Geomorphology最新文献

Nowadays, the detection and automatic identification of the three-dimensional structure of sinkholes is extremely lacking, which has resulted in significant gaps in sinkholes mapping, soil erosion estimation and morphological studies. In this study, we discovered 249 sinkholes on a river terrace (about 2050 m long and 100 m wide) in a small watershed of Chinese Loess Plateau. Subsequently, we used the unmanned aircraft systems (UAS) and handheld laser scanner (HLS) to investigate these loess sinkholes in detail. We introduced the PointNet ++ deep learning model to train the point cloud dataset for 50 epochs and then selected the best model. In order to evaluate the identification accuracy and transferability of the model, we input point clouds of the unknown prediction area into the trained model to predict the sinkhole point clouds. The trained model exhibits excellent transferability and can effectively identify the sinkhole point clouds in the predicted area (OA = 0.935, IoU (Sinkhole) = 0.662, mIoU = 0.794, AUC = 0.966, Recognition rate = 82.46 %), and even sinkholes with complex connected structures can be accurately identified. This study provides a new perspective for future large-area LiDAR surveys, mapping, and assessment of sinkholes.

Changes to the morphology of the upper Yellow River (UYR) had various impacts on the surrounding ecology and society, as well as the entire basin. However, low-spatial-resolution imagery (e.g., MODIS, AVHRR) cannot capture sufficient spatial details for monitoring complex water bodies, while high-spatial-resolution imagery (e.g., SPOT, Quickbird, Ikonos) lacks spatial coverage and the revisit frequency necessary for large-scale water body monitoring. To address these limitations, this study utilized the Google Earth Engine (GEE) and ArcGIS spatial analysis tools, applied pan-sharpening to downscale Landsat imagery of the study area from 1999 to 2023, performed river extraction, and calculated the spatiotemporal changes in river morphology in the UYR using river morphological parameters (i.e. area, channel width, centerline length, sinuosity index, lateral migration rate, channel stability). The Automated Water Extraction Index (AWEI_sh) effectively characterized the study area, and pan-sharpening technology improved the extraction accuracy of small water bodies. Finally, the overall accuracy and Kappa coefficient were 0.993 and 0.985, respectively. Over the past 25 years, the area and average width of the entire reach of the UYR changed significantly, with the maximum value being 1.3 times the minimum value, whereas the centerline length and sinuosity index showed no apparent changes, and the lateral migration rate varied minimally, with the average annual movement ranging from 4.67 m to 10.18 m. In typical river segments without human activity, although single-channel reaches exhibited stronger stability than multi-channel reaches, natural factors (i.e. annual precipitation, annual runoff, annual sediment discharge) had a noticeable impact on the morphology of both single-channel and multi-channel reaches. Large-scale cascade hydropower development in the UYR has significantly impacted river morphology over a short period. Meanwhile, in river sections unaffected by human activities, the changes occurred gradually. This study provides support for better understanding complex river morphologies at large regional and long-term scales and a scientific basis for water resource management and sustainable development in the UYR.

The coupling of sediment sources varies in terms of efficiency and availability based on the frequency and intensity patterns of rainfall events over time. It is commonly assumed that reaches with steeper gradients have higher longitudinal connectivity, while lower gradient reaches have lower longitudinal connectivity. However, considering that the longitudinal connectivity of channels is not always perfectly established, this conception regarding channel gradient may not always hold true. In forested regions, elements such as large wood can be the main agents of this disconnectivity. Thus, this study investigates the effects of large wood on sediment flux, flow characteristics and channel morphology in the context of the Atlantic Forest Biome in a low-order stream in the southern Brazilian plateau. To achieve this, measurements of hydrological variables, characterization of sediments, and channel morphology were conducted. Hydraulic and morphological variables were estimated to define hydraulic signatures for each river section. The influences of large wood barriers in the study section were highlighted through an analysis of hydraulic characteristics at different cross-sections and the assessment of morphological variables. The investigation revealed a tendency for a reduction in velocity of approximately 90 % in low-discharge conditions in sections where large wood barriers were present. In the case of high-magnitude events, the velocity reduction was considerably lower. Additionally, it was found that each large wood deposit presented uniqueness, and the structural characteristics of each reflected the potential for system disconnectivity. Finally, it was observed that both barriers have the capacity to store sediments, leading to the constriction of the cross-section due to the formation of sediment bars, although surveys revealed that fine sediments were poorly retained in both barriers.

In 2021, La Palma's southern volcanic complex Cumbre Vieja erupted for its longest period in historic times. Although the geological record shows no evidence for a collapse of Cumbre Vieja, ground deformation studies and field observations suggest that its western flank is moving seawards, following the direction of previous collapses of the island. To better estimate the hazard of a potential flank collapse of Cumbre Vieja, it is important to identify the lateral extent and depth of the mobile sector. Here, we analyse the volcano-tectonic deformation along Cumbre Vieja's western flank, based on geomorphological analysis of combined topographic and new ship-born bathymetric data as well as the analysis of shallow seismicity records associated with the 2021 eruption. In our interpretation, the shoreline-crossing Puerto Naos Ridge results from tectonic uplift accompanying transpressional deformation along the northern boundary of Cumbre Vieja's moving flank, therefore decoupling a stable sector in the north from the mobile sector farther south. The proposed moving sector is consistent in scale with previous ground deformation studies and documented flank collapses of structurally similar volcanoes. We present a workflow for semi-automatically detecting boundaries of unstable volcanic flanks based on morphological changes captured in digital elevation data. The method correctly delineated the known boundaries of the unstable flanks of Mt. Etna and Kilauea volcanoes. The ability to constrain potential boundaries of unstable volcanic flanks should inform the planning of future geophysical and geodetic campaigns aiming to identify precursory signals of potential flank failures.

This study presents a novel method for the accurate delineation of dolines in karst areas. The method is based on the use of hydrological tools and sky-view Factor in ArcGIS Pro and was implemented using a digital elevation model with a resolution of 1 m in four study areas in Slovenia. We manually delineated dolines at four test areas and compared them with the results of the new method, as well as the results of the most commonly used method of hydrological filling and the results of U-Net segmentation. We calculated the average deviation of the perimeter and the differences in the basic morphometric properties. The hydrological filling method cannot be accepted as a suitable method for doline delineation and should only be used for doline identification. The method based on the U-Net segmentation performed better, but the results contain landforms that are not enclosed depressions and therefore cannot be considered as dolines. The new method utilizes the advantages of hydrological filling and at the same time improves the doline delineation. We conclude that the presented method is the most suitable for automatic doline identification and delineation among the automatic methods discussed in this paper. This study further quantifies the enhancements achieved with the new method, highlighting the specific improvements in perimeter accuracy and the reliability of morphometric measurements.

Alluvial plains are highly vulnerable to floods and ground disasters. Recent rapid urbanization and climate change have heightened disaster risks in urban areas. Geomorphological maps, crucial for estimating disaster risks, delineate landform boundaries based on patterns of concave breaks of slope and micro-landforms. However, enhancing the accuracy of such maps requires data extraction methods capable of capturing these features with greater precision. Traditional topographic measurements derived from adjacent elevation points in airborne light detection and ranging (LiDAR) digital terrain models (DTMs) fail to accurately represent slope variations on low ground surfaces due to the inclusion of numerous noise-like artificial terrain features. Consequently, analyzing natural terrain becomes challenging. To address this issue, our study devised a method to automatically identify and eliminate noise-like artificial terrain from LiDAR DTMs. We achieved this by removing major artificial terrain features from land-use vector data, creating an edge-preserving smooth DTM, and selectively removing and interpolating only those areas where were large differences between the smooth DTM and the LiDAR DTM. This method minimizes the interpolation of artificial terrain and quotes the LiDAR DTM for other areas, thereby minimizing the data quality loss. It is possible to identify and demarcate topographic boundaries in plains with a longitudinal gradient of approximately 1% or less at a high resolution, which can be used to investigate the relationship between flood and ground characteristics and landform volume in the plains. This method can be easily processed using only QGIS and free open data. This approach enhances the precision of disaster risk estimation and facilitates more effective urban planning in vulnerable areas.

Composite volcanoes are dynamic landforms that require comprehensive morphological analysis to understand their formation, degradation and associated controlling processes. Establishing Digital Elevation Model (DEM) source, spatial resolution and edifice delineation method are the first essential steps to quantify volcano morphometry. The delineation and quantification of the morphology is a complex endeavor as a volcano’s edifice is the result of overlapping eruptive products, intrusions, and degradation by a range of erosional processes and thus needs to be assessed in different volcanic environments.

In this study, sixteen volcanoes from four volcanic arcs are used to quantify and compare twelve different geometric and drainage parameters. We first perform an edifice delineation analysis where we compare the similarity of volcano boundaries drawn by seven volcano geomorphology experts. Afterwards, a second set of boundaries is drawn based on a slope threshold to guide the delineation between boundaries, which proves beneficial in enhancing consistency between expert-driven manual delineation. For the same volcanoes, we also extract automatic delineation algorithm-derived NETVOLC boundaries to complement the comparison. Afterwards, a comparative analysis of morphologic parameters is conducted for four free and globally available 30-m-resolution DEMs: ALOS (AW3D30), SRTM (SRTMGL1), ASTER (GDEM 003) and TanDEM-X. The impact of resolution is also assessed using the 12 m and 30 m grid TanDEM-X DEMs on the same parameters.

Our results show that precise and consistent delineation of the volcanic edifice boundaries, and to a lesser degree the resolution of the DEM, holds greater significance than the specific DEM type used to extract morphometric parameters. The slope cost function of NETVOLC shows the lowest deviation from the expert-defined boundaries. The metrics most sensitive to the defined boundary are volumes and basin width, and the parameters that significantly differ between 12 m and 30 m TanDEM-X are irregularity index, eroded volume, slope and drainage density. Our analysis thus emphasizes the necessity of meticulous consideration when selecting the DEM, and more importantly, adopting a consistent approach to delineating edifice boundaries in comparative morphometric analyses of volcanoes.

In the present study, circular and octagonal collars together with sacrificial piles are tested for their efficiency as protection devices against local scour in the non-uniform sand bed of geometric standard deviation 2.29 and median grain size 1.18 mm. To examine the effect of width and elevation on scour depth, experiments are conducted with circular and octagonal collars of widths $1.5b$ and $2b$ placed on the bed and $0.25y$ above the bed where $b$ is the pier diameter and $y$ is the flow depth. The octagonal and circular collars of width 2b placed in flush with the bed achieved maximum scour reductions of 78.33 % and 75 %, respectively. The efficiency of the collars decreased when their width is reduced and when they are placed above the bed. Among the sacrificial piles in transverse and staggered arrangements, a maximum scour reduction of 55 % is observed when the piles are placed transverse to the flow at a distance of 2b from the pier center. The efficiency of the sacrificial piles decreased when they are moved away from the pier center. A maximum scour reduction of 86.67 % is seen for the combination of the octagonal collar of width $2b$ on the bed and piles in the transverse arrangement. A new empirical equation is proposed for temporal and equilibrium scour for collar around the pier, including the armor effects. The sensitivity analysis revealed that $b_c/b$ is the most sensitive parameter followed by $H/y$, $k_s$ and $T_c$ where where $b_c$ is the collar width, $H$ is the location of the collar from the water surface, $k_s$ is the shape factor and $T_c$ is dimensionless time.

Atmospheric warming and circulation reorganization at the end of the last ice age represent the most important climate change of the last 100,000 years and provide an opportunity to uncover how the southern subtropics cryosphere responded to strong changes in the global climate system. Extensive mapping and chronologic records on cryogenic landforms to better understand the association and interactions between glaciers and viscous creep of ice-rich permafrost landforms (rock glaciers) are widely missing in the region. In this paper, we reconstruct the geomorphic imprint of the Last Glacial Maximum (LGM) and the Termination I in the high Andes of the Río Limarí Basin (30–31°S) in the subtropical semiarid Andes of Chile. 74 new ¹⁰Be surface exposure dating ages constrain the timing of glaciation, deglaciation, and glacial to periglacial transition. Glacial advances occurred first by 41.2 ± 0.6 – 35.0 ± 0.5 ka during Marine Isotope Stage 3, but probably earlier also; then, a second advance occurred during the global LGM between 24.2 ± 0.4 and 18.6 ± 0.2 ka. Deglaciation by 17.6 ± 0.2 ka left extensive hummocky moraines on the main valleys. Characteristic patterns of furrows and ridges typical of rock glaciers and solifluction superimposed on the LGM hummocky moraine indicate ice-rich permafrost in glacial deposits likely between 15.5 ± 0.3 and 13.6 ± 0.3 ka. We propose that moraines deposited by LGM debris-covered glaciers served as a niche for strong seasonal frost and permafrost creep, which substantially modified the original landforms. Our results contribute to a better understanding of major transformations in an ice-rich high mountain area of the southern hemisphere where the interplay of temperature and precipitation changes drove glacial to periglacial transitions.

The forcing mechanism behind river incision and terrace formation is one of hot topics in the study of fluvial geomorphology. This work focused on the late Quaternary alluvial sequence in the south piedmont of the Chinese Altay Shan in the arid inland of Asia. In order to reveal the mechanism controlling the development of late Quaternary fluvial features along the mountain front, we conducted detailed fluvial geomorphological investigations on eight rivers, including geomorphic mapping, optically stimulated luminescence (OSL) dating, and differential global position system (dGPS) surveying. By utilizing the Monte Carlo simulation with terrace data, the late Quaternary rates of river incision along the south piedmont of the Chinese Altay Shan were determined. The results show that (1) the terraces developed by the piedmont rivers are not more than four levels and the depth of river incision in the piedmont is only dozens of meters, with deeper valleys displayed by the western piedmont rivers; (2) terrace alluviums along the mountain front were accumulated during glacial stages, and the subsequent incision occurred during interglacial stages; (3) the rate of river incision was accelerated during the Holocene, when the regional climate was characterized by progressively increasing wetness. When combining with the regional tectonic setting, we propose that the climate could have played the key role in driving the alluvial accumulation and the subsequent incision in the south piedmont of the Chinese Altay Shan during the late Quaternary. Together with the similar observations from the northeastern margin of the Tibetan Plateau and the Tian Shan, we further propose that climatically-driven fluvial geomorphological development could be a common phenomenon during the late Quaternary in the arid interior of Asia.