Floods in Dhaka

Dhaka has over ten million inhabitants and has been central to Bangladesh's economic success in recent years. The city is already very vulnerable to flooding, especially during the monsoon season, as shown by five major floods since 1980. The 1988, 1998 and 2004 floods were particularly severe and brought large economic losses.

When major floods occur they hit around half the city's area. They are mainly caused by spillover from surrounding rivers and rainfall that generates runoff beyond the capacity of the drains. The provision for infrastructure and services has not kept pace with the city's population growth.

The 40 percent of the population living in slums and squatter settlements are most severely affected by floods, water-logging and other associated problems. The unequal development and management of utilities and bad management of water and waste water are caused by both non-compliance with national policies, rules and regulations and insufficient resources.

Climate change will affect Dhaka in two main ways: through floods and drainage congestion and through heat stress. Melting glaciers and snow in the Himalayas and increasing rainfall will lead to more frequent flooding (water-logging, drainage congestion from river floods and excessive rainfall during the monsoon already cause very serious damage). Furthermore, Dhaka may also face 'heat island' problems, because temperatures in the city are a few degrees higher than in surrounding areas.

Infrastructure, industry, commerce and utility services are key sectors at risk from flooding. The impaired performance of these sectors during and after flooding increases the vulnerability of city dwellers, with economic and social class dictating the severity of that vulnerability. The loss of life and livelihoods, and impacts on human health, are particularly severe for lower-income groups.

Measures have been taken to improve air quality and protect the city from devastating floods, but far more is needed if Dhaka is to adapt to climate change. Recent erratic rainfall brought unusual urban flooding as a result of drainage congestion and inadequate facilities for pumping water from inside the flood embankment.

Are existing flood management measures adequate to address future flooding, which is anticipated to be more frequent and intense? Such measures could include:

• Spatial planning for unbuilt areas of Dhaka should ensure that these areas avoid flooding and avoid contributing to flood risks for the whole city.
• Changes to the design of the embankment and provision of adequate pumping systems to drain rainwater from the city.
• City-wide adaptation to allow Dhaka to cope with the changes in intensity and pattern of rainfall under a warmer climate.

Mozaharul Alam
Bangladesh Centre for Advanced Studies, House 10, Road 16A, Gulshan-1, Dhaka, Bangladesh.
mozaharul.alam@bcas.net