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Flashcards in Floods Deck (25)
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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



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)


Reasons for an increasing demand of water

- Population (higher demand)
- Housing
- Industry
- Climate (Global warming, drought, water shortage)