Earth Sciences 1022A/B Lecture Notes - Lecture 11: Longshore Drift, Refraction, Beach Nourishment

• School: Western University
• Department: Earth Sciences
• Course: Earth Sciences 1022A/B
• Professor: Stephen R Hicock

Document Summary

Waves: from wind blowing over the ocean; a surface waveform of energy moves through the water whose molecules move side to side and up and down. As a wave approaches the shore it feels bottom and breaks into surf that moves up a beach as swash then water flows back down as backwash. Storm waves erode headlands by wave impact compressing air in fractures, by abrasion, undercutting. Sand movement on the beach: waves bend as they approach an irregular shoreline (wave refraction) so that erosion focuses on headlands, deposition occurs in bays. Wave refraction: waves bend toward irregular shoreline to erode headlands, and deposit in bays. Sawtooth pattern of swash and backwash results in: beach drift, longshore current that transport sediment along the shore. Most waves hit the shore at an angle and move sediment along beaches by the zigzag pattern of swash and backwash called beach drift.