Unit 4 - River Processes and Pressures Flashcards
Name three landforms formed in the upper course
Waterfalls, V shaped Valleys, gorges
Name three landforms formed in the middle course
Meanders, oxbow lake, river beach
Need two landforms formed in the lower course
Floodplains, deltas
What is the river profile
A graph that shows how the weather changes during its journey
What happens during the upper course
There is the river’s source in highland areas as there is more rainfall. The river runs downstream cutting its valley by vertical erosion. The Valleyside it’s a steep and is usually large rocks on the river bed.
What happens during the middle course
Less vertical erosion and more lateral or erosion. Wider and deeper. More lateral erosion where the river cuts meanders
What happens in the lower course
Gentle gradient and the channel is wider. Tributaries s, surface run-off and groundwater have increased the volume of the river
Describe what the river profile looks like
Height on the Y axis. The length of the river from the source along the X axes with a plotted line from top left to bottom right showing the river
What is the Bradshaw model
A diagram showing how characteristics of a river change from upstream to downstream. Triangles are used to show this as they either start wider or narrow and end with the opposite
What is transportation
Rivers move material, Load, downstream from its source to its mouth. There are four types of transportation methods
What is erosion
Rivers wear away their load and the bed and banks of the river channel. There are four processes
What are the four types of transportation
Traction, saltation, suspension, solution
What happens during traction
Large stones are dragged or rolled
What happens during saltation
Smaller stones are picked up and then dropped or bounced
What happens during suspension
Tiny particles of sediment are carried in the rivers current
What happens during solution
Dissolved chemicals are carried along in the solution, invisible to the eye
What are the four types of erosion
Attrition, abrasion, solution and hydraulic action
What is attrition
Rocks and stones where each other away as they knock together
What is abrasion
Sand and pebbles are dragged along the river bed, or knock into it by saltation wearing away the bed
What is solution in erosion
Alkaline rocks such as limestone are dissolved by acidic rainwater
What is hydraulic action
Fast flowing water is forced into cracks breaking up the bank overtime
How are a waterfalls and gorges formed
- There must be a layer of hard rock on top of soft rock and the river must cross it
- The soft rock gets eroded faster by the river. This forms a ledge undercut and overhang and a plunge pool at the bottom
- The ledge collapses as it wasn’t supported into the plunge pool
- This repeats making the waterfall retreat leaving a gorge
How is a V shaped valley formed
The river erodes vertically making the valley like a V.
The steep valley sides are attacked by weathering processes like freeze thaw
The valley sides weaken making them collapse
River valleys may have interlocking spurs, slivers of land that interlock. These are more resistant so it is left behind and the river moves between them
What is velocity
The speed of the river, measured in metres per second
What is discharge
The volume of water flowing in a river, measured in cubic metres per second
How does a meander form
The weather is naturally curved slightly which means the water flows at different speeds in different parts. On the outer edge of a curve it is fastest so it erodes the edge. On the inner edge, it is slow so sediment builds up.
What happens at the outer edge of a river
It is fast flowing so it is eroded. This forms an undercut or a river cliff
What happens at the inner edge of a river
It is slow flowing so sediment carried from the outer edge is the positive here which forms a slip off slope
What are the three types of flow in a river
Inside flow, outside flow or thalweg, helicoidal flow
What is an oxbow lake
When a loop of a meander is left and split from the river
How an oxbow lake formed
The outside of the meander bend which is the neck is eroded more
It is continued to be eroded until only a thin piece of land separates the two channels
The river floods over the neck where it is eroded and the Ariver takes the easier course.
What is a floodplain
A flat area of land that the river spills onto when it bursts its banks
What is a levee
A small raised area of land on the banks of the river made up of sediment. It can be natural or man-made
What is a river delta
When the river deposits its material faster than the sea can remove it
What is estuary
It appears where the river meets the sea
How is a levee formed
During a flood sediment builds up along the banks small ridge. This then continues to grow as more floods happen
What are the three types of deltas
Fan shaped
Cuspate
Birds foot
What is a fan shaped delta
The river splits into many smaller ones to create a fan effect as the river mouth arches out into the Sea
What is a cuspate Delta
The land around the mouth juts out like an Arrow into the sea
What is a birds foot delta
The river splits on the way to the sea and each part juts out into the Sea
Give an example of a fan shaped delta
The Niger delta
Give an example of a cuspate Delta
The Ebro Delta
Give an example of a birds foot delta
The Mississippi Delta
How is a river delta formed
When the river meets slower water, like the sea or a lake, it loses power as it slows down so the sediment being carried is deposited forming the deltas.
What are water stores
Different places where bodies of water are stored
What is most of the earths water
Salt water
What is interception
Water being prevented from reaching the surface by trees or grass
What is infiltration
Water sinking into the soil from the ground surface
What is groundwater flow and through flow.
Groundwater flow is flowing through the rock layer and through flow is flowing through the soil layer
What is percolation
Water seeping deeper below the surface
What is transpiration
Water lost through pores in vegetation
What is the lag time
The peak flow of water time - the peak amount of rainfall
Give three points of a short lag time
Intense rainfall, urban area, high drainage density
Give three points of a long lag time
Gentle Valleyside, forest, low drainage density
What is antecedent rainfall
The amount of moisture already in the ground before a rainstorm
Three causes that make hydrographs look different
Antecedent rainfall, geology, vegetation
