Impact of greater dhaka city flood protection works on the environment with specific referemce to domestic waste disposal.

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.