Rivers

Question 1

Upper course = Gradient: valley and channel shape:

Answer 1

Steep , v-shaped valley , steep sides , narrow/shallow channel.

Question 2

Middle course = Gradient: Valley and channel shape:

Answer 2

Medium , Gently sloping valley sides , Wider deeper channel.

Question 3

Lower = Gradient: Valley and channel shape:

Answer 3

Gentle , very wide almost flat valley , very wide and deep channel.

Question 4

Vertical erosion

Answer 4

• Deepens river valley and channel,making it v-shaped.
• Dominant in upper course.
• High turbulence causes rough angular particles scraping along river bed. Causing downwards erosion.

Question 5

Lateral erosion

Answer 5

• Widens river valley and channel during meander formation.

- Dominant in middle/lower course.

Question 6

Hydraulic action

Answer 6

Force of river water colliding with rocks, breaks rock particles away from river channel.

Question 7

Abrasion

Answer 7

Eroded rocks picked up by river scrape and rub against channel,wearing it away.

Question 8

Attrition

Answer 8

Eroded rocks picked up by river crash into e.o and break into smaller parts. Edges rounded off as rubbed together. Further materials travel,more it is eroded. Attrition causes particle size to decrease from rivers source to mouth.

Question 9

Solution

Answer 9

River water dissolves some types of rock, e.g chalk and limestone.

Question 10

Traction

Answer 10

Large particles pushed along river bed by force of water.

Question 11

Suspension

Answer 11

small particles are carried along by water.

Question 12

Saltation

Answer 12

Pebble-sized particles are bounced along river bed by water force.

Question 13

Solution

Answer 13

Soluble materials dissolve in water and carried along.

Question 14

Deposition

Answer 14

When a river drops eroded material.

Question 15

When does deposition occur?

Answer 15

River loses velocity and energy.

Question 16

Where are waterfalls and gorges found?

Answer 16

Upper course of a river.

Question 17

How is waterfall formed?

Answer 17

1. Soft rock eroded quicker than hard.
2. Hard rock undercut forming overhang.
3. Abrasion and hydraulic action make erode creating plunge pool.
4. Keeps getting bigger until hard rock collapses.
5. Process continues and waterfall retreats upstream.
6. Steep-sided valley left where water fall once was, this is called a gorge.

Question 18

Meanders formed by?

Answer 18

Erosion and deposition.

Question 19

How are meanders formed?

Answer 19

• Current faster on outside of bend because channel is deeper (less friction).
• More erosion takes place outside bend forming river cliffs.
• Current slower on inside of river bend because river channel is shallower.
• Eroded material deposited on inside of bend forming slip-off slopes.

Question 20

How are ox-bow lakes formed?

Answer 20

1. Erosion causes outside bends to get closer.
2. Until small bit of land left between bends (neck).
3. River breaks through land, usually during flood.
4. River flows along shortest course.
5. Deposition cuts of meander.
6. Forming ox-bow lake.

Question 21

Discharge?

Answer 21

Volume of river water flowing per second (cumecs)

Question 22

Peak discharge?

Answer 22

Highest discharge in the period of time you are looking at.

Question 23

Lag time?

Answer 23

Delay between rainfall and peak discharge.

Question 24

Rising limb?

Answer 24

Increase in river discharge as rainwater flows into river.

Question 25

Falling limb?

Answer 25

Decrease in river discharge as the river returns to normal level.