Bangladesh Is Used to Coping But Rising Seas Pose
New Dangers
"The people of Bangladesh have been living with natural hazards
and catastrophe [particularly river and coastal flooding]
for thousands of years," say the authors of this report on sea
level rise, and the Bangladeshi have developed methods of coping
with them. However, the threat of sea level rise because of climate
change is "something new and potentially devastating." The country
will have to develop a more comprehensive view of its coasts and
how to manage them, taking into account global sea level rise,
subsidence, population growth and development. It will need help
from the world community to face this new challenge.
About 115 million people - nearly 800 per square kilometer -
live in the low-lying delta of three major rivers, the Ganges,
Brahmaputra and Meghna. This study of the effects of a one-meter
relative sea level rise predicts that 17.5 percent of
the country will be inundated, displacing 13 million people, about
11 percent of the population. The Sundarbans, the largest mangrove
forest in the world, would probably be destroyed. This unique
habitat for plant and animal species is already threatened by
salt intrusion, partly because the flow of the Ganges in the dry
season was diminished after a dam was constructed to divert water
to Calcutta.
More than one-fifth of the country's monsoon rice land would be
flooded. Coastal aquaculture, particularly shrimp would be overwhelmed,
although it is possible it could displace agriculture or migrate
landward. The facilities of two major ports would have to be upgraded
and raised. Coastal islands, home to many thousands of people
and important areas of biological diversity for both plants and
animals, would be "totally lost." River floods from melting snow
in the Himalayas, which already cause tremendous destruction and
loss of life as well as crop damage, would be higher and last
longer. Diarrheal diseases spread by these floods - a major health
hazard - will only get worse. Salt intrusion of both ground and
surface water, now causing some difficulties, will become more
of a problem.
The devastation of the periodic cyclonic storms arising out of
the Bay of Bengal will grow "many fold," as rising seas increase
the height and penetration of the surges. Erosion would mar the
southeastern beach near Cox's Bazar, one of the longest stretches
in the world and a major tourist attraction.
These acute difficulties will not be easy to solve, and Bangladesh
cannot mitigate them without outside help. The options are limited.
The relocation of people in such a densely populated country is
almost impossible and relocating homes, buildings and roads would
also be a formidable job. Coastal protection would be expensive
and has drawbacks although it is probably the most likely alternative.
The minimum protection for the 16,700 km2 area likely to flooded
in a one-meter rise would cost approximately $50,000 per square
kilometer - close to $1 billion. This would include building nearly
9000 km of new earthwork embankments, raising nearly 5000 of existing
embankments, strengthening and renovating, building sluice gates
and other structures. Even these measures would only protect against
a 20-year flood. Should a higher level of protection be offered?
the authors ask. Flood protection also does have disadvantages.
It stops beneficial delta processes, particularly depositing sediment,
which would keep land elevated as seas rose. The Sundarbans would
not benefit from coastal protection because they need an interplay
between salt and fresh water.
The principal program which is planned at present- a $10 billion
effort - consists of a series of embankments on major rivers.
But sea level rise will increase upstream flooding, upper river
embankments will need to be raised to higher levels, increasing
costs. Costs of embankments for agriculture, ports and other cities
have not been included.
(S.Huq, S.I.Ali, and A.A.Rahman, Bangladesh Centre for Advanced
Studies, Bnagladesh)
