Physical factors of flooding
- Prolonged rainfall
- Heavy rainfall
- Snowmelt
- Relief
Human factors of flooding
- Deforestation
- Building construction
Flooding - Prolonged rainfall
After a long period of rain -> soil is saturated -> further rain cant infiltrate -> INCREASES surface runoff -> Discharge is increased quickly -> Flood
Flooding - Heavy rainfall
Heavy rain -> Lot of runoff -> INCREASES discharge quickly -> Flood
Flooding - Snowmelt
Snow or ice melts -> Lots of water into a river in a SHORT space of time -> INCREASES discharge quickly -> Flood
Flooding - Relief
River is in the steep- sided valley -> Water reaches the channel quicker (water flows quicker) -> Discharge INCREASES quickly -> Flood
Flooding - Deforestation
Cutting down trees stops interception of water
- > Increases the volume of water reaching the channel
- > INCREASES discharge
- > Flood
Flooding - Building construction
Buildings -> impermeable materials
- > INCREASES surface runoff (drains quickly take runoff to rivers)
- > INCREASES discharge
- > Flood
Examples of Hard engineering
- Dams and reservoirs
- Channel straightening
Examples of Soft engineering
- Flood warnings
- Preparation
- Flood plain and zoning
- ‘Don nothing’
Hard engineering definition
Man- made structures built to control the flow of rivers and reduce flooding
Soft engineering definition
Schemes set up to using knowledge of a river and it processes to reduce the effects of flooding
Dams and reservoirs
Walls are built across river upper course lake is formed behind the dam
+ Store water -> reduces flooding
+ Used a drinking water
+ Used for hydroelectric power stations
- Very expensive
- Flood existing settlements
- Eroded material is deposited in the reservoir not the natural course (farmland is less fertile)
Channel Straightening
Course is straightened (meanders are cut out by building straight channels)
+ Water moves out area quicker ( doesn’t travel as far)
- Flooding may happen down stream
- More erosion down stream - flowing faster
Flood warnings
Environment agency warms people \+ Impact is reduced \+ Gives people time to more possessions upstairs - Doesn't stop a flood - Difficult to get insurance - Might not have access/hear warnings
Preparation
Buildings are modified to reduce damage
+ Less damage on buildings
+ People know what to do if a flood happens
+ Less likely to worry
- Doesn’t guarantee safety
- False sense of security
- Expensive to modify homes & businesses
Flood plain & Zoning
Restrictions preventing building on areas likely to flood
+ Impermeable surfaces aren’t made
+ Houses/ roads aren’t damaged
- Limited in Urban areas
- To late for some areas which have been built on
‘Do nothing’
+ Eroded material is deposited on the flood plain -> More fertile farmland
- Risk of flood & impacts aren’t reduced
- Flood will cause a lot of damage
Places with high population densities means…
A higher demand for water
The South east and midland are areas of…
Water deficit
The North and West are areas of…
Water surplus
Issues of Water transfer
- Dams and aqueducts needed are expensive
- Effects wildlife (fish migration)
- Political issues -> People don’t want their water given to another country
How the UK meets their water demand
- Water transfer (Birmingham deficit - Wales Surplus)
- Build more reservoirs
- Fixing leaky pipes - less water is lost during transfer
How to reduce demands of water
- People can reduce the amount of water they use at home (taking showers, only putting the dishwasher on when its full)
- Water companies said they want people to have water metres (charge for the exact volume of water they use)
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Plate Margins9
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Kielder Water management4
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