RIVERS Flashcards
name 3 river processes
erosion
transportation
depostion
deine erosion
breaking down of sediments by rivers’ energy
4 types of erosion
- hydraulic action (force of water removes sediments from river banks and beds)
- abrasion (pebbles grind along a rock platform and becomes smooth)
- attrition (pebbles knock against each other and becomes smaller in size)
- solution (river dissolves rock)
name four types of transportation
- traction (roll)
- saltation (bounce)
- suspension (float)
- solution (dissolve)
talk about depositon
happens when river energy is lost (ie deceased velocity and volume)
–> large sediments are disposed of first as they require most energy to carry.
6 key principles of the bradshaw model?
- width and depth increases
upstream: high GPE, vertical erosion
downstream: low GPE, horizontal erosion, widening the channel - velocity increases
amount of water touching riverbanks decrease downstream, less friction faster movement of water - discharge increases
- velocity increases
-volume increases (more tributaries) - gradient decrease
- load amount increase
- load size decreases
define discharge
volume of water passing through a specific point at a specific time
name 3 upper course landforms
- V-shaped valleys
- interlocking spurs
- waterfalls and gorges
explain how V-shaped valleys form
-high GPE upstream, vertical erosion, steep sides
-weathering and mass movement steeepens sides
explain how interlocking spurs form
- low river energy upstream (low velocity low volume)
river cannot erode bands of hard rock so it bends around it
explain how waterfalls and gorges form
- soft rock eroded quicker than hard rock, forming a STEP
- erosion continues, hard rock is UNDERCUT, forming an OVERHANG
- abrasion and hydrualic action forms a plung pool
- size of overhang increases until hard rock COLLAPSES under gravity
- waterfall TREATES, eroding asteep-sided gorge into the landscape
define waterfall
sudden drop along the river course
name 2 middle course land forms
meanders and oxbow lakes
explain how meanders form
–> outer bend:
high velocity, high energy, erosion, deeper, forming RIVER CLIFFS
–> inner bend:
low velocity, low energy, deposition, shallower, forming POINT BARS
Explain how oxbow lake forms
- erosion makes neck of meander narrow over time
- during floods, rivers ERODE THROUGH the neck of rivers through ABRASION and HYDRAULIC ACTION
- after flood, river loses energy, deposition occurs, ISOLATING former meander as oxbow lake
name two lower-course landforms
- flood plains
- leeves
talk about floodplains
floodplains are areas of FLATLAND on the sides of the river that is covered during floods
- lateral erosion flatterns sides of channel
- deposition during flooding makes up the floodplains
talk about leeves
leeves are RAISED BANKS of rivers found along floodplains
- after flooding, river energy decreases
-river deposits sediments through sorting; big and heavy elements that require lots of energy to carry are deposited first, followed by smaller sediments
define flooding
when volume of water inside river exceeds channel capactiy
talk about the lag time
lag time is the time between the peak rainfall and peak discharge
the shorter the lag time, the more likely it is for the river to flood as WATER IS REACHING THE RIVER MORE QUICKLY
rank the different ways of water entering the river in terms of their rate
precipitation
drains
surface runoff
infiltration
groundwater
name and explain two physical causes of flooding
- intense rainfall
soils and rocks become satuated, increasing surface runoff, which is a quick way for precipitaion to enter the river - relief
RAPID TRANSFER of water towards river channels
name and explain 3 human causes of flooding
- deforestation (trees roots absorb water)
- farming (land is ploughed, water flows quickly through furrows)
- urbansiation (concrete roads faciliate rapid surface runoff// water enters rivers quickly through drains)
define hard engineering
major construction work to alter natural processes
two types of hard engineering and their pros&cons
- dams and reservoirs
:) HEP/ long lasting
:( expensive/ affect wildlife (salmon cannot go upstream) - channealisation (deepen, widen ad straighten river
:) sense of security
:(visually unattractive/ increase chance of flooding downstream
soft engineering
working WITH natural proccesses to MINIMISE their impact
suggest two types of soft engineering and their pros & cons
- flood plain zoning (control land use)
- washlands (flood plains reserved for floods)
:) minimise risk of damaging human life and property
:( evacuation/ impossible for areas with high population density/ captical cities
geographical advantage of river wye
- flows between tintern and chepstow
- marks the border between England and Wales
how human activies affect the landscape of river wye
- industry (quarrying to extract limestone steepens gorge)
- forestry (widespread planting of conifers resulted in varying rates of interception between growing and harvesting seasons)
