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Rapid urbanization has an accelerated impact on catchment hydrology and geomorphology due to land use and land cover changes as a result of anthropogenic development activities in river catchment areas that cause increased surface runoff and higher sediment yield. The present study investigates the channel changes and sediment transport phenomena, including bed material movement from the upstream to the estuaries of the Pahang River Basin, Peninsula Malaysia. The river geometry survey associated with the spatial variation in sediment transport has confirmed that changes in river bed profile occur due to the erosion and sediment deposition along the Pahang River. The sediment size distribution for the Pahang River was very coarse sand and gravel after the December 2014 flood. The river geometry survey showed a gentle slope that can induce lower discharge typical of alluvial rivers relating to flood events. Quantitative assessment of sediment load is, therefore, of critical importance for future river basin management. [ABSTRACT FROM AUTHOR]

The battering of bedrock by bedload collisions is the primary mechanism by which bedrock rivers erode and landscapes evolve. The energy imparted via impacts acts to detach bedrock via the growth and intersection of surface fractures. We present impact experiments designed to test the influence of particle impact energy on bedrock erosion rates. We found that erosional efficiency increased with increasing impact energy. Notably, these increases in efficiency are not captured by a widely‐used mechanistic bedrock erosion model. Observed increases in erosional efficiency were linked with enhanced elastic energy dissipation captured by differences in the coefficient of restitution. We suggest that this increase in energy dissipation is indicative of enhanced crack extension for high velocity impacts. Our experiments indicate a clear energy‐dependence for bedrock detachment processes that is not yet captured by bedrock incision models but may be integrated into long‐term erosion rates and landscape evolution. Plain Language Summary: Bouncing sediment grains batter the bedrock beds of rivers during floods. As these impacts collide with the bed, they slowly chip away at the riverbed bedrock. It's perhaps intuitive that a grain with more energy when it collides with the riverbed is able to chip away more bedrock. But, how much more destructive are these high energy impacts? We designed an experiment where we hit a bedrock sample with a steel ball at a range of impact energies, over and over again, up to 30,000 times, and measured how much material was chipped away. High energy impacts eroded more material, but this increased efficiency of erosion is not fully captured by impact‐based erosion models. We hypothesize that for higher energy impacts, a larger fraction of the incoming energy is used to crack the bedrock, more easily eroding material. We liken the relative influence of these high energy impacts to a battering ram, where only a few strikes can easily break down a door, whereas lower energy impacts, similar to a simple knock, are unlikely to achieve the same result. We suggest that this effect may be important in determining the influence of extreme events on bedrock erosion over long timescales. Key Points: Impact experiments demonstrate that bedrock erosional efficiency is enhanced with increasing impact energyExperimentally‐derived coefficients of restitution and rock resistance coefficients indicate enhanced elastic energy dissipation with increasing impact energyResults suggest that more energetic impacts enhance crack extension, increasing erosional efficiency [ABSTRACT FROM AUTHOR]

Research in fluvial biogeomorphology largely aims to promote our understanding of the interactions between riparian vegetation and fluvial morphodynamics within riverine ecosystems. Starting at the end of the last century, Angela M. Gurnell has made a major contribution to fluvial geomorphology by considering water flow and sediment transport in combinaton with riparian and later also aquatic vegetation and thus significantly promoting the fluvial biogeomorphological approach from its early days until today. The objective of the present paper is to present a set of studies and results obtained over the last 20 years mainly by the authors and many collaborators, including Angela M. Gurnell, on a panel of French rivers: the Tech, Garonne, Isère and Allier. In particular, feedback mechanisms between fluvial morphodynamics and riparian vegetation dynamics were investigated directly in the field and by using high‐resolution remote sensor systems at the scale of individual plants, populations, communities and landscapes as well as during semi‐controlled ex‐situ experiments at the scale of individual plants. Collectively, the authors' research conducted over the past 20 years has helped to elucidate some key aspects of the feedback dynamics between the lowest and highest levels of the riparian ecosystem organization. This article reviews and discusses those key aspects. The gradually obtained results have contributed to a better understanding and quantification of feedback between river morphodynamics and vegetation at nested spatiotemporal scales, from plant species traits to the riverine landscape. Furthermore, the biogeomorphological approach advocated for more than 20 years now has clearly facilitated the extension of the discipline of geomorphology to ecology in general and evolutionary ecology in particular and thus contributed to a more integrative vision of earth surface processes. [ABSTRACT FROM AUTHOR]

Sedimentary records of Ri-Yue Tang (Sun Moon Lake), which is the largest lake in Taiwan, provide valuable hydro-environmental information during the past 15,000 years. From the viewpoint of hydro-geomorphological conditions, the interval is roughly divided into four stages: (i) high water level with large artificial water inflow (1934 AD–present), (ii) low water level with a comparatively large catchment area (1919 AD–ca. 2800 years BP), (iii) frequent high water level with a small catchment area (ca. 2800–ca. 13,500 years BP), and (iv) low water level with a comparatively large catchment area (ca. 13,500–15,000 years BP). The changes in the conditions are mainly shown in the physical properties. A small mineral grain size and large grain density suggest enough water with high water level while large grain size and small density imply low water level and limited water discharge. Dam construction (1919–1934 AD) for more water supplies to the newly established power station greatly influences the hydro-geomorphological and environmental conditions in the Ri-Yue Tan lake-catchment system. Additional artificial water inflow with mineral material through the waterway from the Wujie Reservoir has transported more sediments (roughly twice) after the dam construction. The increase in water level due to the dam construction caused water-area enlargement and catchment-area shrinkage, resulting in changes in material production (erosion), transportation, and sedimentation in the original system. The increase in water amount supplied from the reservoir is also printed in the physical properties (small mineral grain size and large grain density) and chemical properties (organic, HCl soluble, and bi-SiO2 contents) of lacustrine sediments. [ABSTRACT FROM AUTHOR]

Boulders are globally widespread and influence processes across many landscapes including hillslopes, coasts, rivers and extra‐terrestrial settings. Boulders are described as particles, sufficiently large, that they have a disproportionate effect on the surrounding landscape. Moving beyond this conceptual definition, however, requires a somewhat arbitrary decision of how to define a minimum boulder size. The implications of boulder definition on study findings are rarely considered. We investigate the suitability of five boulder definitions, two based on fixed sizes: (1) 0.26 m and (2) 1 m, and three definitions which vary based on system characteristics: (3) grain mobility, (4) grain protrusion and (5) surface grain size distribution (> 84th percentile, D84). We consider the impact of definition on calculated boulder metrics, and, for the >1m and >D84 definitions, their association with channel and catchment characteristics across 20 boulder‐bed streams in northern Sweden. We also surveyed river managers responsible for restoring these rivers, to gain a practitioner insight on boulder size definition. We found that boulder definition matters; for metrics relating to the number or density of boulders, the >D84 and >1m size definitions were negatively correlated. Surveys indicated the importance of communicating boulder definition. We conclude that, whilst the best choice of boulder size definition will vary based on the questions of interest and techniques employed, evaluating the implications of the chosen boulder size definition and communicating the reasoning behind boulder definition choice is crucial. [ABSTRACT FROM AUTHOR]

River channels, riparian and floodplain forms and dynamics are all influenced strongly by biological processes. However, the influence of macroinvertebrates on entrainment and transport of river sediments remains poorly understood. We use an energy‐based approach to explore the capacity of benthic animals to move surficial, gravel‐bed particles in field and laboratory settings and use the results to assess the relative significance of biological and physical benthic processes. Our results showed that in 11 British gravel‐bed rivers, the maximum energy content (i.e., calorific content) of macroinvertebrate communities generally matched the flow energy associated with median discharges and, at multiple sites, exceeded that of the 10‐year return interval flood. A series of laboratory experiments used to estimate the minimum energy expended by signal crayfish (Pacifastacus leniusculus) when performing geomorphic work established that crayfish move gravel particles at energy levels below that expected of the flow, complicating direct comparisons of the capacity for macroinvertebrates and fluvial flows to influence bed mobility. Our findings suggest that the influence of macroinvertebrate communities in either promoting or suppressing, the mobilisation of the bed may be large compared to equivalent values of fluvial energy. Based on these findings, we conclude that in the gravel‐bed rivers studied, the macroinvertebrate community's potential to perform geomorphic work matches or exceeds the stream power during most of the year. Although our study examined biological and fluvial energy systems separately, it is important to recognise that in nature, these systems are highly interactive. It follows that utilising the energy framework presented in this paper could lead to rapid advances in both fluvial biogeomorphology and river management and restoration. [ABSTRACT FROM AUTHOR]

Hydrogeomorphology studies river dynamics, focusing on the interactions between flow structure, sediment transport, and the morphologies that characterize rivers and their watersheds. It provides an analytical framework and tools for better integrating knowledge of river dynamics into river management in the broadest sense, and more specifically, into river restoration as well as into the assessment and prevention of risks associated with fluvial hazards. In Quebec, hydrogeomorphology is emerging as a significant contribution to risk assessment and management approaches, and is at the heart of a paradigm shift in river management whereby process restoration aims to increase the resilience of fluvial systems and societies, and improve the quality of fluvial environments. This contribution outlines the trajectory of hydrogeomorphology in Quebec, based on scientific publications by Quebec geographers, and discusses the discipline's aims in research and knowledge integration for river management. Messages clés: Les géographes du Québec ont contribué fortement au développement des connaissances et outils de l'hydrogéomorphologie.L'hydrogéomorphologie a évolué d'une science fondamentale à une science où les connaissances fondamentales sont au service de la gestion des cours d'eau.L'hydrogéomorphologie et le cortège de connaissances et d'outils qu'elle promeut font de cette discipline une partenaire clé pour une gestion holistique des cours d'eau. [ABSTRACT FROM AUTHOR]

Mount Meager is a deeply eroded quaternary volcanic complex located in southwestern British Columbia (BC) and is known for its frequent large landslides. In 2010, the south face of Mount Meager collapsed, generating a long-runout debris avalanche that was one of the largest landslides (50 × 106 m3) in Canadian history. Over the past 14 years, the landslide deposit has been reworked by stream action, delivering large amounts of sediment to Lillooet River, just downstream. In this study, we investigate 10 years of geomorphic evolution of the landslide deposit using orthophotos and digital elevation models (DEMs) generated using Structure from Motion (SfM) photogrammetry on aerial photographs acquired during unmanned aerial vehicle (UAV) and Global Navigation Satellite System (GNSS) surveys. The SfM products were used to produce a series of precise maps that highlight the geomorphological changes along the lower Meager Creek within the runout area of the landslide. Comparison of DEMs produced from 2010, 2012, 2015, and 2019 imagery allowed us to calculate deposit volume changes related to erosion, transport, and redeposition of landslide material. We estimate that about 1.1 × 106 m3 of sediment was eroded from the landslide deposit over the period 2015–2019. About 5.2 × 105 m3 of that sediment was redeposited inside the study area. About 5.8 × 105 m3 of sediment, mainly sand, silt, and clay, were exported from the study area and are being carried by Lillooet River towards Pemberton, 40 km from Mount Meager, and farther downstream. These remobilized sediments likely reduce the Lillooet River channel capacity and thus increase flood hazards to the communities of Pemberton and Mount Currie. Our study indicates a landslide persistence in the landscape, with an estimated 47-year half-life decay, suggesting that higher flood hazard conditions related to increased sediment supply may last longer than previously estimated. This study shows the value of using SfM in tandem with historic aerial photographs, UAV photos, and high-resolution satellite imagery for determining sediment budgets in fluvial systems. [ABSTRACT FROM AUTHOR]

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As climate warms, hydrology and geomorphology in glacierized catchments are evolving, changing sediment export from these catchments, thus impacting downstream ecosystems and communities. Currently, much uncertainty persists regarding interactions among geomorphic processes that evacuate sediment from glacierized catchments. Here, we present a catchment‐scale numerical model of subglacial and proglacial sediment transport with debris meltout processes. We apply the model in a Monte Carlo framework to suspended sediment data collected over 2014–2020 from the Fieschertal catchment in the Swiss Alps, assessing possible combinations of geomorphic processes responsible for suspended sediment discharge. The ensemble of model outputs quantifies the interaction of different geomorphic processes, including the trade‐off between bedrock erosion and sediment previously stored in the catchment. Model runs suggest that, at some periods, up to 20% of the sediment leaving the glacier is deposited in the proglacial area relative to the catchment's total sediment discharge. This shows that the model captures the proglacial area change from sediment source to sediment sink in different hydrological and glaciological conditions. Furthermore, the findings highlight the impact of glacier retreat on the catchment's sediment dynamics, which both reduces the proglacial area's slope and introduces additional sediment to the proglacial area through debris meltout. The model outputs and the parameters quantify the interaction among geomorphic processes, yielding key insights into the drivers of sediment transport in alpine regions. The implications of these interactions are discussed in the context of interpreting processes responsible for controlling erosion rates from glacierized regions and modeling sediment transport in glacierized catchments. Key Points: We present a numerical model of sediment transport in a glacierized catchment and apply it to a 7‐year record of suspended sediment exportMonte Carlo application of the physically‐based model demonstrates the importance of different geomorphic processesModel outputs show the interactions amongst sediment mobilization and deposition, and debris meltout in the catchment's sediment discharge [ABSTRACT FROM AUTHOR]

Abstract The battering of bedrock by bedload collisions is the primary mechanism by which bedrock rivers erode and landscapes evolve. The energy imparted via impacts acts to detach bedrock via the growth and intersection of surface fractures. We present impact experiments designed to test the influence of particle impact energy on bedrock erosion rates. We found that erosional efficiency increased with increasing impact energy. Notably, these increases in efficiency are not captured by a widely‐used mechanistic bedrock erosion model. Observed increases in erosional efficiency were linked with enhanced elastic energy dissipation captured by differences in the coefficient of restitution. We suggest that this increase in energy dissipation is indicative of enhanced crack extension for high velocity impacts. Our experiments indicate a clear energy‐dependence for bedrock detachment processes that is not yet captured by bedrock incision models but may be integrated into long‐term erosion rates and landscape evolution.

Despite geomorphic processes being increasingly recognized as a vital component of river management projects, evidence suggests that they may not be adequately captured in common river assessment procedures. We reviewed 91 river assessment procedures from around the world to evaluate their effectiveness in capturing geomorphic processes relevant for river management goals. Our objectives were to summarize which common geomorphic indicators are measured and how in different types of river assessments categorized based on their main focus: geomorphic, physical habitat, mixed geomorphic and habitat, and hydromorphology. Our analysis identified differences in the types of geomorphic indicators included and measurement methodologies between the types of assessment procedures. Some geomorphic processes, such as sediment transport, are nearly completely absent from all assessments, despite their importance for geomorphic processes. The variability among assessment procedures suggests that a single procedure is unlikely to capture all geomorphic components required to support every river management programs. Here, we discuss how the strengths and limitations of different assessment types can be used to guide decisions around how to select assessments and geomorphic indicators to support management project goals. A companion paper expands the discussion of how to plan effective river assessment procedures to support unique management goals. [ABSTRACT FROM AUTHOR]

Mount Meager is a deeply eroded quaternary volcanic complex located in southwestern British Columbia (BC) and is known for its frequent large landslides. In 2010, the south face of Mount Meager collapsed, generating a long-runout debris avalanche that was one of the largest landslides (50 × 106 m3) in Canadian history. Over the past 14 years, the landslide deposit has been reworked by stream action, delivering large amounts of sediment to Lillooet River, just downstream. In this study, we investigate 10 years of geomorphic evolution of the landslide deposit using orthophotos and digital elevation models (DEMs) generated using Structure from Motion (SfM) photogrammetry on aerial photographs acquired during unmanned aerial vehicle (UAV) and Global Navigation Satellite System (GNSS) surveys. The SfM products were used to produce a series of precise maps that highlight the geomorphological changes along the lower Meager Creek within the runout area of the landslide. Comparison of DEMs produced from 2010, 2012, 2015, and 2019 imagery allowed us to calculate deposit volume changes related to erosion, transport, and redeposition of landslide material. We estimate that about 1.1 × 106 m3 of sediment was eroded from the landslide deposit over the period 2015–2019. About 5.2 × 105 m3 of that sediment was redeposited inside the study area. About 5.8 × 105 m3 of sediment, mainly sand, silt, and clay, were exported from the study area and are being carried by Lillooet River towards Pemberton, 40 km from Mount Meager, and farther downstream. These remobilized sediments likely reduce the Lillooet River channel capacity and thus increase flood hazards to the communities of Pemberton and Mount Currie. Our study indicates a landslide persistence in the landscape, with an estimated 47-year half-life decay, suggesting that higher flood hazard conditions related to increased sediment supply may last longer than previously estimated. This study shows the value of using SfM in tandem with historic aerial photographs, UAV photos, and high-resolution satellite imagery for determining sediment budgets in fluvial systems.

Reliable forecasts of building damage due to debris flows may provide situational awareness and guide land and emergency management decisions. Application of debris-flow runout models to generate such forecasts requires combining hazard intensity predictions with fragility functions that link hazard intensity with building damage. In this study, we evaluated the performance of building damage forecasts for the 9 January 2018 Montecito postfire debris-flow runout event, in which over 500 buildings were damaged. We constructed forecasts using either peak debris-flow depth or volume flux as the hazard intensity measure and applied each approach using three debris-flow runout models (RAMMS, FLO-2D, and D-Claw). Generated forecasts were based on combining multiple simulations that sampled a range of debris-flow volume and mobility, reflecting typical sources and magnitude of pre-event uncertainty. We found that only forecasts made with volume flux and the D-Claw model could correctly forecast the observed number of damaged buildings and the spatial patterns of building damage. However, the best forecast only predicted 50% of the observed damaged buildings correctly and had coherent spatial patterns of incorrectly forecast building damage (i.e., false positives and false negatives). These results indicate that forecasts made at the building level reliably reflect the spatial pattern of damage, but do not support interpretation at the individual building level. We found the event size strongly influences the number of damaged buildings and the spatial pattern of debrisflow depth and velocity. Consequently, future research on the link between precipitation and the volume of sediment mobilized may have the greatest effect on reducing uncertainty in building damage forecasts. Finally, because we found that both depth and velocity are needed to forecast building damage, comparing debris flow models against spatially distributed observations of building damage is a more stringent test for model fidelity than comparison against the extent of debris-flow runout. [ABSTRACT FROM AUTHOR]

The interaction of sedimentary systems with oceanographic processes in deep‐water environments is not well understood yet, despite its importance for palaeoenvironmental reconstructions, and for a full understanding of source‐to‐sink sediment transport. The aim of this study is to improve the understanding of how contourite moats, elongated depressions formed by bottom currents associated with contourite drifts, develop and of the link between moat‐drift system morphology and bottom current dynamics. This study provides a systematic comparison of 185 cross‐sections of moat‐drift systems distributed at 39 different locations worldwide, and a detailed analysis of the morphology of six moats that cover a wide range of typical geological and hydrodynamic settings. Additionally, in situ measured current data were analysed to better link hydrodynamics to moat morphology. The median of all profiles across all moat‐drift systems reveals a 50 m relief, a width of 2.3 km, a relief to width ratio of 0.022, a slope angle of 6°, a drift angle of 3° and a concave‐up shaped morphology. Moats can be over 100 km long. Some moats are driven by sediment erosion while others are depositional and primarily exist due to differential sedimentation inside the moat compared to the drift alongside the moat. A new sub‐classification of moat‐drift systems based on their stratigraphy is proposed. This classification distinguishes moats depending on the degree of erosion versus deposition. No relation is found between latitude and moat‐drift morphology or stratigraphy in the analysed examples. The combined data indicate that a steeper slope focuses the current more than a gentle slope, resulting in an increase of the relief–width ratio and drift angle. Thus, this study provides new insights into the interaction of ocean currents with sedimentary morphology, which thereby affects the evolution of a poorly understood deep‐water sedimentary system. [ABSTRACT FROM AUTHOR]

Natural channel design (NCD) and analytical channel design (ACD) are two competing approaches to stable channel design that share fundamental similarities in accounting for sediment transport processes with designs based on hybrid fluvial geomorphology and hydraulic engineering methods. In this paper, we highlight the linkage between ACD's capacity/supply ratio (CSR) and NCD's sediment capacity models (FLOWSED/POWERSED), illustrating how ACD and NCD have reached a point of convergent evolution within the stream restoration toolbox. We modified an existing CSR analytical spreadsheet tool which enabled us to predict relative channel stability using both conventional bed load transport equations and regional sediment regression curves. The stable channel design solutions based on measured data most closely matched the Parker (ACD) and/or Pagosa good/fair (NCD) relationships, which also showed the greatest CSR sensitivity in response to channel alterations. We found that CSR differences among the transport relationships became more extreme the further the design width deviated from the supply reach, suggesting that a stable upstream supply reach may serve as the best design analog. With this paper, we take a step toward resolving lingering controversy in the field of stream restoration, advancing the science and practice by reconciling key differences between ACD and NCD in the context of reach scale morphodynamics. [ABSTRACT FROM AUTHOR]

This study aimed to characterize the sedimentary facies and understand the morphodynamics of the study area, and their results were correlated with various analytical methods. Different analyses such as depositional environmental, statistical, shoreline change, and grain size illustrated the temporal and spatial distribution of sediments. It has previously been claimed that current research locations are locii to fluvial landforms and are affected by fluvial processes. However, there are currently no rivers in the study region. This study was done to better understand the presence of fluvial landforms and to evaluate the previous findings. The dynamic behavior of the coast was revealed through shoreline analysis, which was done using satellite images from various years. Oceanographic parameters and longshore sediment transport play a vital role in geomorphological changes in coastal zones. According to the grain size analysis results, mean values showed that the deposits predominantlyare medium grained. The outcome discussed the spatiotemporal variations in geomorphology, sedimentation, and the function of coastal and fluvial processes on the beach of an island and a sand spit. Also highlighted was the role that wave action, fluvial currents, and tidal currents had in the long-term evolution of coastal geomorphological features such as spits, beaches, open coasts, and islands. The standard deviation signifies that the sediments are very well sorted to poorly sorted. Skewness ranges from fine skewed to strongly fine skewed and the kurtosis values show that the sediments are predominately very platykurtic which implies a low-energy environment of deposition. Four sedimentary facies (Facies A, B, C, D) have been found and facies A, B, and C may be wave-influenced deposits, but facies D may be formed by fluvial processes and contain medium to sand-sized particles. The direction of the tip area is also pointing to the south and this result concluded that the tip area is continuously growing. Thus, the results of this study revealed that sediment transport and coastal geomorphology evolution may be governed by two main processes such as the present ocean hydrodynamics and paleo fluvial processes of the study regions. [ABSTRACT FROM AUTHOR]

River profiles are shaped by climatic and tectonic history, lithology, and internal feedbacks between flow hydraulics, sediment transport and erosion. In steep channels, waterfalls may self‐form without changes in external forcing (i.e., autogenic formation) and erode at rates faster or slower than an equivalent channel without waterfalls. We use a 1‐D numerical model to investigate how self‐formed waterfalls alter the morphology of bedrock river longitudinal profiles. We modify the standard stream power model to include a slope threshold above which waterfalls spontaneously form and a rate constant allowing waterfalls to erode faster or slower than other fluvial processes. Using this model, we explore how waterfall formation alters both steady state and transient longitudinal profile forms. Our model predicts that fast waterfalls create km‐scale reaches in a dynamic equilibrium with channel slope held approximately constant at the threshold slope for waterfall formation, while slow waterfalls can create local channel slope maxima at the location of slow waterfall development. Furthermore, slow waterfall profiles integrate past base level histories, leading to multiple possible profile forms, even at steady‐state. Consistency between our model predictions and field observations of waterfall‐rich rivers in the Kings and Kaweah drainages in the southern Sierra Nevada, California, supports the hypothesis that waterfall formation can modulate river profiles in nature. Our findings may help identify how bedrock channels are influenced by waterfall erosion and aid in distinguishing between signatures of external and internal perturbations, thereby strengthening our ability to interpret past climate and tectonic changes from river longitudinal profiles. Plain Language Summary: Mountain rivers are shaped by tectonic and climatic forces; thus, the longitudinal profile of a river (a plot of river elevation vs. distance along the stream) can be used to investigate geologic history. Abrupt changes in river slope are often interpreted as signals of an external tectonic or climatic disruption. However, other factors may disrupt longitudinal profiles, including changes in rock type and differences in river erosion processes. Here, we investigate one such process: waterfalls formed by feedbacks between water flow, sediment transport and river‐bed erosion, and whether these waterfalls can alter longitudinal profiles without climatic or tectonic changes. We make a model to investigate what river profiles might look like if waterfalls naturally develop and alter erosion rates in all channels exceeding a specific slope threshold. Our model predicts that waterfalls generate distinct river profile features including a constant channel slope maintained over several kilometers where waterfalls occur and sharp increases in slope due to waterfall occurrence, both of which we have found in waterfall‐rich rivers in the southern Sierra Nevada, California. This research identifies similarities and differences between the impact of changes in tectonics and climate versus internal feedbacks such as self‐formed waterfalls on river profiles. Key Points: We investigate how erosion via self‐formed waterfalls alters river long profile form using a stream power model with a slope thresholdSelf‐formed waterfalls alter fluvial relief and concavity, create dynamic equilibriums, and, in cases, path‐dependent profile formsProfiles of rivers in the Sierra Nevada, California, with abundant waterfalls have similar features to our model [ABSTRACT FROM AUTHOR]

The climatic, hydrological, tectonic and topographic conditions of the Yarlung Tsangpo river basin in the south eastern margin of the Tibetan Plateau have the potential to develop super-large reservoir glaciers or landslide-dammed lakes that result in mega floods. The research progresses in the sedimentary characteristics of mega floods were briefly reviewed; by presenting widely distributed geomorphology and sedimentary evidence of mega floods in the Yarlung Tsangpo river basin, the main sedimentary characteristics and causes of mega flood sediments in the basin as well as their geomorphological response in the basin were summarized. The results show that eddy bars are the most common ones in the Yarlung Tsangpo river basin, followed by point bars and pendant bars, but expansion bars are absent; in terms of sedimentary characteristics, the well-sorted, horizontally laminated silt and coarse sand or granules are predominant in the internal sedimentary structure of giant bars; special sedimentary structures, including typical ripple and cross-lamination, silt bed, clinoforms and coarse parallel bedding can also be found sometimes. The evidence and previous studies show that extreme surface processes such as megafloods play a key role in sediment transport and landscape evolution over the Tibetan Plateau and the Yarlung Tsangpo river basin. [ABSTRACT FROM AUTHOR]

An estimated 20% of the world's land surface is underlain by lithologies favorable for karst formation. Karst features (e.g., sinkholes) and soils coevolve, likely influencing local pedogenesis, soil carbon storage, and hydrologic patterns. While karst is widespread, our understanding of the influence of karst geomorphology on pedogenesis remains limited. To better estimate the impact of karst geomorphology on pedogenesis, we characterized nine pedons as a function of landscape position (i.e., toposequence) in two subsidence sinkholes located in the Inner Bluegrass physiographic region of central Kentucky; we characterized a suite of soil physical, chemical, and mineralogical properties. The Inner Bluegrass is underlain by a phosphatic limestone and is susceptible to karst formation. Expectedly, total carbon was greater in lowland positions relative to upland landscape positions. However, inverse relationships between elevation and clay content, selective iron, aluminum, and silicon extracts contradicted previous toposequence trends. Clay mineralogy differences between toeslope and summit positions suggested sediment transport from summit to toeslope positions. Karst geomorphology may limit pedogenesis and facilitate more rapid material export through karst conduits compared to other lithologies. Given the extent of karst terrains and lithologies susceptible to karst formation, future work is needed to understand the magnitude of the impact of karst on pedogenesis and other earth system processes. Core Ideas: Sinkholes are common features in karst topography and have variable morphologies.Soil physical and chemical properties are variable between karst sinkholes.Typical toposequence trends may be reversed in sinkholes due to the impact of karst features. [ABSTRACT FROM AUTHOR]

Suspended sediment dynamics play an important role in controlling nearshore and estuarine geomorphology and the associated ecological environments. Modeling the transport of suspended sediment is a complicated and challenging research topic. The goal of this study is to improve the accuracy of modeling the suspended sediment concentrations (SSCs) with newly developed techniques. Based on a three-dimensional suspended cohesive sediment transport model, the transport of suspended sediment and SSCs are simulated by assimilating SSCs retrieved from the Geostationary Ocean Color Imager (GOCI) with the adjoint data assimilation in the Hangzhou Bay, a typical strong tidal estuary along the coast of the East China Sea. To improve the effect of the data assimilation, the penalty function method, in which the reasonable constraints of the estimated model parameters are added to the cost function as penalty terms, will be introduced for the first time into the adjoint data assimilation in the SSCs modeling. In twin experiments, the prescribed spatially varying settling velocity is estimated by assimilating the synthetic SSC observations, and the results show that the penalty function method can further improve the effect of data assimilation and parameter estimation, regardless of synthetic SSC observations being contaminated by random artificial errors. In practical experiments, the spatially varying settling velocity is firstly estimated by assimilating the actual GOCI-retrieved SSCs. The results demonstrate that the simulated results can be improved by the adjoint data assimilation, and the penalty function method can additionally reduce the mean absolute error (MAE) between the independent check observations and the corresponding simulated SSCs from 1.44 × 10−1 kg/m3 to 1.30 × 10−1 kg/m3. To pursue greater simulation accuracy, the spatially varying settling velocity, resuspension rate, critical shear stress and initial conditions are simultaneously estimated by assimilating the actual GOCI-retrieved SSCs to simulate the SSCs in the Hangzhou Bay. When the adjoint data assimilation and the penalty function method are simultaneously used, the MAE between the independent check observations and the corresponding simulated SSCs is just 9.90 × 10−2 kg/m3, which is substantially less than that when only the settling velocity is estimated. The MAE is also considerably less than that when the four model parameters are estimated to be without using the penalty function method. This study indicates that the adjoint data assimilation can effectively improve the SSC simulation accuracy, and the penalty function method can limit the variation range of the estimated model parameters to further improve the effect of data assimilation and parameter estimation. [ABSTRACT FROM AUTHOR]

CONCLUSIONS Despite the breadth and intensity of human impacts to lowland rivers it is essential that river managers have knowledge of fluvial dynamics in the context of historic and planned human impacts to rivers. Lowland rivers often have broad valleys and deltas characterized by multiple raised channel belts and distributaries separated by expansive flood basins. Lowland rivers are unique geomorphic and hydrologic settings that support distinctive environmental processes and a range of human activities. Study results raise important issues as regards management options for coastal draining lowland rivers along passive margins with broad lowland rivers undergoing high rates of sea level rise. [Extracted from the article]

The Port of Klaipėda, located at the Klaipėda strait, divides the Lithuanian coast into two different geomorphological parts: southern—the coast of the Curonian Spit, and northern—the mainland coast. Port jetties interrupt the main sediment transport path along the South-Eastern Baltic Sea's coast. Port of Klaipėda reconstruction in 2002 and the beach nourishment project which started in 2014 significantly influenced the northern part of the coast, which led to changes in the coastal zone evolution. The measurements in various periods are essential for cross-shore profile elevation to analyze seabed morphology and sedimentation patterns. These data highlight our understanding of the scale and timing of seabed erosion or sedimentation processes scale and timing. This study evaluates the impact of anthropogenic pressure and natural factors on coastal geomorphology and dynamics. In order to assess the latter changes, the cross-shore profile evolution and sediment budget were analyzed as well as nearshore bathymetry changes. The data illustrated a changing picture of the entire shore profile—on land and underwater. [ABSTRACT FROM AUTHOR]

Headwater streams play an essential role in catchment hydrogeomorphology while supplying water and sediment to downstream reaches along the channel network. Adaptive management strategies which require ecological rehabilitation and natural hazards prevention methods are increasingly needed to sustain ecological services provided by headwater streams. However, environmentally sound and economically effective stream management techniques depend on relevant information on boundary conditions, operating processes and evolutionary trajectories of a river system, which are often unavailable. Therefore, it is desirable to provide river managers with scientifically rigorous, yet easy to apply tools (methods) to assess channel and catchment conditions. The present paper focuses specifically on the sediment supply and transport (SST) regime, a crucial component of the fluvial system and a source of significant hazard to people and infrastructures. The SST hazard and risk assessment procedure was developed for small headwater streams with a catchment area of up to ca. 50 km2. The method comprises two core modules. Module 1 is designed to rapidly evaluate susceptibility to SST hazard based on four catchment variables (relief, lithology, erosion-prone surfaces, and connectivity). Module 1 is intended primarily for river managers to differentiate between catchments and identify those with the highest probability of SST hazard. Module 2 comprises a detailed evaluation of channel and catchment variables; thus, it is to be conducted applying basic training in fluvial geomorphology and GIS skills. Module 2 includes five successive steps: channel network segmentation, identification of segments with vulnerable and hazardous anthropic elements, determination of the dominant mode of sediment transport, determination of SST hazard category, and calculation of SST risk score. The method was designed to balance the present-day understanding of sediment flux in the catchment-scale sediment cascades and applicability for target end-users, mostly technically educated professionals and research scientists in river mechanics and erosion and sedimentation. [ABSTRACT FROM AUTHOR]

The present geomorphic study analyzes the morphometric anomalies of the lateritic badlands (West Bengal, India) to understand the erosion intensity, triggering factors and landscape evolution using the ALOS AW3D30 DEM and quantitative techniques of various hydro-geomorphic processes (viz., basin morphometry, rainfall-runoff simulation, geomorphic threshold, erosion indices, sediment yield, SPI, and STI etc.). The GIS-based analysis reflects that there is the requitement of minimum drainage area (i.e. 55.71-349.01 m²) to maintain one metre of gully channel in the basins which have the network density of 2.86-13.76 km km-2. The critical slope (i.e. geomorphic threshold) of badland terrain varies from 0.0222 to 0.0407 metre metre-1, having dominance of overland flow erosion to initiate gully heads. The basin-wise SCS-CN and USLE coupling estimates that within the daily rainfall range of 11.41-66.41 mm day-1, the potential sediment yield of gully basins varies from 2.15 to 9.10 t ha-1. The SL index (i.e. 0.81-47.32 m) diagram reflects the beats of gully energy profile due to stream erosion enhancement, slope steepness, resistance of underlying lithologies and active tectonics. Hypsometric integral values of the gully basins, ranging from 0.4 to 0.6, emphasize a low entropy-based fluvial system and development of mature-youthful landform stage. The evolutionary stages of badlands are explained here by the connectivity model and hillslope -- gully -- river coupling system, showing a quasi-equilibrium to complex stage of landscape development at present. [ABSTRACT FROM AUTHOR]

This study assessed historical morphology changes of the Msimbazi River in Dar es Salaam City, Tanzania, following heavy rainfall events using historical Google earth images. The erosion and sedimentation processes that cause morphological changes of a river are also associated with flooding within the river catchments. In this study, the bank-line movement, erosion and sedimentation areas and changes in river section width were analyzed under three-time periods: 2005-2012, 2012-2018, and 2018-2020. Data shows that, the timing for floods coincides with the historical records for heavy rains. It was found that, area in the upper reaches of the river such as Kinyerezi suffer from river bank erosion most, as indicated by the large increase in river width. This has resulted into washing away of infrastructure including houses and loss of land. The river channel width at Kinyerezi has widened a lot since 2005, with some sections having widths of more than 90 m. On the lower reaches for example around Kigogo and Jangwani areas, deposition of the soil materials prevails, resulting into raised river bed and reduced river widths. As the river section an hence carrying capacity is reduced, inundation of river banks occurs. This is among the causes of river bank flooding reported at these areas whenever there is a heavy storm event. It is therefore recommended that interventions to solve the flooding events in Dar es Salaam city should also include preventing catchment and river bank erosion on the upstream areas. [ABSTRACT FROM AUTHOR]

Knowledge of hydrologic connectivity is important to grasp the hydrological response at a basin scale, particularly as changes in connectivity can have a negative effect on the environment. In the context of a changing climate, being able to predict how changes in connectivity will affect runoff and sediment transport is particularly relevant for land-use planning. Many studies on hydrology, geomorphology and climatology have been conducted in the Lake Tana Basin in Ethiopia, which is undergoing rapid development and significant environmental changes. This systematic literature review aims at assessing to what extent the hydrologic connectivity has been taken into account in such research, and to identify research gaps relevant to land and water management. On the Web of Science and Scopus databases, 135 scientific articles covering those topics were identified. Aspects of hydrologic connectivity were mostly implicitly taken into account based on process-based, statistical and descriptive models. Amongst the drivers of changing connectivity, the climate was covered by a large majority of publications (64%). Components of structural hydrologic connectivity were accounted for by considering geomorphology (54%) and soils (47%), and to a lesser extent, hydrography (16%) and geology (12%). Components of functional connectivity were covered by looking at surface water fluxes (61%), sediment fluxes (18%) and subsurface water fluxes (13%). While numerous studies of the Lake Tana Basin accounted for the hydrologic connectivity implicitly, these related predominantly to functional components. The structural components are given less attention, while in the context of a changing climate, better insights into their influence on the hydrologic seem most relevant. Better knowledge of the static aspect of connectivity is particularly important for targeting appropriate soil and water conservation strategies. Being able to explicitly assess the 'structural connectivity' is therefore of direct relevance for land management and land-use policy. [ABSTRACT FROM AUTHOR]

Sediment yield is the result of all sediment production and transport processes. Recent technological developments and increasing availability of global environmental datasets, including earth observation data, provide an opportunity to systematically examine the relationship between sediment yield and controlling catchment variables by employing geographic information system (GIS). The Sediment yield index (SYI) method is employed using soil texture, topography, rainfall erosivity, geomorphology and landuse-landcover parameters to compute the spatial distribution of sediment yield rate and plan soil conservation and prioritize watershed in the Chambal river basin. The model does not provide absolute sediment yield value and can be only used for qualitative purposes. The present study estimated the sediment yield rate between 560–2625 ton/ha/yr with an average value of 1608.89 ton/ha/yr and severe, very high, high, moderate, and low priority zones. The priority levels are determined based on average sediment yield values and conservation approaches are proposed for all the catchments. [ABSTRACT FROM AUTHOR]

This note analyzes for the first time the geomorphology and sedimentary features of the Simpson Submarine Canyon (SSC), located between Chiloé Island and the Taitao Peninsula. For that purpose, multibeam bathymetric data were obtained in 2018. The SSC has a unique orientation compared to most canyons on the Chilean margin. Slope escarpments, topographic irregularities, and sinuosity of the canyon could be associated with regional tectonics. Sediment transport and deposition along the axis define the transversal morphology. On the canyon walls, erosion and transport processes dominate, evidenced by gullies, channels, and mass removals, which leave debris on the axis. We report a large landslide from a canyon wall, which could be due to a highenergy event such as an earthquake; and the generation of a large sediment wave field outside the canyon mouth, indicating a great activity by sedimentary processes. All the above could indicate that the canyon is continuously evolving. [ABSTRACT FROM AUTHOR]

Tidal flats are widely distributed on high-latitude coasts, where sea ice processes have been invoked to explain the abundance and distribution of boulders. This study documents the surface morphology and sediment dynamics of a Low-Arctic macrotidal system, the boulder-rich tidal flats of Koojesse Inlet, fronting the Nunavut capital, Iqaluit, on Baffin Island. This is a region of postglacial isostatic uplift and forced regression, with raised littoral, deltaic, and glaciomarine deposits. The spring-tidal range is 11.1 m and sea ice cover lasts roughly 9 months of the year. The extensive intertidal flats are up to 1 km wide, with a veneer of sand and gravel (including large boulders) resting on an erosional unconformity truncating the underlying glaciomarine mud, forming a terrace within the present tidal range. Over a 3-year study, no consistent pattern of erosion or deposition was evident. Over a longer time scale, the concave hypsometry, low sediment supply, slight ebb dominance of weak tidal currents, abrasion by wave-entrained sand, ebb-oriented ripples formed under subaerial drainage, and slumps on the terrace flanks are consistent with seaward hydraulic and gravitational sediment transport. These processes may be of greater importance than shoreward ice transport. This study underlines the importance of relict glaciomarine deposits, postglacial uplift, and falling relative sea level in the erosional development of these high-latitude tidal flats. Relative sea-level projections for Iqaluit are ambiguous, but a switch to rising sea level, if it occurs, combined with more open water and wave energy, could alter the foreshore dynamics of the system. [ABSTRACT FROM AUTHOR]

Well-log and three-dimensional (3D) seismic data are used to investigate the tectonic controls during the depositional periods of the Kongdian and Shahejie formations from Ek–Es4L to Es4U–Es3L–M on strata distribution, depositional systems and sediment dispersal in the Qingdong Sag, Bohai Bay Basin, East China, from a source-to-sink perspective. This tectonic transition is characterised by the Tanlu Fault switching from sinistral to dextral strike-slip as the fault system changed from a dominant NW–WNW trend during the Ek–Es4L period to a dominant WNW–EW trend during the Es4U and Es3L–M periods. These changes subsequently controlled the framework and areal extent of sediment dispersal in the inner-basin source-to-sink systems and resulted in a change in trend of inner-basin secondary structural belts, from primarily being NW-trending during the Ek–Es4L period to E–W-trending during the Es4U and Es3L–M periods. The tectonic transition also resulted in the western and southern source-to-sink systems expanding with time and controlled the flow path and sediment redistribution within each source-to-sink system with migration of the subsidence centre of the Qingdong Sag and even the region. The significant changes in the basin structure controlled the source area, flow path, sediment transport distance and direction, and have a significant impact on the interpretation of depositional environments and reservoirs in rift basins with a multi-phase evolution history. The Qingdong Sag, Bohai Bay Basin, experienced a tectonic transition during sediment deposition in the Eocene. The tectonic transition resulted in changes to the fault system and basin geomorphology. Fault movement and changes in basin geomorphology affected source-to-sink systems. [ABSTRACT FROM AUTHOR]

Dunes form where winds blow over a bed of mobile sediment grains — conditions that are common in our solar system. On Earth, dunes abound in arid continental interiors and along sandy coastlines. Dune fields have also been recognized on Venus, Mars, Saturn's moon Titan, and Pluto. In response to the different boundary conditions and other environmental forcings, dunes adopt a rich diversity of shapes, sizes, and behaviors. Thus, people around the globe and over centuries have developed a rich vocabulary to describe dunes and their complexity. As a result, existing dune nomenclature often includes redundant terms with differing definitions across scientific communities. Previous studies have endeavored to link dune shape to environmental forcing, usually by means of correlation. Although instructive, correlation-based classifications can be misleading if not based on underlying mechanics or if dune morphogenetic classes are not uniquely defined. Here, we synthesize existing dune terminology and use the last two decades of research on dune morphodynamics to propose three complementary dune classification schemes based on: (1) descriptive dune geomorphology, (2) morphodynamic processes, and (3) fluid mechanics and physics of sediment transport. The first classification relates dune types to geomorphic setting, the presence or absence of vegetation or obstacles, and dune shape (including planform shape, and cross-sectional symmetry or asymmetry). Dune classes can be further subdivided where the direction of sand transport is known independently. The second classification relates dune types and shapes to bed properties (sand-covered vs partially starved bed) and wind forcing (directional variability or the relative strengths and directions of wind modes) that together influence dune dynamics (growth, migration, elongation) and select the dominant processes by which dunes are shaped and oriented relative to the resultant transport direction. The third classification relates, for different planetary environments, the range of possible dune sizes, from minimum to maximum wavelength, to fluid flow regime (rough or smooth) and the response of sediment flux, which influence the coupling between sand bed topography, fluid flow, and sediment transport. These characteristic lengths are useful scales for comparative geomorphology. The three classification schemes provide complementary information. Together, they form a unified framework for geomorphologists, sedimentologists, geographers, physicists, and others to describe windblown sand dunes on Earth and beyond through their shape, dynamics, and size as a response to winds and boundary conditions. [ABSTRACT FROM AUTHOR]

Sandspits at river mouths are important socio-ecological but fragile coastal ecosystems. Due to their significant role, particularly in shielding areas behind them from wave impact, sandspits are crucial, albeit they also pose challenges such as increased fluvial flooding, which often necessitates substantial engineering interventions such as artificial breaching. Here, four wave-dominated sandspits are compared to determine their common behavior. The study sites at river mouths have in common a high control of waves on longshore sediment transport leading to sandspit development; the Langue de Barbarie at the Senegal River delta, the Bouche du Roi at the mouth of the Mono River in Benin, the Mataquito River mouth in Chile, and the Pomene River mouth in Mozambique, each characterized by unique hydrodynamic conditions and geomorphologic features that influence their evolution and susceptibility to natural and anthropogenic impacts. Their cycles of opening and development, typically spanning decades, are studied by collecting 37 years of shoreline and wave reanalysis data from the Landsat and Sentinel-2 missions. It is shown that part of the morphodynamics is truly intrinsic and that climatic wave evolution drives only a small part of their evolution. A simplified model is introduced to predict the cyclic behavior of spits. The proposed model for sandspit development is based on a cyclic behavior, where newly formed spits mature and eventually break, resetting the cycle. This cyclic perception is represented as a function of time, where the elongation of the spit relative to its maximum length is modeled as a function of time and a constant wave-driven longshore sediment transport component. The model is tested at several sites with similar environmental conditions and blindly at one site with reasonable results. The present work also highlights the importance of spit evolution and the associated variability they impose on coastal downdrift and updrift, especially when considering anticipating the implementation of engineering solutions. • Cyclic behavior of sand spit lengthening. • Predicting sand spit length with a conceptual model. • Updrift and downdrift coastal impact of a sand spit lengthening. [ABSTRACT FROM AUTHOR]

Chirp profiles collected on the southern Brazilian shelf were combined with sedimentological and hydrodynamic data to characterize shelf geomorphology, focusing on the development of outer shelf bedforms and their genetic links with major oceanic currents. Outer shelf sediment accumulations are interpreted as two scales of bedforms, such as dunes and sand ridges. In the São Paulo Bight, cuspate bedforms are bounded landward by a geomorphological scarp. The sector between Florianopolis and Mostardas also exhibits frequent asymmetric bedforms, whereas the inner- middle shelf is covered by semitransparent sheets. The southern Rio Grande Cone is characterized by stratified deposits covering vast outer shelf areas. Surficial sediment samples reveal a dominantly muddy composition and relatively high carbonate contents. Hydrodynamic data indicate a major influence of the Brazil Current over the São Paulo Bight. The prolific bedform outer-shelf environment is assumed to be mostly relict formed in a transgressive shallow-water setting. The sand ridges are believed to have evolved from a moribund stage characterized by morphological degradation to a relict stage, with preservation enhanced by fine-grained winnowing, coarse sediment armoring, and early cementation. Bedform migration seems to be occurring on the São Paulo Bight due to the presence of a nearly permanent meander of the Brazil Current. Over most of the inner shelf, the northward advection of sediments mainly led by the Brazilian Coastal Current has formed extensive fine-grained deposits. The occurrence of a relict shelf scarp may have conditioned the formation of the outer-shelf bedform environment. The vast spatial distribution of bedforms over most of the outer shelf seems comparable with other shelf areas, such as the south African shelf, dominated by the influence of unidirectional oceanic currents. Dune dimensions are lower on the Brazilian shelf, due to their relict character, the geomorphological configuration of the margin, and the scarcity of sand sources. • Outer shelf along the southern Brazilian margin covered by bedforms • Inner-to-middle shelf advection of fine sediments driven by Brazilian Coastal Current • Two scales bedforms (sand ridges and very large dunes) in a relict to moribund stage • Bedform preservation aided by fine-grained winnowing by the Brazil Current, armouring and cementation • Prolific bedform environment comparable with the south African shelf [ABSTRACT FROM AUTHOR]

Filling of dolines with aeolian sediments, one of the less frequently described ways in which they are filled, is analysed in the present study on an example of a doline in the high-mountain karst of the Dinarides. There is a series of deep dolines on a broad ridge (about 2450 m a.s.l.) on Mt. Durmitor (Montenegro) in the southeastern part of the Dinarides. The accumulation of very fine-grained sand that almost completely fills one of the dolines was analysed. More than 99% of the accumulation was found to be composed of well-sorted quartz grains with an average size of 89 µm and no vertical differences in granulometric or textural characteristics. With respect to mineral composition, the accumulation differs significantly from that prevalent in this part of the Dinarides, in which different kinds of carbonate rocks are dominant. The conducted analyses indicated an aeolian origin of the sediments. Significant aridification that began in the Middle Holocene made the area of North Africa a source of sediments that were transported by the aeolian process to neighbouring regions. Geomorphological-sedimentological research on Mt. Durmitor and earlier investigations of the wider Mediterranean region indicate that dolines in high-mountain karst can be filled with aeolian sediments. The sediments originated from territory of the northern Sahara, and the filling occurred in the Late Holocene, at the close of the African humid period. The present study shows that apart from the influence of local factors, regional geomorphological processes such as aeolian transport can also exert significant influence on the filling of dolines. It also indicates a high intensity and strongly expressed dynamics of aeolian sediment transport from the territory of Africa to this part of Southern Europe. [ABSTRACT FROM AUTHOR]

The Qinghai-Tibetan Plateau, known as the world's "third pole", is home to several large rivers in Asia. Its geomorphology is exceptionally vulnerable to climate change, which has had a significant impact on historical riverbed development through runoff and sedimentation processes. However, there is limited research combining climate change, sedimentology, and chronology with river dynamics to investigate riverbed evolution patterns in geological-historical time scales and their changes in overland flow capacity. In the current study, the evolution of a representative portion of the river channel in the Nangqian basin in the Lancang River headwaters was investigated to explore the reaction of the riverbed to climatic change during the geological period via field surveys, riverbed drilling, optically stimulated luminescence (OSL) dating and bankfull channel geometry parameters. The generalized channel section of the historical period was obtained by linking sedimentary layers of the same age on the distribution map of borehole sections, and the bankfull area of the river was computed accordingly. The restored bankfull areas can effectively reflect the ability of historical river channels to transport water and sediment, thus reflecting the climate change at that time. The findings showed that river morphology in the mounded river section could be successfully reconstructed using OSL dating and sedimentary records and that the conceptual sections of the historical warm periods at 2000 years (2 ka) and 0.7 ka can be recovered. Based on the reconstruction, the calculated bankfull areas during the two warm events were larger than present by factors of 1.28 and 1.9, respectively, indicating a stronger capacity for transporting water and sediments. This is the first trial in the Lancang headwaters to investigate the response of river morphology to climate change on a geological time scale. [ABSTRACT FROM AUTHOR]

Rocky reefs provide complex structures in the otherwise largely sand-dominated coastal North Sea. Therefore, these reefs are highly important natural habitats for the functioning of coastal ecosystems, as they provide shelter, refuge and nursery grounds for various mobile and sessile species. In the North Sea, the spatial distribution of these habitats has been intensively investigated over recent years. However, these studies generally provide static accounts of the current state of these reef systems, but limited data exist on the temporal variations in sediment dynamics at and around natural rocky reefs. In this study, we provide observations from a multiannual time series of hydroacoustic seafloor surveys conducted at an isolated rocky reef in the North Sea. We use multibeam bathymetry and side-scan sonar backscatter data in combination with video observations, sediment sampling, and sub-bottom profiler data to assess the long-term variations of the rocky reef system. The reef is located in water depths between 11 and 17 m with an areal extent of ~0.5 km2 and is surrounded by mobile sands. The topography of the rocky reef appears to create a distinct hydrodynamic system that permits mobile sands to settle or move into bathymetrical deeper parts of the reef. Our results suggest a very dynamic system surrounding the reef with large scale scouring, sediment reworking and transport, while the shallower central part of the reef remains stable over time. We demonstrate the importance of hydrodynamics and current scouring around reefs for the local variability in seafloor properties over time. These small-scale dynamics are likewise reflected in the spatial distribution of sessile species, which are less abundant in proximity to mobile sands. The hydroacoustic mapping and monitoring of seafloor dynamics at higher spatial and temporal resolutions presents an important future direction in the study of valuable coastal habitats. [ABSTRACT FROM AUTHOR]

The development of colluvial wedges at the base of fault scarps following normal-faulting earthquakes serves as a sedimentary record of paleoearthquakes and is thus crucial in assessing seismic hazard. Although there is a large body of observations of colluvial wedge development, connecting this knowledge to the physics of sediment transport can open new frontiers in our understanding. To explore theoretical colluvial wedge evolution, we develop a cellular automata model driven by the production and disturbance (e.g., bioturbative reworking) of mobile regolith and fault-scarp collapse. We consider both 90 and 60 ∘ dipping faults and allow the colluvial wedges to develop over 2000 model years. By tracking sediment transport time, velocity, and provenance, we classify cells into analogs for the debris and wash sedimentary facies commonly described in paleoseismic studies. High values of mobile regolith production and disturbance rates produce relatively larger and more wash-facies-dominated wedges, whereas lower values produced relatively smaller, debris-facies-dominated wedges. Higher lateral collapse rates lead to more debris facies relative to wash facies. Many of the modeled colluvial wedges fully developed within 2000 model years after the earthquake, with many being much faster when process rates are high. Finally, for scenarios with the same amount of vertical displacement, differently sized colluvial wedges developed depending on the rates of geomorphic processes and fault dip. A change in these variables, say by environmental change such as precipitation rates, could theoretically result in different colluvial wedge facies assemblages for the same characteristic earthquake rupture scenario. Finally, the stochastic nature of collapse events, when coupled with high disturbance, illustrates that multiple phases of colluvial deposition are theoretically possible for a single earthquake event. [ABSTRACT FROM AUTHOR]

Since then, the work of researchers trained or working in collaboration with Des over this period have been key to its development, and its operational application by the Environment Agency has grown with demand for improved catchment understanding (Walling, 2013; Walling & Collins, 2016). "Linked" thinking: A framework for catchment management Walling (1990) highlighted the need to understand the linked elements of the catchment sediment system and not simply sediment yield at the catchment outlet. Des Walling's 1990 chapter ' I Linking the field to the river i : I sediment delivery from agricultural land i ' (Walling, 1990, in Boardman et al., 2003) highlighted the need for an improved understanding of sediment dynamics in agricultural catchments in the UK against a backdrop of ' I recent concern for the increasing incidence of soil erosion i '. [Extracted from the article]

Stream ecosystem metabolism contributes to global carbon cycling, yet predicting metabolism across ecosystems remains elusive. Even within stream segments, spatial variation in metabolic rates and their controls can be substantial, exhibiting sudden rather than continuous changes. We measured metabolism at 6 sites along a 75-km mainstem segment of Marsh Creek, Idaho. This agricultural stream lacks major geomorphic transitions such as tributaries or changes in valley width, but possesses patchy patterns of turbidity. We asked: (1) How variable is metabolism along this segment, and (2) How do the controls on metabolism vary along this segment? Metabolism varied several-fold along this stream segment. Average rates of gross primary production (GPP), ecosystem respiration (ER), and net ecosystem production (NEP) among sites did not correlate with water quality or aquatic macrophyte cover. Rather, reaches along this segment appear to represent different process domains that were characterized by turbidity: More turbid reaches saw negative effects of turbidity on GPP and NEP and positive effects on ER. Turbidity was associated with increased respiration and decoupled ER from GPP at turbid sites. Less turbid sites had stronger coupling between GPP and ER, and GPP was predicted by light and temperature. Heterogeneous sediment supply and transport capacity along Marsh Creek create patchy patterns of turbidity, which affects the controls on metabolism. Geomorphic controls on ecosystem processes are complex but not random. Understanding how metabolism and its controls vary across process domains is needed to scale up process rates and understand how process rates might respond to future changes. [ABSTRACT FROM AUTHOR]

Direct measurements of erosional response to past climate change are scarce, but mid‐latitude landscapes can record how shifts between cold and warm periods altered erosion outside glacial margins. To study hillslope responses to periglaciation, we measured bulk geochemistry and cosmogenic 10Be and 26Al concentrations in colluvium and weathered bedrock in an 18 m regolith core from Bear Meadows, Pennsylvania, ∼100 km south of maximum glacial extent. Using core lithology, cosmogenic nuclide concentrations, and regional 10Be‐derived erosion rates, we show the onset of 100‐Kyr glacial cycles at the Mid‐Pleistocene Transition (1.2–0.7 Ma) instigated multiple periglacial episodes in central Appalachia, increasing erosion rates compared to the relatively warmer Neogene. Our results show the higher efficiency of periglacial versus temperate erosion processes and highlight a pervasive Pleistocene periglacial erosion signal preserved in the 10Be inventory of surface sediments in central Appalachia, where erosion rates are slow enough to integrate previous cold‐climate processes. Plain Language Summary: During ice ages in the past 2.6 million years, mid‐latitude landscapes like central Pennsylvania were shaped by extreme cold and thawing permafrost, conditions that promote fast breakdown and transport of soil. However, the effect of these cold climates and subsequent warming on erosion rates is unclear since we often lack records of hillslope erosion of warm and cold periods. We drilled 18 m through hillslope material emplaced during permafrost thaw and into the underlying weathered bedrock, and measured the concentrations of 10Be and 26Al, two isotopes that serve as tracers of burial timing and erosion rate. The ratio of 26Al/10Be in the oldest permafrost thaw unit indicates the material was deposited about one million years ago, corresponding to a switch to colder glacial periods followed by more abrupt and extreme warming. The concentrations of 10Be in bedrock below the deposits also imply slower erosion rates prior to the onset of glacial‐interglacial cycles. Our results indicate that cold climate processes are more efficient at eroding rock and transporting sediment than temperate processes and help explain patterns in erosion rates across the mid‐Atlantic region measured over different time scales. Key Points: In situ 10Be and 26Al measured in 18 m regolith core from central Pennsylvania, 100 km south of Pleistocene maximum glacial extentPeriglacial activity began at onset of 100‐Kyr glacial cycles, marked by permafrost thaw during abrupt warming following sustained coldPleistocene periglacial conditions led to an increase in erosion rates compared to the more temperate Neogene climate [ABSTRACT FROM AUTHOR]

Disturbances such as floods, fires, and mass movements introduce large volumes of sediment into fluvial systems. Tracking the movement of disturbance‐generated sediment provides insight into the processes of fluvial system response. Few studies document a post‐disturbance response that explicitly links channel change to evolution of a reservoir delta. We exploit the tight coupling in a sediment source‐to‐sink analysis of flood deposits over 6 years. Within the first year after the flood, the channel incised 1.5 m and widened 10 m. Limited channel morphologic change thereafter is attributed to bed armoring. Morphodynamic modeling of the channel predicted transport of Radio‐Frequency Identification‐tagged clasts from which we infer a discharge threshold of >14 m3/s for future geomorphic adjustments. Post‐flood discharges and reservoir drawdowns deposited 3 times the volume of sediment in the delta than was deposited during the flood and prograded the delta 200 m. Overall system response followed a characteristic sediment decay flux. Despite the sediment flux decline, comparable rates of delta progradation occurred due to reservoir drawdowns that shifted the sediment source from the channel to incision of the delta. Thus, the delta evolved via distinct processes based on sediment source and reservoir level: (a) aggradation of the delta topset and progradation of the Gilbert‐type clinoform when sediment is sourced from the channel during years when reservoir level fluctuated seasonally; and (b) delta progradation through incision of the delta topset during reservoir drawdowns. Our results reveal a genetic relationship between post‐disturbance channel and delta evolution. Plain Language Summary: Floods, fires and mass movements deliver large volumes of sediment into river systems. Few studies track what happens to this sediment as it moves through a channel and gets deposited in a reservoir, however. We monitored sediment in a channel and adjacent reservoir for 6 years after an extreme flood, capturing the effects of a high snowmelt discharge and two reservoir drawdowns. Channel change was dominated by incision and widening in the first year after the flood. Storage of the remaining unconsolidated flood sediments may persist for long periods of time. Sediment transported to the reservoir caused the delta to prograde an equal amount during high discharges as during low discharges and reservoir drawdown. Importantly, the sediment source shifted from the channel to the delta surface during drawdowns. Finally, the sediment volume delivered to the reservoir declined exponentially over time. We conclude that that there is a link between post‐disturbance channel morphology and delta evolution influenced by reservoir level. Key Points: Channel bed armoring in the first year after a flood limits morphologic change and results in large volumes of stored sedimentFlood‐deposited sediment in a reservoir delta declines nonlinearly over 6 yearsPost‐flood erosional processes controlled by reservoir level link sediment source to delta morphodynamics [ABSTRACT FROM AUTHOR]

Modeling network‐scale sediment (dis)connectivity and its response to anthropic pressures provides a baseline understanding of river processes and sediment dynamics that can be used to forecast future hydro‐morphological changes in river basins. However, this requires a solid understanding of how a system is currently operating, and how it operated in the past. We present the basin‐scale, dynamic sediment connectivity model D‐CASCADE, which combines concepts of network modeling with empirical sediment transport formulas to quantify spatiotemporal sediment (dis)connectivity in river networks. D‐CASCADE accounts for multiple factors affecting sediment transport, such as spatiotemporal variations in hydrological regime, different sediment grain sizes, sediment entrainment and deposition. Add‐ons are included in D‐CASCADE to model local changes in river geomorphology driven by sediment‐induced variations in features such as channel width. We apply D‐CASCADE to the well‐documented Bega River catchment, NSW, Australia, where significant geomorphic changes to rivers have occurred post European colonization (after 1850s), including widespread channel erosion and sediment mobilization. The Bega catchment provides a useful case study to test D‐CASCADE, as original source data on the historical sediment budget are available. By introducing historic drivers of change in the correct chronological sequence, the D‐CASCADE model successfully reproduced the timing and magnitude of major phases of sediment transport and associated channel adjustments over the last two centuries. With this confidence, we then ran the model to test how well it performs at estimating future trajectories of basin‐scale sediment transport and sediment budgets at the river reach scale. Key Points: We present the new dynamic D‐CASCADE model for network‐scale river sediment (dis)connectivity modelingD‐CASCADE successfully reproduced major historic geomorphological changes observed in the Bega river network after European settlementD‐CASCADE is used to test future trajectories of basin‐scale sediment transport and reach‐scale sediment budget in the Bega river system [ABSTRACT FROM AUTHOR]