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An introduction: to support AS Geography (Edexcel B)
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Channel processes and featuresValley slope processes and
landforms
RIVER STUDIES
Satellite view of river drainage, Middle East
Microscale drainage basin
Upper valley characteristics
Upper valley characteristics
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hillslopes
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hillslopes
Terracettes formed by soil creep
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hillslopes
Terracettes formed by soil creep
Narrow, shallow channel, low velocity and discharge
Upper valley characteristics
“V”shape valley, vertical erosion dominant
Interlocking spurs
Slumping and landslides - very active hillslopes
Terracettes formed by soil creep
Narrow, shallow channel, low velocity and discharge
Large bedload derived from upstream and from valley sides
Interlocking spurs, Robinson, Lake District
A typical upper course valley with interlocking spurs, steep valley sides and active slope processes
Choked runnel, N. Pennines
Ephemeral stream or runnel - water present only during high rainfall events
Choked runnel, N. Pennines
Debris brought downslope towards channel - dropped when water disappears after storm
Ephemeral stream or runnel - water present only during high rainfall events
Choked runnel, N. Pennines
Debris brought downslope towards channel - dropped when water disappears after storm
Ephemeral stream or runnel- water present only during high rainfall events
Vertical erosion creating steep, bare slopes vulnerable to further erosion - an example of positive feedback in a slope system
River load in upper course
Load is dumped in summer due to the low discharge unable to carry the c________ and c__________ of load at higher flow levels
River load in upper course
Load is dumped in summer due to the low discharge unable to carry the capacity and competence of load at higher flow levels
River load in upper course
Load is dumped in summer due to the low discharge unable to carry the capacity and competence of load at higher flow levels
River load in upper course
Boulders are large and semi-rounded, due to attrition within the load and abrasion with the stream bed and banks
Load is dumped in summer due to the low discharge unable to carry the capacity and competence of load at higher flow levels
Rapids in the Upper Tees Valley
Rapids in the Upper Tees Valley
Rapids are mini-waterfalls
Protruding bands of more resistant strata create steps over which rapids fall - the river bed is ungraded
Rapids in the Upper Tees Valley
Rapids are mini-waterfalls
Protruding bands of more resistant strata create steps over which rapids fall - the river bed is ungraded
Shallow, slow flowing river due to large amount of friction.
Rapids in the Upper Tees Valley
Rapids are mini-waterfalls
Protruding bands of more resistant strata create steps over which rapids fall - the river bed is ungraded
Shallow, slow flowing river due to large amount of friction.
Wetted perimeter is large compared to cross sectional area of water - resulting in a low ????????????
Rapids in the Upper Tees Valley
Rapids are mini-waterfalls
Protruding bands of more resistant strata create steps over which rapids fall - the river bed is ungraded
Shallow, slow flowing river due to large amount of friction.
Wetted perimeter is large compared to cross sectional area of water - resulting in a low hydraulic radius (low efficiency)
High Force waterfall, R. Tees
High Force waterfall, R. Tees
Huge step in river bed due to igneous intrusion of dolerite into the limestone.
High Force waterfall, R. Tees
Huge step in river bed due to igneous intrusion of dolerite into the limestone. Plunge pool where the dolerite wall is undercut, causing rockfalls and recession of the waterfall upstream
High Force waterfall, R. Tees
Huge step in river bed due to igneous intrusion of dolerite into the limestone.
Waterfall creates gorge as it recedes upstream by eroding the base and neck
Plunge pool where the dolerite wall is undercut, causing rockfalls and recession of the waterfall upstream
High Force waterfall, R. Tees
Huge step in river bed due to igneous intrusion of dolerite into the limestone.
The long profile will be graded over time
Waterfall creates gorge as it recedes upstream by eroding the base and neck
Plunge pool where the dolerite wall is undercut, causing rockfalls and recession of the waterfall upstream
Headward erosion, Offa’s Dyke
This is amazing!!
Headward erosion, Offa’s Dyke
Spring erodes ground over which it flows and lubricates base of cliff, causing slumping and headward erosion
Headward erosion, R. Colorado
Headward erosion, R. Colorado
River seeps out from spring at base and undermines steep cliff, causing rockfalls and headwall recession
Headward erosion, R. Colorado
Rivers erode in a headward direction, eating back into plateauRiver seeps out from spring at base and undermines steep cliff, causing rockfalls and headwall recession
Potholes in R. Wharfe
Smooth sculpturing of rock by abrasion, showing evidence of water levels during high discharge events
Vertical erosion is dominant
Close-up of potholes
Close-up of potholes
Close-up of potholesCircular potholes due to eddying motion when river energy is high
Close-up of potholesCircular potholes due to eddying motion when river energy is highPotholes will join together by abrasion, and deepen by vertical erosion
Close-up of potholesCircular potholes due to eddying motion when river energy is high
Load is picked up and used to scour or abrade pothole. Load itself becomes rounded by attrition
Potholes will join together by abrasion, and deepen by vertical erosion
Potholes, human scale!!
Middle course, R. Tees
Middle course, R. Tees
Valley opens out, more gentle slopes, wider valley bottom
Middle course, R. Tees
Valley opens out, more gentle slopes, wider valley bottomFirst signs of meanders
Middle course, R. Tees
Valley opens out, more gentle slopes, wider valley bottomFirst signs of meanders
Floodplain
Middle course, R. Tees
Valley opens out, more gentle slopes, wider valley bottomFirst signs of meanders
Floodplain
River channel wider, deeper, greater velocity and discharge
Meander, R. Lavant, Chichester
Meander, R. Lavant, Chichester
Floodplain
Meander, R. Lavant, Chichester
FloodplainPoint bar deposits on the inner meander bend where there is low energy
Meander, R. Lavant, Chichester
Floodplain
Steep bank known as the river bluff or cliff, caused by concentrated erosion due to the
Point bar deposits on the inner meander bend where there is low energy
Meander, R. Lavant, Chichester
Floodplain
Steep bank known as the river bluff or cliff, caused by concentrated erosion due to the thalweg
Point bar deposits on the inner meander bend where there is low energy
Meander, R. Lavant, Chichester
Floodplain
Steep bank known as the river bluff or cliff, caused by concentrated erosion due to the thalweg and
Point bar deposits on the inner meander bend where there is low energy
helicoidal flow
Meander, R. Lavant, Chichester
Floodplain
Steep bank known as the river bluff or cliff, caused by concentrated erosion due to the thalweg and
Point bar deposits on the inner meander bend where there is low energy
helicoidal flow
pool
riffle
pool
Pools develop at meander bends and riffles in the stretches between bends
Meander on the R. Colorado
Meander on the R. Colorado
Meander incised into plateau due to rejuvenation
Meander on the R. Colorado
Meander incised into plateau due to rejuvenation
Different strata show evidence of past climates or hydrological events
Meander on the R. Colorado
Meander incised into plateau due to rejuvenation
Different strata show evidence of past climates or hydrological events.
Stratum with large boulders must have formed in wetter conditions when higher river discharge carried a greater competence of load
Migrating meanders, R. Gongola, Nigeria
Migrating meanders, R. Gongola, Nigeria
Former course marked by white sediments
Current channel is braided
Lower Severn Valley
Lower Severn Valley
Well developed meanders with bars in the channel indicating high sediment load
Very wide floodplain
Very gentle valley side gradients
River terraces, R. Agri, S. Italy
River terraces, R. Agri, S. Italy
River has been rejuvenated causing renewed vertical erosion - base level has dropped either due to rising land or falling sealevel
River terraces, R. Agri, S. Italy
Flat terraces represent former floodplains
River has been rejuvenated causing renewed vertical erosion - base level has dropped either due to rising land or falling sealevel
Flooding in the Severn Valley
Flooding in the Severn Valley
Floodplain can be mapped into risk zones high to low
Flooding in the Severn Valley
Floodplain can be mapped into risk zones high to low
Floods can be beneficial - they renew soil fertility by depositing sediment on floodplain
Flooding in the Severn Valley
Floodplain can be mapped into risk zones high to low
Floods can be beneficial - they renew soil fertility by depositing sediment on floodplain
Floods result in large amounts of sediment transported in the channel
Padstow estuary
Estuaries are tidal, dominated by marine sediments
At low tide, mudflats are exposed
Alluvial fan, Buttermere, Lake District
Alluvial fan, Buttermere, Lake District
Alluvial fan, Buttermere, Lake District
Lake Buttermere acts as a local baselevel for the stream, leading to deposition of load in a triangular shape - an alluvial fan
This is the same process that forms major deltas at the coast e.g. R. Nile
Braided river, Swiss Alps
Braided river, Swiss Alps
Braided river, Swiss Alps
Daytime snowmelt in summer produces flashy regime
Vast amounts of sediment supplied from frost-shattered valley sides
Braided river, Swiss Alps
Daytime snowmelt in summer produces flashy regime
Vast amounts of sediment supplied from frost-shattered valley sides
Channel course can change daily due to changes in discharge and loose sediments
Summary of channel characteristics
(1) Processes
Summary of channel characteristics
(1) ProcessesErosion
Corrasion Attrition Solution Hydraulic
action
Headward Vertical Lateral
Summary of channel characteristics
(1) ProcessesErosion
Corrasion Attrition Solution Hydraulic
action
Transport
Suspension Solution Bedload
- traction- saltation
Headward Vertical Lateral
Summary of channel characteristics
(1) ProcessesErosion
Corrasion Attrition Solution Hydraulic
action
Transport
Suspension Solution Bedload
- traction- saltation
Deposition
Headward Vertical Lateral
Summary of channel characteristics(2) Landforms
Summary of channel characteristics(2) Landforms
•Rapids
•Waterfall
•Pothole
Summary of channel characteristics(2) Landforms
•Rapids
•Waterfall
•Pothole
•Meander
•Bluff/cliff
•Point bar
•Pool
•Riffle
Summary of channel characteristics(2) Landforms
•Rapids
•Waterfall
•Pothole
•Meander
•Bluff/cliff
•Point bar
•Pool
•Riffle
•Knick point
•Braids
•Alluvial fan
•Delta
Summary of channel characteristics
(3) Concepts and technical terms
Summary of channel characteristics
(3) Concepts and technical terms
•Discharge
•Regime - flashy - regular
•Capacity
•Competence
Summary of channel characteristics
(3) Concepts and technical terms
•Discharge
•Regime - flashy - regular
•Capacity
•Competence
•Hydraulic radius
- cross sectional area
- wetted perimeter
Summary of channel characteristics
(3) Concepts and technical terms
•Discharge
•Regime - flashy - regular
•Capacity
•Competence
•Hydraulic radius
- cross sectional area
- wetted perimeter
•Long profile
•Graded profile
•Rejuvenation
•Base level
Summary of channel characteristics
(3) Concepts and technical terms
•Discharge
•Regime - flashy - regular
•Capacity
•Competence
•Hydraulic radius
- cross sectional area
- wetted perimeter
•Long profile
•Graded profile
•Rejuvenation
•Base level
•Thalweg
•Helicoidal flow
•Meander migration
Summary of valley characteristics
Summary of valley characteristics
Upper Slumps Landslides Terracettes (soil
creep) I nterlocking spurs “V” shaped valley
Summary of valley characteristics
Upper Slumps Landslides Terracettes (soil creep) I nterlocking spurs “V” shaped valley
Middle Wider valley Gentler valley sides Floodplain Meanders
Summary of valley characteristics
Upper Slumps Landslides Terracettes (soil creep) I nterlocking spurs “V” shaped valley
Middle Wider valley Gentler valley sides Floodplain Meanders
Lower Widest part of valley Terraces