CMRA Assessment Tool Data Sources

The CMRA Assessment Tool provides summaries of authoritative datasets for Counties and Tribal Lands. These summaries provide a consistent view of spatially heterogeneous data, and let users examine the intersection of climate data with federal information products such as Building Code Adoption Tracking. Read on to see how the data from various sources is processed to feed into the CMRA Assessment Tool.

Census TIGER/Lines

County and census tract boundaries were accessed from the U.S. Census Bureau TIGER/Lines database. The 2019 version was used to be consistent with the National Risk Index and Justice40 layers. As these products move to the 2020 census boundaries, the CMRA data will be updated in a consistent manner. Population estimates were based on the 2019 American Community Survey.


Census Tribal Boundary and Annexation Survey

The Census Tribal Boundary and Annexation Survey (BAS) combines Federally Recognized Reservations, Federally recognized Off-Reservation Trust Lands, Federal Tribal Subdivisions, Alaska Native Regional Corporations (ANRCs), and Hawaiian Home Lands. In Tribal BAS updates tribes submit boundary corrections that are not the result of a legal change, New Reservation or off-reservation trust lands, or new or updated tribal subdivisions. The BAS is updated annually. The goal of the BAS is to best identify the lands where tribe members live.


Climate Data Summaries

Information displayed in Area 1 of Figure 1 shows projections of future climate conditions for three periods under two emissions scenarios. Climate summaries for the contiguous 48 states were derived from data generated for the 4th National Climate Assessment. These data were accessed from the Scenarios for the National Climate Assessment website. The 30-year mean values for 4 time periods (historic, early-, mid-, and late-century) and two climate scenarios (RCP 4.5 and 8.5) were derived from the Localized Constructed Analogs (LOCA) downscaled climate model ensembles, processed by the Technical Support Unit at NOAA’s National Center for Environmental Information. The netCDF data from the website were summarized by county and census tract using the Zonal Statistics as Table utility in ArcGIS Pro. The results were joined into the corresponding geography polygons. A minimum, maximum, and mean value for each variable was calculated. This process was repeated for each time range and scenario. In order to display the full range of projections from individual climate models for each period, data originally obtained from USGS THREDDS servers were accessed via the Regional Climate Center’s Applied Climate Information System (ACIS). This webservice facilitated processing of the raw data values to obtain the climate hazard metrics available in CMRA.

As LOCA was only generated for the contiguous 48 states (and the District of Columbia), alternatives were used for Alaska and Hawaii. In Alaska, the Bias Corrected Spatially Downscaled (BCSD) method was used. Data were accessed from USGS THREDDS servers. The same variables provided for LOCA were calculated from BCSD ensemble means. However, only RCP 8.5 was available. Minimum, maximum, and mean values for county and census tracts were calculated in the same way as above. For Hawaii, statistics for two summary geographies were accessed from the U.S. Climate Resilience Toolkit’s Climate Explorer: Northern Islands (Honolulu County, Kauaʻi County) and Southern Islands (Maui County, Hawai'i County).


Coastal Inundation

The sea level rise (SLR) coastal inundation layers were created using existing federal  products: the (1) NOAA Coastal Digital Elevation Models (DEMs) and (2) 2022 Interagency Sea Level Rise Technical Report Data Files. The DEMs for the Continental United States (CONUS) are provided in North American Vertical Datum 1988 (NAVD 88) and were converted to Mean Higher High Water (MHHW) using the NOAA VDatum conversion surfaces; the elevation values are in meters (m). The NOAA Scenarios of Future Mean Sea Level are provided in centimeters (cm). The MHHW DEMs for CONUS were merged and converted to cm and Scenarios of Future Mean Sea Level were subtracted from the merged DEM. Values below 0 represent areas that are below sea level and are “remapped” to 1, all values above 0 are remapped to “No Data”, creating a map that shows only areas impacted by SLR. Areas protected by levees in Louisiana and Texas were then masked or removed from the results. This was done for each of the emissions scenarios (Lower Emissions = 2022 Intermediate SLR Scenario Higher Emissions = 2022 Intermediate High SLR Scenario) at each of the mapped time intervals (Early Century - Year 2030, Middle Century - Year 2050, and Late Century - Year 2090).

The resulting maps are displayed in the CMRA Assessment Tool. County, tract, and tribal geographies summaries of percentage SLR inundation were also calculated using Zonal Statistics tools. The Sea Level Rise Scenario year 2020 is considered “baseline” and the impacts are calculated by subtracting the baseline value from each of the near-term, mid-term and long-term timeframes. 

Impact Percent Calculations

C = County Pixel Count - number of pixels (including water areas) within a county boundary.
T = Census Tract Pixel Count - number of pixels (including water areas) within a census tract boundary.
TL = Tribal Lands Pixel Count - number of pixels (including water areas) within a tribal land boundary.
B = Baseline Pixel Count - number of pixels within a county boundary impacted by sea level rise for the respective SLR baseline scenario.
X = Scenario Pixel Count - number of pixels within a county boundary impacted by sea level rise for given scenario 

County Impact Percent = ((X-B)/C) * 100

Tract Impact Percent = ((X-B)/T) * 100

Tribal Lands Impact Percent = ((X-B)/TL) * 100

General Disclaimer
The data and maps in this tool illustrate the scale of potential flooding, not the exact location, and do not account for erosion, subsidence, or future construction. Water levels are relative to Mean Higher High Water (MHHW) (excludes wind driven tides). The data, maps, and information provided should be used only as a screening-level tool for management decisions. As with all remotely sensed data, all features should be verified with a site visit. Hydroconnectivity was not considered in the mapping process.  The data and maps in this tool are provided “as is,” without warranty to their performance, merchantable state, or fitness for any particular purpose. The entire risk associated with the results and performance of these data is assumed by the user. This tool should be used strictly as a planning reference tool and not for navigation, permitting, or other legal purposes.

SLR visualizations and statistics are not available in CMRA for Hawaii, Alaska, or U.S. territories at this time.

Levees Disclaimer
Enclosed levee areas are displayed as gray areas on the maps.

Major federal leveed areas were assumed high enough and strong enough to protect against inundation depicted in this viewer, and therefore no inundation was mapped in these regions. Major federal leveed areas were taken from the National Levee Database.

Minor (nonfederal) leveed areas were mapped using the best available elevation data that capture leveed features. In some cases, however, breaks in elevation occur along leveed areas because of flood control features being removed from elevation data, limitations of the horizontal and vertical resolution of the elevation data, the occurrence of levee drainage features, and so forth. Flooding behind levees is only depicted if breaks in elevation data occur or if the levee elevations are overtopped by the water surface. At some flood levels, alternate pathways around—not through—levees, walls, dams, and flood gates may exist that allow water to flow into areas protected at lower levels. In general, imperfect levee and elevation data make assessing protection difficult, and small data errors can have large consequences.

Citations
2022 Sea Level Rise Technical Report - Sweet, W.V., B.D. Hamlington, R.E. Kopp, C.P. Weaver, P.L. Barnard, D. Bekaert, W. Brooks, M. Craghan, G. Dusek, T. Frederikse, G. Garner, A.S. Genz, J.P. Krasting, E. Larour, D. Marcy, J.J. Marra, J. Obeysekera, M. Osler, M. Pendleton, D. Roman, L. Schmied, W. Veatch, K.D. White, and C. Zuzak, 2022: Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines. NOAA Technical Report NOS 01. National Oceanic and Atmospheric Administration, National Ocean Service, Silver Spring, MD, 111 pp. 


Current Flooding Hazards

FEMA’s National Flood Hazard Layer (NFHL) is the official assessment of areas in the U.S. susceptible to flooding and provides 100-year (1% annual chance of flooding) and 500-year (0.2% annual chance of flooding) floodplain areas. The NFHL was accessed on October 13, 2021. Zonal statistics of the percentage of a county, census tract, or tribal area that lies within the 100 or 500-year floodplain were calculated, along with percentages of areas that are not mapped by the NFHL.


Building Codes

FEMA maintains a database of building code requirements for the U.S. called the Building Code Adoption Tracking (BCAT). The data in this tool were accessed August 2022. The data are organized into counties and municipalities (rather than census tracts). Figure 1 Area 4 provides a flag to display the status of the building codes at the county level.

  • Fully Resistant – 100 % of county is required to adhere to a hazard-resistant building code
  • Partially Resistant – between 0.1 % and 100 % of county is required to adhere to a hazard-resistant building code
  • Lower resistance – no part of county is required to adhere to a hazard-resistant building code

When screening at the census tract level the flag is associated with the county-level data since there is no easy way to intersect census tracts and municipalities.