Geomorphic Mapping Research Articles

Sediment Source Partitioning and Budgeting Over Historical Timescales in a Glacierized, Mountain Catchment

AbstractManaging and living with geohazards is especially challenging in mountain landscapes and requires an understanding of catchment‐scale sediment dynamics and internal system functioning. While sediment budgeting is a valuable framework, challenges remain including partitioning sediment yield by source and grain size and addressing scale issues. This study advances our understanding of bed material dynamics in glacierized mountain catchments by applying a range of complementary techniques to measure sediment transfers in the Fitzsimmons Creek watershed. First, we measured the historical bed material yield using field surveys and historical air photo analysis, revealing an average specific sediment yield of 210 Mg km−2 yr−1, that varied by a factor of 17 over the 76‐year record. Hydro‐meteorological and historical analyses suggest that gravel extraction had the largest impact over the past three decades, while an extreme landslide and flood event produced the highest recorded sediment yield. Second, we constructed a detailed sediment budget along the river system using high‐resolution, multi‐temporal lidar and geomorphic mapping data. Sediment source partitioning indicates that landslide, active channel, and floodplain sources each contributed about one‐third of the total sediment supply. Net degradation occurred along the valley bottom upstream of the fan‐delta, resulting in steadily increasing downstream sediment yield. This trend is punctuated by chronic landsliding near the outlet, driven by postglacial incision through glaciogenic sediments at a hanging valley step. Contemporary glacial and proglacial sources were not measured directly but surprisingly contributed minimally. These findings provide insight into the sediment dynamics of glacierized mountain catchments and their potential controls.

Climatically-driven development of late Quaternary fluvial geomorphology in the arid inland of Asia

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

Analysing the impacts of extreme torrential events using multi‐temporal LiDAR datasets—The Schöttlbach catchment, Upper Styria, Austria

AbstractExtreme precipitation events in small alpine catchments trigger hazardous hydro‐geomorphic processes that cause considerable damage to settlements and infrastructure. In summer 2011 and 2017, two flood events mobilizing large amounts of sediments struck the town of Oberwölz (Styria, Austria) located at the outlet of the Schöttlbach catchment. We used data from local weather stations and precipitation radar to analyse the meteorological settings that caused the flooding. We compiled a consistent sediment budget for the 2017 event by combining geomorphic mapping, connectivity analysis, high‐resolution airborne LiDAR (ALS) and uncrewed aerial vehicle (UAV)‐borne LiDAR (ULS), data from other authors for the 2011 event and external information (e.g., event analysis and excavation data). The 2017 event mobilized higher sediment volumes than the 2011 event (131 000 m3 vs 90 000 m3) even though 24‐h precipitation and peak discharges were lower in 2017. First assumptions that the larger sediment output was caused by the reworking of the 2011 flood deposits proved to be incorrect. The impacts of the 2011 event affected the resilience of the geomorphic system resulting in a significantly higher hillslope sediment supply. We conclude that sediment transport in alpine catchments can increase disproportionately when recurrence intervals fall below a critical level.

Evaluating the accuracy of binary classifiers for geomorphic applications

Abstract. Increased access to high-resolution topography has revolutionized our ability to map out fine-scale topographic features at watershed to landscape scales. As our “vision” of the land surface has improved, so has the need for more robust quantification of the accuracy of the geomorphic maps we derive from these data. One broad class of mapping challenges is that of binary classification whereby remote sensing data are used to identify the presence or absence of a given feature. Fortunately, there is a large suite of metrics developed in the data sciences well suited to quantifying the pixel-level accuracy of binary classifiers. This analysis focuses on how these metrics perform when there is a need to quantify how the number and extent of landforms are expected to vary as a function of the environmental forcing (e.g., due to climate, ecology, material property, erosion rate). Results from a suite of synthetic surfaces show how the most widely used pixel-level accuracy metric, the F1 score, is particularly poorly suited to quantifying accuracy for this kind of application. Well-known biases to imbalanced data are exacerbated by methodological strategies that calibrate and validate classifiers across settings where feature abundances vary. The Matthews correlation coefficient largely removes this bias over a wide range of feature abundances such that the sensitivity of accuracy scores to geomorphic setting instead embeds information about the size and shape of features and the type of error. If error is random, the Matthews correlation coefficient is insensitive to feature size and shape, though preferential modification of the dominant class can limit the domain over which scores can be compared. If the error is systematic (e.g., due to co-registration error between remote sensing datasets), this metric shows strong sensitivity to feature size and shape such that smaller features with more complex boundaries induce more classification error. Future studies should build on this analysis by interrogating how pixel-level accuracy metrics respond to different kinds of feature distributions indicative of different types of surface processes.

Hydrogeomorphological approach for flood analyses at high- detailed scale: Narrow rivers with broad complex alluvial plains

Fluvial flood risk management requires precise knowledge of flooding processes; thus, there is a need to carry out a detailed hydrological, hydraulic, and geomorphologic analysis to understand floods and the factors that influence them. Although the integration of geomorphological methods and hydrological-hydraulic modelling is known to be crucial for flood risk analysis, it remains a challenge to apply these approaches to the understanding of floods in small and medium-sized catchments, focusing on complex fluvial systems that have been highly modified. In this work, a hydrogeomorphological methodology was developed to analyse fluvial floods in narrow rivers with broad complex alluvial plains. The procedure comprises different phases that combine hydrologic-hydraulic modelling and a geomorphological break-down. Critically, this allows for a detailed analysis of existing relationships among erosional and depositional fluvial landforms and hydraulic parameters, comprising geometric sections, discharges, depths, flood extents and, therefore, flood hazards. The approach involves the analysis of specific flood events beforehand and the study of fluvial floods associated with different probabilities of occurrence afterwards. The information employed in the present study incorporates high- detailed inputs comprising hourly time series of hydrometeorological data, LiDAR data to extract high-precision terrain information, fluvial geomorphic maps and flood event extents based on Sentinel-2 imagery. We demonstrate this methodology in the Carrión River, located in the province of Palencia, Spain, whose characteristics include a wide complex alluvial plain, reaches highly modified by anthropic interventions and recurrent flood episodes. This hydrogeomorphological approach allowed the integration of geomorphological knowledge and hydrologic-hydraulic modelling in flood analysis. As a result, it led to a deeper comprehension of the processes of inundation, which would be challenging to thoroughly understand without incorporating a holistic method, an essential factor for defining effective flood management strategies.

Tree parameter extraction method based on new remote sensing technology and terrestrial laser scanning technology

Ground LiDAR is a terrestrial LiDAR system that is often used for terrain and geomorphic mapping. Ground-based LiDAR can be used to collect more local and short-range data, making it ideal for mapping smaller areas with high precision. In order to solve the rapid extraction of tree parameters in the national public welfare forest survey, the ground-based LIDAR was used to obtain the point cloud of trees, and the point cloud data was registered, denoised, normalized, sliced, parameter extracted, etc., and the parameters of individual trees in the forest were obtained. The Bland-Altman consistency test is used to test whether the method of extracting tree parameters from point clouds is consistent with the traditional measurement method. The experimental results show that the point cloud data obtained by the ground-based LIDAR can quickly, conveniently and accurately extract the tree parameters, which is consistent with the traditional tree parameter extraction method, and has the advantages than the traditional tree parameter measurement, such as point cloud, image and traceability. It has a unique advantage in establishing a tree database. It is suggested that LIDAR should be used for forest survey in the future.

Geomorphic Imprints of Active Tectonics of the Bikaner-Nagaur Petroliferous Rift Basin and its Surroundings (Western Rajasthan, India)

Abstract Geology of sedimentary rift-basins require strong geomorphic input for a proper interpretation of active tectonics. Rift-related sedimentation took place in western Rajasthan of the Indian shield, which includes the Bikaner-Nagaur basin (BNB) and a few other adjacent basins. The sedimentation history of the BNB includes Proterozoic, Cambrian, Permo-Carboniferous and from Paleocene to the Recent. This study analyses river profiles with the best-fit curve (R2) model for the BNB and the surrounding regions. The research shows that the watershed 3 within the study area is most active tectonically, through which multiple faults and lineaments pass. Hypsometric Curves (HCs) of watersheds 1, 2 and 3 indicate that these watersheds are tectonically active. This inference is based on the concave profiles of HCs at the head, and convex profiles of HCs at the body and toe sections. Clustering of sixty segments (S) of the considered rivers based on linear-scale morphometric parameters, e.g., sinuosity index (SI), stream length gradient index (SL) and concavity (θ) enabled segment-wise comparison of river profiles with similar values. These segments were compared pair-wise, and Euclidean-based dissimilarity (dR) values were calculated between each such pair. The findings too imply that tectonic activeness exists in parts of watersheds 1, 2 and 3. The channel flow lines are controlled by faults/lineaments as per the micro-scale examination of the drainage network and faults/ lineaments analysis. Under structural control, nine major geomorphic units emerged with distinct erosional surfaces, denudational hillocks, dissected hills and inselbergs. Detailed geomorphic map with micro-scale studies revealed a slope retreat process that resulted in landforms viz., pediment, pediment slope and active flood plains.

Investigation of site fundamental frequency using H/V method guided by geomorphic features derived from old aerial photos

The fundamental frequency of soil (non-lithified cover on the bedrock) is one of the most important factors in seismic hazard evaluations. On the other hand, this frequency expresses several factors such as the clast size, sorting, and the degree of compaction and cementation of soil, which is in close relationship with both the geomorphic setting and processes responsible for the soil formation. We present a rapid and cost-effective multi-disciplinary approach to study site effect in developing urban areas using the spatial correlation between geomorphic setting of soil units and their fundamental frequencies. As a case study, the city of Zanjan was selected because like many other cities of developing countries has been expanded drastically during the last half-century. We use old aerial photos (produced in 1966) of Zanjan and its surroundings to reconstruct a unified orthophoto-mosaic of the study area. This orthophoto-mosaic exhibits pristine geomorphic landforms and features, which predate the current urban coverage of the city, and provides an excellent possibility for mapping Quaternary geological units with distinct geomorphic settings and soil characteristics. Besides, the site effect is measured through the H/V spectral ratio method at 91 points along the profiles pre-designed based on our geomorphic mapping. Subsequently, the spatial pattern described in the geomorphic map was compared with the site effect values. This comparison shows a general correlation between the geomorphic setting of alluvia and the corresponding fundamental frequencies of the soil such that the closer to the mountain front, the higher the fundamental frequency. The results indicate that the peak frequency is observed in the northern regions of the city where a relatively thin layer of unsorted coarse-grained alluvium overlies the bedrock. In the southern geomorphic depressions close to the Zanjanrood river and behind the East-dipping North Zanjan reverse fault (east of the city), where a pile of fine-grained deposits is found, the fundamental frequency reaches its lowest values, namely less than 1 Hz. A comparison of the soil frequency map with the map of shear-wave velocities provided by geotechnical borehole data also indicates a meaningful correlation. Our approach provides a twofold benefit by (1) reducing both the time consumption and expenses in site effect studies through an optimal design of H/V measurement points and borehole drillings based on a precise mapping of distinct geomorphic units, and (2) proposing a unique possibility to produce a reliable site effect map in the urban areas developed during the last half-century.

High-Accuracy Mapping of Soil Parent Material Types in Hilly Areas at the County Scale Using Machine Learning Algorithms

Conventional maps of soil parent material (SPM) types obtained by field survey and manual mapping or predictions from other map data have limited accuracy. Digital soil mapping of SPM types necessitates accurate acquisition of SPM distribution information, which is still a challenge in hilly areas. This study developed a high-accuracy method for SPM identification in hilly areas at the county scale. Based on geographic information system technology, seven feature variables were extracted from the geological map, geomorphic map, digital elevation model, and remote sensing image data of Shanggao County, Jiangxi Province, China. Different feature combination schemes were designed to develop SPM identification models based on random forest (RF), support vector machine (SVM), and maximum likelihood classification (MLC) algorithms. The best SPM identification results were obtained from the RF algorithm using the combination of geological type, geomorphic type, elevation, and slope. Confusion matrices were constructed based on a field survey of 586 validation samples, and the results were evaluated in terms of overall accuracy, precision, recall, F1 score, and Kappa coefficient. The overall accuracy and Kappa coefficient of the results from the optimal RF model were 83.11% and 0.79, respectively, which were 26.11% and 0.31 higher than those of the conventional map, respectively. Its precision and recall for various SPM types were greater than 75%. A comprehensive comparison of the accuracy, uncertainty, and plotting performance of the SPM recognition results reveals that the RF algorithm outperforms the SVM algorithm and the MLC algorithm. Geological type was the largest contributor to SPM identification, followed by geomorphic type, elevation, and slope. The importance of different feature variables varied for distinct SPM types. The accuracy of SPM identification was not improved by selecting more feature variables, such as land use type, normalised difference vegetation index, and topographic wetness index. This study demonstrates the feasibility of high-accuracy county-level SPM mapping in hilly areas based on the RF algorithm using geological type, geomorphic type, elevation, and slope as feature variables. As hilly areas have typical topographic features and SPM types, the proposed method of SPM mapping can be useful for application in other similar areas. There are a few limitations in this study with regard to data quality and resolution, feature variable selection, classification algorithm generalisation, and study area representativeness, which may affect the outcomes and need to be solved.

Deciphering Complex Morphology and Structural Connectivity of High-Magnitude Deep-Seated Landslides via Airborne Laser Scanning: A Case Study in the Vrancea Seismic Region, Romanian Carpathians

In the Vrancea seismic region (Romanian Carpathians; the most important intermediate-depth seismic source of Europe), the morphology of the slopes is often marked by the existence of numerous high-magnitude, deep-seated active, dormant or relict landslides, which are the subjects of many cases of functional and structural connectivity. Due to the compact and extensive (coniferous and broad leaved) forest coverage and because of the lack of publicly available regional high-resolution DEMs, it is usually difficult to fully understand the morphogenetic framework of such large, deep-seated landslides in order to assess their frequency–magnitude relationship, a key issue in hazard quantification. However, the high impact of such landslides on river networks requires an in-depth understanding of the multi-hazard framework, as cascading effects are likely to affect the presently growing human activities developing along the valleys. Within a case study represented by a 2.5 km long deep-seated landslide, that caused a 500 m lateral occlusion of Buzău River, we used integrated remote sensing technologies (UAV laser scanning) and in situ (geomorphic mapping and ERT investigations) techniques, which allowed us to better understand the structural connectivity which conditions the landslide hazard in such complex morphogenetic conditions, outlining the present potential of the regional seismo-climatic context to trigger potential high-magnitude chain effects.

Supervised Geomorphic Mapping of Himalayan Rivers Based on Sentinel-2 Data

The Himalayan region is a hotspot in terms of expected future hydrological and geomorphological variations induced by climate change on proglacial areas and the related implications for human societies established along the downstream rivers. Due to the remoteness of the proglacial zones in the Himalayas and the associated logistical problems in carrying out traditional field and UAV-based morphological monitoring activities, remote sensing here plays a crucial role to monitor past and current fluvial dynamics, which could be used to anticipate future changes; however, there has been, so far, limited research on morphological changes in Himalayan proglacial rivers. To address this gap, a morphological classification model was designed to classify recent changes in Himalayan proglacial rivers using the Google Earth Engine platform. The model is the first of its kind developed for the Himalayan region and uses multispectral S-2 satellite data to delineate submerged water channels, vegetated surfaces, and emerged, unvegetated sediment bars, and then to track their variations over time. The study focused on three training sites: Langtang-Khola (Nepal), Saltoro (Pakistan), and Nubra (Jammu and Kashmir) rivers, and one testing site, the Ganga-Bhagirathi River (India). A total of 900 polygons were used as training samples for the random forest classifier, which were further divided into 70% calibration and 30% validation datasets for the training sites, and a separate validation dataset was acquired from the testing site to assess the model performance. The model achieved high accuracy, with an average overall accuracy of 96% and a kappa index of 0.94, indicating the reliability of the S2 data for modeling proglacial geomorphic features in the Himalayan region. Therefore, this study provides a reliable tool to detect past and current morphological changes occurring in the Himalayan proglacial rivers, which will be of great value for both research and river management purposes.

Regional flood occurrence in the culmination zone of medium-high mountain ranges by tree-ring based reconstruction: Frequency, triggers, dynamics

Floods are among the most dangerous geohazards in Central Europe. Their occurrence is often the result of the cumulative contribution of sub-catchments in the culmination zone of a mountain range, which subsequently has a devastating effect in the foreland. However, data on discharges from gauging stations are mostly missing from these sites (high-gradient streams), which are crucial to understanding the origin of floods in low-lying populated areas where they can cause significant damage. Therefore, this study focuses on an extensive reconstruction of flood events in 13 sub-catchments in the culmination zone of the Orlicke hory Mts. Flood events were reconstructed using dendrogeomorphic approaches, currently the most accurate absolute dating method. The analysis revealed 111 floods in all sub-catchments during the 34 to 84 year period by dating 844 growth disturbances in a tree-ring series of 632 trees (Picea abies (L.) Karst.) damaged during the floods. Regional reconstruction across the mountain range revealed events of regional and local significance, with no direct link between event magnitude and areal extent. This is consistent with the two dominant rainfall patterns identified that likely triggered the floods (short-term extreme rainfall and medium-term above-average rainfall). In particular, however, the study revealed several patterns of spatial transformation of flood events from source sub-catchments to their form captured at gauging stations in the foreland. The combination of various lines of evidence (geomorphic mapping, growth disturbance patterns, spatial pattern of flooding) suggests a limited erosional effect of most of the reconstructed events. The findings thus shed new light on the overall dynamics of floods in the mountain massif and their impact on flood discharges in the foreland.

Evidence for a prehistoric multifault rupture along the southern Calico fault system, Eastern California Shear Zone, USA

Abstract Geomorphic mapping and paleoseismologic data reveal evidence for a late Holocene multifault surface rupture along the Calico-Hidalgo fault system of the southern Eastern California Shear Zone (ECSZ). We have identified ~18 km of continuous surface rupture along the combined Calico and Hidalgo faults in the vicinity of Hidalgo Mountain in the southern Mojave Desert. Based on the freshness of geomorphic fault features and continuity of surface expression, we interpret this feature to reflect a simultaneous paleorupture of both faults. Displacement along the paleorupture is defined by 39 field measurements to be generally pure right-slip with a mean offset of 2.3 m. Scaling relationships for this offset amount imply that the original surface rupture length may have been ~82 km (corresponding to a M7.4 earthquake) and that much of the rupture trace was erased by subsequent erosion of sandy and unconsolidated valley alluvium. Eight luminescence ages from a paleoseismic trench across the paleorupture on the Hidalgo fault bracket the timing of the most recent rupture to 0.9–1.7 ka and a possible penultimate event at 5.5–6.6 ka. This timing is generally consistent with the known earthquake clusters in the southern ECSZ based on previous paleoseismic investigations. The ages of these earthquakes also overlap with the age brackets of the most recent events on the Calico fault 42 km to the north and the Mesquite Lake fault 40 km to the south from earlier work. Based on these age constraints and the expected surface rupture length, we propose that the Calico fault system experienced a major, multifault rupture that spanned the entire length of the fault system between the historical Landers and Hector Mine ruptures but preceded these events by ~1–2 k.y. Coulomb stress change modeling shows that the Calico paleorupture may have delayed the occurrence of the Landers-Hector Mine cluster by placing their respective faults in stress shadows and may have also prevented a triggered event from occurring on the Calico fault following the historic events. This work implies that closely spaced ruptures in complex shear zones may repel each other and thereby stretch out the duration of major earthquake clusters. These results also suggest that complex multifault ruptures in the ECSZ may not follow simple, repeatable patterns.

Fluvial response to Late Pleistocene–Holocene climate change in the Colorado River drainage, central Texas, USA

Abstract We documented the impact of Late Pleistocene–Holocene climate change on terrace deposits and preserved channels in the unglaciated drainage of the Colorado River in central Texas (south-central United States) using integrated channel morphology and provenance analysis. Detrital zircon (DZ) U-Pb ages (n = 1850) from fluvial terrace deposits and new quantitative analysis of fluvial channel morphology based on LiDAR data were used to reconstruct sediment provenance and shifts in paleohydraulic conditions during Late Pleistocene to Holocene aridification. These data reveal a reduction in fluvial channel size and discharge temporally coupled with a rapid shift in erosion locus and dominant sediment sourcing, from the Southern Rocky Mountains to the Llano area, during the glacial-interglacial transition. Geomorphic mapping and morphometric analysis show narrowing of river channels linked to diminishing Colorado River discharge. DZ data show an abrupt shift to erosion in the lower drainage basin and the remobilization of older terraces due to river incision and lateral channel migration. We attribute these systematic changes to upper-basin contraction caused by drainage reorganization and aridification during the Late Pleistocene, as well as the onset of enhanced convective precipitation sourced from the Gulf of Mexico, driving focused erosion along the topographic edge of the Llano uplift in central Texas since the early to mid-Holocene.

Simplified engineering geomorphic unit-based seismic site characterization of the detailed area plan of Dhaka city, Bangladesh

Severe failure of improperly designed and poorly constructed structures may occur due to the amplified and prolonged ground motion during an earthquake, and hence prediction of the ground motion characteristics at the soil surface is crucial. In this study, based on the prepared simplified engineering geomorphic map, we performed a one-dimensional (1D) nonlinear site response analysis for seismic site characterization of the recently proposed Detailed Area Plan (DAP) area of Dhaka City, the Capital of Bangladesh. The engineering geomorphic unit-based map was prepared from image analysis and verified with the collected borehole data and surface geology map. The study area was classified into three major geomorphic units and seven sub-units subject to the subsurface soil profiles. Nine earthquake time histories, seven from the PEER NGA WEST2 data set and two synthetics, and seven identified subsurface soil profiles were used for nonlinear site response analysis, along with the BNBC 2020 uniform hazard spectrum as the target spectrum. For the selected earthquake ground motions, the near-surface soil response of the DAP area showed de-amplification of acceleration in the short period and amplification of acceleration in the long period. The amplified long-period acceleration could cause severe damage in inappropriately designed and poorly constructed long-period structures. The outcome of this study could be used to prepare a seismic risk-sensitive land use plan for the future development of the DAP of Dhaka City.

Geomorphic mapping and analysis of neotectonic structures in the piedmont alluvial zone of Haryana state, NW-India: a remote-sensing and GPR based approach

The Himalayan Frontal Thrust (HFT) and the surrounding piedmont alluvial region represent a zone of active deformation in the Indo-Gangetic plains. We investigated the Piedmont zone between the Ghaggar and Yamuna River basins in Haryana, India, for geomorphic signatures of active tectonics using remotely sensed data and validated by Geophysical Ground Penetrating Radar (GPR) surveys. The possible locations and the types of active tectonic features such as sub-surface fault, ridges, lineaments and warps were identified based on the presence of geomorphic signatures such as drainage gradient anomalies, abrupt change in flow direction, river offset, compressed meanders, paleochannels and topographic breaks. We used various optical satellite imageries to detect and map the temporal changes in the flow pattern of rivers in the study area. GPR investigations were done at selected test sites to locate and verify the continuity of subsurface fault. The GPR profiles were taken in the North-South direction using the common midpoint technique with 40 and 100 MHz antennae. Low frequency bi-static GPR scanning confirmed a number of dipping reflectors due to fault planes and warp surfaces in the study area. It is concluded that the piedmont zone of Haryana is actively deforming and could become a future seismic hazard zone.

Surface deformation and damage of 2022 (M6.8) Luding earthquake in China and its tectonic implications

AbstractThe 2022 (M6.8) Luding earthquake on the Xianshuihe Fault Zone (XFZ) caused severe casualties and property losses, and surface deformation and damage of which is crucial for studying the earthquake hazard assessment. However, few intensive scientific understanding has obtained to date because of widespread coronavirus transmission, strong vegetation coverage, and post-earthquake paralyzed traffic. By integrating high-resolution satellite images, large-scale geomorphic mapping, and UAV surveys, we constrain coseismic fractures and ruptures along an NW-SE-trending surface deformation zone, with discontinuous geomorphic scarps,en echeloncracks, and bulges concentrated in the areas of Yanzigou, Moxi, Menghugang, and Xingfu villages near the epicenter. Field observation also shows that the zone extends nearly parallel to the pre-existing XFZ with a length of ∼35 km with variable widths and a maximum vertical displacement of ∼100 ± 10 cm. The earthquake-induced surface coseismic effects, such as landslides, rock falls, and collapses, caused damage to the area. The amplification effect of the topography and the improper aseismic design and poor constructions may be responsible for the spatial distribution of MM Intensity IX, which is larger than other previous earthquakes that occurred in the surrounding area with a similar tectonic setting.

Late Quaternary fluvial and aeolian depositional environments for the western Red River, Southern Great Plains, USA

AbstractUbiquitous Holocene dune systems are associated with major west-to-east flowing rivers across the Southern Great Plains (SGP), USA. Critical questions remain as to whether aeolian activity reflects multiple environmental signatures, including increased sand supply from riverine sources. This research focused on the western Red River where geomorphic mapping revealed three terrace levels up to 16 m, buried partially by up to 10 m of aeolian sediments. Pedosedimentary facies analyses of sections and Geoprobe cores extracted from terraces and close-interval optically stimulated luminescence dating of quartz grains revealed two periods of fluvial aggradation at ca. 80 ka to ~5 to 8 m above the Red River forming the Vernon terrace, and at 30 to 13 ka to ~20–15 m, the highest identified Childress terrace. Net degradation of 20 m also occurred between 13 and 7 ka to 4 m below the current channel, reflecting regional fall in the groundwater level. The latest aggradation event, which built the lowest Luna terrace at ~2 m, ended 1.5 to 0.7 ka and was partially buried by fluvial-sourced dunes in the sixteenth and seventeenth centuries. This recent phase of aeolian deposition coincides with a comparatively wet period in the central United States during the Little Ice Age, rather than with regional drying.

Morphometry and evolution of sinkholes on the western shore of the Dead Sea. Implications for susceptibility assessment

Sinkhole development is a hazardous geomorphic process responsible for increasing economic losses worldwide. The highly dynamic eogenetic salt karst of the Dead Sea is one of the most striking examples of a human-enhanced sinkhole hazard. Since the 1980s, the shores of the Dead Sea have been affected by thousands of sinkholes while the lake level has been declining. Sinkholes pose a major threat, but their rapid development also offers an exceptional opportunity to study their evolution. Although the evolution of the morphometry and distribution of sinkholes provides essential data for hazard assessment, this kind of studies are almost lacking because of the typical slowness of the processes. Here we present multi-temporal cartographic sinkhole inventories of a sector in the western shore of the Dead Sea. The database was constructed using aerial and satellite imagery, high-resolution three-dimensional photogrammetric models, and fieldwork. Most of the depressions mapped were single, small, relatively shallow, subcircular, collapse sinkholes nested within large sagging basins. From 2005 to 2021, the 702 new sinkholes have been concentrated along a narrow N-S-oriented strip comprising tightly packed alignments and clusters. Sinkhole expansion by mass wasting and coalescence play an essential role in the evolution of the sinkhole landscape. An average subsidence rate of 45 cm/year has been calculated for the total area affected by sinkholes, providing an indirect estimate for the rate of subsurface salt dissolution. This research illustrates how multi-temporal geomorphic mapping and morphometric analyses provide an objective basis for the development of reliable spatial predictions for sinkhole evolution.

Glacial geomorphology between the Gran Campo Nevado and Estrecho de Magallanes, Chile (52–53°S, 73°W)

ABSTRACT We present the first extensive high-resolution glacial geomorphic map west of the Andean Cordillera in southernmost Chile (52.8–53.1°S, 73.0–73.9°W). The map extends over 1565 km2 and is based on high-resolution satellite images and aerial photographs. At selected locations, the remotely mapped geomorphology was corroborated by field observations. The study area is dominated by glacial erosional landforms (77%) over depositional landforms (23%), with published submarine depositional landforms having been included (e.g. moraines). Glacial drift, kettle kame topography and lateral and frontal moraines form the primary depositional landforms and sediment associations. Glacial cirques, wide U-shaped valleys, whalebacks, roches moutonnées and scoured bedrock characterize most of the mapped area. The spatial distribution of whalebacks and roches moutonnées in the study area indicates a lack of lithological control on their formation and a warm-based, dynamic ice velocity and thickness regime during Patagonian Ice Sheet cover and retreat during the last glacial cycle.