Management of Coral Reefs in Gulf of Mannar using Remote Sensing and GIS Techniques – with Reference to Coastal Geomorphology and Land Use

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Management of Coral Reefs in Gulf of Mannar using Remote Sensing and GIS Techniques – with Reference to Coastal Geomorphology and Land Use

Bathymetry Mapping
Bathymetry map of study area on 1: 50,000 scale was prepared manually using 1975 Naval Hydrographic Chart. The prepared bathymetry map was digitized into ARC-INFO and a digital bathymetry map was prepared. The prepared bathymetry map was updated during fieldwork, which was carried out during April 1999. The depth of the sea bottom was measured (within 10m depth) using ecosounder around Mandapam and Tuticorin groups of islands and some coastal regions near Tuticorin and Mandapam coastal area. The depth values are recorded at a particular location with reference to chart datum (1975). The measured depths values were tide corrected with respect to time and then converted with respect chart datum (0.2m accuracy). Measured tide table from the Tuticorin port was used for final data conversion to chart datum. The locations where the depths were measured with their corresponding Lat/Long and the changes in bathymetry are given in Tables 1 and Table 2.

Table 1. Changes in Bathymetry for about 24-year period between Tuticorin and Sippikulam Coastal Area

Sl.No	Site	Geographic Lat/Long	Depth (m)1975	Depth (m)1999	Changes (m)
1	Tuticorin	78°10’26’’E-8°47’1’’N 78°10’33’E-8°49’11’’N	1.00 2.00	0.6 1.7	-0.34 -0.33
2	Vellaippatti	78°10’30’’E8°51’15’’N 78°11”29’’E8°51’23’N	1.00 2.00	0.91 2.08	-0.09 +0.08
3	Taruvaikkulam	78°11’51’’E8°53’17’’N 78°11’21’’E8°53’17’’N 78°11’21’’E8°53’16’’N 78°11’21’’E8°53’24’’N	1.00 2.00 2.00 1.00	0.6 1.7 1.7 0.6	-0.04 -0.13 -0.13 -0.04
4	Sippikulam Coast	78°15’2’’E-8°59’21’’N 78°15’3’E-8°59’18’’N	1.00 2.00	0.5 0.6	-0.65 -1.24
5	Vilangu Shuli Island	78°16’7’’E-8°56’17’N 78°16’4’’E-8°56’17’’N 78°16’13’’E8°56’19’’N 78°16’15’’E8°56’24’’N 78°16’17’’E-8°56’6’’N 78°16’22’’E-8°56’2’’N 78°16’3’’E-8°55’31’’N 78°15’34’’E8°55’29’’N	1.00 2.00 1.00 2.00 1.00 2.00 1.00 2.00	1.6 1.6 1.6 1.6 1.7 2.9 1.1 1.47	+0.06 -0.94 +0.06 -0.94 +0.87 +0.69 +0.11 -0.53
6	Van Island	78°12’19’’E-8°50’6’’N 78°12’16’’E-8°50’6’’N 78°12’16’’E8°50’10’’N 78°12’25’’E8°49’33’’N 78°12’25’E-8°49’30’’N 78°13’7’’E-8°49’23’’N 78°13’23”E8°49’28’’N	1.00 2.00 2.00 1.00 2.00 1.00 2.00	0.05 1.52 0.50 0.55 0.96 1.06 3.19	-0.95 -0.48 -1.50 -0.45 -1.04 +0.06 +1.19

Table 2. Changes in Bathymetry for about 24-year period in Mandapam Coastal Area

Sl.No	Site	Geographic Lat/Long	Depth (m)1975	Depth (m) 1999	Changes (m)
1	Pamban Channel	79°12’14’’E-9°16’21’’N 79°12’14’’E-9°16’4’’N	1.00 1.00	0.25 0.42	-0.75 -0.58
2	West of Kundugal	79°12’31’E-9°15’17’’N 79°13’31’’E-9°15’17’’N	1.00 2.00	0.85 0.42	-0.15 -1.58
3	Thoniturai Coast	79°10’29’’E-9°16’21’’N 79°10’19’’E-9°16’12’’N	1.00 2.00	0.95 1.07	-0.05 -0.93
4	Marakkayar Pattinam	79°7’6’’E-9°15’33’’N 79°6’56’E-9°14’33’’N	2.00 2.00	1.07 1.50	-0.93 -0.50
5	Musal Island	79°3’12’’E-9°12’9’’N 79°3’2’’E-9°12’9’’N 79°3’8’’E-9°11’17’’N 79°2’32’’E-9°11’7’’N 79°4’12’’E-9°11’9’’N 79°4’12’’E-9°11’19’’N 79°4’35’’E-9°11’25’’N 79°5’23’’E-9°11’25’’N 79°5’23’’E-9°11’15’’N	0.05 1.00 0.50 1.00 1.00 0.50 1.00 0.05 1.00	0.64 1.07 0.64 1.07 0.64 0.42 0.28 0.42 0.64	+0.14 +0.07 +0.14 +0.07 -0.42 -0.08 +0.28 -0.08 -0.36
6	Manalli Island	79°6’32’’E-9°12’24’’N 79°7’32’’E-9°12’21’’N 79°7’34’’N-9°12’15’’N 79°9’28’E-9°12’23’’N 79°8’6’’E-9°12’22’’N 79°8’11’E-9°12’31’’N	1.00 0.50 1.00 0.50 0.58 0.70	0.42 0.42 0.42 0.85 0.21 0.25	-0.58 -0.08 -0.58 +0.35 -0.37 -0.42
7	Pumurichan Island	79°10’38’’E-9°14’27’’N 79°10’25’’E-9°14’23’’N	0.50 1.00	0.25 0.64	-0.29 -0.36
8	Kovi Island	79°11’1’’E-9°13’24’’N 79°11’7’E-9°13’31’’N	1.00 0.50	0.85 0.42	-0.15 -0.08
9	Kursadi Island	79°12’9’’E-9°14’31’’N 79°12’13’’E-9°14’34’’N 79°12’28’’E-9°14’14’’	0.50 1.00 0.50	0.42 0.42 0.42	-0.08 -0.58 -0.08

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