# EESB18H3 Lecture Notes - Surf Zone, Dune, Breaking Wave

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10 Nov 2010
School
Course
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
ī Crest
ī Trough
o Wave height, length and period depend on
ī Wind Speed
ī Length of time wind blows
ī Fetch ī distance wind travels
o As wave travels, water passes energy along by moving in a circle
ī At a depth of about one-half the wavelength, the movement of
water particles becomes negligible (wave base)
ī 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 ī Wave sets generated by storms far out at the sea
ī Any wave that has traveled out of its area of origination
o Rouge Waves ī When series of similar-size waves meet and coalesce
o Changes that occur when a wave moves onto shore
ī As wave touches bottom of shore the bottom of the wave
begins to slow down while the top of the wave rīīīīīīīīīīīīĆÆīī
original speed.
ī 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
ī Wave refraction
x Bending of a wave
x Wave arrives parallel to shore
x Results
o Wave energy is concentrated against the sides
o Wave erosion straightens an irregular shoreline
ī Point furthest out on coast will be hit first resulting in most
wave energy being used to erode cliff.
ī 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
ī With Wave Shoaling
x Length Decreases
x Height Increases
x Wave Steepness increases
ī Types of breaking waves
x Plunging Breakers ī Steep beaches, very erosive
x Spilling Breakers ī Wide, gently sloping, sandy beaches
ī Great energy dissipation
ī Shoreward mass transport of water
ī Turbulent water created by breaking waves is called surf
ī Swash (Up beach) ī Moves up slope of the beach
ī Backwash (Down beach) ī Flows back down the beach toward
the surf zone
o Beach Form
ī Composed of whatever material is available (bits of shell/coral,
fragments of basalt, rier sediments)
ī Gravel ī high energy, steep beaches
ī Sand ī gently sloping, lower energy beaches
ī 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 ī a buffer protected sea cliffs and coastal properties
from intense wave action & erosion
o Sand Transport
ī 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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