Abstract Blowouts are geomorphic features formed through the interplay of aeolian processes, vegetation cover and anthropogenic disturbance. Although the basic dynamics of airflow over blowouts under unidirectional winds are relatively well understood, fine‐scale airflow patterns under bi‐directional wind regimes remain poorly characterised. This study investigates airflow dynamics within a small trough blowout located in the coastal dune system of Canet‐en‐Roussillon (SE France), where foot traffic has modified the original morphology. Wind data were collected using 26 anemometers deployed across and within the blowout, capturing spatial and vertical variations during both offshore and onshore wind events. The blowout exhibits a bifurcated morphology that alters airflow asymmetrically: offshore winds are steered oblique to the shoreline and sustain acceleration along the main axis (pattern [c]), whereas onshore winds generate more parallel flow, resulting in deceleration and turbulence (pattern [a]). This contrast gives rise to distinct internal flow structures, flow bifurcation under offshore winds and widespread near‐surface disturbance under onshore winds. A shallow, disturbed near‐surface flow develops within the blowout, constrained vertically by blowout dimensions, and decoupled from the more coherent higher and above‐blowout flows aligned with the incident wind. Peak velocities for both wind directions are observed in the constricted throat region (pattern [b]), though classic jet flow does not develop, likely due to bifurcation and throat morphological constraints. These findings highlight the sensitive coupling between blowout morphology, wind regime and anthropogenic alteration in shaping airflow behaviour within a small trough blowout.

Abstract Tropical glaciers are important indicators of climate change, provide freshwater resources for downstream communities, and form an important component of the hydrological cycle. Understanding the dynamics and patterns of behaviour of tropical palaeoglaciers is important for interpreting their sensitivities and vulnerabilities. Glacier advances in the high tropical Peruvian Andes occurred multiple times during the last glacial cycle and Holocene, leaving complex geomorphological evidence on the landscape. The substantial topographic, geological and climatic variability in this region leads to high geomorphic diversity. However, few detailed geomorphological studies have been conducted to date, leading to considerable uncertainty in the behaviours and drivers of tropical palaeoglaciers. Here, we provide a detailed geomorphological analysis of the Cordillera Vilcanota, Cusco region, southern Peru (71°W, 13.7°S), and use morphostratigraphic principles to reconstruct the former maximum icefield extent and palaeoglacier advances. Across this domain, we mapped ~23,000 features encompassing five key environments: glacier, subglacial, ice‐marginal, fluvial and lacustrine. The mapped features show evidence of both modern‐day polythermal and temperate ice margins, with low meltwater volumes leading to small‐scale glaciofluvial landform formation. However, larger moraines, beyond those well‐dated to the Younger Dryas and Antarctic Cold Reversal, assumed to represent Last Glacial Maximum and earlier advances, suggest that conditions were temperate and drained by more substantial rivers, with coupled flow of ice and till, and evidence of subglacial scouring, drumlin formation and the deposition of substantial moraines and large palaeosandar. Our reconstructed maximum icefield covers 2,660 km 2 and was drained by multiple topographically constrained ice lobes across the region. In the north, these ice lobes reached an elevation of 3,500 m asl, but were limited to above 4,500 m asl in the south, likely reflecting the dominant moisture sources. Our geomorphological mapping reveals seven clear ice margins, morphostratigraphically correlated across the study region, reflecting at least seven palaeoglacier advances during the last glacial cycle, including the Late Glacial period and the Holocene.

Abstract Complex evolutionary processes imprint distinct geomorphic signatures on the landscapes, offering valuable insights into the evolution of Earth and other planetary surfaces. In fluvial landscapes, river networks are thought to evolve toward configurations that minimize the energy expenditure required to transport water and sediments. Thus, the evolutionary stage of a landscape can be assessed by its energy expenditure; however, this has not yet been systematically studied using real landscape data. In this study, we quantify the relative energy expenditure of the drainage network in reference to the optimal channel network (OCN) algorithm to gauge the landscape efficiency. Additionally, the evolution of river networks towards optimal patterns would influence the basin morphology, potentially offering insights into the stages of evolution. To examine this, we used Hack's law, a well‐studied power‐law relationship between channel length and basin area, as experimental studies have observed that Hack's exponent () changes with evolution. Our analyses of 25 islands show that and are positively correlated, suggesting that both decrease as landscapes evolve and that drainage basins organize into less elongated and more energy‐efficient configurations. To further verify this relationship, we employed a simplified stream power incision model (SPIM) to simulate landscape evolution under fluvial processes and found that both and decrease over time. Thus, our analyses demonstrate the effectiveness of the numerical indicators, Hack's exponent and energy efficiency, in characterizing fluvial landscape evolution.

Abstract The Three Gorges Dam (TGD) and Xiaolangdi Dam have triggered substantial morphological changes along the middle Yangtze River and the lower Yellow River (LYR), respectively. Yet a comprehensive comparison of these changes is lacking, which hinders our understanding of large rivers' response to mega‐dam operation. Based on systematic data of hydrology, sediment and cross‐sectional surveys over the last two decades, we compared the water‐sediment conditions and the morphological changes of the two rivers. Results showed that sediment load decreased by about 90% in both rivers while discharge reduction was minor. Both rivers underwent degradation, widening, decreased width‐to‐depth ratio (W/H), reduced slope and bed coarsening, but with different magnitudes, rates and spatial extents. The average incision depth of thalweg was 4.2 and 4.6 m, and the maximum was 24.9 and 11.9 m at the Yichang‐Chenglingji Reach (~380 km) in the middle Yangtze River and the LYR (~730 km), respectively. The upper Jingjiang reach experienced the most severe degradation within the middle Yangtze River, with no temporal declining trend of the erosion rate. Erosion centers were primarily located in the braided reach of the LYR. The erosion rate at this reach decreased recently after about 2017, while it increased at the downstream transitional and meandering reaches. The changes in the LYR agree with Lane's balance, and W/H was negatively correlated with water discharge multiplied by slope. Heterogeneous changes along the channels prohibited the application of simplified, unified frameworks for channel adjustment to regulated water and sediment.

No abstract is available for this article.

Abstract Single‐ and multi‐thread gravel‐bed ephemeral channels in semi‐arid and arid regions have a characteristic repeating, channel‐wide pattern of low angle, fine‐grained ‘flats’ alternating with steeper, coarse‐grained ‘bars’. The genesis of these macroforms, while a topic of ongoing discussion, has not been fully elucidated. We have documented the formation of these macroforms after both artificially homogenising the bed material of a reach of the Nahal Yatir in the northern Negev, Israel, and ensuring its surface was planar. Here, we integrate the empirical data gained from these field experiments with a novel mathematical model. The model we propose, within a one‐dimensional framework, is based on the analysis of flow over an initially planar, erodible bed consisting of a bimodal grain size mixture of sediment. We apply linear stability analysis to derive a solution that provides insight into the formational dynamics of these macroforms. Our results indicate that bar‐flat patterns may arise from a free‐instability mechanism driven by sediment size heterogeneity, provided that the standard deviation of the sediment grain size distribution (GSD) is sufficiently large. Application of the model to a selection of ephemeral channels of the northern Negev suggests that repeating bar‐flat patterns are likely to develop during the recession of flash flood hydrographs, specifically when flow conditions approach the critical threshold for bedload transport. Besides providing a possible explanation for the formation of these macroforms, this study also contributes to a broader understanding of geomorphic processes in dryland river systems.

Abstract 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.

Abstract Recent releases of high‐resolution elevation data in British Columbia have revealed several previously unidentified meltwater‐derived landforms associated with the last Cordilleran Ice Sheet (CIS). Prominent among these are small subglacial meltwater corridors (sSMCs): morphologically distinct channels up to 10s of km long that are eroded into glacial sediments, with varying intra‐corridor landform assemblages. Intra‐corridor landforms identified include curvilinear ridges, eskers and multi‐ridged fans. The sSMCs are one or more orders of magnitude smaller than the previously described Chasm and Green Lake meltwater corridors, the latter two formed from an extremely large supraglacial lake outburst flood. Results from geomorphological, sedimentological and near‐surface geophysical methods show that an erosional unconformity cut into the regional till sheet forms the base of each sSMC. This unconformity extends from the channel boundary and includes intra‐corridor curvilinear ridges and erosional remnants, consistently topped by a 0.2–0.3 m thick concentration of cobbles. A discontinuous channel‐wide fill (5–15 m thick) buries some curvilinear ridges and is sometimes capped by an intra‐corridor esker. Multi‐ridged fans occurring downflow from braided outwash plains postdate the sSMCs and all other intra‐corridor landforms. We interpret the sSMCs as palimpsest landforms that developed over several melt seasons through the continuous reoccupation by subglacial meltwater flow (and later proglacial streams). Each trough found lateral to a curvilinear ridge represents an individual subglacial meltwater channel incised over one or more melt seasons. The broad corridor fill records higher‐than‐average melt season discharge within portions of the sSMC, burying or further eroding curvilinear ridges and potentially forming eskers during late‐stage waning flows. Results from this study indicate that the last CIS had an active and dynamic subglacial drainage system during deglaciation.