High resolution bathymetric mapping of the Indian Exclusive Economic Zone

Abhishek Tyagi, Dr. John Kurian P.

National Centre for Antarctic and Ocean Research Ministry of Earth Sciences (Govt. of India) Headland Sada, Vasco da Gama, Goa-403 804

Under the United Nations Convention on Law of the Sea (UNCLOS), the Exclusive Economic Zone or EEZ is covered by Articles 56, 58 and 59.

The UNCLOS or the Law of the Sea Treaty, is the international agreement that defined the limits of the territorial seas of nations and the areas in which they could exploit marine resources.

The EEZ is defined as that portion of the seas and oceans extending up to 200 nautical miles in which coastal States have the right to explore and exploit natural resources as well as to exercise jurisdiction over marine science research and environmental protection.

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3 Nautical Miles UNCLOS (3) 12 Nautical Miles UNCLOS (33) 24 Nautical Miles UNCLOS (57) 200 Nautical Miles L a n d GCHS (26-30) High Seas LEGAL REGIMES : UNITED NATIONS LAW OF THE SEA CONVENTION 1982 (UNCLOS) GENEVA CONVENTION ON THE HIGH SEAS (April 29, 1958) (GCHS) GENEVA CONVENTION ON THE CONTINENTAL SHELF (April 29, 1958) (GCCS) Territorial Sea

REGIMES CHART

Zone Exclusive Economic Zone UNCLOS (58, 113-115) UNCLOS (87,112-115) High Seas Depth in meters 0 Shelf edge O c e a n 1000 2000 UNCLOS (79,113-115) GCCS (4) Geological slope Base of the slope Geological rise 3000 Continental crust (granite) 4000 Oceanic crust (basalt) 5000

Main Regions include: Continental Margins, Deep-ocean Basins, Mid-ocean Ridges

• • •

Continental Margins

From the land, submerged edges of the continents : Continental shelf – nearly flat, gradual seaward slope; covered with sediments Continental slope – steeper seaward slope; submarine canyons Continental rise – 0.5° - 1° slope ; composed of sediments

Deep-Ocean Basins

• • • Beyond the continental margins, ocean floor deeper than 2000 m: Abyssal plains – very flat areas at depths of 3-5 km Seamounts – underwater volcanoes, > 1000 m high Deep-sea trenches – steep-sided, long, narrow depressions

Mid-Ocean Ridges

• • • Underwater mountain ranges that are the longest on earth Occupy 1/3 rd of the ocean floor Contain rift valleys at the summits as well as many fracture zones, where rocks have cracked and slid past one another

Bathymetry is Basic Information

•Bathymetry provides information about water depth •Bathymetry gives a descriptive picture of the ocean bottom terrain, revealing the size, shape and distribution of seabed features APPLICATIONS: •For Science Oceanography, geology, biology, ecology • For Economics and Infrastructure Resource exploration, cable routing, shipping • For Management and Policy Fisheries, Maritime Boundaries, Marine Protected Areas • Defence & Sovereignty issues

Echo sounder (also called SONAR)

• Invented in the 1920s • Primary instrument for measuring depth • Reflects sound from ocean floor HMS Challenger-first to study bathymetry in parts of all the oceans except the Arctic Ocean Achievements: • the first systematic attempt to chart the basins of the world ocean • 492 bottom soundings

Echosounder Operation

• Positioning using GPS • Uses acoustic energy (sound) • Pulse of sound travels through the water column • Lapse in time converted into distance (Source: http://tidesandcurrents.noaa.gov/images/hydro_ship.png

)

Technologies have evolved to survey the ocean floor more accurately & widely

http://www.earthguide.ucsd.edu/earthguide/diagrams/sonar/sonar.html

Shipborne

Bathymetric Mapping Tools

Spaceborne Airborne 10,000m

OFFSHORE

Tide Gauge

barrier reef

2m

lagoon fringing reef NEARSHORE

Hull-mounted vs towed

Hull-mounted (i.e., most swath bathymetry systems):

• Fixed mounted on the ship; don’t require repeated deployment • Can collect data while ship is being used for other purposes (e.g., physical oceanographic cruise) • Fast surveying (ship can travel at ~10 knots) • Acoustically noisy (near-surface turbulence and ship noise) • Resolution constrained by near-sea-surface location • Hard to access for repairs, and • Compatibility with certain hull shapes

Hull-mounted vs towed

Towed (i.e., most sidescan sonar systems):

• Location of fish with respect to ship must be measured or calculated • Deployment/retrieval, ship speed must be slow ~2 Knots • Operate in quieter water at greater depth • Easier to move from ship to ship • Must be deployed each cruise

Sidescan sonar Multibeam sonar

(Source: http://www.nauticalcharts.noaa.gov/hsd/images/SW_WhatIs_image.jpg

)

INDIAN EEZ MAPPING PROGRAMME



To prepare a comprehensive seabed topographic map for the entire EEZ of the country using the multibeam swath bathymetric systems.

NCAOR Responsibilities

 

Bathymetric survey beyond 500m, data interpretation, analysis, maps preparation etc.

Archival of all data collected by the participating institutes.

Participating Agencies

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NIO, Goa

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NIOT, Chennai - Shallow waters (West Coast) - Shallow waters (East Coast & Andaman region) Vessel’s utilised for Deepwater Survey ORV Sagar Kanya RV Sagar Nidhi RV Ak. N. Strakhov

• • Indian EEZ covers about 2.37 million km 2 12 th largest EEZ in the world

• The MBES technology requires different set of instruments with different operating frequency and technique to undertake bathymetric surveys for shallow and deep water regimes and since the Indian EEZ is having a wide range of bathymetric depths (i.e., upto ~4000 m), the entire EEZ has been divided into two segments viz. Segment-I with areas having bathymetric depth less than 500 m, and Segment-II with areas having bathymetric depth more than 500 m.

• Technically, shallow waters, less than 500 m water depth need to be surveyed using higher frequency MBES systems while the deep-waters more than 500 m water depth need to be surveyed with lower frequency systems.

• To understand the source of sediment fluxes, their transport mechanisms and to assess the potential of seabed resources, sediment samples are also being collected in a systematic manner during the course of the surveys. Analysis of the sediment samples essentially aid to assess the potential resources as well as to reconstruct the palaeoceanographic conditions and paleoclimatic history.

Implementation

Segment-I : Upto 500m depth Segment-II: Beyond 500m depth

Details of Indian EEZ areal extents Description

Total Area of Indian EEZ (Source: World EEZ-v4) Area with more than 500 m depth Area with less than 500 m depth Area of EEZ around Mainland (East coast and West coast) Area of EEZ around Andaman & Nicobar Islands

Area (sq. km.) 2372298 1875378 496920 1697775 684933

Specifications of MBES used for deep water surveys

Vessel ORV Sagar Kanya RV Sagar Nidhi RV-Akademik Boris Petrov RV-Akademik Nikolaj Strakhov

Reson Make L3-Comm. Elac-Nautik Model SB3012 Frequency of operation 12 kHz Number of Beams Swath Coverage Beam Width Beam Width Depth of performance Acquisition software Post processing 201 Upto 5 x Depth Upto 5 x Depth Upto 140 ° Upto 150 ° 1 ° Upto 11,000m Hydrostar Eiva NaviPac Reson Seabat 7150 12 KHz Upto 880 2 ° Upto 10,000m/ 6000m PDS2000 PDS2000 Atlas Elektronik Hydrosweep-DS2 15 kHz 59 / 240 (HDBE) Upto 3.5 x Depth Upto 120 ° 2.3

° Upto 10,000m Hydromap Offline Seabat 7150 12 kHz 234 Upto 5 x Depth Upto 150 ° 2 ° Upto 10,000m/ 6000m Hydromap Online PDS2000 PDS2000 In India, the first multi-beam ‘Hydrosweep-DS’ system was installed onboard Oceanographic Research vessel (ORV) SAGAR KANYA in 1990

Vessel

Specifications of MBES used for shallow water surveys

RV Sagar Sukti RV-Sindhu Sankalp CRV- Sagar Purvi CRV-Sagar Pachimi

Make Model Frequency of operation Number of Beams Swath Coverage Kongsberg Simrad EM1002 95 kHz 111 Upto 7 x Depth Kongsberg Simrad EM1002 95 kHz 111 Upto 7 x Depth Kongsberg Simrad EM1002 95 kHz 111 Upto 7 x Depth Reson 8101 240 kHz 101 Upto 7.5 x Depth Beam Width Beam Width Depth of performance Acquisition software Post processing Upto 150 ° 2 ° Upto 1,000m Neptune SIS, Cfloor Upto 150 ° 2 ° Upto 1,000m Neptune SIS, Cfloor Upto 150 ° 2 ° Upto 1,000m Neptune SIS, Cfloor Upto 150 ° 1.5

° Upto 300m PDS2000 PDS2000

Results

• During the course of the high-resolution multibeam bathymetric mapping of the Indian EEZ, several geomorphological, structural and tectonic features have been mapped including ridges, seamounts, knolls, abyssal hills, levees etc.

• Some of the known features are now mapped with enhanced accuracy and resolution, hence providing better ideas about geomorphic and evolutionary history.

• Integrated analysis of the bathymetric data, coupled with geological and geophysical information from the region would provide new insights into the regional tectonics, tectonic evolutionary history and basin evolution.

• Revealed presence of a new channel-levee system in the lower fan region of Bay of Bengal. Preliminary analysis of the data inferred that these submarine channel-levee systems have served as pathways for turbidity currents and other sediment-gravity flows to transport and deposit sediments from the continents to deep basins of the Bengal Fan.

• Parts of the Ninetyeast ridge and Laccadive ridge have also been mapped and better resolution geomorphologies of these sections have been prepared.

THANKS