Bangladesh is used to flooding, but the 2020 monsoon season was most devastating than ever, leaving more than 25% of the country under water and displacing hundreds of thousands of people. But floods carry fertile sediment through the country, and are recognised as essential to the nation. A feature article in BBC Future delves into options to balance the devastating and restorative power of floods in Bangladesh.
Bangladesh is a delta nation. Most of it is located within the floodplains of three great rivers: the Ganges, Brahmaputra and Meghna, and their tributaries. The combined discharge of those three rivers is among the highest in the world. Dominated by the fertile Ganges-Brahmaputra delta, the largest river delta in the world, the majority of the country is a metre or less above sea level, predominantly rich fertile flat land. Its geography, together with socio-economic factors (population density and poverty levels) make it highly vulnerable to the effects of climate change. It was ranked as the seventh hardest-hit country by extreme weather events for the period 1999-2018 in the Global Climate Risk Index 2020, calculated by nonprofit Germanwatch.
Past efforts to manage floods tried to resist the flood-prone nature of the country. The Flood Action Plan of 1990 has been criticised as unrealistic and expensive, with structural flood control interventions that did not work as anticipated. Embankments were used to create polders that would protect low-lying islands. One of the main problems of building defensive walls is that they disrupt sediment flow: polders were found to lose elevation in comparison with surrounding areas. Thus, blocking sediment from spreading over the landscape during gradual flooding lowered ground levels and increased the risk of more sudden floods. In addition, flood defences give people a false sense of security, so they build closer to flood-prone zones. Traditionally, settlements were built on higher ground, raising the area by digging and elevating the soil, which allowed people to cope with all but very extreme events.
Now that climate change is set to make flooding worse, the methods that worked in the past may not be resilient enough for what is to come. Khondker Neaz Rahman, who has worked with the Bangladesh government and the United Nations Development Programme on urban and regional planning calls for a world without structural defences as the way forward, while recognising that moving away from the conventional approach to flood control will take time. Containing the rivers and the delta of Bangladesh has proved inefficient, but he thinks removal of structures currently in place would cause more damage.
The proposed approach is to increase resilience by planning for floods – examples are elevated houses, traditional boats when roads are inundated – rather than preventing floods. The country has to find a middle ground between existing defences and starting from scratch; one thing is for sure, and that is the solutions ahead should be multifaceted and reflect Bangladesh’s relationship with water, both a source of destruction and a source of life. Just so we can grasp this, Rahman points out that “Bonna”, which means flood, is a traditional woman’s name. You certainly would not name your daughter drought, or earthquake.