Flashcards in Rivers, Floods and Management - Bangladesh Case Study Deck (55):
Frequency of major floods
Every 8 years
3 major rivers
Capital of Bangladesh
Population of Bangladesh's capital
Dhaka 1 million
How much rainfall fell in Bangladesh and when? This was the worst rain for how many years?
350mm in 24 hours
13th September 2004.
Worst rain for 50 years.
How much of Bangladesh is how far above sea level? Why?
20% less than 1 metre above sea level.
Because it is built on a floodplain on delta land.
Summary: 5 physical causes of Bangladesh flood
- Heavy rainfall
- Monsoon climate
- Low lying
- 3 major rivers
What system was put in place for farming? Which river? Effects?
Irrigation system to divert the Ganges.
Reduced speed of flow in channels = more deposition inland, less on low lying delta = didn't build up
Name 2 places where urban growth occurred
Nepal and Tibet
Summary: 4 human causes of flood
- Irrigation diverted Ganges
- Deforestation of Himalayas
- Global warming
How much of the country was flooded?
How much of Dhaka was under water and in which month?
40% under water in July
How many bridges destroyed?
How much road damaged?
How much farmland destroyed?
How many people suffered from diarrhoea in Dhaka?
Cost of total damage?
2 other long term impacts
Rice crops devastated = food shortages
Jute and sugar cash crops rotted = money shortages
How much aid did the UK give?
How much aid did the UN appeal for? How much did they actually get?
Appealed for $74 million.
Only got 20% by September
What charity gave Bangladesh short term aid?
Water aid - water purification tablets
2 other short term responses
- NGOs: rice, clothing, medicine, blankets
- Farmers given free seed
9 long term responses
- Flood action plan formed
- Early warning system
- sluice gates
- 2 ha of raised land for flood shelter
- Coastal homes on stilts
- homes raised by 2m on earth banks
- Embankments strengthened
- Self help schemes: rebuilt homes & communities
- Additional financial aid granted
By how much were homes raised on earth banks?
How much raised land was created for flood shelter?
What economic factor limits Bangladesh's ability to manage floods?
GDP per capita = $700 and tax revenue limited = rely on foreign aid and NGOs
Why did heavy rainfall lead to flooding?
Groundwater stores filled = water table reached surface = surface runoff
When is the wet season?
May to September
What causes rain to coastal regions? How did this lead to floods?
Low pressure and winds fro southeast = heavy rain
Meghan reached peak level in July
What brings intense precipitation and storm surges?
Cyclones from Bay of Bengal
What area of Bangladesh is easily washed away by floodwater and why?
Densely populated island - Chars
Made up of mud deposits = unstable
How did Himalayas lead to flooding? 3 ways
1. Snow and glacial melt increase discharge of Ganges and Brahmaputra
2. Tectonic uplift = rivers have more GPE = more erosion = sediment deposited downstream which chokes channels
3. Relief rainfall - high slopes = faster and more runoff
Which glacier in himalayas contributed to flooding and how?
Gangotri Glacier in Indian Himalayas feeds ganges. Melts at 25m per year.
what type of causes have become more important in recent decades?
Human causes of flooding
Where did deforestation occur and why?
In Himalayas due to pop pressure in Nepal and Tibet - need more grazing land and wood for fuel
How did deforestation contribute to flooding?
Less interception and evapotranspiration = more runoff
Soil erosion = river bed aggradation = reduced capacity
How did urbanisation contribute to flooding?
Impermeable surfaces = more runoff and less infiltration = discharge increased, lag time decreased.
Increased magnitude and frequency of flooding.
How did global warming contribute to flooding?
- More extreme weather = increased quantity and intensity of monsoon rain
- Higher temp = more snow melt
By how much is rainfall estimated to increase due to global warming and by when?
10-15% increase by 2030
How much rice was destroyed?
2 million tonnes
Who lost their livelihoods?
What infrastructure was damaged?
Railways, roads, embankments, irrigation system
What groups of people were most affected?
Poor farmers, landless labourers and slum dwellers
How many people homeless?
36 million (25% population)
How much untreated sewage escaped into water each day?
500,000 cubic meters
5 environmental impacts of flooding
1. Land flooded
2. River bank erosion on embankments near main channels
3. Soil erosion
4. Waterlogged urban areas
5. Water Contamination
Describe early warning system put in place
- Satellite monitoring linked to local radio stations to send warnings
- warnings from loudspeakers in Mosques
Who and for how long was financial aid granted?
5 year period
- World bank loan to paid for infrastructure repairs, water resources management and education
What dates did Bangladesh have catastrophic flooding again?
2007 and 2010
Why is Bangladesh under greater threat?
Sea level rise and more storm surges
Climate change made cyclones more powerful = higher storm surges
How much is temp supposed to rise Bay of Bengal?
2- 4 degrees next 40 years