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.