CHAPTER 7: Shorelines and Coastal Processes

Emergent and Submergent Coastlines
Causes of changes =>  short term =  tides and storms
 in sea level                                      ______________

                                     Long term: ______________
                                                      isostatic push after glaciation
     Ice melting from the polar areas   rise in sea level

Wave cut platforms:step like surface cut in rock by waves at the water surface level as a  result of____________________________________  or ____________________________.

              surface of each wave cut platform  => = old water level
                                                                               edge of continent
  Repeated process =>  coastline in step-like terraces

Drowned valleys: How do they form?
 
 
 

 Fjords = ____________________valleys filled with sea water

Sea level trend: rise (1/3 m every 100 years)
     Problems = flat lands ==> flooding and retreat
           made worse by greenhouse effect   more polar melting

Beach
 
 

Waves:  Origin? __________________________________________
 

Motion of water molecules: Rise and fall in circular orbits that become smaller with depth.

Wavebase:  level below which water motion is negligible

Breakers: Formed when shallowing bottom _____________________ with water orbits.

Cliff Erosion:

direct: pounding of breakers
indirect: abrasion or________ = grinding erosive effect of sand, pebbles and cobbles propelled by waves

Jutting points of land or headlands = more pounded than recessed bays

Wave refraction:  deflection of waves around irregularities, breakers' energy is concentrated towards headlands.

Storms and Coastal Erosion
Storm surge                         low air pressure  =>       bulge in water
                                            onshore winds                unusually
                                                                                   high tides

•   Outwash of the berm (gently sloping portion of beach above high-tide line)
•   Beginning of erosion on dunes and/or cliffs beyond

Strategies to limit cliff erosion
 unsuccessful + costly  => temporary solutions
    Seawall = solid wall of concrete
     Riprap = pile of blocks or debris.
Erosion continues around barriers, below them or can be diverted to unprotected cliffs nearby.

    Breakwaters = structures parallel to shorelines located offshore

    Beach replenishment (Miami)
 

Sand transport and beach erosion
 Longshore currents =          result from waves approaching the shore at an angle -

•  net movement  => parallel to shore
• effect:  move seds. from one end to other of the beach.

Flood control dams:
  cut off sediment supply for beaches near the mouth => beach erosion -
Replenishment?              costly
environmentally sound? duplicate mineralogy & size
 

Difficult environments = shore erosion avg: 1.5-4.5 ft/year
Barrier Islands?
 
 

 origin :  longshore currents on delta sands, moved them along the coastline and deposited them in a long narrow band.
 tendency: retreating inland (higher energy on seaward side) 2m/year (ATLANTIC USA)

 Effect on shores? ____________________________
 
 

 Highly developed    <= scenic features

  Temporary                     * add beach sand
   measures  of                  * breakwaters                              Costly and  hopeless
  shoreline                        * groins
  stabilization

Tendency in government policy? _______________________________  in risky areas.

Estuaries                         body of water along coastline
                                       tide rises and fall
                                       mixture of fresh and saltwater =>  brackish water
                                       lower ends of stream valleys (drowned)

Location: tidal flats

Organisms: adapted to the particular salinity of the estuary
                   restricted water circulation   pollution from cities
                   life: specific to the site, vulnerable and fragile

Land reclamation from estuaries = by filling and pumping water out
Zuider Zee, Netherlands: example of estuary transformed into real state.
 

CHAPTER 7: Shorelines and Coastal Processes
REVIEW QUESTIONS:
1)  Draw a beach profile naming its different portions.
2)  Explain the development of breakers close to the shore.  Wave base.
3)  Which areas along the shoreline are more affected by erosion? Explain. Relate to wave refraction.
4)  Effect  of storms on shorelines. Where do you find erosion and where deposition of sediments?.
5)  Advantages and disadvantages of the different types of structures designed to cope with coastal erosion.
8)  Effect of longshore currents a) in areas where protective structures have been built. b) in areas left undeveloped.
7)  How and why do wave-cut platforms form?. Contrast with drowned valleys and fjords.
8)  Does shoreline gradient have any influence in the effect of small rises in the sea level. Yes, no, why?
10) How do barrier islands generally evolve through time?. Why?
11) Why are estuaries considered difficult environments?
12) Outline the methods to recognize coastal hazards.
13) Write 5 meaningful multiple choice questions on shorelines and coastal processes. Provide the correct answer. Questions must have at least 4 choices (or 5 choices if you use "all of the above" or "none of the above").