Unit 1C- River Landscape In The UK Flashcards
What is the valley and channel shape of the upper course?
V-shaped Valley steep sides
Narrow, shallow channel
What is the valley and channel shape of the middle course?
Gently sloping valley sides
Wide, deepchannel
What is the valley and channel shape of the lower course?
Very wide, almost flat valley
Very wide, deep channel
What is the difference with vertical and lateral erosion?
Vertical- High turbulence causes the rough particles to be scraped along the river bed, causing downwards erosion.
Lateral- Widens river valley and channel during the formation of meanders. In the middle and lower courses.
What are 4 reasons why rivers slow down and deposit material?
The volume of water falls
The amount of eroded material increases
The water is shallower e.g. on the inside of a bend
The river reaches its mouth
What are flood plains?
The wide valley floor on either side of a river, which occasionally floods. Deposition of material that has been transported builds up the floodplain.
How are levees created?
During a flood the heaviest material is deposited closest to the river channel, because it gets dropped first when the river slows down and loses energy. Over time, the deposited material builds up.
How are mudflats created along estuaries?
When the water floods over the banks of the river, it carries silt and sand into the valley floor as the tide reaches its highest point, the water moves slowly, and has little energy, so it deposits sediment. Overtime, more mud builds up.
How can you tell the height and steepness of land using contour lines?
Height- numbers marked on them
Steepness- how close together the lines are (closer lines mean a steeper slope)
How do waterfalls and gorges form?
Softer Rock is eroded more than the hard rock creating a step in the river.
This erosion is repeated, creating a steep drop which is a waterfall.
The hard rock is eventually undercut by erosion, it becomes unsupported and collapses.
The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion and this creates a deep plunge pool.
Over time, the waterfall retreats, leaving behind a steep-sided gorge
What are interlocking spurs?
The hillsides that interlock with each other as the river winds around them
How are meanders formed?
Faster current on the outside bends (deeper) means more erosion, creating river cliffs.
Slower current on the inside bends (shallower) means eroded material is deposited, creating slip-off slopes.
How are ox-bow lakes formed?
Erosion on the outside bends creates a small bit of land between them- called the neck
When the river breaks through, due to flooding, the river flows along the shortest course
Deposition cuts off the meander forming an ox-bow lake
What is the peak discharge?
The highest discharge in the period of time you’re looking at
What is lag time?
The delay between peak rainfall and peak discharge
What is rising limb?
The increase in river discharge as rainwater flows into the river
What is the falling limb?
The decrease in river discharge as the river returns to its normal level
What are four physical and human factors that affect flood risk?
Heavy rainfall
Geology (rock type)
Prolonged rainfall
Relief (changes in land heights)
What is an advantage and disadvantage of channel straightening?
Adv- Water leaves the area more quickly
Dis- flooding may happen downstream instead
What is an advantage and disadvantage of flood relief channels?
Adv- Gates means the release of water can be controlled, reducing flood risk
Dis- increased discharge where the relief channel rejoins the river
What is an advantage and disadvantage of river restoration?
Adv- little maintenance
Dis- local flood risk can increase
