NOAA Shoreline Website

A Guide to National Shoreline Data and Terms

Calculating Shoreline Change


Add historical and modern vector shorelines

Historic and modern shorelines can be used as a basis for determining shoreline change rates. It is helpful when determining long-term shoreline change to have sequential historic shorelines dating as far back as 100 yrs to the most recent available shoreline.


Draw a baseline

The baseline is an arbitrary line that can be drawn either shoreward or landward of shorelines to serve as the origination point of transects used for calculations.


Cast transects

Transects are cast either manually or using an automated system (ie. DSAS). Automated systems have the ability to cast transects quickly over large areas.


Calculate the rate of change

The rate of change can be determined by measuring the distance between the shoreline/transect intersection points. Linear regressions are common statistical analyses for determining shoreline change rates.