Unit 2 - Dynamic Shorelines Flashcards
What are the six types of coastlines?
Permafrost coasts, Sandy beaches, Rocky beaches, Wetlands and marshes, Cliff-backed beaches, Estuaries
What is the most dynamic part of the beach?
surf zone
Where is the surf zone located?
extends from the breaker zone to the shore
When do waves break in the surf zone?
when water depth is ~1.5x wave height
How do waves in the surf zone break?
Can break as a spilling breaker on low gradient slopes, a plunging wave on moderate gradients, or a surging wave on steep slopes
What occurs during breaking?
waves transform potential energy to kinetic energy, manifesting as wave bore moving shoreward as broken white water
What can happen to currents at the shoreline?
currents can be deflected alongshore and water may return seaward as a rip current
What does a rip current facilitate in terms of water movement?
drives transport between inner shelf and surf zone.
What causes a rip current?
Incoming waves push water toward shoreline, creating imbalance of water piling up in surf zone.
Where is a rip current typically the strongest?
break in sandbar where water seeks path of least resistance back through surf.
What happens to a rip current’s strength after passing through a narrow gap?
It begins to spread out, considerably weakening the velocity and strength of the rip current circulation.
What are fish assemblages in surf zones impacted by?
- intense recreational fishing
- commercial netting
- coastal urbanization
- beach modification
What effects does the environment have on surf zone ecosystems?
direct, but often hard to understand
What happens when broken waves reach the base of the wet beach?
they collapse and run up the beach face as swash in the swash zone
What are other important facts about swash?
Includes uprush and backwash, produces relatively steep seaward sloping swash zone (1 - 20°)
What happens as sediment is deposited in the swash zone?
- can build a berm
- may also contain beach cusps, spaced ~ every 20 to 30 m
What is a berm?
a near horizontal to slightly landward-dipping sand surface, the area where most people sit when they go to the beach
How are beaches classified based on dynamics?
Wave dominated, Tide modified, Tide dominated, Beaches+Rock/Reef Flats
What are some characteristics of dissipative beaches?
A high energy double bar with a 500 m wide surf zone and multiple lines of breakers.
What is the average height of a wave in a longshore bar and trough?
1.5-2 m
Where do longshore bar and trough waves break?
near continuous longshore bar located 100-150m seaward of beach
What is the width and depth of longshore trough separating it from the beach?
50-100 m wide, 2-3 m deep
What are the effects of storms on coastlines?
increased wave action and storm surge
What processes, that typically occur over months/years in coastal zones, are amplified by storms?
Erosion, sediment transport, and deposition
What is coastal erosion?
process by which local SLR, strong wave action, and coastal flooding wear down or carry away rocks, soils, and/or sands along the coast
What is the impact of storm surge on coastline vulnerability?
temporarily raises still water level, leading to erosion.
How does erosion affect the sand in the berm and dune during storms?
moves sand out to sea and into sand bars.
What can a single major storm do to large dune fields?
A single major storm can destroy large dune fields.
How do wave-modified and tide modified beaches differ?
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.
