Paper 1: River Landscapes Flashcards
Hydraulic action
the force of water crashing against the river bed or banks causing material to be dislodged and carried away by the river.
Abrasion
rocks are thrown against the river bed/banks causing more material to be broken off and carried away by the river.
Attrition
rocks are thrown against each other by the river which results in the rocks becoming smaller and rounder
Solution
river water dissolves certain types of rock
Traction
large boulders are rolled across the river bed.
Saltation
Saltation - small pebbles are bounced along the river bed.
Suspension
Suspension - fine light material is carried along in the water.
Solution
minerals are dissolved in the water and carried along in solution.
Why does a river deposit its load?
it no longer has enough energy to transport it anymore.
Load transport in upper course
-Traction is most common
- large boulders have not yet undergone attrition
-can only be rolled
Load transport in lower course
-Suspension is most common
- load is more fine, due to attrition,
-so it floats within the water.
Relief of river in upper course
-very steep
- surrounded by mountainous terrain.
Relief of river in lower course
- flatter
- surrounded by lower-lying hilly valleys.
Cross profile of a river in the upper course
- very narrow
- shallow river channel
- surrounded by v-shaped steep valleys.
-There is little discharge - very little velocity of water
Cross profile of river in the lower course
-the discharge increases,
-the width and depth of the channel increases
- the surrounding valley becomes u-shaped instead.
erosion in middle/lower course
-lateral erosion
-widens channel
causes of flooding
-SRO
-deforestation
-steep relief
-urbanisation
Surface runoff
-water flowing over surface
infiltration
water sinking into soil from grounds surface
soil moisture
water held in soil layer
through flow
-water flowing through soil layer parallel to surface
groundwater flow
-water flowing through rock layer
percolation
water sinking through soil into rocks below
interception
water being prevented from reaching the surface by trees and grass
plant uptake
-water absorbed from soil and rocks by roots of plants
Transpiration
-water lost through pores of leaves in vegetation
Urbanisation causes flooding
-building = impermeable surfaces
-limited infiltration
-more SRO
-shorter lag time
Deforestation
-lack of interception
-more sro
-shorter lag time
steep relief = flooding
gravity causes water to flow downhill fast
-lack of infiltration
-more sro
-shorter lag time
hard engineering eg
-dams/reservoirs
-flood relief channels
-straightening river bends
-building embankments
Soft engineering eg
-flood warnings
-flood plain zoning
-river restoration
-aforestation
flood warnings
sends alerts to local residents
-allows for preparation
-reduces devastation of flood
flood plain zoning
-homes are only built on areas safe from river flood
-closer areas to rivers only permeable surfaces are built = parks
-river restoration
-aforestation
-intercept rainfall
-reduce sro and lag time
dams /reservoirs
-control river flow
-times of high discharge dam is closed
-stores water = prevents flood
straightening rivers
-water flows through specific area quicker
-protecting upstream areas from flood
embankments
-prevents flood
-more discharge in order to burst banks
-banks are higher
Flood relief channels
-at times of high discharge, water is diverted
-reduces discharge of main river
-less likely to flood
hard engineering
-use heavy engineering or use artificial sturctures to prevent river flooding
soft engineering
-works with nature to reduce impacts of flooding
Dams and reservoirs pros (5)
-durable
-hydroelectricity
-can be controlled
-upstream land is fertile
-downstream is protected
Dams and reservoirs cons (5)
-expensive
-damages habitats
-evacuate residents
-disturbs migration
-maintenance
River straightening pros - 2
-reduces flood risk upstream
-water is removed faster
River straightening cons - 4
-less evaporation
-erosion downstream
-river shortened = less space for species
-increase discharge/velocity downstream = flooding
Flood relief channel pros - 2
-reduces discharge
-insurance costs are reduced
Flood relief channel cons - 3
-expensive
-takes up space for farming
-flood near artificial confluence
Artificial embankments pros - 3
-concrete resists erosion
-natural material = habitats
-cheaper
Artificial embankments cons - 4
-deprivation of fishing
-if flood occurs, water cannot reach river again
-needs maintenance
-disrupts ecosystems
Flood warning pros - 2
-gives local preparation time
-reduce impact of flood
Flood warning cons - 2
-doesn’t prevent flood
-only effective if people take action
Flood plain zoning pros - 3
-less damage
-allows impermeable surfaces to be limited around river
-reduces other maintenance
Flood plain zoning cons - 1
limits urban expansion
River restoration pros - 3
-increases biodiversity
-meanders = evaporation
-no further maintenance
River restoration cons - 3
-lengthy process
-expensive
-land needs to be available
Planting trees pros - 4
-binds soil
-intercepts water
-no extra maintenance
-increases biodiversity
Planting trees cons - 4
-long time
-uninhabitable
-takes up space
-less sediment in river = less levees
River Tees - Cow Green Dam advantages (3)
-reservoir holds 40,000m3 of water = supplies industry + leisure/tourism
-new habitat
-hydroelectricity = supports industry + eco friendly
River Tees - Cow Green Dam disadvantages (4)
-discharge levels are reduced = impact on aquatic life
-reservoir took up farming land = compensation was paid
-erosion downstream due to faster flowing water as sediment trapped behind dam instead of being transported/deposited
-less cost effective = maintenance
