Learn about the physical and human causes that can result in rivers flooding.

When a river carries too much water to be contained by the river bank, it floods the local area. There are a number of reasons why rivers can flood. Sometimes it rains harder or for longer than is usual; sometimes there is heavy snowfall followed by a sudden thaw, leading to huge amounts of water to be released. This can cause huge damage and loss of life, especially when the flooding occurs unexpectedly – some rivers flood every year and locals are prepared for it happening.

Human activity is sometimes a cause of flooding. Houses and roads are sometimes built on flood plains; as concrete and tarmac are impermeable the water cannot sink. Deforestation is another cause – trees and vegetation provide a natural barrier to water, and trees also prevent rain reaching the ground so fast.

Most scientists agree that flooding is on the increase, but there is disagreement over who or what is to ‘blame’: global warming, the earth’s natural cycle, deforestation, or simply the fact that more people live beside rivers.

The UK has experienced an increase in the amount of flooding over the last twenty years. Some of the most serious examples include:

2009, Cumbria: flood waters rose by up to 2.4 metres (8 feet).

2007, Yorkshire: a month’s worth of rain fell in just 18 hours in Sheffield.

2004, Cornwall: the Boscastle flood inundated the town on 16 August, causing great damage but no loss of life.

Although the UK suffers from flooding, partly due to its climate and partly because of the high population density, there have been few floods in recent years that caused high loss of life. However in the 1952 flood in Lynmouth, North Devon, 34 people drowned.

The effects of and responses to floods vary between rich parts of the world and poor areas.

Although serious flooding does occur in the developed world, generally speaking floods cause much greater damage in poorer countries like Bangladesh. This is partly because much larger numbers of people live in very close proximity to water, and because the housing quality is so poor that homes are easily washed away.

River Management Issues

What are the economic, social and environmental issues around managing rivers to provide a sustainable supply of water?

Of course rivers don’t only bring floodwater; they provide water, for people, for crops, for livestock and for industry. Mankind can survive without many things; but one resource no-one on earth can survive without is water.

Even in the UK – a country with a relatively high rainfall – water is a finite resource and its use has to be carefully controlled. For instance, there is usually much higher rainfall in the north, but there is much greater population in the south; this can lead to water shortages. It has been suggested that the UK needs a water network, which would operate in the same way as the power or telephone network: water from the north could be piped to the south and there would be no shortages. However, this would be very expensive, and a great deal of water is already lost due to leaking pipes.