1C:Physical Landscapes in UK Rivers and Coasts

how do stumps form

what is a dis/concordant coast and what feature forms

crack, cave, arch, stack:bottom erodes and top falls into sea, stump

discordant coast- bands of alternate rock
headlands and bays form because headland (hard rock erodes slower than softbay)
concordant rock is all the same type

how to waves form, define fetch, and what are the two types

waves form wen wind blows over the sea, friction w the wind’s surface causes ripples that develop into waves
fetch- distance wind blows across water

constructive wave:
far apart crests, strong swash, weak backswash, builds gentle beach, breaking wave spills over

destructive:
strong backswash pulls sand/pebbles, breaking waves go down

describe types of hard and soft engineering

hard:

sea wall- concrete barrier breaks waves, expensive
groynes- collect sediment to widen beach, starves others further along
rock armour-piles of rock forcing waves to break and have less energy, cheap
gabions-wire cage of rock to support cliff, cheap but lasts 10 years

soft:
beach nourishment & dune fencing- adds sand/shingle to make beach higher/wider, expensive but looks natural
managed retreat-floods low value land sustainable,lose land
dune regeneration- planting grass to stabilise dunes, cheap, can be damaged by storms

Lyme Regis: challenges and solutions + and-

challenges: msot of town built on unstable cliff and limestone which slides over muds/clay underneath, coastline rapidly eroding due to powerful SW winds, damaging properties

solution:
+more tourism(34500 employed in tourism)
+seafront business are thriving
+withstood winter storms
+better protected harbour is good for boat owners and fishermen

-sea wall interferes w coastal processes affecting neighbouring towns
-cost £22 million

when does coastal deposition occur, and what features does it create

sea loses energy and drops pebbles it was carrying, occurs in areas w slow flow of water, when a river enters shallow water

creates:
beaches-constructive waves bring in sediment, strong swash builds up beaches, rock if high energy waves wash out sand
spits-(long narrow line of sediment going into sea from land)longshore drift, change in wind direction results in a hook
bars- gap in coastland w water in it, deposited material from longshore drift at an angle
sand dunes-embryo dunes from wood/rocks develop and become stabilised →vegetation grows→organic matter forms depressions(ponds)

how do wave cut notches and platforms form

1. erosion at base of cliff

2. unstable rock above cliff

3. top of cliff collapses into sea

4. new wave cut notch forms and collapsed material is cleared by sea

5. overtime the cliff retreats forming a wave cut platform

what are the 3 types of weathering

weathering-breaking down of rocks in/close to ground

physical/freeze thaw:

1. water collects in crack

2. temp below 0 so it freezes expanding, widening crack

3. temp rise and ice melts

4. this repeats and fragments of rock break off

chemical: rainwater is slightly acidic so it causes rocks like chalk and limestone to slowly dissolve
biological:plant roots grow in rocks cracks or animals like rabbits burrow in weak rocks

3 types of mass movement

slumping/s???ing: collapse of weak/saturated soil in a straight line
sliding: large blocks of sand slide down cliff as a landslide w lots of action
rock falls:material breaks up and falls down slope

what is longshore drift

the gradual movement of sediment along a shore in a zigzag motion
1. wave arrives at coast
2. swash moves sediment up the beach
3. backswash is always a straight line due to gravity

infiltration vs percolation, ground water flow vs through flow

infiltration- water enters soil percolation- water enters rock
groundwater- water travels through soil, percolation-water travels through rock

define: tributary, river drainage basin and watershed

tributary- smaller river that joins a bigger one
drainage basin- area drained by a river
watershed- edge of drainage basin(if water falls outside of watershed it goes to another river)

define: source, mouth, river channel and confluence

source-where river begins
mouth- where river meets sea
river channel- main river
confluence- where rivers join

how does valley shape change from upper to lower course

upper course- v shaped valley with steep sides
lower course-very wide and flat valley

how does the channel change from upper to lower course

upper course- narrow and shallow
lower course- deep and wide

how does the gradient of a river change from source to mouth

source- steep mouth- almost flat

what is vertical erosion, what is lateral erosion, which takes place in upper/lower course

vertical erosion- deepens river valley, very high turbulence so particles scrape along river bed causing it to cut down, in upper course
lateral erosion- widens river bed, causes meanders, carries sediment, in lower course
both in middle course

what are the 4 processes of erosion

abrasion, attrition, hydraulic action, corrosion

define the 4 process of transportation
which happen in fast/slow water

traction- large particles brushed along by water’s force
saltation- pebble sized particles bounced along by water’s force
solution- soluble material dissolved in water
suspension- small particles are carried along by water
all happen in fast water, but only suspension and solution in slow water

when does deposition occur

speed of river slows so less energy to carry materials because: shallow water, river reaches mouth, more eroded material

what forms on the upper course of a river

waterfalls and gorges, interlocking spurs, v shaped valleys, lots of erosion

landforms in the middle course of a river

meanders and oxbow lakes

river landforms in the lower course

formed by deposition, levees, floodplains, estuaries

what is lag time and factors that increase lag time

time for rain to get to river
factors- more trees, forest. permeable rock

how do interlocking spurs form

when there are areas of harder rock are difficult to eroded so river bends around it

how to waterfalls and gorges form

1. hard rock e.g limestone, on top and soft rock e.g. sandstone, on bottom

2. soft rock erodes faster creating a plunge pool where debris and water swirl

3. debris and water in plunge pool erode it, deepening it, creating an overhang of hard rock

4. hard rock is no longer supported and collapses due to gravity

5. erosion continues so waterfall retreats upstream forming a gorge

how do meanders form

1. faster current on outside of bend, so less friction to slow down, since the river channel is deeper

2. erosion outside bend forms river cliffs

3. slower current inside bend, since more friction to slow down as channel is shallower

4. deposition inside bend forming slip off slopes

how do oxbow lakes form

1. erosion causes outside of bends to get closer

2. neck forms when only a small bit of land is left

3. river breaks through this land, usually during a floood

4. river flows along shortest course(through neck)

5. deposition eventually cuts off meander forming an oxbow lake

how do floodplains form

1. river floods so water loses energy depositing sediment which builds up flood plain

2. meanders migrate laterally(to the side) and also downwards over time

3. deposition on slip off slopes(from meander) builds up flood plain

how do levees form

1. during a flood, eroded material is deposited over floodplain

2. heaviest material is deposited closer to channel since the river slows down, losing energy

3. finer sediment is carried further onto floodplain

4. over time deposited materials build up creating levées along the edge of the channel

what are estuaries, how do they form and what affects their size add more later

estuaries are bodies of water opening to the sea
form when freshwater of river meets saltwater of an ocean, at the mouth.
size of estuary depends on the size of the river that feeds it and the condition of the land where river meets sea

what are the 4 types of hard engineering and soft engineering

hard- dams and reservoirs, channel straightening, embankments, flood relief channels
soft- river restoration, afforestation, wetlands/flood storage areas, floodland zoning

describe dams and reservoirs (3+ and 3-)

regulate river flow, reducing flood risk
+ hydroelectricity, water supply, irrigation
- expensive, disrupts fish migration, floods surrounding land to build

describe channel straightening

cutting through meanders to create a straight channel, concrete lining smooths surface, speeding water flow preventing collapse of river banks
-looks unattractive, reduces range of aquatic habitats

describe embankments

artificial levees to raise river bank so more water is held before flooding
+cheap if made from mud, but concrete embankments are more effective and expensive
+can be covered with vegetation to look natural
-reduce biodiversity

describe flood relief channels

artificial river channels constructed to bypass an urban area
+supports biodiverse aquatic ecosystems, provides leisure and recreation opportunities
-involves changing land use so roads close affecting local community access and farmers may lose land

describe river restoration

reverting river to its natural form by removing everything artificial, uses natural processes and features of a river e.g meanders to slow river’s flow, preventing floods
+biodiversity by creating habitats
+cheap
+aesthetically pleasing

describe afforestation

planting trees, which intercepts rainfall reducing lag time, reducing flooding
+cheap
+creates habitats → biodiversity
+reduces global warming

describe wetlands and flood storage areas

allowing low value areas of land to flood naturally so that high value land downstream isn’t flooded
+ecosystems on wetlands flourish
-often farmland that is allowed to flood

floodplain zoning

restricts different land use to certain areas on the floodplain so the higher the value, the further from the high risk area, but landcan still be used
river→ parks →roads and carparks →industry→houses and shops

human and physical causes of flooding

human- deforestation and urbanisation
physical- high rainfall, saturated soil, steep slopes

define: flood watch, flood warning, severe flood watch

flood watch- flooding of low-lying land and roads is expected
flood warning- threat to homes and businesses, move valuables to upper floor and turn off electricity
severe flood warning- leave property or stay upstairs

how are properties protected from flooding

floodgates and sandbags- keep floodwater away
move high valuables upstairs, turn off electricity

where isriver flood management case study

Banbury, Oxfordshire, North West of London. River Cherwell a tributary of the river Thames

How has Banbury been affected by flooding

1998, £12.5 million in damage, 150 homes damaged, shut local roads and railway stations

who funded the defences for Banbury flooding

Oxfordshire County Council, Environment Agency, National Rail, DEFRA(a UK government sector)

what has been done to reduce the risk of flooding in Banbury

• 2.9km embankment, created a flood storage area capable of holiding 3 million m³ of water, located on River Chirwell’s floodplain to collect rainwater that would’ve swelled river bursting its banks

• floodgates, control river flow down stream, so excess water backs up filling a resevoir instead of flooding, no need to open/close floodgates

• new pumping station transfers excess water to a river below town

• new biodiversity action plan habitat with ponds, trees and hedgerows to absorb excess water

• raised A361 road and added improvements to drainage so it no longer closes during floods

What were the benefits of Banbury’s flood management plan

• raised A361 route → open during floods so no disruption to life

• quality oflife improved for local people → reduced levels of anxiety from fear of flooding

• protected 441 houses and 73 commercial properties, saving over £100 million

• biodiversity action plan encourages wildlife

what were the disadvantages of Banbury’s flood management scheme

• £18.5 million cost

• part of the floodplain will deliberately be allowed to flood if river levels are high

• around 100,000 tonnes of earth required to build the embankment, which was extracted from nearby