River processes and pressures Flashcards
What is the gradient like in the upper course?
Steep
What is the discharge like in the upper course?
Small
What is the depth like in the upper course?
Shallow
What is the channel shape like in the upper course?
Narrow, steep sides
What is the velocity like in the upper course?
Quite fast
What is the valley shape like in the upper course?
Steep sides
What features are found in the upper course?
Waterfalls, interlocking spurs
What is the gradient like in the lower course?
shallow gradient
What is the discharge like in the lower course?
Very large
What is the depth like in the lower course?
Deep
What is the channel shape like in the lower course?
Flat floor, gentle slopping sides
What is the velocity like in the lower course?
Very fast
What is the valley shape like in the lower course?
Flat, gentle slopping sides
What features are found in the lower course?
Meanders, floodplains, levees and ox-bow lakes
What is the gradient like in the middle course?
Less steep
What is the discharge like in the middle course?
Large
What is the depth like in the middle course?
Deeper than the upper course
What is the channel shape like in the middle course?
Flat, steep sides
What is the velocity like in the middle course?
Fast
What is the valley shape like in the middle course?
Flat, steep sides
What features are found in the middle course?
Meanders and floodplains
What are the four main processes of erosion?
Hydraulic action
Abrasion
Attrition
Solution
What is hydraulic action?
The force of water on the bed and banks of the river removes material
What is attrition?
The load that is carried by the river bumps together and wears down into smaller, smoother pieces
What is abrasion?
Material carried by the river rubs against the bed and banks and wears them away
What is solution?
Some rock minerals dissolve in the river (limestone and chalk) and are carried along in the flow
What are the four main types of transportation?
Traction
Saltation
Suspension
Solution
What is traction?
Large boulders roll along the river bed
What is saltation?
Smaller pebbles are bounced along the river bed, picked up the dropped as the flow of the river changes
What is suspension?
Finer sand and silt particles are carried along in the flow, giving the river a brown appearance
How are waterfalls formed?
More resistant rocks lies over less resistant rock
Less resistant rock is eroded forming a step
More resistant rock is undercut forming an overhang
Overhang is not supported so rock falls into water
Powerful fall of water erodes plunge pool with fallen rocks
Waterfall retreats upstream
How are interlocking spurs formed?
The river naturally flows from side to side, around ridges in valley sides (spurs). These spurs become interlocking with those on the other side of the valley
What are meanders?
Bends in the river’s course
Where are meanders found?
Lower course
Where are waterfalls found?
Upper course
Where are interlocking spurs found?
Upper course