Study On Beach Morphodynamics And Resource Evaluation Along Leizhou Peninsula

Beach is located in the transitional zone between land and sea,formed by sands,gravels and pebbles and other loose sediments.As a good tourism and leisure resource,its tourism development value has attracted increasing attention.Since the beginning of the 21 st century,the global climate change has become increasingly apparent.Global sea level rise will cause coastal erosion and shoreline recede.The intensity and frequency of storm surges maybe increase which will further increase the intensity of coastal erosion.The mechanism of coastline change and the and beach morphological evolution have attracted widespread attention.In this paper,Leizhou Peninsula is taken as the research case.Data of beaches are investigated in the field including two typhoons processes,typhoon Kanu and strong typhoon Mangkhut.A comprehensive study has been made on the beach morphodynamics and beach resource state of Leizhou Peninsula,and the response and recovery behavior of representative beaches in the Peninsula under extreme wave conditions.Following conclusions are obtained: 1.Morphodynamics of Leizhou PeninsulaLeizhou Peninsula beaches can be divided into 6 types: reflection group,low tide terrace/reflection group(with rip current),bar-trough/intermediate state group,sandbar dissipation group,super dissipation group and low tide terrace/reflection group(without rip current).Wave,tide,sediment characteristics and coastal geological structure background have different impacts on the beach state of Leizhou Peninsula.The impacts of factors are different in different shore sections.The geological background is a factor that cannot be ignored in beach state classification.As for the traditional beach morphoynamic model ?-RTR,it pays more attention on dynamics and sedimentary factors.The classification results based on ?-RTR are slightly different from the cluster analysis results,but can effectively distinguish the beach state types on the whole.The ?-RTRmodel is an effective means to understand the beach dynamic geomorphic system.2.Storm response characteristics of the beaches along the southern Leizhou PeninsulasUnder the influence of typhoon "Kanu"(strong tropical storm),the surface sediment of the beach became coarser and the sorting became worse.The beach state changed to a more dissipated state to buffer and adapt to the energy of high-intensity waves.Influenced by headland bay orientation and size,beach profile changes were different in different beach sections or different beaches.After the typhoon,the beach may form a submerged sand bar or a beach berm on the upper part of the beach.For Dengloujiao beach,underwater reef flat,giant sandy headland affected the beach change during typhoon.The storm influence of the beach-reef flat system needs more detailed observation and further research.3.Sedimentation process and recovery mechanism of Nanshan Island beach under storm.Influenced by strong typhoon Mangkhut,the beach of Nanshan Island,located in the eastern Leizhou Peninsula,made rapid response under extreme dynamic conditions.During the whole response-recovery phase,the sediment accumulation in the supratidal zone and the sandbar in the subtidal zone interacted with each other.The intertidal zone was relatively stable without obvious erosion and deposition.Under the influence of typhoon,the surface sediments on the beach became thinner and better sorted.In the recovery stage,sediments were readjusted and distributed along the beach surface.In the restoration process,the restoration process of the supratidal zone was relatively independent and the restoration speed in the intertidal zone was relatively slow.The main reason was that the sediment transportion on the beach surface was be redistributed through the intertidal zone,which influenced the restoration speed of the subtidal zone.4.Beach resources quality evaluation of Leizhou PeninsulaAccording to the actual situation of beach resources in China,a rural beach evaluation system is established.The evaluation system selects 14 natural beach,mainly considering the geological and geomorphic state of the beach,the characteristics of beach sediments and sedimentary dynamics,and propose a dynamic safety evaluation operation method under the condition that the marine dynamic factors are difficult to obtain.The evaluation system was used to evaluate the quality of rural beaches in Leizhou Peninsula.Results showed that Baisha Bay,Qing'an Bay,Duzai and Xingou beaches in Leizhou Peninsula are of high quality.Considering the beach quality,geographical location,social conditions,radiation,the Baisha Bay and the Qing'an Bay have more advantages in development and utilization.In addition,the beach evaluation system should pay attention to basic theoretical issues such as beach morphodynamics.By understanding the beach state,the underwater topography and beach safety of the beach can be mastered,and the development,utilization,management and protection of beach resources can be better carried out.