Rivers

Question 1

What is weathering?

Answer 1

Weathering is the breakdown and decay of rock by natural processes.

Question 2

Name the three types of weathering.

Answer 2

1. Physical (freeze thaw)
   2.Chemical (acid rain)
2. Biological

Question 3

What is freeze thaw?

Answer 3

Freeze thaw is when water enters crack and the water freezes expanding the crack eventually causing rocks to break into smaller pieces

Question 4

What is acid rain?

Answer 4

All rain is slightly acidic

• If the air is polluted it makes the rain more acidic
• The acid rain reacts with weaker minerals causing it to dissolve or decay

Question 5

What is biological weathering?

Answer 5

When roots grow into cracks of rocks causing rocks to split apart.

Question 6

What is mass movement?

Answer 6

The downslope movement of material due to gravity.

Question 7

Name 2 types of mass movement.

Answer 7

1. Soil creep

2.Slumping

Question 8

What is soil creep?

Answer 8

Where individual particles of soil move slowly down a slope due to gravity and collect at the bottom of valley sides.

Question 9

What is slumping?

Answer 9

When bottom of valley side is eroded by a river.

• The material becomes steeper.

-The material above slides downwards rotating as it does so.

-Often triggered by periods of heavy rain.

Question 10

Name 3 MAIN processes that affect a rivers landscape.

Answer 10

1. Weathering
2. Mass movement
3. River erosion

Question 11

Name the 4 types of erosion.

Answer 11

1. Hydraulic action
   2.Abrasion
   3.Solution
   4.Attrition

Question 12

What is hydraulic action?

Answer 12

When the sheer force of water hits the river bed, and banks, wearing them away.

Question 13

What is abrasion?

Answer 13

This is caused by material carried in the river rubbing against the bed and banks of the channel, wearing them away.

Question 14

What is solution?

Answer 14

River water is slightly acidic so it can dissolve some rocks and minerals in contact with the river.

• Limestone and chalk mostly affected

Question 15

What is attrition?

Answer 15

Sediment particles carried in the river collide with each other

• This causes the edges to be knocked off. The continued collision of particles in the river causes them to become rounder and smaller downstream.

Question 16

What are the 4 types of deposition?

Answer 16

1. Traction
2. Saltation
3. Suspension
4. Solution

Question 17

What is traction?

Answer 17

Stones roll along the river bed in the direction of the rivers flow.

Question 18

What is saltation?

Answer 18

Particles the size of sand grains bounce over each other along the river bed.

Question 19

What is suspension?

Answer 19

The water flow carries silt and clay sized particles.

Question 20

What is solution?

Answer 20

The river water dissolves some minerals.

Question 21

What are interlocking spurs?

Answer 21

• Near the source
• Spurs are left interlocking with those from one side of the valley overlapping with the spurs from the other side.

Question 22

How is a waterfall formed?

Answer 22

• When a more hard rock lies over soft rock.

-. River erodes soft rock causing gradually undercutting the hard rock.

• Continued erosion of soft rock causes an overhang of hard rock
• Eventually hard rock cant support its weight and collapses due to gravity.

-Erosion of water and large boulders leads to the erosion of the river bed and forms a plunge pool.

• As soft rock continues to erode the hard rock collapses, a steep sided gorge is formed.

Question 23

What are meanders?

Answer 23

Meanders are bends in a river course, commonly found on a river’s flood plain.

Question 24

How are meanders formed?

Answer 24

• As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
• The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.

Question 25

How is an oxbow lake formed?

Answer 25

- Neck becomes narrower. Eventually the river will erode through the neck. -Water flows through the straight route of the eroded neck. -Deposition at the neck seals of the bend - Gradually begins to dry forming an oxbow lake

Question 26

What are flood plains?

Answer 26

Flood plains is the flat area of land either side of a river especially in its lower course.

Question 27

How is a flood plain formed?

Answer 27

-It is formed by lateral erosion on the outside bends of meanders. -Meaning they migrate across the valley floor and can erode valley sides so they become wide and flat.

Question 28

What are Levees?

Answer 28

Natural embankments of sediment formed along the banks of rivers that carry a large load and occasionally flood.

Question 29

How are Levees formed?

Answer 29

-When it floods, water and sediments come out of the channel as the river overflows its banks. -River loses velocity and energy and deposits larger and heavy sediments on the banks. -Repeated flooding causes banks to get higher forming Levees.

Question 30

What are Deltas?

Answer 30

When a river reaches another body of water, like an ocean, it loses velocity and deposits sediment. If the river deposits sediments fast than it can be eroded. Sediments build up in layers in a fan shaped Deltas.

Question 31

What is a hydrograph?

Answer 31

A hydrograph is a way of showing how a river responds to a rainfall event.

Question 32

Why is flood risk in the UK increasing?

Answer 32

Increasing population - more people are affected by flooding. Changes to land use - urbanisation creates more impermeable surfaces and increases surface runoff rates. Changes to weather patterns - linked to climate change.

Question 33

What are the advantages are disadvantages for having Embankments (Hard Engineering) Embankments - high banks built on or near river banks

Answer 33

Advantages - They stop water from spreading to areas where it can cause problems, for example settlements. Disadvantages- Flood water may go over the top then get trapped behind them. They can burst under pressure

Question 34

What are the advantages and disadvantages of flood walls (Hard Engineering) Flood walls - artificial barriers designed to raise the height of the river banks to hold more water.

Answer 34

Advantages - They prevent water from spreading to areas of high impact like housing. Disadvantages - Expensive to build. They help flood water flow quickly past. They dont look natural

Question 35

What are the advantages and disadvantages of Demountable flood barriers (Hard engineering) Demountable flood barriers - a temporary structure that is only installed when needed.

Answer 35

Advantages - They can be put up and taken down in areas where flood walls could look ugly. Disadvantages - Can only be used in the specific location it has been set to be deployed Risk defence might not be installed in time

Question 36

What are the advantages or disadvantages of flood barriers (Hard engineering) Flood barriers - floodgates built near the river mouth to prevent storm surge or spring tide from blooding area behind the barrier.

Answer 36

Advantages - The gates can be closed when a high tide or surge is forecast. They are able to protect large areas in storm surge conditions. Disadvantages - Construction costs are high and need regular maintenance.

Question 37

What are the advantages and disadvantages of flood plain retention (Soft Engineering) Flood plain retention - strategies to maintain and restore the rivers original land.

Answer 37

Advantages - Allowing rivers to flood helps slow flood waters down and recover river's natural sedimentation processes. Disadvantage - allowing land to flood may mean a change of land use for example change in farm land.

Question 38

What are the advantages or disadvantages of River restoration (Soft engineering) River restoration - Using a variety of strategies to restore the river's original course.

Answer 38

Advantages - Allows rivers to flood but slows them down. Natural rivers are more attractive for recreation and create natural habitats. Disadvantages - Some flood banks often still are needed. Changes in land use may bring some disadvantage.