Earth Surface Processes and Landforms最新文献

While rock–organism thermal interactions on rocky shores have known biogeomorphological relevance, the influences of rock thermal properties on the conditions experienced by rock-dwelling organisms (epiliths) remain understudied. This is a significant gap given the potential ecological and biogeomorphological consequences of changing average and extreme temperatures for coastal ecosystems. Using field block exposure trials in Southern England (including the 2023 September heatwave) alongside laboratory simulations, the thermal responses of four contrasting substrates (limestone, sandstone, basalt and concrete) were compared under the same heating conditions. Indicative organism temperatures were simultaneously obtained using biomimetic sensors (robolimpets [RLs] and robomussels [RMs]) attached to the substrate surfaces. Highly divergent thermal behaviours were observed, with peak substrate surface temperatures (T_max) differing by up to 13.2°C (basalt vs. limestone) under heatwave conditions in the field. Relative substrate temperatures were consistent between the field and laboratory (T_max limestone < sandstone < concrete < basalt), corresponding to key material properties such as density and colour; and hotter surfaces were always associated with higher biomimetic temperatures. The degree of association between surface and biomimetic temperatures differed between the two sensor types, attributed to more efficient conductive heat transfer (from substrate to organism) in the case of RLs. Thermal divergence between the two types of sensors was also mediated by rock type, with substrate porosity and evaporative cooling effects having a modulating effect. Biomimetic T_max also diverged under increasingly extreme scenarios depending on the substrates the sensors were attached to. These observations demonstrate how geomorphological approaches can contribute to thermal biology research (hinting at a new ‘thermal biogeomorphology’), with implications for patterns of physiological stress, the crossing of critical thermal limits, and resulting changes in the distribution and abundance of geomorphologically relevant species. Key challenges going forward, such as addressing sensor limitations and scale issues, are also identified.

The end of the last glaciation triggered major environmental changes with implications for geomorphological systems, ecosystems and societies. From the Last Glacial Maximum (LGM) to the start of the Holocene, landscapes have undergone profound changes, with increased temperature and modification of precipitation regimes affecting the way sediments are produced and transported at the Earth's surface. Records of past denudation rates are essential for understanding how landscapes responded to this transition and are required to assess the sensitivity of this response to local environmental, climatic and geomorphic contexts. Several methods, based on terrestrial cosmogenic nuclides (TCN) inventories, are available to constrain palaeo-denudation rates over millennial timescales, but few datasets exist that display strong signals regarding the dependency of this response to the setting, and the diversity of the approaches limits the possibilities for a global analysis. In this study, we propose a new method to constrain changes in erosion rates over the Pleistocene–Holocene transition, using the well-known concept that erosion rates derived from TCN concentrations are integrated over a timescale inversely proportional to the erosion rate. By combining TCN data with topographic information, we constrain the amplitude of erosion changes at 10 ka across neighbouring basins that are eroding at different rates. We highlight a complex pattern, with an overall several-fold increase in denudation rate when entering the Holocene. Intertropical high-relief areas appear to be more prone to displaying an increase in denudation rates, which might reflect a stronger sensitivity of these landscapes to periglacial processes, monsoon regime and/or threshold hillslope dynamics.

Glacier mass balance is a key indicator of climate change, with most glaciers worldwide exhibiting negative trends due to rising temperatures. However, Adishi Glacier in the Central Caucasus presents an anomaly published by earlier studies. This research uses Ice, Clouds and Land Elevation Satellite-2 altimetry data (2018–2024) and the Shuttle Radar Topography Mission Digital Elevation Model to assess recent elevation changes and mass balance variations. ERA5 reanalysis data were used to examine potential climatic drivers. Results show persistent thinning in lower glacier regions, while the accumulation area demonstrates sustained elevation gains. The equilibrium line altitude shows a slight upward trend (+3.07 m/year), consistent with global patterns. Notably, Adishi Glacier exhibited a positive mass balance of 0.05 ± 0.17 m w.e. a⁻¹ in 2021 and 0.03 ± 0.06 m w.e. a⁻¹ in 2024, but the mean for 2018–2024 remains negative at −0.31 ± 0.09 m w.e. a⁻¹. This suggests that, despite short-term gains, the anomaly is not sustained. Compared to the neighbouring glaciers—Bezengi, Khalde, Tsaneri North and South—which show continuous negative mass balances, Adishi's stability stands out. Regional warming (+0.19°C/year) based on ERA5 reanalysis contributes to ablation zone losses, but glacier hypsometry, with an extensive accumulation area above 4,000 m a.s.l., and orographic effect of snowfall on windward slopes support temporary gains. These favourable conditions, however, are insufficient to maintain a long-term positive mass balance under ongoing climate change.

Geomorphic processes are shaped by climate changes, tectonic movements and human activities. Investigating these interactions is crucial for understanding climate change and landform dynamics. However, the mechanisms driving landform development in high-altitude regions such as the Tibetan Plateau (TP), largely unaffected by human or tectonic activities since the Holocene, remain unclear. This study investigated the Puruogangri icefield region on the central Tibetan Plateau (TP), where diverse landforms such as lakes, rivers, sand dunes and glaciers could offer valuable insights for geomorphic research. Using optically stimulated luminescence (OSL) dating, we analysed the Linggo Co delta and its outwash terraces. The results indicate that the lake maintained a higher water level from 6.2 to 3.5 ka, which dropped between 3.5 and 2.5 ka. The outwash terraces were formed during the periods of accelerated glacier melting around 5.0, 1.8 and 0.6 ka, with warm periods leading to the formation of delta foreset deposits and outwash terraces, while the cold periods characterised by reduced glacier meltwater resulted in the topset deposits as the lake levels decreased. These findings reveal that temperature could be the dominant factor influencing fluvial landform development in this region.

This study investigated the effects of varying vegetation heights and partial coverage on turbulent flow and bed morphology in a laboratory sand-bed channel with an aspect ratio of 4.615. Vegetation was distributed to represent 33.3% emergent, 33.3% just submerged and 33.3% fully submerged plants (16 cm, 12 cm and 8 cm). Velocity measurements were made using a 5 cm down-looking micro ADV, and bed morphology was surveyed with a Bosch GLM 400 Laser Distance Measurer after 24 hours of continuous flow. Results showed that while vegetation stabilizes riverbanks and beds, it also intensifies erosion in non-vegetated zones. Streamwise velocity decreased by 20–40% downstream of vegetated areas and increased by 25–40% in non-vegetated areas. Higher turbulent intensities were observed at the vegetated/non-vegetated interface, while weaker intensities occurred within vegetated zones. The strength of streamwise-vertical Reynolds shear stress is close to zero with negative magnitude in the shorter vegetation (8 cm) region, while higher with negative magnitude in taller vegetation (16 cm) at the interface of the vegetation region indicated helical flow due to the intermixing of different flow velocities. This research enhances understanding of the effects of heterogeneous vegetation on flow dynamics and sediment transport, offering insights for riverbank and riverbed restoration efforts.

Reservoir bank landslides in the Three Gorges Reservoir (TGR) area frequently show step-like displacement characteristics under coupled reservoir water level (RWL) fluctuations and rainfall, posing significant challenges to hazard early-warning systems due to their abruptness and complexity. This study identifies three key trigger conditions for step-like displacement by analysing the displacement characteristics of landslides. Using the Hejiabao landslide as a case study, the transient release-inhalation method (TRIM) was employed to assess the unsaturated soil hydraulic properties of both the slide body and slide zone soils. Additionally, physical modelling tests were conducted under rainfall and RWL rise and fall conditions to simulate the triggering conditions. The results from TRIM and physical modelling tests reveal the underlying mechanisms of step-like displacement in reservoir bank landslides.

Furthermore, the asymmetric hysteresis effect of the soil-water characteristic curve (SWCC) governs the spatial–temporal distribution of pore water pressure. High hysteresis in the slide body delays deformation, while low hysteresis in the sliding zone accelerates instability. This study suggests optimizing early warning models by incorporating hydraulic hysteresis parameters and dynamic permeability thresholds, with particular attention to the synergistic effects of RWL drop rate and rainfall intensity.

These findings provide a theoretical basis for risk assessment and early warning improvement in reservoir bank landslides, highlighting the importance of hydraulic hysteresis and dynamic coupling modelling for enhanced prediction accuracy.

This study explores the effect of waves on sediment beds of known grain-size distribution under controlled experiments for simulating coastal environments. The experimental setup replicates flat and upward sloping bed conditions, comprising a bimodal grain-size distribution, and evaluates the changes in distribution under the surface waves of different frequencies. The results demonstrate a significant modulation from an initial bimodal to a unimodal grain-size distribution in the sloping bed. In contrast, the original size distribution is retained in the flat bed. Statistical analyses revealed a shift towards finer grains in the upward sloping area, driven by wave-induced sorting mechanisms. It is interesting to note that the observed grain-size distribution in the transitional region from the plane bed to the upward sloping bed follows a Gaussian distribution, as both the coefficients of skewness and kurtosis show zero, irrespective of the wave frequencies. These outcomes align with previous research, contributing to a deeper understanding of sediment transport and grain-size distribution in coastal zones. In addition, prototype field photographs of bedforms because of low tidal waves show immense similarities with the ripple morphology along the upward slope generated in the laboratory flume. Moreover, the concentration of heavier coarse fractions of grains occasionally dropped at the trough regions of the fine-grained ripples of lunate shapes. The study's insights are valuable for improving coastal management strategies, particularly in areas vulnerable to sediment redistribution and erosion.

This study examines the relationship between structural connectivity, forcing conditions and functional connectivity of debris flows in an alpine catchment in the Austrian Alps. We investigate two consecutive rainfall events in the Horlachtal valley in 2022 that triggered 163 and 69 debris flows, respectively, providing a unique opportunity to assess connectivity under different rainfall forcing magnitudes. Using the Index of Connectivity (IC) to represent structural connectivity, spatially distributed precipitation data for forcing and a debris flow–channel proximity metric to quantify functional connectivity, we evaluate how well the IC predicts debris flow–channel coupling with and without incorporating observed forcing information. Our results demonstrate that the IC serves as a robust predictor of debris flow connectivity across different forcing conditions, with strong correlations for both events. While observed rainfall forcing showed moderate correlation with functional connectivity, their inclusion in predictive models provided only marginal improvement (2% additional variance explained) over IC alone. This suggests that topographic and morphological constraints, rather than precipitation patterns, predominantly control debris flow propagation in this setting. Notably, the predictive capability of the IC proved relatively stable despite substantial differences in rainfall magnitude between events. Various regression models were evaluated, with quadratic and beta regression approaches performing best. The proximity metric used in this study offers advantages over binary coupling classifications by providing more nuanced information about functional connectivity, especially valuable when most observed processes do not reach the channel network. These findings empirically validate the IC as a meaningful descriptor of system structure in alpine catchments and suggest that challenges in spatial transferability of IC models likely stem from factors other than forcing variability.

The design and construction of post-mining landforms is a complex undertaking where any structure requires integration with underlying materials and the surrounding unmined or undisturbed landscape. A common reconstruction design for post-mining landscapes is to have linear hillslopes with drains or runoff diversion structures that are designed for the hillslope length, angle and climate. These landscapes are easy to construct and result in a surface which can be easily traversed by agricultural machinery, while the benches often rely on drainage control structures to manage runoff and resultant erosion. Few mines worldwide have committed to a catchment-based reconstruction approach or that employing geomorphic design. Here, a method for catchment design has employed a simple strategy of an uplifted catchment being allowed to evolve using a computer-based Landscape Evolution Model until the volume matches that of a proposed design. The computer-generated landforms are compared with that of a catchment created using site hydrology and sediment transport conditions (Expert Knowledge) by a recognised design engineer. The results demonstrate that a computer-generated landscape produces sediment output within that of target erosion rates with low gully depths. The design created using Expert Knowledge produces sediment output above background erosion rates as well as having maximum gully depths of up to 2.7 m. Modelling demonstrates that computer-generated designs produce erosion rates which are approximately one-third to half that of the Expert Knowledge design, with a commensurate reduction in maximum gully depth. The computer model-generated catchments also have a more natural appearance with regular curvature and channel definition. A key finding is that landscapes with a series of smaller catchments and a more complex drainage network produce less sediment output.

This study investigates large wood (LW) recruitment from the floodplain to the channel in a mountain stream in northeastern Italy, following the exceptional 2018 flood triggered by the Vaia Storm, a severe windstorm and intense precipitation event. It aims to quantify in-channel LW loads, estimate floodplain-recruited LW volumes, explore the links between hydraulic forcing, sediment balance, lateral connectivity and recruitment and explore the potential of numerical modelling in such a context. The study focuses on a 9.5 km segment of the Tegnas Torrent, a mountain stream with a catchment area of 52 km². Post-event in-channel LW was quantified through field surveys across sampling segments, while to assess recruitment volumes, a combination of pre- and post-event remote sensing data and 2019 field plots was used to estimate standing volumes and identify trees eroded by flood-induced channel widening. At the reach scale, key variables related to hydraulic forcing, sediment dynamics and lateral connectivity were evaluated, and correlations with LW recruitment were analysed. Finally, a two-dimensional numerical model was applied to simulate and compare the flood-driven erosion and wood recruitment. The total in-channel LW volume was estimated at 496 m³ ± 220 m³, averaging 18 m³ ha⁻¹, which is consistent with values from nearby, although undisturbed, mountain streams. In contrast, 2080 m³ (132 m³ ha⁻¹) of wood was recruited due to lateral channel widening. Our findings revealed that recruitment is influenced by complex factors, with limited correlation to sediment dynamics and hydraulic energy. Wider lateral erosion does not always lead to higher recruitment, as the riparian corridor's forest composition and structure play a key role. The numerical model provided reasonable estimates of channel widening and associated LW recruitment, making it a useful tool for approximating potential flood-induced planform changes. However, for more accurate results, further refinement in vegetation and sediment transport modelling is necessary.