Rivers, flooding case study LEDC Bangladesh

Bangladesh, Brahmaputra flood 1997

Causes:

Physical

1. Steep release form the Himalayas increase surface runoff.

2. Spring ice melt in the Himalayas increase discharge.

3. 70% of Dhaka is less than 1m above sea level.

4. Heavy monsoon rains in summer, 3000mm of rainwater in 4 months.

5. Confluence of 3 major international rivers, (Brahmaputra, Ganges, Meghra) so sudden increase in discharge.

6. Cyclones in Bay of Bengal stop floodwater escaping.

Human

1. Deforestation in Nepal so less interception, more surface runoff.

2. Urbanisation, e.g. Dhaka, less infiltration, more surface runoff.

3. Global warming means more cyclones and heavier rain.

Effects:

Social (short term)

-Immediate death toll 400

-Loss of cattle, poultry, belongings and plants swept away

-17% household trees lost

-15% poultry lost

-40 million people homeless

Environmental (short term)

-High tides, landslides, (farm)land eroded, dam destroyed

-Dhaka was 2m underwater

-floodwaters double normal levels, 137cm compared to an average of 73cm

-57% of Bangladesh flooded

Social (long term)

-Derivative, water borne diseases e.g.…