency identified by the Ministry of Shipping for the implementation of the proposal has retained in July 2002 the National Environmental Engineering Research Institute (NEERI), Nagpur to conduct
  23. 23. Environmental Impact Assessment studies followed by the Techno-Economic Viability for the proposed quot;Sethusamudram Ship Channel Projectquot;. 1.2 Earlier Studies Involving Creation of Canal One of the pioneering efforts undertaken to study the construction of the canal was the Commander Taylor's proposal of 1860. Although a series of proposals on the subject were forwarded thereafter during the British regime in the country, due consideration could never be given to the proposal and the Sethusamudram Ship Canal remained a dream for the Indian maritime community. After Independence, the Government of India continued to pursue the idea of constructing the Sethusamudram Ship Canal and among the many committees constituted for studying the feasibility of the project, the 'Ramaswamy Mudaliar Committee' constituted in 1955, was the first. In addition to studying the feasibility of the Sethusamudram Ship Canal project, the committee also studied the increase in potentiality of the port of Tuticorin, if it were to be developed into a deep-sea port alongwith the canal. Although Tuticorin port was in existence for a long time, it did not have berthing facilities for ships and those had to be attended at the anchorage, which was about 5 to 6 miles off the coast. The committee was of the view that the two projects namely the Sethusamudram Ship Canal and Tuticorin Harbour were closely inter-related and should be taken up and executed as part of the same project. After evaluating the costs and benefits, the project was found to be feasible and viable and the committee, therefore, proposed an initial capital outlay of Rs. 998 lakhs for the integrated Sethusamudram-cum-Tuticorin Port Scheme. Thereafter, series of studies were undertaken for the project, and many of those recommended for increase in draught from the original 26 ft. proposed by the Ramaswamy Mudaliar Committee. These studies also led to revision of the Project cost, as also to the expected savings in navigable distance resulting from the canal which ranged from 260 to 425 kilometres. Finally, the Tuticorin Harbour project was sanctioned in 1963 and the Government of India continued to study the various aspects of the Sethusamudram Ship Canal Project. Over a last century, several proposals were formulated by various committees to create a continuous navigable route all around the peninsula within the
  24. 24. territorial waters of India. The latest study of the project was undertaken by the Lakshminarayanan Committee constituted by the Ministry of Shipping and Transport (Port wing) in 1981. The Committee, after a critical review of the earlier proposals, some of which envisaged the canal project by cutting across the main land, investigated another alignment known as the 'K' alignment across the Rameswaram island near Kodandaramasamy temple, and established the technical feasibility and economic viability of the alignment. This alignment was also in keeping with the representations of the public, the fishermen and the pilgrims of Ramanathapuram area who preferred the island being cut east of Rameswaram town. The Committee fixed the alignment across the land and along the northern and southern approaches in the sea, conducted drilling operations in sea and on land, collected tidal, current, wind and other meteorological data, and submitted to the Government of India in 1983 a project feasibility report with an estimated project cost of Rs. 282 crores including foreign exchange component of Rs. 3 crores. As per economic analysis by the Committee, the project would have generated surplus from twentieth year of its operations building up cumulative surplus of Rs. 453 crores at the end of twenty fifth year. However, no follow-up action on this report was initiated due to financial constraints. In its pursuit to make the Sethusamudram Ship Canal project a reality the Government of Tamilnadu in 1996 got, through Pallavan Transport Consultancy Services (PTCS) Limited, the Lakshaminarayanan Committee proposal updated for its economic viability with a view to seeking approval from Government of India for the project. Fresh particulars of cost and traffic were collected and incorporated in the report so as to reflect conditions as of 1996. Apart from the construction of proposed canal, which constituted the major component of project, creation of number of other infrastructural facilities as listed below were envisaged : • Construction of a quot;lockquot; • Construction of rubble mound type breakwaters on either sides of the canal • Navigational aids - Lighted beacons/buoys - Racons
  25. 25. - Satellite based differential global system - Improvements to Pamban light house • Flotilla - Harbour tugs - Pilot, mooring, survey-cum-lighting launches - Despatch vessels • Shore facilities - Two service jetties - Slipways - Buoy yard - Repair workshop • Staff and administration buildings The canal proposed had two legs, one near the Point Calimere called the Bay of Bengal Channel and another across the narrow Danushkody Peninsula near Kodandaramasamy Temple. The Bay of Bengal Channel traverses the Palk Bay wherein the sea-bed is mostly soft to hard clayey-sand in nature and not corals or rock. The channel proposed was 19.3 km away from Point Calimere and Kanakesan Thurai where the coast consists of only clayey-sand. The second leg of the canal 802 m long would have crossed the narrow Danushkody Peninsula through the land portion. The entire coast of Danushkody Peninsula on the North and the South is all sandy. In the North Approach Channel, soft sand-stone was met with below 12 m depth and cutting this sand-stone was not necessary even in the ultimate stage of the canal. The canal would have, however, cut the road connecting Rameswaram and Danushkody. This road is being used by the Rameswaram fisherman to go to Danushkody for daily fishing as there is no habitation at Danushkody. The project envisaged a high-level or a swinging bridge at the crossing point to enable the traffic to go through. Tracer studies conducted at two places along the 'K' alignment established that the pattern of movement of sea-bed silt would almost be in the same direction as that of the proposed canal, and that the chances of siltation would be very minimal. The cost estimates for the proposed canal project were worked out by PTCS Ltd. based on the same quantities of dredging as in the 1983 report but with updated rates for the year 1996. The costs of dredging for various segments of channel for
  26. 26. three different drafts viz. 30, 31 and 35 feet were worked out alongwith cost estimates for other components of the project including those of navigational aids and floating crafts. The construction period for 31 feet draft was estimated as four years with a capital expenditure of Rs. 760 crores. The operation and maintenance cost was estimated by PTCS Ltd. at Rs. 4.52 crores per year. An economic appraisal of the Sethusamudram Ship Canal project, taking into account cost estimates and cost benefits of the proposal, were made by PTCS Ltd. Based on Net Present Value (NPV) method of appraisal, an Internal Rate of Return (IRR) of 10 to 17% on the project investment was arrived at. Considering the then interest rate of 9% per annum of government lending to ports on the capital employed the project would have generated surplus from the 16 or 17th year of its operation, and thereafter the benefits to the canal company would have been 47 crores in the first year, and this would have increased to 100-120 crores every year. The traffic potential through the canal at various draughts projected by both the studies for 2000 AD were as follows : Upto 30' draught 31~32' draught Above 32' draught 1983 Committee 2,100 2,200 2,300 1996 Report 3,791 3,875 4,211 Later a report was prepared by NEERI in 1998 comprising the examination of environmental status of the project region based on information available on hydrography, marine water quality and ecological resources etc. An environmental impact study was recommended by NEERI as essential for fuller description and appreciation of the natural processes occurring in the region to delineate the environmental consequences including the ecological risks associated due to the ship canal and suggest measures for minimisation and mitigation of potential adverse impacts. The study for initial environmental examination of proposed canal also recommended that the canal route should pass through Adams Bridge area circumventing the Pamban Island instead of cutting through it. A detour was suggested from earlier alignment. Keeping in view the location biosphere reserves, it was suggested that an environmental viable alignment of route be selected in GOM so that proper distance from Biosphere reserves can be maintained and the available
  27. 27. navigational route can be selected based on both environmental and technical viability. The EIA studies recommended in IEE report of NEERI was therefore subjected to proper scoping so that all the environmental concerns due to this project can be addressed and resolved through this report. The technical viability would depend on quantity of dredging required in the vicinity of Adams Bridge area keeping in view the draft required to operate the channel. This study report addresses environmental, technical and commercial viability of the proposed ship canal project. 1.3 Project Region The Palk Bay and the Gulf of Mannar together sprawling over an area of 10,500 sq.km (8O35’N to 9O25’N latitude and 78O8’E to 79O30’E longitude) in which the ship channel is proposed to be constructed are biologically rich and rated as the highly productive seas of the world and their biodiversity is considered globally significant. In the Gulf of Mannar, there are 21 islands covering an area of 623 ha which have been declared as National Marine Parks by the Tamilnadu Forest Department and the MoEF, Government of India. The islands are distributed in 4 groups namely Mandapam, Keezhakarai, Vembar and Tuticorin group. The islands have luxurient growth of mangroves in their shores and swampy regions. The coral reef of fringing and patch type are present around the 21 islands from Rameshwaram to Tuticorin covering a distance of 140 km. However, a major part of the reef is fringing type arising from shallow sea floor of not more than 5 m in depth. About 3600 species of flora and fauna have been recorded in this area. Fringing type of reef is present in Palk Bay. The hydrography data shows that there are two circulations of water masses in the region, the clockwise circulation of south-west monsoon and the counter clockwise circulation of north-east monsoon. The reported current velocities in the Palk Bay and the Gulf of Mannar are as mild as 0.2 - 0.4 m/sec except on few days during south-west monsoon when it rises upto 0.7 m/sec. The directions of currents follow the directions of predominant winds. The presence of corals along the proposed ship channel alignment is negligible however occurrence of major groups of biological resources like sea fan, sponges, pearl oysters, chanks and holothuroids at various locations have been reported. All the three groups of prochordata organisms, considered as the connecting
  28. 28. link between invertebrates and vertebrates, viz., hemichordata, cephalochordata and urochordata have been recorded mostly around the islands of the Gulf of Mannar. There are 87 fish landing stations between the south of Point Calimere and Pamban in the Palk Bay, and 40 stations in the Gulf of Mannar between Pamban and Tuticorin. Out of over 600 varieties of fishes recorded in this area, 72 are commercially important. During 1992-2001, the fish production has increased gradually from 55,300 tonnes in 1992 to 2,05,700 tonnes in 2001. Non-conventional fishing in the region is represented by pearl, chank, sea weeds, ornamental shells and holothurians. Rare and endangered species of sea turtle, dolphin, sea cow and whale are recorded in the Gulf of Mannar and the Palk Bay. The sea cow inhabitates the shallow shore regions where grasses occur, while other endangered animals mostly prefer deep sea. Several species of green algae, brown algae, red algae, blue-green algae and sea grasses are recorded in the Gulf of Mannar and the Palk Bay. A few of the islands are reported to possess patches of mangroves predominated by Avicennia sp. and Rhizophora sp. Most of the habitats of the sensitive biota, viz., corals, pearl oysters, chanks, dugong, holothuroids and marine algae are along the coast and around the islands. Along the coast in the Gulf of Mannar and the Palk Bay there are 138 villages and towns spread over 5 districts. 1.4 Geomorphology of Study Region The study region stretches between Tuticorin and Dhanushkoti including its coastal and offshore water in Gulf of Mannar and Palk Bay area between Pumban and Point Calimere. The coastline near Tuticorin is extensively used due to the presence of major port. Beach is very flat and narrow between Tuticorin and Sippikulam. Offshore islands viz; Pandyan Tivu, Van Tivu, kasuvari Tivu, Vilangu Shuli Tivu and Kariya Shuli tivu are present within 5 km distance from the coast line along this segment and offer protection from wave action. The backshore of this costal segment largely consists of salt pans. The Viappar river joins Gulf of Mannar near Sippikulam. An extensive coastal low land is seen between Sippikulam and Vembar (Loveson, 1994).
  29. 29. The coastal segment between Sippikulam and Naripaiyur is open without any offshore islands or submerged coral banks and is exposed to direct action of waves both during southwest monsoon and northeast monsoon. The coastline near Kannirajapuram is found with large extent of beach rocks with pear luster (Loveson, 1994). Wide and flat sandy beach with numerous small dunes are seen between Naripaiyur and Mukkaiyur . The formation of sand island off Tuticorin indicates this region as sediment sinks with progressive accumulation of sand. The large beach storage of sand between Manppad and Tiruchendur, Vembar and Valinokkam and Rameswaram Island is an indication of depositional features of littoral sediments. Gundar river joins the sea near Mukkaiyur. The presence of offshore islands are once again noticed from Mukkaiyur till Mandapam. There are 16 islands noticed along this coastal segment viz., Uppu Tivu, Shalli Tivu, Nalla Tanni Tivu, Anaipar Tivu, Palliyarmunai Tivu, Puvarasanpatti Tivu, Appa Tivu, Talairi Tivu, Valai Tivu, Muli Tivu, Musal Tivu, Manali Tivu, Pumorichan Tivu, Kursadi Tivu, Kovi Tivu, and Shingle Tivu. The beaches between Mukkaiyur and Valinokkam are very wide with elevated dunes. Extensively developed beach is seen at Kilamundal. Flat rocky shorelines are noticed near Valinokkam (Loveson, 1994). Extensive spread of rocky shore with hard sand stone platform is seen off Valinokkam. There is a Bay formation immediately on the northern side of Valinokkam. No beach is present especially during high tide Kilakarai. A narrow and flat beach is noticed near Sethukarai with the abundance of algae along the coastline. Loveson and Rajamanickam (1987, 1989) have identified a spit growth near Pariyapattinam. They described well-developed hooked nature spit extending southeast and connecting the main land in southwest direction. This formation of spit extending southeast and connecting the main land in southwest direction indicated seaward progradation of the coast between Tuticorin and Mandapam. Wave cut cliff is seen at places like Valinokkam, Sethukarai and Mandapam. Very low and narrow sandy beach is noticed between Kalimangundu and Vedalai (loveson, 1994). Sea is found to be very calm in this region. Wave cut platform is once again noticed along the coast of Vedalai. A patch of rocks is observed along the coast between Mandapam camp and Mandapam tip. Agrawal (1988) observed that the area
  30. 30. between Mandapam tip and Pamban Island is attributed to a sand spit later emerging as a high water land. The coastline between Mukkaiyur and Mandapam is totally protected from northeast monsoon waves. Chandrasekar et al. (1993) indicated reversal trend in the direction of sediment transport between Mandapam and Cape Comorin due to change in the coastal configuration, deposition as the formation of numerous spits along this coast that too, in a region where fluvial activities are negligible. The presence of three offshore islands viz., Pumorichan Tivu, Kursadi Tivu, Shingle Tivu are noticed off Rameswaram Island in Gulf of Mannar. The stretch of shoreline around Rameswaram Island exhibits distinct variation (Loveson, 1994). The central zone of the northern part of Rameswaram is made up of undulatory sandy bodies with a relief upto 21 m above Mean Sea Level (MSL). This area is partially covered with huge dunes. Northern part of Rameswaram Island is occupied by raised coral plain. Characteristically, this zone is flat with dead corals and numerous minor circular depressions. These depressions are liable to get filled with water during rainy season and is entirely devoid of vegetation. Huge sand dues of medium grain and white sands are found in the central part of the island. Dune patterns are well developed by the active Aeolian processes, resulting in the migration of dunes with frequent changes in their shapes and patterns from time to time but generally trends due east to west. The sand sheet covers the southwestern zone of the island. Within this unit, on the western part, localized sand mound of about 19 m height is noted (Loveson, 1994). The beach zones in this area are broader with wide inter tidal zones. The tail portion of Rameswaram occupying the southeastern part of the island has coral swampy plain, which is considered to be of recent in age. This vast flat and low-lying plain, which is considered to be of recent in age. This vast flat and low lying plain is essentially composed of thin sheet of silt and clay materials in which coral fragments are impregnated. Invariably, this zone is often inundated by seawater during high tides, monsoons and storm seasons. At east, a long sand spit of about 20 km length is formed up to Arimunai and it tends to grow longer and wider. The width of this sand spit which is about 2 km near Uthalai, reduced to Arimunai and it tends to grow longer and wider. The width of this sand spit which is about 2 km near Uthalai, reduced to 1250 m at Mukkuperiyar, 750 at Dhanushkodi and 150 m at just east of Arimunai and coverages on tip at Arimunai. The beach berm is found to be highly elevated along the sand spit
  31. 31. bordering Gulf of Mannar, but very low and flat along the side bordering Palk Bay. There is a marked depression in the sand spit level between Palk Bay and Gulf of Mannar between Dhanushkodi and Arimunai. Due to such level difference, the water overflows during spring tide particularly from Bay carrying the fine sediment to the backshore regions. Most of the time, the water is stagnant and remains along the trough of the spit. This low lying region is fully occupied by water column during the monsoon season. The coastal process between Arimunai (India) and Talaimannar (Sri Lanka), i.e. along Adman’s Bridge is quite complex which predominantly control the exchange of sediment between Gulf of Mannar and Palk Bay. Adam’s Bridge is formation of submerged sand shoals and there are around 17 islands present with bushes and plants. The average length of these islands vary between 0.8 km to 3 km. This is exposed to complex current pattern with the presence of quicksand. The currents near Adam’s Bridge and Pamban Pass are found to be more seasonal. Submerged sand shoals are seen shifting south of Arimunai and remain quasi-steady. The nearshore on the northern side of the Rameswaram Island is found to be very shallow causing the northeast monsoon waves to break far offshore. The coastal stretch between Mandapam and Ariyaman in Palk Bay shows the presence of wide beach with elevated dunes. Loveson et.al. (1990) classified the coastal zone of Palk Bay into 3 groups; (i) uplands/highlands with scantly vegetation, comprised of Cuddalore sandstone formations, (ii) along the lower elevations sedimented Cuddalore sand stones, and (iii) coastal lands mainly of microdeltas, swamps, and beach ridges based on the geomorphological features. A large amount of sediments from those pediments are removed constantly by rainfall and minor rivers. Because the pediments are placed over the substratum which is appreciably sloping towards the sea, the erosion is found to be intensive along the coastal islands. The eroded sediments brought to the littoral zone are dumped in Palk Bay. As Palk Bay is shallow and protected from the high waves and currents, the materials brought by these minor rivers is deposited in the mouth of each river/stream, leading to the formation of micro-deltas in due course, encouraging the formation of new shorelines.
  32. 32. Palk Bay is very shallow and is largely occupied by sand banks and shoals (Agrawal, 1988). Abundant growth of corals, oysters, sponges, and other sea bottom communities flourish in the relatively calm waters of Gulf of Mannar. Sea level variations along the Tamilnadu coast were studied by Loveson et.al., (1990) using satellite imageries and photographs. About 300 sediment samples were collected along the central Tamilnadu coast by Chandrasekhar and Rajaminckham (1993) and suggested to possibility of the supply from ultrabasic, pegmatitic and granitic source of material to the depositional basic. River Influx and Sedimentation in Palk Bay/Palk Strait Vaigai River basin is located between latitude 9O15’ and 10O25’N and longitude 77O15’ to 79O covering an aerial extent of 8600 sq. km. in the Madurai and Ramanathapuram districts of Tamil Nadu, India. The river Uaigai, originates at an altitude of 2200 m above mean sea level in the western ghats, drains through the plains and confluences with the Bay of Bengal near Attangarai of Ramanathapuram district. The basin is bounded by western ghats, in the west, Palni hills in the north, a stretch of mountain ranges comprising Varushanad and Andipatti hills in the south and the Bay of Bengal in the east. Vellar estuary also comes under Palk Bay (lat. 11029'N ; long. 79046'E). Sediment in estuarine region are rich in organic carbon, phosphorus and nitrogen and finally finds its way into Palk Bay. The nutrient rich water (due to settling of unified feed particle) discharges periodically from the shrimp farms however did not show influence on nutrients content of sediment in estuary. Sea Bed Characteristics Geomorphology of the area exhibits tidal flats, estuaries and marsh zones as well as linear stabilized older younger sand dunes. Beach dunes run parallel to the sea. Geologically, thick section of Quaternary alluvium overlies the Archean charnockite rocks and these are in turn overlain by the Holocene tidal flat deposits. The detailed lithological observation of cores reveals that the sediments have been depositing in phases and that there has been pulsating supply of fine sediments onto the tidal flats and estuaries. Sediment in the cores show very heterogeneous mixture of quartz sand, biogenic carbonate and clay. Geomorphologic observations
  33. 33. reveal that the coarse sand in the tidal zones reflect ample sediment supply during the Northeast monsoons. A number of different types of topographical features are found in the study area, such as continental shelves, deep sea basins, troughs, trenches and continental slopes. Sediments are moderately well stored and slightly well skewed. Kurtosis value of 0.3 shows less sorting in grain size distribution. Clay is absent and sediments are made of detritus. Different grain size sediment show variable levels of heavy metal (Fe, Mn, Cr, Cu, Pb, Zn, Cd & Hg) concentration (Table 1.1). 1.5 Environmental Impact Assessment (EIA) The pre-construction phase would involve land acquisition, resettlement and rehabilitation of affected population as also compensation hence impacts due to such activities are required to be assessed. During the construction phase there will be considerable increase in rail and road traffic to and from the island for transportation of men, material, machinery and equipment. Also, the land access, now available to the local fisher folks, to Dhanushkody area for traditional fishing may be hindered unless alternative arrangements are made. The potential sites for dredging and disposal of dredged material are to be decided as also shipping operations will have to be regulated so as to cause minimum disturbance to the normal fishing activities. During the operation phase of the channel, the potential sources of marine pollution are spillage of oil and grease, marine litter, jetsam and floatsam including plastic bags, discarded articles of human use from the sea-borne vessels hence impacts due to such wastes are to be assessed. The channel may facilitate the movement of fishes and other biota from the Bay of Bengal to the Indian Ocean and vice versa. By this way, the entry of oceanic and alien species into the Palk Bay and the Gulf of Mannar, as also the disposal of endemic species outside the Palk Bay and the Gulf of Mannar may occur. The project is expected to provide employment opportunities and avenues of additional income through establishment of small ancillary industries. The project will also trigger development of coastal trade between the ports south and north of Rameswaram, consequently reducing the load and congestion on railways and
  34. 34. roadways. The project will help in saving considerable foreign exchange through reduction in oil import bill, and generate revenue income from dues levied on ships transiting the canal which will add to the national economy. 1.5.1 Objectives of EIA Study The objectives of the study is to carry out assessment of environmental impacts, its quantification and for delineating environmental management plan for Sethusamudram Ship Channel project to enable the Ministry of Shipping to obtain environmental clearances from concerned local, state and central Government authorities. The environmental assessments are to be carried out in keeping with the applicable guidelines and notifications of the regulatory agencies as also the International transboundary concerns. The rapid environmental impact assessment study report was prepared incorporating primary data collected for the region and also available secondary data, environmental impact statement based on identification, prediction and evaluation of impacts, ranking of environmentally viable alternatives and environmental management plan for the acceptable route. The comprehensive EIA report was prepared later based on the primary data collection for region.The area for Environmental Impact Assessment Study is shown in Fig. 1.3. 1.5.2 Scope of the Study The scope of the comprehensive EIA study is summarised as follows : i. Assessment of the present status of coastal water, marine, land, biological and socio-economic components of environment including parameters of human interest along the proposed ship canal route ii. Identification of potential impacts on various environmental components due to activities envisaged during pre-construction, construction and post- construction/ operational phases of the proposal iii. Prediction of impacts on the various environmental components using appropriate mathematical/simulation models iv. Preparation of environmental impact statement based on the identification, prediction and evaluation of impacts v. Preparation of detailed Environmental Impact Statement (EIS) duly bringing out the likely impacts of the project, mitigation, protection and enhancement
  35. 35. measures including impacts due to the disposal of dredged materials, consideration of alternatives, etc. vi. Short-listing of viable routes for the proposed shipping canal based on technical requirements, and delineation of acceptable canal route for shipping based on environmental considerations vii. Delineation of Environmental Management Plan (EMP) outlining preventive and control strategies for minimising adverse impacts for various stages of the proposed project including the costs and time schedules for its implementation viii. Formulation of environmental quality monitoring programme for various phases of the project to be pursued as per the requirements of statutory authorities 1.5.3 Plan of Work • Collation/ collection of primary and secondary data on benthic flora/ fauna, meiobenthos, bacrobenthos • Collation/collection of primary and secondary data on phytoplankton, zooplankton in water column • Assessment of general physico-chemical quality of water • Assessment of sediment quality and its texture • Fishery potential of the region • Collation of secondary data on bathymetry, sediment transport, water current and directions, wave height, tidal variation, dispersion coefficients and other hydrographic parameters • Collection of information about marine parks and ecologically sensitive species • Qualitative and quantitative assessment of waste loads likely to accrue from proposed activities in the hinterland all along the canal • Assessment of change in hydrographic pattern in the region during and after implementation of dredging activities vis-à-vis impact on coastal ecosystems
  36. 36. • Assessment of impacts on food chain productivity, growth of benthos and vegetation, phytoplankton densities predatory fish and birds in the coastal waters • Assessment of impacts on ecological health due to hydrodynamic and water quality changes 1.5.4 Components included in the Study 1.5.4.1 Coastal Water Environment • Study of coastal water environment with respect to its physico-chemical and biological characteristics • Assessment of mangrove forests/vegetation in the coastal and inter- tidal zones • Determination of primary and secondary productivity in the coastal region • Prediction of impacts of discharges during dredging on marine water quality • Evaluation of impacts due to shipping activities in keeping with the CRZ regulations 1.5.4.2 Marine Environment • Establishing abiotic and biotic characteristics of water and sediment component of marine environment
  37. 37. • Delineation of hydrodynamic conditions (tide, current, wind and waves) including the pattern of movement of sea-bed material in the project region • Assessment of impacts of dredging, transportation and disposal of dredged materials like interference with fishing, increased turbidity and disturbance to the flora and fauna • Identification of likely impacts on the islands/region along the shipping canal • Prediction of impacts of the project on other natural marine processes 1.5.4.3 Land Environment • Study of existing landuse pattern, vegetation and forestry along the coastline of the region • Assessment of impacts on landuse pattern of main land and islands with respect to agriculture and forestry due to proposed project 1.5.4.4 Biological Environment • Identify the sensitive receptors and ecological systems within the study region • Collection of information about flora and fauna and determination of species diversity, density, abundance etc. • Collection of available information on both terrestrial and aquatic flora and fauna, including rare and endangered species in the study region • Assessment of potential impacts on aquatic flora and fauna due to effluent discharges • Prediction of stress on biological environment in the study region • Estimation of anticipated impacts on fisheries and other useful aquatic flora and fauna • Delineation of measures for abatement/reduction of biological stress 1.5.4.5 Socio-economic and Health Environment
  38. 38. Collection of baseline data related to socio-economic profile of the study region with reference to : • Human settlements, occupational pattern, employment and income in the region • Infrastructure resource base, viz. Medical, education, water resources, power supply • Economic resource base, viz. Agriculture, industries, forest, trade and commerce • Health status, viz. morbidity pattern with reference to prominent and endemic diseases • Cultural and aesthetic attributes in the study region including places of historical/ archeological, religious, recreational importance - Estimation of disruption in social life due to relocation of human settlements and assessment of rehabilitation requirement - Assessment of impacts on places of historical/ archeological importance and aesthetic impairment - Assessment of economic benefits to community and environment due to the proposed activities 1.5.4.6 Ecological Risks • Quantification of ecological risks and delineation of ecological risk mitigation measures • Study and survey of environmentally sensitive sites viz. spawning and breeding grounds and coral reefs • Analysis of information with regard to environmental impact (direct, synergistic and cumulative) and associated nagivational and landward activities in and around the project region • Quantification of ecological risks with recourse to appropriate ecosystem models 1.5.5 Environmental Management Plan
  39. 39. Environmental Management Plan (EMP) is to be drawn for the pre- construction, construction and operational phases after identifying, predicting and evaluating the impacts on each component of the environment with a view to maximising the benefits from the proposed project. The EMP to be prepared would mainly cover mitigation measures at dredging sites, transportation route (of dredged spoil), and dumping site. EMP would essentially consist of details of work proposed under mitigation measures, implementation schedule of such measures, fund and manpower requirements. 1.6 Techno-economic Viability 1.6.1 Traffic Potential The future traffic potential is to be studied over short, medium and long term time horizons in terms of volumes of cargoes in tonnage like container, dry, liquid, bulk, also number, size and category of ships and other types of vessels taking into due consideration the future economic growth. 1.6.2 Alignment of Channel Alignment of the channel is to identified with reference to environmental factors, navigational aspects, morphological aspects, seabed movements/ sedimentation likely to be induced by the cross currents in the canal after its creation and during operation.
  40. 40. 1.6.3 Dredging and Disposal Areas The disposal areas (within Indian territory) of the dredged materials are to be spelt out to satisfy the statutory requirements of State/ Central Govt. Deptts./Ministry of Environment & Forests and other concerned Archeological Deptt., Tamilnadu Pollution Control Board, Tamilnadu Maritime Board etc. so as to ensure that the dumping of dredged materials will not adversely affect the environment. Study the transboundary effects such as flooding and effects of fishery potential etc. on the Sri Lankan side due to the disposal of dredged materials. Also, the quantum of maintenance dredging per annum, its periodicity, disposal areas etc. are to be assessed. 1.6.4 Cost Estimates and Economic Viability This would include the project cost estimates towards preliminary surveys and site investigations; dredging costs, transportation and dumping of dredged material at the chosen sea/land locations. The economic analysis for a selected route will also be carried out. 1.7 Permits and Approvals Permits and approvals from the following mentioned agencies / organisations are envisaged : • Tamilnadu State Pollution Control Board • Tamilnadu State Forest & Environment Department • Tamilnadu Maritime Board • State Wildlife Warden • Chief Conservator of Forests • Ministry of Environment & Forests • Ministry of Defence / Indian Navy • Archeological Department • Ministry of External Affairs • Sri Lankan Government
  41. 41. Fig. 1.2 : The Gulf of Mannar and Palk Bay/Palk Strait Area
  42. 42. Fig. 1.3 : The Study Area
  43. 43. Table 1.1 Texture, Mineralogy and Elemental Composition of Sediments in Palk Strait Statistical Parameters of Sediments (units in φ) Area Mean Dispersion Skewness Kurtosis Median Palk strait 2.4 0.4 -0.07 0.3 2.3 Percentage of Various Minerals in Sediments Area Quartz Feldspar Carbonates Clays Palk strait 64 4 32 -- Chemical Composition of Bed Sediments Fe Mn Cu Pb Zn Cd Hg Area Cr ppm Org carb % ppm ppm ppm ppm ppm ppb % Palk strait / 0.38 110 122 8 8-40 34 1-2 107 0.09 Palk Bay Gulf of Mannar 0.35 90 BDL-10 BDL-70 10 BDL-40 BDL BDL 0.3-0.4
  44. 44. 2. Proposed Project and Oceanographic Environmental Setting 2.1 Proposed Project The project envisages a ship navigation channel across Adam’s bridge connecting Gulf of Mannar with Palk Bay and further Palk Bay with Bay of Bengal with dredging of navigational channel in Palk strait. The project enables the direct movement of ship between the east & west coast of the country instead of going via Srilanka. The route will originate from Tuticorin harbor, extend N-E up to south of Pamban island using available navigation depths which is more than 20 m, cut through Adam’s Bridge where a channel will be required to be dredged with depth suiting the draft requirement and proceed parallel to medial line for fishing rights in Palk Bay through available navigation depth, pass through a channel to be created in Palk strait by dredging and join Bay of Bengal. The construction of ship channel will be done to suit different drafts 9.15m, 10.7m & 12.8m by dredging & Excavation in Adam’s Bridge area and Palk strait. • Tentative specification of Navigational channel are : − First phase : 9.15-m draft. 300m width − Second phase : 10.7 m draft 300m width − Third phase : 12.8 m draft 500 m width • Phase wise development − First phase : control two way traffic − Second phase : control two way traffic − Third phase : two way traffic The project besides creating a channel envisages deployment of Vessel Traffic Management System (VTMS) to be located on Rameshwaram Island and at pt. Calimere to control navigation. Provision will be made for necessary navigational aids which include lighted Fairway Buoys, channel marked, Buoys, Recons, flotilla etc.
  45. 45. NEERI has undertaken studies for assessing environmental status of the region and have engaged services of National Ship Design Research Center (NSDRC), Visakhapattanam for oceanographic & hydrographic surveys besides drilling operations along proposed alignment, to collect borehole data. Services of National Hydrographic Office (NHO) Dehradun were engaged to conduct bathymetry and bottom profile studies in Palk Bay Strait area. 2.2 Oceanographic Status in Project area along Route Alignment The stability of the study area along the alignment is influenced by number of environmental factors, primarily due to geological, biological, meteorological and oceanographical parameters, which distinctly vary from one sector of the coast to another. The most influencing factors in coastal waters are the tides, waves and currents, and they interact each other to produce an energy input, which shapes and modifies the shore. Any attempt to study these problems require a thorough understanding of the factors and processes involved in the coastal geomorphological system, the pattern of sediment transport in the littoral zone, the volume of exchange of littoral drift from one region to another, the monthly and seasonal variation, and the intermittent oceanographic factors acting on the system. 2.2.1 Waves The winds blowing over the ocean surface has the direct effect on wave generation as it is related to wind speed, extent of fetch and wind duration. Pilot (1953) gives a detailed account of the southern part of the Bay of Bengal. The oceanographic pattern along the Indian coast is mainly governed by the monsoons. The southwest monsoon influences this pattern from June to September. The average speed of the wind during southwest monsoon period is about 35 km per hour frequently rising up to 45-55 km per hour. The average speed of the wind during northeast monsoon (October to January) prevails around 20 km per hour. Tropical storms known as cyclones frequently occur in the Bay of Bengal during October to January. In eastern coast, the wave activity is significant both during southwest and northeast monsoons.
  46. 46. 2.2.1.1 Wave Measurement The observations on wave measurement show that significant wave height varied from 0.46 to 1.12 m in March, 0.33 to 1.18 m in April, 0.46 to 1.74 m in May, 0.71 to 1.78 m in June, 0.68 to 1.6 m in July, 0.68 to 1.49 in August, 0.64 to 1.76 m in September, 0.54 to 1.35 m in October, 0.40 to 1.13 m in November, 0.40 to 1.12 m in December, 0.35 to 1.03 m in January and 0.35 to 1.23 m in February. Measured significant wave height is given in Fig. 2.1 The maximum wave height varied from 0.67 to 1.78 m in March, 0.44 to 1.73 m in April, 0.66 to 2.81 m in May, 0.98 to 2.72 m in June, 0.91 to 2.45 m in July, 0.89 to 2.48 in August, 0.89 to 2.96 m in September, 0.66 to 2.94 m in October, 0.59 to 1.60m in November, 0.48 to 1.73 m in December, 0.47 to 1.68 m in January and 0.45 to 1.79 m in Febraury. Wave heights are relatively higher during southwest monsoon. Measured maximum wave height is depicted in Fig. 2.2. Monthly variation of breaking wave height (m) is depicted in Table. 2.1 The wave direction (with respect to north) mostly prevailed 140O to 230O in southwest monsoon (June to September), 85O to 150O during northeast monsoon (October to January), and 90O – 200O during fair weather period (February to May). The wave direction is highly variable in January and May. The zero crossing wave period predominantly varied 3-8 s in December to April, 4-10 s in May and 4-9 s during rest of the year. The wave heights recorded in west and east coast offshore area of India are compared. In west coast the wave heights off Mumbai are in between 2.0-6.0 m in southwest monsoon, 2.0-3.0 in north east monsoon, and 1.0-2.5 m in fair weather period. Off Goa the wave heights are between 0.8-5.1 m in southwest monsoon. Off Mangalore wave heights are around 3.2 m in southwest monsoon and 0.8 m in fair weather period. Off Trivandrum the wave heights are 2-4.3 m in southwest monsoon and 1-2.0 m in fair weather period. Off Cochin the wave heights are between 0.9-2.0 in southwest monsoon. In east coast off Chennai the wave heights are 2.5 m in southwest monsoon and 1 m in northeast monsoon. Off Visakhapatnam coast these heights are between 0.8-3.9 m in southwest monsoon 0.6-2.9 m in northeast monsoon and 0.5-3.8 m in fair weather period. Off Orissa the wave heights are between 1.0-2.5
  47. 47. m in southwest monsoon and 0.8-2.5 m in northeast monsoon, and around 1-2.2 m in fair weather period. The wave climate reported in the literature indicates that the wave activity in the study region remains relatively low compared to the rest of Indian coast. 2.2.1.2 Wave Refraction Tuticorin to Arimunai Wave refraction during the southwest monsoon shows appreciable divergence of wave orthogonal near Adams Bridge, Arimunai, and south of Sippikulam. Wave activity was found to be extremely reduced between Mandapam and north of Valinokkam due to the presence of offshore islands, which causes waves to break offshore. Wave energy concentration was observed at Mukkuperiyar, Valinokkam, Mukkaiyur and Vember. The region between Sippikulam and Tuticorin is again protected from southwestern waves due to the presence of islands. The presence of offshore islands is observed to protect the coastal stretch from Mandapam to Valinokkam, and Veppalodai to Tuticorin from northeasterly waves. Wave refraction between Tuticorin and Arimunai during NE Monsoon and SW Monsoon is shown in Figs. 2.3-2.5 respectively. Arimunai to Vedarnyam This segment of the coastline lies in Palk Bay and waves propagating from south (during southwest monsoon and fair weather period) do not enter in this region. Studies are indicating that even during the northeast monsoon, waves are found not entering the bay and get attenuated across the shoals of middle banks and south banks between Vedaranyam (India) and Matakal (Sri Lanka). Part of wave energy with less magnitude enters the bay through Pedro Channel and reach the coast between Puduvalasai and Gopalpatnam. Wave refraction between Arimunai and Vedaranyam during NE Monsoon is shown in Fig. 2.6 respectively.
  48. 48. 2.2.1.3 Wave Period During southwest monsoon, the wave period predominantly persisted 9 –10 s between Vembar and Keelamunadal, and 6 – 8 s between Uthalai and Dhanushkodi. During the northeast monsoon, it predominantly persisted 5 –10 s between Vembar and Keelamundal, and 5 –8 s between Uthalai and Dhanushkodi east. In fair weather period, it remained 6 –10 s along Vembar to Keelamundal, and 9 –10 s along Uthalai to Dhanushkodi. The study shows that the waves approaching the coastline consist of both seas and swells. Monthly variation of wave period is depicted in Table 2.2. Predominent wave character buoy data off Vembar from wave rider is given in Table 2.3. 2.2.2 Tides and Currents The tides in this region are semidiurnal. The various important tide heights with respect to chart datum near Pamban pass are as follows. Mean Higher High Water Springs = 0.70 m Mean High Water Neaps = 0.48 m Mean Sea Level = 0.41 m Mean Low Water Neaps = 0.32 m Mean Low Water Springs = 0.06 m It shows that the average spring tidal range is about 0.64 m and the neap tidal range is about 0.16 m. The tidal range is relatively low compared to the northern part of the Indian coast, which inturn would restrict the influence of tidal currents. 2.2.2.1 Longshore Currents The longshore current speed remained weak (<0.1 m/s) throughout the year between Keelamundal and Vedalai and along the northern coast of Rameswaram from Arimunai to Ariyaman. Consequently, it was relatively moderate (>0.1 m/s) throughout the year between Sippikulam and Naripaiyur and along the southern coast of Rameswaram i.e. from Uthalai to Mukkuperiyar. The spit between Dhanuskodi and Arimunai in Gulf of Mannar experienced relatively stronger currents during fair weather period (March to May) and remained weak during southwest monsoon and northeast monsoon periods (June to February). It indicates that the stronger currents prevailing in the adjacent coasts during
  49. 49. southwest/northeast monsoons becoming weaker between Dhanushkodi and Arimunai. This phenomenon of sudden weakening of littoral currents causes the littoral drift to deposit and form series of sand shoals near Arimunai. Such prolonged deposition of littoral drift over many years can be attributed to formation of numerous islands and shallow shoals across the strait between Arimunai (India) and Talaimannar (Sri Lanka) called Adam’s Bridge. The Uthalai coast facing Gulf of Mannar experienced stronger longshore currents (0.2 – 0.5 m/s) throughout the year, followed by a segment of the coast between Vembar and Naripayur (0.2 – 0.4 m/s) with exposure to relatively high wave energy environment. The prevalence of weak longshore currents between Keelamundal and Vedalai is causing deposition of littoral drift on either side, as evidenced by the occurrence of many offshore islands and submerged shoals. Although the Pamban Pass, connecting Palk Bay and Gulf of Mannar break the continuity of longshore current between the mainland and Rameswaram Island, the magnitude of the current on either side of Pamban Pass is found to be very weak. This reduces the volume of littoral sediments approaching the Pamban Pass which inturn reduces the quantity of sediment passing through Pamban Pass from Gulf of Mannar to Palk Bay. The longshore current direction prevailed northerly during southwest monsoon and fair weather period, and southerly during northeast monsoon between Sippikulam and Uthallai. The entire coast of Rameswaram facing Gulf of Mannar, experienced the current in westerly direction throughout the year, except in June and July. This phenomenon of northerly currents along the mainland and westerly current along Rameswaram create a zone, wherein, most of the littoral drift will get deposited. Only a fractional proportion is expected to move from this region by tide induced currents towards the Adams Bridge. This would reduce the volume of littoral sediment reaching the Adam’s Bridge and intrun. The quantity of sediment entering Palk Bay from Gulf of Mannar. These sediments deposited at shoals is supplied back to the littoral system for the mainland, when the longshore currents move towards south during the ensuing northeast monsoon.
  50. 50. Although the longshore current was extremely weak along the sand spit facing Palk Bay, it tends to be easterly during southwest monsoon/fair weather period and westerly during northeast monsoon. Similarly, at Ariyaman, the longshore current direction was southerly during southwest monsoon/fair weather period and northerly during northeast monsoon, indicating just opposite to the phenomenon observed in Gulf of Mannar. Such processes once again indicate the accumulation of littoral drift on either side of Rameswaram Island during southwest monsoon and removal during northeast monsoon, making this region as a sediment storage reservoir. Monthly variation of longshore current (m/s) is given in Table 2.4. 2.2.2.2 Currents Studies Continuous measurements on tidal current speed and direction were carried out for three seasons at 4 locations viz., i) stn. C1 - off Arimunai-Adam’s Bridge, ii) stn. C2 - off Uthalai (Gulf of Mannar), iii) stn. C3 - Pamban Pass, and iv) stn. C4 - off Tharuvai (Palk Bay). The measured currents were resolved into parallel and perpendicular components with respect to the coastline. The variation of current speed and direction and the resolved components are presented in Figs. 2.7 to 2.35. Southwest monsoon (June to September) Near Arimunai (stn. C1) the average current speed occurred around 0.2 m/s with the maximum and minimum speed of 0.3 m/s and 0.05 m/s respectively both at surface and bottom (Fig. 2.7). The variation of current direction had not followed the tidal phase. It showed consistent northwesterly flow over one tidal cycle and changed to southeasterly flow for the subsequent tidal cycle. It indicates that current shifted its flow direction for alternate tidal cycles rather than flood and ebb tidal phases. The shore parallel component of currents indicates that for larger tidal range, the flow was in westerly direction and for small range in easterly direction. The shore perpendicular component of currents indicates that the flow consistently existed from Gulf of Mannar into Palk Bay. The northwesterly and southeasterly currents over different tidal cycles were found to be equally predominant.The component of currents near surface and bottom off Ariminai during southwest monsoon is depicted in Fig. 2.8 and Fig. 2.9 respectively. At Uthalai (stn. C2) in Gulf of Mannar, the average current prevailed around 0.1 m/s with the maximum and minimum of 0.2 m/s and 0.05 m/s respectively (Fig.
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