Abstract:
After the devastating flood of 1987 and 1988, Government of
Bangladesh decided to build a protection works around Dhaka City
along with the surrounding rivers. Every development works needs a
feasibility study to assess its impact so that preventive
corrections can be made. But due to the degree of damages in 1987
and 1988, an urgency of need has been arisen and "Greater Dhaka
City Flood Protection Works" (GDCFPW) started' without any
feasibility study. Now, along with many positive impacts, some
negative impacts have been arisen which may offset the project
itself. Hence, impact of GDCFPW on environment has been critically
reviewed with specific reference to domestic waste disposal system.
There are two types of domestic waste, namely liquid waste and
solid waste. Some portion of liquid waste are handled by DWASA
piped sewer line, which has little impact on GDCFPW unless overflow
from manholes occurs due to faulty construction and maintenance
negligence. But, major portion of liquid waste are not taken care
by DWASA. This portion arises mainly from slum areas where proper
sanitary system is not provided. These raw sewage directly mix with
surface wash and eventually finds their ways to canal system.
Moreover, leachate from solid waste deposited along road side also
mix with canal water thereby increasing the pollution load of canal
water to an alarming stage. Prior to construction of GDCFPW, these
surface wash reach to the nearby river from many points. Now, after
the construction of GDCFPW, all runoff route have been cut off.
Subsequently, five lagoons are allowed to form, from which water
will be pumped into the river in wet seasons or will be allowed to
go to the river through sluice gates in dry seasons. The highly
polluted canal water which contains raw sewage, leachate,
industrial waste and agricultural residue will agglomerate into lagoons or other low lying areas. This will create public health
hazard. It will require a day or two for the lagoon water to move
into the river, by this time ground water may pollute. Further,
water is coming to the river through some specific points, which
may reduce the self assimilatory capacity of the river system.
Besides public health, surface and ground water pollution, the
project will hamper fisheries, city drainage and sewerage system,
road and canal traffic. Since the project provides a flood free
zone, rapid in-migration of poor people will be enhanced. This will
make the problems worse.
With proper steps to overcome or minimize problems, GDCFPW may
become a very beneficiary project. It will protect the capital city
of 265 sq. km. from flood water, saving Tk. 250 million per year
and ensuring 4.8 million people a flood free life, Moreover, it
will help city development, road communication improvement and
agricultural activity increasement.
