Using free satellite imagery to study the long-term evolution of intertidal bar systems

Abstract

Intertidal bar systems (IBSs) are ubiquitous geomorphic features on beaches and play an important role in nourishing and protecting beaches. IBSs can also pose a significant threat to nearshore swimmers and ships. Therefore, studying the evolution of IBSs will yield valuable insight in understanding the dynamic nature of beaches, provide help in protecting beaches from current widespread erosion, and provide early warning of potential hazards. However, the data used by previous approaches are commonly site-specific and labor-intensive (or expensive), which restricts their application. This paper introduces a new approach for studying the long-term evolution of IBSs based on free satellite imagery. This satellite approach uses three methods, namely bar, trough, and breaker methods, to directly recognize the planar positions of IBSs. This approach has low requirements on satellite images, therefore it is conducive to making full use of the precious historical satellite images to study the highly dynamic evolution of IBSs in recent decades, which cannot be measured and photographed again. Based on the terabytes of free satellite imagery, this approach can be used on almost all beaches in the world, which will greatly expand the study object pool and facilitate the selection of study objects in different types of marine conditions. This paper also introduces how to use the satellite approach based on a case study. The case study quantitatively revealed the forming, migration, decay, and distribution of the IBSs around the Feng River mouth in China, evaluated the errors of the satellite-derived position and migration rate, analyzed the main factors affecting their evolution, and discussed the main factors influencing their evolution and their influence on the evolution of adjacent beaches. • A new satellite approach was provided to study the evolution of intertidal bar systems. • The approach uses bar, trough, and breaker methods to recognize the position of IBS. • The long-term evolution of IBSs around a river mouth was revealed and analyzed.