THOUGHTS ON MITIGATING THE HARMFUL AFFECTS OF DISASTERS, ENDANGERING
THE SOUTH-WESTERN REGION OF BANGLADESH
INTRODUCTION :
The universe and the Solar family behaves in ways most of which are
still unknown to the scientists. At times we face altogether new
phenomenon. Whenever any such new development or deviation proves
harmful we became frightened. In the recent decades, two such
phenomena have endangered the lives and properties of people of the
South-Western region of Bangladesh. These are : (i) Cyclonic storm,
(ii) Tidal bore (due to cyclone or Tsunami) and (ii) Sea level rise.
In pursuance with the theme of this Seminar I shall keep my discussion
limited on various aspects of these two phenomena and their probable
mitigations only.
MAJOR AIR-WATER RELATED DISASTERS IN BANGLADESH :
The major climatic and geotectonic hazards the people of South-Western
region of Bangladesh suffer from are : (01) Cyclone, (02) Flood and
(03) Tidal bore due to cyclone. The two new additions in this list are
: Tidal bore due to Tsunami and Sea-level rise.
(01) Cyclone : A map showing the paths of major cyclones traversing
the territory of Bangladesh shows that most of those passed through
the South Western region.
(02) Flood : The map of natural flood zones (flood plains) of
Bangladesh shows that the South-West zone is unaffected by flood.
However, they would have never-ending flood with the rise of sea water
level.
(03) Tidal Bore : The areas of the South Western region adjacent to
the sea is prone to Tidal Bore.
(04) Sea-level rise : This is a comparatively new phenomenon. The land
of Bangladesh regions adjacent to the sea has got a natural slope
towards the sea. Hence these areas are to be permanently immerged due
to sea-level rise.
From the above figures it may be seen that the worst affected area due
to (i) Cyclone originating in the Bay of Bengal, (ii) Tidal bore and
(iii) Sea-level rise is the South-Western region of the country.
GLOBAL WARMING / DIMMING AND SEA-LEVEL RISE :
Since Global warming is a recently developed phenomenon and the common
people do not seem to have the clear understanding of it, we present
here its brief discussion. Meaning of some the technical terms used in
this paper has been provided at the end. We shall endeavor to answer
the question : Whether sea-level rise would at all take place.
(a) GLOBAL WARMING : The temperature of the atmosphere in between the
earth's surface and a 'modified layer of gas' is getting hotter
because of trapping of heat energy emitted by the sun, dissipated by
the earth and those created due to human activities. The modified
layer of gas is constituted of Ammonia, Hydrogen Sulfide, Oxides of
Sulfur and Nitrogen, Oxides and other pollutants produced by
industrial plants and motor vehicles, Ozone, atmospheric Carbon
Di-Oxide, Methane, Chloro-Fluoro Carbon (CFC) etc. These are commonly
known as green-house gas. Due to this rise of temperature, water
existing in the form of in the Polar Regions, ice-berg, ice at the
peak of mountains, glaciers etc. constantly melt down, causing water
level in the sea to increase.
(b) GLOBAL DIMMING : Tons of minute solid particles from the
industries, cities, vehicles, jet planes (known as Con-tail affect)
etc. escape upward. When these come in contact with cloud the steam
sticks to water vapor and render the cloud impenetrable to Sunray. As
such sun's radiation cannot reach the earth. It creates less light or
'dimming' and cooler environment. However, the thick layer of cloud
reduces evaporation, because the sun's ray cannot come in contact with
water below. As a consequence there happens less evaporation and less
rain. This phenomenon causes more water to stay in the sea. From these
two phenomena one can easily understand why it is natural for the
sea-water to rise up due to Global warming and Global Dimming.
WHO ARE TO BE BLAMED ?
At present lots of hue and cry is going on accusing the developed
countries holding responsible for production of green-house
components. However, this endeavor is surely going to fail because of
genuine reasons. We mention here some of the reasons.
(01) While the developed countries emit vast quantity of green-house
gas (Hydrogen Sulfide, Oxides of Sulfur, Oxides of Nitrogen, Carbon
Di-Oxide, Chloro-Fluoro Carbon (CFC), Smoke, Carbon Mono-Oxide, dust
particles etc.) from vehicles, domestic activities, Industries etc.,
the non-developed and the developing countries also do the same by
producing gases like Carbon Di-Oxide, Methane, Smoke, Carbon
Mono-Oxide, Oxide, dust particles etc. in their water-logged rice
fields, bogs and grass-eating cattle. If the developed countries
create pressure on the developed countries to stop use of vehicles or
industries, the developed countries also deserve the right to
pressurize the developing countries to stop agriculture and
cattle-raising.
(02) Everyday millions of tons of green grass are emptied by the
rivers in the sea. Also sea-weeds grown in the sea finally deposit on
the bottom. These produce huge quantity of Methane, which are released
in the nature. Who can stop the sea from doing that ?
(03) Considerable quantity of heat energy and gas escape through the
numerous volcanoes and under-water creeks. Is there any practical way
to stop those ?
In such a situation, accusing one country by another or claiming
compensation for this act is an erroneous practice. We can finally
deduce that there is no practical way (01) to stop emission of
green-house gas from various sources and hence no way to stop the rise
of sea water and (02) to stop cyclonic storm, which is formed due to
water heated by the gas escaping out of under-water volcanoes and
cracks.
MEASURES TAKEN AGAINST FLOOD, CYCLONE AND TIDAL BORE :
The various measures taken by the government and other various
organizations for addressing the situation created by Cyclone and
Tidal bore have got both advantages and limitations. We shall mention
some of these measures.
(I). BOAT : Some NGO's have proposed for maintaining one boat per
family. They proposed for digging a pond next to the habitable house
such that the inhabitants can save life and properties during flood.
(II). BRICK BUILDING FOR PUBLIC USE : Brick-built houses accommodating
school, hospital, government office etc. in the cyclone prone areas
are used as cyclone shelters.
(III). BRICK BUILDING ON STILTS : Brick buildings built on stilt have
been constructed at some locations to act as shelter during flood,
tidal bore and cyclone.
(IV). EARTH MOUND (KILLA) : High earth mound constructed at some
locations in the coastal area save human life and cattle in time of
flood and tidal bore.
(V). EMBANKMENT : In some regions closed embankments have been used to
prevent flood water from damaging crop and other properties. Even
though this venture tried in Bangladesh has been proved futile because
of water-logging, the same has been found to work successfully in the
Sundarban area of West Bengal since 1965.
COMPARATIVE PICTURE OF VARIOUS MEASURES TAKEN AGAINST FLOOD, CYCLONE
AND TIDAL BORE
MEASURES ADVANTAGES LIMITATIONS
01. LIFE-SAVING MEASURE IN FLOOD/TIDAL BORE : Boat ready for floating.
Capable of saving (01) life and (02) meager properties during flood.
Dangerous during cyclone. No room for cattle, no safety for crop.
02. CYCLONE SHELTER
Brick building for public use (school, office, community
centre etc.). Capable of saving (01) life and (02) some properties
during cyclonic storm. Needy people may suffer due to location, space
and accessibility to such buildings. No room for cattle, no safety for
crop.
03. SHELTER FOR CYCLONE AND TIDAL BORE : Brick building on stilts
Capable of saving (01) life and (02) some properties during cyclone,
flood and tidal bore. Needy people may suffer due to location, space
and accessibility to such buildings. No room for cattle, no safety for
crop.
04. SAFE PLACE AT TIDAL BORE : Earth mound (Killa)
Capable of saving (01) human life, (02) some properties and (03)
cattle during flood and tidal bore. Needy people may suffer due to
location, space and accessibility to mounds. No safety for crop.
05. NULLIFYING FLOOD AND TIDAL BORE : Poldering or enclosed
embankment Capable of saving human (01) life, (02) properties, (03)
cattle and (04) crop during flood, tidal bore and sea-level
rise. Everything like life, properties, cattle and properties are safe
if the structures are strong.
FORMULATION OF PROPOSAL :
CONSIDERING THE PAST ENDEAVORS : Before going for formulation of
proposal for solution, we present here brief discussion on some of the
practiced solutions.
01. BOAT : The boat solution bears the typical character of NGO
practice, where "spending money for the needy" is the inner
philosophy.
02. BRICK BUILDING : Using brick-built public buildings may be an
excellent solution during cyclone. If these buildings can be
constructed with multiple stories, then these may be of use during
tidal bore also. Planning necessarily means achieving success with
limited resources. At present the government follows a policy of
constructing the same type of public building in all regions of the
country, without the considering whether that type is necessary or
not. Fig. No. 01 indicates that no region other than the south-western
region of Bangladesh is prone to severe cyclone. In such a case, if
the government decides to construct less costly and less strong
buildings in the Northern region and take up a policy of constructing
storied brick buildings in the South-Western region, then much better
result may be achieved at less cost.
03. BUILDING ON STILT : Brick building on stilts is an excellent
solution in flood and storm, even though it cannot ensure safety of
the inhabitants properties including cattle and the crop. Also this
type of building is costly and huge number of those may be necessary
to take care of all the inhabitants.
04. EARTH MOUND : With the additional capability of saving the cattle
the Earth mound solution also has many limitations.
05. EMBANKMENT : We shall discuss hereunder both positive and negative
aspects of embankment as experienced in various countries.
(i) East Pakistan/Bangladesh : The embankment solution was practiced
by the government of East Pakistan in the southern region for two
purpose : (i) For enclosing the entire land of independent island and
(ii) To stop entry of saline eater in high tide. However, both the
solutions have been proved futile. As for example, the entire land of
Bhola (independent island) was enclosed by embankment in the sixties.
In 1970, the land faced catastrophe when the embankment failed due to
rat-hole and/or depressed height. The entire crop was rotten (usually
crop is not badly affected by flood continuing for few hours or days)
and the total casualties was estimated to have been over one million.
In Khulna such embankment has created water-logging in huge areas.
(ii) USA : The embankment project (they use the term : enforcing the
natural levee) failed in Louisiana, USA in 2004 due to Katrina.
(iii) West Bengal, India : The Government of West Bengal transformed a
part of the Sundarbans to habitable area in the sixties by
constructing embankment. Inside the enclosed area the land at highest
level was used for habitation, that at slightly lower level for
growing a single crop (paddy) and the low land for fish culture. Till
today we did not hear of any major problem to take place in that
region.
From the above discussion it may seem that (01) Construction of
embankment around and (02) Construction of structures with
cyclone-resistant materials might be the ideal solution to solve the
problem of the South-Western region :
Construction of embankments have lots of disadvantages like
water-logging, stoppage of natural silting, need for huge quantity of
fertilizer, raising of land etc. From the experience that the
embankment program is running successfully in West Bengal (India) one
may feel tempted to accept this solution in Bangladesh. However, a
careful look at Fig. 01 may reveal that the cyclone generating in the
Bay of Bengal moves in a North-easterly direction due to Coriolis
force and the Sundarbans of West Bengal is located outside the path of
severe cyclones (Ref. Fig. 06). The construction of the structures
with cyclone-resistant materials however, is an encouraging proposal.
As a matter of fact two-storied brick buildings owned by the
inhabitants are capable of saving their life and properties.
OTHER CONSIDERATIONS : The earth is losing huge quantity of land every
year due to (i) Rise of sea-water, (ii) Soil erosion and (iii)
Perma-froze affect. On the other hand the population is on increase.
In such a situation all endeavors to increase land should be
considered as blessings. Netherlands has increased its territory by
reclaiming huge land from the sea. Bangladesh is in an excellent
position to reclaim the shallow land at the continental shelf. While
Netherlands was in need of pumping out water after the construction of
the embankment, Bangladesh is extremely fortunate that such operation
would not at be required here. What the country needs is to create
some sort of obstruction near edge of the shelf, such that the huge
quantity of silt cannot escape to the deep sea (i.e. continental
slope). After such obstructions can be created, the job of filling and
creation of natural levee would be done automatically by the receding
silt. I discovered one estimate saying, the country gets 400 Billion
tons of silt every year. While I do not believe in such estimates and
I know how difficult such a job is, from common sense we can sense the
huge quantity of silt escaping every moment.
The job of trapping silt in the continental shelf may be, a
technically speaking a difficult job and economically speaking, an
ambitious program for Bangladesh. However, the value of the reclaimed
land will be so attractive that there may not be any dearth of
commercial firms to undertake this job. If the land at the continental
shelf be reclaimed that the country would no more have to worry for
sea-level rise, cyclone or tidal bore.
SPECIFIC PROPOSALS :
It may take longer time for Bangladesh country to take up the program
of reclaiming land at the continental shelf. By this time there would
be more tidal bores and more loss of life and properties. In such a
situation we present the following specific proposals for mitigating
the problems.
(a) Administrative measures :
(01) The small fishing boats (commonly known as fishing trawler)
should not be allowed to go for fishing beyond certain limit (say, 20
kilometers) beyond the coast line.
(02) The owners of the fishing boats should be asked to submit the
list of workers along with their photographs, consent letter, details
of compensation to be paid in case of mishap etc. before those are
allowed to go to the sea.
(03) Large fishing boats, which are safe in the deep and rough sea
should be used for fishing beyond this limit.
Such administrative measures are capable of lessening the loss of
valuable lives from the South-West and other regions.
(b) Infra-structural facilities for the inhabitants :
The government may establish small size brick-burning kilns at
suitable locations, supply brick making mould and train the people for
making bricks. The inhabitants most of whom are illiterate and are
capable of giving idle labor only can make and dry bricks. Then, they
can take those to the burning kilns where they can pay the cost of
burning by surrendering certain percent of burnt bricks. The soil of
this area with its rich organic content is highly suitable for making
bricks. After the inhabitants can procure enough of brick, they can
sell part of those to procure other materials and go for construction
of buildings. In this way, the unutilized idle labor of the
inhabitants and the easily available soil of this area may turn to
'wealth' for them and also for the country, only if the government can
provide the burning facilities. While such a project may enable the
inhabitants to become owners of better-quality houses, it may also
create alternate means of livelihood, and thus lessen the inhabitants'
dependence on the forest (Sundarban's) and the hazardous sea.
CONCLUSION :
Bangladesh needs to look for permanent solution for the safety of her
people in the South-western region. The country has got and still
receiving vast quantity of resources to counter the ill-effects of
SIDR 2007. While part of this wealth may be used for immediate relief,
the greater part should be saved for long-lasting solution.
Continuation of relief program for a long time may turn the people
dependent on external help. If part of the fund is used for
establishing and maintaining brick-burning facilities, then it would
help the inhabitants to partially solve two of their problems : (i)
Housing and (ii) Livelihood.
At the end I am to add, I strongly feel that Bangladesh should
seriously think of reclamation of land at the continental shelf.
It hears nice to pronounce with gloomy face, "we are sorry for your
loss". And for the affluent people it may be amusing to give
donations to the victims. Only the families losing their sole earning
member, or a family losing its dear son and daughter can feel, how
pathetic it is to live with the cyclone, tidal bore and to witness the
ever-rising water engulfing all they could earn in their lives. The
scientists or affluent people of Bangladesh may have limited
responsibilities. But the responsibility of the government of the
republic is stupendous. Being the representative of the people and
thus shouldering the task of their welfare and safety, they need to
act very intelligently and cautiously in such an extremely grave
situation. Even though we did not notice such intentions in our
government in the past, we hope the present will be different, such
that the future will be better and brighter.
--------------------------------------------
TERMS USED IN THIS PAPER :
CYCLONE : Cyclone or Lows is the term used to denote fast-moving wind
towards an area of low atmospheric pressure. Normally it moves in a
counterclockwise direction in the northern hemisphere and reverse, in
the southern.
ANTICYCLONE : High-pressure area with clockwise winds is known as an
anticyclone or Highs.
HURRICANE : Hurricane is the name given to violent storms originating
in the Atlantic Ocean, Caribbean Sea, Gulf of Mexico, or North Pacific
Ocean east of the International Date Line. Those taking on the west of
the International Date Line are called typhoons.
Tropical cyclones, Hurricanes or Typhoons are caused due to heat
(usually over 27 C, 80 F) from the water, where heat is caused by the
sun ray or under-eater volcanoes.
TORNADO : Violently rotating column of air extending from ground to
thundercloud level with an average diameter of about 50 m (160 ft) is
known as Tornado.
TSUNAMI : A Tsunami is a series of vast waves with 100 to 200 km
widths (the distance between one wave crest to the next), that may
travel hundreds of kilometers across the ocean with velocity of 725 to
800 km/h. It may be insignificant (say, only about half a meter high)
in deep sea, that grow in height as it enters shallow coastal waters.
Tsunamis are usually caused due to displacement or rupture of the
earth's tectonic plates.
FLOOD : Flood is caused by superfluous water, which may happen due to
excessive rain or inefficient drainage. Periodic or natural floods may
occur seasonally in the depressed areas or flood plain. Flood caused
by water suddenly by a number of river system is called a flash flood.
GLOBAL WARMING : It is the phenomenon of warming the atmosphere in the
annular space in between the earth's surface and the modified layer of
gas, where the heat emitted by the earth is trapped.
GLOBAL DIMMING : It is the phenomenon of dimming of the earth below
the cloud, darkened due to carbon particles, that result in less
evaporation of sea water.
GREENHOUSE GAS : Water-vapor, Ammonia, Hydrogen Sulfide, Oxides of
Sulfur and Nitrogen, Oxides and other pollutants produced by
industrial plants and motor vehicles, Ozone, atmospheric Carbon
Di-Oxide, Methane, Chloro-Fluoro Carbon (CFC) etc. are known as green
house gas.
SOURCES OF GREEN HOUSE GAS : The major sources green house gases are
the following :
(i) Industries : Hydrogen Sulfide, Oxides of Sulfur, Oxides of
Nitrogen, Carbon Di-Oxide, Methane, Chloro-Fluoro Carbon (CFC), Smoke.
(ii) Vehicles, airplanes : Carbon Mono-Oxide, Carbon Di-Oxide, dust particles.
(iii) Water logged rice fields, bogs etc. : Ammonia, Methane.
(iv) Domestic cattle : Methane.
(v) Sea bed : Methane (generated from Sea weeds deposited on the bottom).
(vi) Nature : Water-vapor, Ozone.
CONTAIL AFFECT : The lowering of temperature and sunlight by the black
layer of smoke released by the airplanes is known as con-tail affect.
It lowers temperature and helps to decrease evaporation.
PERMA-FROZE : The water in the land in the cold regions get
permanently frozen and act as solid land. Due to global warming, this
soil releases water and the land vanishes into water body. This is
known as Perma-froze affect.
CORIOLIS FORCE : The slippage of the air cover over the earth's
surface at the time of earth's rotation is known as Coriolis force
(Ref : A TEXT BOOK OF CLIMATE AND DESIGN FOR THE BUILT-FORM DESIGNERS.
Bijon B. Sarma and Falguni Mallick. ISBN 984-8684-02-6. P.29).
CONTINENTAL SHELF OR TERRACE : It is the part of the sea floor
adjoining a landmass over which the maximum depth of sea water is
200m. Bangladesh has got a coastal line of over 720-km length. Its
continental shelves extends to 100 km south of Hiron Point and over
250 km off the coast of Cox's Bazar. As for depth, the part of
continental terrace near Chittagong and Teknaf is less than 20m deep.
That on the south of the Sundarbans, Patuakhali and Noakhali is even
shallower. Some of the shoals and sand ridges present on the shelf
show an elongation pattern pointed towards the Swatch of No Ground.
This indicates that sediments are being tunnelled to the deeper part
of the Bay of Bengal through the Swatch of No Ground.
SWATCH-OF-NO-GROUND : The Swatch-of-No-Ground is a trough-shaped
marine valley or canyon that crosses the continental shelf diagonally.
It is situated on the south of the Ganges-Brahmaputra delta at a
distance of about 35 km from the Sundarban of Bangladesh and has a
maximum depth of 1200m, with depths at its edge ranging between 60-800
m.
The Swatch of no Ground has a seaward continuation for almost 2,000 km
down the Bay of Bengal. The sandbars and ridges near the mouth of the
Ganga-Brahmaputra delta pointing toward the Swatch of no Ground
indicate that sediment are tunnelled through this trough into the
deeper part of the Bay of Bengal. Most of the sediment has been
derived from the confluent of Ganges and Brahmaputra rivers, which is
in a position to drain the south and north slopes of the Himalayan,
respectively. Under the present condition perhaps low-density
turbidity currents and sand cascading are dominating process of
sediment transport from the shelf to the deep sea through the Swatch
of no Ground.
PROF. BIJON B. SARMA, ARCHITECTURE DISCIPLINE, KHULNA UNIVERSITY, BANGLADESH
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