CHAPTER TWO
Literature Review
Land cover change is one of the main research topics of Scientist and Geoligis
. A large amount of paper is published on land use change in different view of
point. These paper are on the basis of Remote Sensing and Geographycal
Information System. Application of Remote Sensing and Geographycal Information
System brings a sensational dimension of the vegetation cover change.Concept of
scale, resolution , and photo interpretation is used for finding out the
vegetation cover changes of Chakoria in cox’s Bazar of Bangladesh.In this study
,mangrove forest cover changes of Chakoria Sundarban has been depicted by usinbg
modern technology RS and GIS.
Land use Bangladesh has evolved through natural forces as well as human need s.
forestland ,cultivated land are the major land use types in Bangladesh. A
large part of the forest land is now under different type s of non-forest land
use , for example . Shifting agriculture, illegal for homestead, shrimp culture
etc .The total land area and is characterized by intensively planted but is mot
efficiently managed (Bashar,2001) . In
Bangladesh, the various land uses is nature. Eight major conflicting land uses
can be identified. The shortage of land is so acute that mare than 50 % farmers
have become landless and many people are compelled to settle in the undeveloped
offshore islands as soon as the appear on the middle of riverbeds, which risking
their lives.(Ullah ,1996). Some of these
undeveloped and unstabilized char lands are inundated during the high tide and
dry out during the low tide. Encroachment of forests for agricultural use and
human settlement near the fringe of forests is very common and in this process
the actual forest land under tree cover is estimated to have gone down to 6
percent at present .( Ullah ,2002)
2.1 THE MANGROVE FOREST
Mangrove are inter – tidal wetlands of the tropical and sub- tropical coastal
environment. Unfortunately, the productive and protective role of the mangroves
has not been duly valued. Consequently , these ecosystems have been neglected.(Siddiqi,2001)
Mangroves are a taxonomically diverse group of salt-tolerant, mainly arboreal,
flowering plants that grow primarily in tropical and subtropical regions (Ellison
and Stoddart 1991). A “mangrove” has been defined as a “tree, shrub, palm
or ground fern, generally exceeding more than half a meter in height, and which
normally grows above mean sea level in the intertidal zones of marine coastal
environments, or estuarine margins” (Duke 1992). (www.coastbd.org). Man grove s
are salt –tolerant forest ecosystem s of tropical and sub – tropical inter
–tidal regions of the world.( Hamilton and Snedaker,1984)
Mangrove forest is a swamp forest of low to tall trees and shrubs, commonly
associated with some salt marsh herbs. Swamp forests occur along the borders of
many tropical shores where wave action is not intense and mud and peat are
deposited. Most plant of this community is halophytes that are well adapted to
salt water and fluctuation of tidal level. Some have stilt or prop roots to help
hold them on the shifting sediments and others have erect root structures that
crop out above the surface. Several species have well developed vivipary of
their seeds, the hypocotyls developing while the fruits still held on the tree.
These seedlings are usually so shaped and weighted that they float long
distances in the sea and thus extensive migration is ensured. Mangrove community
often develops as a distinct halosere. In such areas it is zoned from open water
landward in a series of different species. The landward zone species develop on
sediments and peats which are initially deposited in the seaward zone. These
Changes due to deposition in the swamp often extend the coast outward and from
incipient islands in shallow, quiet water. The swamp when dense also affords
some protection against erosion resulting from violent storms. Thus mangrove
swamps have significant geologic role.(Choudhury et al.1990)
2.1.1Mangrove status of Bangladesh:
According to the location , the mangrove forest of Bangladesh is divided into
three forest zones . they are the Sundernans, the largest productive mangrove
forest of the world , the chokoria Sunderbans which ios now a senuded forest and
the coastal mangrove plantation forest which was started to be raised during the
sixties. According to the recent inventory report ,65% of Sundernans has tre
cover of mor e than 70% , about 30% between 30 and 70% kand about 5% has less
then 30% tree cover . It has been suggested top exploit Sunderban forest at a
level below its optimum productive capacity.
The plantation of mangrove species are managed jpromarily for fuel – wood and
pulp – wood production. At present growing stock in the coastal plalntation is
estimated as 0.606 mllion cubic metre. The Chokoria Sudarbans is a denuded
forest and it started to deteriorate in the sixties . As found in the present
study, this forest area has been denuded almost completely and all over this
area by deforestation. .(Choudhury et al.1990)
2.1.2 Mangrove Species diversity of Chokoria Sundarbans:
There were only 20 tree species in all. They did attain a maximum height of
about 12.0m. Baro baen (
Avicennia tomentosa
) was the most common large tree and grew almost everywhere but they did not
form pure forest anywhere in the area. Except Baro Baen the forest consisted of
Dulia Baen (A.
alba
) Kala Baen (A.
officinalis
). Tushia (
Bruguiera caryophyloides
), Ruhinia ( Kandelia roxburghiana
) and Lasalong ( Aegiceras majus
). In specially low lying area Natinga (Bruguiera
gymnorhiza
), Karamphala (
Carapa obovata
) and Ail (
Carapa moluccensis
) were occasionally found. Gutia (
Ceriops roxburghiana
) formed a dense thicket in the interior of the forest. It occupied mostly as
copies shoots 1.5m to 4.5m high with an upper storey of scattered Baen. A large
area on the western side had pure Nunia forest. On the sea-front and along and
along the banks of the main rivers where the banks are muddy and shelving, Kewra
(
Sonneratia apetala
) was the most frequent species. In the North-west portion of the area where the
land is higher and the river banks were steep and not shelving, Sundri (
Heritiera fomes
) was the main tree species, all gradations from almost pure Sundri forest to
Sundri mixed with Gewa (
Excoecaria agallocha
), Dulia Baen (
Avicennia alba
), Hantal ( Phoenix paludosa
) in gregarious clumps and Urussia (
Tamarix gallica
) with Natinga on lower ground were seen. On the banks of smaller stream, the
commonest trees were Gorjan (
Rhizophora conjugate
), Kala Baen and Keora. Natural regeneration was good throughout, but Nunia
which multiplied itself very easily. All species copied well.
2.2 Deforestation:
Deforestation is removal of trees from existing forest areas. The
primary cause of deforestation in Bangladesh has been population increase, in
addition to such other factors as demand for forest products and fuel wood, and
conversion of forest land to such other uses as agricultural, industrial,
urbanization and development of infrastructures for transportation, energy
production and so on.
Deforestation is a serious environmental concern in Bangladesh. Deforestation is
becoming more and an acute problem with time and is threatening the destruction
of evergreens tropical rainforest of the country at an alarming rate.(UNDP,2001
The other aspect is that forestlands are being encroached upon illegally. Up to
1989, about 76,596 ha of forestlands have been encroached upon in different
forest areas. According to one estimate, forest cover in Bangladesh has declined
from about 15 percent of the total area to 5 percent.
src="new_page_11_files/image002.jpg" alt=Deforestation v:shapes="Picture_x0020_1">
Figure‑2.
1:
Deforestation of the forest
Out of a total area of 2 million ha of forestland, less than half of this area
is actually covered with trees, the estimated rate of deforestation being 8,000
ha per year; 40 percent of forestlands have reportedly been lost from 1960 to
1990. Deforestation rate was 0.9 percent in 1970, but rose to 2.7 percent in
1984-90. Some sources quote satellite surveys and note that forests are
declining at a rate of nearly 70,000 ha per year and Bangladesh has less than
0.02 ha of forest land per person, one of the lowest forest-man ratios in the
world. If the current trend continues, forests are likely to disappear
altogether in the next 35-40 years or earlier. The implication of continued
deforestation is that valuable species may disappear forever. In addition to
habitat loss, the environmental effects of deforestation include soil
degradation, flooding, erosion and above all the danger of climate change.(
Banglapaedia ,2006)
2.2.1 Deterioration of the Mangrove Vegetation:
To quote from the report, “the condition of the forest crop was very poor.
During the last working plan period there was sudden heavy demand of firewood
for salt manufacture. The demand was much heavy than capacity of the forest.
Also with the opening of the Chittagong-Cox’s Bazar highway and along with the
large-scale working of the Garjan forest in the area the concentration of the
management was completely diverted to mainland tropical forest. As a result the
management of the Chokoria Sundarbans forest was seriously neglected and there
was dearth less illicit cutting of the forest in the area which was so
disastrous that hardly any tall tree was available over the whole Chokoria
reserve forest”. Though the natural regeneration was good but due to heavy
incidence, of grazing and partly due to brackishness of water the new
regeneration could not establish and as a result, the condition of the forest
started to deteriorate from bad to worse. Destructive deforestation by clear
cutting of mangrove vegetation in the Chokoria Sundarban forest area was first
noticed remarkably on the aerial photographs of 1981. After stereoscopic
examination of the aerial photographs it was found that about 2104 ha forest
cover had been completely opened for shrimp forming. Recent studies from landsat
TM imagery reveal that the forest vegetation has almost completely been removed
for deforestation and shrimp farming has been established in the area.(Choudhury,1990)
2.2.2 Destructive Deforestation of the Chokoria Sundarbans :
The destructive deforestation of the Chokoria Sundarbans forest is due to
various causes. Amongst them, the management of the forest was the most
important.
Natural disasters also added to accelerate the act of deforestation. Breach of
forest laws like illicit removal of timbers and other forest produces is one of
the most common and most destructive ways of damaging the forest crop. This was
very much rampant in this area. Insufficient forest staff, lack of co-operation
from the local population and the forest produce traders are few of the many
causes of deforestation.
Abuse of pass system was another cause of damage of the forest crop. In the past
the disposal of the forest produce on pass system was one of the commonest and
easiest ways of removal of forest produce. In this system there was very little
control on felling and extraction.
This forest area was subjected to periodic cyclones of severe intensity.
Cyclones of more or less severe intensity occur in this area frequently and
cause large scale damage to forest trees and forest properties. Most of these
storms are followed by storm surge and the damage and destruction caused by
these storms and surge are considerable.
src="new_page_11_files/image004.jpg" v:shapes="Picture_x0020_2">
Figure‑2.2
: Deforestation by domestic animal . The baffaloes are chewing the cud in
the deforest of the forest.
The whole area of the forest was open for grazing by cattle and buffaloes. This
uncontrolled grazing affected seriously the young regeneration and could not
recoup the lost stock. A system of rotational grazing system was enforced to
control the loss due to grazing but a few of forest guard could not control the
traditional grazing. As a result the forest crops started to deteriorate day by
day.
In the past, fishing was permitted throughout the year under the system of
annual fishing permit. Permits for fishing stakes and dry fire wood for the
fishermen were issued separately. This gave the fishermen a chance to enter into
the forest and in the course of extraction o0f fishing stakes and dry fire wood
considerable damages were done to the forest.
The tidal water was thereby blocked and kept in stagnant condition inside the
forest area for a considerable period. The young regeneration falling with in
this area failed to survive in this stagnant saline water. As a result, in most
of these areas natural regeneration was a complete failure. This type of
traditional fishing in the forest area was another important cause of
deforestation. The forest department adopted some limitations and restriction on
this type of devastating fishing system but they failed to enforce them and slow
deforestation continued years together.
The Chokoria Sundarbans came under Government management in 1903. From that
time, 8500 ha of forest remained under the management and full control of the
provincial Forest Department. From the total forest area 7489.8 ha of land
declared as reserved forest and the
rest of 1012.2 ha area was declared as Protected forest. For proper maintenance
and control Bangladesh Forest Department divided the 7489.8 ha of Reserved
forest into two blocks namely Rampur ( 3827.5 ha ) and Charandwip ( 3662.4 ha ).
The mangrove vegetation of Chokoria Sundarbans was subjected to the destructive
deforestation by clear cutting, burning and pond excavation. In the beginning of
the decade of eighty the price of shrimp in the international market rose
remarkably. Some traders became much attracted with shrimp export and found
Chokoria Sundarbans area most suitable for shrimp production.Now the whole area
of Chokoria Sundarbans is under the shrimp farming except some patches of
vegetation on the bank of the rivers and channels.(Choudhury et al ,1990)Then
they open the forest by cutting vegetation and clear them by burning. Some
evidences of destructive deforestation have been shown in the figure No
(2.3&2.4).
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2.3 Remote Sensing overview
Literally the word “remote” means far away from any place and sensing means
acquiring knowledge about anything. Remote sensing therefore stands for having
knowledge or different kinds of information about any object , situation or
phenomenon from a far away distance without going in close contact with that.
Remote sensing is a science that deals with obtaining information about objects
on earth surface by analysis of data, received from remote platform. It involves
analysis of electromagnetic radiation reflected or emitted by earth surface. In
this way, we can identify the feature on earth surface.(Shaha,2007)
The literal meaning of “Remote sensing” is to sensing some thing from a place
where we are not physically present. Its rather simple, as we view the screen of
your computer monitor, you are actively engaged in remote sensing a physical
quantity (light ,a from of energy) emanates from that screen , which is source
of radiation. The radiated light passes over a distance and thus is “remote “to
some extent, until it encounters and is capture by a sensor (our eye) Each eye
sends a signal to a processor (our brain) which records the data and interprets
this into information. Several of the human senses their awareness of the
external world almost entirely by perceiving a variety of signals, either
emitted or reflected, passively from objects that transmit this information in
waves or pulses. In the previous sentence, all sensations that are not received
through direct contact are remotely sensed. (Bhatt,
1993) Thus, remote sensing is the science of acquiring information
about earth's surface without actually being in contact with it. This is done by
sensing and recording reflected or emitted energy and processing, analyzing, and
applying that information. (Shaha,2007)
2.3.1.Component of Remote sensing :
There are five distinct Component of Remote sensing process .Two major steps are
involved in this s process. The first one is the data acquisition and the second
data processing and interpretation. Data acquisition is made by sensors fro,
platforms. (Santra, 2001)
Basic Component of Remote sensing are:
v
Energy source
v
Transmission path
v
Target
v
Platform
v
Sensor
2.3.2 Remote Sensing Satellites
A satellite with remote sensor to observe the earth is called
a remote sensing satellite. Description of various remote sensing satellites
is given
in the following:
src="new_page_11_files/image010.jpg" v:shapes="Picture_x0020_5">
Figure no -2.5
: Remote Sensing Satellite
2.3.3 Types of Remote Sensing
In respect to the type of Energy Resources:
Passive Remote Sensing: Makes use of sensors that detect the reflected or
emitted electro-magnetic radiation from natural sources.
Active Remote Sensing: Makes use of sensors that detect reflected responses from
objects that are irradiated from artificially-generated
energy sources.
2.3.4 SATELLITE REMOTE SENSING
Earth resources technology satellite (ERTS-1)/ later renamed as Landsat-1/ was
the first remote sensing satellite launched by NASA for surveying, mapping and
monitoring of earth resources. Realizing the potentials of this emerging
technology many other countries like France (SPOT)/ India (IRS)/ Japan (JERS)
and Europe (ERS) have entered into this venture. So far five satellites in the
series of Landsat have been launched of which first three are first generation
satellite and carried Return Beamvedicon (RBV) and multi-spectral scanner (MSS)
imaging sensors while the second generation satellites carry apart from MSS an
Advanced Imagining Sensor called Thematic Mapper (TM).Unlike geostationary
satellites/ these remote sensing satellites are sun-synchronous and polar
orbiting type with a repetitive cycle of 16-26 days enabling repeated collection
of data, at the same place at the same local time for continuous monitoring of
the earth resources.
(Rahman, 1998)
src="new_page_11_files/image012.jpg" v:shapes="_x0000_s1030">
Figure no-2.6: ENVISAT
in space .This satellite will provide many different type
of Remote Sensing data.
2.3.5.
LANDSAT
The first satellite designed specifically to monitor the Earth's surface,
Landsat-1. NASA launched it in 1972. LANDSAT was designed as an experiment for
collecting multi- spectral Earth observation data from unnamed satellite
platform. Since that time, this successful program has collected an abundance of
data from around the world from several LANDSAT satellites. A number of sensor s
have been used for LANDSAT series satellite. They are
F
Return Beam Vidicon (RBV)
F
Multi Spectral Scanner (MSS)
F
Thematic Mapper (TM)
src="new_page_11_files/image014.jpg" v:shapes="Picture_x0020_4">
Figure no:-2.7
LANDSAT.
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Table no –1
: Characteristics of LANDSAT TM Missions.
Application of Landsat TM Band :
Table no –2 :
Application of Landsat TM Band
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2.3.6 Remote Sensing Process
Remote sensing is a wide process. This involves emission of electromagnetic
radiation, sensing and recording reflected or emitted energy and processing
analyzing and applying that information. The remote sensing process is described
in the following:
src="new_page_11_files/image016.jpg" v:shapes="_x0000_s1032">
Figure‑2.8 :Remote
Sensing processo
2.3.7 Electromagnetic Spectrum (Alam and Saha, S.D.)
Transmittance
(r)
-
some fraction (up to 100%) of the radiation penetrates into certain surface
materials such as water and if the material is transparent and thin in one
dimension, normally passes through, generally
with some diminution. The amount of refraction (n) is the ratio of the speed of
the light in vocume (c) compared to the speed of light in the substance ,Snell’s
law state that
,n(sinØ)= constant .where Ø is the angle of incisence . the angle of refraction
(Ø2) can be determination by the equation.
(2)
Absorptance (a)
-
some radiation is absorbed through electron or molecular reactions within the
medium; a portion of this energy is then re-emitted, usually at longer
wavelengths, and some of it remains and heats the target.
(3)
Reflectance (p) -
some radiation (commonly 100%) reflects (moves away from the target) and
scatters away from the target at various angles,
depending on the surface roughness and the angle of incidence of
the rays. Because they involve ratios (to
irradiance), these three parameters are
dimensionless numbers (between 0 and 1),
but are commonly expressed as percentages.
Following the Law of Conservation of Energy:
t
+ a +
p = 1.
src="new_page_11_files/image018.jpg" v:shapes="_x0000_s1033">
Figure No-2.9: Reffrction and Reflection of light rays in water.
2.3.8 Spectral Signatures(Bhatt,1993)
For any given material, the amount of solar radiation that reflects, absorbs, or
transmits varies with wavelength. This important property of matter makes it
possible to identify different substances or classes and separate them by their
spectral signatures (spectral curves).Here high reflect is Grass land after that
ia vegetation then pine woods and then silty water. as shown in under this
figure :
src="new_page_11_files/image020.jpg" v:shapes="_x0000_s1034">
Figure No- 2.10: Reflectance of some material in various wavelength
2.3.9 Application of Remote Sensing
Application of remote sensing is vast. Now a day, remote sensing has been used
in digital mapping, agriculture, forestry and other earth resources
investigation. Some important application of remote sensing is given as below :
Forestry
Forests are valuable resources providing food, medicine, fuel etc. International
and domestic forestry applications where remote sensing can be utilized include
sustainable development, biodiversity, land
title and tenure, monitoring deforestation, reforestation monitoring and
managing, commercial logging operations, shoreline and watershed protection,
species inventory, forest health and vigor, forest fire/burn mapping, forest
inventory, biophysical monitoring and other environmental concerns.
Land use change
The increase of population and national economies continue to move away from
agriculture-based systems, cities will grow and spread. The change of land use
from rural to urban is monitored to get plan direction of urban developers and
monitor adjacent environmental hazards. The remote sensing methods can be used
to identify the land use change and its impact on environment.
Topography
Remote sensing helps to know the topography of an area. It also helps for
production of topographical map of an area.
Mapping
There is a growing demand for the utilization of remote sensing data in map
production. The benefits are digital format,
low labors intensity, wide area coverage and timely delivery.
Deforestation
Remote sensing plays an important role for identification of deforestation.
Images of earlier years are compared to recent scenes to measure the loss of
forest.
2.4 GEOGRAPHIC INFORMATION SYSTEM
A Geographic Information System is a computer based tool for mapping and
analyzing things that exist and events that happen on earth..
Geographic information system (GIS) is a computer technology that uses
geographic information as an analytic frame work for managing and integrating
data; solving problem and understanding past present or future situation.
Arnoff
(1989) defines GIS as "a computer based
system that provides four sets of capabilities to handle
geo referenced data: data input, data
management (data storage and retrieval), manipulation and analysis, data
output". Automated systems for the capture , storage, retrieval ,analysisand
display of spatial data .(Clarke,1990) A system for capturing ,storing,
checking , interating,manipulating , analyzing and displaying data which are patially
referdnced to the earth.(Chorley,1987).( www.isafa.it/scientifica/gis/eng_gispersito.htm).
In short , GIS are computer – based system that can deal with virtually any
type of information about features that can be
reference geographical location. These systems are capable of handling
both location date and attribute data about
such features. That is, not only GISs do
permit the automated mapping or display of
the locations of features , but also these
systems provide a relational database
capability for recording and analyzing descriptive characteristics
about the features. For example,
a GIS might contain not only a "map" of the
location of roads but also a database of
descriptors about each road. One of the important benefits of a GIS is the
ability to spatially interrelate multiple type of
information stemming from a range of sources. Remote sensing images
and information extracted from images are
used as primary data sources for GIS .
src="new_page_11_files/image022.jpg" v:shapes="_x0000_s1035">
Figure No 2.11: Schemematic
function of GIS process
(Santra, 2001)
GIS may be manually done or computer-aided. A manual GIS involves
creating a base map and one or more layers on
clear film to overlay over the base map. The
combination of layers can, thus, indicate areas affected by different combination
values within the GIS. (Santra, 2001)
First GIS software came in 1970 from the lab of the
ESRI. The development of GIS has occurred with the contribution of many
different disciplines such as Geography, Cartography,
Photogrammetry, Remote Sensing, Surveying,
Geodesy, Civil Engineering, Statistics, Computer Science, Operations Research,
Artificial Intelligence, Demography, and many other branches of Social Sciences,
Natural Sciences, and Engineering. GIS will give you the power to create maps,
integrate information, visualize scenarios, solve complicated problems, present
powerful ideas and develop effective solutions.
2.4.1 Components of GIS
There are five key components of GIS. They are respectively given as below.
ª
Hardware
ª
Software
ª
.Data.
ª
People
ª
Methods.
2.4.2 Three views of
GIS
A map is way to work with geographic data in a GIS . A GIS can be viewed in
three ways.
§
The Data base View
§
The Map Vew
§
The Model View
2.4.3 GIS Tasks
General purpose geographic information system essentially perform six processes
or tasks.
such as:
P
Input
P
Manipulation
P
Management
P
Query and Analysis
P
Overlay –Analysis
P
Visualization
2.4.4 Application of GIS
GIS technology is rapidly becoming a standard tool for mapping, planning,
decision making, and
managing natural resources. Some important application of GIS technology is
given in the following.
Agriculture
GIS provides the analytical capabilities that form the hub of a successful
precision agricultural
system. GIS lets farmers perform site-specific spatial analyses of agronomic
data. A farmer uses GIS
to forecast crop yields and determine fertilizer spread.
Forestry
Forestry uses GIS as a key component in managing its timber resources and
maintaining
sustainable forest management. GIS is
necessary for land valuation, timber market analysis, harvest
route planning, and landscape visualization.
Vegetation
GIS
is ideal for mapping and inventorying vegetation across landscapes and to better
understand
threatened and endangered species inventories for scientific and managerial
applications.
Water
GIS is used for wetland and water quality mapping and planning. It also used to
know about channel
characteristics, seasonal flow, adjacent land uses, and natural features in the
existing habitat.
Planning
GIS is necessary for urban planning and design, mapping, housing,
telecommunication,
underground pipeline, gas source and pipeline management, natural resources
management, power management, landscape, and manage all geographic objects.
Decision making
GIS help to take better decisions about location. Common examples include real
estate site
selection, zoning, planning, conservation, natural resource extraction etc.
Making the correct
decision about a location is increasingly seen as strategic to the success of an
organization.
Geographic Information
GIS provides geographic information management and shearing. Map and other data
help in earth feature observation and study. It makes to get information in an
easy way and help in economic development.
2.5. Preceding study:
Haque ,et al,(2007)
conducted a study to Land use of Sylhet has changed gradually. This is found
from the field survey that in 1970 the area was dominated by marshy land (645.33
katha), vacant land (430.88 katha) and crop land (336.17 katha). By 1988 there
was no university in the area. Residential area also increased. It covered was
39.11 % of total study area. Now in 2007 there is a radical change noticed in
the area in comparison with 1988. Population has increased and accordingly
residential area has also increased. Now it covers about 58.71 % of the study
area. The impacts of Deforestation changes rainfall, temperature, wind speed
etc.
J.B.Alam,et,al,(2005)
conducted a study to present environment auditing of the Sunamganj- Chattak road
via Dowarabajar applying remote sensing technology and checklist method.
According to their study, it was mentioned that during 1990 about 24% of the
total area was as water bodies whereas at 1997 it was increase to about
37%.Again at 1990 the existing vegetation was about 24% ,which during 1997
period decreases to about 11%.About 893.88 hectare areas were changed form water
bodies to exposed soil. There are no likely remarkable changes of settlement in
between 1990 and 1997.
Mathew
(2001) detected that the major change of Pallipad,
Ramankari and
Kumarakom
panchayats is the conversion of paddy fields to non-paddy or
non-agricultural purposes. They used the different data products such as
cadastral maps; aerial photographs and resource maps were acquired. This is
followed by the collection of secondary data from various departments, libraries
and offices. The major change from paddy was
to settlements with mixed trees category coming to about 73.69 percent of the
total paddy change (i.e., from 541.55 ha in 1988 to 608 ha in 1997J.
The area of paddy cultivation changed to coconut comes about 13.24 percent [from
1.25 ha. to 16.89 ha), to mixed crops comes to about 2.66 percent, to plantain
0.31 percent and to the water areas which comes to about 1.03 percent. About
8.93 percent of the change was to marsh. A slight increase in area of pond, and
river is noticed from 3.02 to 3, 54 hectares and 23.21 to 23.55 hectares
respectively. The new categories of land uses evolved mainly through the
conversion of paddy are mixed crops, comprising 2.71 ha, plantain comprising
0,37 ha and marsh comprising 10.27 ha.
YUNUS,A.J.M et al,
(2004)conducted to develop appropriate mapping and assessment techniques to
quantify the nature and magnitude of riparian landscape structural changes along
the Pinang River using remote sending data. Vegetation land-use changes from
1992 to 2000, within fixed 50-m width stream buffer, were identified using GIS
and used to estimate the riparian zone and subsequently calculate the landscape
patterns using Patch Analyst. The riparian land-use patterns in 1992 and 2000
were studied by landscape metrics such as areal percentage, patch number per
unit area, landscape diversity, evenness index, and mean fractal dimension. The
results show that in vegetation areas have significantly decreased mainly due to
conversion to urban and built-up, agricultural, and recreational land.
Furthermore, most of the agricultural land is being displaced to the hill slopes
and hilly area (85% of first-order stream located), while urban and built-up
developments are gradually replacing the original agricultural land. Based on
landscape metrics, it has been revealed that landscape metrics indices are
significant for evaluating the riparian land-use and land cover change, in
addition integration of GIS and remote sensing to quantify
landscape structure is a feasible and efficient way to evaluate the temporal
effect of land-use activities on watersheds
Johnson,
et al,(1999) reported to land derived inputs of nutrient and sediment, there is
concern worldwide for the effects of anthropogenic change in river catchments on
reefs. This case study was undertaken on the floodplain of the Herbert River
catchment in north Queensland, utilizing remote sensing and GIS to assess both
spatial and temporal changes in freshwater wetlands and riparian forests. It is
demonstrated that there has been a very large reduction in the area of these
ecosystems since European settlement in the mid nineteenth century, with an 80%
decline in their extent since 1943. A range of quantitative measures show that
the landscape diversity of these ecosystems has also declined. These changes are
of importance in terms of regional, national and international trends.
It should be worth mentioning that all the existing literature . so far
completed in differcnt areas of Bangladesh . But our project report undertake
an empirical investigation on the Mangrove forest cover change detection in
Chokoria Sundarban using RS &GIS .
