There are two ways of managing floods to reduce their impact
Soft engineering and hard engineering (same as with coasts)
It is a balance of how valuable the land is, how many people will be affected, how costly the management scheme is, and how effective + sustainable the management scheme will be
River management: Hard + Soft Engineering Now highlight, in different colours, the advantages and disadvantages of each scheme Hard Engineering Soft Engineering Dams Washlands Embankments Land-use zoning Flood Walls Afforestation Straightening and deepening the river Warning systems Storage areas
These are traditional methods of stopping floods and require complicated engineering.
The Environment Agency has three options available:
1. build flood defences like dams, embankments and flood walls
2. straighten and deepen the river and cut off meanders
3. make storage areas for extra water.
These trap and store water so reduce surface runoff as water is realeased in a controlled way.
The land upstream of the dam is flooded, this can change ecosystems and mean that local residents may have to move out of the area.
The reservoir lake can be used for recreation e.g. fishing
Dams trap sediment behind them that would normally flow downstream. This can cause problems where farmers rely on silt providing fertile soil after flood events e.g. The River Nile
Dams are very expensive but effective .
These are raised banks along the river, they effectively make the river deeper so it can hold more water before it floods.
They are very expensive and do not last long (unsustainable).
Rivers can now flood without causing much damage.
Embankments are also built near settlements with washlands between the embankments and the river.
Flood walls are built around settlements and important factories or roads. They're quite expensive and don't look very natural. These are very effective at stopping flooding. Flood walls are also used in
places where there are
a lot of people living.
Straightening and deepening the river
This is when the river is made straighter to make the river flow and channel flow faster so there is less chance of river flooding.
It keeps the water levels to a minimum so it is less likely to flood.
We can use it to make high levels of electricity.
It is very expensive to dig out and straighten the whole river, especially if it is a very long river.
The result is often not natural looking.
Water can be pumped out of the river and stored in temporary lakes.
Then it is pumped back in after the water in the river has gone down a bit.
Effective but we do
need to have a large
area of free land that
isn't used, so that
you can flood it.
Soft engineering techniques work with the river and use natural processes.
These are parts of the floodplain that are allowed to flood.They can't be built on. They're usually used for sports pitches or nature reserves.
This is where the land has different building controls depending on how far from the river the buildings lie. The land next to the river is un-used land and as the distance from the river increases so does the quality and the value of land rises. Important factories, schools, and most homes should be away from the river.
Afforestation is the deliberate and planned planting of various greenery (more specifically trees).
By doing this you can increase interception and prevent the ground from becoming saturated with water.
However, doing this takes up a lot of room and cannot prevent serious flooding.
Warnings are issued by the Environment Agency so that local people can put sand bags by their homes, take furniture upstairs, or even evacuate the area.
People do not always listen to warning systems.
Warnings are given on tv, radio and the internet.
River flood example
Example video of the Mozambique floods
If you want that higher grade, take notes….it is your case study after all
Read through the information on the choices of management schemes
You need two different colours of paper. On one piece, make notes on the River Derwent – the hard and soft engineering here. On the other colour, make notes on how the River Limpopo/Zambesi in Mozambique is managed.
This has now created a revision sheet for you.
Comparing Flood control in MEDC's and LEDCs
MEDC - North Yorkshire, River Derwent
MEDC river = has money to build defences (e.g. embankments, sluice gates,, washlands, land-use zoning)
Since the flood, £7.5 million has been spent on protecting towns
Sluice gates upstream can hold back water and let it out in a controlled way.
LEDC – Mozambique, Limpopo / Zambezi River
LEDC river = does not have the money to build defences
Money has been given to Mozambique by other countries to help recover in the short term
Cannot afford to have flood defences / prediction
Homework over holidays
Make sure you have caught up on everything.
Rivers + Coasts are now finished
You need to make sure you have got your case studies completed, that you understand the keywords, that you know + can explain landforms/changes in coasts+rivers, and flood hydrographs
Make a log/journal over the holiday to show what work you have done (e.g. 17 th Feb, completed Mozambique case study).
Please start using the blog. It is not there just for fun, it is your reference point. Every lesson is on there plus links to the exam board. There is a checklist of all you should know.
Describe the flood defences in the photograph (1)
Explain how these defences protect against river flooding (2)
Hard and Soft Engineering
Use the words below to complete this paragraph.
Hard engineering techniques are that are imposed on the river. They try to the river. Examples of hard engineering are and . Soft engineering started to be used in the 1990s. Soft engineering methods work with the river and use processes. Examples include and .
dams structures natural afforestation flood walls land-use zoning control
Exam Q: Responses to flooding
Evaluate two methods of protecting against the effects of river flooding. (4)
For 4 marks, you need to name 2 different methods and give 2 explanations . Evaluate means give the pros + cons.
Positive, e.g. effective, control water flow
Negative, e.g. expensive, ugly
Positive, e.g. sustainable, cheap, warn people to prepare
Negative, e.g. does not stop flood, may be ignored, needs technology
Exam Q practice
2. Explain why flood defences are more effective in MEDCs than LEDCs? (4)
For 4 marks, you need to make 2 basic points and develop these with 2 explanations .
Countries like Mozambique have low GDP (less money) SO they cannot afford to have flood defences.
LEDCs have to prioritise in developing basic services like hospitals and schools INSTEAD of flood protection.
MEDCs often have BETTER prepared emergency services and flood plans.
MEDCs have strict planning controls that prevent developers building on high risk areas WHEREAS these controls are not effective in many LEDCs.
Foundation exam paper (so highest grade = C)
Marked out of 25.
C = 17+
D = 14+
E = 11+
F = 8+
G = 4 +
Exam question feedback
Exam question feedback
River Terminology Test
You are going to be shown 10 words.
For each one, write the correct definition.
5. Groundwater flow
10. River basin
The scratching and scraping of the river bed and banks by the stones and sand in the river
2. Afforestation The replanting of trees
3. Delta A flat area at the mouth of a river made of sediment deposited by the river
4. Floodplain Flat land around a river that gets flooded when the river overflows
5. Groundwater flow The flow of water through underground rock
6. Impermeable Doesn’t let water through e.g. tarmac
7. Infiltration The soaking of water into the ground
8. Interception The capture of rainwater by leaves
9. Transpiration The evaporation of water from leaves
10. River basin The area drained by a river, the edge of which is marked by its watershed
Update your checklist sheet in your book
Make a note of the areas you feel you still need to learn more about (e.g. I’m a bit unsure about the hydrological cycle)