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Maryland Department of Natural Resources (MDDNR), Eastern Shore Regional GIS Cooperative (ESRGC), National Oceanic and Atmospheric Administration (NOAA), United States Army Corps of Engineers (USACE), United States Geoglogical Survey (USGS).
The 2006 building footprints from which this dataset is built was provided by Somersest County (originator: Spatial Systems Associates, Inc.) |
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The layer supports Maryland Department of Natural Resources (MDDNR) leadership and planners as they endeavor to mitigate or prevent the impacts of sea level change resulting from land surface subsidence and rising sea levels. The product uses sea-level projections to forecast maximum stillwater elevations and first floor flooding inside building footprints of Somerset County's for a given scenario.Methodology:US Army Corps of Engineers (USACE) provide the sea level change (SLC) estimate-1. SLC is localized using water elevations collected from a qualifying-2 National Oceanic and Atmospheric Administration (NOAA) tidal reference station - NOAA observations are transformed from tidal datum to North American Vertical Datum of 1988 (NAVD88). A final correction for glacial isostatic adjustment and land subsidence is applied to create an SLC value for the official project year, 2015.Forecast Sea Level Change:Year; Tide: SLC Value; Tide: SLC Value2015; MSL: 0; MHHW: 1.022020; MSL: 0.52; MHHW: 1.542030; MSL: 0.88; MHHW: 1.902040; MSL: 1.31; MHHW: 2.332050; MSL: 1.82; MHHW: 2.84The best available LiDAR, at time of creation, contributes to a county-wide Digital Elevation Model (DEM). The LiDAR-derived DEM is the base from which the SLC value is applied.The SLC adjusted DEM serves as elevation data for a Level 1 Coastal Only HAZUS-MH (FEMA) Flood analysis. The shoreline of the county level study is limited to Deal Island Neck. Breakpoints segment the shorline to capture flooding sources, locations, and heights outlined in the FEMA Flood Insurance Study for Somerset County, Maryland - #24039CV000A; Effective: March 03, 2011.Expected Flood Values:Flooding Source; Location; Annual Chance Event: Eleveation (ft) NAVD88Chesapeake Bay; Drum Point; 10%: 3.3, 4%: 3.675, 2%: 4.3, 1%: 4.7, 0.2%: 5.7Chesapeake Bay; Twiggs Point, Deal Island; 10%: 3.3, 4%: 3.712, 2%: 4.4, 1%: 4.8, 0.2%: 5.8Chesapeake Bay; Deal Point, Deal Island; 10%: 3.4, 4%: 3.812, 2%: 4.5, 1%: 4.9, 0.2%: 5.9Chesapeake Bay; Chance; 10%: 3.4, 4%: 3.85, 2%: 4.6, 1%: 5.0, 0.2%: 6.0Damage Curve assignment:First Floor Flood Depth; Building Damage %; Contents Damage %FFFDepth < -1, then BuildingDamage% = 0; ContentsDamage% = 0FFFDepth >= -1 and FFFDepth < 0, then BuildingDamage% = 18 + 18 * FFFDepth; ContentsDamage% = 12 + 12 * FFFDepthFFFDepth >= 0 and FFFDepth < 1, then BuildingDamage% = 18 + 4 * FFFDepth; ContentsDamage% = 12 + 13 * FFFDepthFFFDepth >= 1 and FFFDepth < 2, then BuildingDamage% = 19 + 3 * FFFDepth; ContentsDamage% = 15 + 10 * FFFDepthFFFDepth >= 2 and FFFDepth < 3, then BuildingDamage% = 19 + 3 * FFFDepth; ContentsDamage% = 33 + 1 * FFFDepthFFFDepth >= 3 and FFFDepth < 4, then BuildingDamage% = 22 + 2 * FFFDepth; ContentsDamage% = 30 + 2 * FFFDepthFFFDepth >= 4, then BuildingDamage% = 26 + 1 * FFFDepth; ContentsDamage% = 26 + 3 * FFFDepth-1 The SLC rate used in this study was calculated using the USACE High Curve. See http://www.corpsclimate.us/ccaceslcurves.cfmfor more detail.-2 Closest station with historic records of 40 years or greater. An average or qualifying stations was chosen when the nearest station’s records were insufficient. |