Rates of long-term and short-term shoreline change were generated 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. The extension is designed to efficiently lead a user through the major steps of shoreline change analysis. This extension to ArcGIS contains three main components that define a baseline, generate orthogonal transects at a user-defined separation along the coast, and calculate rates of change (linear regression, endpoint rate, average of rates, average of endpoints, jackknife).
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.
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Pacific Science Center
400 Natural Bridges Drive
Baseline generation was made as part of the calculation process for the Digital Shoreline Analysis System an Extension for ArcGIS (http://pubs.usgs.gov/of/2005/1304/)
This baseine data represents a generalization of the shoreline of California used by DSAS. Remaining gaps in this data, if applicable, are a consequence of non-existing shoreline data.
A Baseline was generated within ArcGIS to be used by the Digital Shoreline Anaylsis System (http://pubs.usgs.gov/of/2005/1304/)in the calculation of shoreline change rates. Please visit our full report on shoreline change in the Coastline of California (http://pubs.usgs.gov/of/2006/1219/) for more information about this analysis
A baseline was manually constructed seaward of, and parallel to, the trend of shorelines representing four general time periods (1800s, 1920s-1930s, 1970s, and 1998-2002). Using DSAS (USGS OFR 2005-1304), transects were generated with a spacing of 50m and transect-shoreline intersection points were saved to a separate layer. Transects were manually eliminated to prevent calculation of rates in areas where less than four shorelines were intersected. Long-term rates of shoreline change, in units of m/yr, were calculated at each transect using linear regression applied to all four shoreline positions from the earliest (1800s) to the most recent (derived from lidar). Linear regression was selected because it has been shown to be the most statistically robust quantitative method when a limited number of shorelines are available and it is the most commonly applied statistical technique for expressing shoreline movement and estimating rates of change. Uncertainties for the long-term rates are also reported in units of m/yr and represent a 90% confidence interval for the slope of the regression line. This means with 90% statistical confidence that the true rate of shoreline change falls within the range defined by the reported value plus or minus the error value. The variability around the trend reflects both measurement and sampling errors. Short-term rates of shoreline change, in units of m/yr, were calculated using the endpoint method comparing the 1970s and most recent shoreline positions.
Pacific Science Center
400 Natural Bridges Drive
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
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United States Geological Survey
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The accuracy is not given or is not known.
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Pacific Science Center
400 Natural Bridges Drive
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.
Seven files comprise the ArcView shapefile: <filename>.dbf, <filename>.shp, <filename>.shx, <filename>.prj, <filename>.avl, <filename>.sbx, <filename>.sbn
Pacific Science Center
400 Natural Bridges Drive