Bangladesh is a river-rich country. Because of its location on the Brahmaputra River Delta and the numerous distributaries that run into the Bay of Bengal, it is prone to floods. Bangladesh faces the cumulative effects of floods due to water flashing from nearby hills, the accumulation of the inflow of water from upstream catchments, and locally heavy rainfall exacerbated by drainage congestion because it is part of such a basin and is less than 5 meters above the mean sea level.
This is a problem that Bangladesh encounters virtually every year. Coastal flooding, along with river bank bursts, is a typical occurrence in Bangladesh, and it has a significant impact on the country's scenery and society. Bangladesh's floodplain covers 80% of the country, and it has a long coastline, putting the country at risk of widespread destruction on a regular basis.
While more permanent barriers are being constructed with reinforced concrete, many embankments are formed entirely of dirt and turf by local farmers. Flooding is most common during the monsoon season, which lasts from June to September. The relief rainfall provided by the Himalayas adds to the monsoon's convectional rainfall. Himalayan meltwater is also a substantial contributor.
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Approximately 26,000 square kilometers (almost 18 percent of the country) of Bangladesh is flooded each year, killing over 5,000 people and demolishing over seven million dwellings. As happened in 1998, the impacted region during catastrophic floods might reach up to 75% of the country.
This amount represents 95% of the overall annual inflow. Rainfall generates just roughly 187 trillion cubic meters of streamflow inside the country during the same time period. Floods have wreaked havoc on Bangladesh in the past, particularly in 1951, 1987, 1988, and 1998. A considerable area of Bangladesh was flooded in the South Asian floods of 2007.
Floods can be caused by a number of things, including sediment being dumped into river channels. Sediment is one major factor as it reduces the hydraulic radius and efficiency on these rivers making them more susceptible for flooding from monsoon rainfall or other storm events during those times too! Deforestation also plays its role through causing landslides which dump huge amounts water onto nearby land creating lakes that then runoff at certain intervals depending where you live- this causes even greater problems downstream though because now there's twice as much flow coming towards us all at once instead of just one channel going left before right etcetera.
While flooding and efforts to mitigate its effects are widespread across the country, numerous types of floods have recently occurred on a regular basis, affecting different places in different ways. These sorts of floods include:
flash floods in hilly areas
monsoon floods during monsoon season
normal bank floods from the major rivers, Brahmaputra, Ganges and Meghna
The country has a long history of destructive flooding that has had very adverse impacts on lives and property. In the 19th century, six major floods were recorded: 1842, 1858, 1871, 1875, 1885 and 1892. Eighteen major floods occurred in the 20th century. Those of 1951, 1987, 1988 and 1998 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 square kilometres of land, (about 40% of the total area of the country) and was estimated as a once in 30-70 year event. 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 square kilometres 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 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, including half of Dhaka. 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 synchronisation of peak flows of the major rivers contributed to the flood. 30 million people were made homeless and the death toll reached over a thousand.
The flooding caused contamination of crops and animals and unclean water resulted in cholera and typhoid outbreaks. Few hospitals were functional because of damage from the flooding, and those that were open had too many patients, resulting in everyday injuries becoming fatal due to lack of treatment. 700,000 hectares of crops were destroyed, 400 factories were forced to close, and there was a 20% decrease in economic production. Communication within the country also became difficult.
The 1999 floods, although not as serious as the 1998 floods, were still very dangerous and costly. The floods occurred between July and September, causing many deaths, and leaving many people homeless. The extensive damage had to be paid for with foreign assistance. The entire flood lasted approximately 65 days.
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The 2004 flood was very similar to the 1988 and 1998 floods with two thirds of the country under water. In early October 2005, dozens of villages were inundated when rain caused the rivers of northwestern Bangladesh to burst their banks.The floods that hit Bangladesh in 2007 affected 252 villages in 40 districts causing millions of people became homeless. Last floods occurred in 2015 and 2017.
The 1998 floods in Bangladesh were among the most devastating natural disasters to occur this century. From July-September, some one million homes and other buildings were damaged by record breaking rainfall which caused extensive deep flooding events that lasted for months on end affecting nearly six million families whose main food crops - rice primarily but also wheat or corn if they practiced a mixed farming lifestyle- ultimately perished from waterlogged soil conditions due not only rivers overflowing their banks before being blocked off at least temporarily during September when major storm systems arrived unexpectedly out of nowhere just days apart giving people no time whatsoever between storms so all three could be.
The Bangladesh Flood of 2007 was caused by storms that triggered devastating landslides in the hills. The rains also caused great flooding, which took many lives and destroyed homes throughout this country-wide tragedy.