Study on coastal sediment budget imbalance in cells resulted from land cover change in the savanna desertification area, west Hainan Island (China)

Coastal zone construction has developed rapidly in recent years in the western region of Hainan Island (China). The study area is the only savanna desertification zone in China which has been suffering severe coastal erosion and accretion in the past 2 decades. To better adapt to the environment of coastal area and protect its resources, we must understand its sedimentary environment fully. This work was based on collecting environmental data and analyzing climatic factors in the study area to better understand the processes of sediment dynamics. Field observation was carried out in the study area, with satellite image analysis and software simulation; detailed studies were made on the evolution process of the shoreline, the stability of the shoreline and the sediment level in the last 20 years. On this basis, the conceptual model of sediment transport is presented, and the coastal dune can be used as a transport engine to drive sediment migration between coastal cells and maintain the stable development of the coastal area. Under the same dynamic conditions, when the forest replaces the natural coastal dunes, the sediment transport path is blocked. This will cause accumulation on the upstream flank and erosion of the downstream flank. Coastal geomorphology, including beach in tidal area and dunes along terrestrial zone, has been undergoing severe change in study area in the past 2 decades. Humans tend to change the natural environment according to their interests, and the feedback mechanism of the natural environment is often characterized by the hysteresis effect, which is not worth losing in the long run. We must respect nature and reduce unnecessary environmental damage.