Calculating Long-Term Shoreline Recession Rates Using Aerial Photographic and Beach Profiling Techniques

Abstract

Quantifying measurement error and precision may be the most difficult step of shoreline recession rate calculations. Calculation of long-term shoreline recession rates based on aerial photograph analysis reflect only the shoreline positions at the time of photography. Conventional methods of long-term recession rate calculation were combined with beach profiling techniques in order to quantify potential errors that can be produced by short -term variations in shoreline position. Monthly beach profiling of a typical northeastern/mid -Atlantic microtidal and wave dominated shoreline demonstrated short-term shoreline position changes of up to 20m over a one year period. Average long-term shoreline recession rates in this area were 1.2 m/yr ± 1.0 m/yr. Short-term shore line position changes were the largest source of error in the long-term recession rate measurements. This emphasizes that photographed shorelines do not necessarily represent the seasonal mean shore line position, particularly in locations where shorelines characteristically exhibit relatively large short-term variations in shoreline position.