What natural (physical) features of the Ganges-Brahmaputra drainage basin make Bangladesh vulnerable to river flooding each year? The deltas of the Ganges and Brahmaputra rivers in South Asia flood on a seasonal basis. The flooding keeps the soil fertile because the rivers deposit silt which forms fertile soil each year. Partly because of the flooding, it is one of the most densely populated areas of the world with millions of people in Nepal, Northern India and Bangladesh depending on the rivers and fertile soils for their livelihoods. The natural causes of the flood in Bangladesh are:
* Most of the country consists of a huge flood plain and delta. * 70 per cent of the total area is less than 1 meter above sea level. * 10 per cent of the land area is made up of Lakes and Rivers. * Snowmelt for the Himalayas takes place in late spring & summer. * 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. So the main cause was the long period of heavy rain, which caused that all 3 rivers have their peak flow at the same time. The monsoon rains cause rivers such as the Jamuna (Brahmaputra) and Padma (Ganges) to overflow their banks between July and mid-august. Most of Bangladesh’s 153 million inhabitants live on the floodplains of these rivers. For most of them, the seasonal flood is essential for their survival as it brings water in which to grow the main crops of rice and jute, as well as silt to fertilize their fields. In 1998, 68 per cent of the country was flooded, unprecedented in terms of both its magnitude and duration. (Fig 1.0)
How has human activity in the Ganges-Brahmaputra basin was increased the risk of damage from flooding? Bangladesh is one of the world’s most densely populated, and the poorest countries in the world. It also has one off the three most powerful rivers passing through it The Ganges, the Meghna and the Brahmaputra. It experiences floods and tropical storms every year. In 1998 one of the most terrible ones.
Bangladesh has many disadvantages; there are many physical and human causes that allowed the floods to be worse. Here are some human causes of the flood in 1998: * Human mismanagement has increased the magnitude and frequency of flooding by: Building on the floodplains to house the country’s growing population & cutting down trees in the upper drainage basin. * 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. * The building of dams in India has increased the problem of sedimentation in Bangladesh. * Global warming is blamed for sea level rise, increased snow melt in the Himalaya and increased rainfall in the region. * Poorly maintained embankments leak & collapse in times of high discharge.
(Fig. 1.0)
How did extreme weather conditions in 1998 cause the worst flooding ever known in Bangladesh? (Fig. 2.0) May and June: there was very little rainfall in the drainage basin area, 92 per cent of which lies beyond the national border of Bangladesh. July: Heavy rainfall at the beginning of the month caused by Brahmaputra, Meghna and Ganges rivers to rise rapidly. When the rivers reached a peak on the 28th, 30 per cent of the country was under water. August: The flood situation slowly improved until the 20th, when most rivers again succeeded their danger levels. A second flood peak, reached on the 30th, saw floodwaters cover over 40 per cent of the country.
September: Further heavy rain, unusually late in the year, caused the rivers to reach a third and the highest peak on the 7th. By that time almost 70 per cent of the country was, or had been, under water. Although the situation improved after that date, it was the end of the month before the floodwaters drained away from many areas. Most floods follow heavy rain or melting snow, frozen ground and already high river levels. The floods in Bangladesh begin through a combination of heavy monsoon rains flooding the rivers and abnormally high tides in the Bay of Bengal preventing floodwater from running off the land and into the sea.
(Fig. 2.0)
The diagram above shows the results of all the years in Bangladesh. As you can see, in 1998 there was the heaviest rainfall.
What were the impacts of the 1998 flood on:
* Human life
* Property
* The economy of Bangladesh?
The flood in 1998 has caused a lot of worse impacts. Railways roads and bridges had been swept away. Most parts of the country were without electricity for several weeks and, because floodwater polluted wells there was no safe drinking water. Hospitals were already full of people suffering from dysentery and diarrhea and the threat of disease, especially cholera, was increasing. Parts of Dhaka, including the international airport were less than 2 meters of water. Delivering overseas aid including food and medical supplies became almost impossible. On 26 august, two weeks before the third peak, and a month before the floodwaters finally receded, urgent supplies were requested. Apart from destroying crops and basic infrastructural features such as roads and bridges, it caused the deaths of over 10000 people, destroyed 7 million homes and left more than 25 million people homeless.
Here are some precautions that have been taken to reduce the risk: Short term management:
* Boats to rescue people. (Fig. 3.0)
* Emergency supplies for food, water, tents and medicines.
* Fodder for livestock.
* Repair and rebuild houses, as well as services such as sewage etc.
* Aid from other countries.
Long term management:
* Reduce Deforestation
* Build 7 large dams in Bangladesh to store excess water.
* Build 5000 flood shelters to accommodate all the population.
* Build 350 km of embankment – 7 meters.
* Create flood water storage areas. (Fig.4.0)
* Develop an effective Flood warning scheme.
