The different erosion fate of the headland-embayed beaches on the muddy and sandy coasts of China

Abstract

China’s beaches exhibit different geomorphic characteristics depending on location. Due to increasing contemporary climate change, induced storm activities and human activities, beaches along the Chinese coast have been exposed to the risk of erosion. This article examines the different shoreline evolution processes from 1973 to 2021 as well as the erosion vulnerability of 9 headland-embayed beaches (of which 5 beaches, each at Baishawan, Dasha, Dongdan, Nanshajiao, and Mushao are on the muddy coast in Southern China and 4 beaches, namely, Bathing Beach 1, 2, 3 and Shilaoren Beach are on the sandy coast in Northern China) based on the inherent geomorphic characteristics and nearshore hydroclimatic factors of the beaches. In the analysis, there were 3 stages. During the first stage, erosion dominated both the muddy and sandy coasts as a result of intense storm conditions. During the second stage, the beaches had earlier recovered as a function of natural processes, however, storm activities later eroded the beaches. During the third stage, most of the beaches accreted as a result of coastal engineering interventions and beach nourishment project. The shoreline analysis results indicate that beaches on the muddy and sandy coasts have been eroding in the long term. During the first erosion stage, erosion is more severe on the muddy coast than on the sandy coast in the short term. On the sandy coast, the beaches recorded severe erosion from 1973 to 1998. Of the 9 beaches, the most eroded location was at Dasha on the muddy coast (LRR: –5.315 m/y; EPR: –5.671 m/y; NSM: –141.94 m) between 1974 and 1998. In summary, beaches on muddy coasts are more vulnerable to erosion than those on sandy coasts. On the muddy coast, there has been a shortage in the supply of sediment from the Yangtze River-derived sediment to the coast. The primary source of sand material for the studied beaches on the muddy coast has been the regular storm condition that changes the sand-mud transition line on the coast. For the sandy beaches, the primary factor responsible for the vulnerability and beach modification includes a shortage in the natural supply of beach material and storm activities, however, recent beach nourishment and coastal protection procedures are gradually stabilizing the beaches. Ultimately, the outcome of this research is suitable for beach management procedures on the Chinese coast.