Explore the vast range of titles available.

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.

As China’s Loess Plateau has lately witnessed increasingly extreme precipitation events, it is important to analyze the impact of extreme precipitation and identify the conditions for the occurrence of geological disasters. Field surveys can provide detailed geological information in this regard but are time consuming and labor intensive. In this paper, we provide a case study on the Gutun catchment of Yan’an, which was affected by prolonged heavy rainfall in July 2013. We used Digital Elevation Model (DEM) data obtained by processing ZY-03 stereo-pair images before and after the rainy season, including the period of prolonged heavy rainfall mentioned above, to analyze the topographical changes triggered by the rainfall. The results showed the following: (1) The rainy season reduced the elevation of the catchment by about 1.7 cm. The major change in its elevation ranged from −0.5 to 0 m, accounting for 38.41% of the overall area of change and dominating above 70 m of slope height. (2) The rainy season increased the average inclination of the slopes in the area from 28.81° to 28.95°, while the range of their peak inclination was mainly distributed in the range of 24°–36°. (3) Sunny and half-sunny slopes exhibited a greater loss in elevation, while shady and half-shady slopes exhibited an increase in elevation. More drastic topographical changes were observed in the shady and half-shady slopes. (4) The morphology of the area that had undergone a reduction in elevation was characterized by concave slopes, while convex slopes abounded in the area with increased elevation. (5) The sunny or shady properties of the slope aspect constituted the key factor influencing the topographical changes, followed by the height, inclination, and shape of the slopes. The work here can provide guidance for measures related to disaster prevention and mitigation.

The monitoring of beach topographical changes and recovery processes under typhoon storm influence has primarily relied on traditional techniques that lack high spatial resolution. Therefore, we used an unmanned aerial vehicle light detection and ranging (UAV LiDAR) system to obtain the four time periods of topographic data from Tantou Beach, a sandy beach in Xiangshan County, Zhejiang Province, China, to explore beach topography and geomorphology in response to typhoon events. The UAV LiDAR data in four survey periods showed an overall vertical accuracy of approximately 5 cm. Based on the evaluated four time periods of the UAV LiDAR data, we created four corresponding DEMs for the beach. We calculated the DEM of difference (Dod), which showed that the erosion and siltation on Tantou Beach over different temporal scales had a significant alongshore zonal feature with a broad change range. The tidal level significantly impacted beach erosion and siltation changes. However, the storm surge did not affect the beach area above the spring high-tide level. After storms, siltation occurred above the spring high-tide zone. This study reveals the advantage of UAV LiDAR in monitoring beach changes and provides novel insights into the impacts of typhoon storms on coastal topographic and geomorphological change and recovery processes.

Background As one of the main components of land-use change, deforestation is considered the greatest threat to global environmental diversity with possible irreversible environmental consequences. Specifically, one example could be the impacts of land-use changes from oak forests into agricultural ecosystems, which may have detrimental impacts on soil mobilization across hillslopes. However, to date, scarce studies are assessing these impacts at different slope positions and soil depths, shedding light on key geomorphological processes. Methods In this research, the Caesium-137 ( 137 Cs) technique was applied to evaluate soil redistribution and soil erosion rates due to the effects of these above-mentioned land-use changes. To achieve this goal, we select a representative area in the Lordegan district, central Iran. 137 Cs depth distribution profiles were established in four different hillslope positions after converting natural oak forests to rainfed farming. In each hillslope, soil samples from three depths (0–10, 10–20, and 20–50 cm) and in four different slope positions (summit, shoulder, backslope, and footslope) were taken in three transects of about 20 m away from each other. The activity of 137 Cs was determined in all the soil samples (72 soil samples) by a gamma spectrometer. In addition, some physicochemical properties and the magnetic susceptibility (MS) of soil samples were measured. Results Erosion rates reached 51.1 t·ha − 1 ·yr − 1 in rainfed farming, whereas in the natural forest, the erosion rate was 9.3 t·ha − 1 ·yr − 1 . Magnetic susceptibility was considerably lower in the cultivated land ( χ hf = 43.5 × 10 − 8  m 3 ·kg − 1 ) than in the natural forest ( χ hf = 55.1 × 10 − 8  m 3 ·kg − 1 ). The lower soil erosion rate in the natural forest land indicated significantly higher MS in all landform positions except at the summit one, compared to that in the rainfed farming land. The shoulder and summit positions were the most erodible hillslope positions in the natural forest and rainfed farming, respectively. Conclusions We concluded that land-use change and hillslope positions played a key role in eroding the surface soils in this area. Moreover, land management can influence soil erosion intensity and may both mitigate and amplify soil loss.

Globally, prioritizing short-term economic gains from mineral extraction has led to a critical dilemma: a planet rich in resources struggles with environmental degradation and a diminishing ability to sustain future generations. Open-pit mining exemplifies this paradox, causing significant environmental damage. In Georgia, this extractive industry presents environmental problems. Despite these known consequences, the long-term impacts of mining activities remain understudied. This study addressed this gap by analyzing the effects of open-pit mining on terrain morphology, and water dynamics in the Kazreti region over a 50-year period (1970–2020) and vegetation health over 35-year period (1987–2022). By integrating water quality assessment, spatial analysis and remote sensing, we revealed the significant human-induced changes to the region’s ecosystem. Spatial analysis results suggested that over 156.7 million cubic meters of bedrock have been fragmented by mining in southern East Georgia, with 125.5 million cubic meters deposited in valleys. Consequently, discernible shifts in the trajectories of water flow were observed based on the hydrological model. Additionally, a comparative analysis of NDVI and EVI values revealed a decline in vegetation health near mining zones, while remote forest areas remained stable. June typically showed healthier vegetation due to cooler temperatures and optimal growing conditions, while August presented lower vegetation health due to increased heat stress. Water quality revealed significant loadings of Cu (58–1855 μg l −1 ), Zn (54–2582 μg l −1 ), Mn (1–2167 μg l −1 ), and Cd (0.1–4.5 μg l −1 ), in local river systems, which are higher than the Georgian official guideline values (Cu - 1000, Zn - 1000, Mn—100, Cd—1 μg l −1 ). This study highlighted the need for a broader long-term monitoring strategy to assess the migration of these contaminants within the food web and the consequent socio-economic impact.

The study area was Anin Beach, where a 1.48-km-long breakwater, consisting of a non-porous caisson, was constructed over 16 months. During this process, significant erosion occurred over a wide area behind the coast, with a maximum reduction in the beach width of 36 m observed in the central part of the coastline. As a countermeasure to prevent erosion, a submerged breakwater was installed that consisted of concrete blocks and had a length of 600 m. Following the implementation of this submerged breakwater, the beach behind it increased in width by 64 m, in proportion to the installation length, while erosion phenomena, such as the loss of coastal roads, were observed at both ends of the structure. In this study, the topographical changes caused by waves and currents were analyzed to identify their causes and establish countermeasures. Additionally, the planned measures, established before structure installation, were closely examined against the actual occurrences observed onsite through a coastline survey.

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.

The remaining alluvial tin reserves around large ex-mining area can be an opportunity to optimize the potential reserves using a small-scale mining system. One of the latest breakthroughs in the mining system for the remaining alluvial tin reserves on land is the borehole mining (BHM) method. However, mining operations using BHM have several environmental impacts especially related to its former holes. This study aims to identify the changes in geometry of the former holes both on the surface and below the surface through direct field observations and measurements using geophysical methods. The study site is in the large ex-mining area of Air Nudur Block in South Bangka Regency, Bangka Belitung Islands Province. The geophysical methods used to identify the changes in the geometry of the BHM holes are GPR (ground penetrating radar) and IP (induced polarization). The GPR method has high resolution subsurface visual capabilities at shallow depths and this method can distinguish between stable and unstable layers. The IP method is used to determine the overburden layer and the condition of the alluvial layer where some of it has become a hole. These two methods will mutually reinforce in interpreting the change in the geometry of the BHM holes. Changes in hole diameter and depth were measured directly in the field within 2 (two) months from the completion of mining operations using the BHM method followed by the periodic topographic measurements using UAV (unmanned aerial vehicle). The results of observations on changes in the elevation of the ground surface around the former BHM hole indicated that the land level subsided by about 1 m. Meanwhile, the results of GPR data processing showed changes in the hole geometry with the hummocky radargram pattern into chaotic. Interpretation of IP data processing shows resistivity values of 250 - 1700 ohm.m and chargeability of 15 - 25 ms in the disturbed alluvial layer around the former BHM holes.