The University of the West Indies Organization of American States PROFESSIONAL DEVELOPMENT PROGRAMME: COASTAL INFRASTRUCTURE DESIGN, CONSTRUCTION AND MAINTENANCE A COURSE IN COASTAL ZONE/ISLAND SYSTEMS MANAGEMENT CHAPTER 3 COASTAL PROCESSES 1 ADDITIONAL SLIDE PRESENATION OLD DOMINION UNIVERSITY COASTAL HYDRAULIC LABORATORY NORFOLK, VIRGINIA, USA US ARMY CORPS OF ENGINEERS, VICKSBURG, MA, USA Organized by Department of Civil Engineering, The University of the West Indies, in conjunction with Old Dominion University, Norfolk, VA, USA and Coastal Engineering Research Centre, US Army, Corps of Engineers, Vicksburg, MS , USA. Antigua, West Indies, June 18-22, 2001 AA RIVERRIVER OFOF SANDSAND Video (20 minutes) by Professor Douglas Inman, Ph.D. Scripps Institute of Oceanography and, John S. Shelton, Ph.D. American Geological Institute available from Encyclopedia Britannica Educational Corp. Chicago, Illinois 1967 THE BEACH: A RIVER OF SAND (video) Summary • Sand for beaches comes from upstream mountains • Beaches are formed by the seasonal variation of waves • Waves breaking at angle cause sand transport along the beach, like a river of sand • Man’s structures (harbors, breakwaters, upland dams, etc.) interrupt the sand movement US Army Corps of Engineers THE BEACH: A RIVER OF SAND (video) Summary • Conclusion “Whenever man interferes with such a system, he becomes involved in its operation. To the degree that man upsets the natural balance of the system, he and his machines must do the work that nature did before.” Inman and Shepard, 1967 US Army Corps of Engineers Waves (c) Pocket beach Rocky Rocky headland headland Narrow rocky shorelines Eq uil ibrium, MHW Y, stable Reference Baseline Dune, cliff, man's artifacts and vegetation THE BEACH: A RESERVOIR OF SAND • Naturally, stable shorelines include rocky headland/bay beaches and pocket beaches. • The minimum dry beach width, Ymin (or volume) depends on storm wave energy. • Beaches are shaped by the seasonal variation of waves. • Storm waves drag sand offshore to build bars. US Army Corps of Engineers THE BEACH: A RESERVOIR OF SAND • Normal waves naturally rebuild beaches after storm events. • The beach is a reservoir of sand to mitigate coastal storm impacts. • Conclusion The beach is INFRASTRUCTURE for coastal storm hazard mitigation and must be maintained if erosion, man’s interference or extreme hurricane events diminish the reservoir volume. US Army Corps of Engineers .