|
|
|
Poster Session
P |
Tidal wetland mapping using remotely
sensed data
V. Shreedhara, A.N. Sherieff, M.
Sabappa Reddy
Karnataka State Remote
Sensing Technology Utilization Centre,
Bangalore, India
C. R.
Bannur
karnataka State Council for
Science & Technology, Bangalore, India.
S. R. Nayak,Baldev Sahahi
Spalce Application Centre, Ahmedabad,
India.
Introduction
Information on the coastal zone is
essential for the regional planning, decision
and policy making for futuristic development and
constructive management plans. Wetland, the
prime component of the coastal zone is a dynamic
ecosystem having complex inter-relationship of
hydrology, soil and vegetation. They are lands
transitional between terrestrial and aquatic
systems where the water table is usually at or
near the surface or land covered with shallow
water. Tidal Wetlands have been recognized as a
significant ecosystem which play an important
role in Bio-geochemical cycle by trapping the
silt and clay, recharging the groundwater and
even cleansing certain toxic components from
effluent water, to which they are aptly called
as “Kidneys of landscape”. The tidal wetlands
also provide a unique habitat for flora and
fauna at different trophic level and are
responsible for conserving reproductive
fisheries not only by way of catch but as
feeding, spawning and nursery grounds. Besides,
mangroves and coral reefs are the economical and
major ecosystem of the wetland. Conservation of
these lands lies in their precise identification
and periodically monitoring them over time and
space.
Karnataka forms a part of the
Malabar Coast in the West with extensive
coastline running 320 kms, placed 12 30-150 00 N
and 740 00 750 00 E. indented with promontories,
headlands, picturesque estuaries, encompassing
tidal wetlands essaying complex “Mangroves” and
lengthy linear beaches. The coastal berm is
narrow due to the descending western ghats,
which are aboutted by the sea particularly in
Uttara Kannada part of the coast. The region
comes under the direct influence of the
Southeswest monsoon, receiving very heavy
rainfall during June to August. The climate is
humid. Soil is alluvial in the plain region and
Lateritic down the hilly slopes.
Nevertheless, the coast has foreseen
over the period of time, the growth of undustry
and urbanisation due to its natural harbors and
ports in particular New Mangalore Port, which
has opened new vistas in trade ad commerce,
which along with the commissioning of the sea
Bird has gone to deplete and destruct the virgin
environment, in particular, the wetland
ecosystems by way of discharging the industrial
effluent into the sea, which needs a constant
monitoring, to which remote sensing is an ideal
tool.
Objectives:
The main
objectives of the present study is :
- To Map tidal wetlands through visual
interpretation of satellite data.
- Carry out spatial analysis of wetland
features.
- Contemplate the complied data to monitor the
coastal environment periodically.
Methodology:
IRS LISS II FCC
( transperancy ) of cloudless data of post and
premonsoon seasons where selected for the study
. The base maps were prepared using Survey of
India topographic sheet on 1:50,000 scale. IRS
FCC dipositive were enlarged to 1:50,000 scale
for detailed mapping using a very high
magnification enlarger procom-II. All the tidal
wetlands classes are identified and delineated
based on the standard image interpretation key
(SAC, 1991) with particular emphasis on the
tone, texture, pattern and association of the
individual features. The preliminary
interpretation is followed by ground truth
verification. The spatial analysis of individual
category is carried out finally using the
digital planimeter.
Data
Used:
Standard false colour composite
diapositive (FCC ) of IRS band 2,3 & 4 which
in contrast to B/W image yields better
discrimination of the wetlands categories, are
used in the present study. Two season data of
October and December 1988 has been selected
based on the reproductively cycle of vegetation
present in the wetland areas. The reproductive
cycle of vegetation present in the wetland
areas. Survey of India topographical sheets on
1:50,000 scale were used for the preparation of
base maps, as said elsewhere. Ground truth data
has preted map, in a formatted from.
Results &
Discussions:
Utilizing the visual
interpretation technique and the wetland
classification key, the entire Karnataka coast
has been mapped using IRS data. The salient
features Karnataka coast has been mapped using
IRS data. The salient features of wetlands units
are discussed below and shown in Fig. 1.
Mudflat:
Mudflats are wide
expanse of fine grained soft mud along the
shore. They generally consist of deposits of
clay, silt, ooze, etc. (King 1972). These
mudflats are further classified based on their
relation with tidal condition into 1) High-tide
or supratidalflats, 2) Intertidal slopes &
3) subtaidal zones (Davies, 1972). Along the
Karnataka creeks, on the low lying areas
adjacent to the estuaries, lagoons particularly
near Karwar, Tadri, Kundapur and Mulki. It is
seen from the study the total area covered by
mud flat is 3937 ha. & the same along the
individual estuarine complex is given in Table
I.
Interestingly, it is seen that total
mud flat area is less along the Karnataka Coast
due to the non-formation of the deltas which may
be due to impediment of the sand & silt
along the west flowing rivers, by the way of
construction of innumerable irrigation &
power dams / barrages and non-plain areas due to
the descending western ghats may be ascribed to
the less formation of mud flats. Added to , the
agricultural practices on large scale along the
estuaries encroaching the already formed mud
flats, which invariable affect the spread of
tidal wetlands.
Sand:
Sand is
classified into various units such as beach,
bar, spit. It is identified by its
characteristics white colour in the image in
associating atleast partly of unconsolidated
material mostly of sand grade. It is seen as a
thin white, linear discontinuous crescent shaped
strip all along the coast, carpeted with beach
vegetation & plantation.
Spit, is
defined as a small point or low tongue or narrow
embank,ment of land commonly consisting of sand
or gravel and having one end attached to the
main land and the other terminating to open
water, usually the sea. The observed spits are
of different sizes. The well developed spit is
observed near Malpe, Bengre and Pavinkurve
regions indicating the direction of littoral
drift. The other spits are locatd at Mangalore,
Kundapur & Bhatkal. Bars are submerged
ridges of detrital sediments which are larger
and less regularly shapped . They are found
singly or together and internally terminated. In
the present study Bars have not been identified,
may be due to the submarine topography &
wave pattern along the coast. Shoals are either
submerged ridge, bank or bar producing shoal
consisting of or covered by sand, Mud, gravel or
other unconsolidated materials. Small pockets of
shoals are identified in the estuaries and
lagoons.
Rocky Coast /
Cliff:
Any high, very steep to
perpendicular or over laying face of rock or
earth rising above the shore of the sea. Absence
of sand, mud & water abutting the coast,
ideally classify / categorize the coast as a
cliffy one. In the present study the
cliffed/rocky coast are commonly seen near
Karwar, Malpe & Bhatkal regions and are
steep & lateritic in nature. All headlands
& promontories are rocky in nature and form
elevated platforms.
Mangroves:
Mangroves are unique halophytes aptly
adapted to saline environment, both
morphologically & physiologically. They are
found along rainy, inter-tropical shores on the
low, flat coast lying inside the surf belt, but
within the reach of the tide, colonizing
especially in the bays, lagoons & estuarine
regions. They may form a fairly continuous
firings or be split up into a labyrinth of
islets between the sluggish tidal streams run. A
uniformly hot & wet climate, salt or
brackish water, a soft ground deprived of air
& rhythmic tidal flood are the conditions
under which mangrove plants develop. Mangroves,
based on the characteristic red tone are
identified and delineated in association with
mud flats habitats along the estuarine /
brackish waters, in patches. However, the frings
mangroves cannot be delineated from the adjacent
agriculture plantations commonly seen along the
estuarine banks/ Udupi & Karwar regions,
where the growth is luxuriant & rest are
scattered in thin patches along the estuaries.
The total spatial distribution of Mangroves is
estimated as 815 ha. & their spread in
individual estuarine complex is given in Table –
I. By the field study it is seen that the
Mangroves found on the west coast in particular
Karnataka coast are less complex when compared
to east coast, wherein mangrove forest are found
in abundance especially in Sunderban areas, with
complex variety. About 16 different species were
recorded, the dominant being Rhizophora
mucronata, followed by Avicennea and Sonneratia.
In order to improve the bio-diversity of the
mangroves, a tidal arboretum is planned near the
kundapur area where congenial environment is
created for the flourish of the variety of the
Taxa, to form a gene bank.
| | | | | |
|
