Rivers: Floods (Sheffield Flood Effects** (people were air lifted from…
Sheffield Flood Effects**
The floods caused an estimated £1billion of damage.
3 people died
1000 businesses collapsed
people were air lifted from their homes
48000 homes effected
cost businesses between £75000-112000
1200 homes flooded
River Don burst it's banks causing pollution and sediment to be washed across many areas
Causes of the Sheffield Flood
Rained a lot three moths prior making the ground already saturated
1 moths worth of rainfall occurred in 2 days
lots of building on floodplains making impermeable surfaces resulting in a shorter lag time and flash flooding
5 rivers flow through Sheffield
river don broke its banks
Sheffield is steep slopped, can result in shorter lag times
One of the most low lying areas in the country.
Urbanisation- lots of impermeable surfaces
Deforestation to make way for buildings
Floodplain of River Don had houses and industry built on it causing more infrastructure at risk of economic damage and no natural storage for floodwaters
Drains were only built to withstand small floods and could not cope
: The highest discharge of the time you are looking at.
The delay between peak rainfall and peak discharge.
: The increase in river discharge as rain water flows into the river.
The decrease in river discharge as the river returns to its normal level.
River Management (Hard Engineering)
Flood walls are artificial barriers built along river banks, allowing the river channel to hold more water. Flood walls are very expensive and they can block the view of the river.
High banks that are built along or near the river banks. They stop the river flowing into built up areas during a flood, protecting buildings and infrastructure. They can be made from earth or other natural materials making them less unsightly. They are relatively expensive to build and there's a risk of severe flooding if the water rises above the level of it or if it breaks.
Built on river estuaries to stop flooding from storm surges or high tides. They can be shut when there's a surge forecast to prevent flooding and they protect large areas of land. They are very expensive and need to be maintained regularly.
Flood Barriers (Demountable)
Provide temporary protection against flooding. They are only put up when there's a flood forecast so there's always a risk they might not be in time. They are quite expensive to build but they don't spoil the view.
River Management (Soft Engineering)
Flood Plain Retention
Maintaining the river's flood plain for example by not building on it. It helps slow floodwaters down and maintain the flood plain's ability to store water. It doesn't cost anything but it restricts development and can't be used in urban areas.
Making the river more natural for example by removing human made levees so that the flood plain can flood naturally. It decreases the risk of flooding downstream because discharge is reduced. The river is left in its natural state therefore little maintenance is needed. However it can increase local flood risk especially if there is nothing preventing major floods.
High level winds at about 6-10km altitude in the atmosphere.