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US Army Corps of Engineers BUILDING STRONG ® Dunes Mike Wutkowski Coastal Engineer
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BUILDING STRONG ® DUNES BENEFITS
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BUILDING STRONG ®
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* The areas with existing wide beaches and a frontal dune system, either natural or man-made, experienced less storm damage. Protected AreaUnprotected Area North Topsail Beach After Fran Wrightsville Beach After Fran * “Hurricane Fran Effects on Communities With and Without Shore Protection: A Case Study at Six North Carolina Beaches” Dec 2000
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BUILDING STRONG ® There are the places that had a protective dune system installed and, as a result, sustained minimal damage. Then there are the areas where there were no tall dunes, where Sandy made its destructive powers known. Ryan HutchinsRyan Hutchins and Seth Augenstein/The Star-LedgerSeth Augenstein Hurricane Sandy /Long Beach Island
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BUILDING STRONG ® Structures Threatened or Destroyed HURRICANES FLOYD & DENNIS Outside ProjectsInside Projects 9680 Source Spencer Rogers North Carolina Sea Grant
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BUILDING STRONG ® Economic Summary ITEMSSELECTED PLAN NED PLAN Total Initial Construction$32,131,000$43,028,000 Interest During Construction$275,000$369,000 Total Investment Cost$32,406,000$43,397,000 Renourishment Cost (4 year)$9,202,000 Total Annual Cost$4,119,000$4,710,000 Total Annual Benefits$13,590,000$14,255,000 BCR3.3 to 13.0 to 1 Annual Net Benefits$9,471,000$9,545,000 Compare Recommended/Locally Preferred Plan to NED Plan 50-yr period of analysis @ 4-7/8%, Price Level October 2007
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BUILDING STRONG ® Differences in Risk – NED and LP Plan (one random 50-year scenario out of 1,000 in analysis) …all 50 years…worst event in that 50 years ( ~85-yr event ) 50-yearsWorst Storm Damaged byNEDLPNEDLP Storm Erosion109168105160 Flood889902594612 Storm Wave61806180 Number of structures impacted -- most impacts are from a ______________________single, rare event
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BUILDING STRONG ® Construction / Cost Rule of Thumb Costs Dune 8’ above Berm 105 ‘ wide ~20 cyds If space exists, at $8.50/cyd ~ $170/ft If shoreline must be pushed seaward, ~125 cyds at $8.50/cyd ~$1,100/ft Planting ~$8,000/acre ~$20/ft. Doesn’t include berm or overfill.
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BUILDING STRONG ®
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Crossovers
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BUILDING STRONG ®
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QUESTIONS?
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