Chapter Two: Background
1. Background of study area
Physical settings & Urban growth
Dhaka, the capital of Bangladesh, one of the largely dense megacities of the world, has faced numerous dramatic historical changes in terms of politics, demographic and topographic structure over 400 years (Chowdhury 2013; Kabir & Parolin, 2012). Located in central of Bangladesh and on the eastern banks of the Buriganga River, the city lies on the lower reaches of the Ganges Delta. Tropical vegetation and moist soils characterize the land as flat and close to sea level. This makes Dhaka susceptible to flooding during the monsoon seasons owing to heavy rainfall and cyclones. The growth of the city has been dictated by natural forces, rather than by any inclusive planning. Based on available literature and documents, the growth and changing pattern of Dhaka can be divided into the following five different phases as depicted in Figure (Chowdhury & Faruqui 2009; Dhaka Tribune,2017):
• Phase 1: Pre-Mughal period (before 1608);
• Phase 2: Mughal Period (1608-1764);
• Phase 3: British Period (1764-1947);
• Phase 4: Pakistan Period (1947-1971); and• Phase 5: Bangladesh Period (1971-onwards)
Dhaka is expanding apace, at an average rate of 4.24%/year and is projected to be the third largest megacity in the world by the year 2020 (The World Bank, 2007). In last two decades (1990-2010), built-up area has increased near 67%. A mass alarming reduction (i.e. 59%) in vegetation and cultivated land is observed where landfill for infrastructural development resulted in decrease of water body and wetlands (i.e. 53%) with the increase in bare soil/landfill (i.e. 44%) (Mamun et al., 2013).
Due to capital base centralization of Bangladesh, Dhaka has always been the center of growth since independence. Lack of proper planning with haphazard urbanization and industrialization makes it over populated with huge migration each year; consequently turned polluted and ecologically imbalanced. The following graphics and chart provided by Hassan & Southworth (2017) represent the drastic rate of Land Cover Change and Urban Growth Trajectories of Dhaka city.
Figure . Spatiotemporal distribution of land covers and patterns of urbanization in greater Dhaka from 1972 to 2015: (A) 2015; (B) 2010; (C) 2005; (D) 2000; (E) 1995; (F) 1990; (G) 1980; (H) 1972.
Figure. Land cover map of the Core city/Dhaka City Corporation area (DCC) between 1972 and 2015. (A) 2015; (B) 2010; (C) 2005; (D) 2000; (E) 1995; (F) 1990; (G) 1980; (H) 1972.
The climate of Dhaka can be categorized as Aw or tropical wet and dry according to the Koppen–Geiger climate classification and characterized by three distinct seasons (Mourshed 2011):
• A hot summer season from March to June with high temperatures between 28 and 34°C, a high rate of evaporation and erratic heavy rainfall;
• A hot and humid monsoon season from June to October with torrential rainfall, accounting for about two thirds of the annual rainfall; and
• A cooler and drier winter season from November to March with temperatures between 10 and 21°C and little rainfall.
Five major river systems (the Buriganga, the Turag, the Balu, the Shitalakkhya, and the Dhaleshwari) flow across the megacity. Topographically, the area is flat with a surface elevation ranging from 1 to 14 meters above the mean sea level, with most urban areas situated at elevations that range from 6 to 8 meters (FAP 8A,1991). Dhaka and its neighboring areas are low-lying and possess low proportion of highland that is free from inundations during annual floods. Again, the low-lying swamps and marshes situated in and around the city because of peripheral rivers, are somehow considered to be significant barriers to the physical expansion of the city till now.
Socio-economic condition & demography
Dhaka and the municipalities that make up the Greater Dhaka Area have a total population of over 18.2 million (http://worldpopulationreview.com/, 2018), and the city has shown population growth of about 4.4% annually (Dhaka Structure Plan, 2016-2035). The projection by UN states, Dhaka’s population will be around 22.9 million at 2025. Even though Dhaka represents only 1% of the country’s total area, it contributes over 36% to the GDP and creates 44% of the country’s total employment (UN World Urbanization Prospects, 2012). With a density of 44,500 people per sq. km Dhaka is the densest city on earth (https://www.thedailystar.net/, 2018).
Land ; Buildings
Dhaka is noted for a severe shortage in land and housing facilities. Dhaka would need about 4.45 million housing units over a 17-year period from 2008 to 2025 in order to fill projected demand.
Because of the scarcity of land for development in the city, the price of land is increasing at a very rapid rate and the common people are not capable of purchasing land and building homes in Dhaka. A survey conducted by the Consumers Association of Bangladesh (CAB) in 2007 states housing rent in Dhaka city had risen by 250% in the last 17 years, despite the presence of rent control laws and courts. Recent survey found that there are 326,000 buildings in Dhaka megacity.
The representatives of the Comprehensive Disaster Management Program (CDMP), under the Ministry of Food and Disaster Management of Bangladesh, specified that 78,000 out 326,000 buildings in Dhaka are vulnerable to collapse, which also shows that official building codes have not been followed properly. The assessment also identified the vulnerability factors in Dhaka,the presence of soft story in buildings (53 %), heavy overhangs in buildings (41 % in Dhaka), and short column in buildings (34 % in Dhaka) (Prashar ; Rahman,2017). Violation of Building Code is the common practice in Dhaka. It is estimated that around 90% of Dhaka’s pre-FAR buildings, in one way or another, are constructed in violation of statutory codes (Mahmud, 2007).