P1. Section C (2) Flashcards
what is the (river) mouth?
where the river goes into the sea
what is the (river) source?
where the river starts
what is the (river) drainage basin?
area of land drained by a river
what is the (river) watershed?
the boundary around the drainage basin
what is the (river) confluence?
where 2 rivers meet
what is the (river) bedload?
material that is in the river
what are (river) tributaries?
when a small stream of rivers joins the larger one
(n.d list) explain the formation of a waterfall, meander, ox-bow lake, gorge, interlocking spurs)
what is a meander?
a bend in a river
how is a meander formed?
what is lateral erosion?
erodes side of river
what is thalweg?
the fastest flow within river bend
what causes a river to change shape?
a little disturbance and a lot of time
what happens at the fastest part of the river?
more curves are formed as the water smashes into the side of the bank (hydraulic action)
what happens at the slowest past of a river?
deposition happens
What course does a river run fastest? why?
lower course because…
Explain the formation of an ox-bow lake
what are 3 lower course landforms?
Levees, floodplains, estuaries
what are flood plains?
relatively flat areas of land that form either side of the river channel. They are made from alluvium
- formed on lower course
what is alluvium?
sediment that is deposited by a river during flood events
Explain the formation of a floodplain.
what are levees
naturally raised river banks (ridges of sediment) found on either or both sides of a river channel
make flash cards for the drainage system
what are 3 human causes of flooding?
- Farming methods such as ploughing
- Deforestation
- building infrastructure
what are 4 physical causes of flooding?
- Sudden bursts of heavy rainfall
- areas with impermeable rock
- previous heavy rainfall
- sudden snow melts
what is a river’s discharge?
the amount of water in a river at any point at any given time
what is a hydrograph?
a graph that shows how river discharge changes in response to a precipitation event
what is lagtime?
the difference between the peak of the rainstorm and the flow of the river
(peak discharge - peak rainfall)
what is hard-engineering?
using man-made/ artificial structures to defend against river flooding.
what are 4 hard engineering methods for flooding?
1.Dams and reservoirs
2. Channel Straightening
3. Embankments
4. Flood relief channels
what are dams and reservoirs?
Dams- a concrete barrier built across a river channel
Reservoirs - artificial lake formed behind dam
how do dams and reservoirs reduce the risk of flooding?
water held behind the dam is released in controlled manner in order to decrease the amount of river flow
what are 6 advantages of dams and reservoirs?
- Boosts tourism
- attractive Kielder dam attracts 300,000 tourists a year boosting economy by £6 million - It’s a source of drinking water -
supplies 200,000 million litres of water to North east england. - provides hydroelectric power
- turbines may be places in dams –> Kielder generates 6MW of energy - promotes new habitats
- Kielder has conservation areas for rare red squirels - Areas around reservoirs may be planted with forests
- 150m trees were planted around Kielder providing employment - highly effective - releases of water are highly controlled –> so no flooding
what are 2 disadvantages of dams and reservoirs?
- Displaces people
- large areas of land are flooded - Expensive
- Kielder dam cost £167 million
what is channel straightening and how does it reduce flooding?
when a meander is widened and straightened and deepened course
- water flows in a straight line so doesn’t travel extra distances
what are 3 advantages of channel straightening?
- increase in homeowner confidence
- encourages ppl to invest in their property as flood risk reduced
- Insurance costs go down - improved navigation and trade
- Flood risk reduced
what are 4 disadvantages of channel straightening?
- Expensive
- £5.8 million spent on dredging 5 mile section of river after 2014 floods - Unattractive
- river may have a concrete lining and also impacts in burrowing river animals - increase pollution - agro chemicals as run off can’t drain into river so easily
- endanger animals and destroys habitats
what are embankments? how do they reduce flood risks?
they are artificially raised river banks.
- increases river’s capacity
what are 4 advantages of embankments?
- provide long distant walking routes for people
- cheaper
- provides habitats for river bank animals (e.g volves)
- safer flooding as the river’s capacity increases
what are 4 disadvantages of embankments?
- deprive people of access to river for fishing and boating
- not as reliable
- high maintenance cost
- need constant monitoring ad repairing - give people a false sense of security.
what are flood relief channels and how do they reduce risk of flooding?
an artificially made channel designed as a back up channel for a river, runs parallel to main river
- water can flow in 2 directions, reduces amount of water in river channel
what are 6 advantages of flood relief channels?
- Insurance cost become lower
- Value of homes increases
- secure environment so businesses can be created
- calm water allows boating and canoeing
- some relief channels include artificial reed bed and grass covered concrete side —> providing habitats
- Exter’s relief channels protect around 3000 properties.
what are 5 disadvantages of flood relief channels?
- people that live in the south of a relief channel have to be moved, causing disruption
- settlements downstream suffer from increased flooding as the merging water from the relief channel swells this part of the river –> this raises questions about ethics
- Expensive –> sometimes runs out of funds
- Need to be maintained and repaired
- take long time to come into effect
what are soft engineering methods for flooding?
- flood plain zoning
- planting trees
- flood warnings and preparation
- river restoration
what is flood plain zoning? how does this reduce flooding?
what are 3 advantages of flood plain zoning?
- cheaper –> only administrative costs involved
- provides green space
- traditional water meadows by a river are protected from development
what are 3 disadvantages of flood plain zoning?
- Habitats are destroyed due to increased building on other green sites
- it is difficult to get planning permissions or extend homes on the flood plain
- there is a housing shortage in the uk –> restricting buildings increases this problem –> restricted supply means house prices increase
what are flood warning and preparation? how do they reduce flooding?
when environment agency and other agencies work together to create and carry out action plans for areas at risk
- data is analysed
- warning published on social media
what are 2 advantages of flood warning and preparation?
- cheap way of protecting property –> makes ppl feel secure and in control
- if people are warned they can protect their valuables
what are 2 disadvantages of flood warning and preparation?
- Doesn’t help people living in areas prone to flooding —> people have to move to temporary accommodation and their insurance costs increases
- Only effective if people listen and take action –> education is needed , not everyone has access or listens to social media or internet
what is planting trees? how does it reduce flooding?
what are 3 advantages of planting trees?
- reduces water flowing downstream –> reduces surface run-off
- more CO2 is absored
- adds variety to landscape and new habitats –> increased biodiversity
what are 2 disadvantages of planting trees?
- loss of potential grazing land where tress have been planted
- countryside wooded rather than open grass –> artificial looking —> less aesthetically pleasing
what is river restoration? how does it decrease flood risk?
what are advantages of river restoration?
- aesthetically pleasing –> e.g visitor number to Sutcliff park increases
- creates new wetland habitats –> increases bio-diversity
- Increased water storage –> reduce risk of flooding downstream
what are disadvantages of river restoration?
- expensive –> e.g River Quaggy estimated £11 million
- not always most effective or practical
- possible less of agricultural land and flooding of crops near the river
What is casestudy/ example for flood management schemes?
Boscastle, Cornwall
why is flood management needed in Boscastle?
- Heavy localised rainfall - 89mm of rain fell in an hour in 2004 –> so ground became saturated
- Narrow river channel
- Tography of the land - the landscape upstream of Bosastle acts as a funnel, directing vast volumes of water into the village. The valley sides are steep sided
what 3 soft engineering method did Boscastle use?
- A gauge to monitor water levels and improve flood prediction
- Car park raised and left as an area that can flood to cope with excess water
- dead trees and vegetation are removed to stop them blocking the river channel during floods
what are 4 hard engineering method Boscastle used?
- strengthened river embankment
- new flood wall built
- old bridge replaced with new bridge with higher arch
- river channel deepened and widened
