ABSTRACT Murtoos and murtooized terrains are new types of subglacial landforms found in the Fennoscandian Ice Sheet (FIS) and Cordilleran Ice Sheet (CIS) regions. LiDAR‐based morphometric analyses have revealed substantial morphometric diversity among murtoos and murtoo‐related landforms, while sedimentological excavations have documented a wide range of architectural elements and lithological characteristics. Most importantly, murtoos are predominately composed of silt/clay‐poor, sandy and gravelly diamictons interbedded with sorted patches of sandy and gravelly sediments. There are two prevailing hypotheses, both suggesting that murtoo formation is related to subglacial flooding episodes during deglaciation. In the FIS region, murtoo genesis has been suggested to be dominated by sediment‐concentrated flows and flooding‐induced sediment transport and liquefaction, and murtoos are considered as depositional landforms. In the CIS region, murtooized terrains are suggested to be formed by subglacial compressional deformation (glaciotectonism), as a consequence of glacial dynamic reorganization and ice flow. In the present study, we analyse and compare the sediment composition and architecture of two morphometrically similar triangular‐shaped murtoos in the FIS region in Finland, located in two different settings. The results demonstrate that murtoo internal structures vary considerably, and these variations cannot be inferred from morphometric characteristics alone. Murtoos may contain different sediment types depending on their depositional environment. They may include a high proportion of sandy to gravelly glaciofluvial sediments with upper‐flow regime (UFR) and lower‐flow regime (LFR) bedforms within their main interior, or they may consist predominately of crudely stratified sandy to gravelly diamicton deposited by subglacial slurries and forming the main sediment type of the murtoo body. The results also indicate that murtoo composition and sediment architecture are dependent on the magnitude of subglacial flooding, which largely relates to their spatial association with subglacial meltwater corridors (SMC). Neither one of the presently studied murtoos exhibits significant features of glaciotectonism, reported from the CIS region. Consequently, murtoos and murtooized terrains may represent equifinal subglacial landforms, and their interpretation requires a combination of regional geomorphological mapping and sedimentological analysis.
ABSTRACT The completion of the Five‐hundred‐metre Aperture Spherical radio Telescope (FAST) has demonstrated the advantages of utilizing large natural depressions for astronomical facility siting in karst regions. However, efficiently and automatically identifying terrain‐morphological candidates for FAST‐type installations remains challenging in geomorphological and geospatial analyses, especially in highly fragmented and scale‐variable karst terrains. In this study, we develop an AI‐oriented, knowledge‐guided DEM‐based framework that integrates multi‐scale spherical‐cap template matching with multidimensional computer‐vision similarity assessment. Spherical‐cap DEM templates at multiple scales are matched to real terrain using a sliding‐window scheme and similarity is quantified using Pearson correlation, structural similarity index measure (SSIM) and mutual information (MI). Depth thresholds, area–depth ratios and local‐minima conditions, combined with spatial clustering, are applied to extract representative depressions. When applied to a typical karst region in Southwest China, the method identified 245 depressions with composite matching scores above 0.70, which cluster at mid‐elevations (800–1500 m) and show strong spatial associations with regional fault zones. High‐scoring depressions generally exhibit high circularity, low edge‐relief variability and geometrically regular outlines, indicating favourable terrain‐morphological conditions for preliminary FAST‐type candidate screening. Further analyses suggest potential linkages among depression size, morphometric attributes, lithological assemblages, structural setting and hydrogeomorphic evolution. Overall, this study provides an efficient, interpretable and transferable DEM‐based workflow for terrain‐based preliminary screening of FAST‐type karst depressions. The identified depressions should be regarded as geomorphological candidates rather than final engineering sites, because practical FAST‐type site selection also requires further evaluation of geological stability, transportation accessibility, meteorological conditions, hydrological safety, electromagnetic environment and construction feasibility.
ABSTRACT The particle shape is an important factor affecting the rotational and translational speeds of sand particles, but the relationship between particle shape and speed is still unclear. The high‐resolution and high‐speed camera technology (31.6 μm/pixel and 10 000 frames/s) is applied in a wind tunnel to study the characteristics of rotational and translational motion of particles with different shapes. The results show that with increasing circularity, the mean rotational speed decreases for smaller particles less than 0.4 mm in diameter and increases for larger particles more than 0.4 mm in diameter, whereas the mean translational speed usually increases for all particles, clockwise and counterclockwise rotational particles. At the same circularity, the mean rotational speed and proportion of clockwise rotation are higher than those of counterclockwise rotation, whereas the mean translational speed of clockwise rotation is usually less than that of counterclockwise rotation. With increasing circularity, the mean rotational speed of particles increases below 10 mm height, but the mean translational speed of particles decreases. The probability density distribution of rotational speed of particles with different circularities is described as a Lorentz distribution, whereas the probability density distribution of translational speed is represented as a lognormal distribution. The mean rotational speed of particles has generally a positive correlation with the mean translational speed. Therefore, particle shape (or circularity) should be considered as an important factor affecting particle motion in the study of particle trajectories and speeds during saltation.
ABSTRACT Under the combined influence of climate change and human activities, erosion–deposition patterns in many estuaries worldwide are undergoing substantial changes. However, under multifactor coupling, the drivers of estuarine erosion–deposition remain difficult to quantify; the dominant controls are not easily identified, and the underlying mechanisms are still insufficiently understood. Taking the Minjiang Estuary in southeastern China as an example, this study reconstructed subaqueous topographic surfaces from multiyear nautical charts, derived annualized DEM‐differencing erosion–deposition rates for 1992–1998, 1998–2007 and 2007–2019, and developed a stage‐specific interpretable machine‐learning framework to quantify the relative explanatory strength of different factors and examine their nonlinear driving mechanisms. The results show a clear stage‐specific reorganization of erosion–deposition controls in the Minjiang Estuary. Water depth remained highly important across all three stages, with normalized importance values of 24.0%, 26.1% and 20.5%, respectively, indicating a persistent constraint of subaqueous morphology on channel–shoal erosion–deposition patterns. Mean suspended sediment concentration was the dominant predictor during 1992–1998, with an importance of 32.9%, but declined markedly during 1998–2007 and 2007–2019, with importance values of 6.8% and 3.6%, respectively. This suggests that sediment availability shifted from a direct local explanatory signal to a broader system‐level background constraint. During 1998–2007, the importance of the engineering‐related obstruction metric increased from 9.6% to 20.7%, indicating an enhanced role of engineering structures in regulating the redistribution of limited sediment. The extended model for 2007–2019 further shows that mud content (11.4%), tidal current speed (10.1%) and significant wave height (10.1%) became important and exhibited nonlinear and condition‐dependent responses. Overall, after the construction of the Shuikou Dam in 1993, the Minjiang Estuary progressively shifted towards a sediment‐limited system, in which water‐depth morphology, human engineering activities, bed‐material conditions and tidal–wave energy jointly regulated erosion–deposition evolution. This study provides a transferable interpretable machine‐learning framework for diagnosing the time‐varying geomorphic controls of estuaries affected by the combined impacts of climate change and human activities.
ABSTRACT In the arid and semi‐arid sandy loess area, farmland wind erosion is exacerbated by spring strong winds and long‐term tillage, yet the pathways by which crop roots regulate soil properties and wind erosion resistance remain unclear; to address this, we conducted controlled experiments combining root‐soil composite preparation and wind tunnel simulations, where soil samples were mixed with foxtail millet roots to form root volume density ( RVD ) gradients of 0%, 0.2%, 0.4%, 0.6% and 0.8% and then exposed to wind speeds of 8–11 m/s at attack angles of 0°, 15° and 30° for 30–120 min, with soil mechanical properties and wind erosion characteristics measured. Results showed that wind erosion intensity decreased exponentially with increasing RVD (maximum 42.7% reduction in the initial stage at 10 m/s wind speed compared to bare soil), soil cohesion increased logarithmically from 3.7 kPa (bare soil) to 9.8 kPa (0.8% RVD ), root‐induced additional shear strength contributed 47.5%–158.67% of total shear resistance, soil erodibility ( K ‐value) declined from 2.61 (bare soil) to 1.49 (0.8% RVD ) and root reinforcement mitigated erosion by 44.8%–47.7% across all attack angles. Although erosion intensity decreases with the increase of RVD , it rises with the increase in wind speed. Mechanistic analysis revealed RVD indirectly regulated wind erosion intensity and erodibility by improving soil structural stability and mechanical properties, with RVD identified as the primary factor controlling wind erosion resistance and wind velocity dominating erosion dynamic attenuation, and we established a nonlinear empirical equation for erodibility parameters and RVD incorporating wind velocity and attack angle. This study clarifies root‐mediated wind erosion control mechanisms and provides a low‐cost, sustainable soil conservation strategy for ecologically fragile sandy loess regions.
ABSTRACT Knickpoints are prominent geomorphic features (the most well‐known being waterfalls) defined as the transition between upstream relict topography and downstream topography adjusted to boundary conditions. Despite being localised within rivers (10s of m), knickpoints profoundly control landscape evolution in the basin where they are located. In contrast to knickpoint retreat rates, studies assessing knickpoint morphology are sparse. Using systematic flume experiments, this study observes knickpoints routinely forming in homogenous‐substrate channels under constant forcing (i.e., base‐level fall rate and sediment flux). We demonstrate for the first time that (i) these knickpoints can have three distinct morphologies and (ii) their morphology is controlled by the balance between base‐level fall rate () and sediment flux (). Unstable conditions are created when outpaces vertical incision () of the channel (i.e., ). Channel steepening occurs due to erosion perpendicular to the knickpoint face at a shear stress maxima downstream of the steepest point. Thus, high base‐level fall rates where there is a greater difference between and are conducive to steep knickpoint slopes. Sediment armouring most readily occurs at the knickpoint base, reducing the erosion rate relative to the lip. This reduces knickpoint slopes when the base is well protected. When sediment flux is low, vertical knickpoints are maintained as plunge pools develop and erode upstream. The deposition of eroded plunge pool material downstream of the knickpoint armours the channel and enhances the difference between and . This study demonstrates that changing morphology may increase or decrease knickpoint erosional effectiveness through changes to its resultant erosion vector. More widely, this study represents a starting point to develop a process‐based understanding of how sediment flux and base‐level fall rate impact knickpoints in longitudinal river profiles providing the potential for more accurate models of landscape evolution across a variety of settings.
Abstract Floods reorganize gravel‐bed rivers through coupled hydrodynamics, sediment transport and vegetation mortality. However, event‐scale morphodynamic predictions remain limited when vegetation loss is represented by a single, simplified mechanism. Here, we address how explicitly representing multiple, concurrent flood‐induced vegetation disturbance processes and their feedbacks can improve the physical realism of vegetation–hydro‐morphodynamic interactions during floods. We propose an integrated framework for modelling flood‐induced vegetation disturbance processes, including mechanical failure through overturning or breakage, followed by downstream washout, burial beneath deposited sediment or persistence in a failed but nonremoved state. To evaluate the model, we compared four configurations: Case 1 (proposed framework), Cases 2 and 3 (with different postfailure mechanisms than Case 1) and Case 4 (a static vegetation case in which flood‐induced disturbance was not considered). These four configurations were incorporated into a two‐dimensional hydro‐morphodynamic model. The framework was applied to the 2019 flood of the Chikuma River, Japan and evaluated against preflood and postflood topography and vegetation distribution data. The proposed framework successfully captured the spatial heterogeneity of vegetation removal by explicitly simulating the co‐evolution of riverbed change and vegetation disturbance processes. Furthermore, the spatial distribution of washout‐dominated vegetation removal and burial‐dominated disturbance were closely associated with bar morphology. These event‐scale feedbacks, whereby vegetation disturbance directly alters flow resistance and morphodynamic evolution, are critical for reliably predicting embankment erosion and associated infrastructure risk. Future work should extend this framework to multi‐event sequences and diverse river planform types to further validate its generalizability.
Summary Large wood (LW) significantly alters flow and bed morphology in river systems, necessitating accurate parameterization in two‐dimensional (2D) hydraulic models. This study investigated the effects of LW‐induced flow resistance in 2D depth‐averaged models using a combination of systematic flume experiments and numerical modeling. Sixteen controlled laboratory experiments were conducted, varying flow conditions, LW blockage ratios (full‐span vs half‐span) and sediment presence. Rectangular porous LW structures of constant porosity ( 0.66) were placed in a recirculating flume, and flow data including water surface elevation and velocity were recorded. Drag coefficient () and Manning's roughness were calibrated for each case using Gaussian Process Optimization to minimize model error based on measured water depths and flow partitioning. Results show that LW flow resistance parameterization is more complex than previously assumed. In addition to LW characteristics, it also depends on flow condition, blockage and sediment transport. Sediment presence and the resulting bed topography exert significant influence on flow resistance parameterization, followed by LW blockage configuration. Flow resistance parameters displayed wide variability even with fixed LW porosity, with ranging from 14 to 65 and Manning's from 1.17 to 2.6. These large values are equivalent resistance coefficients that represent the bulk drag of the emergent porous LW lumped over its footprint, not bed‐surface roughness values. While both and Manning's yield equivalent flow resistance in 2D modeling, 's dimensionless nature may offer broader generalizability. Importantly, the study confirms that parameter calibration is essential, especially for cases involving sediment transport and complex bed morphology. Rather than a single empirical formula, the study yields regime‐dependent guidance: where the bed stays relatively flat the resistance can be treated as a function of LW characteristics, whereas calibration is recommended where sediment‐shaped scour produces strongly three‐dimensional flow. These findings provide practical guidance for river modelers and engineers incorporating LW effects into flood‐risk assessment and restoration design.
Abstract Soil erosion and nutrient leaching due to overland flow are among the major threats to the sustainability of rice paddy systems, particularly where rainfall is intense. The objectives of this study were to evaluate the effectiveness of rice‐husk‐derived nanosilica for reducing soil detachment capacity (D c ) and potassium (K) leaching and to test the accuracy of key hydraulic variables in predicting D c . Laboratory flume experiments were performed on paddy soil samples treated with four nanosilica rates (0%, 1%, 2%, 3% and 4% w/w, referred to as NS0, NS1, NS2, NS3 and NS4, respectively) and untreated under multiple flow discharges and low slope (<1%). Soil detachment capacity and K leaching were measured, and D c was modelled based on key hydraulic parameters (shear stress, τ, and stream power, Ω). Nanosilica application significantly reduced mean D c soil across all flow conditions on average by 15%–50% compared to untreated soil, depending on discharge and dose. The largest decrease (over 45%) occurred at doses over 2% nanosilica, beyond which improvements showed a plateau. Potassium leaching losses were also significantly reduced by 55% (NS2) to 60% (NS4) compared to the control. Moreover, critical shear stress and stream power both increased, while soil erodibility coefficients decreased with nanosilica addition. Non‐linear regression models based on shear stress and stream power showed strong prediction accuracy of D c ( R 2 = 0.86–0.96). This confirms that these key hydraulic predictors reliably estimate D c and capture amendment effects. Overall, the combined reduction in particle detachment and K loss demonstrates that rice‐husk‐derived nanosilica can simultaneously improve erosion resistance and nutrient conservation; modelling results indicate a threshold‐type response. Beneficial effects of nanosilica amendments are observed at the highest doses, suggesting that moderate application rates may be sufficient. These findings support the use of waste‐derived nanosilica as a circular‐economy soil amendment for improving the physical and functional resistance of rice paddy soils.
Abstract Macro‐roughness elements (MREs) are widely used in river restoration to enhance flow heterogeneity and habitat diversity, but their impact on flow capacity and associated backwater rise (i.e., upstream increase in water level) remains insufficiently quantified. This limits the ability to balance ecological benefits against flood risk in river restoration applications. To address this gap, laboratory experiments in a fixed bed flume were conducted to investigate three simplified designs of MREs, namely, a boulder structure, an engineered logjam and a rootwad composite. Flow velocity, turbulent kinetic energy and backwater rise were measured under subcritical and supercritical flow conditions, for varying structure dimensions, solid volume fractions and configurations, including channel‐spanning and partial‐spanning setups (i.e., structures leaving a lateral gap with the channel wall). Results showed that backwater rise scales with Froude number and relative width of the structure, while it is insensitive to structure length and submergence depth. Backwater rise can be predicted by extending an existing semi‐analytical model based on flow partitioning through and around the structures. Differences among MRE types had limited influence on backwater but strongly affected local flow patterns. In particular, porous structures with complex internal geometry (e.g., rootwads) enhanced flow diversion and gap velocities, despite their low solid volume fraction, whereas boulder arrays generated jets in the wake and higher turbulent kinetic energy. Flow heterogeneity increased under emergent and partial‐spanning configurations, while higher Froude numbers and submerged conditions promoted more uniform flow. These findings provide guidance for selecting and configuring MREs across a range of flow conditions to optimize ecological benefits while minimizing flood hazards.
Abstract A set of 10 Be‐derived catchment‐wide denudation (CWD) rates in a low mountain catchment of western Europe (Strengbach catchment, Vosges Mountains) are analysed to discuss landscape stability. Together with a morphometric study, the data highlight the heterogeneous behaviour of the main trunk and major tributaries. Overall, the rates range from 39 to 84 mm/kyr across the catchment, the main trunk shows increasing rates from 41 to 48 mm/kyr from source to outlet, and the tributaries have systematically higher rates (42 to 84 mm/kyr). To discuss the origin of these variations, we look for systematic characters related to both morphology and lithology. We apportion the landscape of each sub‐catchment (upper main trunk and tributaries) among four main lithologies (granitic, metamorphic and two sandstone units) and three main morphologies (steep hillslopes near riverbeds, gentle hillslopes and steep slopes) resulting in nine landscape types defined by their combined lithological and morphological characteristics. A Monte Carlo adjustment method based on a Quantum‐behaved Particle Swarm Optimization (QPSO) algorithm has been applied to retrieve the optimal denudations of each landscape type that contribute to each sub‐catchment CWD rate. Our results show that some zones erode up to 10 times faster, indicating out‐of‐disequilibrium relief evolution. We use the inversion results to quantify the pace of landscape adjustment, including cliff retreat in tributaries and retreat of major knickpoints within a stream‐power incision framework. This approach allows us to show that modest gradients of CWD at the catchment scale can coexist with an internally transient landscape with focused denudation near knickzones and cliffs. The horizontal retreat rates of knickpoints, which are up to one order of magnitude larger than sub‐catchment CWD, remain slow and may explain the persistence of strong relief contrasts in a low‐deformation setting. Although the 10 Be CWD rates vary only slightly, large variations in denudation rates can occur because of landscape and the lithological particularities. Our methodology makes it possible to discuss CWD variations in slowly evolving environments and their role in maintaining high relief in close to steady‐state mountain landscapes.
Abstract Intensification of hydroclimatic volatility increases the potential for large floods to reshape rivers and threaten infrastructure. Fluvial geomorphic resilience, defined as a river's resistance to, and recovery from, flood disturbance, offers a framework for understanding river response to extreme events and guiding management. We assessed resilience at two scales: (1) a detailed geomorphic and hydraulic analysis of the June 2022 flood on East Rosebud Creek, Montana, which was part of broader flooding in the Greater Yellowstone Ecosystem, and (2) a multiriver comparison of 13 flood‐impacted alluvial mountain rivers (East Rosebud Creek plus 12 additional sites across North America and Europe). We quantified resistance using active‐channel width ratios () and recovery using postflood channel evolution () and recovery rate (). East Rosebud Creek showed strong spatial variability in disturbance among two defined segments, with an upstream segment shifting to new forms via widening, coarsening and/or incision, whereas a downstream segment that experienced similar flow strengths adjusted more modestly, within a dynamic geomorphic equilibrium. Slope, confinement and grain size were key influences on flood response in East Rosebud Creek. In the multiriver analysis, multilevel regression showed a positive log‐transformed relationship between normalized flood peak exceedance above the () and mean and a negative linear relationship between mean slope and mean . Multiriver results suggest that slope‐driven influences on vegetation growth shape recovery. Understanding patterns of resilience can improve flood adaptation strategies and inform targeted river management.
Abstract Over the past four decades, the water and sediment fluxes of the Yellow River to the sea and the deltaic coastal morphology have changed markedly under the combined influence of human activities and natural processes. There is an urgent need to quantitatively investigate how shoreline adjustments driven by outlet migration and the embayment north of the river mouth affect the nearshore tidal‐current field. In this study, Landsat imagery and multi‐year bathymetric data were used to resolve shoreline changes, subaqueous topographic evolution, and outlet shifts of the Yellow River Delta in 1987, 2000, and 2023. A numerical hydrodynamic model was established to quantitatively evaluate the influence of different outlet and shoreline configurations on the nearshore tidal regime and to reveal the response mechanisms of the tidal‐current field to shoreline evolution, river‐mouth deflection and changes in runoff intensity. The results indicate the following: (1) Nearshore tidal currents are predominantly rectilinear, and an elliptical high‐velocity zone (>0.8 m/s) that migrates with the river mouth has persisted. Northward deflection of the river mouth has created an embayment between the Gudong seawall and the mouth, where current speed has decreased significantly, with a maximum reduction of 0.46 m/s, corresponding to a change rate of 78.23%. (2) Runoff intensity strongly modulates water levels and tidal currents near the river mouth. The runoff‐dominated area expands with increasing discharge, and under extreme runoff (4000 m 3 /s), the influence can extend up to approximately 10 km offshore beyond the mouth. (3) The distribution and strength of the tidal‐current field are significantly affected by the outlet course and shoreline configuration. Corresponding adjustments of the tidal‐current field are observed in regions of intense erosion and accretion, such as the Gudong nearshore area and the active and abandoned river mouths. These findings are of considerable engineering value for understanding delta morphodynamics and informing nearshore environmental management.
Abstract Soil reinforcement is a potential solution to mitigate wind‐induced sand erosion. Previously, microbiologically induced calcite precipitation (MICP) has been used to control sand erosion and enhance the strength of soil particles. However, it has limitations. The present study explores the effectiveness of an alternative biologically inspired method, enzyme‐induced carbonate precipitation (EICP), in enhancing the stability and strength of aeolian sand. The novelty of this study lies in the identification of an optimal dosage through a multiscale evaluation of EICP performance, specifically targeting high‐velocity erosion resistance (up to 30 m/s), surface strength uniformity, penetration depth, mechanical reinforcement and the explicit characterization of calcite thermal stability. Plant‐based Jack bean urease was used at varying concentrations with a 1‐M cementation solution. To mitigate wind‐induced sand erosion, surface treatment was performed using the spray method. The treated specimens were subjected to a wind tunnel test, a surface strength test, a calcite test, scanning electron microscopy (SEM) analysis and energy‐dispersive X‐ray spectroscopy (EDX) analysis. To evaluate the strength of soil particles, unconfined compressive strength (UCS) and split tensile strength (STS) samples were treated using the stopped and gravity flow methods and were tested for UCS, STS, ultrasonic pulse velocity (UPV) and calcite formation. Additionally, to assess the thermal behaviour of the formed calcite, thermogravimetric analysis (TGA) was performed. The study demonstrated that the EICP method effectively mitigates erosion up to a wind speed of 30 m/s and achieves optimal soil strength, with a maximum UCS value of 756 kPa and 5% calcite formation. However, practical implementation considerations, including extended treatment duration and long‐term durability under field conditions, require further investigation before large‐scale application.
Abstract The relationship between beach slope, sediment size and therefore its permeability has been the subject of study for decades. Particular attention has been paid to sand and gravel beaches, but less research has focused on coarse beaches. In this work, we analyse coarse beaches characterized by a low thickness, around 35–50 cm, composed of surface pebble and cobble clasts (D50 of the B ‐axis between 41 and 102 mm) with a mixed matrix of sand and gravel (D50 between 0.76 and 12.33 mm). The most notable element is the presence of an impermeable underlying cohesive sediment up to 1 m of thickness, which gave a radiocarbon date much older than the time when sea level reached its present level. In spite of the occurrence of an impermeable layer at a low depth that reduces its permeability, the slope of the beach ranges from 7.13° to 11.3°, and the correlation between the beach slope and the bulk matrix and sand sizes of the infilling sediment corresponds to what was expected, and the underlying cohesive sediment reached the same slope as the beach. These results suggest that the development of the present coarse‐grained beaches is that the erosion of cohesive sediments occurred contemporaneously with beach formation, with abrasive clasts playing a central role in shaping the equilibrium profile.
Abstract Megafires have profound impacts on the movement of water and sediment along watersheds because of changes in the mechanical and hydrologic properties of soil and vegetation. Literature has often focussed on local post‐wildfire mass‐wasting events, although less attention has been paid to watershed‐scale river responses. We present a study from the Deadman River of British Columbia (Canada), which was recently affected by wildfires, including the severe Sparks Lake Fire of 2021. Timelapse photogrammetry and multispectral remote sensing on both pre‐ and post‐fire conditions show how fire‐related changes in hydrology and vegetation influenced channel morphodynamics. The photogrammetric analysis indicates a watershed‐wide increase in channel width and meander migration rate after the Sparks Lake Fire, with a sharp increase of up to 100% and 540%, respectively. Once normalised by the timespan over which migration rates are averaged, results indicate an up to ~20‐fold increase in channel mobility post‐fire. The remote‐sensing analysis reveals that regions that burned more severely drained into reaches that migrated laterally at faster rates. These results provide a quantification of the degree to which megafires alter the morphodynamics of meandering rivers, with anticipated ramifications for natural‐hazard mitigation and ecosystem recovery efforts in affected areas.
Abstract Tagged particles (painted, with inserted magnets, RFID labelled) used as tracers have often been deployed in field experiments focused on tracking the displacement of river gravels. In this way, fluvial geomorphologists have explored the relationships between mean travel distances and flow strength, among many other topics. However, these kinds of tracer experiments have typically been conducted without clear guidelines or rules on what constitutes an adequate sample size of tracers to minimise bias and uncertainty in displacement metrics. To fill this gap, we propose a probabilistic model that we applied to simulate and analyse the influence of the size of the tracer sample on the precision and accuracy of mean travel distances. We also used this model to explore how different causes of tracer loss (loss of frontrunners, buried tracers, due to signal collision and random) influence sample representativeness. Model results suggest that understanding the influence of sample size in particle tracking experiments in gravel‐bed rivers requires an explicit consideration of the different sources of tracer loss. According to the model, the loss of frontrunners and the consequent truncation of sampled travel distances is the most important factor conditioning the accuracy in the estimation of mean travel distances. Its impact is more significant than in the case of losses of buried tracers, losses due to signal collision and random losses resulting from low tracer densities or resulting from a poor survey. Based on our analysis, we concluded that 500–1000 tagged stones is an optimal tracer sample size for estimating mean travel distances. We hope that the outcomes of the proposed model could be used as a supporting tool to assist in the design and programming of future particle tracking experiments in gravel‐bed rivers.
Comprehensive prefailure datasets combining soil depth distribution, topography and porewater pressure at the soil-bedrock interface are rarely available for natural shallow landslides. This study presents a case in which such datasets were collected before a shallow landslide in a forested headwater catchment, providing a unique opportunity to examine the dominant topographic and hydrological features triggering the landslide and to evaluate the predictability of its location and timing using prefailure information. The analysis revealed that the landslide area was characterized by thinner soil layers, steeper slopes, larger contribution areas and higher topographic wetness index values. A logistic regression analysis confirmed that bedrock topographic features better explained the landslide distribution than surface topographic features, with soil depth being the primary predisposing factor. The landslide event began under wetter-than-average conditions; at failure, widespread saturation developed across the site with a record-high porewater pressure that exceeded the predicted value from the long-term rainfall-porewater pressure relationship. This record-high porewater pressure was attributable to both vertical rainwater percolation and groundwater exfiltration from bedrock layers. Integrating in situ information into a simple slope stability analysis improved the identification of locations with relatively high or low susceptibility; however, predicting the exact timing remained challenging. Notably, neither the amount nor the intensity of the triggering rainfall event was at a historical maximum, highlighting the limitations of rainfall-only approaches and the added value of subsurface hydrological monitoring. Our field evidence demonstrates that porewater pressure exceeding a site-specific threshold is a critical indicator for landslide occurrence. Establishing site-specific rainfall-porewater pressure relationships and monitoring groundwater seepage from bedrock layers at susceptible locations can substantially improve early-warning capabilities for landslides not triggered by extreme rainfall.
Abstract Increased collaborations between geomorphologists and artists have recently been suggested as possible ways of improving the visibility of geomorphology and of stimulating interest in and engagement with the discipline. As a well‐established art form, poetry provides a unique set of challenges and opportunities for such collaborations. Here, we present two original poems about an enigmatic coastal landform and surrounding landscape—Dinas Dinlle hillfort, north Wales—and reflect on the wider potential of poetry to facilitate enchantment with, and communication of, geomorphology. We discuss how poetry's potential could be employed particularly effectively in two specific sectors: (1) education, through aligning field experiences with creative writing sessions, and by linking with emerging cross‐curricular concepts such as cynefin in Wales and ‘greening the curriculum’; and (2) heritage, where links between geomorphology and social and cultural history can be made in collaboration with archaeologists and heritage managers. We contend that poetry can contribute to creating a more diverse and inclusive discipline by fostering increased engagement and facilitating discussions between different actors, including the more‐than‐human elements of landscape.
Abstract Soil erosion reduces soil productivity and pollutes streams and reservoirs through sediment inflow. Daecheong Lake, South Korea and its surrounding area, including the study area, is designated as a water source protection zone and has been experiencing increased soil erosion due to climate change, leading to water quality degradation. In this study, 137 Cs and 210 Pb ex radionuclides were used to estimate the medium‐ to long‐term soil erosion rates in cultivated and forest areas typical of the Daecheong Lake region. The average erosion rates estimated using 137 Cs and 210 Pb ex were 4.73 and 1.10 t ha −1 yr −1 , respectively, for the forest area, and 75.61 and 124.70 t ha −1 yr −1 , respectively, for the cultivated area. For the forest area, these rates were similar to those estimated in previous studies, but the rates for the cultivated area were relatively high when compared to previously reported values. In addition, the relationship between erosion rate estimates based on 137 Cs and 210 Pb ex showed different patterns for cultivated and forest areas. This difference may be attributed to the different time scales associated with the 137 Cs and 210 Pb ex methods, enabling the spatiotemporal analysis of erosion that occurred in cultivated and forest areas. Therefore, we demonstrate the potential of using 137 Cs and 210 Pb ex to estimate erosion rates in Korea and suggest that these two distinct radionuclides can be useful tools for understanding the history of soil erosion in cultivated and forest areas through the interpretation of differences in estimated erosion rates.
