Case Study - Rivers LEDC - Bangladesh

The damage potential of a flood is controlled by a number of factors:

• Location (densley/sparsely populated, urban/rural)
• Size of area affected by flooding
• Depth of flooding
• Duration of flooding
• Seasonal timing (especially important in rural areas - crop planting/harvesting)

On 29th August 1998, Bangladesh experienced it's worst ever river flood.

The cause: The simultaneous rising of the water levels in all three of it's major river system - the Gagnes, the Brahmaputra, and the Meghna.

The increased river levels were chiefly cyclone-infuced. (At 6 crucial monitoring points all 3 rivers were shown to be flowing at their highest levels for over 100 years.

The following facts shown the enormous scale of the flood:

• At its peak, almost 70% of the city was covered by floodwater.
• 2/3rds of the capital city, Dhaka was flooded, with most of the suburban areas being knee deep in water; raw sewage was observed floating on the surface of Dhaka's residential zones. The retreating flood water left behing pools of stagnant, contaminated water which represented a very serious health risk.
• 30-40 million people rendered homeless, the homes of a further 5 million were seriously damaged.
• Death toll - 1000+. 227 due to diarrhoea!
• Outbreaks of skin disease, jaundice, measles common where people had clustered together for long periods of time (food shelters)
• 1 million tonnes of wheat and 3 million tonnes of rice destroyed by flood water.
• 90% of the nation's stock of sweet potato seeds destroyed.
• 42,500 drunking water 'tube wells' had to be repaired.

Many measures were implemented to try and reduce the impact of future flood events. These included:

• Improving flood control + riverbank protection for Dhaka + other large urban areas.
• Improving flood forecasting + warning systems - including extending the national network of radar stations designed to monitor weather changes + transmit flood and cyclone warning systems.
• Improving disaster preparation facilities by building escape centres + roads on higher ground; also providing school buildings with some degree of flood prevention.
• Developing 'education in disaster preparedness' programmes in schools and adult communities.
• Increasing use of watershed management techniques, including:
  • Building dams to control river flow
  • Dredging river channels to increase their capacity
  • Extending afforestation schemes & encouraging valley farmers to terrace their land.