Unit 1 C River Landscapes In The Uk Flashcards
What does the long profile of a river show
How the gradient changes of the different courses
What does the cross profile show
What a cross-section of the river looks like
Describe the upper course of a rivers gradient,valley and channel shape
- steep gradient
- V-shaped valley,steep sides
- narrow,shallow channel
Describe the middle course of a rivers gradient,valley and channel shape
- medium gradient
- gently sloping valley sides
- wider,deeper channel
Describe the lower course of a rivers gradient,valley and channel shape
- gentle gradient
- very wide,almost flat valley
- very wide,deep channel
Vertical erosion
- deepens river valley and channel making it v-shaped
- dominant on the upper course of river
- high turbulence causes rough,angular particles to be scraped along the river bed,causing intense downwards erosion
Lateral erosion
- widens river valley and channel during formation of meanders
- dominant in middle and lower courses
What is hydraulic action
The sheer force of the water breaks rock particles away from the river channel
What is abrasion
When eroded rocks picked up by the river scrape and rub against the channel,wearing it away
What is attrition
When eroded rocks picked up by the river smash into each other and break into smaller fragments.their edges get rounded off as they rub together.
What is Solution
When river water dissolves some types of rock
How do waterfalls form
- form when river flows over area of hard rock followed by area of softer rock
- softer rock is eroded more than hard rock creating a ‘step’ in the river
- as water goes over step it erodes more or the softer rock
- steep drop is eventually created which is called a water full
how are gorges formed
- hard rock is eventually undercut by erosion from waterfall and becomes unsupported and collapses
- collapsed rock are swirled around at food of waterfall where they erode softer rock by abrasion which creates a plunge pool
- over time more undercutting causes more collapses. The waterfall retreats leaving behind a steep sided gorge
What are interlocking spurs
- rivers aren’t powerful enough to erode laterally in the upper course as they have to wind around the high hillsides that stick out into their paths on either side
- The hillsides that interlock with each other as the river winds around them are called interlocking spurs
Meanders
- current faster on outside of bend because river channel is deeper (less friction to slow water down)
- so more erosion takes place in outside of bend forming river cliffs
- current is slower on inside of bend because river is shallower (more friction to slow water down)
- so eroded material is deposited on inside of bend,forming slip-of slopes
Formation of ox-bow lakes
- erosion causes outside bends to get closer
- until there’s only small bit of land left between bends
- river breaks through this land,usually during flood
- and the river flows along along the shortest course
- deposition eventually cuts off meander forming and ox-bow lake
What are flood plains
The wide valley floor on either side of a river which occasionally gets flooded
What are levees and how are they formed
Natural embankments along the edges of a river channel.formed during a flood when eroded material is deposited over whole flood plain.heaviest material deposited closest to river channel because it gets dropped first when the river slows down.over time deposits material builds up creating levees
What are estuaries and where are they found
Tidal areas where river meets the sea found at the mouth of a river
Features of estuaries
- land is closest to sea level
- river valley at its widest
- river levels rise and fall each day
What land forms are in the upper course
V-shaped valleys Interlocking spurs Rapids Waterfalls Gorges
What landforms are in the middle course
Meanders
Ox-bow lakes
What landforms are in the lower course
Levees
Flood plains
List main landforms of a named river
River Clyde in Scotland
- gorges
- ox-bow lake starting to form
- waterfalls
- meanders
- flood plains and mud flats
What is river discharge
Volume of water that flows in river per second
What is peak discharge
The highest discharge in the period of time you’re looking at
What is lag time
The delay between peak rainfall and peak discharge
What is rising limb
The increase in river discharge as rainwater flows into river
What is falling limb
The decrease in river discharge as the river returns to its normal level
Define flooding
Happens when the level of a river gets so high that it spills over its banks.river level increases when discharge increases because high discharge means more water in a channel.
causes of flooding
- prolonged rainfall-soil becomes saturated further rainfall can’t infiltrate so increases surface run-off
- heavy rainfall-water arrives to rapidly for infiltration,increases run-off
- geology-impermeable surface create run-off
- relief-water will reach river quicker if has steep sides
- land use-buildings made from impermeable materials and removing trees that intercept water
What are dams and reservoirs
Dams are built across rivers usually in upper course. And reservoir (artificial lake) is formed behind dam
What are the benefits and costs of dams and reservoirs
B- store water prevent flooding
B-reservoir water used as drinking water and generate hydroelectric power
C-dams very expensive
C-reservoir can flood existing settlements
What is channel straitening
When the rivers course is straightened-meanders are cut out by building artificial straight channels
What are the benefits and costs of channel straightening
B-water moves out area quickly doesn’t travel as far, reduces flooding
C-flooding may happen downstream instead as water carries there faster
C-more erosion downstream because flowing faster
What are embankments
Raised walls that are built along the river banks
What are the Benefits and costs of embankments
B-river can hold more water
C-expensive
C-risk of severe flooding of break or water rise above
What are flood relief channels
Channels built that divert water around important areas or take elsewhere if water level is too high
What are benefits and costs of flood relief channels
B-river discharge reduced
B-gates in flood relief channel can control release of water
C-increased discharged where relief channel rejoins river
What are benefits and costs of flood warnings
B-impacts if flooding is reduced
C-don’t stop flood from happening
C-people may not hear or have access to warnings
What are benefits and costs of preparation
B-impact of flooding reduced
B-people less likely to worry
C-doesn’t guarantee safety could give false sense of security
C-expensive
What are benefits and costs of flood plain zoning
B-risk of flooding reduced
B-impact reduced
C-expansion of urban area becomes limited
C-no help in areas that have already been built on
What are benefits and costs of planting trees
B-discharge and flood risk reduced
B-vegetation provides habitats
C-less land available for farming
What is river restoration
Involves making river more natural removing man made features
What are benefits and costs of river restoration
B-discharge reduced
B-little maintenance needed
B-better habitats for wildlife
C-local flood risk can increase
Using a named example of a flood management scheme explain why the scheme was needed
Village of Boscastle on north coast of Cornwall devastated by flash flood 16th august 2004 caused millions of pounds of damage.village surrounded by steep valley sides and land upstream cleared of trees and vegetation.low bridge of narrow river channel
Give two features of the Boscastle scheme and explain how they reduced flood risk
- old bridge replace with new,higher bridge so things don’t get stuck and create a dam
- Gauge introduced to monitor water levels and improve flood prediction so people can evacuate
Give 1 social,1 economic and 1 environmental issue with the Boscastle flood management scheme
Social: residents lives were disrupted for years by rebuilding projects and construction of flood defences
Economic:scheme cost over £4 million and isn’t as good as it could be
Environmental: vegetation and river habitats in area are continuously managed.biodiversity and river habitats have been improved
Traction
Large particles like boulders pushed along river bed by force of water
Saltation
Pebble-sized particles bounced along river bed by force of water
Suspension
Small particles like silt + clay carried along by water
Solution
Soluble material dissolve in water and carried along
Why rivers deposit sediment
- Volume of water in river falls
- Amount of eroded material in water increases
- Water is shallower
- River reaches its mouth
