Resilience to flash floods in wetland communities of northeastern Bangladesh
Introduction
Globally, hydrometeorological hazards such as floods, droughts, hurricanes, and coastal storm surges pose a direct threat to human lives and impact livelihoods due to widespread destruction and damage to crops, businesses and critical infrastructure. The frequency and strength of natural hazards varies globally. Nearly all continents were hit by some sort of natural hazards in 2017: flooding in South Asia, hurricanes, earthquakes and wildfires in North America, landslides and droughts in Africa, and volcanic eruption in Southeast Asia. Heavy monsoon rain and floods caused devastation in large parts of Bihar and Assam states of India, Bangladesh and Nepal that killed more than 1200 people over the summer of 2017 and triggered one of the worst humanitarian crises in years with more than 40 million people affected in the region. In Bangladesh alone, 145 people died, more than 100,000 houses were estimated to be completely destroyed and over 8 million people were affected by floods that covered one third of the country [1].
Hydrometeorological hazards, particularly floods and coastal inundation to storm surges associated with tropical cyclones, are common in Bangladesh. Due to its subtropical monsoon climate and the geographic location – downstream region of the Himalayan Rivers the Ganges, Brahmaputra and Meghna, every year, floods occur in low-lying areas of Bangladesh (Fig. 1) that cover a mean area of 20% (Fig. 2) of the 144,000 km2 area of the country. Based on inundation depth, it is estimated that a 10, 50 and 100-year flood event is projected to inundate approximately 37%, 52% and 60% of the country's total land area, respectively [2]. Outside the cyclone-affected coastal region where flooding occurs as a result of storm surges in April-May and October–November [3], there are four main types of flood in Bangladesh [4]: (i) monsoon, riverine floods when the major rivers overflow or cause their tributaries runs off into adjacent floodplains; (ii) flash floods in the eastern (hilly region), northeastern (Haor region) and northern areas (piedmont area) due to heavy and intense rainfall; (iii) localised coastal floods associated with tropical cyclones and storm surges in southern Bangladesh; and (iv) localised urban floods associated with intensive rainfall and/or onrush of river water when protective embankments breach takes place. The normal sequence of floods in Bangladesh starts with flash floods in the northeast, southeast and eastern hilly regions caused by pre-monsoon storms in April and May, and prior to the onset of the monsoon rainfall generally commences in June that normally causes riverine flooding.
Globally, with a population density of ~1000 inhabitants per km2 [6], Bangladesh is the country with the highest number of people and assets are exposed to increasing flood hazards [2]. River floods can inundate a large area, for example, nearly 60% area of Bangladesh was flooded in the catastrophic floods of 1988 and 1998 that inundated an area of 70% (Fig. 2) and killed some 2379 and 918 people respectively [7]. Floods in 2007 were one of the 95th percentile flood events inundating 42% of the entire Bangladesh and killed 1110 people [7]. These historical large river floods (e.g., 1987, 1988, 1999, 2004, 2007 and 2012) that lasted for a few weeks to 2–3 months, caused substantial damage to crops, houses, and means of livelihood, particularly of poor population in the country. The number of fatalities in these historical floods in Bangladesh has gone down over time [7]. In contrast to river floods that affect large proportion of land surface every year, flash floods generally affect a much smaller area (typically <5–20%) and the duration is smaller, commonly a few weeks to a month, but can have a catastrophic impact on human lives, properties and livelihoods. For example, flash floods of 2007 in northeastern Bangladesh affected ~10% area of the country but killed several hundred people and affected livelihoods in Haor communities [8].
Over the last few decades, numerous studies were conducted to identify hydrological and climatic drivers of flooding in Bangladesh [9], [10], [11]. On the other hand, a few studies [12], [13] looked at social vulnerability to flooding and resilience of communities and individuals, particularly poor people, living in floodplains and coastal regions, who may or may not receive direct support from the government of Bangladesh during disasters. This study aims to better understand the level of vulnerability and resilience to flash floods in the Haor region of northeastern (NE) Bangladesh by applying a number of social-science survey techniques.
Section snippets
Vulnerability and resilience to flash floods: theoretical considerations
Haors are low-lying, physiographic depressions or floodplain wetlands that are commonly found in NE Bangladesh. These areas experience greater amount of annual rainfall than the rest of the country. Due to their unique physical and social conditions, Haor inhabitants tend to be vulnerable to both riverine and flash floods. Despite this underlying vulnerability, people in the Haor region have been living with various hydrometeorological hazards (e.g., floods, tropical storms, waterlogging) for
The case of the 2017 flash flood in NE Bangladesh
Flash floods are sudden, localised flood events that occur when an exceptional amount of rain falls over a short period of time (a few hours to days) within a catchment producing a rapidly rising and fast moving river flows. Flash floods in Bangladesh are common and generally occur in early monsoon time (April-May), extensively in the Hoar region due to intensive rainfall within the country and upstream catchments in India. The word ‘Haor’ refers to a round to elliptical shaped, depressed
Study area
The Haor region of northeastern Bangladesh is a low-lying, bowl-shaped basin covering about 6000 km2 in Sunamganj district (Fig. 3, Fig. 5) of Sylhet Division [25]. The Surma River and Kushiyara River run through the district whilst Ratna River criss-crosses the district and beyond. The River Da'uka or Danuka also run through Sunamganj district. Sunamganj has a total population of 1,968,669 of which 51% are male and 49% are female. People of Sunamganj are racially and ethnically diverse,
Qualitative results from FGDs and KIIs
Qualitative data collation through FGDs and interviews in the study areas of Tahirpur upazila reflect on livelihoods and the way Haor inhabitants live their day to day life and provides a narrative description from the sufferers of how the flash-flood affected their lives and livelihoods (see Box 1 for 4 case stories in the Supplementary Information). One of the respondents described in their words:
“No one could understand our sufferings unless they see them with their own eyes. Within minutes
Conclusions
The Haor (wetland) region of northeastern Bangladesh is a flash-flood prone area due to its low-lying flat topography and high annual rainfall. Given the social conditions, wetland communities therefore become highly vulnerable to flood-related disasters. The 2017 flash floods in Bangladesh were especially abrupt and catastrophic compared to the flash floods of 2004, 2007 and 2012. The present study looks at vulnerability and resilience to flash floods in the Haor communities. The research was
Acknowledgements
Authors thank the field assistants who helped the social science survey team at Dhaka University, and are deeply indebted to the communities and individuals in the Haor region where this research was conducted. This research was funded (Project number: UCLC 302712) by the International Center for Collaborative Research on Disaster Risk Reduction (ICCR-DRR), Beijing, China.
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