Unit 2 - Dynamic Shorelines

Question 1

What are the six types of coastlines?

Answer 1

Permafrost coasts, Sandy beaches, Rocky beaches, Wetlands and marshes, Cliff-backed beaches, Estuaries

Question 2

What is the most dynamic part of the beach?

Answer 2

surf zone

Question 3

Where is the surf zone located?

Answer 3

extends from the breaker zone to the shore

Question 4

When do waves break in the surf zone?

Answer 4

when water depth is ~1.5x wave height

Question 5

How do waves in the surf zone break?

Answer 5

Can break as a spilling breaker on low gradient slopes, a plunging wave on moderate gradients, or a surging wave on steep slopes

Question 6

What occurs during breaking?

Answer 6

waves transform potential energy to kinetic energy, manifesting as wave bore moving shoreward as broken white water

Question 7

What can happen to currents at the shoreline?

Answer 7

currents can be deflected alongshore and water may return seaward as a rip current

Question 8

What does a rip current facilitate in terms of water movement?

Answer 8

drives transport between inner shelf and surf zone.

Question 9

What causes a rip current?

Answer 9

Incoming waves push water toward shoreline, creating imbalance of water piling up in surf zone.

Question 10

Where is a rip current typically the strongest?

Answer 10

break in sandbar where water seeks path of least resistance back through surf.

Question 11

What happens to a rip current’s strength after passing through a narrow gap?

Answer 11

It begins to spread out, considerably weakening the velocity and strength of the rip current circulation.

Question 12

What are fish assemblages in surf zones impacted by?

Answer 12

• intense recreational fishing
• commercial netting
• coastal urbanization
• beach modification

Question 13

What effects does the environment have on surf zone ecosystems?

Answer 13

direct, but often hard to understand

Question 14

What happens when broken waves reach the base of the wet beach?

Answer 14

they collapse and run up the beach face as swash in the swash zone

Question 15

What are other important facts about swash?

Answer 15

Includes uprush and backwash, produces relatively steep seaward sloping swash zone (1 - 20°)

Question 16

What happens as sediment is deposited in the swash zone?

Answer 16

• can build a berm
• may also contain beach cusps, spaced ~ every 20 to 30 m

Question 17

What is a berm?

Answer 17

a near horizontal to slightly landward-dipping sand surface, the area where most people sit when they go to the beach

Question 18

How are beaches classified based on dynamics?

Answer 18

Wave dominated, Tide modified, Tide dominated, Beaches+Rock/Reef Flats

Question 19

What are some characteristics of dissipative beaches?

Answer 19

A high energy double bar with a 500 m wide surf zone and multiple lines of breakers.

Question 20

What is the average height of a wave in a longshore bar and trough?

Answer 20

1.5-2 m

Question 21

Where do longshore bar and trough waves break?

Answer 21

near continuous longshore bar located 100-150m seaward of beach

Question 22

What is the width and depth of longshore trough separating it from the beach?

Answer 22

50-100 m wide, 2-3 m deep

Question 23

What are the effects of storms on coastlines?

Answer 23

increased wave action and storm surge

Question 24

What processes, that typically occur over months/years in coastal zones, are amplified by storms?

Answer 24

Erosion, sediment transport, and deposition

Question 25

What is coastal erosion?

Answer 25

process by which local SLR, strong wave action, and coastal flooding wear down or carry away rocks, soils, and/or sands along the coast

Question 26

What is the impact of storm surge on coastline vulnerability?

Answer 26

temporarily raises still water level, leading to erosion.

Question 27

How does erosion affect the sand in the berm and dune during storms?

Answer 27

moves sand out to sea and into sand bars.

Question 28

What can a single major storm do to large dune fields?

Answer 28

A single major storm can destroy large dune fields.

Question 29

How do wave-modified and tide modified beaches differ?

Answer 29

In wave-modified, the surface gravity waves are the main source of energy, compared to tides. In tide modified, the energy from tides is more important than the surface waves.