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yeah rocks > coastal processes > Flashcards

coastal processes Flashcards

1
Q

tides

A

waves with extremely long wavelengths and periods that travel across the ocean and are modified by the geomorphology of the coastline

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2
Q

Tsunami are tidal waves.

TRUE or FALSE

A

FALSE

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3
Q

everywhere experience equal tides.

TRUE or FALSE

A

FALSE, influenced by location of the ocean basins and position of the land masses

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4
Q

semi-diurnal tide cycle

A

2 similar high and low tides

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5
Q

diurnal tide cyle

A

1 high and 1 low tide per day

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6
Q

on tidal charts, how are different height high tides distinguished?

A

higher high water and lower high water

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7
Q

mixed tide cycle

A

no pattern

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8
Q

most places on earth experience how many neap and spring tides per month

A

2

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9
Q

tidal range

A

difference between neap (lowest low) and spring tide (highest high)

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10
Q

how many days after a spring tide will a neap tide occur?

A

7 days

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11
Q

what is the arrangement of planets in a spring vs neap tide?

A

spring: moon, earth, sun all aligned.
neap: moon 90 degrees to sun and earth

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12
Q

king tides

A

full moon and closest orbit to the earth coinciding. Results in exceptionally high tidal ranges.

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13
Q

king tide and deep low pressure weather system can result in

A

widespread coastal flooding

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14
Q 
tide terminology:
HAT =
MHST = 
MHNT =
MIN HT =
MIN LT =
LAT =
A 
tide terminology:
HAT = high astronomical tide
MHST = mean high spring tide
MHNT = mean high neap tide
MIN HT = minimum high tide
MIN LT = minimum low tide
LAT = lowest astronomical tide
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15
Q

where is the maximum shore width?

A

at HAT and LAT

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16
Q

3 things affecting height, wavelength and period of WAVES

A
  1. wind speed
  2. length of time wind blows
  3. fetch
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17
Q

define fetch

A

distance the wave has travelled across open water

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18
Q

sea state

A

describes the prevailing wave climate

19
Q

3 main types of wave

A
  1. ocean swell
  2. storm waves
  3. nearshore waves
20
Q

at what depth below a wave is the water unaffected by wave energy?

A

half the wavelength deep

21
Q

ocean swell into breakers

A

Ocean swell is created by distant storms in the ocean. The swell generally has a long wavelength and low amplitude. As the swell approaches the coastline, water depth decreases and the wave height increases. As the height increases, the front of the wave steepens due to a speed reduction caused by friction with the seabed. As the wave continues to slow and become nearshore waves they reach shallow water and the oscillation becomes so great that the wave front collapses as breakers. The morphology of a breaking wave is dependent on the nearshore bathymetry

22
Q

plunging breaker vs spilling breaker

A

steep offshore slopes = plunging

gentle slope = spilling

23
Q

storm surges

A

caused by very low offshore pressure systems. Combined with winds makes for a very destructive situation

24
Q

how deep below a wave is the water affected, leading to sediment mobilisation

A

water depth = 2 x wavelength

25
Q

Storm water base (SWB) vs Fair weather wave base (FWWB)

A

SWB is deeper

26
Q

wave refraction

A

angle between swell and submarine contours change so waves break parallel to contours. Concentrate energy and accelerate transport and erosion

27
Q

longshore currents and longshore drift

A

narrow shore-parallel currents as a result of wave refraction. Primary mechanism for sediment transport in the coastal zone = longshore drift. Sediment is moved from one end of a coastal cell to another.

28
Q

sea level rise effect on coastal flooding

A

increases magnitude and frequency of flooding

29
Q

two sea level rising mechanisms

A
  1. eustatic

2. isostatic

30
Q

shoreline erosion

A
  • coastlines are high energy environments
  • high energy erodes and transports sediments
  • major economic hazard
  • trends show its increasing
31
Q

2 coastline subcategories

A
  1. rocky coasts

2. sediment dominated

32
Q

rocky coasts erosion

A
  • erode at slow rates
  • erode due to UNDERCUTTING
  • in weak rocks landslides are a risk
33
Q

engineers can stop coastal cliff recession

TRUE or FALSE

A

FASLE, we can only slow it

34
Q

is coastal cliff regression continuous or episodic?

A

episodic

35
Q

Hard engineering

A

short term and expensive option with high environmental impact

36
Q

hard engineering solutions

A
  • groynes
  • sea walls
  • revetments
  • rock armour
  • breakwaters
  • floodgates
37
Q

Groynes

A

rigid hydraulic structures made of wood, concrete and rockfill, whose purpose is to limit longshore drift.
Create a wide beach on updrift side and prevent erosion on the downdrift side.
Cliffs are protected by the wider beach and are relatively stable.

38
Q

sea walls

A

Sea walls protect the coastline from erosion, but they impede the natural longshore drift.
They have a curved shape which helps dissipate the wave energy. Very expensive to build and maintain

39
Q

breakwaters

A

They are constructed 100-500m offshore and cause the waves to break early. however, erosion is increased downdrift of the structure

40
Q

floodgates

A

protect low-lying estuarine areas from the effects of storm surges.
Most expensive and complex coastal protection structure

41
Q

3 soft engineering interventions

A
  1. beach replenishment
  2. dune stabilisation
  3. managed retreat
42
Q

beach replenishment

A

replace sediment lost by longshore drift and create a wider beach which can absorb more energy and protect the coastline

43
Q

dune stabilisation

A

dunes help dissipate wave energy. They can be stabilised by vegetation, mesh, fences and controlling human activity.

44
Q

managed retreat

A

previously protected areas are allowed to naturally flood and form natural coastal landforms. Restores natural sediment movement dynamics.
Philosophy that coastal erosion is a natural process and to prevent it would be futile.

yeah rocks (16 decks)

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