The USGS has produced a comprehensive database of digital vector shorelines by compiling shoreline positions from pre-existing historical shoreline databases and by generating historical and modern shoreline data. Shorelines are compiled by state and generally correspond to one of four time periods: 1800s, 1920s-1930s, 1970s, and 1998-2002. These shorelines were used to calculate long-term and short-term change rates in a GIS using the Digital Shoreline Analysis System (DSAS) version 3.0; An ArcGIS extension for calculating shoreline change: U.S. Geological Survey Open-File Report 2005-1304, Thieler, E.R., Himmelstoss, E.A., Zichichi, J.L., and Miller, T.M. Shoreline vectors derived from historic sources (first three time periods) represent the high water line (HWL) at the time of the survey, whereas modern shorelines (final time period) represent the mean high water line (MHW). Changing the shoreline definition from a proxy-based physical feature that is uncontrolled in terms of an elevation datum (HWL) to a datum-based shoreline defined by an elevation contour (MHW) has important implications with regard to inferred changes in shoreline position and calculated rates of change. This proxy-datum offset is particularly important when averaging shoreline change rates alongshore. Since the proxy-datum offset is a bias, virtually always acting in the same direction, the error associated with the apparent shoreline change rate shift does not cancel during averaging and it is important to quantify the bias in order to account for the rate shift. The shoreline change rates presented in this report have been calculated by accounting for the proxy-datum bias.
publication date
Bias Uncertainty Values(Source:
USGS)
Internal feature number.(Source:
ESRI)
Feature geometry.(Source:
ESRI)
Feature number.(Source:
U.S. Geological Survey)
Detailed description of the feature.(Source:
U.S. Geological Survey)
Shoreline Bias Value(Source:
USGS)
| Range of values | |
|---|---|
| Minimum: | 10.1 |
| Maximum: | 24.2 |
| Units: | meters |
| Resolution: | 0.1 |
Long-Term Bias Uncertainty(Source:
USGS)
| Range of values | |
|---|---|
| Minimum: | 5.7 |
| Maximum: | 15.9 |
| Units: | meters |
| Resolution: | 0.1 |
Short Term Bias Uncertainty(Source:
USGS)
| Range of values | |
|---|---|
| Minimum: | 9.9 |
| Maximum: | 27.5 |
| Units: | meters |
| Resolution: | 0.1 |
Pacific Science Center
400 Natural Bridges Drive
Historical shoreline change is considered to be a crucial element in studying the vulnerability of the national shoreline. These data are used in a shoreline change analysis for the U.S. Geological Survey (USGS) National Assessment Project.
In order to calculate the bias, as well as the bias uncertainty, for this regional shoreline change analysis, long-term best estimates and measures of uncertainty are derived for beach slope, wave height, wave length, and tide level. The best estimate for beach slope was derived by averaging individual lidar transect slope estimates within 1-km blocks along the coast. We take the long-term mean wave height and length to be the best estimate to use in the bias calculation. The long-term mean wave height is derived from USACOE Wave Information Studies (WIS) hindcasts while the long-term mean wave length is derived from long-term buoy records (NDBC and CDIP) along the California Coast. Finally, the best estimate of the tide level responsible for generating HWL shorelines is taken as the elevation of MHW. The measures of uncertainty for the beach slope, wave height, and wave length are estimated as the difference between the 95% exceedance statistic and the 50% exceedance statistic of the cumulative distributions. This gives a 90% confidence interval on each of the cumulative distributions. The uncertainty of assuming that the tide responsible for leaving HWL-type shorelines was at MHW is calculated simply by MHHW-MHW. The proxy-datum bias, and the associated uncertainty, is calculated at each of the 1-km blocks in which the average beach slope has been calculated. The nearest WIS station, wave buoy, and tide gage to each individual 1-km block were used in the application of Equation 1. Once the bias was calculated, it was incorporated into DSAS and applied on a transect-by-transect basis, so that the estimated bias is removed from the final long- and short-term shoreline change rates. The bias, averaged over 815 1-km sections of the California coast, was approximately 18 m with an average uncertainty of approximately 8.7m. Please See Below References for More information about the procedure: Ruggiero, P., Kaminsky, G.M., and Gelfenbaum, G., 2003, Linking proxy-based and datum-based shorelines on a high-energy coastline: Implications for shoreline change analyses: Journal of Coastal Research Special Issue 38, p. 57-82. Moore, L.J., Ruggiero, P.R. and List, J., 2006. Comparing high water line and datum-based shorelines: Implications for shoreline change. Journal of Coastal Research, v.22, n.4, pp. 894-905.
Pacific Science Center
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Data were projected from UTM zone 10 to geographic with a datum shift from NAD27 to NAD83 Tool: ArcGIS > ArcToolbox > Toolboxes > Data Management Tools > Project Command issued: GEOGCS['GCS_North_American_1983',DATUM['D_North_American_1983',SPHEROID['GRS_1980',6378137.0,298.257222101]],PRIMEM['Greenwich',0.0],UNIT['Degree',0.0174532925199433]] # NAD_1927_To_NAD_1983_NADCON
384 Woods Hole Road
The bias uncertainty, averaged over 815 1-km sections of the California coast, was approximately 18 m with an average uncertainty of approximately 8.7m. Please see the Open File Report for more information (http://pubs.usgs.gov/of/2006/1219/)
The bias, averaged over 815 1-km sections of the California coast, was approximately 18 m with an average uncertainty of approximately 8.7m.
The proxy-datum bias, and the associated uncertainty, is calculated at each of the 1-km blocks in which the average beach slope has been calculated. The nearest WIS station, wave buoy, and tide gage to each individual 1-km block were used in the application of Equation 1. Once the bias was calculated, it was incorporated into DSAS and applied on a transect-by-transect basis, so that the estimated bias is removed from the final long- and short-term shoreline change rates.
Public domain data from the U.S. government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.
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Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, these data and information are provided with the understanding that they are not guaranteed to be usable, timely, accurate, or complete. Users are cautioned to consider carefully the provisional nature of these data and information before using them for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences. Conclusions drawn from, or actions undertaken on the basis of, such data and information are the sole responsibility of the user. Neither the U.S. Government nor any agency thereof, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any data, software, information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. Trade, firm, or product names and other references to non-USGS products and services are provided for information only and do not constitute endorsement or warranty, express or implied, by the USGS, USDOI, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy.
Data format: |
Seven files comprise the ArcView shapefile: <filename>.dbf, <filename>.shp, <filename>.shx, <filename>.prj, <filename>.avl, <filename>.sbx, <filename>.sbnin format SHP ESRI polyline shapefileSize: 0.038 |
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Network links: |
http://pubs.usgs.gov/of/2006/1251/CCal.zip
http://pubs.usgs.gov/of/2006/1251/#gis |
Pacific Science Center
400 Natural Bridges Drive