Coastal Hazards NDTest2

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Coastal Hazards NDTest2
2013-11-11 09:24:48
natural disasters

test 2
Show Answers:

  1. What are waves caused by?
    offshore winds producing friction over water
  2. What determines the size of waves?
    • speed of wind
    • duration of wind
    • fetch (distance wind blows over water surface)
  3. When do waves become sorted into groups?
    as they move away from their origin
  4. How do you determine wave height?
    distance from crest to trough
  5. How do you determine wavelength?
    distance from crest to crest
  6. How do you determine wave period?
    time between crests
  7. What kind of motion do waves have?
    • circular in the open ocean
    • decrease in diameter with increasing depth
    • become ellipses in shallow water
  8. What are wave sets generated by storms?
  9. How do swells work?
    enter shallow water, become unstable and break
  10. Where do waves lose their energy?
    trying to reach the coastline
  11. What is a single wave called?
    a wave front
  12. What can cause variations in wave height as it approaches shore?
    irregularities in topography
  13. How are beaches formed?
    • loose material accumulates by wave action on the shoreline
    • white(shell and coral)
    • black(volcanic rock)
    • brown(quartz and feldspar)
  14. What is considered the onshore portion of the beach?
    landward extent of a beach on seashore or lakeshore
  15. What are the different types of onshore beaches made from?
    • line of sand dunes
    • line of permanent vegetation
    • sea cliff or bluff (formed from erosion of rock/sediment)
  16. What is the berm?
    • beach portion that slopes landward
    • formed by deposition of sediment by waves
  17. What is the beach face?
    • beach portion that slopes toward the water
    • in the swash zone
  18. What makes up the beach offshore?
    • swash zone
    • surf zone
    • breaker zone
  19. What is the swash zone?
    where waves swash and backswash on the beach
  20. What is the surf zone?
    where turbulent waves move after waves break
  21. What is the breaker zone?
    • where waves become unstable, peak, and break
    • longshore bar forms beneath breakers
    • longshore trough forms landward from bar
  22. What is the eustatic sea level?
    the global sea level
  23. What is the eustatic sea level affected by?
    changes in the amount of water in oceans
  24. What can change the eustatic sea level?
    • temperature increases (cause volume of water to expand)
    • temperature decreases (cause ice to form on land, taking water away from the ocean)
    • change of the shape of the ocean basin
  25. What is the relative sea level?
    location of the sea at shoreline
  26. What can cause the uplifting of land?
    • glacier melt
    • earthquakes
    • causes a decrease in sea level
  27. What can make relative sea level rise or fall?
    rates of deposition, erosion, or subsidence
  28. What causes daily and seasonal changes in the relative sea level?
    tides caused by the gravitational pull of the moon
  29. What can also cause changes in relative sea level?
    • winds
    • storm surge
  30. What are rip currents? How do they develop?
    • currents that move away from shore
    • develop when waves pile up water between longshore bar and swash zone
  31. What does beach erosion involve?
    beach budget
  32. What makes up the beach budget?
    • input-sediments brought from upshore (local erosion of dunes/cliffs)
    • output-sediments being carried away from shore (storm waves, on-shore winds)
    • storage-sediment on the beach
  33. When does the beach grow? erode?
    • input exceeds output
    • output exceeds input
  34. What causes cliff erosion?
    • wave action
    • running water
    • landslides
    • all cause cliffs and bluffs to retreat
  35. Do humans add to cliff erosion?
    yes by increasing surface run off, increasing groundwater discharge, and adding weight to cliffs
  36. How can cliff erosion be monitored?
    using LIDAR
  37. What are the effects of coastal processes?
    • rip currents
    • beach erosion
    • cliff erosion
  38. How do you minimize the effects of costal hazards?
    with stabilization
  39. What is hard stabilization?
    creating structures meant to protect the shoreline
  40. What is soft stabilization?
    • adding sand to depleted beaches
    • beach nourishment
  41. What are some types of hard stabilization?
    • seawalls
    • groins
    • jetties
    • breakwaters
  42. What are seawalls?
    • built parallel to shoreline
    • vertical design reflects waves and redirects energy to shore
    • promote beach erosion
  43. What are groins?
    • built perpendicular to shoreline, usually in groups
    • traps sand from longshore drift
    • cause increased erosion in donwdirft area
  44. What are jetties?
    • built in pairs perpendicular to shoreline near river or inlet
    • designed to keep channel open
    • cause increased erosion and deposition in other locations
  45. What are breakwaters?
    • built parallel to shore
    • intercept waves to protect boats/ships in harbor
    • block littoral transport, increasing erosion and deposition in different locations
  46. What is beach nourishment?
    • adding sand to replace sand that has eroded
    • aesthetically preferable to hard stabilization
    • temporary solution
    • sand must be chosen carefully to match conditions at beach