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Vegetation colonization is known as an effective process for stabilizing talus slopes, but little quantitative data is available about the relationships between vegetation, sediment fluxes, and sediment storage. The results of a detailed analysis of a single active fine-grained scree slope show that the upper section, scattered with shrubby vegetation, represents an environment characterized by strong biogeomorphic feedbacks. Engineering species (Thuya occidentalis, Betula papyrifera , Cornus sericea, Salix caprea) are well adapted to high sediment mobility with different modes of reproduction and survival. White cedar has a high sediment trapping capacity (>22 m3 per individual) and generates a micro-relief of 80 cm on average. It is responsible for 99 % of the volume of sediment trapped by shrub vegetation, even though it represents 44 % of the total shrub population sampled. In contrast, the hardwoods species have a very low capacity for sediment trapping (<1 m3 per individual) and micro-relief generation (>20 cm). This is likely due to the morphology of the growth which, despite a strong capacity to produce stump rejections, remains limited in trapping sediment. The shrubby vegetation directly influences the trajectory of frost-coated clast flows, the dominant slope process. Nevertheless, the vegetation appears to be quite resilient and stable on a decadal scale, where even the occurrence of extreme debris flows had little impact. In the downslope section, the debris flows, frost-coated clast flows, and snow avalanches present original and circumstantial modalities of tree-line regression. If the upper slope remains of sufficient size to allow for the occurrence of high-magnitude geomorphic events, the tree line appears to be driven primarily by slope processes rather than climate. Although it may be surprising that recent warming lowers the tree line on the studied talus slope, this provides new insight into the complex and non-linear relationships between vegetation and talus slope processes. • Shrub vegetation on active scree provides strong biogeomorphic feedbacks. • White cedar has a high sediment trapping capacity compared to hardwood species. • Engineering species are adapted to sediment mobility for reproduction and survival. • Mass-wasting processes present circumstantial modalities of tree-line regression. • Tree line is driven primarily by slope processes rather than climate. [ABSTRACT FROM AUTHOR]

Retrogressive thaw slumps (RTS) are an important landform of rapid permafrost degradation in regions with very high ground ice contents. RTS mobilize significant amounts of sediment, meltwater and organic carbon and impact downstream hydrological systems by directly affecting topography and water quality. The term megaslump has previously been coined for RTS exceeding 20 ha in size. The Batagay megaslump in the Yana highlands of NE Siberia with an area of 87.6 ha (in 2023, including the bowl-shaped part and the erosional outlet) has been identified as the largest megaslump on Earth. We use very high resolution remote sensing from satellite data and drones, geological structure modeling, and field data to assess how much and what material is thawed and mobilized in the Batagay megaslump. The total volume of permafrost thaw and material loss from the Batagay RTS amounts to about 1 million m3 per year. The material is by one third composed of thawed sediments and by two thirds of melted ground ice. About 4000 to 5000 tons of previously permafrost-locked organic carbon is released every year. Organic carbon content has been measured as Total Organic Carbon (TOC) of sediments and as Dissolved Organic Carbon (DOC) of ground ice. From its formation in the 1970s until 2023, the Batagay RTS – due to thermal denudation and headwalls retreat – mobilized a total volume of about 34.7 million m3 of which 23.4 million m3 were melted ground ice and 11.3 million m3 were thawed deposits including a total of about 169,500 t organic carbon. With these rates of sediment and carbon mobilization, the Batagay megaslump is not only a prominent local feature of rapid permafrost thaw, but offers excellent conditions to study rates and mechanisms of rapid permafrost degradations and to calculate the stock and release of, e.g., organic matter. • 3D geological modeling allowed estimating the Batagay megaslump material flux. • The megaslump mobilized ca. 35 million m3 since initiation in the 1990s. • Since 2014, the annual mobilized volume amounts to ca. 1 million m3/year. • About ⅔ of the total material volume was ground ice and ⅓ was permafrost sediments. • Organic carbon release amounts to 4000 to 5000 tons per year. [ABSTRACT FROM AUTHOR]

Creeks are essential for salt marshes by conveying water and sediment through this geomorphic system. In this paper, we investigate the mechanisms that determine the residual sediment flux using measurements conducted in tidal creeks in salt marshes of the Yangtze Estuary. A main creek and a secondary creek were studied to explore whether the mechanisms determining residual sediment fluxes through the main creek differ from those in the secondary creek. Measurements in creeks were carried out over 5 years, spanning different months. Sediment import was found during most tides, both in the main creek and the secondary creek, implying that creeks in Chongming generally function as a conveyor belt of sediment into the marsh. However, sediment export can occur during certain overbank tides. When comparing the role of creeks in drainage and sediment delivery, the main creek functions more in delivering sediment while the secondary creek primarily serves as a drainage conduit. To better understand the mechanisms behind sediment fluxes, the residual sediment flux was compared with the residual discharge and the sediment differential (differences in sediment concentration between flood and ebb). Overbank tides generally lead to a net outward discharge as more water from saltmarshes can be concentrated into the marsh creek during ebb tides. This net outward discharge tends to export more sediment during ebb tides. However, due to the sediment abundance during the flood phase in the turbid environment, sediment import can be expected even with the residual export of water. Export of sediment was only found for the few tides with a net outward discharge and a small positive sediment concentration differential. Large negative sediment differentials (larger averaged suspended sediment concentration during ebb tides) have not been observed because the sediment supply during ebb is limited. This paper unravels how the sediment differential and residual discharge contribute to the residual sediment flux, providing a better understanding of sediment dynamics in marsh creek systems. • The relative importance of asymmetries in sediment concentration and in flow for residual sediment fluxes was explored. • The main creek is mainly a conduit for sediment delivery whereas the secondary creek is mainly a drainage conduit. • Sediment supply limitation can even occur in a turbid system like Chongming. [ABSTRACT FROM AUTHOR]

Abstract The impact of wind waves and salt marsh erosion on sediment transport dynamics of macro-tidal estuarine systems has been examined using a numerical model. Morphological changes associated with salt marsh erosion facilitate the propagation of waves to the marsh edges, and increase the resuspension and export of sediments from the estuary. Results also highlight the impact of tidally-modulated changes in wave action upon sediment transport dynamics throughout a tidal cycle and from neap to spring tide. In particular, wave action at the landward margin of the estuary is limited by the shallow water depth, and tidally induced increments in water depth only cause a modest increase in wave shear stresses. At the seaward side of the domain, the impact of waves is limited by the deeper water, and tidally induced water level variations have a more significant control on wave shear stresses. The outcomes contribute new insights that are important for the sediment budget of macro-tidal estuaries facing climate change and have implications for the long-term morphological evolution of estuarine wetlands. Highlights • Enhanced sediment export from estuaries caused by wind waves • Enhanced salt marsh erosion caused by wind waves • Salt marsh erosion due to morphological changes of estuaries • Wave impact changes with varying water depth [ABSTRACT FROM AUTHOR]

This study focuses on the contrasted architectural elements of the two late Pleistocene alluvial fill sequences (T1 and T2 attributed to the Late Saalian and Weichselian) of the upstream Seine River alluvial plain, la Bassée , and constitutes the first estimation of the sediment volumes associated to these glacial cycles along this river. Estimations of the incised valley and valley fill spatial distribution are obtained by cokriging of data from 546 wells collected from the French national repository and a digital elevation model (DEM) of the present topography. The well stratigraphic attribution is given by the homogenised geomorphological map of la Bassée . We calculated the sediment volume of eroded material for the T1 sequence to be 1.70 10 9  m 3 and of valley fill deposits to be 1.18 10 9  m 3 . This corresponds to a mean thickness of 6.1 m. By contrast, volumes of the T2 sequence are one-third smaller, 1.23 10 9  m 3 . The T2 mean thickness is very similar with 5.8 m. The alluvial plain is divided into four reaches representing a typical assemblage of the T1 and T2 incision style and valley fill deposits. Along the downstream reaches (1 - Montereau-Bazoches, 2 - Bazoches-Grisy), the T2 proportion per kilometer are close to the alluvial plain mean value (reach 1: 76%; reach 2: 69%, la Bassée : 71%), the T2 mean incised valley width corresponds to three quarters of the T1 (4 km). In the middle upstream reach (3 - Grisy-Courceroy), the T2 proportion is the largest (92%), the T2 mean incised valley width is the largest and comparable to the T1 (5.5 km). Along the upstream reach (4 - Courceroy-Romilly), the T2 proportion is the lowest (53%) and the T2 incised valley (2 km wide) is enclosed within the T1 incised valley (4 km wide). The rate of exported material, though, is the same for each sequence in any reach (31%). The spatial pattern of the T1-T2 deposits coincides largely with the presence of a knickpoint along the T2 paleothalweg (downstream part of reach 4, slope face 1.5‰), suggesting that the knickpoint had a large influence on the fluvial processes. The toe of the knickpoint (reaches 3 to 1, slope 0.24‰) was the site of the most efficient erosion of the T1 deposits. We propose that the change of slope favored diversion of the channel path. Upstream of the knickpoint face (upstream part of reach 4, thalweg slope 0.34‰), the incision processes were dominated by incision, avulsions or multithreading with limited lateral migration as indicated by the numerous T1 relicts preserved across valley. The sediment export corresponds to a mean incision rate of 40 m/Ma during the last 300 kyr; a fairly low value for the Paris basin, suggesting a low uplift area north of the Massif Central. Such contrast between the fluvial processes during the T1 and T2 sequences is most likely to be looked for in the climatic conditions that existed at the onset of the incision as no local controls for the knickpoint location could be identified such as active faults, substrate heterogeneity, or flow modifications. The lower sediment flux and the knickpoint associated to the T2 sequence suggest a transient river profile and valley incision at the end of the climatic transition associated to the Weichselian (T2). [ABSTRACT FROM AUTHOR]

The Manawatu incised-valley estuary was rapidly infilled between 12,000–4700 cal. yr BP. A combination of empirical measurements of sedimentation rates, a reconstruction of relative sea-level (RSL) change, and digital elevation models of key surfaces within the Holocene sedimentary fill of the valley were integrated to produce a numerical model to investigate the influence of the system controls of sea-level change, sediment flux, and accommodation space on the rapid infilling history of the palaeo-estuary. The numerical model indicates that sediment flux into the palaeo-estuary was greatest during the Holocene marine transgression between 12,000–8000 years BP. The average rate of sediment deposition in the estuary during this period was ~ 1.0 M m 3 yr − 1 . This rapid rate of sedimentation was controlled by the rate of accommodation space creation, as regulated by the rate of sea-level rise and the antecedent configuration of the valley. By the time sea levels stabilised c. 7500 cal. yr BP, the palaeo-estuary had been substantively infilled. Limited accommodation space resulted in rapid infilling of the central basin, though sediment flux into the estuary between 7100 and 4500 cal. yr BP was at a lower rate of 234,000 m 3 yr − 1 . The limited accommodation space also influenced hydrodynamic conditions in the estuarine central basin, driving export of fine-grained sediment from the estuary. Once the accommodation space of the estuarine basin was infilled sediment bypassed the system, with a consequent reduction in the sedimentation rate in the valley. More accurate partitioning of the sources of sediment driving the infilling is necessary to quantify sediment bypassing. Post-depositional lowering of RSL index points from the valley is driven by neotectonics and sediment compaction. [ABSTRACT FROM AUTHOR]

In the second half of the 19th century, channelization of large multi-thread rivers such as the Rhine, the Danube, and the Rhône rivers induced artificial disconnection of most of their secondary channels. Compared to naturally abandoned channels, terrestrialization (i.e., the passage from the aquatic to the terrestrial stage, controlled by sediment deposits and/or lowering of the water level) patterns and rates of such artificially prematurely abandoned channels remain largely unknown. Moreover, factors controlling their evolutionary trajectories are complex owing to a set of pressures occurring throughout the 20th century within specific space-time windows. Through a case study of the Rhône River, this paper aims to assess and distinguish the effects of a set of potential controlling factors on abandoned channel terrestrialization dynamics and lifespan. We tested the influence of: (i) submersible embankments closing the entrance of abandoned channels, (ii) main channel degradation following its channelization or the water level lowering due to channel bypassing in the middle of the 20th century involving drastic water abstraction in these reaches, (iii) transverse dykes within the abandoned channels, (iv) the flooding regime of abandoned channels (i.e., frequency and magnitude of upstream connections producing lotic functioning), and (v) longitudinal variation in the suspended sediment concentration along the main channel. To this end, we studied 24 abandoned channels (16 artificially disconnected at their upstream end by submersible embankments and eight naturally disconnected by bar plug establishment) from the mid-19th to the beginning of the 20th century. Their terrestrialization rates were characterized through the reconstruction of their planimetric trajectories using historical maps and aerial photos. The results reveal a much longer lifespan of artificial abandoned channels compared to natural ones because of the truncation of the initial bedload infilling phase due to the artificial and imposed closing of their entrance. Moreover, terrestrialization occurred faster when water level lowering or channel degradation was greater. Surprisingly, terrestrialization rates were the highest in the most frequently connected artificial abandoned channels (i.e., channels with a high frequency of lotic functioning), probably in relation to the roughness induced by the presence of transversal dykes. Finally, it is difficult to rank all the factors tested because of their complex combinations, which can change in space and time. [ABSTRACT FROM AUTHOR]

Large volcanic debris avalanches are triggered by failure of the steep flanks of long-lived composite cones. Their huge deposits change the landscape and drainage pattern surrounding stratovolcanoes for thousands of years. At Mt. Ruapehu, New Zealand, we identified seven major flank-collapse events that produced debris avalanches travelling down pre-existing river catchments for up to 90 km from source. In two cases the extreme mass flux into the river valleys led to their complete truncation from the volcano, while four drainage systems were subsequently re-established along similar pathways influenced by regional strike-slip faulting, which caused localized graben formation. In all cases the volcanic debris-avalanche deposits currently form distinctive plateaus at or near the highest topographic elevations of each river valley margin. The timing of the flank failures indicate that inter-eruptive cone destabilization of Mt. Ruapehu is affected by climate change and occurs most commonly during interstadials when glaciers on the cone are in retreat, whereas syn-eruptive collapses are most prominent during cold stages. Dated debris-avalanche deposit levels, along with those of up to four stadial-related aggradational gravel terraces between c. 125 and 18 ka, were used to calculate regional uplift rates in this area. Rates of between 0.2 ± 0.1 mm yr − 1 to 3.8 ± 0.8 mm yr − 1 are found for four river systems dissecting the central North Island of New Zealand. In three cases incision below the diamicton sequences and into the basement, allowed quantification of sediment-flux rates into the Tasman Sea of 107,000 ± 1,200 m 3 yr − 1 to 177,000 ± 3,500 m 3 yr − 1 since debris-avalanche emplacement. [ABSTRACT FROM AUTHOR]

Movement of biophysical fluxes and resultant processes are governed by among other things, the (dis)connectivity structure of a landform. Hence, the quantification of connectivity structure of a landform is important in order to analyze water and sediment fluxes over a surface. Two dimensional connectivity structure through analysis of lateral and longitudinal connectivity for water and sediment flux has been quantitatively defined for the well-known Kosi megafan in north India. The avulsive behavior of the Kosi River has resulted in various paleochannels over the megafan, and they guide the flux transfer over the surface and also control the local topography of the megafan. As (dis)connectivity structure of landform is governed by its physical characteristics and also affected by anthropogenic disturbances, both these factors have been considered to quantitatively analyze the connectivity structure of the Kosi megafan for sediment and water fluxes. Megafan surface characteristics have been defined through local slope variability, land use-land cover map and flow length. These surface parameters have been used to map ‘buffers’ in the area. The distribution pattern of ‘buffers’ on the megafan surface has been used to define the ‘natural’ (dis)connectivity structure. Further, the megafan surface has also been affected by progressive development of the rail-road transport network, which is mostly east-west aligned and intersects the south flowing paleochannels. These rail-road network acts as an anthropogenic ‘barrier’ for water and sediment fluxes across the megafan surface. A detailed mapping of rail and road network in different years (1955, 1983 and 2010) has been used to characterize anthropogenic disturbance on the connectivity structure. The spatio-temporal variation in connectivity structure is attributed to density of the transport network. Finally, natural and anthropogenic disturbances on connectivity structure have also been integrated to quantitatively define the present day connectivity structure of the Kosi megafan for water as well as for sediment flux. Further, the (dis)connectivity structure has been used to explain the spatial variability of waterlogging over the megafan surface, which is presently a serious hazard in the region. [ABSTRACT FROM AUTHOR]

Abstract: A spatially lumped process–response model, PaCMod, is presented, which calculates long time series (103–106 years) of fluvial water discharge and sediment load at the river catchment outlet, based on climatic data, drainage basin characteristics and user-defined parameters. Key aspects of the model are (i) the lumped approach, allowing for fast simulations and preserving the same resolution from palaeoclimatic conditions and geomorphological reconstructions; (ii) the parameterization of sediment routing and storage within the catchment. PaCMod was successfully tested on observed data from three present-day fluvial systems: the Meuse, the Waipaoa, and the Po Rivers. Moreover, the simulated sediment flux for the Meuse and for the Waipaoa Rivers in the late Quaternary is in agreement with published field and modelling work. PaCMod experiments show how the downstream propagation of the original climatic signal is hampered by sediment routing and storage within the catchment. [Copyright &y& Elsevier]

Abstract: Quantification of contemporary geomorphological activity is a fundamental prerequisite for predicting the effects of future earth surface process and landscape development changes. However, there is a lack of high-resolution spatial and temporal data on geomorphological activity within alpine catchments, which are especially sensitive to climate change, human impacts and which are amongst the most dynamic landscapes on Earth. This study used data from repeated laser scanning to identify and quantify the distribution of contemporary sediment sources and the intensity of geomorphological activity within the lower part of a glaciated alpine catchment; Ödenwinkelkees, central Austria. Spatially, geomorphological activity was discriminated by substrate class. Activity decreased in both areal extent and intensity with distance from the glacier, becoming progressively more restricted to the fluvially-dominated valley floor. Temporally, geomorphological activity was identified on annual, seasonal, weekly and daily timescales. Activity became more extensive with increasing study duration but more intense over shorter timescales, thereby demonstrating the importance of temporary storage of sediment within the catchment. The mean volume of material moved within the proglacial zone was 4400m3.yr−1, which suggests a net surface lowering of 34mm.yr−1 in this part of the catchment. We extrapolate a minimum of 4.8mm.yr−1 net surface lowering across the whole catchment. These surface lowering values are approximately twice those calculated elsewhere from contemporary measurements of suspended sediment flux, and of rates calculated from the geological record, perhaps because we measure total geomorphological activity within the catchment rather than overall efflux of material. Repeated geomorphological surveying therefore appears to mitigate the problems of hydrological studies underestimating sediment fluxes on decadal–annual time-scales. Further development of the approach outlined in this study will enable the quantification of geomorphological activity, alpine terrain stability and persistence of landforms. [Copyright &y& Elsevier]

Abstract: This paper describes the construction and application of a new field instrument, a Gauged Sediment Trap (GaST). Our GaST measures and captures aeolian-transported sediment, can be deployed for long periods of time (weeks), is easy to construct, and is extremely durable. The instrument consists of a water-level logger contained within an underground, water-filled sleeve, into which sediment is funneled from a surface trap. As sediment enters the sleeve water is displaced proportionally to the volume of sediment allowing for continuous monitoring of sediment accumulation. The rate of sediment transport and flux, for a given time period, is estimated through laboratory calibration using sediment from the study area and the GaST. The instrument can be affixed to almost any surface-sediment trap, whether saltation or bedload transport is the target. Data from laboratory calibration and several field tests staged in the summer and winter on Bogue Banks, NC, are presented. Using the HOBO® U20 Water-Level Logger, the GaST accurately captured sediment transport at a resolution of 5.71g (2.15cm3) of sediment per unit time, depending on sampling interval and overall sediment flux. The GaST predicted total sediment mass and volumes with less than 5% error. With an adjustable sampling interval, the GaST can be deployed for various lengths of time but may be limited by the rate of sediment accumulation (they can overflow) and the evaporation rate inside the sleeve (the water could completely evaporate in arid settings). [Copyright &y& Elsevier]

Abstract: Progressive glacier thinning, retreat and mass loss in the High-Arctic is increasingly exposing forefield sediments to processes of mobilisation and redistribution. In this paper, we quantify forefield sediment redistribution at Midtre Lovénbreen, Svalbard, using repeat light detection and ranging (lidar) surveys conducted in 2003 and 2005 in combination with field-based observations. Average surface lowering of the forefield over the observation period identified from lidar surveys is −0.05ma−1; and two primary areas of sediment reworking are identified: active fluvial incision of proglacial streams by ~2m and lateral moraine downwasting of similar magnitude. Multivariate analysis of fluvial and climatological field data indicates that observed forefield sediment mobilisation is driven primarily by discharge forcing, but with contributions from thermoerosive processes and stochastic, autogenic sediment supply. During the period of observation, disparity between sediment loss in forefield fluvial systems as calculated from lidar data (3000–4000×103 kg) and monitoring of fluvial sediment load (1600–3500×103 kg) suggests the likely presence of significant quantities of buried ice beneath a thick debris mantle, as evidenced by field observations. Relatively uniform lowering of the moraine crest identified from our repeat lidar surveys indicates thermoerosion of an ice core. However, simple debris layer thickness modelling indicates an increase in variation of debris layer thickness at lower elevations, providing support for the assertion that moraine disintegration is driven by complex combinations of both thermal and mechanical processes. This study demonstrates the viability of using lidar in conjunction with field monitoring to better understand sedimentary deglaciation dynamics and processes, and also highlights the significance of forefield areas in controlling the sediment yield from deglaciating catchments. [Copyright &y& Elsevier]

The development of coastal adaptation pathways along sandy barrier-island coasts requires an understanding of multi-decadal barrier morphodynamics in response to forcings such as sea-level rise, sediment fluxes, and storminess. Long- and cross-shore sand exchanges among barrier-system compartments (shorefaces, beaches, dunes, tidal inlets, backbarrier lagoons) and between adjacent barrier islands can play a fundamental role in barrier-system morphology and resilience to sea-level rise. We explore these dynamics through investigation of historical areal changes within the 13 largely undeveloped Virginia Barrier Islands of the United States Mid-Atlantic Coast. We pair subaerial island areas mapped from historical surveys and modern aerial and satellite imagery with representative island thicknesses determined from stratigraphic and lidar-derived elevation data to estimate volumetric changes through time. Overall, the Virginia Barrier Islands lost ~3.4% (16 × 106 m3) of their 1887 C.E. volume between 1887 and 2017 C.E. The loss from three central islands (Parramore, Hog, and Cobb)—historically characterized by rotational behavior—was 43% (79 × 106 m3). In particular, Parramore Island continuously decreased in volume over the 20th and 21st centuries. In contrast, growth of Assateague and northern Wallops islands (located at the northern, updrift end of the island chain) from 1887 to 2017 C.E. resulted in a volume increase of ~59 × 106 m3. Whereas the Virginia Barrier Islands as a whole modestly decreased in size (and thus volume) directly in response to storm impacts and accelerating relative sea-level rise since the mid-1800s, the differential behavior of islands south of Assateague suggests more regional controls on coastal geomorphic behavior. Specifically, we identify the roles of antecedent substrate, sand trapping and changing wave-refraction patterns associated with the growth of Assateague Island, and inter-island sand exchanges in response to changing updrift barrier-scale behaviors. These findings help to better understand the underlying mechanisms behind state changes of barrier islands; in particular, the mechanisms by which geomorphic change along one barrier island influences those located several to tens of kilometers downdrift. This highlights the need to consider coastal beach and sand management over long reaches, even in systems which are largely unaffected by development, nourishment, and shoreline hardening. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural landscapes with a millennial-scale history of cultivation are common in many loess areas of central Europe. Over time, patterns of erosion and sedimentation have been continually modified via the variable imposition of anthropogenic discontinuities and linkages on fragmented hillslope sediment cascades, which eventually caused the complicated soilscape pattern. These field records challenge topographically oriented models of hillslope erosion and simple predictions of longer-term change of spatial soilscape by cultivation activities. A thorough understanding how soilscape patterns form in the long-term, however, is essential to develop spatial concepts of the sediment budget, particularly for the spatial modeling of anthropogenic hillslope sediment flux using GIS. In this study I used extensive datasets of anthropogenic soil truncation and burial in a typical undulating loess watershed in southern Germany (10 km2, Wetterau Basin, N of Frankfurt a.M.). Spatial soilscape properties and historic sediment flux, as caused by cultivation over seven millennia, were evaluated by these data. The soilscape pattern on the low-gradient hillslopes of the study area was found to be marked by a statistical near-random pattern of varying depth (thickness) of truncation and overthickened burial. Moreover, it was shown that truncation and burial had developed independently from each other and did not correlate with either hillslope gradient or downslope curvature. Hence, in the field any combination of (few) nearly preserved, severely truncated or completely removed soil profiles with either no, some or a thick sediment cover is present, thereby lacking an obvious spatial pattern. Here, I suggest putting long-term change of the soilscape into a contextual anthropogeomorphic systems perspective, that accommodates components of human-induced soil erosion operating at different spatial scales to interpret the longer-term spatial consequences at the hillslope-system level. In the study area, system scale linkages are marked by the spatial intersection of a finer-scaled managed field system with a broader hillslope-scale framework of ‘natural’ erosion controls. In the low-gradient study area, field borders exert control over the spatial reference of soil erosion and sedimentation sites. Over time, this brought about a growing historical and spatial contingency change to the soilscape, because of arbitrary spatial changes of the field system which are inherent in its socio-agricultural maintenance. Thus, the very low-gradient and low-erosivity setting of the study area have singled out the agency of human-induced spatial and connectivity controls and contingency for long-term spatial hillslope sediment flux. Although these findings may be less true for different settings, they allow for deriving a generic conceptual model of the linkages between ‘natural’ and anthropogenic subsystems to interpret the effects of long-term human-induced sediment flux. Accordingly, the resulting balance between on-hillslope net storage and net delivery to streams is scaling with basic physiographic properties of erosivity and sedimentation as well as the degree of anthropogenic hillslope fragmentation. For loess areas in Europe variable fields are fundamental anthropogeomorphic units that determine appropriate system scaling for historic sediment flux analysis and constrain retrodiction and prediction of changing fluxes at a point and a time at watershed scales. Methodical implications address adequate sampling strategies to record soilscape change, as a result of which a critical review of the applicability of the catena concept to long-cultivated hillslopes in central Europe was included. Finally, the suggested refined generic model of long-term, human-controlled sediment flux involves a number of research opportunities, particularly for linking modeling approaches to long-term field records of cultivation-related change in the soilscape. [Copyright &y& Elsevier]

Abstract: The sediment flux generated by postglacial channel incision has been calculated for the 2150 km2, non-glacial, Waipaoa catchment located on the tectonically active Hikurangi Margin, eastern North Island, New Zealand. Sediment production both at a sub-catchment scale and for the Waipaoa catchment as a whole was calculated by first using the tensioned spline method within ARC MAP to create an approximation of the aggradational Waipaoa-1 surface (contemporaneous with the Last Glacial Maximum), and second using grid calculator functions in the GIS to subtract the modern day surface from the Waipaoa-1 surface. The Waipaoa-1 surface was mapped using stereo aerial photography, and global positioning technology fixed the position of individual terrace remnants in the landscape. The recent discovery of Kawakawa Tephra within Waipaoa-1 aggradation gravels in this catchment demonstrates that aggradation was coincidental with or began before the deposition of this 22600 14C-year-old tephra and, using the stratigraphic relationship of Rerewhakaaitu Tephra, the end of aggradation is dated at ca 15000 14C years (ca 18000 cal. years BP). The construction of the Waipaoa-1 terrace is considered to be synchronous and broadly correlated with aggradation elsewhere in the North Island and northern South Island, indicating that aggradation ended at the same time over a wide area. Subsequent downcutting, a manifestation of base-level lowering following a switch to postglacial incision at the end of glacial-age aggradation, points to a significant Southern Hemisphere climatic warming occurring soon after ca 15000 14C years (ca 18000 cal. years BP) during the Older Dryas interval. Elevation differences between the Waipaoa-1 (c.15 ka) terrace and the level of maximum channel incision (i.e. before aggradation since the turn of the 20th century) suggest about 50% of the topographic relief within headwater reaches of the Waipaoa catchment has been formed in postglacial times. The postglacial sediment flux generated by channel incision from Waipaoa catchment is of the order of 9.5 km3, of which ~6.6 km3 is stored within the confines of the Poverty Bay floodplain. Thus, although the postglacial period represented a time of high terrigenous sediment generation and delivery, only ~30% of the sediment generated by channel incision from Waipaoa catchment probably reached the marine shelf and slope of the Hikurangi Margin during this time. The smaller adjacent Waimata catchment probably contributed an additional 2.6 km3 to the same depocentre to give a total postglacial sediment contribution to the shelf and beyond of ~5.5 km3. Sediment generated by postglacial channel incision represents only ~25% of the total sediment yield from this landscape with ~75% of the estimated volume of the postglacial storage offshore probably derived from hillslope erosion processes following base-level fall at times when sediment yield from these catchments exceeded storage. [Copyright &y& Elsevier]

Abstract: The dramatic lake level drop of the Dead Sea during the twentieth century (∼30 m) provides a field-scale experiment in transport-limited incision of gravel-bed channels in response to quasi-continuous base level fall at approximately constant rate. We apply a one-dimensional numerical incision model based on a linear diffusion equation to seven ephemeral channels draining into the Dead Sea. The model inputs include the measured twentieth century lake level curve, annual shoreline location (i.e., annual channel lengthening following the lake level drop), reconstructed longitudinal profiles of each of the channels based on mapped and surveyed terraces, and the current profiles of the active channels. The model parameters included the diffusion coefficient and the upstream-derived sediment flux. Both were first calibrated using a set of longitudinal profiles of known ages and then validated using additional sets of longitudinal profiles. The maximum at-station total incision observed at each of the studied channels was significantly less then the total lake level drop and varied in response to both drainage area and lake bathymetry. The model applied predicted degradation rates and the pattern of degradation with high accuracy. This suggests that sediment flux in the modeled channels is indeed linearly dependent on slope. Further support for this linear dependency is provided by a linear correlation between the diffusion coefficient and the mean annual rain volume over each basin (a proxy for discharge). The model presented could be a valuable tool for planning in rapid base level fall environments where incision may risk infrastructure. [Copyright &y& Elsevier]

Abstract: (Dis)connectivity within and between landscape compartments affects the extent and rate of transfer of energy and matter through catchments. Various landforms may impede sediment conveyance in a river system, whether laterally to the channel (termed buffers) or longitudinally along the channel itself (termed barriers). A generic approach to analysis of landscape (dis)connectivity using slope threshold analysis in GIS, tied to air photograph interpretation and field mapping of buffers and barriers, is tested in the upper Hunter catchment, Australia. Under simulated conditions, effective catchment area, which is a measure of the proportion of a catchment that has the potential to contribute sediment to the channel network, varies from 73% to just 3% of the total catchment area for differing subcatchments in the upper Hunter. This variability can be explained by the spatial distribution and assemblage of buffers and barriers in each subcatchment. Multiple forms of disconnectivity are evident in some subcatchments, such that when one buffer or barrier is breached, other features still impede sediment transfer within the system. The importance of the position of buffers and barriers within any given subcatchment is emphasised. Spatial variability in valley width exerts a critical control on catchment connectivity, with more efficient sediment conveyance in narrow valleys relative to wider valleys characterised by piedmonts, terraces, fans and extensive floodplains in which conveyance is impeded. This variability reflects the landscape history and geological setting of each subcatchment. The framework developed in this paper can be used to assess the impact of natural or human-induced buffers and barriers on catchment-scale sediment flux in any landscape setting, providing a physical template atop which other biogeochemical fluxes could be examined. [Copyright &y& Elsevier]

Abstract: The paper presents an overview of recent publications on the fluvial suspended sediment flux to the Arctic Ocean. The total suspended matter exported from the Russian territory is 102×106 t/year and from the Canadian Arctic is 125×106 t/year. The total suspended matter (TSM) flux to the Arctic (227×106 t/year) is very low, only about 1% of the global flux. Mean concentrations of suspended matter and specific sediment discharge are approximately one order of magnitude lower than the global concentration. An analysis of the trends in the sediment loads based on records of up to 62 years in length shows decreases (Yenisey), increases (Kolyma) and stability (Ob). Among the reasons for the very low concentrations and fluxes of suspended sediment in the Arctic rivers are thin weathering crusts on the Arctic watersheds, low precipitation, extensive permafrost, low temperatures for most of the year, large areas of swamps and lakes and a low level of human activity. A stochastic sediment transport model by Morehead et al. [Morehead, M.D., Syvitski, J.P., Hutton, E.W., Peckham, S.D., 2003. Modeling the temporal variability in the flux of sediment from ungauged river basins. Glob. Planet. Change 39, 95–110] is applied to the Arctic rivers to estimate the sediment load increase should the surface temperature of the drainage basin increase. For every 2 °C of warming a 30% increase in the sediment flux could result and for each 20% increase in water discharge, a 10% increase in sediment load could follow. Based on this model, an increase of the sediment flux of six largest arctic rivers (Yenisey, Lena, Ob, Pechora, Kolyma and Severnaya Dvina) is predicted to range from 30% to 122% by 2100. [Copyright &y& Elsevier]

Abstract: Preliminary results of modeling of annual variability in suspended particle matter (SPM) in Lake Baikal are presented together with outline of major present-day sedimentary environments, and variation in sedimentation patterns in drilled sections (spanning several million years) from the lake. The model predicts the SPM concentration, sedimentation, resuspension, mixing and mineralization in the lake on a monthly basis, using parameters describing the lake geometry and the climate in the catchment. Results of the modeling are generally in agreement with empirical data and indicate that the model accounts well for the relatively large volume and variable conditions occurring in Lake Baikal. The model also seems to have large potential in predicting variability of sediment flux and mass balance in the lake in the past. [Copyright &y& Elsevier]

This paper explores the effects of hillslope mobility on the evolution of a 10-km2 drainage basin located at the northern border of the Swiss Alps. It uses geomorphologic maps and the results of numerical models that are based on the shear stress formulation for fluvial erosion and linear diffusion for hillslope processes. The geomorphic data suggest the presence of landscapes with specific cross-sectional geometries reflecting variations in the relationships between processes in channels and on hillslopes. In the headwaters, the landscape displays parabolic cross-sectional geometries indicating that mass delivered to channels by hillslope processes is efficiently removed. In the trunk stream portion, the landscape is (i) V-shaped if the downslope flux of mass is balanced by erosion in channels (i.e. if mass delivered to channels by hillslope processes is efficiently removed) and (ii) U-shaped if in-channel accumulation of hillslope-derived material occurs. This latter situation indicates a non-balanced mass flux between processes in channels and on hillslopes.Information about the spatial pattern of the postglacial depth of erosion allows comparative estimates to be made about the erosional efficiency for the various landscapes that were mapped in the study area. The data suggest that the erosional potential and sediment discharge are reduced for the situation of a non-balanced mass flux between processes in channels and on hillslopes. These findings are also supported by the numerical model. Indeed, the model results show that high hillslope mobility tends to reduce the hillslope relief and to inhibit dissection and formation of channels. In contrast, stable hillslopes tend to promote fluvial incision, and the hillslope relief increases. The model results also show that very low erosional resistance of bedrock promotes backward erosion and steepening of channel profiles in headwaters. Beyond that, the model reveals that sediment discharge generally increases with decreasing erosional resistance of bedrock, but that this increase decays exponentially with increasing magnitudes of fluvial and hillslope mobilities. Very high hillslope diffusivities even tend to reduce the erosional potential of the whole watershed. It appears that besides rates of base-level lowering, factors limiting sediment discharge might be the nonlinear relationships between processes in channels and on hillslopes. [Copyright &y& Elsevier]

Over the last decades, animal activity has been explored and reported as a potential source of natural hazards, such as the destruction of a beaver dam potentially triggering a flash flood downriver. However, the sediment source or sediment budget related to animal activity has received very little attention from geoscientists to date. The main goal of this study is to quantify the biogenic activity of the European snow vole (Chionomys nivalis) as a sediment source in the subalpine prairies of the Parâng Mountains, Southern Carpathians. Only the direct action of this rodent was analyzed, namely the spatial distribution and frequency of burrowing, quantitative analysis of the mounds, and rate of sediment excavation and mass transfer caused by burrowing and tunnel digging. To do this, 838 burrows and mounds were mapped and measured in eleven plots, and excavated volumes of sediment and mass transfers were calculated following three approaches: 1) measuring the weight of excavated debris; 2) measuring the dimensions of excavated debris; and 3) measuring burrow dimensions. The fieldwork revealed three preferred aspects: south, southeast, and west. The amount of displaced soil was highly variable depending on the approach used, ranging from 3.41 m3/ha to 21.08 m3/ha. As such, snow vole biogenic activity, which is due to the long-term opening of the landscape for traditional transhumance and sheep farming, should be considered to be an important sediment source in the subalpine and alpine prairies of the Parâng Mountain. • Chionomys nivalis is a significant geomorphic agent in the subalpine prairies. • Sediment and mass transfers are highly variable depending of the approach used. • Burrows and mounds have short landscape residence time. [ABSTRACT FROM AUTHOR]

Highest geomorphic activity in the central Nepal Himalayas is mainly driven by monsoonal precipitation. In contrast, the northern flanks of the Nepal Himalaya lay in the relative dry rain shadow of the mountain range. During the monsoon 2018, major floods and geomorphic events occurred in the Kali Gandaki (KG) valley impacting both the monsoon-affected and the dry parts of the catchments. We analyze the events and its triggers based on field observations, multiple satellite image interpretation, climatological analysis using Global Precipitation Measurement and MODIS snow cover data, hydrological analysis and media analysis. The hydro-meteorological triggers are complex. Exceptional precipitation in April and May 2018 occurred in the entire study area, followed by a rather dry period. Precipitation in August was exceptional in the northern part whereas below average in the South. We argue that dynamics of snow accumulation and delayed melting contributed significantly to flooding and increased geomorphic activity in the southern part in August whereas flooding in the northern part was mainly triggered by rainfalls. We thus define 2018 as an abnormal (pre-)monsoon year with less rainfall than average but being more catastrophic. Sediment dynamics in the study area are still controlled by the Dhampu rock avalanche dam and the braided river floodplain north of this knickpoint, where sediment pulses delivered from tributaries are rarely connected from the main river. During the monsoon floods 2018 sediment connectivity was given for most tributaries due to the steepness of the catchments. The study area is subject to major human impact. Mostly in the south, numerous hillslopes have been undercut by road construction, leading to higher geomorphic sensitivity. Severe landslides might thus be triggered in future even by less intense rainfall events. Magnitude and frequency of such abnormal (pre-)monsoon precipitation are highly relevant for sediment flux and natural hazards studies. Unlabelled Image • The year 2018 was an abnormal (pre-)monsoon year. • Below average precipitation caused yet more disastrous geomorphic events. • Exceptional snow falls in spring and delayed melting were essential drivers. • Magnitude/frequency of such years are relevant for sediment flux/natural hazards. [ABSTRACT FROM AUTHOR]