This is a MD iMAP hosted service layer. Find more information at http://imap.maryland.gov. To quantify rates of change (erosion or accretion) along coastal and estuarine shorelines in Maryland - the Maryland Geological Survey (MGS) - in conjunction with Towson University's Center for Geographic Information Sciences (CGIS) and the U.S. Geological Survey (USGS) - installed and ran a computer program - the Digital Shoreline Analysis System (DSAS) - using as input a series of digital shoreline vectors dating from 1841-1995. Shorelines were derived from three sources: (1) maps from a Historical Shorelines and Erosion Rates Atlas (Conkwright - 1975) - (2) Coastal Survey maps (topographic or T-sheets) produced by the National Ocean Service (NOS) - a branch of the National Oceanic and Atmospheric Administration (NOAA) - and (3) a digital wetlands delineation based on photo interpretation of digital orthophoto quarter quads. DSAS constructed a 'baseline' landward of and approximately parallel to the shorelines - inserted nodes every 20 m along the baseline - and cast straight-line transects from each node - perpendicular to the baseline - across the shorelines. Based on the time elapsed and the along-transect distance between shoreline pairs - DSAS calculated rates of change for each transect. Last Updated: Feature Service Layer Link: https://mdgeodata.md.gov/imap/rest/services/Hydrology/MD_ShorelineChanges/MapServer ADDITIONAL LICENSE TERMS: The Spatial Data and the information therein (collectively "the Data") is provided "as is" without warranty of any kind either expressed implied or statutory. The user assumes the entire risk as to quality and performance of the Data. No guarantee of accuracy is granted nor is any responsibility for reliance thereon assumed. In no event shall the State of Maryland be liable for direct indirect incidental consequential or special damages of any kind. The State of Maryland does not accept liability for any damages or misrepresentation caused by inaccuracies in the Data or as a result to changes to the Data nor is there responsibility assumed to maintain the Data in any manner or form. The Data can be freely distributed as long as the metadata entry is not modified or deleted. Any data derived from the Data must acknowledge the State of Maryland in the metadata.