Rapid Morphological Changes Caused by Intensive Coastal Development in Longkou Bay, China

Analyses of the evolution of subaqueous topography in coastal water provide an understanding of the effects of intensive coastal development on bays and estuaries. Analysis of a series of historical bathymetric acoustic surveys has revealed large changes in morphology from the 1960s to 2010s in Longkou Bay, China. Water depths were extracted from digitized admiralty charts to explore the accretion-erosion characteristics in a geographical information system environment, providing quantitative estimates of morphological changes. Multibeam echosounders were used to map and analyze the geomorphologic features caused by the construction of artificial islands. Results illustrated that the shoreline and bathymetry of Longkou Bay have changed rapidly in recent decades. The subaqueous area decreased by about 15%, while land area increased by more than 13 km(2) in the study area during the last 50 years. From the 1960s to 1990s, the evolution of Longkou Bay was mainly governed by natural processes with a patchy distribution of deposition and erosion, and there were few signs of change related to large-scale human activities. During the period from the 1990s to 2010s, intensive coastal developments, including large port engineering projects, channel dredging, and construction of artificial islands, became the main processes affecting morphological changes in Longkou Bay. The high-resolution bathymetric results near the artificial island showed that the seafloor was dredged at many sites, leaving large areas of borrow pits. The sudden change of the underwater topography will lead to the destruction of local benthic habitat, and effective measures need to be taken to protect and remediate the heavily disturbed subaqueous environment.