Efficient measurement of large-scale decadal shoreline change with increased accuracy in tide-dominated coastal environments with Google Earth Engine

摘要

Most of the worlds' population relies on the processes and ecosystems in the coastal zone. Understanding the long-term change of coastlines is critical for the effective management of these complex, and heavily utilised regions. There has been a recent increase of studies focused on large-scale shoreline change mapping. However, most current methods are optimized for extracting shorelines of wave-dominated sandy beaches, which are only 30% of the global coasts, resulting in uncertainty for other environments such as tidal flats and bedrock. Here, we propose a new shoreline change mapping workflow, using the Landsat archive and Google Earth Engine, which increases compute efficiency and is suitable for retrieving shoreline changes for various coastal landforms at high tide instead of mean sea level. By validating against regional and continental datasets in Australia, we found the approach here produced high mapping accuracy and showed particularly better performance at tide-dominated coasts, where tidal flats and intertidal bars and ridges are present, when compared to past approaches. This is an important step forward since tide-dominated and tide-modified coasts are widely distributed at tropical low latitudes. We also explored the global application of the proposed method and derived hotspots of shoreline erosion and accretion that agreed with multiple regional studies across the world. Most of these hotspots were related to river sediment discharge and human intervention on the coast, as expected. Although it requires further validation, the global application of our method demonstrates the significance of this approach in identifying potential threats to coastal zones, especially in complex tide-dominated environments, which can facilitate effective coastal management.