River Landscapes and processes

what is a river course

the path of a river as it flows downhill

rivers form ________ and valleys as they flow downnhill

channels and valleys

what determines the shape of the valley of a river

whether erosion or deposition is the most dominant process

what are the three river courses

upper course

middle course

lower course

upper course

steep gradient, the source area of a river, often in an upland or mountainous region

V shaped valley, steep sides, narrow and shallow channel

middle course

medium gradient ,the section of the river between the mountains and the lowland

gently sloping valley sides, wider, deeper channel

lower course

that part of a river system that is close to the mouth of the river

very wide, almost flat valley, very wide, deep channel

what is the river mouth

the place where a river ends and empties into a larger body of water such as the sea

vertical erosion

Downward erosion of a river bed, this deepens the river valley and channel making it V-shaped. It's dominant in the upper course of the river. The high turbulence causes the rough, angular particles to be scraped along the river bed

lateral erosion

Sideways erosion by a river, widens the river valley and channel causing U shaped valleys. It's dominant in the middle and lower courses

how does freeze thaw weathering break down rocks on the valley sides?

happens when the temperature gets below 0'C, water gets into the rocks that has cracks, freezes and expands. This puts pressure on the rock. When the water thaws it contracts which releases pressure on the rock. Repeated freezing and thawing widens the cracks and causes the rock to break up.

what are the four types of erosion along a river

hydraulic action

abrasion

attrition

solution

hydraulic action

The force of the water breaks rock 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 picked up by the river smash into each other and break into smaller fragments, their edges also round off as they rub together. Attrition causes particle size to decrease between a river's source and its mouth

solution

river water dissolves some types of rock eg. chalk and limestone

what are the four types of transportation

Traction

Saltation

Suspension

Solution

traction

large particles like boulders are pushed along the river bed by the force of water

suspension

small particles like silt and clay are carried along by the water

saltation

pebble sized particles are bounced along the river bed by the force of water

solution (transportation)

Soluble materials dissolve in the water and are carried along

what is deposition

When a river drops eroded material

when does deposition happen

When a river slows down (loses velocity)

what are reasons as to why rivers slow down and deposit material?

1. the volume of the water in the river falls

2. the amount of eroded material in the water increases

3. the water is shallower eg. on the inner bend

4. the river reaches its mouth