Effects of land use change on drainage and retention ponds in the western part of Dhaka city

Abstract

Urban flooding in Dhaka city is a common phenomenon which reflects the poor management & development planning regarding wet land preservation. Dhaka has experienced major floods in 1954, 1955, 1970, 1974, 1980, 1987, 1988, 1998 and 2004. About 77% areas of Dhaka City were submerged and about 60% of the city dwellers ware directly affected by the terrible flood of 1988. Several studies carried out in 1988- 89 to develop a comprehensive flood policy and Program for Bangladesh, including Dhaka City. Based on the study results, Flood Action Plan (FAP) was formulated. In support of Government’s flood action program, Dhaka Town Protection component, FAP-8 was formulated which consist of two parts FAP-8A & FAP-8B. FAP-8B is covered with 136.5 sq. km of western part and FAP-8B. FAP-8A is covered with 128.5 sq. km of eastern part of Dhaka City. This research has encompassed mainly the western part of Dhaka City. This study has attempted to explore the land use changes and also the cause and effects of land use changes on FAP-8B proposal in the western part. Land use changes have been analyzed through Satellite Image Interpretation and physical feature data analysis. The study area is the main built-up area of the Dhaka City. Major land use in the western part is residential about 51% and it consists of 73.6 % population of DCC area. Most of the study areas are affected by water logging and flood. Unplanned physical intervention of the natural drainage system is the main reasons for flooding. The socio economic condition and development pattern or trend of the infrastructure development pattern has imposed significant impact on the land use changes. During 1989 to 2007, wetland areas have been decreased nearly 22% to 12%. From the year 1989, on an average 2.5% wetlands have been decreased. FAP-8B proposed about 4.5% area of total land for retention pond in the western part but now exist only 1.79%. About 6.71% of the Kallayanpur retention ponds areas are now using as water body. Out of 14 khals, 13 khals within the western part are encroached significantly and the encroachment is about 34% of its total area. The result reveals the rapid rate of wet land degradation and unplanned infrastructure development.