To start… Recap Thames and Mekong case studies. Why are there conflicts in the development of river basins?

What issues arise from the development of river basins?

Lesson Objectives: By the end of the lesson you will be able to: Appreciate how rivers are used and why the dependency of rivers alters between MEDCs and LEDCs. Identify the issues that arise from the development of river basins. Explain how these issues can have social, environmental and economic causes and effects.

Factors that promote flooding… Areas of intense convectional rainfall. Prolonged heavy rainfall. Seasonal snow melt. Small basins ion which run-off is rapid. Steep slopes which lead to rapid and overland flow. Areas where the natural vegetation has been replaced. Basins with large areas of impermeable surfaces due to urbanisation and industrial development.

Natural causes of flooding

Human causes of flooding…

Case Study: 2007 UK Floods

Facts and Figures… The torrential downpours in July 2007 were officially the worst for 200 years. Rainfall was more than double the seasonal average. Gloucestershire and neighbouring areas experienced more than 320% more rainfall than the average for the previous 3 decades. Over 140000 people were without water for ten days when the river Mythe water treatment plant was damaged.

Natural causes of the floods? The unusual position of the jet stream has been blamed for the bad weather. It normally lies over the North Atlantic holding back the bad weather while allowing warm weather in from Europe. But it moved several hundred miles south, possibly due to La Nina event, which occurs when cool water surges from the bottom of the Pacific and cools the air above.

Causes of the UK 2007 floods

Effects of UK floods 2007 – highlight the economic effects orange, social effects blue and the environmental effects green.

To what extent are people the victims and or the causes of floods in the UK?

Flooding in an LEDC: Bangladesh Flooding is common in Bangladesh due to a number of natural and human factors.

Natural causes of flooding More than half the country is less than 5m above sea level. Total rainfall in the Brahmaputra-Ganges-Meghna catchment is very high and seasonal. 75% annual rainfall occurs in the monsoon between June and September. Area also subject to coastal flooding and storm surges.

Human causes of flooding Bangladesh is very densely populated – over 900 people per km. It is experiencing rapid population growth – contains nearly twice as many people as UK in half the space. Low-lying flat delta vital for place to grow food and place to live. ¾ population live within the delta. Deforestation – removal of trees in Himalayan uplands led to mover overland flow and less infiltration on water. River diversion – River Ganges has been diverted for irrigation purposes.

Fresh water wells – in 1980s more than 100 000 tube wells and 20 000 deep wells were built to provide drinking water. They have reduced the water table. International Loans – government spends its money replaying debts rather than better flood protection. Lack of international investment – few companies willing to invest in long-term social projects that would help Bangladesh. Overseas pressure – government under pressure to invest in industry. Corruption – funds for flood protection may have been diverted. Floods are vital to Bangladesh to provide nutrients to the soil – but benefits have to be balanced with costs.

Causes of Floods

1998 floods 2/3 country submerged by water. Dhaka (capital) cut off. 23 million made homeless, 130 000 cattle killed, 660 000 hectares crops destroyed. Almost ¼ children under 5 were malnourished. In Dhaka the sewage system collapsed and drinking water contaminated – diarrhoea and dysentery affected many people. Incomes of two of country’s largest industries, textiles and shrimp production, were about 20% below normal. Roads damaged, 1000 schools destroyed. International Aid – 1 million tonnes food provided. World Heath Organisation launched appeal for medicine and purification tablets.

2007 floods 565 000 hectares of farmland and nore than 10 000 km of road were submerged. 300 people died. 7 million people affected by the floods. Estimated 300 000 moved into refugee camps.

Effects