Physical Flashcards
attrition
rocks that bash together to become smaller
solution
a chemical reaction that dissolves rocks
abrasion
rocks hurled at the base of a cliff to break pieces apart or scraped against the banks and bed of a river
hydraulic action
water enters cracks in the cliff or river bank, air compresses, causing the crack to expand
solution
minerals dissolve in water and are carried along
suspension
sediment is carried along in the flow of the water
saltation
pebbles that bounce along the river bed
traction
boulders that roll along the river by the force of the flowing river
deposition
when the sea or river loses energy, it drops the sand, rock particles and pebbles it has been carrying.
precipitation
moisture falling from clouds as rain, snow or hail
interception
vegetation prevents water reaching the ground
surface runoff
water flowing over the surfaces of the land into rivers
infiltration
water absorbed into the soil from the ground
transpiration
water loss through leaves and plants
physical causes of flooding
- prolonged heavy rainfall causes soil to become saturated leading runoff
- relief - steep sided valleys channels water to flow quickly into rivers causing greater discharge
- impermeable rocks causes surface runoff to increase river discharge
human causes of flooding
tarmac and concrete are impermeable this prevents infiltration and causes surface runoff
upper course of river
Near the source, the river flows over steep gradient from the hill this gives the river a lot of energy, so it will erode the riverbed vertically to form narrow valleys
middle course of river
Here the gradient gets gentler, so the water has less energy and moves more slowly. The river will begin to erode laterally making the river wider
lower course of the river
Near the rivers mouth, the river widens further and becomes flatter. Material transported is deposited
Formation of waterfall
- river flows over alternative types of rocks
- river erodes soft rock faster creating a step
- further hydraulic action and abrasion form a plunge pool beneath
- hard rock above is undercut leaving cap rock which collapses providing more material for erosion
- waterfall retreats leaving steep sided gorge
formation of floodplains and levees
When a river floods, fine silt is deposited on the valley floor, closer to the rivers banks, the heavier materials build up to form natural levees.
formation of ox bow lakes
- erosion of outer bank forms rover cliff. Deposition inner bank forms slip off slope
- further hydraulic action and abrasion of outer banks, neck gets smaller
- erosion breaks through neck, so river takes the fastest route, redirecting flow.
- evaporation and deposition cuts off main channel leaving an oxbow lake
soft engineering
afforestation - plant trees to soak up rainwater, reduces flood risk
demountable flood barriers - put in place when warning raised
managed flooding - naturally let areas flood, protect settlements
hard engineering
straightening channel - increases velocity to remove flood water
artificial levees - heightens river so flood water is contained
deepening or widening river - to increase capacity for a flood
River Tees geomorphic processes
upper - V-shaped valleys, rapids and waterfalls
- high force waterfall
middle - meanders and ox bow lakes
lower - greater lateral erosion creates features such as floodplains and levees
Formation of bays and headlands
- waves attack the coastline
- softer rock is eroded by the sea quicker
- more resistant rock is left jutting out into the sea this is a headland
Formation of coastal spits
- swash moves up the beach in the direction of wind
- backwash moves down the beach at 90 degree
- LSD transports material along the beach
- deposition causes beach to extent
- change in wind direction forms a hook
- behind spit, deposition forms salt marshes
constructive waves
has a swash that is stronger than the backwash, therefore builds up the coast
destructive waves
has a backwash that is stronger than the swash, therefore erodes the coast
formation of coastal stack
- Hydraulic action widens cracks in the cliff face
- Abrasion forms a wave cut notch
- further abrasion widens notch into a cave
- Caves on both sides of the headland break through to form an arch
- erosion causes it to collapse and form a stack
- further weathering and erosion leaves a stump
Hard engineering defences
Groynes - Wood barriers prevent LSD, so the beach can build up.
Sea walls - Concrete walls break up the energy of the wave . Has a lip to stop waves going over.
Gabions - Cages of rocks absorb the waves energy, protecting the cliff behind.
Soft engineering defences
Beach nourishment - Beaches built up with sand, so waves have to travel further before eroding cliffs.
Managed retreat - Low value areas of the coast are left to flood & erode.
Coastal Management Lyme Regis, Dorset
Geomorphic Processes
Geomorphic Processes
Unstable cliffs – soft clays on top of stronger limestone – landslips common.
Strong waves beach removed by strong storms
Coastal Management Lyme Regis, Dorset
Hard engineering & Soft engineering
- New sea wall and promenade
- Rock armour near jetty
- Large stone groynes built
- Nailing and improving drainage of cliffs
- Sand imported from France – beach replenishment
Coastal Management Lyme Regis, Dorset
evaluation
- New defences stood up to recent winter storms
- Visitor numbers have increased
- Coastal processes (LSD) interfered with – affects coastline to the West.
Case Study: The River Tees
Management
- Yarm and Middleborough are economically and socially important due to houses and jobs that are located there.
-Dams and reservoirs in the upper course, controls river’s flow during high & low rainfall. - Better flood warning systems, more flood zoning and river dredging reduces flooding.
