Water On The Land Flashcards
What are the 4 processes of transportation?
Traction- large boulders move across the bed due to the force of water
Saltation- small particles Bounce along the bed due to the flow of water
Suspension- particles are carried by the flow of water
Solution- particles dissolved in the water
Deposition is when a river drops its eroded material
This occurs when the river slows down
Why does a river lose velocity?
Volume of water in a river decreases
The amount of eroded material increases
The water is shallower (inside of a bend)
The river reaches its mouth
What is a slip off slope?
Deposited material on the inside of a river
How do slip of slopes form?
The current flows faster on the outside of a bend as it’s deeper and less friction
The current is slower on the inside as the river is shallower and there is more friction
So eroded material is deposited in the area with less energy
How are Oxbow lakes formed from meanders
Middle/lower course
1) erosion causes the outside Bends to get closer
2) this continues to happen until there’s a small bit of land between the two meanders called a neck
3) the river breaks through the neck usually by a flood, the river flows along the shortest course
4) deposition eventually cuts off the meander, forming an oxbow lake.
How do waterfalls form?
Upper course
An area of land is separated by hard rock and soft rock.
The channel is able to erode the soft rock creating a step. The soft rock continues to erode until it forms a steep drop called a waterfall
How does a gorge form from a waterfall?
Upper course
The hard rock becomes undercut by erosion, becoming unsupported and collapses.
The collapsed rock swirls around at the foot of the waterfall and erode the soft rock by abrasion in a plunge pool.
Over time, more undercutting will take place, causing more collapses and the waterfall will retreat leaving behind a steep sided gorge
What is a flood plain and what happens to them when they flood?
Flood plains= wide valley floors on either side of a river which occasionally gets flooded.
As the river floods it loses energy, making it slow down, this causes material to be deposited, building up the flood plain
Meanders move across the flood plain making it wider
What are levees?
Natural embankments on either side of the river,
As eroded material is deposited over the whole flood plain, the heaviest material is deposited closest to the river channel as it requires more energy to carry larger boulders. Over time the material builds up preventing floods
E.g. Yellow river, China
What are contour lines?
What do they show?
They tell you the height of land in meters by the numbers marked on them.
They also tell you the steepness by how close they are together.
A river flows from higher contour lines to lower ones
Contour lines meet at a river (perpendicular)
Maps:
What symbol is evidence for a cliff?
Black blocky lines
What is river discharge?
The volume of water that flossing river per second
Draw a hydrograph What is meant by: The rising limb Peak Discharge Lag time Falling limb
Rising limb- the increase in discharge as rainwater flows into the river
Peak discharge- the highest discharge during a period of time
Lag time- the delay between peak rainfall and peak discharge, this happens as most of the water doesn’t directly go into the river, e.g. Surface run off/infiltration
Falling limb- the decrease in discharge as the river discharge reverts to its normal level.
What are the 4 processes of erosion?
Hydraulic action- the force of the water breaks away parts of the bed
Abrasion- eroded rocks scrape and rub against the channel
Attrition- eroded rocks smash into each other to form smaller fragments with rounded edges
Solution- river water dissolves some of the rock
What happens to the discharge as run off increases?
The more water that flows as run-off the shorter the lag time
This is because more water gets into the channel in a shorter space of time
