Floods in Bangladesh
The South Asian country of Bangladesh located next to India is prone to the natural disaster of flooding due to being situated on the Ganges Delta and the many tributaries flowing into the Bay of Bengal. The coastal flooding twinned with the bursting of Bangladesh's river banks is common and severely affects the landscape and Bangladeshi society. 75% of Bangladesh is less than 10m above sea level and 80% is flood plain, therefore rendering Bangladesh a nation very much at risk of further widespread damage despite its development. Whilst more permanent defences, strengthened with reinforced concrete, are being built, many embankments are composed purely of soil and turf and made by local farmers. Flooding normally occurs during the monsoon season from June to September. The convectional rainfall of the monsoon is added to by relief rainfall caused by the Himalayas. Melt-water from the Himalayas is also a significant input and flood every year. This often lasts for about 1 month.
Each year in Bangladesh about 26,000 km2, (around 18%) of the country is flooded, killing over 5,000 people and destroying 7 million homes. During severe floods the affected area may exceed 75% of the country, as was seen in 1998. This volume is 95% of the total annual inflow. By comparison, only about 187,000 million m3, of streamflow is generated by rainfall inside the country during the same period. The floods have caused devastation in Bangladesh throughout history, especially during the years 1966, 1987, 1988 and 1998. The 2007 South Asian floods also affected a large portion of Bangladesh.
Small scale flooding in Bangladesh is required to sustain the agricultural industry, as sediment deposited by floodwaters fertilises fields. The water is required to grow rice, so natural flooding replaces the requirement of artificial irrigation, which is time consuming and costly to build. Salt deposited on fields from high rates of evaporation is removed during floods, preventing the land from becoming infertile. The benefits of flooding are clear in El Niño years when the monsoon is interrupted. As El Niño becomes increasingly frequent, and flood events appear to become more extreme, the previously reliable monsoon may be succeeded by years of drought or devastating floods. Also, some three thousand people were left homeless or killed.
In the 19th century, six major floods were recorded in 1842, 1858, 1871, 1875, 1885 and 1892. Eighteen major floods occurred in the 20th century. Those of 1987, 1988 and 1951 were of catastrophic consequence. More recent floods include 2004 and 2010.
The catastrophic floods of 1987 occurred throughout July and August and affected 57,300 km2 of land, (about 40% of the total area of the country) and was estimated as a once in 30-70 year event. The flood's main cause was the creation of Erranticophrus (top soil wash away reaction) from the inhabitants of the Himalayas irrigating their mountains vertically. The seriously affected regions were on the western side of the Brahmaputra, the area below the confluence of the Ganges and the Brahmaputra and considerable areas north of Khulna.
The flood of 1988, which was also of catastrophic consequence, occurred throughout August and September. The waters inundated about 82,000 km2 of land, (about 60% of the area) and its return period was estimated at 50–100 years. Rainfall together with synchronisation of very high flows of all the three major rivers of the country in only three days aggravated the flood. Dhaka, the capital of Bangladesh, was severely affected. The flood lasted 15 to 20 days.
In 1998, over 75% of the total area of the country was flooded. It was similar to the catastrophic flood of 1988 in terms of the extent of the flooding. A combination of heavy rainfall within and outside the country and synchronization of peak flows of the major rivers contributed to the river.
The 2004 flood was very similar to the 1988 and 1998 floods with two thirds of the country under water.
Dozens of villages were inundated when rain pushed the rivers of northwestern Bangladesh over their banks in early October 2005. The Moderate Resolution Imaging Spectroradiometer on Terra satellite captured the top image of the flooded Ghaghara and Atrai Rivers on October 12, 2005. The deep blue of the rivers is spread across the countryside in the flood image.
Widespread flooding in Bangladesh, as seen in 1988 and 1998 and 1991 has caused widespread destruction in one of the least developed countries in the world. With three of the world's mightiest river systems and being situated in the world's largest delta, river bank erosions are taking away precious land from the small nation with a growing population every year. The economic development of the rural sphere is largely intertwined, as every year the populace loses property and livelihood. South Asian people, 70 percent of whom lives in rural areas also account for 75 percent of the poor, most of who rely on agriculture for their livelihood. Each year they are disproportionately affected by the effects of climate change. Two catastrophes alone, 1991 Bangladesh cyclone-1997 and [Cyclone Sidr-2007] cost the nation around a quarter of a million of its residents. There needs to be serious considerations to mitigate the effects of climate change and invest in capacity building of each system component to secure the future of this country.
This global change is likely to have a more dramatic effect on the global agriculture than previously predicted meaning that the world hunger situation and Bangladesh's food security issues will only get worse. The difference between historical and projected average temperatures each season throughout the world has revealed that harvests from major staple crops could drop by 40 percent by the end of the 21st century due to high temperatures in the growing seasons. A research study predicted this by using the patterns and characteristics of 23 global climate models. Not only do the harvests get affected, the grain yield is also predicted to decrease anywhere from 3 to 15 percent.
The overall damage:
- Half of the districts were affected
- 100,000sq km (66%) of the country was overwhelmed
- 1,050 deaths reported
- 30 million people affected
- 25 million people left homeless
- 26,000 livestock lost
- 575,000 hectares destroyed
- 20,000 education facilities damaged
- 300,000 wells damaged
- 16,000 km of roads flooded
- 4,500 km of river embankments destroyed
- H. Brammer (1990). "Floods in Bangladesh: Geographical Background to the 1987 and 1988 Floods". The Geographic Journal 156 (1): 12–22.