GEOGRAPHY YEAR 10: RIVERS AND FLOODING. Contains: river floods, factors to increase flooding, human factors, storm hydrographs, Boscastle 2004, Bangladesh 2007, the red mud in Hungary 2010.

1. YEAR 10 GEOGRAPHY
RIVERS AND WATER
8. RIVERS AND FLOODING

2. A river floods when the water normally flowing in the
channel overflows its banks and spreads out onto the
surrounding land.
This causes major problems for people living close to the
river.

3. A variety of factors can increase the likelihood of flooding.
Physical causes of flooding:
• heavy rainfall
• long periods of rain
• snowmelt
• steep slopes
• impermeable rock (doesn't allow water through)
• very wet, saturated soils
• compacted or dry soil

5. Human factors increasing flood risk:
• urbanisation, because towns and cities have more
impermeable surfaces
• deforestation, because removing trees reduces the amount
of water intercepted and increases run-off

6. A storm hydrograph is a graph to show how and when a
rainfall event affects the discharge of a river.

8. The amount and intensity of the rainfall is not the only factor
influencing the shape of the hydrograph.
There are other influences.

10. Boscastle is a small coastal settlement in the south west of
England.
It flooded in August 2004, washing cars and buildings into
the sea and putting peoples' lives in danger.

12. Heavy localised rainfall - 89 mm of rain fell in an hour.
Saturated ground from previous rainfall.
Topography of the land. The landscape upstream of Boscastle, a steep-
sided valley, acted as a funnel directing vast volumes of water into the
village.
Narrow river channels in the village itself.

13. £4.5 million has been spent on a flood defence scheme.
The scheme stretches along the valley, incorporating
drainage, sewerage systems and land re-grading.
Boscastle car park has been raised in height, which will stop
the river from bursting its banks so easily.
New drains allow water to run into the lower section of the
river quickly.
The river channel has been made deeper and wider so that it
can accommodate more water.

14. Bangladesh is a developing country in Asia and it is
frequently affected by flooding.
For example, in 2007 flooding made 9 million people
homeless and approximately 1,000 people died from
drowning and from waterborne diseases.

16. Cyclones cause coastal flooding.
Lots of low-lying land.
Melt water from the Himalayas.
Heavy deforestation.
Heavy monsoon rains.
Increasing urban areas.

17. Bangladesh is a very poor country and so has less money to
spend on flood defences than richer countries.
Most people in Bangladesh do not earn enough to pay for
insurance against flooding, so when there are floods they
risk losing everything.

18. Food aid from the Government and other countries.
Water purification tablets.
People repaired embankments and helped to rescue people.
Free seed given to farmers.

19. Building embankments.
Building raised flood shelters.
Introducing flood warning systems.
Emergency planning.
Dams planned.
Reducing deforestation.
Unfortunately, many of these long-term responses are
difficult to pay for and maintain.
They are not always successful and don't always help enough
people.

20. In October 2010, a large river of toxic red mud flowed through
areas of Hungary.
The mudflow was two metres high and covered an area 40 sq
km.
One million cubic metres of industrial waste was released into
the area.

22. The dam collapsed because of high rainfall.
The reservoir contained industrial waste material stored from
a nearby bauxite factory.
The factory producing the waste may not have been properly
maintained.

23. Nine people died, 120 were injured.
The chemicals released into the water killed fish and other
wildlife.
The pH level of the mud was high enough to cause chemical
burns.
Seven towns and around 7,000 people were affected.
The topsoil in agricultural areas was left contaminated.