High resolution bathymetric mapping of the Indian Exclusive Economic Zone

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High resolution bathymetric mapping of the Indian
Exclusive Economic Zone

• Abhishek Tyagi, Dr. John Kurian P.

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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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UNCLOS (3)
UNCLOS (33)
UNCLOS (57)
3
12
24
200
Nautical
Nautical
Nautical
Nautical
Miles
Miles
Miles
Miles
GCHS (26-30) High Seas
UNCLOS (87,112-115)
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)
High Seas
Territorial Sea
REGIMES CHART
Depth in
Contiguous Zone
meters
Exclusive Economic Zone UNCLOS (58, 113-115)
0
Shelf
edge
O
O
O
c
c
c
e
e
e
a
a
a
n
n
n
1000
2000
Geological
Base of
UNCLOS (79,113-115)
slope
the slope
Geological
L
L
L
a
a
a
n
n
n
d
d
d
3000
GCCS (4)
rise
4000
Oceanic crust (basalt)
Continental crust (granite)
5000
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Continental Margins
Main Regions include Continental Margins,
Deep-ocean Basins, Mid-ocean Ridges

• 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

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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, gt 1000 m high
• Deep-sea trenches steep-sided, long, narrow
  depressions

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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

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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

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• 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

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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/h
ydro_ship.png)
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Technologies have evolved to survey the ocean
floor more accurately widely

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

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Bathymetric Mapping Tools
Spaceborne
Airborne
Shipborne
Tide Gauge
2m
10,000m
NEARSHORE
OFFSHORE
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Hull-mounted vs towed

• Hull-mounted (i.e., most swath bathymetry
  systems)
• Fixed mounted on the ship dont 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

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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

(Source http//www.nauticalcharts.noaa.gov/hsd/im
ages/SW_WhatIs_image.jpg)
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• 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)
• Vessels utilised for Deepwater Survey
• ORV Sagar Kanya RV Sagar Nidhi
  RV Ak. N. Strakhov

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• Indian EEZ covers about 2.37 million km2
• 12th largest EEZ in the world

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• 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.

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Implementation Segment-I Upto 500m
depth Segment-II Beyond 500m depth
Details of Indian EEZ areal extents
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
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Specifications of MBES used for deep water surveys
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 7150
Frequency 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 Depth
Beam 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 PDS2000
Post processing Eiva NaviPac PDS2000 Hydromap Offline PDS2000
In India, the first multi-beam Hydrosweep-DS
system was installed onboard Oceanographic
Research vessel (ORV) SAGAR KANYA in 1990
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Specifications of MBES used for shallow water
surveys
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
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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