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Geography (River Lanscapes (Long and Cross profiles (Both vary over course…
Geography
River Lanscapes
Transportation
Traction, large particles are pushed along the river bed
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Suspension, small particles i.e silt and clay are carried by the river
Solution, soluble materials like chalk and limestone dissolve in the water and are carried along
Depostion, when a river drops eroded material. It happens when a river slows down
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Hydraulic, the force of the water breaks particles away from the river channel
Abrasion, eroded rocks picked up by the river scrape and rub against the channel wearing it away
Attrition, eroded rocks smash into each other and create smaller fragments their edges get rounded off as they do this. The further they travel the more eroded they get, attrition causes particles size to decrease between the source and mouth of a river
Solution, river water dissolves some types of rocks
Long and Cross profiles
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Shape of valley and channel changes along the course of the river depending on whether erosion or deposition is having the most impact
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Cross profile shows you what the cross section of the river looks like. Vertical and lateral erosion changes its shape
Vertical and lateral erosion happen at the same time, although one is usually dominant at different points on the river. Vertical erosion deepens the river channel, tends to be dominant in the upper course where high turbulence causes rough angular particles rub along the bed causing intense vertical erosion. Lateral erosion widens the river valley and channel, during the formation of meanders it is dominant in the middle and lower course
River landforms
Upper course
Waterfalls , Gorges, Interlocking spurs,
In the upper course the erosion is vertical which creates V shaped valleys. The rivers aren't powerful enough to erode laterally so they must wind around high hillsides, the hills that interlock are called interlocking spurs.
Middle course
Meanders
Rivers develop large bends called meanders in the middle and lower courses, there are both shallow and deep sections in the channel. The current is faster at the outside of the bend because the river is deeper and there is less water to slow the river down more erosion takes place here which forms river cliffs. Current is slower on the inside because the channel is shallower, more deposition occurs here forming slip-off slopes
Ox-Bow lakes are formed from meanders, as they get larger they become cut off from the main channel and form a lake
Lower course
Meanders, floodplains, levees, estuaries
Floodplains are the wide valley floor which occasionally gets flooded. When a river floods onto a floodplain the river slows down and deposits the material the river was carrying, this builds up the floodplain making it higher. Meanders migrate across the floodplain making it wider. The deposition that occurs on the slip-off slopes also build up the floodplain
Levees are natural embankments along the edges of a river, during a flood eroded material is deposited but the heaviest material is dropped closest to the river, this stacks up and forms a levee
Estuaries are tidal areas where the river meets the sea. Land is close to the sea, the river valley is close to sea level. The area is tidal and water floods over the banks carrying silt and sand onto the valley floor
Physical Factors
Prolonged Rainfall, the soil becomes saturated and further rainfall cant infiltrate
Heavy rainfall, rain falls too rapidly for infiltration
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Relief, water reaches river slower of faster depending on the gradient of the land
Human Factors
Land use, deforestation or urbanization can reduce interception and increase flood risk
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Coastal Landscapes
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Transportation/Deposition, material is deposited along coasts by a process called longshore drift
Waves follow the direction of the prevailing wind and hit the coast at an oblique angle. The swash carries material up the beach in the the same direction of waves. The backwash carries it back at right angles and over time the material zig-zags down the coast
Mass movement, the shifting of rocks and loose material down a slope
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Types of waves
Constructive
They are created in calm weather and are less powerful than
destructive waves. They break on the shore and deposit material, building up
beaches.
They have a swash that is stronger than the backwash.
They have a long wavelength, and are low in height.
Destructive
Destructive waves are created in storm conditions.
They are created from big, strong waves when the wind is powerful and has been blowing for a long time.
They occur when wave energy is high and the wave has traveled over a long fetch.They tend to erode the coast.
They have a stronger backwash than swash.
They have a short wave length and are high and steep.
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