erosion
vertical and lateral
hydraulic action
-force of water hitting river bed and banks. Most effective when water is moving at fast and high volume
abrasion
- load carried by river hits the bed/banks, dislodging particles
attrition
- stones carried by the river knock against each other, becoming smaller/more rounded
solution
- alkaline rocks (limestone) are dissolved by slightly acidic river water
drainage basin
the area of land drained by a river and its tributaries
- source- start of river
- tributary- small stream that joins larger river
- confluence- where a tributary joins a larger river
- watershed- the edge of a river basin
- mouth- end of a river where it joins the sea
cross profile
upper course
valley: steep-sided, V-shaped
river: narrow, shallow, turbulent
middle course
valley: wider, flat floor
river: wider, deeper
lower course
valley: very wide, flat
river: wide, deep, large load
transportation
load: material transported by a river
- solution- dissolved load
- suspension- small sediments held in the river
- traction- large particles rolled on riverbed
- saltation- ‘bouncing’ of particles too heavy to be suspended
deposition
when a river’s velocity decreases and it no longer has the energy to transport its load
large rocks carried by traction are carried short distances at high flow and are deposited in the upper course
smaller sediment carried by suspension further downstream is deposited on the bed where velocity slows due to friction
lots of deposition occurs at a rivers mouth where velocity reduces because of the gentle gradient/interaction with tides
interlocking spurs
- mountain stream erodes vertically creating V-shaped valley
- winds around areas of resistant rock to create inter-locking spurs which jut out into the valley
waterfalls
- river crosses boundary between hard rock and soft rock
- soft rock is more easily eroded so is eroded downwards
- undercutting of softer rock by hydraulic action and abrasion
- hard rock overhang collapses into plunge pool
- waterfall retreats
gorges are narrow, steep-sided valleys found downstream of a retreating waterfall
meanders
bends in a river found in lowland areas
-fast flow on outside curve of the bend causes more erosion(river cliff)
- slower flow on inside curve of bend causes deposition (slip-off slope)
ox-bow lakes
- as meanders migrate across valley floor, they start eroding towards each other
- neck of meander gets narrower
- neck gets broken through and forms a straighter channel
- old meander loop is cut off by deposition to form an ox-bow lake
floodplains and levees
floodplain
- wide, flat areas on either side of a river in its middle and lower course
- created by migrating meanders which erode laterally
levees
- at low flow, deposition raises river bed so channel cant carry as much water
- during flooding, water flows over the sides of channels
- velocity decreases, coarser sediment is deposited first on the banks, then finer sand and mud, raising the level
estuaries
- where the river meets sea
- affected by tides, wave action and river processes
- as the tide rises, rivers cant flow into the sea
-velocity falls and sediment is deposited - mudflats formed which develop into salt marshes
river tees
North-East England and its source is the Pennine Hills
flows towards the North Sea at Middlesborough
High Force waterfall drops 20m- dolerite and limestone
meanders, levees, floodplains
