Coastal Hazards ND Test 2
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What causes waves?
offshore winds producing friction over water
What does the size of waves depend on?
- wind speed
- wind duration
- fetch (distance wind blows over water surface)
How do waves move?
become sorted into groups as they move away from the origin
What is wave height?
distance from crest to trough
What is the wave length?
distance from crest to crest
What is the wave period?
time between crests
How do waves move?
- circular in open ocean
- circle diameter decreases as depth increases
What is a single wave called?
What are the onshore regions of beaches?
- landward extent of a beach
- line of sand dunes, permanent vegetation, sea cliff or bluff
- divided into two categories
What are the offshore regions of beaches?
- swash zone
- surf zone
- breaker zone
How are onshore regions classified?
- berm: beach slopes landward, formed by deposition of sediment by waves
- beach face: beach slopes toward water, located in swash zone
What is the swash zone?
where waves swash and backswash on the beach
What is the surf zone?
where turbulent waves move after waves break
What is the breaker zone?
- where waves become unstable, peak, and break
- longshore bar forms
- longshore trough forms from bar
What is eustatic sea level?
- global sea level affected by amount of water in oceans
- climate increases/decreases the amount of water
- tectonic processes change the volume of the ocean basin
What is the relative sea level?
location of the sea at the shoreline
How does the relative sea level change?
- weather conditions (wind & storm surges)
- glacier melting (uplifts land)
- daily and seasonal tide changes
What are the effects of coastal processes?
- rip currents
- beach erosion
- cliff erosion
What are rip currents?
- currents that move away from the shore
- develop when waves pile up between longshore bar and swash zone
- concentrated in narrow zones
What is beach erosion?
- input- everything brought in
- output- what waves carries back out
- storage- everything left on the beach
What is cliff erosion?
- erode due to wave action, running water, and landslides
- cliffs and bluffs begin to retreat
- human activity increases erosion rate
What is hard stabilization?
- structures meant to protect shoreline
- groins, jetties, break waters
What is soft stabilization?
adding sand to depleted beaches (beach enrichment)
What do breakwaters do?
protect ships in harbors from waves
What do jetties do?
keep the channel open
What do groins do?
trap sand from longshore drift
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