1. PART 2
G1.8- G1.10 PLUS CASE STUDIES

2. G1.8 river rejuvenation
Rejuvenating rivers form as a result of a fall in sea level, either as a result of an increase in ice storage or due to isostatic rise. Either way the result is a relative fall of sea level to land. Isostatic rise or rebound is caused by the landmass rising. Under these circumstances, the river will begin again to cut down vertically, starting from the mouth in an attempt to reach it new base level. The point at which the river is cutting down is called the knick point. This means that the river will now have features of the upper course again. The knick point is a sudden break or irregularity in a river long profile where gradient increases suddenly. They are generally easily recognised in the long profile as they are marked by a waterfall or series of rapids. However some knick points can go almost unnoticed. This process begins at sea level and begins to retreat back up the long profile. The knick point represents where the old long profile joins the new one.

3. River terraces
Once a river rejuvenates, due to a fall in its base level, the river will begin cut down. In doing so it leaves behind abandoned river terraces that mark the previous level of the floodplain. A river terrace is a remnant of a former flood plain which has been left at a higher after rejuvenation of the river. The river starts to cut into the valley creating another valley within the first on. If rejuvenation takes place again this process is again repeated. Terrace provide shelter from flooding as well as natural routes for roads and transport. The built up areas of London and Oxford are built on the Thames river terraces.

4. Incised meanders
If a rejuvenated river retreats to an area where there are already mature meanders the river will erode vertically as well as laterally at this point. This means that the meander will become deepened
Incised streams and rivers have cut deeply into the landscape. These landforms created is largely a result of the rate at which vertical erosion has taken place. When incision is slow and lateral erosion is occurring, an ingrown meander maybe produced. The valley becomes asymmetrical, with steep cliffs on the outer bends and more gentle slip offs with rapid incision where down cutting the valley is more symmetrical.
There are two types of incised meanders:
Entrenched meanders develop following a rapid incision of the river or when the valley sides are more resistant to erosion. Entrenched meanders have a symmetrical valley profile, e.g. River Wear, Durham.
Ingrown meanders occur when incision is slower and drawn out over a period of time. In this case the meander has time to erode both vertically and laterally to form an asymmetrical river valley, e.g . River Wye, Tinton Abbey.

5. G1.10 - The causes of flooding
Flooding- more water than usual in an area due to a river busting its banks to due to precipitation. Causes of Flooding:
Physical Causes
Human Causes
Excessive/ intensive precipitation
Urbanisation, roads, infrastructure. (bridges)
Snow melt
River management. Dams, channelisation
Climate hazards (hurricanes)
agriculture
Relief of land
Deforestation (trees can intercept runoff)
The nature of the drainage basin
Rock and soil type
Natural vegetation
G1.9 mid unit test G1.11 revision

6. G1.10 - Characteristics that result in floods
Both human and physical factors attribute to flooding.
Some of the physical cause include intensive or excessive precipitation, this increase in precipitation leads to saturated land which cannot take any more water therefore the land will flood because the water has nowhere to go it cannot infiltrate the ground. Another example of physical causes is snow melt, this again leads to waterlogged land meaning that yet again infiltration cannot occur. Therefore the water puddles and the puddles turn into floods. This type of flooding can occur in places such as the alps where there is a lot of snow melt in the spring.
Many human causes of flooding are because of urbanisation. This is because in urban areas there are lots of impermeable surfaces this means that percolation can’t occur. This happened in West Pulborough, Sussex where people built on the floodplain. Deforestation can also cause flooding this is because usually the trees intercept the runoff and surface flow from the precipitation however if the trees do not intercept the water this means that more water will get to the river but also it will get there quicker. In urban areas there are often drainage systems these will decrease flood risk with in the city however this may cause promblems further downstream as water is quickly transferred directly to the river this reduces the lag time. In many urban areas rivers have been narrowed or constricted in other ways for example the building of bridges. This affects the discharge of the river and can lead to a higher risk of flooding.

7. G1.10 – Responses to Flooding
Short term
Media broadcasts
Emergency relief, rescue, shelter, food.
Evacuation, emergency defences
Road closures
Long term
Government or foreign aid
Disaster planning for the future
Flood management schemes and programmes for the future.

8. G1.10 – Flooding case studies
MEDC – Southern Britain 2007
LEDC – Bangladesh 2004
Why did the flooding occur?
The jet stream which influences the path taken by low pressure systems in the north Atlantic had followed a southern track therefore the UK was getting more rain than usual. This meant that the high pressure associated with fine weather was not able to influence the British weather.
Rainfall totals for May to June 2007 were the highest for 241 years (1766, many areas registered over double of the long term rainfall expected for this time of year. On the 20th of July exceptional rainfall was recorded.
-145mm in Pershore, Worcestershire.
- 111mm in Chieveley, Berkshire.
-120mm in Oxfordshire.
Flood risk during the summer is usually lower due to dry conditions.
However during summer 2007 the rainfall had already been high and the ground was saturated. This meant there was little infiltration or percolation capacity.
These storms cause serve local flash flooding.
Bangladesh, which lies in the low land region of the deltas of 3 major rivers in Asia, the Ganges, the Brahmaputra, The Meghna. The sources of these rivers are in the Himalayas therefore snowmelt adds to their discharge during spring. Bangladesh has a monsoon season for May to September; this is when low pressure brings heavy persistent rain to the region. Bangladesh also suffers from cyclones during this time as well this leads to localised flooding as discharge from rivers increases as well. Urbanisation has also contributed to flooding in this area. As cities get bigger the water cannot infiltrate the soil. Deforestation has also lead to flooding as there are fewer trees to intercept the rain fall. This country is one of the poorest in the world ($300 GDP) therefore it relies on other countries to help it implement river management and control river floods. From late June to September 2004 the monsoon brought more rainfall than usual which resulted in all 3 rivers bursting there banks and widespread flooding across the country.

9. CASE STUDIES CONTINUED
MEDC –Southern Britain 2007
LEDC – Bangladesh 2004
When and where did the flooding occur?
Summer July - Southern Britain -Berkshire, Oxfordshire, Worcestershire, Warwickshire, Buckinghamshire, Gloucestershire, Somerset.
This map shows those areas affected by the summer floods of 2007 as you can see it was mainly south western midlands of the UK.
June – September 2004
Bangladesh, Asia

10. CASE STUDIES CONTINUED
MEDC –Southern Britain 2007
LEDC – Bangladesh 2004
What was the impact of the flooding?
Immediate:
1000’s stranded on M5
Power cuts homes
Loss of running water homes
still affected a week later
"biggest (rescue effort) in peacetime Britain"
Economic costs
£25 million damage to Gloucestershire’s roads
Up 50% of crops lost
£3 billion paid out in insurance
Similar amount lost due to uninsurance
£1 billion cost to the water industry
38% of land flooded (800,000 hectares of agricultural land as well as the capital city.
Nationwide, 36 million/125 million people were made homeless
Death toll- 800 (most due to disease and no access to clean water.)
Serious damage to infrastructure.
$2.2 billion cost
Poor less able to cope.
Environmental - river bank erosion, soil erosion, water logging, water contamination.

11. CASE STUDIES CONTINUED
MEDC –Southern Britain 2007
LEDC – Bangladesh 2004
What was the response to this flooding?
Prime Minister Gordon Brown promised £46 million in aid to flood-hit councils and £800 million rise in annual spending on flood protection by 2010–11, confirming Hilary Benn's announcement. Brown also pledged to push insurance firms to make payouts.
On 8 August 2007 Defra announced that Sir Michael Pitt would chair an independent review of the response to the flooding
Short term: Emergency relief (government and NGO) (rice, clothing, medicines, blankets and towels)
UN disaster management team.
Critical emergency supplies
Damage and needs assessment
Bilateral aid
Self-help schemes
Long term:
Dependant on foreign aid due to being an LEDC
In the past river management has proved inadequate
Small scale community schemes seem to be more effective.
Early warning systems and flood shelters have been put in place for the future.
Financial aid for 5 years

12. G1.10 Flood/River Management
Flood Management Strategies
Flood management strategies seek to reduce the effects of flooding on the human environment. Approaches toward flood management vary from enormous engineering projects such as modifying river channels on the Mississippi, to protecting buildings from flood damage as implemented on the river Ouse in York.
The main strategies can be grouped into hard engineering methods and soft engineering methods.
Hard engineering is a man made usually more expensive method where the channel of the river is changed significantly whereas soft engineering works with the natural process of the river.
Flood warnings
Case studies - Hard - Soft

13. Hard Engineering
Flood walls, these are designed to increase the height of the channel to stop water spilling out onto the floodplain. These are mostly used in towns and cities where there is restricted access to land to provide floodplains.
Embankments are often made of earth with rubble fill and are more common outside of urban area, this is because in more rural areas there is more room to change the channel, and this means that embankments can be set back from the original river channel making the new channel deeper and wider. This means that the water is contained within the new channel width and therefore it continues downstream instead of flooding this area.
Levees can be artificially enhanced or introduced to raise the level of the river bank; this will stop the water from overflowing and flooding the bank.

14. Hard Engineering
Dams: These are widely used to regulate the flow of water during high rainfall. The extra water can be stored in the reservoir created by the dam. It can then be released slowly during low- flow conditions. This can allow a steady flow of water all year round. However dams can be expensive to build and also require a lot of space as some of the valley may have to be flooded.
River straightening (channelisation):
This leads to a higher velocity within the river; this means that the flow downstream is quicker this leads to a short lag time and therefore less likeliness of flooding. This is because the water is not stuck in an area but flows quickly away from it. This means flash flooding and further flooding downstream is more common though it prevents long term flooding, as water quickly travels away. Sometimes it is created by using very unnatural looking banks and river beds made of concrete which also speeds up the flow of the river. This is called channelisation.
Diversion: (bypass)
another options is to construct a second channel to divert the channel from built up places during high flow periods. Much like with roads when a bypass is constructed to relieve traffic in a town centre. During high flow periods sluice gates are opened this allows the water to flow into the bypass channel. This relieves pressure on the original channel. However in most places the flow has to be permanently controlled by sluice gates to avoid the channel being abandoned by the river.

15. SOFT Engineering Planting trees:
Afforestation programmes in upland areas increase interception and slow down the water transfer. The trees also take up water for their growth. Thus both of these reduce the amount of water that gets to the river.
Wetlands:
Environments on floodplains are important for storing water. They are also important habitats for wildlife. Increasingly such areas that have previously been drained are being returned to their natural state of wetlands and marshes.
Riverbank conservation:
this involves stabilising riverbanks to prevent their erosion and collapse and the subsequent silting up of the river channel, this over course slows down the velocity and can lead to flooding as well as the channel is made smaller. This often involves planting vegetation, like bushes and trees, the roots of which bind together the loose sediment forming the banks.
Floodplain use and zoning:
careful planning can reduce the risk of flooding to the human environment. Areas that are close to the river can be left and not developed on meaning that these areas can be used for farming and green spaces as well as reaction. This means that if flooding should occur it doesn’t affect expensive developments such as towns.
River Restoration:
Involves returning a river that has been altered to its original state. If left alone rivers will flood but usually this is small scale flooding. The natural process and features of a river such as meanders and wetlands work to slow down river flow this reduces the risk of a major flood. River restoration often involves introducing meanders to a river that may have been artificially straightened. An example of this is the River Skerne in Darlington; here a 2km stretch of the river has been restored to create wetlands and meanders. This river had been straightened for 200 years and was a polluted river, now it has been restored it has a better environment and is home to wildlife. This river was used as a demonstration project by the River Restoration Centre.

16. FLOOD WARNINGS
Throughout the UK, rivers and flood basins are monitored by the Environment Agency; this means that they can issue warnings from their observations to alert the public that flooding is possible. There are 3 warnings issued by the environment agency.
Flood Watch(alert) - low land and low lying roads are expected to flood. The public is asked to prepare.
Flood Warning – means that there is a threat to homes and businesses. People are urged to move high value items to high places and to switch off services such as electricity and water. Evacuation is possible.
Severe Flood Warning – means that extreme danger to life and to property is expected. People urged to seek safety or evacuate.
Shown on the next slide are flood warnings from Jan 2014

17. Flood Warnings
03/01/
Met Office/ Environment agency

18. Flood Warnings
03/01/

19. Flood Management Case Studies
Hard –engineering:
MEDC – UK- Cumbria – Carlisle
in 2005 a prolonged spell of rain caused the river Eden to burst its banks, this lead to two people being killed as well as 1700 properties being affected by the flood. Large parts of the city were evacuated. Damage costing £500 million was caused.
As a result of the flood the environment agency implemented a two phase plan to combat future flood threats to Carlisle.
Phase 1: In 2008 a 4.5km stretch of raised flood defences like walls and embankments was completed along the River Eden and the River Petteril. These defences cost £13 million and protected properties.
Phase 2: In 2010 a further 5km stretch of flood defences was completed costing £25 million. These defences focused on the River Caldew and protected a further properties. A new pumping station was also installed.
During 2009 phase 1 came to the test and the environment agency successfully managed to protect Carlisle from a flood that affected much of the surrounding area. By using temporary defences Carlisle was kept safe.
In addition some soft engineering strategies have also been implemented in Carlisle. For example creating more space for flood plains downstream, as well as cleared channels to prevent blockages and raised footbridges.

20. Flood Management Case studies
SOFT Engineering – Case Study – river restoration.
The river Quaggy runs through southeast London. Since 1960 it has been heavily managed and artificial channels and culverts were built to divert it beneath the ground surface as it passed through Greenwich. As a result of increased flood risk due to continued development in Lewisham and Greenwich, more needed to be done to protect the area from further flooding. Hard engineering was considered, such as further widening and deepening of the existing channel. But instead the environment agency decided to implement a soft engineering program. This solution was proposed by local residents who formed the Quaggy Waterways Action Group (QWAG) who implemented the new more environmentally friendly soft engineering scheme. The plan was for the river to be brought above ground again to create a multi functional space in Sutcliffe Park. A new lake was created to store water and some water is still diverted underwater in flood conditions. The park has a flood storage capacity, this means that in a flood the park will take a lot of the water before it overflows and floods the surrounding towns. This strategy has lead to numerous awards being given to QWAG.

21. QUICK RECAP ON FLOOD MANAGEMENT

22. G1.10 Flood management (COST) (ft. AMY LINFORD)
Method
description
Picture
Cost
Advantages
Disadvantages
Dams and reservoirs
Widely used to regulate flow of water by Storing water then slowly releases it over a period of time.
Example in China Yangtze River cost £25 billion to build in 2006.
Can be used for multiple purposes such as irrigation and hydroelectricity.
By producing a regulated flow, there is a constant supply of water downstream all year round.
Cause flooding to upstream areas. People have to be relocated. Harmful to wildlife habitats such as the white flag dolphin in China.
Requires dredging.
Causes more erosion downstream.
Afforestation needed on slopes.
Increased likelihood of landslides.
Artificial embankment
Material dredged from the river bed, placed on the river bank to increase the height. Often reinforced by a concrete wall.
Relatively cheap as it uses resources already there in the area, which have been produced from the erosion caused by the river.
Use of resources already there.
The river can hold a greater volume of water.
Prevents flooding.
Ruins the picturesque landscapes.
Potential of riverbank collapse.
Concrete walls can destroy wildlife habitats.
Prevent flood water drain back into the rivers.

23. HARD
Flood walls
Concrete structures that increase height of channels to prevent rivers bursting their banks.
Expensive due to cost of concrete.
Prevents flooding.
Used in urban areas as it doesn’t take up too much space.
Expensive to build. Cause flooding further downstream.
Disruption of the rivers natural flow. Prevents water from getting back to river.
Diversion Channels and spillways
Channels formed to serve as an overflow within the rivers cause.
Expensive due to the construction of a new channel.
Holds higher volumes of water.
Water can be diverted from a town so that flooding doesn’t occur.
Maintains a natural look to the river.
It’s expensive to build.
If it’s not controlled correctly, It can dry up the main channel.
Channelisation
River channel is lined by concrete to prevent flooding and the collapse of river banks.
Higher velocity due to less erosion. A shorter lag time meaning flooding is less likely.
Can create flooding further downstream.
It can increase flash flooding.

24. SOFT
Afforestation
Planting trees to increase interception and slow down water transfer. Thus reducing the amount of water in the river.
Fairly cheap.
Creates a natural look to the river.
Doesn’t interrupt the rivers natural course.
Add stability to the land.
Takes a long time to grow so the effects aren’t immediate.
Have to plant a large number of trees to reduce discharge downstream.
wetlands
These environments store water on the flood plains.
Cheap.
Water is stored in the floodplain and not in the river itself which reduced flooding.
Encourage species diversity as it doesn’t affect the natural course of the river.
The wetlands creates an environment in which reed beds, meadows and trees grow.
River bank conservation
This involves stabilising the riverbank to prevent erosion and collapse. This means that it stops the river channel silting up.
Reduces flooding by increasing river flow. Cheap.
Involves vegetation by which the roots bind together the loose sediment forming the banks.
It doesn’t last for very long as problems can occur meaning it has to be rebuilt.

25. SOFT Floodplain use and zoning
Creating areas of the flood plain that are suitable to flood.
cheap
Areas closer to the river can then be used for farming and houses can be built further away.
Ensures that any damage done due to flooding will be minimal.
Doesn’t affect the rivers natural process.
Takes up a lot of space that can be used for other things.
River restoration
Returning a river that has had modifications to its natural state.
Waste of money as it’s removing the flood managements already put in place.
Aims to put the river back into its natural form.
Occasional flooding is beneficial to the soil.
Has negative effects of social and economic issues.
Doesn’t prevent flooding as its relying on floodplains.
Flood forecasting and warnings
Throughout the UK, rivers and flood basins are monitored by the environmental agency.
Expensive as the equipment is very high tech.
Issue warnings to alert people to the risks of flooding.
Prevents risks to people.
Doesn’t prevent flooding actually happening.