Bangladesh Coastal Flooding Case Study 1998 Sarah

Causes of Flooding in Bangladesh

Posted in Causes of the Flooding in Bangladesh, Environmental Issue, Floods In Bangladesh, Geography, Population by Khaled Saifullah on March 27, 2009


Photo: CGZ

Bangladesh is one of the world most densely populated country and one of the most susceptible countries to flood disasters. It also has one of the three most powerful rivers passing though it Ganges, Meghna and Brahmaputra. About one half of the land area in Bangladesh is at an elevation of less than 8 meters above sea level.  Up to 30% of the country has been covered with flood waters.  In 1991 more 200,000 deaths resulted from flooding and associated tropical cyclones.

Photo: USAID

There are many physical and human causes that allowed the floods to be worse; such as:

The Physical Causes of the Floods:

  • Most of the country consists of a huge flood plain and delta.
  • Snowmelt from the Himalayas takes place in late spring & summer.
  • 70% of the total area is less than 1 meter above sea level.
  • 10% of the land area is made up of Lakes and Rivers.
  • Bangladesh experiences heavy monsoon rains, especially over the highlands.
  • Tropical storms bring heavy rains and coastal flooding.
  • The main cause was the above average & long period of heavy rain which caused all 3 rivers to have their peak flow at the same time.
  • In the spring, melting snow from the Himalayas further increases the flood risks as torrents of melt water enter the rivers at their source.

The Human Causes of the Floods:

  • Deforestation in Nepal and the Himalayas increases run off and add to deposition and flooding downstream.
  • Urbanization of the flood plain has increased magnitude & frequency of floods.
  • Global warming is blamed for sea level rise, increased snow melt & increased rainfall in the region.
  • The building of dams in India has increased the problem of sedimentation in Bangladesh.
  • Poorly maintained embankments (levees) leak & collapse in times of high discharge.
  • Increasing population pressure in Bangladesh itself has resulted in the sinking of many new wells resulting in the lowering of the water table and the subsequent subsidence of land making it even more prone to flooding.

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BANGLADESH FLOODS

Between July-September 1998, Bangladesh suffered one of its worse ever floods. Despite being flooding being common in this country, the floods of 1998 were particularly severe resulting in over 1000 deaths and 30 million people being made homeless and newspapers / media sources were full of headlines like the following; South Asia - Bangladesh Floods Rise again (BBC Article) and Floods threaten 20 million lives in Bangladesh.

So why is Bangladesh so prone to flooding? Well the answer to this requires consideration of both the physical landscape and conditions of the country and the impact of its population.

CAUSES OF FLOODING IN BANGLADESH

Physical (Natural) causes of flooding in Bangladesh

  1. Bangladesh is a very low lying country, with 70% of its land area being less than 1m above sea level and 80% of it being floodplain.
  2. Bangladesh receives large amounts of water passing through it with two major rivers (the Ganges and Brahmaputra) converging and forming a huge delta (see picture) formed from silt deposited by the river as it enters the sea. Both rivers have large volumes of water flowing through them to the sea as they have large drainage basins which increasing the flood risk;
  3. Bangladesh has a monsoon climate and the annual torrential rains which result often result in the rivers exceeding their capacity and flooding;
  4. In the spring, melting snow from the Himalayas further increases the flood risks as torrents of melt water enter the rivers at their source.
Human causes of flooding in Bangladesh
  1. Increasing population pressure in the foothills of the Himalayas where the rain contributes to the source of the River Ganges and Brahmaputra has resulted in intense deforestation. It is believed that this reduction in interception has resulted in more water entering the rivers - indeed with 92% of the area drained by the rivers being in countries other than Bangladesh, Bangladesh's proneness to flooding is exacerbated by population and environmental issues in countries other than its own, making it increasingly difficult to target the problems.
  2. Indeed deforestation in the headwaters is also believed to be responsible for the increased soil erosion which has led to large amount of silt being washed into the rivers and subsequently being deposited on the river bed, reducing its channel capacity and increasing the likelihood of flooding.
  3. Increasing population pressure in Bangladesh itself has resulted in the sinking of many new wells resulting in the lowering of the water table and the subsequent subsidence of land making it even more prone to flooding;
  4. Bangladesh is an LEDC and its lack of money and heavy national debt means that little money is available to spend on flood protection methods / defences and many existing defences lack upkeep and are of questionable use.

(click on the digram below for a summary of these)



EFFECTS OF FLOODING IN BANGLADESH

Remember - you must learn place specific detail when writing answers to case study questions if you are to be awarded the full marks.

POSITIVE EFFECTS OF FLOODING

It is important to remember that whilst flooding has serious impacts on human life in Bangladesh it is also instrumental in the wellbeing of Bangladesh's economy and the survival of its people. So what are these positive effects of flooding?
  1. As well as providing water for crops, when flooding occurs, as there is friction between the water and the surface of the land, the water slows down and loses its energy. This loss of energy results in the deposition of rich fertile soil resulting in the providing important nutrients enabling people to grow crops;
  2. This deposition of silt also creates land upon which people can live - for example the Ganges delta has been formed in this way as deposition has occured where the river has entered the Bay of Bengal.
EFFECTS OF THE 1998 FLOODS:
  1. Over two thirds of the land area was covered by water and the capital, Dhaka, was 2m underwater.
  2. 30 million people were made homeless in the floods with many losing all their belongings.
  3. 1,070 people died - this death toll resulted from a number of things. As well as people being killed by drowning in the flood waters, health problems increased the number of deaths further. Contamination of water by waste and dead bodies / animals, and the lack of a clean water supply resulted in the spread of disease such as cholera and typhoid. Further deaths from snake bites and other injuries which led to death through the lack of access to medical care.
  4. Food supplies were severely affected as flooding destroyed the rice stocks with a total of 668,529ha of crops being destroyed;
  5. The impact on the economy was signifcant with Bangadesh's export industries seeing a 20% decrease in production with over 400 clothing factories forced to close.
  6. Communications became difficult, with shopping impossible in the main port, as well as roads and railways having been swept away making the distribution of aid and the rescue operation very difficult;
The effects can clearly be seen in the following links:
Photographic presentation of the floods of 1998
Flood '98 - Bangladesh Photo Gallery

and all though very detailed this report provides an over view of the Disaster Impacts, Household coping and response. This chapter from the report provides specific detail on the impacts of the flood on agricultural production, employment and wealth.

FLOOD RELIEF / MANAGEMENT IN BANGLADESH

As has already been mentioned Bangladesh's low level of economic development means Bangladesh's flood protection is insufficent and a number of factors as discussed in this post have exacerbated the problems.

Following the 1998 floods a number of short term flood relief measures were put in place to try an minimise loss of life - these included:
  • international food aid programmes
  • the distribution of free seed to farmers by the Bangladesh govenrment to try and reduce the impact of food shortages - the government also gave 350,000 tonnes of cereal to feed people;
  • volunteers / aid workers worked to try and repair flood damage (see OCR A textbook - p.39 for further details)
In the long term a number of flood prevention measure are possible:
  • the creation of embankments (artificial levees) along the river to increase channel capacity and restrict flood waters - however since 1957, 7,500km of flood embankments have been constructed and yet many were breached in the 1998 floods;
  • constructing flood protection shelters (large buildings raised above the ground) to shelter both people and animals
  • emergency flood warning systems and plans made for organising rescue and relief services;
  • providing emergency medical stores in villages
  • building flood proof storage sheds for grain and other food supplies
  • dam construction upstream and major embankments around Dhaka have been suggested however lack of money has meant that these suggestions have not been taken further.
Further Links:

Conclusions and lessons from the 1998 floods
Lessons learning from the 1998 Bangladesh Floods

Map source: US CIA World Factbook (Creative Commons)
Photo source: Ganges delta - screenshot from NASA World Wind (Creative Commons)

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