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Chapter 13:Hazard Analysis—Coastal Erosion <br /> CHAPTER 13 - COASTAL EROSION <br /> 13.1 Description of Hazard <br /> Beach erosion and coastal erosion are not the same,but they are related. Beach erosion is a <br /> reduction in the amount of sand a particular beach has. On a global level, sea level rise <br /> causes beach erosion. But beaches also erode(and expand)on a seasonal basis. <br /> Beaches get sand from both the ocean and the land. Larger waves move sand from the coastal <br /> sand dunes off into the ocean. This raises the seafloor, flattens the overall profile of the <br /> beach, and,therefore, causes waves to break further offshore. This, in turn,minimizes the <br /> waves'impact on coastal lands. Beaches recover from these seasonal shifts when the waves <br /> move the sand back onto the beach and the winds blow the deposited sand into dunes. These <br /> dunes will store the land-based sand until the next large wave event. <br /> Initial shore prof lie. <br /> —width— <br /> Shnrelirre profile after retreat. <br /> �eaas trap OnYW. in wid&W <br /> W ldlh— <br /> Aneach undergoing net longierm sweat will <br /> *nainlain its natural width. <br /> Inital shore praflie. <br /> -- 6e:idr <br /> wldlh <br /> Snswuq Stloreline profile after retreat. <br /> &1.VCh kj Ss <br /> awKu:Ua any rotas u1&Nw*ia(taa11 <br /> Bench loss eventually nccurs in trorit r)f a seHwall <br /> trrr a t}eaCh experiencirxl net InrHyerm retreat. <br /> Figure 13-1. The impacts of stabilization on shoreline retreat and beach loss <br /> 13-1 Hawaii County Multi-Hazard Mitigation Plan <br />