General Causes of Bangladesh floods
Physical causes
- 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
- 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.
- Bangladesh has a monsoon climate and the annual torrential rains which result often result in the rivers exceeding their capacity and flooding.
- 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
- 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.
- 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.
- 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;
- 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.
Caused of the 2004 floods
In late-June 2004, heavy monsoon rains caused the Meghna River to rise, which reached its peak level in early-July. The Jamuna and Padma Rivers also burst their banks in early July, due to heavy rains in the north of the country. This subsequentlycaused flash floods in the north and the west central districts. The floods spread, eventually impacting Dhaka and other central districts. 36 million people (about 25 percent of the population) across 39 districts were affected by the floods many of which were made homeless. Approximately 38 percent of Bangladesh was inundated by the time the waters began to recede in late-August, including 800,000 hectares of agricultural land. As of mid-September, the death toll had reached almost 800. During the emergency, access to potable water and sanitation facilities was diminished, as thousands of tube wells and latrines were contaminated. The floods also caused heavy damage to
major infrastructure such as roads, bridges, railway, embankments, irrigation systems and rural
infrastructure as well as losses to the agriculture sector and small-scale businesses. Between 10 and 16 September, a localized monsoon depression swept over Bangladesh, bringing three times the normal rainfall and causing flooding in the Dhaka and southwest and central areas of the country. Several districts, which had been spared during the previous flood, were affected this time. The Asian Development Bank (ADB) is continuously monitoring and assessing the damage and impact of this flood over the next month through its Bangladesh Resident Mission (BRM). Relief operations are continuing in many areas while rehabilitation efforts are underway across flood-affected areas.
Flood management
Flood management strategies adopted in the country have continuously evolved over the last 50
years, in three distinct phases of their development, and with mixed experiences. Initially, the
emphasis was on structural measures through the implementation of some large-scale flood
control, drainage and irrigation (FCDI) projects. However, it was soon recognized that their
implementation involved large investments, as well as longer duration for their completion.This was hard engineering and was not suited to the country as it was not deemed sustainable which in a cost benefit analysis would make it seem pointless. It was then decided that a more softer approach was needed. The construction of small and medium scale projects began and they quickly provided benefits As a result, since the 1960’s about 628 large, medium and small-scale projects have been implemented; they comprise levees and embankments, drainage channel improvements, drainage
structures, dams and barrages, pumping systems, etc. They have provided flood protection to about 5.37 million ha of land, which is about 35% of the total area. Non-structural measures such as flood forecasting and warning were later incorporated, as it was felt that structural measures alone could not mitigate flood problems. The Flood Forecasting and Warning System (FFWS), established in the 1970s, was modernized in 1996 and then again as of 2000. It now covers all the flood-prone areas of the country with 85 flood-monitoring stations, and provides real-time flood information and early warning with lead-times of 24 and 48 hours. The FFWS is currently assisting Government, disaster managers and the communities living in the flood prone areas in matters of flood preparedness, preparation of emergency mitigation plans, agricultural planning and rehabilitation.