Rivers

Question 1

What are the three main parts of a river?

Answer 1

Upper course, Middle course and the Lower course.

Question 2

What is Hydraulic Action?

Answer 2

The sheer force of the water dislodges particles from the river’s bed and banks.

Question 3

What is Abrasion?

Answer 3

Smaller material carried in suspension (like sandpaper) against the banks of the river.

Question 4

What is Corrosion?

Answer 4

When acid in the water dissolves the rocks (such as limestone).

Question 5

What is Attrition?

Answer 5

Boulders and other material are transported along the bed of the river, these collide and break into smaller pieces.

Question 6

Corrosion, Abrasion, Attrition and hydraulic Action are all types of what?

Answer 6

Erosion.

Question 7

What is Traction?

Answer 7

Large rocks and boulders are rolled along the river’s bed.

Question 8

What is Saltation?

Answer 8

Smaller rocks are bounced along the river’s bed.

Question 9

What is Suspension?

Answer 9

Fine material, light enough, is carried along in the flow of the river (giving water its colour).

Question 10

What is Solution?

Answer 10

Dissolved material eroded by corrosion is carried in solution.

Question 11

Solution, Saltation, Traction and Suspension are all types of what?

Answer 11

Transport.

Question 12

What happens when a rivers power is reduced?

Answer 12

The river dumps or deposits its load as it can no longer carry material.

Question 13

When is a river’s power reduced?

Answer 13

-The flow of the river slows: This happen when the gradient of the river bed becomes less steep/more shallow, or when the water flows around thew inside of a bend.
-The volume of water in the river is reduced: This will happen if water is lost to evaporation or percolation.

Question 14

What are some features of the Upper Course of a river?

Answer 14

-Steep Sided ‘V’ Shaped Valley
-Interlocking Spurs
-Rapids
-Waterfalls
-Gorges
P.S. which are all formed by erosion.

Question 15

How is a ‘V’ Shaped Valleys?

Answer 15

-A small stream will naturally follow small depressions in the landscape.
-As the small stream flows downhill steeply, the bedload will erode downwards and scrape away the bottom of the channel (vertical erosion).
-This vertical erosion deepens the valley, making the sides steeper and exposed.
-Over time, weathering and gravity wear away the steep valley sides, forcing material into the stream, which it uses to cut the valley deeper.

Question 16

When rivers get closer to the mouth what happens?

Answer 16

It gets increasingly wider and there are gentle sided valleys.

Question 17

Why does the channel increase in size?

Answer 17

To hold extra water which it receives from its tributaries.

Question 18

What happens in the middle course of the river?

Answer 18

The river starts to erode sideways (laterally) into its bank rather than downwards into its bed (vertically), like it does in the upper course.

Question 19

What happens when rivers flow over flat land?

Answer 19

They develop large bends called Meanders.

Question 20

What is the river beach?

Answer 20

The part of the meander where water flows slowly and deposits material.

Question 21

What is the river cliff?

Answer 21

The part of the meander where water flows quickly and erodes the bank.

Question 22

How is an Oxbow Lake formed?

Answer 22

-Due to erosion on the outside of a bend and deposition on the inside, the shape of a meander will change over a period of time.
-Erosion narrows the neck within the meander.
-In time and usually during a flood, the river will take a new shorter route.
-The new route will be fastest down the middle and therefore deposit material across the old meander.
-In this time, the bend will cut off becoming an Oxbow Lake.

Question 23

What are some Physical causes of floods?