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Alluvial fans are common landforms deposited by streams and/or debris flows. Multiple fans can overlap and connect with each other, developing a bajada. Currently, studies about the evolutionary process of alluvial landscapes and environmental changes in arid areas urgently need clear, detailed and object-based evaluation within bajadas. However, existing methods still struggle to divide these alluvial slopes into individual fans. Accordingly, we proposed a novel method for delineating individual alluvial fans based on free digital elevation models. This method incorporated multi-directional hillshades to accurately extract alluvial slopes, and two flow direction algorithms to support the delineation of individual fans. The method was tested in Death Valley, where a total of 89 individual fans were delineated for morphological analysis. Our result demonstrated high accuracy validated by a Landset-9 L2 satellite image, with an intersection over union (IoU) of 95.51 % for alluvial slopes and a mean IoU of 86.19 % for individual fans, and it also aligned well with the geological map. Additionally, based on the delineated individual fans, we computed morphological features, distinguished the surface differences of both sides and analyzed the feature correlations. Overall, this study accomplished the delineation of individual fans and provided a viable solution for the automated and large-scale mapping of arid alluvial landscapes. The delineated results can act as the foundation for research about the evolutionary process and genetic mechanisms of alluvial fans, and provide opportunities for understanding the tectonic activities, sediment deposition and erosion process and environmental changes in arid regions. • Boundaries of alluvial slopes were accurately identified. • Delineation of individual confined fans within bajadas was achieved. • Individual fans were characterized by diverse morphological features. • Differences of individual fans on both sides of Death Valley were revealed. [ABSTRACT FROM AUTHOR] more...

Hillslope surface classification via digital terrain analysis (DTA) is a current research focus in geomorphology and geographic information science (GIS) studies. However, traditional methods are generally based on raster digital elevation models (DEMs) and window difference methods, which suffer from terrain description and analysis scale mismatch issues. In this study, we propose a hillslope surface classification approach based on the vector structure. Triangulated irregular networks (TINs) are used as an example. Benefiting from free sampling with TINs, we apply terrain surface reconstruction to the original point cloud or DEM and then calculate the terrain derivatives based on the normal vectors of the optimized TINs. Finally, the fuzzy inference method is used to classify hillslope surface elements. We select two cases to evaluate the proposed method: a small watershed with dense point cloud data and a large region with complex landforms and a 30 m resolution Copernicus DEM. The results show that the proposed approach can effectively reduce the influence of DEM errors on classification and mitigate the scale mismatching problem in terrain generalization and analysis. A novel hillslope surface classification method with a new data structure is proposed to extend the application of vector methods and structures in DTA and GIS. [ABSTRACT FROM AUTHOR] more...

Grain size and surface roughness play crucial roles in modelling flow resistance and boundary shear stress in fluvial systems. However, the impact of grain size sorting on surface roughness, particularly for gravel-bed rivers composed of poorly-sorted sediments, has yet to be elucidated. Here we utilize a stochastic model to simulate generic riverbed surfaces, investigating the influence of sediment sorting on roughness. Through comparison with field-acquired data, we explore the relationships between grain size, sorting, presence of textural patches, and local roughness. Our analysis reveals significant spatial roughness variations on surfaces with poorer sorting conditions, driven by stochastic grain arrangements. Notably, surfaces with poorly sorted grains exhibit meter-scale patches, each with distinct roughness attributes. Consequently, upon characterizing the roughness of riverbeds made up of m-scale gravel bars, the sorting of the grains needs to be considered to account for the complexity of the relationships between water flow and riverbed. [ABSTRACT FROM AUTHOR] more...

The extreme conditions associated with Hurricane Ian, a large Category 4 hurricane, led to unprecedented damage to the barrier islands of southwest Florida. This study investigates the morphologic changes and sedimentological signatures of deposits resulting from Hurricane Ian along both developed and undeveloped barrier islands through a combination of sediment cores and pre- and post-storm digital elevation models. Laterally extensive washover deposits, measured up to 74 cm thick, were formed during the intensification phase of the storm surge and were primarily controlled by the degree of development and vegetation density along barrier-island interiors. Storm deposit sedimentology was influenced by the degree of development and position relative to the dune crest, with a large inclusion of anthropogenic debris along developed barrier-island interiors. During the subsiding phase of the storm surge, short, straight channels and longer, dendritic ebb-scour channels, measuring up to 2.4 m in depth, were cut into newly formed storm deposits and antecedent washover deposits from previous storms, reflecting time-dependent bidirectional sediment transport processes during Hurricane Ian. The results of this study demonstrate how bidirectional processes throughout a single large storm event have significant implications for the preservation potential of new and existing washover deposits, presenting a potential setback for long-term barrier-island migration. • Anthropogenic structures and natural vegetation influenced morphologic changes. • Storm deposit sedimentology varied with cross-shore location and vegetation density. • Bidirectional flows caused time-dependent erosion and deposition during the storm. • Ebb scour channels influence the preservation of new and antecedent storm deposits. [ABSTRACT FROM AUTHOR] more...

Due to the ongoing degradation of permafrost and the associated impacts on the stability of periglacial mountain slopes, there is a need to improve our understanding of the dynamics of rock glaciers over relatively short timescales. There is also a growing interest in the hydrological role of rock glaciers and other ice-debris landforms, as they can potentially store valuable amounts of ice. Despite the acceleration in rock glacier velocities observed primarily in the European Alps, annual and inter-annual changes in surface elevation and volume have so far escaped detailed quantification in monitoring programs. In this study, annual and biannual uncrewed aerial vehicle (UAV) surveys combined with structure-from-motion (SfM) photogrammetric techniques are used to derive high-resolution surface kinematics, elevation and volume changes of three rock glaciers in the Western Swiss Alps. Between 2016 and 2021, detailed digital elevation model (DEM) differencing revealed a high variability of mean annual elevation changes, reaching up to −0.19 ± 0.02 m/yr (2020−2021) at the Yettes Condjà B rock glacier, while elevation changes at the Les Cliosses rock glacier ranged from −0.05 ± 0.02 m/yr (2016–2017) to +0.014 ± 0.008 m/yr (2021−2021). In addition, the multi-temporal and very high-resolution topographic datasets revealed the presence of distinct rock glacier features, including superimposed lobes, lateral levees and flow divides, that could not be identified previously with traditional in-situ measurements and observations. Our results in terms of elevation and surface velocity changes highlight the importance of detailed and regular high-resolution monitoring for understanding the rapid evolution of active glaciers under the current degradation of mountain permafrost. • Centimetre-scale DEMs and orthomosaics are derived from UAV surveys. • Elevation changes range from −0.19 ± 0.02 m/yr to +0.014 ± 0.008 m/yr. • Short-term volume changes indicate a complex mass redistribution. • Annual elevation changes a novel complement to the study of rock glacier dynamics. [ABSTRACT FROM AUTHOR] more...

Cirques provide important information about the palaeoclimate conditions that produced past glaciers. However, mapping cirques is challenging, time-consuming, and subjective due to their fuzzy boundaries. A recent study tested the potential of using a deep learning algorithm, Convolutional Neural Networks (CNN), to predict boundary boxes containing cirques. Based on a similar CNN method, RetinaNet, we use a dataset of >8000 cirques worldwide and various combinations of digital elevation models and their derivatives to detect these features. We also incorporate the Convolutional Block Attention Module (CBAM) into RetinaNet for training and prediction. The precision of cirque detection with or without the addition of the CBAM is evaluated for various input data combinations, and training sample sizes, based on comparison with mapped cirques in two test areas on the Kamchatka Peninsula and the Gangdise Mountains. The results show that the addition of CBAM increases the average precision by 4–5 % (p < 0.01), and the trained model can detect the cirque boundary boxes with high precision (84.7 % and 87.0 %), recall (94.7 % and 86.6 %), and F 1 score (0.89 and 0.87), for the two test areas, respectively. The inclusion of CBAM also significantly reduces the number of undetected cirques. The model performance is affected by the quantity and quality of the training samples: the performance generally increases with increasing training samples and a training dataset of 6000 cirques produces the best results. This trained model can effectively detect boundary boxes that contain cirques to help facilitate subsequent cirque outline extraction and morphological analysis. • A deep learning model, RetinaNet, is trained by >8000 cirques for cirque detection. • The addition of an attention module (CBAM) in RetinaNet increases model performance. • The addition of CBAM also significantly reduces the number of undetected cirques. • The trained model detects 83 % and 93 % of the cirques in the two test areas. • Model performance is reduced by edge effects and inaccuracies in the training data. [ABSTRACT FROM AUTHOR] more...

Flow direction algorithms have been widely used to extract crucial terrain attributes of great hydrological and geomorphological significance. However, essential distinctions between the empirically-designed strategies of typical algorithms and the natural rules of physical dispersions bring various problems (e.g. parallel channel, artificial dispersion), leading to the low size and extent precisions of estimated results. In this work, geometrical and mathematical analysis is conducted on the inherent characteristics of physical dispersions along slope lines on local terrains. On each 3 × 3 window of digital elevation model (DEM), center pixel is divided into eight non-overlapping sub-facets. Necessary and sufficient (NS) conditions of size relationships between the elevations of adjacent pixels are summarized to directly identify the receiving facets of a sub-facet. Then, strict mathematical relations are derived between slope direction of a sub-facet and flow proportions allocated to receiving facets. A strategy is designed to re-adjust receiving facets and flow proportions for the boundary flow of adjacent facets. Lastly, a multiple-flow-direction algorithm called TFGA is proposed with the NS condition of size relationships, mathematical relation of slope direction with flow proportion, and adjustment strategy of boundary flow. Case studies are conducted for investigating the total contributing areas (TCA) and specific contributing areas (SCA) estimated by TFGA. Results reveal all-side superiorities of TFGA to typical algorithms in spatial patterns, error indicators and statistic characteristics of estimated TCAs and SCAs. Particularly, TFGA improves size precision of estimated results by approximately one order of magnitude. In a conclusion, we highly recommend TFGA for digital elevation analysis. • An algorithm called TFGA is built based on Triangular Facet and Geometric Analysis. • Mathematical relation is deduced between slope direction and flow proportion. • Necessary and sufficient (NS) conditions are deduced for receiving facets. • TFGA improves size precision of estimated terrain attributes significantly. [ABSTRACT FROM AUTHOR] more...

Phlegraean Fields and Ischia Island are large, densely populated, active volcanic structures located in the Campanian Tyrrhenian margin between the onshore and offshore sectors. While the emerged landforms provide significant insights into a series of intense volcano-tectonic events of the last 60 ka, our understanding of the sub-marine portion of these volcanoes remains limited due to its inaccessibility to direct exploration. In the last decades, the use of magnetic methods has proven to be useful in volcanic context, given the presence of large magnetization contrasts, whereas the implementation of a high-resolution Digital Elevation Model (DEM) has allowed the integration of detailed morphological analyses into the geophysical studies. In this work, we present two new high-resolution airborne and shipborne magnetic surveys, carried out by the National Institute of Geophysics and Volcanology (INGV) in the marine sector of the Phlegraean Fields caldera (Pozzuoli Bay) and surrounding sea sectors. Moreover, the new datasets have been integrated with older marine surveys carried out by the National Research Council (CNR) to extend the resulting magnetic anomaly map embracing the whole Campanian offshore volcanic structures, excluding Ischia Island. As a result, we present here three new magnetic anomaly maps used for an integrated interpretation of magnetic, morphological, and tectonic features. The study results provide valuable insights into the relationship between volcanic, magmatic, and tectonic activity, which may be useful for further investigations. Among the most notable findings are: the identification of the magnetic signatures of regional faults, previously unknown caldera structures, and a massive rock avalanche. Consequently, our research provides a significant contribution to seabed exploration aimed at identifying potential hazard factors in the study area. [Display omitted] • Morpho-magnetic data show volcano-tectonic structures in Naples and Gaeta Gulfs. • Strong magnetization contrasts reveal intrusions tightly controlled by tectonic. • We mapped giant caldera-like structure and paroxysmal landslides [ABSTRACT FROM AUTHOR] more...

Badlands are extremely fragmented landforms characterized by soil erosion processes at a short-time scale. In this paper, the annual evolution of hillslope morphological characteristics and erosion/deposition processes in a Sicilian badland area, surveyed on May 2021 and April 2022 by Unmanned Aerial Vehicles (UAVs), was investigated. Three-dimensional (3D) and planimetric (2D) approaches were applied to determine the badland morphometric characteristics. UAV surveys and photogrammetric 3D-model generation allowed for obtaining the digital terrain model and identifying the badland unit. The convergence index method was applied to evaluate the drainage network and its variation due to the erosion processes. The analysis highlighted a decrease of the morphometric indexes with increasing slope, which can be explained by the fact that the drainage network tends to be less tortuous and branched as slopes become steeper. The geomorphic change analysis showed that the soil erosion is evenly distributed along the badland slopes, while it is negligible along the drainage networks. The geomorphic changes due to slope collapses and soil erosion and deposition phenomena lead to a modification of the morphological characteristics of the badland unit, sub-units and the corresponding drainage networks. The results confirmed that badlands are intense erosion spots, with soil loss (approximately 348 t ha−1 y−1) much higher than the soil loss tolerance. Finally, the morphometric indexes were positively related to the sediment yield values, suggesting that in more extended and branched drainage networks sediment transport is more efficient. • Soil erosion is evenly distributed along the badland slopes. • Soil erosion is negligible along the drainage network. • Extended and branched drainage networks promote the sediment transport. • Badland areas are confirmed to be intense erosion spots. [ABSTRACT FROM AUTHOR] more...

There is a unique glacial landscape system in the southern Żarnowiec Moraine Plateau of northern Poland. Here the terrain is characterized by a very high concentration of ridges that are often adjacent to pits, which together constitutes a special type of hummocky topography. The morphological diversity of the study-area ridges and pits was determined from high-resolution lidar imagery that was qualitatively and quantitatively processed, then analysed. Fourteen test fields of spatial dimensions 0.5 km × 0.5 km were selected within the moraine plateau for detailed studies. The results show that the ridges and pits constitute a very dense network of approximately circular, diverse-oriented forms of various sizes, most of which are linked to each other in a step-wise fashion. The pits are surrounded by ridges of various heights and widths that separate one pit from another. A characteristic feature of the studied pits is the orientation of their long axis. Form-based morphological analysis revealed that their genesis was associated with a glacial rather than a periglacial environment. It is believed that ridge orientation reflects a spatial pattern related to ice crevasses. A moraine plateau constituted a terrain obstacle that acted as a counterslope to the advancing ice sheet. The studied landforms and landscape resulted from the ice sheet's breaking up into dead-ice blocks of various sizes. The very dense system of perpendicular, parallel, and diagonal crevasses was related to ice sheet advance from a northerly direction, resulting in a flow around the obstacle and differences in ice-mass speed. [ABSTRACT FROM AUTHOR] more...

Global warming significantly impacts sediment dynamics in glaciated catchments, affecting water resource operations, water quality, recreational activities, and ecological systems. The propagation of climate-change-induced geomorphic changes and the catchment's sediment yield are moderated by sediment connectivity, defined as the degree to which a geomorphic system facilitates sediment transfer. Quantifying functional sediment connectivity at the catchment scale remains a challenge. To address this, we propose a novel approach combining graph theory with the morphological method. This approach is exemplified through a detailed case study of a 2022 thunderstorm event in the Grastal valley, Tyrol, Austria. First, a graph of potential sediment cascades is constructed using a geomorphological map, a digital elevation model and a flow routing algorithm. A short-term Digital Elevation Model of Difference (DoD) from consecutive ALS surveys is then used to infer sediment fluxes and calculate the Sediment Delivery Ratio (SDR) for each landform. The primary sediment mobilising processes were debris flows and fluvial erosion, with a significant proportion of debris flow material being deposited on slopes, not reaching the fluvial corridor. Strong fluvial erosion was observed in the proglacial area, but the propagation of these geomorphic changes is halted by an alluvial fan and a lake. Most landforms can be clearly categorised as connecting or disconnecting features based on their SDR. In total, a maximum of 12 % of mobilised sediments exited the catchment. Our findings demonstrate that (i) short-term, catchment-wide DoDs are valuable for assessing functional connectivity at an event temporal scale, (ii) using landforms as fundamental spatial units allows for the identification and in-depth analysis of critical sediment sinks and sources, and (iii) graph analysis facilitates the catchment-wide calculation of sediment delivery ratios between meaningful fundamental units and the delineation of significant sediment cascades. • The morphological method was used to infer sediment fluxes of a 2022 debris flow event • Functional connectivity was assessed at catchment scale using graph theory with landforms as fundamental units • Most landforms could be clearly classified as connecting or disconnecting features • The fluvial system had high sediment delivery ratios, indicating supply limitation • Important disconnecting features were talus slopes, an alluvial fan and a lake at the margin of the proglacial area [ABSTRACT FROM AUTHOR] more...

The Garrotxa Volcanic Field is situated in the northeast region of the Iberian Peninsula. It represents the most recent volcanic area within the Catalan Volcanic Zone, which is one of the volcanic provinces of the European Rift System, featuring over 50 dispersed eruptive vents. This study presents a comprehensive morphometric analysis of volcanic edifices, aiming to enhance our understanding of both volcanostratigraphy and the geomorphology of landforms within the Garrotxa Volcanic Field. Our methodology involved extensive fieldwork and detailed analysis of Digital Elevation Models (DEMs) to precisely determine the spatial distribution and morphometric parameters of the best-preserved volcanic structures in the area. The Garrotxa Volcanic Field exhibits an uneven spatial distribution of various volcanic landforms, with approximately 50 % comprising magmatic cones, primarily formed through Strombolian eruptions. The remaining 50 % is evenly divided between magmatic-phreatomagmatic volcanoes and phreatomagmatic tuff rings-maars. The morphometric characteristics of the three genetic types overlap significantly, showing no clear differences, although a few distinctions can sometimes be identified. The Garrotxa Volcanic Field displays a variety of eruption styles: 46 % of the identified eruptive sequences begin with phreatomagmatic activity, while 54 % start with predominantly magmatic explosive activity. Most eruptions show a transition through different phases. Data also indicate that the morphometric variability at the Garrotxa Volcanic Field stems from differences in the properties of pyroclastic sequences, resulting from their diverse eruption styles, as well as pre- and post-eruptive factors. Consequently, the results of the morphometric analysis are deemed insufficient for establishing a reliable chronology for the Garrotxa Volcanic Field. [ABSTRACT FROM AUTHOR] more...

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. [Display omitted] • LiDAR DTM and smooth DTM difference is used to extract artificial terrain regions. • NDTM can identify lowland slopes of 1% or less even at resolutions higher than 15 m. • High-resolution NDTM enables automated lowland terrain classification using DTMs. [ABSTRACT FROM AUTHOR] more...

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. [ABSTRACT FROM AUTHOR] more...

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. • Volcano boundary extent is more crucial than DEM resolution for morphometric parameters. • Using a 3° slope threshold improves consistency of manual expert boundaries. • NETVOLC slope boundaries closely align with manual expert boundaries. • Volcano morphometry is more sensitive to DEM resolution than DEM type. • Morphometry from TanDEM-X generally shows the least variance and ASTER the largest. [ABSTRACT FROM AUTHOR] more...

Functional connectivity refers to the system dynamics and sediment transfer in a geomorphological system. It is usually quantified through digital elevation models of difference at two time-steps but measuring and quantifying sediment connectivity variation between the time-steps remains a challenge. In this study we utilised a combined approach of morphodynamic model and field observation for assessing seasonal spatio-temporal variation of longitudinal functional connectivity over a 6-kilometre sub-arctic river reach. Comprehensive field datasets including sediment sampling, monitoring of morphological change and continuous discharge and water level measurements, were collected multiple times during the year to calibrate and validate the model for one year. The results revealed that connectivity inside the reach is episodical and not all the morphological adjustment was tied to discharge. Connectivity varied spatio-temporally inside the reach and sediment source and sink areas could be detected. Outside of the hydrological controlled episodes, meander evolutional stage and grain size had notable role in sediment connectivity in the short-term, and therefore underlaying morphological adjustment in the long-term. This approach can contribute to enhancing already existing connectivity indices towards a functional model considering the seasonality and periodicity of connectivity in more detail and would therefore enhance river management and prediction of geomorphic systems functioning. • Combined approach for quantifying seasonal longitudinal sediment connectivity • Three connectivity episodes defined by threshold discharge magnitudes • Bend-to-bend morphological adjustment was not linear within the reach • River forms have short-term control over sediment connectivity [ABSTRACT FROM AUTHOR] more...

Climate change since the end of the Little Ice Age (LIA) has driven observed glacier volume loss, significantly contributing to the rise of global sea level. The related calculation of volume change requires knowledge of glacier surfaces from at least two points in time, usually represented by two digital elevation models (DEMs). These are typically derived from photogrammetric techniques using stereo images, but such images do not go back to the LIA. Accordingly, several techniques have been developed to reconstruct LIA glacier surfaces from historic outlines and modern DEMs. Here we first evaluate various surface interpolation methods by replicating modern glacier surfaces from outline elevation points and analyse elevation differences and uncertainties. Secondly, we investigate different GIS-based methods for LIA surface reconstruction including a new method that is based on up-scaling of recent glacier-specific elevation change data and works also for ice caps without lateral moraines. The methods were tested on 90 glaciers (covering 643 km2) in southern Novaya Zemlya and 266 glaciers (524 km2) in the Bernese Alps of Switzerland. As in previous studies, we also found that the Natural Neighbor and Topo to Raster interpolation methods in ESRI's ArcGIS performed best for glacier surface reconstruction and that all methods are challenged by replicating the variable surface curvature of glaciers. The new reconstruction method shows the smallest mean difference to the reference dataset (RMSE of 26.7 vs. 39.8 m). The often neglected small surface lowering in the accumulation area can increase the derived glacier volume changes by 30–50 % and should thus be considered whenever possible. Applying the up-scaling method to both test regions revealed that elevation change rates over the last two decades (−0.8 m a−1 for Novaya Zemlya and -1.14 m a−1 for the Bernese Alps) were much higher than from 1850 until today (−0.13 m a−1 and -0.22 m a−1, respectively). • We tested various surface interpolation methods on 90 glaciers in Novaya Zemlya and 266 in the Bernese Alps, and found that Natural Neighbor and Topo to Raster performed best. • We developed new and improved existing methods to reconstruct Little Ice Age glacier surfaces. • Our new up-scaling method is based on recent elevation changes and showed the smallest RMSE of 26.7 meters, it works well for any surface curvature including ice caps without lateral moraines. • Elevation change rates over the past 20 Years (-0.8 m a-1 for Novaya Zemlya, -1.14 m a-1 for the Bernese Alps) are much higher than those from 1850 until today (-0.13 m a -1 and -0.22 m a-1, respectively). [ABSTRACT FROM AUTHOR] more...

Landslides triggered by degrading mountain permafrost pose an increasing risk to life and infrastructure in mountain regions due to current climate change trends. Because discontinous mountain permafrost is not directly detectable by remote sensing, permafrost molards offer a way of indirectly detecting its location and state. Permafrost molards are cones of loose debris that are associated with landslide deposits. They originate from ice-cemented blocks of sediment that are transported downslope with the landslide. These ice-cemented blocks are fragmented parts of the permafrost initially located in the landslide source area. Over time, these blocks degrade into conical mounds with diameters typically ranging from decimeters up to 40 m. They indicate the presence of an area of degrading permafrost at the level of the detachment zone. The physical processes that lead to the formation of molards from the ice-cemented blocks have not yet been studied in detail. Therefore, we perform an experimental study to recreate molards in a controlled laboratory environment and investigate the key formation processes. We downscale the molards to an initial cube side length of ~30 cm, and reduced the model's complexity by using two different types of gravel with a defined granulometry and lithology. We quantified the degradation phase by using a novel photogrammetric time-lapse system to detect changes in the digital elevation model between half-hourly time-steps. For the first time, we successfully recreated morphologies resembling molards under controlled laboratory conditions on a decimeter scale. We find the main processes to produce the final molard shape are cascades of grainfall for slightly cohesive sediment, and individual grainfall for non-cohesive sediment. Our experiments reveal three possible cross-section shapes (bell-shaped, triangular, trapezoidal) that correspond to molards that can be found in the field. Along with these field observations, we suggest that it may be possible to identify the cohesion of a molard's sediment based on its morphology. Together with future field data and experiments investigating the granulometry, ice and clay contents of the initial ice-cemented block, we aim to use molards as a record to better understand the landslide dynamics and state of the mountain permafrost. • Successful reproduction of permafrost molard morphology in a controlled laboratory environment. • Determination of the most important processes in the formation of permafrost molards using time-lapse photogrammetry. • The flank angles of molards in the laboratory are up to 10 % steeper than the angle of repose of the respective material. • The cohesion of the molard material determines the molard's morphology and cross-section type. [ABSTRACT FROM AUTHOR] more...

Forested hillslopes are zones of specific surface hydrology and geomorphic activity regimes. Their distinct properties, namely terrain microrelief (<10 m in diameter and height), are often a result of past disturbances that control forest stand conditions, soil formation processes, and superficial processes. A clear bioindicator of the past forest disturbance is pit-mound topography, which, however, is challenging to study because of its complexity and relatively small sizes of individual forms (usually <5 m in diameter). The present study analyzed the spatial representation, geomorphometric, and geophysical evaluation of the rare pit-mound topography in the Karkonosze Mountains National Park, SW Poland, Central Europe. For this task, two digital terrain models (DTMs) have been considered and were based on different quality point clouds collected during airborne and terrestrial laser scanning (ALS and TLS, respectively). The first data allowed the production of the DTM in 1 × 1 m spatial resolution, while the second data offered the DTM in 0.025 × 0.025 m resolution. Various geomorphometric derivatives (Terrain Ruggedness Index, Geomorphons, Topographic Wetness Index, Valley Depth, and Negative Openness) were applied and compared based on these models. In the further part of the study, we applied electrical resistivity tomography (ERT) and electromagnetic induction (EMI), assisted by shallow soil sampling and analyses to support the interpretation of geophysical models. Our TLS-based DTM offered higher-quality models and a better representation of pit-mound topography. The high-quality TLS-based DTM elevation model can support close-to-reality hydrological and geomorphic modeling. The geophysical investigation allowed us to isolate a critical difference between treethrow pits and mounds better represented by ERT models than shallow EMI models. The differences were partly supported by soil properties, namely lower electrical resistivity in treethrow pits were related to higher moisture conditions, organic matter, organic carbon, and silt content in pits. As a general property, pit-mound topography resulting from tree uprooting adds to the complexity of forested hillslope hydrology and geomorphic activity. The surficial heterogeneity in hillslope topography was also evident in soil properties with sharp changes in short distances between treethrow mounds and pits. • Pit-mound topography expressed the most recent history of soil formation. • TLS-based DTM represents better complex pit-mound topography. • ERT reflects the main near-surface properties of treethrow pits and mounds. • Higher humus thickness, Corg, and silt content were found in treethrow pits. • The spatial model of negative openness represents better complex pit-mound topography. [ABSTRACT FROM AUTHOR] more...

Filtered Geomorphic Reference Models (FGRMs), extracted from High-Pass Filters based on the Fast Fourier Transform (HPF-FFT), provide a semi-automated and objective detection of a wide range of geoforms and geomorphic situations (flat areas, slopes, depressions, or valley bottoms). The method is sensitive enough to reveal numerous inflection points that enable the identification of subtle changes in relief polarity, resulting in accurate representations of real land depressions. The effectiveness of this method has been demonstrated in lunar landscapes, utilizing altimetry extracted from high-precision Planetary Digital Elevation Models (PDEMs) to construct crater inventories with well-defined FGRMs. However, when analysing lunar environments with closely-spaced geomorphic features, the FGRMs display blurring and generalization effects, reducing their capability to identify all existing crater depressions. This limitation controls the ability of FGRMs, to generate reliable crater inventories. This study examines such effects in three experiments. Using Synthetic Digital Relief Models (SDRMs) constructed by means of a MATLAB script two experiments are performed. In Experiment_1 different scenarios of proximity between aligned craters are analysed. The marks, or footprints, formed by craters of identical size and shape (i.e., circular bowl-shaped depressions with central peaks) are considered, resulting in simplified PDEMs. Various scenarios of crater centre separation (proximity) and the presence of internal features within craters are also analysed. Experiment_2 validates the method with different proximities, locations and crater sizes. Experiment_3 validates the approach in a sampled area of LRO lunar PDEM corresponding to Zelinskiy crater (Mare Ingenii area). To address these blurring effects, a hybrid methodology is employed, generating FGRMs extracted from HPF-FFT, in conjunction with other GIS and remote sensing tools, such as singular point zoning, aspect-slope zoning, and edge-limits zoning. As a result, the correspondence between the FGRMs and the synthetic forms is examined, aiding the comprehension of the graphical response provided by filtering in these cratered areas. The methodology demonstrates that FGRMs derived from HPF-FFT are sensitive to capturing connections between shapes as soon as the crater features start to merge, while blurring becomes evident when the craters are located at a proximity of <20 model units. Additionally, the results highlight the method's utility in accurately locating crater footprints and morphologically characterizing inner crater features, even when crater centres are closely spaced. This approach effectively mitigates blurring effects and enables the precise localization of crater marks and their internal features. The validations carried out in complex relief and high precise DEMs provide a use in real situation. [Display omitted] • SDRMs of nearby craters at different proximity distances are generated using a MATLAB script. • FGRs of craters extracted from FFT filtering yield inaccurate inventories due to blurring effects. • Different scenarios of crater proximity are designed to evaluate the answer provided by filtering. • Combined use of FFT filtering, GIS and remote sensing tools is sensitive to blurring. • The morphological characterisation of simulated craters improving crater inventories. [ABSTRACT FROM AUTHOR] more...

Accurate digital elevation models represent the basic tool for a large spectrum of applications, including geological, architectonic, archaeological, and urbanistic studies. However, aggressive urbanization may significantly alter the morphology of areas of interest. Such is the case of the active Campi Flegrei caldera in southern Italy, where all the buildings, facilities, infrastructures, quarries, and landfills altered the original volcanic morphology. To avoid these limitations, we analyzed a set of vintage aerial photographs acquired in 1943 by Italy's Military Geographic Institute (IGM). We reconstructed the study area's topography before the deep anthropic modification from the 1960s onwards by applying Structure-from-Motion photogrammetric processing. On the reconstructed orthomosaic and a historical-Digital Surface Model (hDMS), we conducted geomorphic analyses along 18 longitudinal stream profiles outside, across the border, and inside the caldera, underlining that the rectilinear sections with preferred orientations and increased incision values suggest a strong structural underpinning on valley incision and stream paths. The analysis of the spatial distribution of sinuosity, SL index, Chi (χ) value and knickpoint maps suggests the presence of tectonic lineaments that influence the stream network from the pre-caldera (>40 ka) to recent times, producing articulated caldera and craters geometry as well as affecting the localization of volcanic vents. The comparison between the 1943 hDSM and 2013 LiDAR (Light Detection and Ranging) DSM allowed us to spotlight the areas that show the most significant differences due to anthropic intervention that obliterated critical features, thus supporting our motivation to use this base. Overall, the results indicate that long-lived volcano-tectonic and tectonic structures control the orientation of drainage patterns and their re-arrangements during volcano-tectonic deformation phases. Finally, a comprehensive structural map, based on the merged 1943 hDSM and the bathymetric DEM, is presented together with a conceptual evolutionary model of the stream network across the caldera border. Under the proper acquisition conditions, vintage aerial photographs can provide a useful tool for morphological analysis and can be applied to several topics in the geosciences. • The original topography of Campi Flegrei is restored using historical aerial photographs. • Several geomorphic indices highlight the activity of volcano-tectonic structures. • Rectilinear and deeply incised valleys occur in different sectors. • NE–SW and NW–SE oriented tectonic features are overprinted by E–W oriented features. • Tectonic lineaments control the occurrence of volcanism through time. [ABSTRACT FROM AUTHOR] more...

The Co nfined M orphologies Ma pping (CoMMa) Toolbox, a novel ArcGIS Pro python toolbox expressly created for semi-automated seabed morphological mapping, is presented here. The toolbox includes a selection of tools for the pre-processing, delineation and description of confined features on a digital elevation model (DEM) that are either negative or positive. The CoMMa Toolbox addresses the need for a flexible and multi-faceted solution applicable to different mapping problems, also encapsulating and re-interpreting existing methodologies. This study also evaluates, qualitatively and quantitatively, the performance of CoMMa delineations performed on a synthetic bathymetry DEM with 150 coral mounds of known characteristics against manual digitisations completed by five expert geomorphologists. The results show that the best CoMMa delineation falls within the range of competence demonstrated by the expert manual mappers. Edge evaluation metrics and attribute error scores are comparable or often superior to four of the five human delineations, although the Toolbox never reaches the performance of the best expert. Nevertheless, the semi-automated techniques can be of assistance to any user, providing rapid, visually unbiased and consistent delineations, thus saving time: they can then be optimised manually where desirable. Moreover, while the toolbox was created for marine geomorphometry, it can be applied to any DEM, either marine, terrestrial or extra-terrestrial. The CoMMa Toolbox is available in a public GitHub repository with a thorough user guide. • We present CoMMa, a toolbox that allows users to characterise confined morphologies. • A synthetic seabed DEM was used to gain statistical control on the accuracy of the toolbox. • CoMMa delineations are compared to those done manually by five expert mappers. • The results by CoMMa are as precise or better than those of the manual mappers. • CoMMa is freely available on GitHub with a complete User Guide. [ABSTRACT FROM AUTHOR] more...

The Upper Verde River in northern Arizona, USA is a vital resource for the wildlife and humans that rely on its waters. We characterize the riparian corridor topography using terrestrial laser scanner (TLS) data from 2021 to 2022. We also quantify geomorphic changes associated with human and climate-driven alterations in river flow and vegetation changes by combining the contemporary lidar surveys with legacy measurements from single line geomorphology transects measured by the United States Forest Service (USFS) in 2009. Seventeen plots along the Upper Verde River were surveyed with the TLS and the data were coregistered within individual plots with a Root Mean Square Error of <0.03 m among scan positions. Digital Elevation Models (DEM) were derived for each plot from the TLS data at 10 cm resolution and compared to the 2009 USFS cross-section data to quantify elevation changes. In areas with statistically significant change, we detected maximum changes in elevation due to erosion and deposition of −0.37 m and + 0.97 m, respectively. Topographic changes over the 13-year period were predominately aggradation and associated with sediment deposition, which we hypothesize might have resulted from altered river flow and vegetation encroachment. This study also demonstrates a quantitative and statistical methodology to fuse traditional single line cross-section data with contemporary lidar data to quantify geomorphic change. The novel approach demonstrated here is broadly applicable to natural resource managers for integrating and contextualizing legacy topographic data for understanding past, present, and future landscape and habitat changes. [ABSTRACT FROM AUTHOR] more...

This study applies semi-automated techniques to analyze the landforms, morphostructure, and geology of the Kharaulakh and Chekanovsky sectors, south of the Lena Delta, northern Siberia. High-resolution data, including TanDEM-X 30 m spatial resolution Digital Elevation Models (DEM), 2 m spatial resolution ArcticDEM Digital Surface Models (DSM), and Sentinel-2 satellite imagery, serve as the basis for the analysis. Digital terrain classification and identification of tectonic lineaments are performed using the Benthic Terrain Modeler (BTM) and Linear Extraction (LINE) algorithm, respectively. Additionally, a hypsometric analysis is conducted to assess areas of potential neotectonic activity. 873 lineaments are identified, primarily in NE-SW and E-W orientations. NW-SE lineaments perpendicular to the lithological and fold belt strikes in the Kharaulakh Ridge suggest inheritance from original depositional settings or later compressional tectonics, now appearing as valleys and weak zones facilitating erosion and river incision. Longer N-S or NNW-SSE lineaments in the Kharaulakh Sector are associated with thrust sheets of the Verkhoyansk fold-and-thrust belt and Cenozoic graben structures linked to the formation of the Laptev Sea Rift System and ongoing regional deformation. The Chekanovsky Sector, marked by epiplatform blocks and hills, presents a dissected plateau with steep valleys. Here, high hypsometric integral values are attributed to compression and uplift near the southwestern boundary of the Laptev Sea Microplate. • Identified 873 lineaments in northern Siberia using comparative remote sensing • Employed Benthic Terrain Modeler for semi-automatic terrain classification • Neotectonic reactivation alters local geomorphology, inferred by hypsometric analysis. • Lineaments impose Mesozoic folding, faulting, and stratigraphic boundaries. [ABSTRACT FROM AUTHOR] more...

This research assessed the efficacy of deep segmentation in identifying and measuring natural karst depressions in the Bambuí Group's carbonate rocks in Western Bahia, Brazil. The investigation used five Global Digital Elevation Models (DEMs) with 30-m resolution: Advanced Spaceborne Thermal Emission and Reflection Radiometer - Global Digital Elevation Model version 3 (ASTER-GDEM v3), Advanced Land Observing Satellite World 3D – 30 m version 3.2 (AW3D30 v3.2), Copernicus 30 m global DEM (GLO-30), NASA Digital Elevation Model version 1 (NASADEM v1), and Shuttle Radar Topography Mission version 3 (SRTM v3). The karst feature detection analysis compared five semantic segmentation architectures: Feature Pyramid Networks (FPN), LinkNet, UNet, UNet++, DVL3+, using an EfficientNet-B7 backbone, one instance segmentation model (Mask-RCNN), and a semantic-to-instance conversion method. This comparison considers different datasets, including one, two, or eleven variables (DEM, DEM-based sink depth, and nine terrain attributes). Besides, we performed a combinatorial analysis of the DEMs to evaluate the improvement in karst feature detection. The methodology involved the generation of geomorphometric attributes, sample labeling from Sentinel-2 and Operational Land Imager-Landsat 8 datasets, training-validation-testing steps with 128 × 128 samples, reconstruction of large images for semantic and instance segmentation, and accuracy analysis. The findings revealed that GLO-30 and AW3D30 data were the most accurate, while ASTER GDEM performed poorly in both segmentation forms. Among the semantic models, FPN showed the highest accuracy. The 11-variable models preferentially outperformed those with fewer in both types of segmentation. The approach of semantic-to-instance conversion with Geographic Information System tools favored individualizing karst depressions and obtaining efficient quantification, consisting of an easy alternative to achieve instance segmentation. Reconstruction of large remote sensing images through sliding windows considering the specifics of instance and semantic segmentation demonstrated that smaller stride enhances object coverage and reduces the risk of losing crucial information, effectively improving the predictions. The combinatorial analysis for semantic and instance segmentation indicates that models incorporating more DEMs (4- and 5-DEM models) and variables achieve generally higher accuracy. The best result in semantic segmentation was combining the five DEM datasets using 11 variables, reaching an F-score of 85.06 and IoU of 74.00. In instance segmentation, the best result for the bounding box was the model that integrates AW3D30, GLO-30, NASADEM, and SRTM with eleven variables reaching Average Precision (AP) of 45.64, AP50 of 88.40 and AP75 of 39.38, while the best result for the segmentation mask was the model that integrates the five models with eleven variables with AP of 42.61, AP50 of 86.79 and AP75 of 35.43. These results demonstrate that integrating a wide range of DEM data, even the lowest performing ones, improves model generalization and accuracy in segmentation, leveraging strengths and mitigating individual weaknesses. Future work could explore high-resolution DEMs and the integration of various deep-learning methods. [Display omitted] • First deep segmentation investigation for karst depression detection in Brazil. • Copernicus Digital Elevation Model with 30-m resolution achieved superior accuracy. • Feature Pyramid Network was more accurate model in detecting karst depressions. • Combining digital elevation model with morphometric attributes improves accuracy. • Successful quantification using semantic-to-instance segmentation conversion. [ABSTRACT FROM AUTHOR] more...

Field surveys to collect data from fluvial ecosystems traditionally focus on specific phenomena related to geomorphology or hydrology. Low-cost unmanned aerial vehicles (UAVs) additionally empower the fast and massive collection of airborne photogrammetry, providing geospatially explicit information. This remote sensing data complements field surveys by offering contextual information on geomorphological conditions, including digital terrain models. AI-based image recognition can augment contextual information to extrapolate archetypal object classes through name labels, such as "gravel", "sand", "plant", or "large wood". However, obtaining sufficient ground truth data for these classifications, particularly in morphodynamic fluvial environments, is challenging and induces high costs. This study introduces a transfer learning approach to address the challenge of low data availability, enabling AI-based mapping of complex objects in fluvial landscapes. We leverage the learned general structure of a deep convolutional neural network (CNN) pre-trained on a broad range of images. The fixed latent features of the pre-trained CNN stem from GoogLeNet. A fixed feature extractor serves to classify objects with limited data amounts. Satisfactory performance is measured with a recall rate, expressing the ability of a model to find all occurrences of a class on an image. High spatial heterogeneity in the locations of measurements on the x-y plane improves model performance. With a minimum of 400 labeled instances, the model achieves a satisfactory 93.75-% recall for a "large wood" target class, providing evidence of the effectiveness of transfer learning in remote sensing for geomorphological studies. This ability to detect large woods in river environments is critical to restoration efforts as it helps create fish habitat, which is essential to supporting biodiversity. [Display omitted] • UAV data augments costly field data from rivers, enabled by transfer learning. • A pre-trained CNN based on GoogLeNet recognizes target features with high recall. • True positive detections of a large wood target feature signify high recall. [ABSTRACT FROM AUTHOR] more...

Obtaining accurate representations of the Earth surface topography is paramount in many geomorphological investigations. While regional scale studies use Digital Elevation Models (DEM) with resolution of the order of 10–100 m, in many applications resolution < 5 m are mandatory to appropriately represent landforms and processes of interest. In particular, hillslopes, which cover the most of continental surfaces, have typical length of the order of 100 m. For that reason, high resolution topographic data are mandatory to correctly represent their morphology. The massive use of higher resolution topographic data has been enabled by a vast array of methodological developments, among which terrestrial and airborne Light Detection And Ranging (LiDAR) or uncrewed aerial vehicle-based photogrammetric approaches are the most commonly used. However, such techniques might be difficult to deploy and not cost-effective, to cover large areas in remote locations. In this study, we present an exploration of the potential of topographic data derived from Pléiades imagery for the characterizing hillslope morphology. We focus on the Gabilan Mesa area in California, where a LiDAR DEM is available and is used as a benchmark. We systematically compare Pléiades-derived topographic data with the DEM constructed from LiDAR data, starting from simple elevation analysis and then using topographic derivatives, such as slope or curvature, which are commonly used in morphometric studies. Finally, we take advantage of the high resolution of the datasets to extract and compare hillslope-scale morphometric parameters, such as length, relief, or hilltop curvature. While some particular situations, such as planar and horizontal surfaces, requires specific attention in terms of the relative differences between the two type of data, the absolute values for the metrics are in good agreement over their relevant range of utilization for hillslope-scale geomorphology. [ABSTRACT FROM AUTHOR] more...

Land-surface quantitative analysis based on digital elevation model (DEM) has been applied for improving the geomorphological mapping of piedmont alluvial fans. Indeed, these fans are frequently along a mountain front, where a series of coalescing fans may eventually occur. The margins of adjacent fans are rather difficult to map, thus preventing accurate and meaningful quantification of fan morphometric properties such as fan area, length, and slope. These morphometric properties are essential for informing on the influence of climatic conditions and tectonic factors on the fan-building processes. Therefore, in this paper, we propose a quantitative digital mapping approach along a stretch of about 50 km in the southern front of the Anti-Lebanon Mountains. Here, the Geomorphological Map of Syria at 1:1,000,000 scale (1963) reported at least nine piedmont alluvial fans, but these were poorly characterized in terms of geomorphometric characteristics and construction processes. Adopting the 1-arcsec SRTMv3 DEM, we propose a four-step workflow to analyse the feeding catchments morphology and fan morphometry. In this manner, the identification and geomorphological mapping of coalescent piedmont fans as well as the recognition of the main construction process have been improved. The proposed approach can support geomorphological investigations of wide and inaccessible areas—especially where arid and semi-arid climate conditions prevail—as well as where socio-political issues may prevent effective field work. • Land-surface quantitative analysis is suitable for geomorphological mapping and characterization of piedmont alluvial fans. • Recognition of the construction processes of the alluvial fan is challenging for a remotely-desk study. • Fluvial fans (FFs) are wider, with longer axis, gentle slope, and extended feeding catchment. • Alluvial fans (AFs) are smaller, with shorter axis, steeper slope, and small feeding catchment. [ABSTRACT FROM AUTHOR] more...

Rainfall-triggered volcanic debris flows (VDFs), or lahars, frequently occur during and/or immediately after eruptions, often because of decreases in the infiltration capacity resulting from the deposition of fine volcanic materials. Although the infiltration capacity recovers and the frequency of VDFs decreases within a decade, VDFs have continued to occur over several decades after the eruption of some volcanoes. No study has yet identified the factors controlling sediment discharge of VDFs for a specific volcano after the recovery of infiltration capacity to the pre-eruptive level. We analyzed topographic changes and sediment volumes between 2003 and 2020, using 16 digital elevation models (DEMs) and orthophotographs from aerial lidar scanning for the Tansandani and Gokurakudani gullies of Mount Unzen where the infiltration capacity has recovered after the most recent eruption in 1990–1995. We also analyzed the frequency and magnitude of VDFs in 2003–2020. Topographic changes differed before and after three large-scale VDFs in 2015 and 2016. The total volume of the three VDFs was 140 × 103 m3. Between 2003 and 2014, the width and depth of the gullies continuously increased, with the changes in the intervals of successive DEMs averaging below 5 m. Between 2017 and 2020, gully cross-sections remained U-shaped and changed little, while the channel gradient gradually decreased. U-shaped gullies promote the dispersion of VDFs and their gentle slopes reduce the velocity of VDFs. As a result, the frequency and magnitude of VDFs decreased, and deposition and erosion in the gullies were almost balanced between 2017 and 2020. Thus, we conclude that topography is the main factor that controls the occurrence and magnitude of debris flows and therefore sediment discharge after the recovery of infiltration capacity to the pre-eruptive level. [Display omitted] • Volcanic debris flows (VDFs) continue for several decades after volcanic eruption. • We conducted monitoring of VDFs and topographic analysis at Mount Unzen. • Recent gully geometry change made VDF hydraulic development harder. • The frequency and magnitude of VDFs decreased in recent years. • Topography would be a factor controlling recent VDFs. [ABSTRACT FROM AUTHOR] more...

Data collected between 2015 and 2022 was utilised to assess longitudinal connectivity and explain the temporal and spatial fluctuation of large wood (LW) along the Blanco River, which was severely affected by the 2008 eruption of the Chaitén Volcano in southern Chile. The study was performed along a ~ 10.6-km long segment, which was divided into two sub-segments (upper and lower). LW source areas were identified using information from previous research, complemented by the analysis of satellite images to cover the study period. LW fluctuation was studied for the period 2017–2022, using field data and images from an unmanned aerial vehicle along seven 80 m-long reaches located within the lower sub-segment of the river. Using the generated georeferenced orthomosaics and digital elevation models, LW and wood jams (WJs) locations, abundance, dimensions, volumes, and WJs stability were assessed, as well as wood deposition patterns. Streambank erosions and landslides were found to be the main LW sources. Considering wood sourcing, and the variations in the number of LW and WJs, in the dimensions of individual LW and WJs volume and deposition patterns as indicators, it was possible to infer the longitudinal connectivity conditions for the studied segment through time. The results showed that the upper and lower subsegments were poorly connected. However, changes in LW abundance over time, its dimensions and volumes, and the very low stability of WJs, and LW deposition patterns indicative of fluvial transport confirmed that the lower subsegment was longitudinally connected. The results also verified that the presence of LW did not affect water or sediment longitudinal connectivity along the fluvial system. The volume of individual LW and WJs showed a decreasing trend with time in all study reaches. As the bank erosions able to source LW to the channel are also reducing with time, pieces of wood deposited in the active channel may become the only way to sustain LW availability for the next few years. Things could change with the occurrence of an extreme and infrequent flood able to connect the upper and lower sub-segments and force the river to initiate a new phase of planform adjustments. [Display omitted] • Large wood (LW) was studied in a river affected by a volcanic eruption. • LW volume decreased from upstream to downstream and with time since the eruption. • Different degrees of connectivity were derived from a semi-quantitative approach. • LW is not affecting longitudinal water and sediment connectivity along the river. [ABSTRACT FROM AUTHOR] more...

Flow direction algorithms have important application in attracting geomorphic features and topographic attributes, which serve as inputs for some hydrological and topographical models. Evaluating flow direction algorithms is of great significance and often conducted on synthetic surfaces instead of real digital elevation models for free of approximation errors. However, most widely-used synthetic surfaces are too simplified to represent complex topographical relief of real-world terrains. For this, this work applies a complex synthetic surface of modified Himmelblau's function (HF) to simulate sophisticated terrains encountered in real landscapes. HF surface is spatially smooth and continuous with four hilltops and one valley, where plan curvatures are clustered mainly from −0.1 to 0.1. In addition, a slope line-based discretization numerical (SLDN) approach is designed for obtaining numerical solution to theoretical total contributing area (TCA) on synthetic surfaces of non-integrable slope lines (e.g. HF surface). TCAs estimated by several flow direction algorithms are compared with SLDN-derived TCA quantitatively. Results indicate that the largest and smallest mean size errors are obtained by Random eight-node (Rho8) (i.e. 82.6 %) and Freeman multiple flow direction (FMFD) (i.e. 17.9 %), while the largest and smallest mean extent errors by Eight drainage directions (D8) (i.e. 128.2 %) and Eight drainage directions, least transversal deviation (D8-LTD) (i.e.55.4 %). Most mean errors are larger than 20.0 %, which may not be satisfactory in practice. This work can provide a reference for flow direction algorithms application in digital terrain analysis, and therefore improve accuracy of hydrological, geological and geomorphological models. [Display omitted] • Characteristics of the complex HF surface are comprehensively investigated. • An SLDN approach is used to obtain theoretical TCAs on complex synthetic surfaces. • D8-LTD and FMFD are respectively the best SFD and MFD algorithms on HF surface. [ABSTRACT FROM AUTHOR] more...

Quaternary glaciations have created impressive landform assemblages that can be used to understand palaeo-glacier extent, character and behaviour, and hence past global and local glacier forcings. However, in the southern hemisphere and especially in New Zealand, the Quaternary glacial landform record is relatively poorly investigated with regard to glaciological properties. In this study, a 1 m digital elevation model (DEM) was generated from airborne LiDAR data and supplemented with aerial imagery and field observations to analyse the exceptionally well-preserved glacial geomorphology surrounding Lake Tekapo, New Zealand. We describe a rich suite of Last Glacial Maximum (LGM) and recessional ice-marginal, subglacial, supraglacial, glaciofluvial and glaciolacustrine landform assemblages. These represent two landsystems comprising i) fluted till surfaces with low-relief push moraine ridges; and ii) crevasse-squeeze ridges, 'zig-zag' eskers and attenuated lineations. The former landsystem records the behaviour of an active temperate glacier and the latter landsystem, which is superimposed upon and inset within the former, strongly suggests intermittent surge phases. The two landsystem signatures indicate a sequential change in ice-marginal dynamics during recession that was likely to have been partially non-climatically driven. Overall, we present the first evidence of surge-type glacier behaviour in New Zealand. • LiDAR topographic data used to identify glacial landforms in New Zealand • Landform assemblages indicative of landsystem superimposition • Overall active temperate glacier recession punctuated by intermittent surge phases • First evidence of surge-type glacier behaviour in New Zealand • Changes in ice-marginal dynamics partially non-climatically driven [ABSTRACT FROM AUTHOR] more...

The existence of former glacial lakes remains poorly documented in the remote regions of the Canadian Shield where the dense forest cover and poor access complicate classical mapping methods. Here we use a high-resolution Digital Elevation Model (DEM; 1 m/pixel) based on LiDAR data to map Quaternary deposits and landforms in the vicinity of the Gouin reservoir in the Laurentian Highlands of Quebec (Canada). A total of 598 raised shorelines were identified, providing new evidence for the presence of a large proglacial lake – Lake Obedjiwan – that formed in front of the northward retreating Laurentide ice sheet margin during the last deglaciation, a few kilometers east of the larger Lake Ojibway that covered extensive areas in northern Ontario and Quebec. The elevation of shorelines outlines a tilted water plane that depicts the influence of the glacio-isostatic adjustment across the basin, with shorelines ranging from 409 m in the south to 439 m in the north. The calculated uplift gradient of 0.78 m/km indicates that the lake developed during the early stages of the deglaciation. Our reconstruction constrains the full areal extent and maximum elevation of the lake, which covered an area of 1800 km2 and reached an elevation of 450 m. It also indicates that Lake Obedjiwan developed independently from Lake Ojibway. The lake-surface elevation was controlled by an outlet located in the southeastern part of the basin where a topographic depression lying at an elevation of 390 m routed meltwater overflow southward through the Saint-Maurice River and into the St. Lawrence River. Another important outlet is located in the northernmost part of the basin and ice retreat beyond this topographic depression (427 m) caused the drawdown of the Lake Obedjiwan, which drained westward into Lake Ojibway. This discharge added around 19 km3 of meltwater, an event that likely impacted the hydrological budget and sedimentology of Lake Ojibway. The results suggest that other glacial lakes probably developed along the southern LIS ice margin and that the approach developed in this study may contribute to the refinement of their areal coverage and improve paleogeographic reconstructions. • A glacial lake was documented by 598 shorelines mapped on a LiDAR DEM. • A DEM-based reconstruction constrains its configuration and evolution. • The maximum areal extent of Lake Obedjiwan was 1800 km2. • The lake uplift gradient (0.78 m/km) suggests an early deglacial age. • Drainage of the lake added ~19 km3 of meltwater to Lake Ojibway. [ABSTRACT FROM AUTHOR] more...

Drainage network extraction plays an important role in geomorphologic analyses, hydrologic modeling, and non-point source pollutant simulation, among others. Flow enforcement, by imposing information of known river maps to digital elevation models (DEMs), leads to improved drainage network extraction. However, the existing flow enforcement methods (e.g., the elevation-based stream-burning method) have certain limitations, as they may cause unreal longitudinal profiles, lead to unintended topological errors, and even misinterpret the overall drainage patterns. The present study proposes an enhanced flow enforcement method without elevation modification towards an accurate and efficient drainage network extraction. In addition to preserving the Boolean-value information as to whether a DEM pixel belongs to a stream, the proposed method can also well preserve and fully utilize the topological relations among mapped streamlines and morphological information of each mapped streamline. The method involves two important steps: (1) proposal of an improved rasterization algorithm of mapped streamlines to yield continuous, unambiguous, and collision-free raster equivalent of stream vectors for flow enforcement; and (2) realization of the enhanced flow enforcement in a modified Priority-Flood procedure –– in this way, flows are enforced to completely follow the mapped streamlines, and hence, channel short-circuits and spurious confluences of adjacent streams are avoided. An efficient implementation of the method is made based on a size-balanced binary search tree. The method is also tested over the Rogue River Basin in the United States, using DEMs with various resolutions. Visual and statistical analyses of the results indicate three major advantages of the proposed method: (1) significant reduction in the misinterpretation of drainage patterns; (2) maximum channel displacement of one pixel to the river map at various resolutions; and (3) high computational efficiency. • An improved method to extract drainage networks from DEMs and river maps is proposed. • An improved rasterization process to avoid misinterpretation of vector streams is attempted. • Mapped streams are incorporated in the Priority-Flood procedure without modifying a DEM. • Topological and morphological information of mapped streams are well preserved. [ABSTRACT FROM AUTHOR] more...

Elongated tracts of hummocks or 'hummock corridors', exposed on palaeo-ice sheet beds, are believed to represent former subglacial meltwater pathways. Here, we present a method, coded in MATLAB, for automatically detecting and mapping hummock corridors from high-resolution digital elevation models (DEMs). Initially the DEM is filtered to remove bed roughness outside the size range of hummocks. A Fast Fourier Transform is then performed to determine the dominant orientation of hummock corridors and remove misaligned features. Finally, image segmentation is used to isolate and extract the hummock corridors as a binary mask. The automated approach is tested visually and statistically against detailed manual mapping in three areas of Canada and northern Scandinavia. Results show that while the automated method does not perfectly reproduce the manual mapping, it successfully captures the general configuration, morphometry (length and width) and location of hummock corridors, despite variation in expression across and between sites. This technique is ideally suited to take advantage of newly available high-resolution digital elevation data (e.g. the ArcticDEM), whose enormous volume makes large-scale manual mapping prohibitively time consuming. Its application will enable efficient and comprehensive mapping of the spatial distribution of hummock corridors across palaeo-beds that is necessary for deriving insights into their formation and the organisation of subglacial meltwater flow beneath ice sheets. • Elongated tracts of hummocks or 'hummock corridors' on palaeo-ice sheet beds represent former subglacial meltwater paths. • We develop a method that isolates hummock corridors from high-resolution DEMs using image processing techniques. • The method rapidly approximates the large-scale pattern of hummock corridors at an ice-sheet scale. • Resulting information can be used to gain insight into the nature and evolution of subglacial meltwater drainage. [ABSTRACT FROM AUTHOR] more...

Drainage divides play significant roles in shaping landscapes. Nevertheless, they are not static through space and time. Previous numerical models have demonstrated divide motions in response to asymmetric tectonic uplift. However, natural examples that have nicely recorded these processes and hence could verify the results of numerical simulations are still lacking. In this contribution, we integrate the results of digital elevation models (DEMs)-based morphotectonic analysis with the tectonic landforms observed during field surveys to investigate the status of topography and probable drainage evolution history of the Wula Shan (Shan means 'Mountain(s)' in Chinese), a roughly west-east trending horst block bounded by normal faults in the Hetao Graben, North China. The results demonstrate that the differences of obtained geomorphic indices are significant between the southern and northern drainage basins; higher hypsometric integral (HI) and normalized channel steepness (k sn) values, and lower ratios of valley floor width to valley height (VF) indicate higher tectonic uplift rate at the southern flank. The main divide of the Wula Shan had migrated northward, which was probably caused by the decrease of asymmetry in vertical uplift associated with the margin faults. We suggest the results of this study may shed new light on divide mobility as well as landscape evolution in actively extending regions. [ABSTRACT FROM AUTHOR] more...

The width of the valley floor dictates the structure and function of the associated river or stream at the macro level. Consequently, the valley floor width is increasingly recognized as a key parameter and has been employed for many applications (e.g., river classification). Here, we propose an automated algorithm approach to extract the valley floor width of U- and V-shaped valleys by using the breakpoint of the slope between the valley wall and valley floor to support digital elevation models (DEMs) of different resolutions. The algorithm includes five steps: 1) preprocessing data, 2) extracting linear reach, 3) extracting perpendiculars of reaches, 4) delineating the outlines of the valley floor and 5) calculating the width of the valley floor. Eight case studies were used to validate the algorithm. Valley floor outlines and widths were computed and measured, revealing that the algorithm performs well with a high correlation coefficient (CC > 0.88) and coefficient of determination (R 2 > 0.77), as well as low relative bias (| RB | < 10%). The algorithm performs better when applied in U-shaped valleys than in V-shaped valleys. The algorithm offers a fast and inexpensive tool with which to obtain valley shape information for research and management. • Proposed an automated algorithm approach to extract the valley floor width by viewing the point slope change. • The algorithm includes five steps. • The algorithm performs better in U-shaped valleys than V-shaped valleys. • The algorithm was programed as an ArcGIS plug-in for free download. [ABSTRACT FROM AUTHOR] more...

The Poiqu River basin in central Himalaya is a transboundary basin between China and Nepal that has experienced rapid glacier ice loss and glacial lake growth, some of which have drained in catastrophic glacial lake outburst floods (GLOFs). Here, we focus on the outbursts of two glacial lakes in this basin, Gongbatongsha Co in 2016, and Poiqu No.1 in 2002, and integrate multiple data sources and approaches to improve our understanding of past GLOFs and project the magnitude of potential future GLOFs. We identify their potential triggers and assess downstream damage by combining remote sensing observations and field surveys. We find that after the outbursts, Gongbatongsha Co shrank by 0.14 ± 0.003 km2 (∼91 %) in 2016 and almost disappeared, and Poiqu No.1 shrank by 0.05 ± 0.001 km2 (∼80 %) in 2002 but then expanded by 0.10 ± 0.002 km2 (∼670 %) by 2022. Our study identifies ice avalanches from the parent glaciers as the dominant trigger of the two GLOF events, and clarifies that the 2002 GLOF event stemmed from Poiqu No.1 instead of the reported Jialong Co. We also reconstructed the flow depths, velocities, and inundation areas using the hydrodynamic models HEC-RAS and FLO-2D. For Gongbatongsha Co, the models suggest that the discharge peaked at ∼550 m3s−1 about 15 min after the outburst, and the flood reached the settlement of Zhangmu with a peak flow of ∼1600 m3s−1 about 8.5 h later. The peak discharge during the GLOF from Poiqu No.1 was ∼2700 m3s−1. The flood reached the town of Nyalam 1.3 h later, with a peak discharge of ∼1100 m3s−1. The simulation of a future GLOF from Poiqu No.1 shows significant potential impacts to Nyalam town and other downstream communities due to the high flow depth. A large GLOF scenario for Poiqu No.1 would result in a peak discharge of more than 2500 m3s−1, with the flood wave reaching Nyalam in less than 40 min. We show that very high-resolution digital elevation models such as obtained from uncrewed aerial vehicles perform better in flood simulation. Our approach can be applied to potentially dangerous glacial lakes in other high mountain areas. • Ice avalanches are the dominant triggers of the two GLOF events. • Complex processes of both GLOFs involving debris flow and flow transition are reconstructed. • Future GLOF poses a significant threat to Nyalam town and other downstream communities. [ABSTRACT FROM AUTHOR] more...

The 2016 Len Small Levee breach and the decision not to repair this breach provides a unique opportunity to study the geomorphic and hydraulic changes associated with floodplain reconnection along a large (~30 km long) meander of the Mississippi River known as Dogtooth Bend. This study evaluates recent geomorphic, hydraulic, and sediment-transport capacity changes related to the breaching of the Len Small Levee and the development of cutoff channels across the neck of Dogtooth Bend. We also assess actions undertaken to mitigate further development of cutoff channels across Dogtooth Bend. To address these goals, we perform geomorphic change detection (GCD) analysis and hydrodynamic modeling to assess the geomorphic and hydraulic changes within both the Mississippi's river-connected floodplain and channel. GCD analysis using digital elevation models (DEMs) of the floodplain from pre (2011) and post (2020) levee breach showed net deposition of 23 million tons (MT) of sediment across the reconnected portion of Dogtooth Bend floodplain alone and an additional 34 MT within the batture (the land between the channel's low-water elevation and the flood-mitigation levee). Converting these deposition masses to deposition rates indicates ~5.7 MT yr−1 of deposition within the river-connected floodplain, which is equivalent to ~6 % of the average annual suspended load (~89 MT yr−1) showing this floodplain area is currently a substantial sink for river-transported sediments. In 2021, the U.S. Army Corps of Engineers constructed a grade-control structure down gradient of the levee breach to inhibit the development of cutoff channels across the neck of Dogtooth Bend. Our modeling indicates the addition of this grade-control structure could decrease peak discharge by up to ~15 % and annual flow volume by half assuming channel conveyance remains similar to 2020 conditions. However, sediment-transport-capacity modeling revealed the decrease in flow across Dogtooth Bend attributed to the grade-control structure did not translate into an increase in sediment-transport capacity within the main channel. Assessment of critical shear stress of erosion for fine-grained cohesive materials across Dogtooth Bend suggests conditions favorable to scouring along the actively forming cutoff channels even with the grade-control structure in place. These observations taken together suggest the current river management efforts may not be sufficient in preventing a meander cutoff over the long-term. [ABSTRACT FROM AUTHOR] more...

In the Central Styrian Karst (CSK, Styria, Austria) 1158 karst landforms were used to obtain a better understanding of the landscape evolution in this region. An automatically delineated doline inventory was combined with an existing cave inventory to investigate surface and subsurface karst landforms in relation to their elevation above the local base level at the transition zone between the Eastern Alps and the Pannonian Basin. The landform entities analysed consist of 51 % dolines and 49 % caves and are related to various stages of landform evolution and thus ages. The CSK was ice-free during glacial times and therefore allow for a much longer preservation of surface landforms compared to landforms that were reshaped during glaciations. Nevertheless, weathering and downwasting do re-shape and even may lead to the disappearance of surface landforms (i.e., dolines); however, subsurface landforms (i.e., caves), if accessible, might preserve information about older geomorphological stages. An old, a mature, and a young stage of landform evolution can be distinguished in the CSK and be related to planation surfaces preserved in the area, presumably older than five Ma. The chosen approach is likely applicable for other areas in the world too by implying karstification over million years' time scale. Besides those regional implications, there are local (neo-) tectonic inferences derived from the analyses that might explain some discrepancies in correlations of levels and planation surfaces, but requiring further more detailed investigations. The automatic doline delineation in the forested karst of the CSK made an area not yet mentioned in the literature become apparent. With an increasing availability of high-resolution digital elevation models, remote-sensed inventories of dolines (surface landforms) renew the question of dolines as diagnostic landforms for karstification. However, in the CSK it is revealed that an absence of dolines due to e.g., surface erosion does not indicate the absence of karstification. Therefore, landscape evolution should consider both surface (i.e., doline) and subsurface (i.e., cave) landforms. • Landscape evolution derived from 1158 landforms within the Central Styrian Karst. • Landscape evolution should consider both surface and subsurface landform inventories. • Analysis reveals new areas with surface karst features not mentioned before. • Dolines as single "diagnostic features" for karstification are deceptive. • Stages of karst landscape evolution are related to planation surfaces. [ABSTRACT FROM AUTHOR] more...

Landscapes tend to be described using some combination of mathematically- and statistically-derived morphometrics extracted from digital elevation models. For coastal barriers, these morphometrics are commonly used to characterize the response of these landscapes to sea level rise and storm activity, or to develop process-form relationships. However, it is not clear if these morphometrics, alone or in combination, are consistent with our interpretation of the landscape based on visual interpretation of structure and patterns. This study compares landscape interpretations based on commonly used morphometrics to visual interpretations made by experts and non-experts. Results suggest that what we visually perceive as landform structure and landscape pattern is not consistent with mathematically and statistically derived morphometrics, and that there is a need to evaluate whether the morphometrics we use are appropriate to characterize landforms in complex polygenetic landscapes for monitoring and management. [ABSTRACT FROM AUTHOR] more...

As escalating environmental pressures threaten the world's river systems, understanding the driving factors influencing their geomorphological changes is of critical global importance. This study illuminates the complex interaction between natural and anthropogenic factors that drove geomorphological changes along the upper Apalachicola River (UAR) from 1960 to 2010. This study utilized LiDAR point cloud data and hydrographic surveys conducted between 1960 and 2010 to identify the primary factors driving riverbed changes. A triangular irregular network (TIN) was used to convert the combined datasets from each survey, following coordinate transformation, into a 1.5 m-resolution digital elevation model (DEM) raster. The DEM of difference (DEMoD) was computed by subtracting the 1960 DEM from that of 2010, and the total sediment loss and gain were then determined by multiplying the DEMoD by the DEM resolution. A random forest (RF) regression model was used to determine the most influential factors contributing to riverbed deformation. The results revealed substantial differences in sediment loss and gain across the river. The UAR, divided into three segments, experienced sediment loss of about −6.56 × 106 m3 between 1960 and 2010, with the farthest upstream section (RM 106 to 98) losing −3.14 × 106 m3, which is ~48 % of the sediment losses in the study area. Some sections of the channel have deepened significantly, with a pronounced depth difference of −17.20 m between RM 92 and 94, potentially caused by the presence of limestone and the enlargement of a sinkhole or spring on the riverbed. The RF model identified the dam (>28 %) as the most crucial anthropogenic factor in riverbed deformation, followed by the presence of dikes (~17—18 %), then historical dredging (~7—8 %), highlighting the substantial impact of artificial structures on riverbed deformation. In contrast, rock removal, while potentially impactful in certain locations, had negligible effects (>0.5 %) at the system scale. This study highlights the interaction of natural and anthropogenic factors in river geomorphology and the potential for machine learning to identify these dynamics and inform data-driven river management and conservation strategies. • Novel examination of factors behind riverbed deformation using machine learning technique • The study reveals that the dam is the prime driving factor in riverbed deformation. • Greater impact of wing-dikes vs. dredging due to cascading effects on erosion and deposition • Rock removal found to have negligible effects at the system scale. • Anomalous elevation change suggests sinkhole or spring expansion on the riverbed. [ABSTRACT FROM AUTHOR] more...

With the availability of improved digital elevation models (DEMs) of global coverage, the morphological analysis of large populations of glacial cirques is possible, and can be used to derive important palaeoclimate and environmental information related to the distribution and history of former glaciers. In 2017, an ArcGIS toolbox, ACME (Automated Cirque Metrics Extraction), was developed to derive 16 cirque metrics based on input cirque outlines, threshold midpoints and DEMs. ACME has been widely used in cirque morphological analysis and regional comparisons. This paper presents a revised and extended toolbox, ACME2. This extended toolbox includes new functions to automatically derive cirque threshold midpoints (cirque foci) and 49 morphometric and locational variables, with attributes related to cirque location, size, shape, altitude, slope, and aspect, including variables related to the median axis, as well as 3 input metadata attributes. ACME2 also improves the methods for calculation of the hypsometric maximum and integral, and implements a new method for plan closure to be more consistent with the original definition. All ACME2 tools are coded in Python and can be imported into ArcGIS with user-friendly interfaces. Comparisons for 155 cirques in the English Lake District and 51 in the Shulaps Range, British Columbia, indicate consistency between the ACME2-derived and manually derived metrics, with most correlations r > 0.90: none <0.70. ACME2 provides more cirque metrics and automates the whole calculation sequence with cirque outlines and DEMs. Its comprehensive approach facilitates understanding of cirque form and development in all its variety. • We present an extended toolbox for automated cirque metrics extraction, ACME2. • ACME2 includes new functions to automatically derive cirque foci and 49 metrics. • A method for plan closure is developed to be consistent with earlier literature. • ACME2-derived and manually derived metrics are highly correlated in two test areas. • Tools and metrics can be used for the morphological study of other landforms. [ABSTRACT FROM AUTHOR] more...

The long-term development of fluvial landscapes is sensitive to tectonic movement. This is the case for the Three Rivers Region, located on the southeastern margin of the Tibetan Plateau, where it is critical for understanding the continuous collision and compression between the Indian and Eurasian plates. However, quantitative perspectives on this landscape evolution are lacking. Based on present global positioning system (GPS) data, a quantitative expression of two phases of regional deformation, a northeast-southwest shortening and dextral shear deformation, was proposed to represent the continuous Indian-Eurasian collision. By incorporating this tectonic pattern into a landscape evolution model and integrating the regional differential uplift, the numerical results quantitatively present a dynamic shaping of the Nu, Lancang, and Jinsha rivers in the SE Tibetan plateau margin. Analyses of the fractal dimensions of these river networks indicate that two tectonic deformation phases significantly controlled regional landscape development and its unique drainage features. The numerical simulations depict the river networks to comprise very long and relatively straight stream trunks, and relatively small and short tributaries. The tectonic shortening and its accompanying rapid uplift prevented the development and lengthening of the tributaries, which might have promoted the formation of low-relief surfaces. With comparison to the digital elevation model (DEM), the fractal features of the river networks extracted from the numerical results are consistent with those extracted from the natural river networks, despite the simplicity of the numerical model. More broadly, based on the more realistic kinematic scenarios and reasonable constraints, this study contributes to the development of an effective and applicable model that can reveal important implications for the landscape evolution of the region. • Landscape modelling of the evolution of the Three Rivers Region, SE Tibetan Plateau • Models India-Eurasia collision deformation: NE-SW shortening and dextral shearing • Results quantitatively present dynamic shaping of the Nu, Lancang, and Jinsha rivers. • River networks comprise long-straight trunks, and small-short tributaries. • Tectonic shortening-uplift prevented tributary assisting low-relief surface formation. [ABSTRACT FROM AUTHOR] more...

Abstract Potholes, or rock basins, are depressions that have been carved out of bedrock. While there has been speculation in the literature regarding the processes involved in the addition or removal of sediment in existing potholes, the processes have not been systematically documented. This study attempts to fill this knowledge gap through data collection on 50 potholes in the Navajo Sandstone located on the top of Rock Window Mesa in Chinle Valley, AZ. For spatial analysis, we obtained a high-resolution digital elevation model and detailed orthophoto of the mesa. These data allowed us to precisely measure many aspects of the potholes, which we then compared to wind data we collected to draw conclusions on how pothole morphology, catchment size, and water retention capacity affect the sediment removal processes. Wind measurements were done on 11 potholes with a range of sizes representative of the 50 potholes on the mesa. Wind speed across the top of the mesa is almost always greater than wind speed in the pothole at any given moment, and there is a robust linear relationship between the wind speed above the pothole and the wind speed in the pothole for all shapes and sizes of potholes tested. In dry conditions, the wind speed threshold for sand removal from the potholes is about 50 km/h, independent of pothole size. We observed the formation of wind eddies in the potholes which formed vortices several meters in height, and these eddies, traveling upward with a helical motion, removed the sand. We conclude that wind is an effective agent for the removal of sediment from the potholes, preventing their infill via the accumulation of sand debris brought in by the wind and spalled from the pothole sides. Highlights • Wind is an effective mechanism for sediment removal in semiarid environments. • Great pothole size does not inhibit deflation. • The wind speed over the mesa that consistently produces deflation is about 50 km/h. • Spalled bedrock from pothole walls contributes significantly to the pothole sediment. [ABSTRACT FROM AUTHOR] more...

Abstract Spatial models are an effective tool for determining potential rockfall source, transit and deposit areas. The reliability of the final rockfall modelling results depends on the quality of the input data, which is mostly based on the digital elevation model (DEM). The spatial resolution of the DEM holds key information about the main morphological properties of the surface, which is crucially important when modelling this kind of geomorphological phenomenon. Therefore, this article studies the influence of DEM spatial resolution on the modelling of rockfall source, transit and deposit areas. Modelling was carried out at five different DEM spatial resolutions available for Slovenia (1 m, 5 m, 12.5 m, 25 m and 100 m). Rockfall source areas were identified using a geomorphometric approach based on a high resolution DEM and a geographical information system. Rockfall transit and deposit areas were modelled using the Conefall computer program, which is designed to estimate potential rockfall risk areas. The area of study was the municipality of Vipava (107.4 km2) in Slovenia, EU. A spatial resolution of 1 m was chosen as a reference layer to which all modelling results of the other spatial resolutions were compared. Validation of modelling included rockfall source area comparison with orthorectified aerial images and location collection of silent witnesses (rock deposits) in the field for estimating maximum runout zones. The modelling results indicate that a spatial resolution of 1 m is the most suitable for modelling on a local scale; resolutions of 5, 12.5 and 25 m can be used for modelling on a regional scale (depending on the purpose of the modelling results); and a resolution of 100 m should not be used for rockfall modelling. Major differences between spatial resolutions can be observed when modelling rockfall source areas, i.e. in areas with the most diverse topography, while in deposit areas the observed differences are smaller due to the less rugged surface. Highlights • The influence of the spatial resolution of the digital elevation model was observed at five different spatial resolutions. • Deviations between modelling results are greater for rockfall source areas than for rockfall runout zones. • High spatial resolutions (1 m) should be used for modelling on a local scale. • Lower spatial resolutions (5 m, 12.5 m and 25 m) can be used for modelling on a regional scale. • Spatial resolution 100 m should not be used for modelling rockfalls. [ABSTRACT FROM AUTHOR] more...

Abstract Understanding dynamic earth surface processes requires various spatial and temporal information to help produce patterns of landform change. Recent developments in sensor technology such as Structure from Motion (SfM), camera-mounted airborne Unmanned Aerial Vehicles (UAVs) and Terrestrial Laser Scanning (TLS) have provided a means of acquiring high-resolution spatial data on land surface topography. Through repeat surveys, these techniques enable much better understanding of what is termed 'geomorphometry', where we can examine a geomorphic surface for change over space and time. In coastal environments, change can involve significant alteration and generation of landforms over relatively short periods and, therefore, we require a means of measuring surface morphology quickly and over large areas. Here, we examine a section of a beach-dune system in NW Ireland using SfM-UAV and TLS plus baseline dGPS data points to assess the value of these techniques and to understand their effectiveness (and limitations). Issues such as accuracy, resolution and differences of Digital Elevation Models (DEMs) are assessed for their efficiency, associated challenges and relative performance over variations in terrain types and analytical approaches. We also examine the implications for differences in areal and volume calculations of the coastal landforms using both approaches. We find that sensor performance is highly dependent on the terrain being measured, with undulations, slope, vegetation cover, acquisition resolution (point density) and interpolation issues all having pronounced impacts on effectiveness and data quality. In general, the TLS performed better over flatter, low-angled topography containing sparse/non-vegetated areas than in areas with complex landforms where survey shadows appear to compromise final DEMs. The SfM-UAV shows good performance over different terrains with the exception of relatively flat, featureless areas such as sandy beaches and densely-vegetated surfaces where differences between techniques are >1 m. Data acquisition however is much (×30) faster using a SfM-UAV with more extensive survey areas covered than using a TLS. Highlights • TLS performs better than UAV over flat beach than in vegetated dunes and vice versa. • UAV-derived point clouds 30 times faster than TLS operations • Survey design and post-processing methodology important in reducing DSM errors • 3D surface derivation should take cognisance of terrain complexity and type. [ABSTRACT FROM AUTHOR] more...

Abstract Identification and characterization of a relict landscape in the Black Hills of South Dakota has provided insight into the postuplift history (~30 Ma to present). A new watershed decomposition technique has been developed that utilizes high-resolution digital elevation models and traditional long valley profiles to identify the location and extent of the relict landscape as well as its geomorphic characteristics. Results identified an expansive relict landscape at elevation in the center of the Black Hills that contains fluvially mature features such as low-gradient channels and broad flood valleys. Moreover, the relict landscape and associated watersheds that drain it are undergoing active fluvial incision via knickzone migration. This observation suggested that the Black Hills were once much more subdued than today. At present, channel confinement, lack of potential floodwater storage, and steepened stream gradients exists in reaches of active incision downstream of the relict landscape. Large paleofloods influenced by these processes have been well documented and have been restricted to the narrow and steep canyons that drain the relict landscape. Therefore, active fluvial incision into the Black Hills influences the ability of more recent (Holocene) large floods to leave substantial evidence of their occurrence inside incised canyon walls and should also be considered when studying watershed factors influencing large flood events on the flanks of the Black Hills. Graphical abstract Unlabelled Image Highlights • Topography is in a transient state of adjustment to ~250 m of stream incision. • Knickzone migration has preserved expansive relict and intermediate landscapes. • Some Tertiary deposits are associated with relict and intermediate landscapes. • Fluvial incision influences the occurrence of high-magnitude low-frequency floods. [ABSTRACT FROM AUTHOR] more...

Abstract Detection of 100-year floodplains is one of the major tasks in flood risk management. In recent years, a variety of DEM-based methods have been developed for preliminary estimations of 100-year floodplains over large regions. The higher efficiency of these methods for large-scale problems and data-scarce regions compared to the conventional hydrodynamic methods is a big advantage. However, unlike considerable advances in the field of probabilistic mapping by hydrodynamic models, these methods are mostly deterministic and cannot provide a probabilistic presentation of the floodplains. In this study, a new method is proposed to combine both advantages of probabilistic mapping compared to deterministic ones and DEM-based methods against conventional models. This method includes a probabilistic function, which uses a morphologic feature, Height Above Nearest Drainage (HAND), as the independent variable. HAND is defined as the difference in elevation between a given point and the nearest stream based on the flow direction and can be calculated from a Digital Elevation Model (DEM). The parameters of the probabilistic function are determined by using a heuristic optimization algorithm named Particle Swarm Optimization (PSO) by minimizing the error of a predicted 100-year floodplain map compared to a reference map. The results illustrate that a linear function with one parameter is an appropriate function for the study site. In addition, a comparison of the proposed method with its deterministic version demonstrates the higher effectiveness and reliability of the proposed probabilistic method for a flat watershed where the overpredictions and underpredictions generated by a deterministic threshold method are reduced. Highlights • This model contains both advantages of probabilistic and low-complexity methods. • Rise in accuracy compared to the deterministic version is shown for a flat area. • A linear function is a proper choice for probabilistic flood mapping in this basin. • The uncertainty of model parameter, TrH , is considered by estimating its PDF. [ABSTRACT FROM AUTHOR] more...

Abstract Surface roughness is a term used in fluvial research without a unanimous definition. Clarification of the term and improved parameterisation is needed in future research. Improvements to the collection of topographic data, using photogrammetry, have provided accurate digital elevation models (DEMs) of field and laboratory gravel-bed patches of varied sediment size and surface structure. In this study, a moving-window process is used for analysing spatial variability within DEMs. Using this information, and in unison, the effect of DEM size and grid spacing are considered on an extensive range of roughness parameters, in order to provide insights for obtaining grain-roughness statistics. It is shown that DEM size influences the calculated roughness statistics, and the observation of plateaus in statistics for DEM window sizes above 16 × D 50A in both directions (where D 50A is the median grain size of the bed-surface material) suggests this as a minimum DEM size for grain-scale roughness analysis. Further, the DEM grid spacing should be 1 mm or below, in order to adequately capture grain roughness, as coarser resolutions failed to detect particle imbrication. Finally, variability in roughness parameters was evident due to natural spatial variation in gravel-bed microtopography, suggesting using a single roughness parameter is not appropriate to holistically describe the roughness of a gravel patch. As the importance of topographic information continues to grow in geomorphology, the results of this study will assist researchers in the collection and subsequent analysis of DEMs. Graphical abstract Unlabelled Image Highlights • Facilitates the improvement of understanding the analysis of topographic data • A single roughness parameter is inadequate for describing patch-scale roughness. • A DEM size exceeding 16 × D 50A in both directions is appropriate to characterise grain-roughness. • Grid spacing should reflect the scale of research. • This analysis can be used on a variety of applications using topographic data. [ABSTRACT FROM AUTHOR] more...