topic 4 || the uk's evolving physical landscape

why is flood risk increasing in the UK?

why is flood risk increasing in the UK?

• increasing population so more housing being built on floodplains

• changes to land use e.g more impermeable surfaces so greater surface run-off

• changes to weather patterns due to climate change e.g storms, drought

dams and reservoirs - hard or soft?

hard engineering

river straightening and dredging - hard or soft?

hard engineering

embankments (levees) - hard or soft?

hard engineering

flood relief channels - hard or soft?

soft engineering

demountable flood banters - hard or soft?

soft engineering

flood barriers/storm surge barriers - hard or soft?

hard engineering

flood warnings and preparation - hard or soft?

soft engineering

floodplain zoning - hard or soft?

soft engineering

river restoration - hard or soft?

soft engineering

positives of dams and reservoirs

• can attract tourists

• can be used to produce electricity by passing water through a turbine within the dam

negatives of dams and reservoirs

• dams trap sediment - reservoirs can hold less water

• habitats are flooded so leads to rotting vegetation

cost of dams and reservoirs

very expensive

positives of river straightening and dredging

• more water can be held in the channel

• can be used to reduce flood risk in built-up areas

negatives of river straightening and dredging

• dredging needs to be done frequently

• speeding up the river increases the flood risk downstream

cost of river straightening and dredging

expensive

positives of embankments (levees)

• cheap with a one-off cost

• allows flood water to be contained within the river

negatives of embankments (levees)

• looks unnatural

• water speeds up and can increase flood risk downstream

cost of embankments (levees)

cheap

positives of flood relief channels

• removes excess water from the river channel to reduce flooding

negatives of flood relief channels

• expensive to build

• if water levels continue to rise, the relief channel may also flood

cost of flood relief channels

expensive

positives of demountable flood barriers

• good for places where a permanent sea wall would look ugly

• more cost efficient than permanent barriers

negatives of demountable flood barriers

• need 24 hours warning to set the barriers up so risk that not installed in time

• can only be used in that specific location

cost of demountable flood barriers

cheap

positives of flood barriers/storm surge barriers

• can protect large areas from storm surges

• the gates can be closed when a high tide is forecast

negatives of flood barriers/storm surge barriers

• construction costs high

• regular maintenance needed

cost of flood barriers/storm surge barriers

very expensive

positives of flood warnings and preparation

• people have time to protect their properties

• many posessions can be saved, resulting in fewer insurance claims

negatives of flood warnings and preparation

• some people may not be able to access the warnings

• flash floods may happen too quickly for a warning to be effective

cost of flood warnings and preparation

fairly cheap

positives of floodplain zoning

• more expensive buildings and land uses are further away from the river, so have a reduced flood risk

• less damage is caused

negatives of floodplain zoning

• not always possible to change existing land uses

• planners have to decide what type of flood to plan for

cost of floodplain zoning

cheap

positives of river restoration

• restoring meanders help to slow down the rivers

• natural rivers are more attractive and better for wildlife

negatives of river restoration

• flooding is still likely

• flood banks will still be needed

• may result in change of land use

cost of river restoration

cheap at first, but gets really expensive

define evaporation

the transfer and change of water from the ground into water vapour in the air

define evapo-transpiration

the transfer and change of water from plants into water vapour in the air

define condensation

water vapour in the air changing back into a liquid

how are clouds formed through condensation?

it forms small droplets which are visible as cloud

define precipitation

the transfer of water from the air to the land. water can fall as snow, rain, or sleet

define overland flow (surface run-off)

the transfer of water back to the sea over the ground surface

define groundwater flow

the transfer of water through the ground back to the sea

define perlocation

water seeping deeper below the surface into the ground layer

define interception

water being prevented from reaching the surface by trees or grass

the water cycle diagram

explain how surface run off could be impacted by human actions (4 marks)

key points:

-human actions can speed up surface run-off

-buildings roads because roads can be large, flat and impermeable

-human actions slows down surface run-off

-planting more trees because trees can intercept rainfall preventing it from reaching the ground

what is a drainage basin?

an area of land drained by a river and its tributaries

what is the source in a drainage basin?

the starting point of the river

define tributaries

the streams and smaller rivers that feed into a main river

most rivers flow down towards sea level even if they don't reach the sea. true or false?

false. the correction should be "all rivers flow down towards sea level

define confluence

the point where two rivers join

what is the watershed?

an imaginary line that seperates one drainage basin from the next

what is the flood plain?

the area of low-lying ground that gets flooded when the river overflows

the river gets ________ as you go from the source to the mouth.

wider

what is the surface storage?

where water is held on the ground surface e.g. lakes, puddles

define infiltration

where water sinks into the soil or rock from the ground surface

what is the water table?

the current upper level of saturated rock/soil where no more water can be absorbed

define throughflow

water flowing through the soil layer parallel to the surface

define groundwater

water stored in rock

define permeable

when water is able to seep through the material through the pore spaces.

define impermeable

when water is not able to seep through the material as there is little or no space.

heavy rainfall - physical or human?

physical

loss of trees (deforestation) - physical or human?

human

steep slopes - physical or human?

physical

prolonged rainfall - physical or human?

physical

soggy soil - physical or human?

physical

tributaries running into the river - physical or human?

physical

building on flood plains - physical or human?

human

snowmelt - physical or human?

physical

impermeable rocks - physical or human?

physical

built up areas - physical or human?

human

roads being built - physical or human?

human

altering the course of rivers - physical or human?

human

what is the most significant cause of flooding?

example structure: The most significant cause of flooding is _____ in my opinion because _____. It can more significant than _____ because _____.

freeze thaw

when rainwater enters gaps in rocks and freezes, the ice puts pressure on the rock and causes it to break

acid rain

rain containing high amounts of chemical pollutants such as nitric and sulfuric acids, which when it falls can react with the minerals in the ground and cause dissolving and decay.

biological weathering

when the roots of plants grow into cracks of gaps and pushes the rock apart

soil creep

individual particles of soil move slowly down a slope due to gravity

slumping

when the bottom of a valley side is eroded, the slope becomes steeper and the material slides downwards

hydraulic action

sheer force of water hitting the river bed and banks, wearing them away

abrasion

material scraping or rubbing along the banks and bed of the river

solution

river water is slightly acidic so can dissolve some rocks and minerals

attrition

particles in the river bashing into each other, wearing each other down and becoming smaller and rounder

traction

stones rolling along the river bed

saltation

smaller particles bouncing along the river bed

suspension

the water flow carries silt and sand particles

erosion

the breaking away and removal of materials by a moving force e.g. river, wave, glacier

four types of erosion?

hydraulic action, abrasion, attrition & solution

weathering

the breakdown & decay of rock by natural processes acting on rocks, cliffs & valley sides

three types of weathering?

physical, chemical, biological

mass movement

the movement of material down a slope due to gravity

four types of mass movement?

falls, slumps/slides, creeps and flows

mudflow

saturated soil flows down a slope

landslide

large blocks of rock slide downhill

rockfall

bits of rock fall off the cliff face, usually due to freeze-thaw weathering

transportation

the carrying of sediment downstream from the point where it has been eroded to where it is deposited

four types of transportation?

solution, suspension, saltation, traction

deposition

when a river loses energy it drops/deposits the sediment it has been carrying