1. Human Causes Natural Causes
Population growing causing cultivation to increase
1971 – 75 million
150 million people now in 140,000 sq km – is now the most densely populated country in the world
Resource depletion –
Wood – cooking, building,
Trees – removed – deforestation – lack of interception, transpiration
Flash Floods
More Silt from Nepal and China in rivers – Aggradation
Discharge capacity reduced
-Dhaka population increased
More impermeable surface
-increase surface run off
Houses built on marginal land
Belt of onshore winds travel around the globe and reach Bangladesh each year bring monsoons May and Sept
Located 10N of Equator therefore prone to tropical cyclones due to warm sea surface temperatures 26.5 and above and Coriolis Force
Whole country virtually a river basin to one of the largest rivers on earth and a flood plain for the Himalayas
3 great rivers meet (confluence) 1.7 million sq km drainage basin
7 times bigger than the UK
Large drainage basin
Less than 0.5 metres above sea level
Floods frequently
Glacial retreat
Global warming
Sea level rise 1m by end of this century
Venn Diagram – Human and Natural Causes of Flooding in Bangladesh

2. River Ganges flooding in Bangladesh – 1998, Case Study
Economic effects
No work in the rainy season so need to find other ways to provide for family – migrate to Dhaka in search of work – manual, low-paid jobs, some stay in shanty towns
Less taxes paid – government little money for schools/hospitals and very little for flood protection
Flooding each year costs between 3 – 10% GDP
River Ganges flooding in Bangladesh – 1998, Case Study
Location & Description – Asia, surrounded by India, south of the Himalayas, north of the Bay of Bengal, 3 major rivers – Ganges, Brahmaputra & Meghna, rivers total. Very flat land
Environmental effects
670,000 hectares crops destroyed
River channels move in flooding – farmers loose land
New islands called Chars (made from sand and silt) can be used for farming, people start living there BUT easily disappear in a flood
Animals die
Human causes of flooding
Growing population so cultivating land that usually floods, 1971 – 75 million, 2008 – 150 millions, most densely populated country in the world
Deforestation – need for wood for cooking and building so water not intercepted or stored in trees gets to river quicker
Changing agricultural (farming) practices - other countries, Nepal putting more silt into rivers so they fill up quicker and can’t hold as much water – aggradation
Urbanisation – more people = more concrete
Global warming – higher sea levels so water trying to run out meets higher tides coming in = more flooding, glaciers in Himalayas melting run into rivers.
Social effects
Loose homes and land – have to move
Families split – men go to work in Dhaka
1000 killed
30,000 homeless
50 million below poverty line can’t protect themselves, hard to recover, live on marginal land prone to flooding
Aid – NGOs. Emergency aid – food. Water, cluster villages, flood shelters, small loans for businesses
Solutions – hard engineering aims to stop floods reduce impacts, expensive, take up space, build embankments = more water in river, need constant repairs, new channels, underground drains & pumping stations
Natural causes of flooding
1) Monsoon rains – brought by on-shore winds , May – Sept each year, up to 1metre can fall in a day.
2)Tropical cyclones bring rain
3) Huge Drainage Basin , 12 times size of Bangladesh- snow melt from Himalayas, 3 great rivers, Bangladesh is one huge flood plain,
4) Flat land – 50% plus is less than 12 metres above sea level.
Solutions – Strengthening livelihoods – helping to carry on earning during flooding
Practical Action – cluster villages, built on raised land so won;t flood, shared facilities, tube well, toilets, gardens/land to grow food - sustainable
Moshiur’s Pumpkins – built on sandy land that no-one wants, sand-bar cropping, appropriate technology – doesn’t need fertilizers or machines, pumpkins grow in sandy soil their growing cycle fits with the annual floods, easily stored so eaten or sold for high price in flood time, result – food, water pump, buy goats, more land
Faruk’s Fish – money from Practical action, raises fish in cages, flooding just moves the cages, free training and small loan to buy cage – expanding next year, improve home, send children to school
Noor’s Super Ducks – ducks can survive in the floods, provides continuous income