Channel processes and features Valley slope processes and landforms RIVER STUDIES Channel processes and features Valley slope processes and landforms
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 Terracettes formed by soil creep Interlocking spurs Slumping and landslides - very active hillslopes
Upper valley characteristics “V”shape valley, vertical erosion dominant Terracettes formed by soil creep Narrow, shallow channel, low velocity and discharge Interlocking spurs Slumping and landslides - very active hillslopes
Upper valley characteristics “V”shape valley, vertical erosion dominant Terracettes formed by soil creep Narrow, shallow channel, low velocity and discharge Interlocking spurs Slumping and landslides - very active hillslopes 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 Ephemeral stream or runnel - water present only during high rainfall events Debris brought downslope towards channel - dropped when water disappears after storm
Choked runnel, N. Pennines Vertical erosion creating steep, bare slopes vulnerable to further erosion - an example of positive feedback in a slope system Ephemeral stream or runnel- water present only during high rainfall events Debris brought downslope towards channel - dropped when water disappears after storm
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 Shallow, slow flowing river due to large amount of friction. 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 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 ???????????? 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 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) Protruding bands of more resistant strata create steps over which rapids fall - the river bed is ungraded
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 The long profile will be graded over time 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
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 plateau River 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 potholes Circular potholes due to eddying motion when river energy is high
Close-up of potholes Circular potholes due to eddying motion when river energy is high Potholes will join together by abrasion, and deepen by vertical erosion
Close-up of potholes Circular potholes due to eddying motion when river energy is high Potholes will join together by abrasion, and deepen by vertical erosion Load is picked up and used to scour or abrade pothole. Load itself becomes rounded by attrition
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 bottom First signs of meanders
Middle course, R. Tees Valley opens out, more gentle slopes, wider valley bottom First signs of meanders Floodplain
Middle course, R. Tees Valley opens out, more gentle slopes, wider valley bottom First 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 Floodplain Point bar deposits on the inner meander bend where there is low energy
Meander, R. Lavant, Chichester Floodplain Point bar deposits on the inner meander bend where there is low energy Steep bank known as the river bluff or cliff, caused by concentrated erosion due to the
Meander, R. Lavant, Chichester Floodplain Point bar deposits on the inner meander bend where there is low energy Steep bank known as the river bluff or cliff, caused by concentrated erosion due to the thalweg
Meander, R. Lavant, Chichester Floodplain Point bar deposits on the inner meander bend where there is low energy Steep bank known as the river bluff or cliff, caused by concentrated erosion due to the thalweg and helicoidal flow
Meander, R. Lavant, Chichester Floodplain Point bar deposits on the inner meander bend where there is low energy Steep bank known as the river bluff or cliff, caused by concentrated erosion due to the thalweg and pool riffle pool helicoidal flow 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) Processes
Summary of channel characteristics (1) Processes
Summary of channel characteristics (1) Processes
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
Summary of valley characteristics
Summary of valley characteristics