Oceanography is a branch of science which deals with the study of ocean. It is
the Physical, Chemical, Biological and Geological aspects of the oceans.
The ocean extends from the shallow estuarine areas to the deeper locations of
the ocean. Generally, the division is responsible in applications of space and
satellite based remote sensing technology in coastal, offshore and open sea for
exploration and exploitation of available resources therein.
Our Bay, the marine area of Bangladesh, is characterized by a semi-enclosed tropical basin. The
coastline of the country comprises about 710 km extending from the tip of Teknaf
in the south-east to the south-west coast of Satkhira. An area about 166000 km2 along more than hundreds of off-shore Islands (OSI) of Bay of Bengal (BoB),
Bangladesh have been exists. Natural
resources in this area have been used for multiple purposes and have strongly
influenced socio-economic development.
methods for collecting information about coastal as well as off-shore Island
are relatively costly and time consuming. Remote Sensing (RS) observation with its unique capability
cost-effective support in compiling the latest information about the
environment of the OSI, while Global Navigation Satellite System (GNSS) use to
collect field information for increase the accuracy of RS data and GIS
facilitates uses for multidisciplinary analysis and decision support.
Integrated analysis comes under the economic
jurisdiction of Bangladesh for exploration, exploitation, conservation and
management of its marine resources.
Under Satellite based Coastal Monitoring
System (SCMS) the following recent
past and current research activities are running.
- Monitoring and Mapping of Coastal
Morphological Changes using
RS, GIS and GNSS Technology (Central Coast)
- Bathymetry Mapping using Landsat
- Sea Surface Temperature mapping using TM data
- Ecologically Critical Area
(ECA) Zoning of Sonadia Island, Moheshkhali, Cox’ Bazar
region of our coast begins from the Tebegins from the
Tentulia river to the big Feni river estuary including the mouth of the Meghna river upto the confluence
of the Padma (Ganges-Brahmaputra)
and the Meghna river near Chadpur.
Heavy sediment load and one of the most complex tropical esturian
ecosystems of the world characterize this region. The coastline is most
irregular, and consists of a series of islands, where the rivers are
continuously changing their courses; the funnel shaped apex of the Bay
of Bengal is relatively shallow, surrounded by numerous islands
and estuarine channels- Tetulia-Rabanabad channel, Hatiya channel, and Sandwip
channel. The area is dominated by semi-diurnal tidal currents, the maximum
tidal range of 5 meters
occurs in the Meghna estuary which gradually
decreases southeastwards along the Chittagong
coast. Since the last two hundred years the Meghna
estuary went through intensive morphological changes with migration and the
growth of islands in the southern direction. This region is also subject to the
impact of cyclone and storm surges causing an innumerable loss of life and
property. Figure 1a shows the exposed and
interior coast including study area. Figure 1b shows the study area of
In this study, satellite
data of Landsat MSS (80 m) 1973, Landsat TM (30 m) 1989 and 2010 also tidal data of 1989 and
2010 were used to generate digital data base of different time period, analysis
of plain/tidal land, erosion/accretion and waterways/channel behavior and
finally produce digital map of coastal area. The study reveals that 87254.6 (hector) areas
have been reclaimed in central coast during 1973-2010. To over come the above
study the following activities have been developed.
Ø For land water
separation, Near-Infrared band (0.76 to 0.90 μm)
has been used because band 4 of Landat-TM is
suitable for land and water separation.
In this case digital number (DN) values of water have been collected
carefully from the histogram of the selected images and applied the collected
vales in the developed algorithm.
Ø For erosion and accretion of off-shore Island (OSI), raster base GIS as well as ArcGIS based analysis have been applied for generation of
erosion and accretion map of coastal area as well as OSI of Bangladesh.
Ø For waterways/channel
behavior and tidal flat mapping, multi-temporal data have been analyzed based
on raster base GIS and ArcGIS.
Ø Inventory of the
off-shore islands under different time period and construction of temporal GIS
the generated digital data base of this study will be helpful for better
planning, policy formulation, and decision-making in national development. To
over come the above study the following activities have been developed.
to study the coastal
morphological changes using RS,
GIS and GNSS Technology the following objectives have been pursued
To generate coastal morphological data sets
1973, 1989 and 2010.
To generate morphological changes between
To study the behavior of the process (Erosion
and Accretion) of some selected OSI and River/Channel of the study area for the
above period and generate maps.
of the off-shore islands under different time period and construction of
temporal GIS database.
and Analysis of Central Coast
(A) Analysis the coastal morphological changes
2 shows the GIS analysis of Morphological Changes of Central Coast between 1973-1989-2010
Figure 3 shows the Bar diagram of
Morphological Changes of Central Coast between 1973-1989-2010
clear seen from the figure 4 that total land has been reclaimed 87254 hectare in 2010 with
respect to 1973. During 37 years period total accretion and erosion was 161333 hec and 74079 hec respectively.
Figure 4 shows the Pie-chart of central coast during (1973-2010).
(B) Analysis the behavior of the
process (Erosion and Accretion) of some selected OSI and River/Channel of the
study area for the above period and generate maps (to be continued).
(C) Inventory of the off-shore islands under different
time period and construction of temporal GIS database (to be continued).
Coastal bathymetry is important
for monitoring the emergence of new land, navigational channel maintenance as
well as for fish resources tracking purposes. But coastal bathymetry undergoes
frequent changes due to coastal processes such as erosion and deposition of
soil. As a result, hydrographic charts
in these areas have to be updated frequently. But Hydrographic surveying by
conventional ship borne sounding technique is slow and expensive. Remote
sensing techniques can be used with limited ground observation to study and
monitoring these changes. The unique character of the shorter weave length
visible channel, such as blue (0.45-0.52µm) has the ability to penetrate water
to a significant depth and generates radiance that reflects submarine albedo. In this study, an attempt has been made to prepare
a digital map showing the distribution of bathymetry using Landsat-TM
data over coastal area (figure 1) of Bangladesh. Three simple algorithm of (i) land water delineation based on blue band, (ii) pixel
intensities (Xi) and (iii) water depth (Z) were used for
bathymetry mapping. The result depicted that the average water depth
recorded in this image was in between 1 to 12.5 meter depth. The depth of sea-bed varies with locations.
The mouth of Haringhata river
is shallower than the Shahbazpur channel because of
the contribution of soil. In addition, the natural shape of the selected area
supported the opportunity of deposition process and erosion. Thus, the lower
water depth measurement was estimated from the satellite image. Figure 2 shows
the bathymetry mapping over study area. The
result was compared with theoretically idea of water depth of the location
since the absent of ground measurement data.
Sea Surface Temperature (SST) is
important for climate modeling, study of the earth's heat balance, atmospheric
and oceanic circulation patterns and anomalies (such as El Niño/La Niña) in
global scale. It is also important for tropical cyclogenesis.
In local scale it is used as an indicator of the environment required for the
living of some marine biota. Conventional techniques of obtaining SST is time
consuming and expensive. The satellite remote sensing techniques found very
useful. A number of studies have been performed on bathymetry and SST
mapping using TM, AVHRR and MODIS data but most of the studies have been
conducted outside of Bangladesh. In this study, an attempt has
been made to prepare a digital map showing the distribution of SST using Landsat-TM data over coastal area (same of bathymetry study
area) of Bangladesh. The radiance and effective
temperature based on Markham et.
al. (1986) was used to estimate the actual temperature (T). The
distribution of SST varies of location. Higher the surface temperature at the
location near the shoreline compared to location farther. Distribution of
higher temperature contributed by suspended sediment and residential area.
Figure 3 shows the SST distribution over study area. The result was compared
with theoretically idea of the typical SST and water depth of the since the
absent of ground measurement data.