Western Coastal and Marine Geology
By Cheryl Hapke1 and David Reid2
1U.S. Geological Survey, Patuxent Wildlife Science Center, Coastal Field Station, Department of Geosciences, University of Rhode Island, Kingston, RI 02881
2U.S. Geological Survey, Pacific Science Center, 400 Natural Bridges Drive, Santa Cruz, CA 95060
The Coastal and Marine Geology Program of the U.S. Geological Survey has generated a comprehensive data clearinghouse of digital vector shorelines and shoreline change rates for the sandy shoreline along the California open coast. These data, which are presented herein, were compiled as part of the U.S. Geological Survey's National Assessment of Shoreline Change Project.
Beach erosion is a chronic problem along many open-ocean shores of the United States. As coastal populations continue to grow and community infrastructures are threatened by erosion, there is increased demand for accurate information including rates and trends of shoreline migration. There is also a critical need for shoreline change data that is consistent from one coastal region to another. One purpose of this work is to develop standard, repeatable methods for mapping and analyzing shoreline movement so that periodic, systematic, and internally consistent updates of shorelines and shoreline change rates can be made at a National Scale.
This data compilation for open-ocean, sandy shorelines of the California coast is one in a series that already includes the Gulf of Mexico and the Southeast Atlantic Coast (Morton et al., 2004; Morton et al., 2005) and will eventually cover Washington, Oregon, and parts of Hawaii and Alaska. Short- and long-term shoreline change evaluations are determined by comparing the positions of three historical shorelines digitized from maps, with a modern shoreline derived from LIDAR (light detection and ranging) topographic surveys. Historical shorelines generally represent the following time-periods: 1850s-1880s, 1920s-1930s, and late 1940s-1970s. The most recent shoreline is from data collected between 1997 and 2002. Long-term rates of change are calculated by linear regression using all four shorelines. Short-term rates of change are end-point rate calculations using the two most recent shorelines. Please refer to our full report on shoreline change of the California coastline at http://pubs.usgs.gov/of/2006/1219/ for additional information regarding methods and results (Hapke et al., 2006).
Data in this report are organized into downloadable layers by region (Northern, Central and Southern California) and are provided as vector datasets with metadata. Vector shorelines may represent a compilation of data from one or more sources and these sources are included in the dataset metadata. This project employs the Environmental Systems Research Institute's (ESRI) ArcGIS as it's GIS mapping tool and contains several data layers (shapefiles) that are used to create a geographic view of the California Coast. These vector data form a basemap comprised of polygon and line themes that include a U.S. coastline (1:80,000), U.S. cities, and state boundaries.
Data in this publication are intended to be integrated into a GIS. A GIS is defined as a system of hardware and software to support the display, manipulation, and analysis of spatial data for mapping and complex data analysis. This integrated package provides researchers the ability to analyze and map the various datasets to help with research, economic and social policy-making decisions regarding the environment.
All of the files necessary to run shoreline change analysis are provided. This includes ten GIS data layers (shapefiles) for each region along the sandy shoreline of California. These include: three historical and one modern vector shorelines, an offshore baseline used for generating shore-normal transects, shore-normal transects for long- and short- term shoreline change rates, transect/shoreline intersection positions for long- and short-term shoreline change rates as a point shapefile, and a vector shapefile containing bias values for the MHW - HWL shoreline proxy offsets. The GIS data layers from this publication are cataloged below by region for easy access. Please refer to http://woodshole.er.usgs.gov/project-pages/dsas/ for information about the Digital Shoreline Analysis System (DSAS) used for the analysis of this data.
Information about the field activities involved in the collecting of data in this report can be found on the Coastal and Marine Geology InfoBank web site (http://walrus.wr.usgs.gov/infobank/):
Morton, R.A., Miller, T.L. and Moore, L.J., 2004, National Assessment of shoreline Change: Part 1: Historical shoreline change and associated land loss along the U.S. Gulf of Mexico: U.S. Geological Survey Open-file Report 2004-1043 (http://pubs.usgs.gov/of/2004/1043)
Morton, R.A., Miller, T.L., 2005, National Assessment of shoreline Change: Part 2: Historical shoreline change and associated land loss along the U.S. South East Atlantic Coast: U.S. Geological Survey Open-file Report 2005-1401 (http://pubs.usgs.gov/of/2005/1401)
Hapke, C.J., Reid, D., Richmond, B.M., Ruggiero, P., and List, J., 2006, National Assessment of Shoreline Change: Part 3: Historical Shoreline Change and Associated Coastal Land Loss Along Sandy Shorelines of the California Coast: U.S. Geological Survey Open-file Report 2006-1219 (http://pubs.usgs.gov/of/2006/1219)
Go to the old Version 1.0 data (version1 folder). The data in v. 1.0 is in UTM projected coordinates. These have now been replaced in v. 1.1 with the data in geographic coordinates. If you want to use the other system, those data are available here.