EESB18H3 Lecture Notes - Surf Zone, Dune, Breaking Wave

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Lecture Seven
x Waves
o Energy traveling along the interface between ocean and atmosphere
o Derive their energy and motion from wind
o Waves can travel great distance (> 10000 km)
o Circular orbital motion
o Parts
๎‚ƒ Crest
๎‚ƒ Trough
o Wave height, length and period depend on
๎‚ƒ Wind Speed
๎‚ƒ Length of time wind blows
๎‚ƒ Fetch ๎€‚ distance wind travels
o As wave travels, water passes energy along by moving in a circle
๎‚ƒ Waveform moves forwad
๎‚ƒ At a depth of about one-half the wavelength, the movement of
water particles becomes negligible (wave base)
๎‚ƒ In very shallow water (depth < 0.05L where L = wavelength)
motion at bottom is nearly horizontal (rather than circular)
x Eg: 1 meter long wavelength would be 0.05(1M) = 5cm
o Swell ๎€‚ Wave sets generated by storms far out at the sea
๎‚ƒ Any wave that has traveled out of its area of origination
o Rouge Waves ๎€‚ When series of similar-size waves meet and coalesce
o Changes that occur when a wave moves onto shore
๎‚ƒ As wave touches bottom of shore the bottom of the wave
begins to slow down while the top of the wave r๎‚‡๎‚๎‚ƒ๎‚‹๎‚๎‚•๎€ƒ๎‚ƒ๎‚–๎€ƒ๎‚‹๎‚–รฏ๎‚•๎€ƒ
original speed.
๎‚ƒ The wave speed decreases, and the waves stack up against the
shore. Causing wavelength to decrease and height to increase.
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o Beaches and shoreline processes
๎‚ƒ Wave refraction
x Bending of a wave
x Wave arrives parallel to shore
x Results
o Wave energy is concentrated against the sides
and ends of headland
o Wave erosion straightens an irregular shoreline
๎‚ƒ Point furthest out on coast will be hit first resulting in most
wave energy being used to erode cliff.
๎‚ƒ The main reason behind wave refraction is the different
shoreline resulting in a different deceleration of the waves
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o Breaking Waves
๎‚ƒ With Wave Shoaling
x Length Decreases
x Height Increases
x Wave Steepness increases
๎‚ƒ Types of breaking waves
x Plunging Breakers ๎€‚ Steep beaches, very erosive
x Spilling Breakers ๎€‚ Wide, gently sloping, sandy beaches
๎‚ƒ Great energy dissipation
๎‚ƒ Shoreward mass transport of water
๎‚ƒ Turbulent water created by breaking waves is called surf
๎‚ƒ Swash (Up beach) ๎€‚ Moves up slope of the beach
๎‚ƒ Backwash (Down beach) ๎€‚ Flows back down the beach toward
the surf zone
o Beach Form
๎‚ƒ Composed of whatever material is available (bits of shell/coral,
fragments of basalt, rier sediments)
๎‚ƒ Gravel ๎€‚ high energy, steep beaches
๎‚ƒ Sand ๎€‚ gently sloping, lower energy beaches
๎‚ƒ Material does not stay in one place
x Wave energy moves large quantities of sand parallel
and perpendicular to the shoreline
o Role of beaches ๎€‚ a buffer protected sea cliffs and coastal properties
from intense wave action & erosion
o Sand Transport
๎‚ƒ Movement perpendicular to the shoreline
x Relatively Light (Less energetic waves)
o During summer
o Swash dominates net movement of sand up the
beach face towards the berm (wide berm)
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Document Summary

Lecture seven: energy traveling along the interface between ocean and atmosphere, derive their energy and motion from wind, waves can travel great distance (> 10000 km, circular orbital motion, parts. S trough: wave height, length and period depend on. S fetch distance wind travels: as wave travels, water passes energy along by moving in a circle. S at a depth of about one-half the wavelength, the movement of. In very shallow water (depth < 0. 05l where l = wavelength) motion at bottom is nearly horizontal (rather than circular) N eg: 1 meter long wavelength would be 0. 05(1m) = 5cm: swell wave sets generated by storms far out at the sea. S any wave that has traveled out of its area of origination: rouge waves when series of similar-size waves meet and coalesce, changes that occur when a wave moves onto shore.

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