Coastal Hazards - Waves, Beaches and Coastal Hazards People...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Waves, Beaches and Coastal Hazards People and Coasts Increase in spending money and leisure time led to growth in coastal tourism , especially after 1940s Coastal homes, hotels, resorts built along beaches By 2004, about 42% of U.S. population lived in coastal counties and continues to increase Beaches and sea cliffs constantly change, and coastal processes do not stop People build ‘permanent’ structures at coast, try to hold back sea and prevent natural changes When dealing with beach or riverbank the area will change over time! Seasonal Beach Changes Summer: less wave energy, wider beach, finer (smaller) sediments Winter: more wave energy, narrow beach, and coarser (bigger) sediments Waves Winds blowing across sea push water surface into waves Friction between air and water Wind-driven waves described in terms of wave height, wavelength, period Height of wave increased by fetch (length of water surface over which wind blows), and amount of time wind blows across water surface -Pacific Ocean bigger waves than Atlantic that is why Hawaii and California are good for surfing Wind driven waves are described in terms of period, wave height and wave length Waves generated with different sizes and moving at different speeds Can interfere to increase or decrease size of combination giant rogue (know on final!!!) waves- waves coming out of seemingly nowhere and is much higher than other waves- they are dangerous and may be causing ship sinkings in Africa Offshore: Water has circular motion within wave Waves approaching shore: Begin to ‘feel bottom’ and feel friction with rocks and slows down but top is still moving fast and that’s what causes breaking and wave coming over- where water depth is less than half wavelength Waves slow in shallow water but rise in height, causing them to break Wave energy is proportional to mass of moving water Open Ocean waves- motion is ½ that at surface at depth 1/9 of wavelength essentially zero at ½ wavelength (wave base)- feel wave less as it gets deeper, shallower waves become more oval Wave Refraction and Longshore Drift Breaking wave pushes sand grains up beach at angle and retreating wave flows down beach slope with sad perpendicular to water’s edge and angled waves create longshore drift, carrying sand along shore over time Waves often approach shore at angle Part of wave in shallower water slows down Part of wave still in deeper water moves faster Crest of wave curves around toward shore Wave refraction : waves bend or refract toward shore Breaking wave pushes sand grains up beach at angle Retreating wave flows down beach slope (with sand) perpendicular to water’s edge Angled waves create longshore drift , carrying sand along shore over time
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Waves on Irregular Coastlines (almost all are)
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/21/2010 for the course GEOL 116 taught by Professor Kruger during the Spring '09 term at Binghamton University.

Page1 / 5

Coastal Hazards - Waves, Beaches and Coastal Hazards People...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online