Shoreline time series analysis through the Isoradiometric method: Bridging landscape evolution and coastal management

Abstract

The increasing availability of remotely sensed data has enhanced our ability to monitor coastal evolution, yet extracting reliable time series for long-term analysis remains a challenge. This study evaluates the effectiveness of the Isoradiometric shoreline extraction Method in producing consistent time series data across different spatial and temporal scales. We applied the method to about 150 multispectral satellite images spanning 40 years, covering two sandy beaches along Sicily’s coast in the central Mediterranean Sea. Our validation approach focused on assessing method consistency across datasets with different spatial resolutions and revisit times. By comparing Landsat and PlanetScope data, we demonstrated that while high-resolution products capture greater variability in shoreline position, lower-resolution but longer time-span observations effectively identify underlying evolutionary trends. The analysis revealed that manual digitization captures instantaneous swash positions, while the Isoradiometric Method consistently identifies stable morphological features between the low tide terrace and berm, providing more reliable indicators of actual coastal change. This multi-resolution approach proved effective in distinguishing between method-related outliers and paroxysmal events, with the latter typically detected across multiple datasets at corresponding timeframes. The systematic application of the Isoradiometric Method successfully characterized both natural variability patterns and anthropic impacts, providing quantitative baselines for interpreting Quaternary coastal processes while offering practical insights for shoreline monitoring and coastal management strategies. Moreover, we calculated the shifts’ gradient to quantify the rate of change in shoreline position. These results demonstrate: i) the necessity of creating shoreline time series as a tool for geological interpretation through the principle of actualism and as a framework for rationalizing contemporary shoreline monitoring approaches; ii) the Isoradiometric Method enables accurate Earth Observation image processing for this purpose.