Each city flooding brings an assurance

The sufferings are the honestly paid price for the benefits of development. The comparable best example is the impact of climate change resulting from emission of gases from industrial development.

City flooding is not an uncommon phenomenon across the world. Many famous cities of the developed countries are facing flooding Heavy monsoon rain in and around India's commercial capital Mumbai, in the year 2005 caused severe flooding. World's major cities, including Bangkok, London, Miami and New York, could be flooded by the end of the century, according to a new analysis of current temperatures in the Arctic region. By then, global temperatures will be at an average of 3 degrees C. higher than now or about as hot as it was nearly 130,000 years ago, when ocean levels were four to six metres higher. Dhaka city is no exception. So too Chittagong. Developments may not pause and sufferings may not be eliminated. Mitigation or adaptation as such is the only route out from hazards of development and the resultant floods in the city.

With forty percent of the country's land mass only one meter above the sea level Dhaka city has an area of 360 square kilometres virtually built on and spread over low lying deltaic zone. So why should there not be floods? The city of Dhaka is said to have once plus-minus 50 criss-cross canals facilitating upland drainage. Most of them in any case disappeared and the visible rest are though dysfunctional or have lost the hydraulic characteristics of a stream, channel or a pond. In the process of urbanisation of Dhaka as water bodies has been converted into lands and land has been converted from fields or forestry to roads, buildings and car parks, it lost its hydraulic properties to store, absorb and convey the surface runoff. Urbanization has multiplied runoff roughly by 5 times that of what would occur on natural terrain. During the periods of flooding, the city streets become flowing rivers, while basements become traps as they fill with water. A start-monsoon rainfall with 50mm a day may cause floods in the city. The 150 mm torrential rain is experienced to have disrupted the normal city life. The highest ever recorded 341 mm rainfall a day in 2004 snapped all activities at the national level. Along with immense sufferings to the city population the rain generated flood severely damages and disables the infrastructures eventually surcharging pressures on prefecture budgets for recurring expenditures on its rehabilitation.

Not more than thirty percent of the city area during torrential rain remains flood free. Fifty percent faces floods and the rest twenty percent that practically floats on waterlogged area is subjected to severe flooding. Inadequate drainage in general has been known as the reason for such flooding. Unplanned building constructions are taken as the wide spread impression for such poor drainage while the Building Code of Bangladesh similar to other countries do not provide for any flood risk. Blocking drainage conduits by dumping solid objects and polythene into it, reducing water absorption capacity of soil by concreting the surface area, obstructing run-off discharge by building unplanned or ill-planned concrete structures, shrinking drainage cross-sections by grabbing the natural outlet canals, squeezing the storage capacity by encroaching the fringes of the detention pond, and strangling the peripheral channels by obstructing the drainage are accepted as the major cause of city flooding. The climate change impacts altering the precipitation patterns are close behind these reasons. The cumulative neglects of the urbanisation process have the progressive impacts. Added to it is the inadequacy of professionals' vision and residents' awareness.

Every time the city is flooded a high level expert committee has been formed to study and investigate into the causes and recommend remedies for such calamities. The politicians flanked by experts frog-jump into the media-lens riding assurances and relief operations with commitments of high sounding plan. The problem is thus buried well before it is realized at the level of policy and decision making process.

Not accepting flooding as inevitable the city residents, political leaders, engineers and environmentalists have to ask what human interventions increased the severity and what steps should be appropriate to mitigate or adapt recurrent flooding. Structural measures may provide safety from floods but consequently shall result in a net increase in habitation density in protected areas. These improvements will also provide politicians with visible evidence to city residents that resources were being put to work. The much talked about flood project widely known as eastern bypass-cum-flood embankment for instance may provide reduced flooding depths in specific areas thereby increasing the habitation which over time shall turn into to-day's problematic DND project; if implemented in a traditional manner.

Dhaka city flooding may not be labelled as misdeeds of individuals or engineers. The dynamics of social developments knew no consequences. Once realised the problems there is nothing wrong in try-bringing corrections or diversions to the process. The city of Dhaka requires preserving floodplains and seeking to accommodate floods not control anymore; this has to be given the due cognisance. In doing so the issues of recharging ground water basins, increasing soil moisture storage by absorption, providing facilities for non-consumptive use of water, flushing city surface through creeks, creating ponds for use as emergency fire hydrants and restoring open water bodies for aesthetic and ecological needs are to be taken into consideration.

The Dhaka city needs to take the bold decision to move away from the conventional "structural approach" to adaptive "hydrological improvement approach" and to embrace a program of floodplain and wetland preservation and restoration. The first step would be to free the natural drainage channels, detention ponds, water bodies, lakes and lagoons and, any other open space. Two of the steps that may be used next are acquisition of flood-prone property and implementation of mitigation projects which will maximize vegetative cover and minimize structural components. The innovative measures to adapt to city flooding may include using open spaces and underground areas, and stormwater infiltration. The city residents are expected to voice now reconsidering the ongoing development practices in the city floodplains and upstream segments of its watersheds; not really staying satisfied with assurance one after another.

Md. Saeedur Rahman is former Chief Engineer of BWDB.