THE DIGITAL SHORELINE ANALYSIS SYSTEM (DSAS), A GEOSPATIAL TOOL FOR EVALUATING SHORELINE CHANGE

The Digital Shoreline Analysis System (DSAS) was first released by the U.S. Geological Survey in 1992 as a software tool to help scientists and managers assess rates of shoreline change in diverse coastal settings using statistical techniques. DSAS facilitates the estimation of shoreline change rates by automating much of the measurement and computation processes. The software uses a reference baseline method as the starting point for transects that cross through a time series of shoreline positions. The user supplies sequential shoreline vectors and a reference baseline as inputs and DSAS generates orthogonal transects from the baseline that intersect the shorelines. These transect-shoreline intersections provide the measurement locations used to estimate rates of change for the time series data. Output data include a variety of rate metrics including end-point and several regression methods (ordinary least squares, weighted least squares, and least median of squares). Standard error, correlation coefficient, and confidence interval are computed for the regression methods. Software development has focused on improving both statistical output options and data management. Calculations are performed using an external module included in the DSAS distribution that provides users the option of developing their own calculation modules. In addition to statistical outputs, DSAS automatically generates metadata when transect locations are created and when rate calculations are performed. DSAS captures user-input variables and processing steps within the transect metadata file, providing automated recordkeeping of calculation parameters and settings used when generating transects and performing rate of change calculations. The software presently works as an extension within ESRI’s ArcMap application but an open-source, web-based application is currently being considered. DSAS is available free of charge and has been used worldwide as a method for assessing shoreline change.