This dataset depicts the geographic distribution of coastal risk along the Hudson River shoreline of Rockland, Orange, Ulster, Greene, Albany, Rensselaer, Columbia, Dutchess, and Putnam Counties. The objective of the Risk Assessment (and resulting mapped Risk Areas) is to define areas at risk from coastal hazards. Data were collected from sources accurate enough to differentiate geographic areas according to the likelihood of flooding, erosion, waves and storm surge. To the extent allowed by source data, areas where flood water can extend up streams and under culverts and bridges are reflected in mapping. The mapping process and data sources used are described below. Mapped Risk Areas are classified into three categories: Extreme, high, and moderate. Extreme Risk Areas: These are areas currently at risk of frequent inundation, vulnerable to erosion in the next 40 years, or likely to be inundated in the future due to sea level rise. Criteria and source data used to define these Extreme Risk Areas include: FEMA V zone. Areas subject to High Tide Flooding per NOAA NWS’s advisory threshold. Added 3 feet to the MHHW shoreline and extended this elevation inland over the digital elevation model (DEM) to point of intersection with ground surface. These four criteria were overlaid and polygons were generated that included the maximum spatial extend of the above-listed criteria. These polygons represent Extreme Risk Areas. High Risk Areas: These are areas that fall outside of the Extreme Risk Areas and are currently at infrequent risk of inundation or are at risk in the future from sea level rise. Criteria and source data used to define these High Risk Areas include: Area bounded by the 1% annual flood risk zone (FEMA A zones). Added 3 feet to NOAA NWS high tide flooding advisory threshold and extended this elevation inland over the DEM to point of intersection with ground surface.Polygons were created that were upland of the Extreme Risk Area boundary and included the maximum spatial extent of the above-listed criteria. These polygons represent High Risk Areas. Moderate Risk Areas: These are areas that fall outside of the Extreme and High Risk Areas, but are currently at moderate risk of inundation from infrequent events or are at risk in the future from sea level rise. Criteria and source data used to define these High Risk Areas include: Area bounded by the 0.2% annual risk (500 year) flood zone, where available. Added 3 feet to the Base Flood Elevation for the current 1% annual risk flood event and extended this elevation inland over the DEM to point of intersection with ground surface. Area bounded by SLOSH category 3 hurricane inundation zone. Polygons were created that were upland of the Extreme & High Risk Area boundaries and included the maximum spatial extent of the above-listed criteria. These polygons represent Moderate Risk Areas. (June2021)
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