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60 Cards in this Set
- Front
- Back
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what is the ecological value of coastal processes? |
high biodiversity |
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what is the social value? |
people live on coastal areas recreational uses transportation |
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economic values |
food supply flood protection massive tourist attraction |
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why are coastal processes at risk? |
utilised by humans as we dont manage them correctly sea level rise climate change pollution eutrophication storms huricanes ecosystem system destabalisation |
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what effect the future sea level? |
Tidallevels (MHWS, HAT)· Stormsurges |
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how can we manage coastal processes correctly? |
need to understand the physical process betwee tides and wind) sediment sources (beach material) and the coast profile to come up with a plan for coastal zone management. |
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what is a wave? |
propogating oscillation with transport of energy - no transport of mass. moves only in cicles |
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why may there still be some transport of mass in a wave? |
some mass is transported. |
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how are coasts protected from coastal erosion? |
· Harddefences· Down-driftproblems· Softand flexible defences· Managedrealignment |
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what energy can be used from the coast? |
· Conventionalenergy · Nuclearpower · Renewableenergy |
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how is wave speed measured? |
wavelength/ wave period. |
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what can cause waves? |
gravity and waves |
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what generates long period of waves? |
storms and earthquakes. |
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how is the energy transferred in wind waves? |
from wind to water |
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what conditions do you need for wind to be transferred to water |
strong enough wind speed wind to be blown enough and a long fetch for the wind to blow over |
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how deep are deep water waves? |
greater than the waves length. |
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what happens when they propogate closer to the shore? |
they become shallower waves (water depths is less than 5% of the wave length ) |
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how are coasts formed? |
by energy and material input |
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what do waves do in deeper waters? |
follow circular orbits |
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what happens to the radius of the circles with depth? |
it decreases |
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what is wave celerity dependent by ? |
the bottom |
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what happens to wave particles in shallow water? |
follow elloptical orbits (orbids become flatter and flatter) |
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what happens to the wave celerity |
square root of g*water depth |
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how do you calculate wave celerity ? |
wave length/ period = square root if g + depth |
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what happens at shallower water very shallow water and shoaling? |
slower waves very shallow water- distortion (crest moves faster than the rest of the wave) higher waves |
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why is there friction at shallower water? |
because the wave touches the bottom which is rough |
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what happens when energy is lost? |
wave disappears everything slows down. |
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what happens at wave distortion |
wave troff slows down more than the crest |
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what are the key factors to shallow water wave modification? |
shoaling, refracting, breaking (defracting and reflection) |
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what happens during shoaling |
wave speed decreases, the wave period stays the same due to conservation energy the wave length then decreases to keep a constant wave speed volume of wave increases due to the transfer of the same volume of energy |
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what happens as the footprint of the wave decreases? |
the wave height increases to keep the same energy (conserve it) |
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when waves enter shallow water why do they break? |
wave becomes so step it cannot support its own wait and therefore collapses (very short and very high) the speed of the water around the crest is of the wave exceeds the wave speed so the water in the crest over tales the wave form and causes it to fall over and break |
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what is wave refraction? |
Bending of waves because of varyingwater depths underneath |
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what causes refraction? |
Thepart of a wave in shallow water moves slower than the part of a wave in deeperwater. Thewave crest in deeper water catches up so that the wave crest tends to becomeparallel to the shore. |
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what is wave diffraction? |
propagation of a wave around anobstacle. (tip of the obstacle scattersincoming wave in all directions ànoisebehind the obstacle) |
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what is wave reflection? |
waves“bounce back” from an obstacle (e.g.shoreline; harbour ) they encounter. |
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what does the proportion of the wave bouncing back depend on? |
The proportion of incoming wavesreflected back from the beach depends on beachslope (mild slope practically no reflection. Steeperprofiles (e.g. cliff) = more reflection;Given same slope, longer waves arereflected more (beach appears steeper to longer waves than to shorter waves)) |
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what are tides? |
waves caused by gravitationalinteractions between Earth, Moon and Sun, and are ALWAYS SHALLOW WATER waves |
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how long are they? |
hundreds of kms |
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why do tides form? |
because of the attraction between the earth and the moon. the sun effect less than the mood because the mood is a lot closer |
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how does the earth cause tides? |
Moon’sgravity pulls ocean water toward the moon, Thenearth rotate and in this way tides occur in different places of earth and a balance etween gravitational attraction and centrifugal acceloration |
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how does the mood rotate? and what does this mean? |
•does not rotate around the earth’sequator, but follows an orbit that is inclined in relation to the earth’s axis.Because of this, northern and southern latitudes commonly face only one hightide and one low tide in a day, called diurnal tides. |
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why are there complex patterns? |
largecontinents on the planet block thewestward passage of the tidalbulges as the Earth rotates |
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what effects do spring tides have on tides? |
make high tides higher and low tides lower |
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what effects do neap tides have? |
makes high tides lower and low tides higher |
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how does the sun modulate the amplitude of the tide? |
spring tide happens as the sun is in line with the moon |
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what type of waves are tides? |
always shallow water waves. |
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what is the differents between tides and waves entering shallower waters? |
the wave is longer |
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what happens when an estury/ bay is closed ? |
the tide is reflected back |
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what happens IFestuary/ bay is the right depth and length? what do you need to have a resonance? |
reflectedtide perfectly overlapincoming tide RESONANCE you double the tide natural period of the basin = to the natural periods of the tides |
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what happens in shallow water to the speed trough and crest in respect to tidal range? |
speed crest>> spreed trough |
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what happens to the speed trough and crest in deep water? |
speed trough= the crest |
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what is a storm surge? |
abnormal rise of water generated bya storm, over and above the predicted astronomical tides greatest threat for coastal area during hurricanes |
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what causes horizontal action? |
water pushed toward the shore bythe force of the winds moving cyclonically around the storm |
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what causes vertical action? |
Pressure: Lowpressure =higher water level |
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what causes a hurricane? |
warm oceans cause evaporation of warmmoist air which raise and leaves area low pressure aroundsurface the surrounding air goes to replace this vacuum which causes New air becomes warmer and rises aswell. inthe mean time Earth rotate-everythingstart rotating -cyclones (e.g. hurricanes |
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how are tropical storms different to cyclones |
travel fast and powerful wind stress is much higher in respect to pressure. |
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what do you need to have a extratropical storm? |
it is big, moves slowly action of pressure is the same as wing |
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what is a tropical storm? |
•small,very intense gyres•generated at sea•unpredictable track•very high surges:•e.g. Hurricane Camille, 1969 surge >6.0m•windstress >> pressure |
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extratropical storms: |
•large,slow moving•surround a depression•considerable duration•pressure≈ wind effect |
