Gcse- Drainage Basin And Rivers

Question 1

What is a drainage basin?

Answer 1

Is an area of land drained by a main river and its tributaries.

Question 2

What does a watershed do?

Answer 2

A watershed separates one drainage basin from another

Question 3

What is drainage density?

Answer 3

Total length of all streams in basin / total area of drainage basin

Question 4

What can drainage basins do?

Answer 4

They can store rainwater, either within river channel or in lakes.

Question 5

What happens to excess water?

Answer 5

It is carried back to the sea via rivers

Question 6

What is constant recycling of water called?

Answer 6

It is called the hydrological cycle. It is a closed system

Question 7

Why is a drainage basin an open system?

Answer 7

Because inputs are- water entering system through precipitation and the outputs- water lost to system through evapotranspiration or vegetation.

Question 8

What is a typical drainage basin system like?

Answer 8

When it rains, water droplets are intercepted by trees. Water is then lost to system through evaporation because rain is light. When rain is heavier, water drops from vegetation to ground. Ground becomes wet and begins to infiltrate. Water will either be stored in soil or transferred downwards.

Question 9

What is infiltration?

Answer 9

Downward movement of water through tiny pores in soil

Question 10

What is the movement of water sideways called?

Answer 10

It is called through flow

Question 11

What is water movement downwards called?

Answer 11

It is called percolation

Question 12

What is the fastest process of water movement?

Answer 12

Surface run-off

Question 13

Where does friction occur in river processes?

Answer 13

Friction occurs at wetted perimeter e.g. Where water comes to contact with river bank and bed.

Question 14

When is friction mostly created in a stream?

Answer 14

When it is full of boulders and rocks. As a result of this water flows slower here than in lowlands.

Question 15

What happens with energy left over from decrease in friction?

Answer 15

It is used to transport material

Question 16

What happens when when river has a great velocity?

Answer 16

It is able to carry a greater amount of material.

Question 17

What is material transported called?

Answer 17

It is called the load?

Question 18

How can load be transported?

Answer 18

In 4 ways-
Traction - along river 
Saltation- along river 
Suspension- within river itself 
Solution- within river itself

Question 19

What does river do with transported material?

Answer 19

Uses it to erode its bank and bed

Question 20

How does river erode?

Answer 20

By 4 processes-
Attrition- boulders are transported along river and collide and break into smaller pieces
Corrosion- when acid in river dissolves rock, like limestone.
Corrasion- smaller material carried in suspension, rub against bank of river. Process is more likely to occur lowland.
Hydraulic Action- when force of river dislodges particles from river banks and bed

Question 21

What does vertical erosion lead to?

Answer 21

Leads to development of steep sided, narrow valley shaped like a V

Question 22

Why are valley sides steep?

Answer 22

Due to soil and loose rock being washed downhill following periods of heavy rainfall

Question 23

What are hill sides known as?

Answer 23

Are known as interlocking spurs, and they restrict view up or down valley.

Question 24

How do waterfalls form?

Answer 24

They form when there is an interruption in the course of the river.

Question 25

How do many waterfalls form?

Answer 25

When river meets band of softer, less resistant rock. Underlying softer rock is worn away more quickly and harder rock is under cut. In time overlying hard rock is unsupported and collapses. After it has collapsed some rock is swirled at times of high discharge to form plunge pool.

Question 26

When do rapids occur?

Answer 26

Occur where layers of hard rock and soft rock are thin, and no obvious break of slope develops in waterfall.

Question 27

What happens as river approaches mouth?

Answer 27

It usually flows over flattened land to develop large bends. Bends are known as meanders.

Question 28

What happened when river reached meander?

Answer 28

Most water is directed towards outside of the bend.

Question 29

What does material do to a meander?

Answer 29

Material erodes the outside of the bank by corrasion.

Question 30

What happens as river looses energy in meander?

Answer 30

It deposits some of its load. Deposited material builds up to form gently sloping slip off slope. Continual erosion on outside bend, results in neck of meander becoming narrower. Neck gets narrower until river cuts through neck. Original meander is blocked off to form of bow lake.

Question 31

How is a floodplain formed?

Answer 31

River widens valley by lateral erosion. At times of high discharge, river has high amount of energy which transports alot of material in suspension. When river overflows, it will spread across flat land. Sudden increase in friction rides water velocity, and silt is deposited. Each time river floods, layer of silt is deposited and flood plain is formed. After this coarsest material is dropped to form a natural embankment called a levee.

Question 32

How is a delta formed?

Answer 32

As river approaches sea, they have energy to carry huge amount of material in suspension. On reaching sea, river crust suddenly gets reduced allowing material to be deposited. Sometimes deposition occurs in main channel and blocks it. River then divides into series of smaller channels called distributaries. Over time, deposited material of sand and silt may build upland to form delta. Deltas form where amount of material bought by river is too great to remove it.

Question 33

What happens with drainage basin mismanagement?

Answer 33

People dispose of their waste in rivers and this cause pollution by-
Source- sewage and water industry accounts for 30% of incidents with surface water outfall combined with sewer overflow.
Type- sewage and oil accounted for half of substained cases, without oil and chemicals being cause major of incidents.