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water as open system
the amount of water in a single drainage basin can vary, as it inputs and outputs
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river processes
erosion
this is the wearing away of landscape by the action of ice, water and wind
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solution
this is the form of chemical erosion. the banks and bed of the river are absorbed by acids in the water
attrition
material is moving along the bed, collides with material and breaks into smaller piecies
hydraulic action
this is the force of water hitting the banks of the rivers. it wears them away and causes them to collapse
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deposition
this is laying down or dumping of material it happens when a river slows and loses its energy
this may be during a dry spell on the inside of a river bed or when they reach the sea
land forms
meanders
As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.
The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy due to decreased friction. This will form a river cliff.
On the inside of the bend, where the river flow is slower, material is deposited, as there is more friction. This will form a slip-off slope.
Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through, e.g. during a flood when the river has a higher discharge and more energy, and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake.
waterfall formation
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The erosion processes of hydraulic action, abrasion and attrition will work together to erode the rock – causing the waterfall to start to move backwards and leave a steep-sided gorge.
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impacts of flooding
on environment
positive impacts
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in dry areas, floods bring relief from drought, providing drinking water for wild animals
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on people
poisitive impacts
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can encourage innovative solutions in future building design, such as building houses on stilts to avoid floodwater, or tiling all ground floor walls and floors to facilitate easy clean up after flooding
negative impacts
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can increase house insurance costs for householders, or even make it impossible for them to insure their home at all
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river drainage basin
key terms
drainage basin of the river is the area around the river that drains the river and all its tributaries
a tributary of a river is a stream that flows into the main river
the source of a river is where it begins, the starting point of the river, this maybe a marsh or glacier
mouth is where the river ends at sea, ocean or lake
watershed this is the boundary between one drainage basin and another (usually seen on the landscape by a ridge of higher land
confluence is the point where two rivers meet
hydro logical cycle
the water cycle also known as the hydro logical cycle is a closed system in which water is continually recycled between land sea and air
key terms:
evaporation is the change of liquid into a gas called water vapour
condensation is when water droplets cool and condense to form
surface runoff is when water in the form of river returns to the sea
interception is when the leaves on the trees catches the rainfall
infilteration is the downward movement of water through the soil
permeable is when water can soak through the soil
though flow is the sideways flow of water through the soil
groundwater is an under store of water
groundwater flow is when water flows horizontally along the rock and back into the sea
key terms:
surface storage is water that is stored on the surface of the land in puddles, lakes and channels
soil store is where water is stored in the soil
percolation is the movement of water from the soil into bedrock
transpiration the evaporation of water from plants and vegetation
river is carrying water to the sea
formation of floodplains and leeves
levee
When a river overflows in the lower course the coarsest/heaviest material is deposited first. This builds up the ridges called levees. This is because energy is reduced due to increased friction or slower velocity.
floodplain
area of wide flat land alongside the river channel that get covered in water when the overflows its bank, leaving behind a fine muddy which is called alluvium, silt and sediment. floodplains have rich fertile soil because of this alluvium and makes them good for farming
bluff, floodplain, levee, river channel