Save flood vulnerable eastern fringe of Dhaka
United Nations warned that a quarter of Bangladesh coastline could be inundated and about 17% of its land mass would go under water, if the sea rises 3 feet in the next 50 years. Approximately 30 million people will be displaced from their homes, making them 'climate refugees'. A recent World Bank report lists Bangladesh as one of the 12 countries most at risk for climate-related problems. Though Bangladesh's contribution to global green house gas emissions is one of the lowest in the world, its low topography, disadvantageous geographic location, high density of population etc make it more vulnerable to climate change.
According to researchers, climate change poses risks to Dhaka city in two ways: one is flooding and the other is heat wave. Besides flooding, the key climate driven variability is erratic and prolonged rainfall with the increase in precipitation and river flow changes caused by sea level change.
Dhaka is situated in the central area of the flat deltaic plain of the three large rivers, the Ganges, the Brahmaputra and the Meghna. Dhaka falls under the active river tidal zone. The low-lying areas are often engulfed by the high tide influenced by the sea tide. Flooding has become a regular event in Dhaka not only by the overflow of rivers but also through water clogging.
The low-lying area of Dhaka city, which is mainly the Eastern part, is at high risk. It forms some two thirds of the greater Dhaka drainage basin. Eastern fringe is defined as flood flow zone for the drainage, navigation or retention of urban runoff in the structural plan proposed for 1995 to 2015. Basically the low lands and the water bodies act as the water retention areas, which help sustain the natural ecosystem as well. Traditionally, the water retention areas of Dhaka city have been efficiently storing the excess water caused by excessive rainfall and the canals connected to the rivers gradually draining the water to the rivers. As a result, there was no water clogging. But the scenario is changing.
The population of Dhaka is increasing alarmingly and there is land scarcity. It is leading towards the encroachment of these water retention areas, which mostly lie in the eastern part of Dhaka city. The city drainage system has also not improved with the pace of rapid growth of urbanization, while most of the canals out of around 50 in the city have either been filled up entirely or partially over the last two decades. Consequently, these low-lying areas suffer from inundation.
The eastern area of Dhaka city is the most vulnerable part and susceptible to annual flooding. According to available literature, the eastern part (nearly 119 square kilometers) of Dhaka was 100% inundated in the floods that occurred in 1988, 1998 and 2004 and it was inundated for the longest period of time than the other parts of the city. It is not only affected by the external flood, which is caused by the rise of river water level, but also by the internal flood caused by the storm water and lack of drainage.
Under the Dhaka Integrated Flood Protection Project, the western part was protected by embankments and the drainage system. But during the 1998 flood, even some of the protected areas were inundated; this indicates that the existing adaptive measures needed further to be improved. The eastern part of Dhaka city is still unprotected. This increases the urgency of the need to take adaptive measures against current climate variability and impact of future climate change to protect the eastern fringe of Dhaka. There is also need for assessing different adaptation measures to be undertaken in the Eastern fringe of Dhaka city.
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