Spatial and temporal shoreline changes of the southern Yellow River (Huanghe) Delta in 1976-2016

In this study, 364 Landsat satellite images were utilized to study the spatial and temporal shoreline changes of the southern Yellow River Delta in 1976-2016, and a new method revised and improved after Zhang et al. (2016) was proposed. By employing that method, the calculated sea levels calculated from simulated tidal heights and instantaneous shoreline positions rather than simulated tidal heights were used to correct fluctuations in instantaneous shoreline positions caused by tidal height and seasonal sea level changes and other random sea level fluctuations. When calculating the shoreline erosion rates and beach slopes, a statistical analysis of a large number of corrected shoreline positions was used to reduce the influence of random errors that were mainly caused by waves and other casual factors. The shoreline erosion rates and beach slopes presented in this paper are therefore more precise and reliable than those derived in previous studies, which only used two satellite images. The results of this study show that the shoreline of the southern Yellow River Delta primarily experienced gradual erosion during 1976-2016, with an average erosion rate of 26.9 m/year. The average shoreline erosion rate increased from 24.9 m/year in 1976-1996 to 34.9 m/year in 1996-2016-an increase of 40%-probably due to the reduction in sediment discharge and shifting northward course of the Yellow River after 1996. The shoreline erosion rate of the central coast decreased from 50.2 m/year in 1976-1996 to 27.1 m/year in 1996-2016-a decrease of 46%-probably due to the protection offered by coastal hard structures. The average shoreline erosion rate caused by relative sea level rise was 8.5 m/year or 32% of the total average shoreline erosion rate. Relative sea level rise plays an important role in the erosion of the southern Yellow River Delta due to its flat beach. The beach slope of the southern Yellow River Delta was flat and stable in 1976-2016, and the average slope over most of the beach was 0.043%.