Mean high water (MHW) shorelines along the coast of California used to calculated shoreline change from 1998 to 2016
This dataset contains mean high water (MHW) shorelines for sandy beaches along the coast of California for the years 1998/2002, 2015, and 2016. The MHW elevation in each analysis region (Northern, Central, and Southern California) maintained consistency with that of the National Assessment of Shoreline Change. The operational MHW line was extracted from Light Detection and Ranging (LiDAR) digital elevation models (DEMs) using the ArcGIS smoothed contour method. The smoothed contour line was then quality controlled to remove artifacts, as well as remove any contour tool interpretation of human-made infrastructure (such as jetties, piers, and sea walls), using satellite imagery from ArcGIS.
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Barnard, Patrick L., Smith, Schuyler A., and Foxgrover, Amy C., 20201231, Mean high water (MHW) shorelines along the coast of California used to calculated shoreline change from 1998 to 2016: data release DOI:10.5066/P91QSGXF, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.
Barnard, Patrick L., Smith, Schuyler A., and Foxgrover, Amy C., 2020, California shorelines and shoreline change data, 1998-2016: data release DOI:10.5066/P91QSGXF, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.
Planar coordinates are encoded using row and column
Abscissae (x-coordinates) are specified to the nearest 2.000000
Ordinates (y-coordinates) are specified to the nearest 2.000000
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257222.
California shorelines for the years 1998/2002, 2015, and 2016
Shapefiles consisting of shoreline position, defined by MHW, for discrete years and regions of the state: Northern California (NorCal), Central California (CenCal), and Southern California (SoCal).
(Source: originators at United States Geological Survey, Pacific Coastal and Marine Science Center)
Effective date of MHW shoreline location from all contributing data
(Source: producer defined)
Range of values
Horizontal uncertainty of shoreline location
(Source: producer defined)
This work is one portion of ongoing coastal monitoring efforts for California and the western United States. These data provide an estimate of past shoreline positions and shoreline change throughout California, with the goal of understanding how shorelines change over time and in response to El Nino events. The data are intended for policy makers, resource managers, science researchers, students, and the general public. These data can be used with geographic information systems or other software to identify and assess possible areas of vulnerability. These data are not intended to be used for navigation.
MHW shoreline positions were digitized from multiple LiDAR data sets within the full geographic extent of the study area from 1998 - 2016.
SoCal LiDAR (source 2 of 2)
Data from Southern California Coastal Response to 2015-2016 El Nino, 2018, Data from Southern California Coastal Response to the 2015-2016 El Nino: University of California San Diego Library Digital Collection, online.
High-accuracy LiDAR data were downloaded from NOAA Digital Coast in the form of digital elevation models (DEMs) for both pre-El Nino (2015) and post-El Nino (2016), as well as 1998/2002 for perspective. Due to sparse LiDAR data coverage in southern California, SoCal LiDAR from UC San Diego Library Collections was used in this region.
Data sources used in this process:
Date: 15-Aug-2017 (process 2 of 4)
The operational MHW line was extracted using the ArcGIS smoothed contour method with the smoothing tolerance parameter set to 30 m alongshore. The NAVD88 datum was used for the MHW elevation. The mean high water (MHW) shoreline elevation in each analysis region (Northern, Central, and Southern California) maintained consistency with that of the National Assessment of Shoreline Change.
Date: 01-Apr-2018 (process 3 of 4)
The smoothed contour line was then quality controlled to remove artifacts, as well as remove any contour tool interpretation of human-made infrastructure (such as jetties, piers, and sea walls), using satellite imagery available in ArcGIS.
Date: 15-Jun-2018 (process 4 of 4)
Using the uncertainty values reported in the DEM metadata, the DEM vertical uncertainty was converted to horizontal uncertainty using the slope of the beach at 50-meter points along the MHW line, using the following steps: Slope maps were created from the DEMS within ArcMap using the 3D Analyst Raster Surface Slope tool. Next, the MHW lines were converted to 50-meter-spaced points, at which the slope value of the DEM was extracted. The average of these values for North, Central, and Southern California was used to convert the vertical uncertainty of the DEM to a horizontal uncertainty. Finally, the horizontal uncertainty and converted vertical uncertainty were summed in quadrature to calculate a final uncertainty value associated with each shoreline.
How well have the observations been checked?
Estimates of shoreline position accuracy using mean high water lines derived from LiDAR DEMS have been cross checked with satellite-derived shorelines, shorelines derived by the national assessment of shoreline change, and in-situ data collected by GPS surveys. However, lack of alternate data collection methods during this time limits the amount of validation possible for this dataset.
How accurate are the geographic locations?
A formal accuracy assessment of the shorelines was conducted for each region. The uncertainty associated with each LiDAR-derived shoreline is comprised of the vertical and horizontal uncertainty of the source DEM. Average beach slopes for North, Central, and Southern California were calculated and used to convert the reported vertical uncertainty of the DEM to a horizontal uncertainty. The derived horizontal uncertainty and vertical uncertainty were summed in quadrature to calculate a final uncertainty value associated with each shoreline. The horizontal accuracy (or uncertainty) for each shoreline is included within this geospatial dataset and was determined at the 95 percent confidence level.
How accurate are the heights or depths?
Although no formal vertical position accuracy assessment was conducted, the uncertainty associated with each LiDAR-derived shoreline is comprised of the vertical (and horizontal) uncertainty of the source DEM. It is assumed that uncertainty associated with the extraction of the MHW line from a DEM is negligible.
Where are the gaps in the data? What is missing?
These geospatial projections are complete. Any gaps in these data, if applicable, are a consequence of nonexisting data or existing data that did not meet quality assurance standards. Users are advised to read the rest of the metadata record and references carefully for additional details.
USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data.
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What's the catalog number I need to order this data set?These data are available in shapefile format. Each shoreline year (1998/2002, 2015, and 2016) and region (Northern, Central, and Southern California) is available as a separate shapefile. CSDGM FGDC-compliant metadata is zipped with the dataset.
Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
The .zip file includes shapefiles of shorelines and the XML (.xml) version of the metadata
in format shapefile
(version ArcGIS 10.6)
Features are in shapefile format and are projected in NAD 1983 UTM zone 10 coordinates with a geographic coordinate system of GCS North American 1983.