On average,five to six storms occur in the Qiongzhou Strait every year,causing significant damage to coastal geomorphology and several property losses.Tropical Storm Bebinca is the most unusual and complex storm event...On average,five to six storms occur in the Qiongzhou Strait every year,causing significant damage to coastal geomorphology and several property losses.Tropical Storm Bebinca is the most unusual and complex storm event that has occurred in this region over the last 10 years.To detect the high-frequency beachface responses to the storm,a pressure sensor was deployed in the surf zone to record the free sea surface height,and the heights of grid pile points on the beachface were measured manually to determine beach elevation changes during this storm.Empirical Mode Decomposition and related analysis techniques were used to analyze the high-frequency topography and wave data.The results showed that:(1)the beachface response process occurred in three stages.The first stage was the rapid response stage,wherein the spring tide berm began to erode significantly,and the front edge of the beach berm reacted closely.The two beach sections resisted the harmful energy of the main storm.In the second stage,the beach slope increased after a large sediment loss on the beach berm and its front edge.To adapt to the storm energy,the beach at the low tide line began to erode,and the beach slope decreased.In the third stage,after the storm turned,the wave energy was significantly attenuated,and the beach berm eroded to resist the residual wave energy.The beachface began to oscillate and recover.(2)The main wave surface was the superimposed product of a few internal mode functions.Similar results were observed in beachface changes.High-frequency driving factors determine the local characteristics of beach evolution,and low-frequency driving factors determine the beach evolution trend.(3)The response of sediment to the storm was not a single sea-transportation,but a single-or two-way conversion driven by factors such as wave energy,swash flow,and secondary wave breaking.(4)TheΩ-RTR model is not completely applicable to beach states that undergo rapid changes during storms.Therefore,it is necessary to carry out further research on beach state identification during storms.展开更多
Beach erosion has occurred globally in recent decades due to frequent and severe storms.Dongsha beach,located in Zhujiajian Island,Zhejiang Province,China,is a typical embayed sandy beach.This study focused on the mor...Beach erosion has occurred globally in recent decades due to frequent and severe storms.Dongsha beach,located in Zhujiajian Island,Zhejiang Province,China,is a typical embayed sandy beach.This study focused on the morphodynamic response of Dongsha beach to typhoon events,based on beach topographies and surficial sediment characteristics acquired before and after four typhoon events with varying intensities.The four typhoons had different effects on the topography and sediment characteristics of Dongsha beach.Typhoons Ampil and Danas caused the largest(-51.72 m3/m)and the smallest erosion(-8.01 m3/m),respectively.Remarkable alongshore patterns of beach profile volumetric changes were found after the four typhoon events,with more erosion in the southern and central parts of the beach and few changes in the northern part.Grain size coarsening and poor sorting were the main sediment patterns on the beach influenced by different typhoons.Typhoons that occurred in the same year after another typhoon enhanced the effect of the previous typhoon on sediment coarsening and sorting variability,but this cumulative effect was not found between typhoons that occurred during different years.A comparison of the collected data revealed that the topographic state of the beach before the typhoon,typhoon characteristics,and tidal conditions were possible reasons for the difference in the responses of Dongsha beach to typhoon events.More severe beach erosion was caused by typhoons with higher intensity levels and longer durations,and high tide levels during typhoons can determine the upper limit of the beach profile erosion site.Taken together,these results can be used to improve beach management for storm prevention.展开更多
基金The National Natural Science Foundation of China under contract Nos 42176167 and 41676079the Project of Enhancing School with Innovation,Guangdong Ocean University under contract No.Q18307.
文摘On average,five to six storms occur in the Qiongzhou Strait every year,causing significant damage to coastal geomorphology and several property losses.Tropical Storm Bebinca is the most unusual and complex storm event that has occurred in this region over the last 10 years.To detect the high-frequency beachface responses to the storm,a pressure sensor was deployed in the surf zone to record the free sea surface height,and the heights of grid pile points on the beachface were measured manually to determine beach elevation changes during this storm.Empirical Mode Decomposition and related analysis techniques were used to analyze the high-frequency topography and wave data.The results showed that:(1)the beachface response process occurred in three stages.The first stage was the rapid response stage,wherein the spring tide berm began to erode significantly,and the front edge of the beach berm reacted closely.The two beach sections resisted the harmful energy of the main storm.In the second stage,the beach slope increased after a large sediment loss on the beach berm and its front edge.To adapt to the storm energy,the beach at the low tide line began to erode,and the beach slope decreased.In the third stage,after the storm turned,the wave energy was significantly attenuated,and the beach berm eroded to resist the residual wave energy.The beachface began to oscillate and recover.(2)The main wave surface was the superimposed product of a few internal mode functions.Similar results were observed in beachface changes.High-frequency driving factors determine the local characteristics of beach evolution,and low-frequency driving factors determine the beach evolution trend.(3)The response of sediment to the storm was not a single sea-transportation,but a single-or two-way conversion driven by factors such as wave energy,swash flow,and secondary wave breaking.(4)TheΩ-RTR model is not completely applicable to beach states that undergo rapid changes during storms.Therefore,it is necessary to carry out further research on beach state identification during storms.
基金The Zhejiang Provincial Natural Science Foundation of China under contract No.LHZ22D060001the Scientific Research Funds of the Second Institute of Oceanography,Ministry of Natural Resources under contract Nos JG2315 and XRJH2309the National Key R&D Program of China under contract No.2022YFC3106200.
文摘Beach erosion has occurred globally in recent decades due to frequent and severe storms.Dongsha beach,located in Zhujiajian Island,Zhejiang Province,China,is a typical embayed sandy beach.This study focused on the morphodynamic response of Dongsha beach to typhoon events,based on beach topographies and surficial sediment characteristics acquired before and after four typhoon events with varying intensities.The four typhoons had different effects on the topography and sediment characteristics of Dongsha beach.Typhoons Ampil and Danas caused the largest(-51.72 m3/m)and the smallest erosion(-8.01 m3/m),respectively.Remarkable alongshore patterns of beach profile volumetric changes were found after the four typhoon events,with more erosion in the southern and central parts of the beach and few changes in the northern part.Grain size coarsening and poor sorting were the main sediment patterns on the beach influenced by different typhoons.Typhoons that occurred in the same year after another typhoon enhanced the effect of the previous typhoon on sediment coarsening and sorting variability,but this cumulative effect was not found between typhoons that occurred during different years.A comparison of the collected data revealed that the topographic state of the beach before the typhoon,typhoon characteristics,and tidal conditions were possible reasons for the difference in the responses of Dongsha beach to typhoon events.More severe beach erosion was caused by typhoons with higher intensity levels and longer durations,and high tide levels during typhoons can determine the upper limit of the beach profile erosion site.Taken together,these results can be used to improve beach management for storm prevention.
