Maine Beach Mapping Program Shoreline Changes
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Data Description and Usage
This dataset includes surveyed shoreline positions for most of the larger beach systems along the southern to mid-coast Maine coastline in York, Cumberland, and Sagadahoc counties. Data were collected using a Leica GS-15 network Real Time Kinematic Global Positioning System (RTK-GPS), and in areas with poor cellular coverage, an Ashtech Z-Xtreme RTK-GPS. Both systems typically have horizontal and vertical accuracies of less than 5 cm. In general, surveys are attempted to be repeated at approximately the same month in each consecutive survey year, however this is not always possible. As a result, the number of available shoreline positions may vary by beach.
Using the shoreline positions and guidance from the USGS Digital Shoreline Analysis System (DSAS) statistics are calculated for each transect. MGS wrote a python-based script following protocols outlined in the DSAS Manual that allows for the calculation of different shoreline change rates and supporting statistics. This was done so that MGS no longer needed to depend on USGS updates to the DSAS software to keep current with ArcGIS software updates. The script casts shoreline-perpendicular transects at a set spacing (in this case, 10-m intervals along the shoreline), from a preset baseline (located landward of the monitored shorelines), and calculates a range of shoreline change statistics.
In 2017, MGS additionally mapped the mean high water (MHW) line along southern Maine’s beaches. This was done by mapping the +1.4 m (NAVD88) contour along the beach using the RTK-GPS. By measuring the distance between the MHW and the more landward vegetation line (or wall line), one can calculate the dry beach width.
These data are meant to help inform decisions at the local, regional, and state-level for beach management. Users must assume responsibility in determining the usability of this data for their purposes. Metadata is included for all of the downloadable layers and should be reviewed for more specifics on how these data were created. Neither the Maine Geological Survey nor the Department of Agriculture, Conservation and Forestry, nor its employees or agents: (1) make any warranty, either expressed or implied for merchantability or fitness for a particular purpose, as to the accuracy or reliability of the information shown on the map; nor are they (2) liable for any damages, including consequential damages, from using the map or the inability to use the map.
Frequently Asked Questions
The frequently asked questions provide more information about how the data layers were created, what they should be used for, usage limitations and general information on shoreline change in Maine.
The beach mapping shoreline change layers can be downloaded as shapefiles for use in any GIS software to perform further spatial analysis.
Contact the Maine Geological Survey with questions at: firstname.lastname@example.org