Spatio-temporal evolution of coastlines of sand-barrier lagoons over 26 years through historic Landsat imagery in Lingshui County, Hainan Province, China

Coastlines of sand-barrier lagoons have provided significant locations for coastal economic development as has frequently occurred along the eastern coast of Hainan Island in southern China. Here, increased levels of human activity have greatly destabilized this ecosystem, subjecting it to major damage. The present study used innovative technology to classify and evaluate six phases of overlapping coastlines in Li’an and Xincun Lagoons in Lingshui County in southeastern Hainan Island between 1987 and 2013. This included the retrieval and integrated analysis of remote sensing images that was combined with data related to ocean dynamics and bathymetric surveys. Average historic high-tide lines were acquired by extracting humidity parameters from images using the Kauth-Thomas Transformation. Variations in the position and length of multiple coastlines were analyzed using GIS with a mathematical and statistical approach. The lengths of anthropogenic coastlines increased by 50% and moved seawards by 94.04 m in Li’an and 102.56 m in Xincun. Meanwhile, the areas in the Xincun and Li’an Lagoons decreased from 21.17 km2 to 19.43 km2 (−8.2%) and 9.94 km2 to 7.92 km2 (20.3%), respectively. Extensive human activity along the coastlines, such as saltwater aquaculture and farming, salt plant, and land reclamation, have profoundly altered the sedimentary geomorphology, local hydrodynamics, and the ecosystem itself. Consequently, the coastlines in Xincun and Li’an Lagoons in this newly designated pilot tourism city became vulnerable to modification. This research fills a critical gap related to the evolution of historical coastlines and provides an inventory of coastlines in support of coastal management.