Floods in Bangladesh
Encyclopedia
The South Asia
n country of Bangladesh
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 during the monsoon. 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.
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, 1998 and 1988. 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 arteficial 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 Nino becomes increasingly frequent, and flood events appear to become more extreme, the previously relaiable monsoon may be succeeded by years of drought or devastating floods. Also, some 3 thousand people were left homeless or killed.
Flash floods in the eastern and northern rivers are characterized by a sharp rise followed by a relatively rapid recession, often causing high flow velocities that damage crops and property.
Local floods due to high localized rainfall of long duration in the monsoon season often generate water volumes in excess of the local drainage capacity, causing localized floods due to drainage congestion.
Monsoon floods from the major rivers generally rise slowly and the period of rise and fall may extend from 10 to 20 days or more. Spilling through distributaries and over the banks of the major rivers causes the most extensive flood damage, particularly when the three major rivers rise simultaneously.
Floods due to storm surges in the coastal areas of Bangladesh, which are generated by tropical cyclone, cause extensive damage to life and property. These cyclones are predominant during the post-monsoon (October and November) and pre-monsoon (April to June) period.
The catastrophic flood 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.
South Asia
South Asia, also known as Southern Asia, is the southern region of the Asian continent, which comprises the sub-Himalayan countries and, for some authorities , also includes the adjoining countries to the west and the east...
n country of Bangladesh
Bangladesh
Bangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...
is prone to the natural disaster of flooding due to being situated on the Ganges Delta
Ganges Delta
The Ganges Delta is a river delta in the South Asia region of Bengal, consisting of Bangladesh and the state of West Bengal, India. It is the world's largest delta, and empties into the Bay of Bengal...
and the many tributaries flowing into the Bay of Bengal
Bay of Bengal
The Bay of Bengal , the largest bay in the world, forms the northeastern part of the Indian Ocean. It resembles a triangle in shape, and is bordered mostly by the Eastern Coast of India, southern coast of Bangladesh and Sri Lanka to the west and Burma and the Andaman and Nicobar Islands to the...
. 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 during the monsoon. 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.
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, 1998 and 1988. The 2007 South Asian floods
2007 South Asian floods
The 2007 South Asian floods were a series of floods in India, Nepal, Bhutan, Pakistan and Bangladesh. News Agencies, citing the Indian and Bangladeshi governments, place the death toll in excess of 2,000...
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 arteficial 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 Nino becomes increasingly frequent, and flood events appear to become more extreme, the previously relaiable monsoon may be succeeded by years of drought or devastating floods. Also, some 3 thousand people were left homeless or killed.
Categories
In Bangladesh, lthe following types of floods are normally encountered.Flash floods in the eastern and northern rivers are characterized by a sharp rise followed by a relatively rapid recession, often causing high flow velocities that damage crops and property.
Local floods due to high localized rainfall of long duration in the monsoon season often generate water volumes in excess of the local drainage capacity, causing localized floods due to drainage congestion.
Monsoon floods from the major rivers generally rise slowly and the period of rise and fall may extend from 10 to 20 days or more. Spilling through distributaries and over the banks of the major rivers causes the most extensive flood damage, particularly when the three major rivers rise simultaneously.
Floods due to storm surges in the coastal areas of Bangladesh, which are generated by tropical cyclone, cause extensive damage to life and property. These cyclones are predominant during the post-monsoon (October and November) and pre-monsoon (April to June) period.
Flood history
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 flood 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
Himalayas
The Himalaya Range or Himalaya Mountains Sanskrit: Devanagari: हिमालय, literally "abode of snow"), usually called the Himalayas or Himalaya for short, is a mountain range in Asia, separating the Indian subcontinent from the Tibetan Plateau...
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
Khulna District
The district of Khulna consists 10859 mosques, 680 temples, 81 churches, 15 Buddhist temples and 9 tombs.-Places of interest:*The Sundarbans is the largest mangrove forest in the world. The royal Bengal tiger inhabits the area; it is said that seeing the tiger enables a person to understand what a...
.
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
Dhaka
Dhaka is the capital of Bangladesh and the principal city of Dhaka Division. Dhaka is a megacity and one of the major cities of South Asia. Located on the banks of the Buriganga River, Dhaka, along with its metropolitan area, had a population of over 15 million in 2010, making it the largest city...
, 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
Bangladesh
Bangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...
over their banks in early October 2005. The Moderate Resolution Imaging Spectroradiometer on Terra satellite captured the top image of the flooded Ghaghara
Ghaghara River
Karnali or Ghaghara is a perennial trans-boundary river originating on the Tibetan Plateau near Lake Mansarovar. It cuts through the Himalayas in Nepal and joins the Sarda River at Brahmaghat in India. Together they form the Ghaghra River, a major left bank tributary of the Ganges. With a length of...
and Atrai
Atrai River
Atrai River flows in West Bengal and northern parts of Bangladesh.In ancient times the river was called Atrei and finds a mention in the Mahabharata. It is linked with Karatoya River. It originates in West Bengal and then after flowing through Dinajpur District of Bangladesh, it enters India again...
Rivers on October 12, 2005. The deep blue of the rivers is spread across the countryside in the flood image.