Delimitation of Indian Continental Shelf

Continental Shelf survey and the submission of claims to the United Nations for sovereignty over the waters of marine states are a topic of hot discussion in the marine world. Some marine states have already submitted claims and many others plan to render theirs by the end of 2009. One of the latter is India, which has completed all the relevant hydrographic and marine geophysical surveys and acquired the Scientific and Technical data. The Naval Hydrographic Department is one active working partner and a leading hydrographic survey agency in India has been supporting the project through its bathymetric surveys. These will be used as a reconnaissance tool for delineation of foot of the continental slope and to construct a cut-off line. This line either shall not exceed 350 nautical miles(M) from the baseline from which the territorial sea is measured, or shall not exceed 100M from the 2,500 metre(m) isobath.

The Continental Shelf of a coastal state comprises the seabed and subsoil of submarine areas extending beyond its territorial sea throughout the natural prolongation of its land territory to the outer edge of the continental margin, or, where the outer edge of the continental margin does not extend to that distance, to 200 nautical miles from the baselines from which the breadth of the territorial sea is measured. The continental margin comprises the submerged prolongation of the landmass of the coastal state and consists of the seabed and subsoil of the shelf, the slope and the rise. It does not include the deep and ocean floor with its oceanic ridges or the subsoil thereof (UNCLOS, Article 76, paragraph 1 & 4a).
The United Nations Convention on the Law of the Sea (UNCLOS) came into force on 16th November 1994. It includes provisions for establishing the various maritime zones of a coastal state, such as the Territorial Sea up to a distance of 12M, from the baseline, the contiguous zone of 24M, the Exclusive Economic Zone (EEZ) of 200M, and Outer Limits of the continental shelf beyond 200M. While the Territorial Sea, contiguous zone and EEZ follows essentially from the baseline, the outer limits of the continental shelf have to be established by physical survey in accordance with guidelines contained in the Convention. These aim to clarify the slope and depth of admissible scientific and technical evidence to be examined by the commission during its consideration of each submission for the purpose of making recommendations. These guidelines also clarify the scientific, technical and legal terms contained in the Convention.
Following India’s ratification of the Convention in June 1995, the country is now obliged to lodge her claims for an extended Continental Shelf at the latest by May 2009. To meet this target, a multi-institutional and multi-million Indian Continental Shelf Programme has been implemented by NCAOR (National Centre for Antarctic & Ocean Research) on behalf of the Department of Ocean Development (DoD). As a part of this programme geophysical data has been collected which includes deep-penetration multi-channel seismic reflection, refraction, magnetic and gravity surveys covering over 24,000km from the Bay of Bengal and the Arabian Sea, in and off the EEZ of India. Data collection, processing and interpretation has been carried out under the supervision of several national organisations and institutes such as the National Geophysical Research Institute (NGRI), the Directorate of Hydrocarbons (DGH), the National Institute of Oceanography (NIO) and the Geological Survey of India (GSI) etc. The Naval Hydrographic Department (NHD) is one of these premier organisations and a leading Hydrographic Survey Agency in India has also been contributing its services.
As a working partner in the Continental shelf programme, the National Hydrographic Office (NHO) has been extending its services through hydrographic surveys on behalf of NHD. The NHO completed its baseline surveys in 1998, as per CLCS guidelines. These points for the Indian Coast, Andaman & Nicobar and Lakshadweep islands are being processed for necessary promulgation by the Republic of India under sections 2 and 3 of the Territorial Waters, Continental Shelf, Exclusive Economic Zone and Maritime Zone Act No. 80, 1976. Also in compliance with CLCS guidelines, Naval survey ships conducted bathymetric surveys using single /multi-beam echo sounder and had the data verified at NHO. The foot of the continental slope and the 2,500m isobath were derived based on this bathymetric data, and the same have been forwarded to DoD for further delineation of boundaries beyond 200M. All the co-ordinating organisations/institutes under this programme are working hard to come up with a draft claim by the year 2005.

EEZ Surveys
The NHD has conducted Baseline and EEZ surveys for the Indian Continental Shelf. Being an active partner in the Continental Shelf programme, the Department has taken responsibility for establishing baseline points and deriving Foot of the Continental Slope (FoS) and 2,500m isobath through its bathymetric surveys. On-schedule completion of baseline surveys established Normal and Straight baselines joining the outermost point of the coast, low-water line, low-water reefs and islands, as marked on the large-scale charts published by the Chief Hydrographer to the Republic of India. The sea area enclosed within the normal and straight baseline system shall form the internal waters of the Republic of India. Baseline points were established for the entire Indian Coast, Andaman & Nicobar and Lakshadweep Islands, and the Republic of India is processing the same for necessary promulgation. In accordance with CLCS guidelines, Indian survey ships carried out bathymetric surveys in the Bay of Bengal, Arabian Sea and in the Andaman Sea and the task was completed by the year 2000. The survey data was verified at NHO for its quality as per GIHS, NP145 & SP44 standards.

Methodology
The complete workflow for obtaining final outer limits of the Continental Shelf beyond 200M is shown in the flow chart (Figure 1). NHD has tried its best to complete the tasks of establishing Baselines, Cut-off lines and Formula line through its bathymetric EEZ surveys. The entire Indian Coast and the Andaman & Nicobar Islands, including Lakshadweep, were divided into eight blocks and in each block Foot of the Slope (FoS) profiles were digitised from the Fair Sheets of the respective hydrographic surveys. Care was taken while choosing FoS profiles that the distance between two FoS points was maintained at less than 60 nautical miles. The survey specifications are in compliance with paragraph 9.2.5 of Scientific and Technical Guidelines of the CLCS/11, dated 13th May 1999.
Digitised profile data in the ASCII format were imported into the CARIS LOTS Article 76 (Ver 4.0), which is specially designed for delineating maritime boundaries, including the outer limit of the continental shelf as defined in Article 76 of the Law of the Sea. The procedural specifications, functionality, and user documentation of CARIS LOTS are in compliance with CLCS guidelines. The bathymetric profile data is imported into CARISLOTS through its ASCII Data Import wizard then all data points are connected with a line, using the tool ‘Join points into line’. The profiles are subsequently viewed one by one and analysed using the tool ‘Analyse the foot of the slope’. This displays the profile or 3D line graphically, with the land to the left and deep water to the right. For easy reference to the corridor of interest, three vertical lines are placed on the line: a blue line represents 140M, a green line 200M and a red line the combined cut-off line (Figure 2).
A mathematical function was fitted to the depth profile (i.e. smooth or filter the line) and examined its second derivative. The smoothing value was adjusted by changing the Spatial Frequency till the smoothed line matches with the original line as closely as possible. It was observed that the second derivative line changes with the steepness of the slope. Therefore the foot of the slope was located at the first big change at the base of the slope as we approach from the seaward side (the right). The procedure was repeated for locating FoS points for all the profiles on the East coast (34 profiles), West Coast (42 profiles) and Andaman & Nicobar Islands (27 profiles). The geographic coordinates of 2,500m isobath digitised from the small-scale nautical charts, as well as those from bathymetric surveys, were imported into CARIS LOTS through ASCII Data Import and a line drawn connecting these points.

Results
The Republic of India is processing the baseline points established by the NHD for the Indian coast for necessary promulgation. However, the sovereignty of India extends, and has always extended, to the Historic waters of India and to the seabed and subsoil underlying and the air space over such waters. Historic waters already declared for Palk Bay and Palk Strait and Gulf of Mannar in pursuance of the maritime boundary agreement between India and Sri Lanka by Gazette of India notification No.13, dated 15th January 1977 will continue to remain so. Bilateral talks are in progress between India and Pakistan and both countries agree in principle to conduct a combined survey in the Sir Creek area to delineate the boundaries (News Agencies). Similarly, negotiations with neighbouring marine states over relevant issues are also in progress.
A total of 108 FoS points have been derived based on single-beam bathymetric data. These points have been verified with the multi-beam profile data (NHO surveys) and also with public domain data. Most of the points are in agreement. By joining the FoS points a line has been drafted called the ‘FoS line’. This line might be used to generate a FoS+60M formula line and further calculate the 1% sediment-thickness line (Gardiner Line). The 2,500m-isobath line could be used to generate the cut-off line by adding 100M to seaward or 350M.