Presentation is loading. Please wait.

Presentation is loading. Please wait.

Wave Dominated Coasts Objective: to examine some of the processes and characteristics active on a wave-dominated coast.

Similar presentations


Presentation on theme: "Wave Dominated Coasts Objective: to examine some of the processes and characteristics active on a wave-dominated coast."— Presentation transcript:

1 Wave Dominated Coasts Objective: to examine some of the processes and characteristics active on a wave-dominated coast

2 Weathering & Erosion What is? Weathering: Breakdown of rock (Geology) to form sediment in situ Weathering is a set of physical, chemical and biological processes that alter the physical and chemical state of rocks and soil at or near the earth's surface. Rock and soil is altered physically by disintegrating and chemically by decomposing. Nearly all weathering involves water, mostly directly: frost shattering, wetting and drying, salt weathering, and all chemical weathering is in solution. That is, weathering is climatically driven and thus the term weathering. Because weather and climate occur at the earth's surface, the intensity of weathering decreases with depth and most of it occur within less than a metre of the surface of soil and rock. Erosion: Transport of weathered material from one location to another... The wearing away of land or the removal of beach and/or dune sediments by wave action, tidal currents, wave currents, drainage, or wind. Erosion includes, but is not limited to, horizontal recession and scour and can be induced or aggravated by human activities.

3 Wave Dominated Coasts Coasts are exposed to the elements Open to the sea Little shelter from waves Waves erode the coastline Waves move rocks/sediment Wave energy Erosion + Sediment Transport

4 Wave Energy Wave Energy is typically HIGH Cliff erosion, formation, maintenance, remobilisation of sediments Fine sediments generally absent Depositional areas include: sands, shingles - beach forms Longshore currents (action of waves) leads to movement of sediment Q. What happens when wave energy is low? A. Refashion beach profile

5 Waves Constructive or Destructive Accretion versus Removal Seasonal Waves are generated by wind, gravity (tides) and? Waves classified into: capillary waves, gravity waves (wind), infra-gravity waves (interaction), long-period waves (tidal) Wave form moves not the water Depth of water shallows closer to the coast, causing waves to break at the surf line - frictional drag causing top of wave to break over bottom Point at which wave touches bottom leads to sediment pick up and transfer Calm versus storm conditions Seismic activity

6 Angle of wave approach to coast leads to refraction Bays and Headlands - hard versus soft rock - differential erosion More erosive power on headlands than bays or embayments Spatial wave gradients due to differential wave activity lead to development of longshore currents and sediment movement Development of edge waves (secondary waves) can amplify the impact of waves at the coast rather than usual dissipation of energy Waves

7 parallel wave fronts concentrated wave energy on headland reduced wave energy in embayment refracted wave fronts Wave Refraction

8 Beaches Beaches often refashioned rather than removed on high energy coast Beaches tend to dissipate energy - natural coastal defence Depends on materials making up the beach Water running up a beach will return by throughflow or surface flow (dependent on materials) determining sediment removal/transport Beaches and dunes are sediment stores Wave approach angle: Swash and Backwash Sediment moved up, down and along the shore Shore parallel, nomal and rip currents Circulation cells formed leading to cusps BEACH SWASH BACKWASH Longshore Drift

9 Cliff Erosion Wave Sediment Accumulation/Loss Cliff Profile Sediment Movement Cutback Cliff Face Shore Platform Geology Type Strength Hardness Structure Strata (dip, permeability)

10 Remote Sensing, Monitoring, Mapping and Coastal Erosion

11 Task – Worksheet No. 2 http://www.coastal.udel.edu/faculty/rad/linearplot.html Input Wave Data, Examine the Output and Tabulate to see if you can find out what this model does and any relationships/patterns that exist Visualisation


Download ppt "Wave Dominated Coasts Objective: to examine some of the processes and characteristics active on a wave-dominated coast."

Similar presentations


Ads by Google