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number of steps in the last 10 years to conserve and
manage these mangrove on a sustainable basis.
However, many of their attempts proved futile and two
factors, along with others, responsible for this are
e lack of information as the degree to which this
mangrove wetland is degraded and
e lack of information on the true causes for
degradation.
Remotely sensed data played a crucial role in solving the
above two problems.
2.4 Assessment of degree of degradation of Picha-
varam mangrove using remotely sensed data
The Pichavaram mangrove forest is declared as a
reserve Forest in 1897 and during that time the total area
of the mangrove forest was about 700 ha. However, due
to various reasons, the extent of this mangrove forest
has degraded drastically. Though, the Government
management agencies were aware of the degradation,
they were unable to quantify the area of the degraded
mangrove since conventional method of surveying was
not possible in the mangrove wetlands. This lack of
information, along with other reasons, impaired the
Government agencies to prepare a reliable conservation
and management plan. However, using Indian Remote
Sensing Satellite (IRS) data, it was found that nearly
62.896 of the Pichavaram mangrove forest was degraded
between the years 1897 and 1994 (Figure.1a & 1b) and
the rate of degradation was about 5 ha per year. The
above information was passed on to the Government
agencies which made them to realise the urgency for the
restoration and conservation of this important
mangroves. Now, the Government agency is also using
remotely sensed data to analyse the extent of
degradation in other mangrove of Tamil Nadu.
2.2 Analysis of the causes for the degradation of
Pichavaram mangroves using remote sensing
It was considered both by the Government agencies and
research Institutions working in the Pichavaram are that
cattle grazing and illegal felling were the main causes for
the degradation. However, remote sensing analysis by
creating False Colour Composites (FCC), ratioed output,
and vegetation indices showed that the degradation was
severe in the middle portion. This indicated that apart
from grazing and felling there could be some other
reasons for degradation since if there two factors were
alone responsible for degradation then the peripheral
areas should have affected more rather than the central
portion. This assumption led the M.S. Swaminathan
Research Foundation to conduct intensive ecological
studies which revealed: that changes in topgraphy into
"rough" shaped and stagnation of tidal water in the
trough were tha main cause for the degradation. Thus,
for the first time one of the main causes for degradation
was indentified and on the basis of which restoration
techniques were developed and successfully
demonstrated.
2.3 Analysis of shoreline changes and its impact on
. Mangroves
The Pichavaram mangrove is being protected from wave
action by a long stretch of sandy beach. However,
comparison of Survey of India toposheet and. remote
sensing imageries of IRS 1B LISS Il revealed that
breadth of this beach reduced by 550m between 1930
and 1970 (Figure 2) and about 150m betwween 1970
and 1992 (Figure 3). The rate of erosion is about
13m/year. This indicated that there is danger of the
Pichavaram mangroves exposed directly to the open sea
where the wave action is very high which will not allow
the establishment and regeneration of mangrove plant
genesis. Apart from these, comparison of topsheets and
recent remote sensing imageries also indicate that which
the Pichavaram mangroves erosion and sedimentation
occurs simultaneously. This indicated by the
enlargement of some islands and sedimentation of some
of the tidal creeks and canals. All there will have severe
impact on mangrove plant communities and
hydrodynamics.
Considering all the aspects explained, a long term
management plan is being prepared for the Pichavaram
mangroves in which both remotely sensed data and
Geographic Information System are used extensively. On
the basis of this experience similar kind of work is also
being undertaken at Bhitarkanika mangrove of Orissa.
(Figure.4)
3. APPLICATION OF GEOGRAPHIC INFORMATION
SYSTEM IN SOCIO- ECONOMIC STUDIES
The application of Geographic In-formation System is
spreading very widely in all disciplines. In MSSRF GIS is
applied in evaluating various socio economic factors of
Dharmapuri district of Tamil Nadu. The different factors
in block level like Infant mortality ratio, birth rate, death
rate, population below poverty line, Scheduled Caste &
Scheduled Tribe population below poverty line, sex ratio,
female literacy etc. were overlaid and the status of the
blocks were identified based on the given factors by
giving weightages to each layer based in the importance
of them in well-being of human life.
In addition to these, it has been proposed to carry out the
following work in the collaboration with other remote
sensing apllication agencies.
1. Evolving a coastal zone management system and its
monitoring in Tamil Nadu - Using remotely sensed
data and Geographic Information System -
Submitted in collaboration with Space Application
Centre, Ahmedabad to the Department of Ocean
Development, Govt. of India, New Delhi
To map the landuse and wetland maps at three
years interval as well as turbidity, sea surface
temperature and primary productivity using satellite
data for the Tamil Nadu coast. The remote sensing
based data and environmental data will be integrated
to prepare coastal zone management plans. These
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
