USA Storm Surge Hazard Maps (SLOSH) - NOAA

This national depiction of storm surge flooding vulnerability helps people living in hurricane-prone coastal areas along the U.S. East and Gulf Coasts and Puerto Rico to evaluate their risk to the storm surge hazard. These maps make it clear that storm surge is not just a beachfront problem, with the risk of storm surge extending many miles inland from the immediate coastline in some areas. If you discover via these maps that you live in an area vulnerable to storm surge, find out today if you live in a hurricane storm surge evacuation zone as prescribed by your local emergency management agency. If you do live in such an evacuation zone, decide today where you will go and how you will get there, if and when you're instructed by your emergency manager to evacuate. If you don't live in one of those evacuation zones, then perhaps you can identify someone you care about who does live in an evacuation zone, and you could plan in advance to be their inland evacuation destination – if you live in a structure that is safe from the wind and outside of flood-prone areas.

SLOSH has been used operationally for more than three decades. Over this time, SLOSH has provided valuable and accurate storm surge forecasts. For planning purposes, the NHC uses a representative sample of hypothetical storms to estimate the near worst–case scenario of flooding for each hurricane category. These SLOSH simulations are used to create a set of operational and planning products.

The NHC provides two products based on hypothetical hurricanes: MEOWs and MOMs. MEOWs are created by computing the maximum storm surge resulting from up to 100,000 hypothetical storms simulated through each SLOSH grid of varying forward speed, radius fo maximum wind, intensity (Categories 1-5), landfall location, tide level, and storm direction. A MEOW product is created for each combination of category, forward speed, storm direction, and tide level. SLOSH products exclude Category 5 storms north of the NC/VA border. For each storm combination, parallel storms make landfall in 5 to 10 mile increments along the coast within the SLOSH grid, and the maximum storm surge footprint from each simulation is composited, retaining the maximum height of storm surge in a given basin grid cell. These are called MEOWs and no single hurricane will produce the regional flooding depicted in the MEOWs. SLOSH model MOMs are an ensemble product of maximum storm surge heights. SLOSH MOMs are created for each storm category by retaining the maximum storm surge value in each grid cell for all the MEOWs, regardless of the forward speed, storm trajectory, or landfall location. SLOSH MOMs are available for mean tide and high tide scenarios and represent the near worst-case scenario of flooding under ideal storm conditions. A high tide initial water level was used for the storm surge hazard maps.

SLOSH employs curvilinear polar, elliptical, and hyperbolic telescoping mesh grids to simulate the storm surge hazard. The spatial coverage for each SLOSH grid ranges from an area the size of a few counties to a few states. The resolution of individual grid cells within each basin ranges from tens to hundreds of meters to a kilometer or more. Sub–grid scale water features and topographic obstructions such as channels, rivers, and cuts and levees, barriers, and roads, respectively are parameterized to improve the modeled water levels.

Important information

Storm surge hazard maps are available for Texas to Maine and Puerto Rico. The data are available in GeoTIFF ( format for use in Geographic Information Systems (GIS) software. Comprehensive metadata are provided with each GIS file describing the data and its limitations. Storm surge inundation datasets are created using the high tide scenario SLOSH MOM products for all regions. Each dataset contains an ESRI World File (.tfw) and metadata .xml file. These GeoTIFFs are 8-bit unsigned integer raster datasets that correspond to 1 ft inundation bins (e.g., Class Value 1 corresponds to the 0-1 ft inundation bin, Class Value 2 corresponds to the 1-2 ft inundation bin, and so on). The maximum Class Value is 21, and inundation in excess of 20 ft is assigned a Class Value of 21. A Class Value of 99 is assigned to leveed areas. A more detailed description of the data can be found in the associated metadata. - NOAA

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Additional Info

Field Value
Author Brian C. Zachry
Last Updated December 6, 2017, 13:36 (Etc/UTC)
Created July 4, 2017, 09:28 (Etc/UTC)
Origin Places Americas, United States of America
Price, £ -

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