Shoreline extraction and analysis of its seasonal evolution under wind effects along the central coast of Vietnam

Vietnam's coastal zone extends for 3260 km along the Western Pacific, an area that experiences a high number of tropical cyclones each year.  Approximately 24% of the coastline suffers from moderate to severe erosion. The central region of Vietnam, in particular, experiences a tropical monsoon climate characterized by two distinct seasons: summer monsoon (southwest monsoon) and winter monsoon (northeast monsoon). This climate leads to exceptional morphological evolution, with episodes of accretion and erosion. Understanding and identifying the specific driving force of shoreline change over space and time are crucial for coastal management. This study demonstrates a close relationship between monsoon winds and seasonal shoreline fluctuations. By analysing  shoreline positions extracted using various optical bands of satellite image from different satellite missions such as Sentinel 2, Landsat 5, 7, and 8, from 1993 to 2019, we reveal that seasonal shoreline changes are driven to a great extent by seasonal sea level variations, a direct consequence of monsoon winds. Furthermore, the study also investigated shoreline changes due to sediment transport using an empirical model. The analysis found that in some regions, sediment transport has a relatively minor impact on seasonal shoreline variation compared to the influence of wind setup during the study period.