UK Physical Landscape: Rivers Flashcards
Source
The start of the river
Confluence
Point where two rivers join
Tributaries
Where the smaller river joins the main river
Watershed
Imaginary line which separate two drainage basins
Mouth
A river flows into the lake, sea or ocean
Upper course
Shallow
Slowest
V-shaped
Steepest
Middle course
Deeper
Faster
U-shaped
Flatter
Lower course
Deepest
Fastest
Open floodplain
Flattest
Erosion
Same four as coasts, only the processes act upon the river bank / bed
Transportation
Same four as coasts, but work from upper to lower course
Deposition
River will drop load when it loses energy
Interlocking spurs / v-shaped valley (UPPER COURSE)
The river erodes vertically and therefore is unstable
Gravity causes it to collapse = v-shaped valley
The process repeats, deepening the valley
As the river flows through the valley it is forced to swing from side to side (spurs)
Waterfalls / gorges (UPPER COURSE)
Waterfalls form when there is hard rock on top of soft rock
The soft rock is eroded through hydraulic action and abrasion
This leaves an overhang of hard rock which becomes undercut and collapses due to gravity; creating a plunge pool
Overtime the waterfall retreats due to headward erosion creating gorges (steep-sided river valleys)
Meanders (MIDDLE COURSE)
Lateral erosion widens the river
The current of the river is pushed towards the outside bend and therefore there is more erosion; hydraulic action and abrasion
The lateral erosion on the outside bend causes undercutting
Water on the inner bend is slower, causing material to be deposited creating a slip of slope
Ox-bow lakes (MIDDLE COURSE)
The neck of the meander has become narrower due to more erosion
The neck of the meander becomes cut through
Deposition seals off the end of the old meander
Vegetation grows in between the ox-bow lake and the river
Floodplains (LOWER COURSE)
Erosion removes any steep valley sides creating a wide flat area on either side of the river
During a flood, material carried by the river is deposited, building up the floodplain
Meanders migrating across the floodplain also makes it wider
Leeves (LOWER COURSE)
Leeves are natural embankments along the edges of a river channel
During a flood, eroded material is deposited over the whole floodplain
Estuaries (LOWER COURSE)
The water floods over the banks of the river carrying the silt and sand onto the valley floor
As the tide reaches its highest point, the water moves slowly and the sediment is deposited
Over time this builds up more, creating large mudflats
At low tides, the wide mudflats are exposed
River Tees
Location - North East
Source - Pennine Hills near Cross Fell (893m)
Mouth - Middlesbrough at the North Sea
Upper course landform - High Force waterfall and gorges
Middle / lower course landforms - meanders, levees and floodplains
Human factors causing flooding
Deforestation
Urbanisation
Climate change
Storage reservoirs
Physical / Natural factors causing flooding
Relief of land
Prolonged or antecedent rainfall
Soil saturation
Climate change
Lag time (hydrograph)
How long it takes the river to fill up
Peak discharge (hydrograph)
Maximum discharge in the river
Rising limb (Hydrograph)
The rising flood water in the river
Falling limb (hydrograph)
The falling flood water in the river
Hard engineering
Dams - man made barriers holding out water
Channel straightening - when a meander is engineered to become straighter
Embankments - artificially raised river bank
Flood relief channel - artificially made channel designed to back a frequently flooding channel
Dams - advantages
Environmental - turbines can be placed in dams
Economic - creates jobs when building
Social - attracts tourists
Dams - disadvantages
Environmental - create earthquakes when building
Economic - expensive
Social - farmers homes are flooded
Channel straightening - advantages
Environmental - flood risk is reduced
Economic - improve navigation and trade
Social - increase in homeowner confidence
Channel straightening - disadvantages
Environmental - animals’ habitats are destroyed
Economic - expensive
Social - unnatractive
Embankments - advantages
Environmental - lowered risks to settlements
Economic - cheapest solution
Social - provides walking routes
Embankments - disadvantages
Environmental - water lies on land for a long time
Economic - high maintenance cost as repairs needed
Social - people cannot fish or boat in the river
Flood relief channel - advantages
Environmental - removes risk of flooding
Economic - insurance costs are lower
Social - recreational area for boating and canoeing
Flood relief channel - disadvantages
Environmental - home downstream suffer from flood
Economic - expensive
Social - people have to move
Soft engineering
Flood plain zoning - restrictions preventing buildings on flood plains
Flood warnings - the environment agency warning people about flooding through media
Preparation - when buildings are modified to reduce damage
Planting trees - increases interception of water, increases lag time
River restoration - making the river natural by removing man-made leeves
Flood plain zoning - advantages
Environmental - the impact of flooding is reduced
Economic - no buildings are damaged
Flood plain zoning - disadvantages
Economic - expansion of urban areas is limited
Social - no help in areas already built on
Flood warnings - advantages
Environmental - the impact of flooding is reduced
Social - warnings give time for people to move
Flood warning - disadvantages
Environmental - does not stop the flood
Social - some may not have access to the media
Preparation - advantages
Environmental - impact of flooding is reduced
Social - people won’t worry about the floods
Preparation - disadvantages
Environmental - doesn’t guarantee safety
Economic - expensive to modify buildings
Planting trees - advantages
Environmental - discharge and flood risk are reduced + provide habitats for wildlife
Planting trees - disadvantages
Environmental - less land available for farming
River restoration - advantages
Environmental - discharge is reduced, so less flooding
Economic - little maintenance
River restoration - disadvantages
Environmental - local flood risk can increase
Banbury
Location - Cotswold Hills, 50km north of Oxford
Flooding history - 1998 was the closure of towns and railways
2007 homes were destroyed
2012 scheme - flow control structures, embankments, pumping station, BAP
Benefits of the 2012 Banbury scheme
Creates a reservoir
Protects 441 houses
Reduces anxiety
Does not disrupt life
Costs of the 2012 Banbury scheme
Floodplain will be flooded
Costs £11.5 million
180,000 tonnes of soil needed
