High resolution bathymetric mapping of the Indian

Exclusive Economic Zone

Abhishek Tyagi, Dr. John Kurian P.

National Centre for Antarctic and Ocean ResearchMinistry 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.

3

REGIMES CHART

1000

2000

3000

5000

4000

Oceanic crust (basalt)

Shelfedge

Geologicalslope

GCCS (4)LLLaaannnddd

Continental crust (granite)

Base ofthe slope Geological

rise

GCHS (26-30) High Seas

3Nautical Miles

12Nautical Miles

24Nautical

Miles

200Nautical

Miles

0

Depth inmeters

OOOccceeeaaannn

UNCLOS (3)

UNCLOS (33) UNCLOS (57)

UNCLOS(87,112-115)

High Seas

UNCLOS (79,113-115)

TerritorialSea

ContiguousZone Exclusive Economic Zone UNCLOS (58, 113-115)

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)

Continental MarginsFrom 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

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

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 1/3rd 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

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

Echo sounder (also called SONAR) • Invented in the 1920s • Primary instrument for measuring depth • Reflects sound from ocean floor

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)

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

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

Spaceborne

Bathymetric Mapping Tools

Airborne

Shipborne

10,000m

2m

NEARSHOREOFFSHORE

barrierreef

lagoon fringingreef

TideGauge

Hull-mounted vs towedHull-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 towedTowed (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 cruiseSidescan 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

NIO, Goa - Shallow waters (West Coast) NIOT, Chennai - 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 km2

• 12th 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.

Description Area (sq. km.)

Total Area of Indian EEZ (Source: World EEZ-v4) 2372298

Area with more than 500 m depth 1875378

Area with less than 500 m depth 496920

Area of EEZ around Mainland (East coast and West coast) 1697775

Area of EEZ around Andaman & Nicobar Islands 684933

Details of Indian EEZ areal extents

Implementation

Segment-I : Upto 500m depth

Segment-II: Beyond 500m depth

Vessel ORV Sagar Kanya

RV Sagar Nidhi

RV-Akademik Boris Petrov

RV-Akademik Nikolaj Strakhov

Make L3-Comm. Elac-Nautik

Reson Atlas Elektronik Reson

Model SB3012 Seabat 7150 Hydrosweep-DS2 Seabat 7150Frequency of operation 12 kHz 12 KHz 15 kHz 12 kHz

Number of Beams 201 Upto 880 59 / 240 (HDBE) 234

Swath Coverage Upto 5 x Depth Upto 5 x Depth Upto 3.5 x Depth Upto 5 x DepthBeam Width Upto 140° Upto 150° Upto 120° Upto 150°Beam Width 1° 2° 2.3° 2°

Depth of performance Upto 11,000m Upto 10,000m/ 6000m

Upto 10,000m Upto 10,000m/ 6000m

Acquisition software Hydrostar PDS2000 Hydromap Online PDS2000Post processing Eiva NaviPac PDS2000 Hydromap Offline PDS2000

Specifications of MBES used for deep water surveys

In India, the first multi-beam ‘Hydrosweep-DS’ system was installed onboard Oceanographic Research vessel (ORV) SAGAR KANYA in 1990

Vessel RV Sagar Sukti RV-Sindhu Sankalp

CRV- Sagar Purvi

CRV-Sagar Pachimi

Make Kongsberg Kongsberg Kongsberg Reson

Model Simrad EM1002 Simrad EM1002 Simrad EM1002 8101

Frequency of operation 95 kHz 95 kHz 95 kHz 240 kHz

Number of Beams 111 111 111 101

Swath Coverage Upto 7 x Depth Upto 7 x Depth Upto 7 x Depth Upto 7.5 x Depth

Beam Width Upto 150° Upto 150° Upto 150° Upto 150°

Beam Width 2° 2° 2° 1.5°

Depth of performance Upto 1,000m Upto 1,000m Upto 1,000m Upto 300m

Acquisition software Neptune Neptune Neptune PDS2000

Post processing SIS, Cfloor SIS, Cfloor SIS, Cfloor PDS2000

Specifications of MBES used for shallow water surveys

•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

Results