To explore the nourishment effect and disaster reduction efficiency of a fully dissipative dry beach under the impact of storms, this paper uses the measured topography and hydrodynamic data to establish a one-dimensional numerical model of the XBeach beach profile. By numerically modeling the change in the nourished profile for different dry beach widths under normal waves and storm conditions and the recovery process of the profile after the storm, the degree of response in dry beach nourishment for the fully dissipative beach is analyzed. The results show that under normal wave conditions, the response of the nourished dry beach is obvious. Sediment on the dry beach erodes heavily, and the shoreline moves landward over a long distance. With the increase in the width and size of the dry beach, the wave height at the bottom of the backshore profile decreases, the wave height attenuation rate increases continuously, and the wave elimination effect is remarkable. When the storm incident wave intensifies, the wave height attenuation rate of the nourished dry beach decreases, indicating that the smaller the storm intensity is, the more significant the wave reduction effect of the nourished dry beach is. At the same time, different profile arrangements of nourished dry beaches suffer from different degrees of erosion under storm conditions, with significant changes in profile morphology. With intensified storm action, the intensity of sediment erosion in the nourished dry beach increases, the nourishment is weakened, and the recovery effect of the profile after the storm is not obvious. The results of the numerical modeling highlight that the dry beach nourishment method can resist storms to a certain extent, but the overall effect is relatively limited.

Based on the measured beach profile data of Sanzhou Bay from 2015 to 2019, an erosion hotspot was identified along the Shanwei coastline of eastern Guangdong, where the maximum retreat distance of the shoreline exceeded 80 m and the erosion rate was more than 20 m/a. To determine the time at which the erosion hotspot started and the potential causes of its formation, this study used 63 Landsat satellite images from 1986 to 2019 to construct a time series of shoreline positions over the past 30 years by extracting their high-tide shorelines. Next, the M-K trend test method was introduced to evaluate the non-linear shoreline behavior based on the single-transect method. The results showed that the time of approximately 2013 marked the start of the erosion hotspot, the erosion hotspot was characterized by erosion rates of more than 2 m/a (a maximum rate of 31.6 m/a), and the affected shoreline more than 4.3 km from 2013 to 2019. Furthermore, this erosion hotspot was proved to be caused by artificial sand mining in the nearshore zone, which destroyed the original beach’s morphodynamic equilibrium. With the aid of storm events, soil cliffs composed of loose sediment on the backshore were sacrificed to achieve a new equilibrium, resulting in an extremely significant retreat parallel to the coast on the west side of the study area, which reflects the combined effect of human and natural processes. This study provides a concrete example of the rapid response of shorelines to artificial sand mining activities, and the associated finding is a stark warning about the cautious development and utilization of coastal zones and the strict regulation of human activities.

The persistence and habitability of coral reef islands in future extreme oceanographic conditions has received increasing attention in the recent decade, concerning that the sea level rise (SLR) and more frequent and intense storms in the context of global climate change are expected to destabilize those islands. Here, we conduct a set of wave-flume laboratory experiments focusing on the morphodynamic change of reef islands to varying ocean forcing conditions (wave height and SLR). Subsequently, a phase-resolving XBeach numerical model is adopted to simulate the monochromatic wave process and its associated sediment dynamics. The adopted model is also firstly validated by laboratory experimental results as reported in this study. It is then used to examine the impacts of island morphological factors (island width, island height, island location and island side slope) on the island migration. The combined laboratory/physical and numerical experiment outputs suggest that reef islands can accrete vertically in response to the sea level rise and the increased storminess.

Fences have been widely used in coastal protection engineering for their low cost, simple deployment, and easy integration with ecosystems. The effects of fence porosity and height on dune development have been investigated while not much attention has been paid to the effects of fence opening configurations, such as opening size and geometry, and porosity distributions. In this study, we deployed eight fences with same height and similar porosity, but different opening configurations on a sandy beach in Pingtan, Fujian Province. Results indicate that there is a similar two-dune-one-trough pattern for all fences at the beginning of dune development, and opening size, orientation, and geometry, and porosity distribution control the leeward dune peak locations. Fences with small openings and non-uniform porosity have high trapping efficiency, and upper denser porosity may be the optimal design as these fences have the highest trapping efficiency and capacity. The conclusions from this study can provide guidance on practical fence design.

As one of the main areas of tropical storm action in the northwestern Pacific Ocean, South China experiences several typhoons each year, and coastal erosion is a problem, making the area a natural testing ground for studying the dynamic geomorphological processes and storm response of promontory-straight coasts. This study is based on three years of topographic data and remote sensing imagery of Gulei Beach and uses topographic profile morphology, single width erosion-accretion and mean change, combined with the Coastsat model to quantify the seasonal and interannual variability and storm response of the beach and to explain the evolution of shoreline change and beach dynamics geomorphology in the last decade. Gulei Beach has been in a state of overall erosion and local accretion for a long time, with relatively obvious cyclical changes; seasonal changes are also obvious, which are mainly characterized by summer accretion and winter erosion, with accretion at the top of the bay and accretion and erosion on the north and south sides of the bay corner, respectively; the seasonal erosion-accretion volume of the beach profile ranges from −80 m³/m to 95.52 m³/m, and the interannual erosion-accretion volume ranges from −69.09 m³/m to 87.31 m³/m. The response of beaches to typhoons with different paths varies greatly depending on the length, slope, orientation and scale of beach development. The large and gently developing Futou beach is less responsive to storms, while the less developed headlands in the southern Gulei Peninsula are more susceptible to disturbance by external factors and respond more strongly to typhoons. Storm distance is more influential than storm intensity. Under the influence of human activities, obvious erosion hotspots develop during normal weather, but storm processes produce redistribution of beach material patterns, and erosion hotspots disappear after storms. The results of this study enrich the theory of beach dynamics geomorphology and provide technical support for disaster prevention and mitigation, as well as ecological restoration of coastal zones.

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.

Extreme storm events in coastal zones play significant roles in shaping the morphology of boulder beaches. However, boulder displacement and the geomorphological evolution of boulder beaches driven by different extreme storm events, especially typhoon events, remain poorly understood. Thus, boulder displacement and the geomorphic response on a boulder beach in Fujian, southeastern China, were explored before, during and after a cold wave event (Dec. 1–7, 2020) and before and after Typhoon In-Fa (Jul. 19–27, 2021), a large tropical storm. This was achieved by tracking 42 tagged boulders distributed in the intertidal and supratidal zones using Radio Frequency Identification (RFID) and topographic surveys using real-time kinematic techniques, respectively. The results showed obvious disparities in boulder displacement in different geomorphic zones due to cold wave and typhoon events that were mainly characterized by migration magnitude, range, direction, and mode of transport. The typhoon event led to rapid and substantial changes in the overall morphology of the boulder beach, while the cold wave event impacted the intertidal morphology of the boulder beach to only a small extent. The surrounding structure of boulders, beach slope and beach elevation had a combined dominant effect on boulder displacement under the same extreme event. Hydrodynamic factors (effective wave energy fluxes, incident wave direction, storm surge and water level) had dominant effects on boulder displacement during different extreme events. In terms of a single event, the magnitude of the boulder displacement driven by the typhoon was much greater than that driven by the cold wave. However, considering the frequency and duration of cold waves in winter, the impact of multiple consecutive cold waves on the geomorphology of the boulder beach cannot be ignored in this study area. Alternating and repeated interactions between these two processes constitute the complete geomorphic evolution of the boulder beach. This study contributes to improved predictions of the morphodynamic response of boulder beaches to future storms, especially large tropical storms, and facilitates better coastal management.

Coastal erosion on islands is increasing due to sea level rise, frequent extreme events, and anthropogenic activities. However, studies on the multifactorial coastal erosion risk and the vulnerability of islands are limited. In this study, the Coastal Erosion Risk Assessment (CERA) method was applied for the first time to the study area in China to assess the erosion risk on the coast of Hainan Island; to explore the effects of coastal ocean dynamics, sediment movement characteristics, and anthropogenic construction; and to discuss the suitability of the method and countermeasures for coastal protection. The results show that the coast of Hainan Island shows high sensitivity, high value, low exposure, and moderate erosion. The whole island showed high vulnerability but low erosion risk, with the eastern region being more affected by erosion, particularly the eastern side of Wulong Port and Yalin Bay in Wenchang, and the shore section of Yalong Bay in Sanya, having a very high risk of coastal erosion. In addition, Monte Carlo simulation was used to check the applicability of the CERA method, and it was found that the rate of shoreline change, population density, and number of storms significantly contributed to coastal erosion, but only the short-term effects of sea level rise were considered. The effects of sea level rise and sediment grain size were primarily analyzed as influencing factors. The effects of sea level rise continue to strengthen, with coastal retreat expected to be greater than 2 m by the mid-21st century. Moreover, Hainan Island is primarily composed of the fine and medium sand types, which have little resistance to coastal erosion. Currently, the impact of sediment grain size is rarely considered in coastal erosion risk assessment studies. However, it can be incorporated into the indicator system in the future, and the spatial variation of indicators can be fully considered to strengthen the refinement study.

Outbreaks of Ulva prolifera have continued in the South Yellow Sea of China (SYS) since 2007, becoming a serious marine ecological disaster. Large amounts of U. prolifera drift to the coast of the Shandong Peninsula to dissipate under the action of southeast monsoons and ocean surface currents. This causes serious harm to the ecological environment and economic activities of coastal cities. To investigate the impact of U. prolifera dissipation, this study extracted the spatiotemporal distribution of U. prolifera in the SYS from 2012 to 2020 based on the Google Earth Engine. The outbreak cycle of U. prolifera was determined by fitting analysis of outbreak time and coverage area through MATLAB. This study also looked at the effect of U. prolifera dissipation on water quality through field monitoring data. The results showed that the growth curve of the U. prolifera has a significant Gaussian distribution. The U. prolifera dissipates in Haiyang, China, in July and August every year and affects the offshore environment. Water quality parameters of seawater at different depths had significant differences after the U. prolifera dissipation. Changes in pH, chemical oxygen demand, nitrite nitrogen, nitrate nitrogen, ammonia nitrogen, chlorophyll a, total phosphorus, and suspended solids were more significant in surface seawater than in deeper water. Changes in the concentrations of dissolved oxygen and total nitrogen were more significant in the deep seawater (1.63 and 1.1 times higher than those in the surface seawater, respectively). The dissipation of U. prolifera releases a large amount of carbon and nitrogen into the seawater, which provides rich nutrients for phytoplankton and may cause secondary disasters such as red tide. These findings are useful for further understanding the rules of U. prolifera dissipation, as well as preventing and controlling green tide disasters.

Accurately building the relationship between the oceanographic environment and the distribution of neon flying squid (Ommastrephes bartramii) is very important to understand the potential habitat pattern of O. bartramii. However, when building the prediction model of O. bartramii with traditional oceanographic variables (e.g., chlorophyll a concentration (Chl a) and sea surface temperature (SST)) from space-borne observations, part of the important spectrum characteristics of the oceanic surface could be masked by using the satellite data products directly. In this study, the neglected remote sensing information (i.e., spectral remote sensing reflectance (Rrs) and brightness temperature (BT)) is firstly incorporated to build the prediction model of catch per unit effort (CPUE) of O. bartramii from July to December during 2014–2018 in the Northwest Pacific Ocean. Results show that both the conventional oceanographic variables and the neglected remote sensing data are suitable for building the prediction model, whereas the overall root mean square error (RMSE) of the predicted CPUE of O. bartramii with the former is typically less accurate than that with the latter. Hence, the Rrs and BT could be a more suitable data source than the Chl a and SST to predict the distribution of O. bartramii, highlighting that the potential value of the neglected variables in understanding the habitat suitability of O. bartramii.