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Purpose To explore the associations between myopia defocus dosage (MDD), aberration coefficients (primary spherical aberration and coma), and axial elongation in children undergoing orthokeratology (ortho-k) with back optic zone diameters (BOZD) of 5 mm and 6 mm over 2 years. Methods Data from 80 participants from two ortho-k studies were analyzed: 22 and 58 children wore lenses with 5-mm and 6-mm BOZD, respectively. Four MDD metrics were calculated from corneal topography data over a 5-mm pupil for the 1-month and 24-month visits: the circumferential, flat, steep, and volumetric MDD. Corneal primary spherical aberration and comatic aberrations were also extracted from topography data over a 5-mm pupil. Linear mixed modelling was performed to explore the associations between the MDD, corneal aberrations, and axial elongation over 2 years, while controlling for confounding factors (e.g., baseline age and sex). Results Participants in the 5-mm BOZD group displayed less axial elongation than the 6-mm BOZD group over 2 years (0.15 ± 0.21 mm vs. 0.35 ± 0.21 mm, P  < 0.001). A greater volumetric MDD was observed in the 5-mm BOZD group compared with the 6-mm BOZD group at the 1- and 24-month visits (both P  < 0.001). No significant differences were observed between the two groups for the other MDD metrics or corneal aberration coefficients (all P  > 0.05). Less axial elongation was associated with a greater volumetric MDD at the 1- and 24-month visits (both β = –0.01, P  < 0.001 and P  = 0.001), but not with any other MDD metrics or corneal aberrations (all P  > 0.05). Conclusions The volumetric MDD over a 5-mm pupil after 1 month of ortho-k lens wear was associated with axial elongation after 24 months, and may be a useful predictor of future axial elongation in children undergoing ortho-k.

For illustrating estuarine and coastal morphology, UAV has proved its effectiveness in providing accurate and diverse information, but unfortunately, no such application have been undertaken for Nakdong River Estuary for ecosystem-based coastal mapping. In this study an attempt has been made to coastal mapping of Jinu-do in Nakdong River Estuary, and to identify beach volume change and vegetation area migration caused by wave and current from 2017 to 2018 with UAV. Unmanned aerial vehicle used for mapping was M600 hexa-copter drone (DJI, china). To create UAV point clouds a standard digital camera can provide imagery with Sony A7 mirror-less camera. Total 34 Ground Control Points (GCPs) accurately surveyed with a RTK-VRS, network use real-time kinematic solutions to provide high-accuracy. Stereo-matching using Agisoft PhotoScan obtained DEM. Using GCPS the vertical accuracy of the DSMs were found to be 5 cm or better. Using the PhotoScan, the area of Jinu-do orthophotos were calculated and the area of vegetation calculated using QGIS. As a result, the vegetation area was increased about 5 % more than the topography. This study of coastal mapping at Jinu-do demonstrate that the integration of UAV techniques and photogrammetric software and analysis tools can provide new concepts into the estuarine.

The gravitational instability of hot material deposited during eruptive activity can lead to the formation of glowing avalanches, commonly known as deposit-derived pyroclastic density currents (PDCs). These currents can travel hundreds of metres to several kilometres from the source at exceptionally high temperatures, posing a catastrophic hazard to areas surrounding steep-slope volcanoes. The occurrence of deposit-derived PDCs is often associated with crater rim failure, which can be triggered by various factors such as magma thrust from dike injection, magma fingering, bulging or less commonly, powerful explosions. Here, the in-depth study of data from the multi-parametric monitoring network operating on Stromboli (Italy), including video surveillance, seismicity and ground deformation data, complemented by remote topographic sensing data, has facilitated the understanding of the events leading to the crater rim collapse on 9 October and 4 December 2022. The failures resulted in the remobilisation of 6.4 ± 1.0 × 10 3 m 3 and 88.9 ± 26.7 × 10 3 m 3 of material for the 9 October and the 4 December 2022, respectively, which propagated as PDCs along the NW side of the volcano and reached the sea in a few tens of seconds. These events were characterised by a preparatory phase marked by an increase in magmatic pressure in the preceding weeks, which correlated with an increase in the displacement rate of the volcano’s summit. There was also an escalation in explosive degassing, evidenced by spattering accompanied by seismic tremors in the hours before the collapse. These events have been interpreted as an initial increase in magma vesicularity, followed by the release of gas once percolation threshold was reached. The degassing process induced densification of the magma, resulting in increased thrust on the conduit walls due to increased magmastatic pressure. This phase coincided with crater rim collapse, often followed or accompanied by the onset of lava overflow phases. A mechanism similar to the one proposed may shed light on similar phenomena observed at other volcanoes. The analysis performed in this study highlights the need for a multi-parametric and multi-platform approach to fully understand such complex phenomena. By integrating different data sources, including seismic, deformation and remote sensing data, it is possible to identify the phenomena associated with the different phases leading to crater rim collapse and the subsequent development of deposit-derived PDCs.

On September 14, 2019, a reactivated landslide with a volume of 1.3 × 107 m3 occurred in Changhe Town, Tongwei County, Gansu Province, China. As a result, a provincial highway, brickfield, and bridge were destroyed. Based on field investigation, interferometric synthetic aperture radar (InSAR) as well as unmanned aerial vehicle (UAV) photogrammetry, high-resolution remote sensing imagery, and digital elevation model, we addressed the surface displacement, travel distance, topographic changes, and causative factors of the Changhe landslide. The result shows the combination of ascending and descending orbit datasets can not only be used to monitor the landslide surface displacement but also to verify the deformation results. This landslide is a typical retrogressive landslide where large pre-failure deformation exists in the lower part of the landslide body. We detected the surface travel distance of the landslide and found spatial differences exist in the surface travel distance of the landslide. The deposit volume slightly exceeds erosion volume due to decompaction during the landslide. The frequency distribution of the basic topographic factors before and after the landslide is different, which indicates that the landslide event significantly changed the local topography and geomorphology. This study provides an insight into the spatiotemporal evolution of the landslide and has practical importance for early warning of landslides and risk mitigation.

Understanding long-term changes in topography and topsoil grain composition is crucial for the management of agricultural landscapes, especially in areas prone to wind erosion. This study investigates long-term changes in topography and topsoil grain composition within an agricultural landscape in south-western Slovakia. To analyse topographic changes over time, we used high-precision positioning measurements and airborne laser scanning to create digital terrain models (DTM) for the years 2011, 2017 and 2020. To assess changes in soil grain composition, we performed grain size analyses on soil samples collected during three different periods: M1 (1961–1970), M2 (2009–2015) and M3 (2015–2016). Changes in soil texture were evaluated to understand the impact of wind erosion on soil composition. The influence of windbreaks was also analysed by comparing the accumulation and deflation processes. The results showed significant changes in both topography and soil texture over the study period. The DTMs showed marked differences in the accumulation and deflation processes, highlighting areas affected by wind erosion. Comparisons of soil samples showed a shift in dominant soil types from loam and clay loam to silty loam, highlighting the effects of wind erosion. Analysis revealed a decrease in clay and silt content and an increase in sand content, indicating wind-induced soil degradation. The presence of windbreaks played a crucial role in reducing soil erosion by reducing wind speed, promoting soil accumulation and stabilising the landscape up to 80 m windward and 20 m leeward. The study highlights the complex interplay of climate and wind factors in shaping topography and soil properties and emphasises the protective role of windbreaks in agricultural landscapes over time. Our results show that wind erosion significantly alters soil texture, which can affect agricultural productivity. However, windbreaks have proven to be an effective measure in reducing soil erosion and maintaining soil quality.

In recent years, the position of the Yellow River Estuary (YRE) entrance has changed frequently, and human activities such as land reclamation have contributed to the transformation of the deltaic topography. These combined factors have resulted in altered hydrodynamics and tidal shear fronts (TSFs) in the surrounding sea area. However, there are few studies on the characteristics of the TSFs before and after diversion, so this paper establishes a hydrodynamic model based on the Finite Volume Coastal Ocean Model (FVCOM) for the years 2005, 2014, and 2020 and analyzes the characteristics of the changes in the tidal currents and the TSFs before and after diversion and the long-term evolution trends. The results reveal that the M2 amphidromic point near the YRE shifted eastward by 4.9 km from 2005 to 2014 and migrated southeastward by 6.8 km between 2014 and 2020. Additionally, significant changes were observed in the maximum and residual currents within the active mouth (AM), the old Qing 8 (Q8) channel, the old QingShuiGou (QSG) channel, and the southeastern region. Notably, the residual currents exhibit vertical fronts with substantial current velocity differences across the slopes. After the diversion of the YRE, the northern TSFs disappeared. The TSFs in the AM gradually shifted landward, while the TSFs in the southeastern region shifted offshore. In the vertical direction, the frontal centerlines of the TSFs gradually moved offshore from top to bottom. The intensity of the TSFs at the same latitude was positively correlated with the offshore distance. Generally, steeper slopes were associated with larger bottom stress gradients, which in turn corresponded to stronger TSFs.

Debris flows moving along steep creeks can bring serious damage to downstream regions. Most debris-flow experiments to date have been conducted in controlled, indoor settings using flumes with straight channels and constant cross-sectional areas. Such experiments cannot accurately verify the dynamic behavior of real debris flows because of their relatively small size, and they often fail to account for complex topographic shapes or the channel bed erosion that occurs during debris flows. With this in mind, a real-scale experiment was conducted in a natural outdoor gully that could credibly represent a true hazard site in South Korea. Video cameras, a load cell, pore pressure transducers, and an ultrasonic sensor were installed at the test site to capture the dynamic behavior of the debris flow. Topographic changes were analyzed before and after the experiment using terrestrial LiDAR. The results showed that the pore-fluid pressure and normal stress for the soil bed were closely related to the flow depth. In addition, the change of the frontal velocity of the debris flow decreased with the decreasing slope angle along the channel but the effect of the width of the channel on the velocity was negligible, although the velocity temporarily increased in the exposed bedrock zone despite a decrease in the slope angle. Furthermore, the erosion depth increased as the frontal velocity increased, with up to four times more erosion in the initiation zone than in the transportation zone.

Digital Elevation Model (DEM) errors tend to be spatially correlated, inevitably affecting DEM-based topographic change detection. Traditional topographic change detection methods often ignore the spatial distribution of the DEM error. This paper aims to develop a workflow that considers the spatial autocorrelation of the error in topographic change detection. Firstly, the DEM of Difference (DoD) is obtained from two-period DEMs, and the Monte Carlo method is employed to evaluate the Spatially Distributed Errors (SDE) in DEMs. Secondly, DoD errors are calculated by propagation based on spatially distributed DEM errors. At the same time, its spatial distribution is quantified using the semi-variance function. Finally, topographic changes (erosion, deposition, and net changes) are calculated based on the spatial distribution analysis and significance detection. The results in two small catchments indicate that DEM errors are spatially correlated, increasing the volume calculation errors. However, using Standard Deviation of Errors (SDE) instead of Root Mean Square Error (RMSE) can effectively reduce the sensitivity of the detection results in the significance threshold. When the significance threshold increases from 68% to 95%, the observations loss using the spatially distributed error is 4.67% −6.92% lower than that using the RMSE. The level of detection has little impact on the net topographic change and significantly influences gross erosion and deposition. In particular, the use of level of detection can effectively reduce the misclassification of erosion or deposition in stable topography areas. The proposed method can be effectively utilized in various applications like surface deformation monitoring, erosion monitoring, and sediment transport assessment.

Because many coastal developments have been continuously occurred in the Yellow and the East China Sea, it is necessary to analyze the effect of persistent topographic change. This study simulated the tidal change in response to stepwise tidal flat reclamation in East China and the Yellow Sea using the MOdelo HIDrodinâmico (MOHID) ocean model. Based on previous studies and historical coastal information maps, we conducted several numerical experiments with reliable coastal topography changes around two areas (Jiangsu Shoalwater and Gyeonggi Bay) from 1990 to 1994 when the most active development took place. The results show that, unlike other components (S2, O1, and K1), the simulated amplitude of the M2 constituent significantly increased with the disappearance of the tidal flat in the Yellow Sea. At the same time, it decreased in the East China Sea. These results are consistent with the quantile regression analysis using observational data. We also found an accumulating effect of tidal energy flux when the reclamation continued, which does not appear in the previous studies. These results indicate persistent man-made tidal flat reclamation in a specific area can cause more remarkable regional tidal changes through tidal energy redistribution and modification.

Lee, C.K. and Yun, K., 2023. Time-series forecasting of topographical changes on Byunsan Beach in South Korea. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 255-259. Charlotte (North Carolina), ISSN 0749-0208. Tides continuously affect the intertidal zone, erosion and deposition are caused by cataclysmic events such as hurricanes and typhoons in coastal areas, leading to a variety of issues. In particular, recent land reclamation, the creation of man-made islands, land expansion, and the construction of coastal power plants as a result of various forms of coastal development may distort the sedimentary environment to attain a new equilibrium state. As a result, there may be a shift in the external forcing on the coastal environment, which may restrict the supply of soil or alter its movement. The Saemangeum reclamation project is a large-scale project that involves building a 33.9 Km embankment from Buan to Bieung-do, Kunsan, and reclaiming the nearby land of 291 km2. This has been ongoing since the start of the seawall construction in the central coastal area of the west coast of the Korean Peninsula in 1991. This study observed and predicted the long-term topographical changes at Byeonsan Beach in Buan-gun, Jeollabuk-do, using aerial photography and drone-based Light Detection and Ranging (LiDAR) data collected over a period of nine years. This was accomplished using the Digital Elevation Models (DEMs) difference approach based on raster operations using the DEM derived from the source data to estimate the change in elevation and volume for each period. The error propagation equation was also used to calculate the probability-based volume change for the inherent error of each data source. As a result, the Region of Interest (ROI) experienced 18,847 m3 depositions between 2014 and 2022, with the area affected comprising 92.3% of the ROI.