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Underlying risk drivers accumulate risk in multiple hazard Dhaka

Areas of Dhaka susceptible to liquefaction and change in water and the built environment in West Dhaka between 1996 and 2009 © Rahman (2010) adapted from IRS Image 1996 and Google Earth

Bangladesh

The 1897 Assam earthquake (also known as the Great Indian Earthquake), one of the largest ever recorded in South Asia, caused great damage to the city’s buildings and infrastructure (Al-Hussaini, 2003). However, it is not only the 150-fold increase (from 100,000 to 15 million people) in exposed population that has led to Dhaka’s current level of earthquake risk. The city has also been unable to address the processes that shape and accumulate that risk over time.

Many areas surrounding central Dhaka are flood prone during the rainy season, and until recently were occupied by natural water bodies and drains, vital to the regulation of floods. Land use planning instruments such as the Dhaka Metropolitan Development Plan restrict development in many of these areas. Despite the Plan, these areas are still being rapidly urbanized through private- and public-sector projects (Figure). Destroying retention ponds and drains increases risks of seasonal flooding just as building in drained wetlands increases earthquake risk. During an earthquake, sands and silts can behave like a liquid to the point where the soil no longer supports the weight of buildings and infrastructure, which may subsequently collapse or suffer heavy damage.

An innovative cyclone shelter programme has helped Bangladesh dramatically reduce cyclone mortality since the 1970s. In the past four decades, Bangladesh has been struck by three severe cyclones: Bhola (1970), Gorky (1991) and Sidr (2007). Bhola caused an estimated 300,000 deaths and Gorky was responsible for more than 138,000. The death toll for Sidr, however, was ‘only’ around 4,000 (EMDAT, 2010a). Unfortunately, the disaster management capacities that have reduced cyclone mortality have not been able to address earthquake risk in Dhaka. There is an Earthquake Zoning Plan for Dhaka, but its enforcement and general urban improvement remain major challenges. Dhaka’s expansion vividly illustrates how drivers such as badly planned and managed urbanization, ecosystem decline and poverty interact to build risk over time (UNISDR, 2009).

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