River Landscapes Flashcards
Vertical erosion
Occuring in the upper course this erosion makes a vshape and deepens the course . Due to high turbulence it causes rough and sharp angular rock to be scraped downwards causing intense erosion
Lateral ersion
Dominant in the middle and lower course. This erosion widens the channel sides
River eden
North west england
Upper course is full or hard rock there fore the valley is steep sided due to vertical erosion . Channel is narrow leading to little discharge and its slow velocity due to the friction caused by the rough sea bed and channel sides
Middle course made from less resistant rock which is eroded by the river leading to lateral erosion . The velocity increases as friction decreases as the channel is wider and deeper .
Lower course. Valley sides are wide and flat . High velocity due to reduced friction . Very large discharge as it joins the two other rivers caldew and perreti . Material is fine and in particles transported by solution and suspension
Traction
Large boulders of sediment rolls around on the river bed
Saltation
Pebble sized sediment bounces along the river bed
Why does deposition occur
Volume of water falls
Speed reduces
Water gets shallower
River reaches mouth
Waterfall formation
Occurs when hard rock is followed by soft rock
Soft rock erodes quicker than hard rock creating a step in the river
As water goes over the step it erodes eventually a steep drop occurs
Hard rock collapses due to erosion
Collapsed rock swirls around eroding softer rock creating a plunge pool
More undercutting occurs. Waterfall retreats and gorge is formed
Interlocking spurs
In the upper course of a river most of erosion is vertical
Creates v shaped valleys
Rivers cannot erode it there fore they go around it winding through
The hillsides that interlock look like a zip as the river winds around them
Formation of meander
Current flow is faster on the outside bend than it is on the inner.
Hydraulic action and abrasion take place outside of the bend forming river cliffs
Current is slower on the inside bend than the outside so sediment is deposited there forming a slip off slope.
Formation of oxbow lake
Erosion cause the bends to get closer until there is a small bit of land separating them called a neck
River breaks through this land during a flood and river flows the shortest course deposition cuts off the meander forming and oxbow lake
Levees
During a flood eroded material is deposited over the whole flood plain
Heaviset material is deposited closest to the river channel as the river slows down . Over time material builds up creating levees along the edge of the channel
What is a delta
Rivers are forced to slow down when meeting a lake. If the deposited material isnt eroded the material will block up the channel forcing the river to form distubitaires
Eventually material builds up so much that low lying areas of land form
How does physical factors effect sediment and river landscape
Climate
Rivers in wetter climate have a high discharge . Increases rate of erosion , adds more sediment to river load. Therefore transportaion increases . Colder climates also have increased weathering which can increase the amount of sediment in the rivers
Geology
Rive flowing through hard rock slows rate of erosion reducing sediment load. Landscapes with harder rock have steeper valley sides. Waterfalls occu with hard and soft rock.
Slope processes
Mass movemnet can add huge amounts of sediment to the river load . Mass movemnets more likely to occur in wetter or colder times
Soil creep can also add to the river load
What factors affect hydrographs
Geology
Hard rock increases surface runoff
Soil type more impermeable soil cannot absorb as much water . Surface runoff increases and vice versa
Slope . Steeper slope less infiltration more surface run off
Draigane basin type
Circular types have a shorter lag time and a higher discharge . Narrower basins water takes a long time to reach the main channel
Colder conditions can freeze surfaces and increase surface runoff
Deforestation
Urbanisation
Why is river eden prone to flooejng
Milder and wetter climates
Increased impermeable surfaces
Snowfall is common . Water melts and reaches channel in a shorte time
Building on flood plain has effected the ability to absorb water
Drainage ditches due to places being repurposed for farminh means water reaches channel faster
STORM DESMOND
BLOCKAGES
INSUFFICIENT DRAINAGE
