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BPP identifies the current shoreline conditions and provides cost effective strategies for future beach management along the County's shoreline in particular the FDEP classified critically eroded areas. Wind, waves, and long shore currents are the driving forces behind coastal erosion. This removal and deposition of sand permanently changes beach shape and structure (Sea Grant Haznet, 1998). Most beaches, if left alone to natural processes, experience natural shoreline retreat. Historically, shoreline retreat is exacerbated by the effects of stabilized (jettied) coastal inlets, which interrupt the natural transport of sediment and promote erosion on the downdrift beaches. It has been estimated that on the east coast of Florida, as much as 80% of the observed erosion is directly attributable to the effects of stabilized inlets (Dean and Work 1993). As houses, highways, seawalls, and other structures are constructed on or close to the beach, the natural shoreline retreat processes may be interrupted. Construction along a historically erosive shoreline increases the likelihood of a property becoming threatened by shoreline retreat. The wave climate impacting the County's 22.4 miles of coastline has contributed to the long term erosion of the County's barrier island. The need for shore protection often results in property owners "hardening" the coast with a structure such as a seawall or revetment. A seawall is a large concrete or steel sheet pile wall designed to protect buildings or other man-made structures from beach erosion. A revetment is a cheaper option constructed with "rip rap" such as large boulders, concrete rubble, or even old tires. Although these structures may serve to protect beachfront property for a while, the resulting disruption of the natural coastal processes has serious consequences for all beaches in the area. Seawalls inhibit the natural ability of the beach to adjust its slope to the ever-changing ocean wave conditions. Large waves wash up against the seawall and rebound back out to sea, carrying large quantities of beach sand with them. With each storm, the beach narrows, sand is lost to deeper water, and the long shore current scours the base of the wall. Eventually, large waves impact the seawall with such force that a bigger structure becomes necessary to continue to resist the forces of the ocean (Pilkey and Dixon, 1996). Indian River County Comprehensive Emergency Management Plan Basic Page 47