Presentation on theme: "OCEN 201 Introduction to Ocean & Coastal Engineering Coastal Processes & Structures Jun Zhang"— Presentation transcript:
OCEN 201 Introduction to Ocean & Coastal Engineering Coastal Processes & Structures Jun Zhang Junfirstname.lastname@example.org
Coastal Processes Typical beach profile and coastal zone - Beaches dissipate wave energy and are constantly adjusting to the wave environment (shoaling, wave breaking, sand bar & surf zone, Fig. 4-1, pp80) Littoral Transport (sediment transport) - Long shore transport (parallel to the shoreline, long shore current) - Offshore-onshore transport (perpendicular to the shoreline)
Wave Refraction*, Diffraction & Reflection Wave Refraction: The direction of waves may change when they enter from deep to shallow water or from shallow to deep water. Deep-1 Shallow-2 Shallow-1 Deep-2
Wave direction is normal to the wave crest line Examples of Wave refraction in the costal zone, see pp 117 Fig 4-21 (old Edition: pp 90 Fig. 4-12). Wave direction is normal to shore line. In other words, wave crest-line is parallel to the shore line.
Phenomena of wave shoaling (wave enters from deep water to shallow water) Wave refraction Wave length becomes shorter Wave group velocity is reduced Wave becomes steeper, which leads to wave breaking. Wave breaking leads to the generation of long-shore current. Definition of the surf zone: from the first breaker (due to water depth) to the shore line.
Wave Diffraction: When wave energy is transferred laterally to wave direction, this phenomenon is known as wave diffraction. Wave diffraction occurs when waves passing by a surface piercing body. It may occur in deep or shallow water. An example in shallow water is wave diffraction behind a breaker water. See Fig. 4- 22 at pp119 (old edition Fig. 4-13 at pp93). (internet examples)
Wave Reflection and Transmission: when the water depth suddenly changes, part of the incident wave energy is reflected in the direction opposite to the incident wave direction, part energy continues to propagate (transmit) in the incident wave direction.
Using Fig 4-23 at pp 120 (old edition Fig. 4-14 at pp 94), you may determine the reflection coefficient based upon the surf parameter.
Wave Runup Wave runup is important to the design of the height of coastal structure, such as seawalls and breakwaters.