The much talked-about Detailed Area Plan of Dhaka Mega City would have to include existing low-lying wetlands, as well as revival of the pre-urban wetlands, in order to lay the groundwork for a truly sustainable future for the capital.
'Urgent attention is needed for wetland preservation, and reviving them for Dhaka city to remain liveable,' said Mohammed Ataur Rahman, director of the Centre for Global Environmental Culture Programme on Education at the International University of Business Agriculture and Technology.
According to Rahman, revival of wetlands would restore and rehabilitate the flora and fauna of the capital, mitigate the acute water crisis faced by city-dwellers, recharge groundwater and revive the wetland ecosystem.
'With the revival of wetlands, the city will be free from water stagnancy and flooding, while also facilitating the communication system — both waterways and road transportation.' He noted that the Ramsar Convention has defined wetlands as areas of marsh, fen, peat land or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt.
The definition includes areas of marine water of which the depth, at low tide, does not exceed six meters.
Rahman said Dhaka, with an aerial extent of 298 square kilometre is bounded by the River Buriganga in the south, the River Balu in the east, the Tongi Khal in the north and the River Turag in the west.
These rivers are connected to the Ganges-Brahmaputra River system and also includes the regional Old Brahmaputra River as it flows southeast.
The bigger area is closely dissected by a number of rivers and canals, which are hydro-logically connected to these major rivers, he added. The IUBAT professor said the wetland quotient of Dhaka's total area had been squeezed to just 5 per cent, resulting in acute shortage of surface water supply. Meanwhile, pollution has become a great threat to the aquatic ecosystem.
He mentioned how compared to an aerial photo taken in 1968, inland water bodies have reduced drastically in a similar photo dated 2001. The Gulshan, Dhanmondi, and Ramna lakes are highly prominent in the 1968 photo.
Rahman noted that the total areas of inland water body were measured to be 5.1 square kilometres in 1968. The 2001 satellite image shows that the area covered by lakes, especially the Gulshan and Dhanmondi ones, have shrunk dramatically.
'Some khals and channels are not identifiable or missing in the south-western Mohammadpur and southern Motijheel area of the city and the total area in 2001 is measured to be just 1.8 square kilometres,' revealed Rahman.
It is seen that water bodies have become more sporadic and patchy in 2001 in comparison to 1968 in many parts of the city. Water body compartmentalisation has particularly occurred in the north-central, southeast and western parts of the city.
Rahman said canals, wetlands and depressions had been filled up due to rapid urbanisation, both in and around the built-up city area. Unfortunately, the spread of unplanned urbanisation has been destroying the water-bodies and flow-paths, causing rainfall-flooding and drainage congestion in many locations around the city. Filling activities, embankments and roads are compartmentalising the wetlands and water bodies, hence obstructing the natural drainage.
Rahman insists progressive, unplanned urbanisation is at the root of wetlands and other water bodies in Dhaka city dwindling over the decades. A number of studies have shown the relationship between land filling activities and drainage congestion and water-logging. At the moment, the city gets water-logged to the point of severely disrupting normal life of inhabitants, particularly during the wet-season.
But the scenario can be expected to worsen with time, warns Rahman, as rainfall patterns get more and more erratic, and more intense, with increasing frequency due to the effects of climate change.
Plants and soils in wetlands play a significant role in purifying water, removing high levels of nitrogen and phosphorus, and in some cases, removing toxic chemicals through biogeochemical cycling and storage, he said. This makes it all the more important to preserve them.
Source: New Age
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