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destruction of soil structure, eroded land is even more <br />susceptible to erosion. <br />The occurrence of erosion has greatly increased, <br />usually at a rate at which soils cannot be sustained by <br />natural soil regeneration. This is because of the <br />activities of modern development and population <br />growth, particularly agricultural intensification. It is also <br />in the field of agriculture that most efforts have been <br />made to conserve soils, with mixed success (Union of <br />International Associations). <br />Particles scattered by erosion can also cause problems <br />elsewhere. Storm water drainage systems, both natural <br />and mechanical, are frequently clogged by loose <br />sediment. If drainage systems are not cleared of <br />uncontrolled sediment on a regular basis, they lose <br />function. <br />(2) Beach Erosion <br />Wind, waves, and long shore currents are the driving <br />forces behind coastal erosion. This removal and <br />deposition of sand permanently changes beach shape <br />and structure (Sea Grant Haznet, 1998). Most <br />beaches, if left along to natural processes, experience <br />natural shoreline retreat. As houses, highways, <br />seawalls, and other structures are constructed on or <br />close to the beach, the natural shoreline retreat <br />processes are interrupted. The beach jams up against <br />these man-made obstacles and narrows considerably <br />as the built-up structures prevent the beach from <br />moving naturally inland. When buildings are constructed <br />close to the shoreline, coastal property soon becomes <br />threatened by erosion. <br />The need for shore protection often results in <br />"hardening" the coast with a structure such as a seawall <br />or revetment. <br />A seawall is a large concrete wall designed to protect <br />buildings or other man-made structures from beach <br />erosion. A revetment is a cheaper option constructed <br />with "rip rap" such as large boulders, concrete rubble, or <br />Indian River County Comprehensive Emergency Management Plan Basic Page 19 <br />