Coastal Geography, Beach-dune System

Question 1

Why are beaches so resilient to erosion?

Answer 1

Beaches exist because they are adaptable/malleable. They accomodate wave energy

Question 2

Landward limit

Answer 2

The end of where water runs up the coast

Question 3

Seaward limit

Answer 3

Where waves encounter the seafloor

Question 4

What are the five main components of a beach-dune system?

Answer 4

The berm, beach face, runnel/ridge, low tide terrace, trough/longshore bar

Question 5

Berm

Answer 5

A nearly horizontal ridge formed by swash deposition

Question 6

Beach face

Answer 6

The swash/backwash zone

Question 7

Runnel/ridge

Answer 7

Runnel: A drainage route for tides on the low tide terrace

Ridge: The raised area flanking either side of the runnel

Question 8

Low tide terrace

Answer 8

A flat, extensive part of the beach composed of fine sand that becomes exposed at low tide

Question 9

Trough/longshore bar

Answer 9

Trough: A deep part of the beach that is submerged even at low tide

Longshore bar: The top of the trough

Question 10

Sand dunes

Answer 10

A temporary mound of sand that forms on the beach from desposited sediment

Question 11

What happens to sand dunes during storms?

Answer 11

The sand is eroded and deposited offshore, usually returning during calmer weather

Question 12

What are the two types of beach profiles and their implication for the transport of sediment?

Answer 12

Steep profile: Sediment transported and deposited onshore

Flat profile: Sediment transported and deposited offshore

Question 13

What are the two main controls of beach profile?

Answer 13

Sediment and wave energy

Question 14

What three parts of sediment influence the beach profile?

Answer 14

Sediment size, percolation, and angle of repose

Question 15

How does sediment size influence beach profile?

Answer 15

Finer sediment will result in a flatter beach while larger, coarser sediment will result in a steeper beach

Question 16

Percolation

Answer 16

The rate at which water will pass through sediment

Larger sediment = Greater percoation

Question 17

How does percolation influence beach profile?

Answer 17

Both well sorted sand and poorly sorted sand with pebbles results in a flatter beach gradient

Contrarily, well sorted pebbles result in a stepper beach gradient

Question 18

Angle of repose

Answer 18

The angle at which loose material can maintain a slope

Question 19

How does angle of repose influence beach profile?

Answer 19

A lower angle of repose (sand) results in a flatter beach gradient

Contrarily, a higher angle or repose (gravel and pebbles) results in a steeper beach gradient

Question 20

What are the two types of wave energy and what types of beaches do they form?

Answer 20

High wave energy: Forms a dissipative beach. Dissipates wave energy

Low wave energy: Forms a reflective beach. Reflects wave energy

Question 21

What are the characteristics of a dissipative beach?

Answer 21

High energy, flat gradient, wide surf zone, small/fine sediment, spilling waves

Question 22

What are the characteristics of a reflective beach

Answer 22

Low energy, steep gradient, narrow surf zone, large/coarse sediment, surging waves

Question 23

In realtion to sediment sorting, what is the relationship between energy and time?

Answer 23

More energy + More time = Better sorting

Question 24

What two conditions change beach profiles

Answer 24

Summer (swell) conditions and Winter (storm) conditions

Question 25

What are the five main characteristics of Summer (swell) conditions

Answer 25

Regular waves, onshore sand transport, beach construction, berm-build up, and a steep beach gradient

Question 26

What are the five main characteristics of Winter (storm) conditions?

Answer 26

High storm waves, offshore sand transport, beach erosion, longshore bar accretion, and low beach gradient

Question 27

What are bars and how do they form?

Answer 27

Bars are areas of sediment convergence while troughs are areas of sediment divergence

Question 28

Why do bars migrate?

Answer 28

In high wave events, bars migrate offshore due to increased erosion Contrarily, in low wave events, bars migrate onshore due to increased deposition

Question 29

Why does beach erosion occur during storm conditions?

Answer 29

Under storm conditions, more sediment is eroded and transported offshore as backwash remains onshore for a longer period of time

Question 30

Storm surge

Answer 30

A combination of wind set up (strong winds) and pressure set up (low pressure), causing MSL to rise

Question 31

Constructive waves

Answer 31

Low energy waves with a weaker backwash that deposits more sediment. Occurs during Summer (swell) conditons

Question 32

Destructive waves

Answer 32

High energy waves with a stronger backwash that erodes ad transports more sedimentl. Occurs during Winter (storm) conditions