Introduction | Methods and Qualifiers | Data Layers | Sources | Special Thanks | Site Credits | Legal
Climate Central’s Surging Seas: Risk Zone map shows areas vulnerable to near-term flooding from different combinations of sea level rise, storm surge, tides, and tsunamis, or to permanent submersion by long-term sea level rise. Within the U.S., it incorporates the latest, high-resolution, high-accuracy lidar elevation data supplied by NOAA, displays points of interest, and contains layers displaying social vulnerability, population density, and property value. Outside the U.S., it utilizes satellite-based elevation data from NASA. It provides the ability to search by location name or postal code.
The accompanying Risk Finder is an interactive data toolkit for the U.S. that provides local projections and assessments of exposure to sea level rise and coastal flooding tabulated for every zip code and municipality along with planning, legislative and other districts. Exposure assessments cover over 100 demographic, economic, infrastructure and environmental variables using data drawn mainly from federal sources, including NOAA, USGS, FEMA, DOT, DOE, DOI, EPA, FCC and the Census. The three components of the Risk Finder can be accessed via links in the upper right hand corner of this map.
This web tool was highlighted at the launch of The White House's Climate Data Initiative in March 2014. Climate Central's original Surging Seas was featured on NBC, CBS, and PBS national news, the cover of The New York Times, in hundreds of other stories, and in testimony for the U.S. Senate. The Atlantic Cities named it the most important map of 2012. Both the Risk Zone map and the Risk Finder are grounded in peer-reviewed science.
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Methods and Qualifiers
This map is based on analysis of digital elevation models mosaicked together for near-total coverage of the global coast. Details and sources for U.S. and international data are below. Elevations are transformed so they are expressed relative to local high tide lines (Mean Higher High Water, or MHHW). A simple elevation threshold-based “bathtub method” is then applied to determine areas below different water levels, relative to MHHW. Within the U.S., areas below the selected water level but apparently not connected to the ocean at that level are shown as a stippled (as opposed to solid) blue on the map. Outside the U.S., due to data quality issues and data limitations, all areas below the selected level are shown as solid blue, unless separated from the ocean by a ridge at least 10 meters (33 feet) above MHHW, in which case they are shown as not affected (no blue).
Flood control structures
Levees, walls, dams or other features may protect some areas, especially at lower elevations. Levees and other flood control structures are included in this map within the U.S., but data limitations, such as an incomplete inventory of levees, and a lack of levee height data, make assessing protection difficult. For this map, levees are assumed high and strong enough for flood protection. However, it is important to note that only 8% of monitored levees in the U.S. are rated in “Acceptable” condition (ASCE). Also note that the map implicitly includes unmapped levees and their heights, if broad enough to be effectively captured directly by the elevation data.
Errors or omissions in elevation or levee data may lead to areas being misclassified. Furthermore, this analysis does not account for future erosion, marsh migration, or construction. As is general best practice, local detail should be verified with a site visit. Sites located in zones below a given water level may or may not be subject to flooding at that level, and sites shown as isolated may or may not be be so. Areas may be connected to water via porous bedrock geology, and also may also be connected via channels, holes, or passages for drainage that the elevation data fails to or cannot pick up. In addition, sea level rise may cause problems even in isolated low zones during rainstorms by inhibiting drainage.
For more information, visit Science Behind the Tool or read a U.S. state report (e.g. Florida) or global report.
For more information on how Surging Seas incorporates levees and elevation data in Louisiana, view our Louisiana levees and DEMs methods PDF.
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| Social Vulnerability
| Global Warning
Water level means feet or meters above the local high tide line (“Mean Higher High Water”) instead of standard elevation. Methods described above explain how each map is generated based on a selected water level. Water can reach different levels in different time frames through combinations of sea level rise, tide and storm surge. Tide gauges shown on the map show related projections (see just below).
The highest water levels on this map (10, 20 and 30 meters) provide reference points for possible flood risk from tsunamis, in regions prone to them.
Scientists agree that climate change has been driving a rise in global sea level, and the rise will accelerate, leading to ocean intrusion on land and aggravated coastal flood risk. Over 1,000 global tide gauges shown on the map, illustrated by bulls-eyes, give downloadable local projections for sea level rise through the year 2200, based on recent peer-reviewed research building off of global projections from the "IPCC. Select tide gauges within the U.S. where at least 30 years of hourly water level data are available also give flood risk projections which integrate sea level rise. In all cases, users may select from among different carbon pollution scenarios, including “unchecked pollution” (technically, Representative Concentration Pathway 8.5, or RCP 8.5), “moderate carbon cuts” (RCP 4.5), and “extreme carbon cuts” (RCP 2.6), this last choice meaning a peak in emissions near the year 2020 followed by a sharp decline to zero near 2070. For gauges with flood risk projections, users may choose between viewing accrued risk (i.e. what is the risk of flooding between the present and a future year) or annual risk (i.e. what is the risk of flooding within a single future year).
Below water level: Areas below water level, and connected to the ocean.
Below but isolated: Areas below water level, but not connected to the ocean, due to natural or built breaks such as levees. This type of area is separately identified only within the U.S., where higher quality elevation data and the availability of levee data allow greater confidence in the assessment of connectivity. See Methods for more detail.
Levees: Built flood control structures.
Tide gauges: Locations with long-term water level records sufficient for making localized sea level projections and, in cases, flood risk projections.
This map defines social vulnerability as the ability of communities to prepare and respond to hazards like flooding. "High" and "low" indicate the 20% most and least vulnerable in coastal areas of each state. Census tract resolution data. Data source: Hazards and Vulnerability Research Institute (HVRI)'s Social Vulnerability Index. (Map layer currently available only within the U.S.)
Census block resolution data. Data source: U.S. Census (Map layer currently available only within the U.S.)
U.S. Census definitions used. Census block resolution data. Data source: U.S. Census (Map layer currently available only within the U.S.)
Per capita income. Census tract resolution data. Data source: U.S. Census (Map layer currently available only within the U.S.)
Census block group resolution data. Based mostly on assessed values in 2008, adjusted to 2012 dollars. Data source: U.S. Environmental Protection Agency. (Map layer currently available only within the U.S.)
Data sources: U.S. Department of Transportation
, U.S. Energy Information Administration
, U.S. Board of Geographic Names / U.S. Geological Survey
, National Telecommunications and Information Administration
, National Center for Education Statistics
(Map layer currently available only within the U.S.)
Elevation data used for parts of this map within the U.S. come almost entirely from ~5-meter horizontal resolution digital elevation models curated and distributed by NOAA
in its Coastal Lidar
collection, derived from high-accuracy laser-rangefinding measurements. The same data are used in NOAA’s Sea Level Rise Viewer
. In our tests, the two maps have a 95% or better match between 0 and 6 ft above high tide (6 ft is the max height in the Viewer). (Elevation data for Louisiana, southeast Virginia and limited other areas comes from the U.S. Geological Survey (USGS)
Areas of this map outside the U.S. use elevation data on a roughly 90-meter horizontal resolution grid derived from NASA’s Shuttle Radar Topography Mission (SRTM). SRTM provides surface elevations, not bare earth elevations, causing it to commonly overestimate elevations, especially in areas with dense and tall buildings or vegetation. Therefore, the map very likely under-portrays areas that could be submerged at each water level, and potential exposure is statistically greater than shown. However, SRTM includes error in both directions, so some areas showing exposure may not be at risk.
SRTM data do not cover latitudes farther north than 60 degrees or farther south than 56 degrees, meaning that sparsely populated parts of Arctic Circle nations are not mapped here.
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See Data Layers, above, for most sources. Others follow.
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To Climate Central’s financial supporters for this project, including The Schmidt Family Foundation, The Kresge Foundation, The Rockefeller Foundation, Island Foundation, and others.
To NOAA's Office for Coastal Management, which has provided high-accuracy coastal elevation data, consistent courtesy, and leadership with its Sea Level Rise Viewer, a map tool Surging Seas strives to complement.
To our project partner for U.S. social vulnerability analysis, the University of South Carolina Hazards and Vulnerability Research Institute.
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Map designed and built in collaboration with Stamen Design in San Francisco.
- Hospital icon used to represent Hospitals designed by Saman Bemel-Benrud from The Noun Project.
- Badge icon used to represent Fire/EMS/Police stations designed by Edward Boatman from The Noun Project.
- School icon used to represent Schools/Colleges designed by Saman Bemel-Benrud from The Noun Project.
- Prayer icon used to represent Houses of Worship was designed by Carson Wittenberg from The Noun Project.
- Museum icon used to represent Culture/Museums/Arts designed by Unknown Designer from The Noun Project.
- Government Office icon used to represent Government/Community designed by OCHA AVMU from The Noun Project.
- Power Plant icon used to represent Powerplants designed by Iconathon with Collaboration by Chad Williamsen, Katie Williamsen, Alison Harshbarger & John Durkee from The Noun Project.
- Caution icon used to represent EPA-Listed Sites designed by Sam Ahmed from The Noun Project.
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General Disclaimer & Legal Terms
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