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Methods of Coastal Hazards Assessment David M. Bush Risk Assessment GEOL 4093
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Island-scale mapping 1990’s Originally done by hand on clear plastic overlays and tracing paper We didn’t know at the time that it was GIS Andy and R/V Bicycle Elevation Forest Cover
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Island-scale mapping1990’s
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Analog GIS Andy--R/V Bicycle Elevation Forest Cover
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Florida Panhandle, after Opal (1995)
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Pawleys Island, SC, after Hugo (1989)
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South of Cancun after Gilbert, 1988
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B Zone A Zone V Zone Jekyll Island flood zones
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Forest No Forest Jekyll Island forest cover
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Preliminary Risk Assessment FLOOD ZONEVEGETATIONRATING V---Extreme ANone or sparseHigh A Dense shrub or forest Moderate Above ANone or sparseModerate Above A Dense shrub or forest Low
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Water Low Hazard Moderate Hazard High Hazard Extreme Hazard Jekyll Island preliminary hazard assessment
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Mainland Mapping Tracy Rice developed this using fetch instead of SLOSH
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Risk Rating ParameterExtremeHighModerateLow Vegetation None, sparse, marsh, 6 Scattered shrub, 4 Dense shrub, 2 Maritime forest, 1 Q-3 Flood zones VE and undes., 8 A and AE. 6 X500, 2 X, 1 SLOSH Category 1-3, 8 Category 4, 5, and upland, 0 Ranges 16-2211-155-100-4
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Geo-indicators Elevation Vegetation Tidal range Bluff configuration Evidence of historical storm impacts Type of structures Density of structures Site relative to stream mouth Soil and drainage Other surrounding features
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Geoindicators Assessment General Site Parameters GeoindicatorsHigh RiskModerate RiskLow Risk Elevation < 3 m3-6 m> 6 m Tidal Range microtidalmesotidalmacrotidal Bluff Configuration bare face, recent slump vegetated face, ramp well-vegetated ramp Erosion rate rapidly erodingeroding stable or accreting Evidence of storms obvious possiblenone Total Indicators Of High Risk Of Moderate Risk Of Low Risk
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Camden County, GA Study Sites
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St. Marys, GA
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Elliots Bluff, GA
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Puerto Rico Coastal Hazards Maps 1.Shoreline-setting hazards (long-term problems) 2.Marine hazards (short-term impacts of storms) 3.Earthquake and slope hazards (ground shaking, landslides, liquefaction) 4.Riverine hazards (historical floods) 5.Development hazards (high-density or dangerous settings) 6.Engineering hazards (stabilization, nourishment, sand mining)
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Methodology, conclusion Each coastal stretch is designated a relative hazard rating based on the following: E = Extreme—more than 4 identifiable hazards H = High—3 to 4 identifiable hazards M = Moderate—at least 2 hazards L = Low—1 or no hazard
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Puerto Rico Culebra Vieques
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A portion of the Carolina, PR, Coastal Hazard Map.
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The portion of Coastal Hazard Map 1, San Juan.
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Mitigation Engineering –Strengthen or move buildings –Armor the coast Land Use Planning –Limit or reduce development density –Can help implement new techniques such as clustered housing –Easiest with new developments
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Our Approach to Mitigation Coastal landform protection, restoration, augmentation Mostly low cost Many things individuals can do Environmentally sensitive Considers geologic/oceanographic processes
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PAR For the Shore Preserve, Augment, Restore –Dunes (frontal and interior) –Coastal barriers of all types Mangroves Shoals River mouth bars Maritime forest –Add new sand to island
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Pandora’s Island—Mitigation on the Beach
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Pandora’s Island—Mitigation back from the beach
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Pandora’s Island becomes Fantasy Island
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Topographic Map of Study Area Harrison County, Mississippi
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3.2 mile study area
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GIS - Map Stacking Example Land cover from air photo Flood zones Land surface slope Katrina damage layer
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Debris Line
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Total Building Destruction
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