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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]

Rates of land surface processes provide insights into climatic and tectonic influences on topography. Bedrock incision rates are estimated by dating perched landforms such as strath terraces, assuming a constant bedrock incision rate from terrace abandonment to the next terrace level or present river level. These estimates express biases from the stochastic nature of sediment and water discharge in controlling river incision as well as from using a mobile channel elevation as a reference frame, leading to different incision rates when calculated over different timeframes. We introduce a 1‐D model incorporating fluvial mechanics, tectonics, sediment, and climate variability to predict these biases and assess their sensitivity to climate and tectonics. Findings suggest biases intensify under highly variable climates and slow rock uplift, with climate periodicity being a primary control for our modeled scenarios. Our model provides a mechanism to improve river incision measurement uncertainty, impacting paleoclimate and tectonic geomorphology reconstructions. Plain Language Summary: Geomorphologists often measure how fast rivers erode bedrock over time by dating river terraces that have been uplifted to be higher than the elevation of the modern river channel. This helps us learn how landscapes evolve and about what past climates were like over long timescales. But this method is complicated by the fact that rivers do not erode rocks at a steady rate and the elevation of the channel surface above which we measure terrace height changes over time. We present a numerical model that predicts how these terraces develop under different climates and rates of rock uplift. Model results imply that measurements of long‐term river incision are most susceptible to temporal bias in regions experiencing highly variable paleo‐climate and slow rock uplift. Our model helps us make better measurements of river erosion and understand how climate and rock uplift shape landscapes. Key Points: We present a numerical model that reproduces biases in rates of river incision measured from strath terracesWe find that these measurement biases are the strongest when climates are highly variable and rock uplift is slowUnderstanding bedrock incision measurement biases allows for bias correction in field studies and improves data comparability [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]

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]

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]

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]

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.

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]

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]

Amplified warming of high latitudes and rapid thaw of frozen ground threaten permafrost carbon stocks. The presence of permafrost modulates water infiltration and flow, as well as sediment transport, on soil-mantled slopes, influencing the balance of advective fluvial processes to diffusive processes on hillslopes in ways that are different from temperate settings. These processes that shape permafrost landscapes also impact the carbon stored on soil-mantled hillslopes via temperature, saturation, and slope stability such that carbon stocks and landscape morphometry should be closely linked. We studied >69,000 headwater basins between 25° and 90 °N to determine whether the thermal state of the soil sets the balance between hillslope (diffusive) and fluvial (advective) erosion processes, as evidenced by the density of the channel networks (i.e., drainage density) and the proportion of convex to concave topography (hillslopes and river valleys, respectively). Watersheds within permafrost regions have lower drainage densities than regions without permafrost, regardless of watershed glacial history, mean annual precipitation, and relief. We find evidence that advective fluvial processes are inhibited in permafrost landscapes compared to their temperate counterparts. Frozen soils likely inhibit channel development, and we predict that climate warming will lower incision thresholds to promote growth of the channel network in permafrost landscapes. By demonstrating how the balance of advective versus diffusive processes might shift with future warming, we gain insight into the mechanisms that shift these landscapes from sequestering to exporting carbon. [ABSTRACT FROM AUTHOR]

• Overlapping crater populations constrain the total era of martian valley formation. • Martian valleys may have formed intermittently over hundreds of millions of years. • Long-term erosion rates would have been similar to the modern Atacama Desert. A number of studies have constrained the cessation of martian valley network activity to around the Noachian-Hesperian boundary, but the total time period over which these features formed remains poorly constrained. Most attempts to ascertain valley network formative timescales rely on an intermittency factor that varies widely for terrestrial rivers and is unknown for Mars. In this contribution, superposition relationships are used to identify crater populations that pre- and postdate valley network incision, resulting in maximum cumulative valley formation times of ∼108 years. These timescales correspond with long-term erosion rates of ∼0.25 m/Myr, similar to those calculated for the Middle to Late Noachian as well as the central Atacama Desert since the Late Miocene. Assuming sediment transport rates previously calculated for other martian valley networks, this implies a minimum fluvial intermittency of ∼10−5, several orders of magnitude lower than modern day Earth rivers but similar to values independently calculated for some martian fluvial deposits. This low intermittency suggests that martian valley incision may have been significantly hindered by erosion into existing bedrock or by boulder armoring of the valley floor. Alternatively, unlike river valleys on Earth, runoff events driving martian valley network activity may have been non-seasonal, Milankovitch-like cycles, with long eras of quiescence between periods of intensified fluvial activity. [ABSTRACT FROM AUTHOR]

We review the role of science in shaping river flood risk management policy in England, highlighting the relatively recent influence of fluvial geomorphology, river ecology, climate change and ecosystem services in evidence-based decision-making. These disciplines, together with an historical perspective, catchment-scale delivery, integrated land and water management planning, and adaptive management are crucial in managing future flood risk. A central tenet of previous land drainage policy was a professional (and public) mindset about flood 'prevention' solutions for river flooding. As a direct consequence, more than 8,500 km of rivers were 'improved' by mechanical dredging during the 1930s to 1980s; habitats were destroyed, but flooding continued. A more enlightened, long-term approach has since evolved in response to environmental imperatives and lessons learnt from several major floods during the last two 'flood-rich' decades. River science, local knowledge and land management incentives allow more natural processes to be restored in river catchments. The natural capital and ecosystem service benefits of river systems are now better understood and quantified, whereas the importance of sediment transport is fully recognised, with sources and sinks treated more holistically than in the past. Evaluating the outcomes of innovative runoff and river management techniques from both physical and socioeconomic perspectives will determine the success of a catchment-based approach. We highlight some of the uncertainties, nuances and assumptions associated with recent initiatives such as Natural Flood Management, Citizen Science and Flood Action Groups. Further integration between policy, strategic planning and local delivery is needed to anticipate and respond to climate and catchment land use changes. River science will play a crucial part in identifying the most effective way of improving flood management and in a way that helps to deliver the recovery of nature. It will inform adaptive management to cope with climate change. [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]

Source‐to‐sink transfer of sediment and organic carbon (OC) is regulated by river mobility. Quantifying trends in river mobility is, however, challenging due to diverse planform morphologies (e.g., meandering, braided) and measurement methods. Here, we utilize a remote‐sensing method applicable to all planform morphologies to quantify the mobility timescales of 80 rivers worldwide. Results show that, across the continuum from meandering to braided rivers, there is a systematic reduction in the timescales of channel mobility and—to a lesser extent—floodplain reworking. This leads to a decrease in the efficiency with which braided rivers rework old floodplain material compared to their meandering counterparts. Reduced floodplain reworking efficiency of braided rivers leads to smaller channel‐belt areas relative to their size. Results suggest that river‐mobility timescales derived from remote sensing can aid in the characterization of sediment and OC storage and transit times at a global scale. Plain Language Summary: Rivers transport sediment and organic carbon (OC) from the mountains to the sea, and river movement affects sediment and OC transit times in landscapes. Understanding the controls on timescales of river movement is critical for assessing how fluvial processes influence the terrestrial carbon cycle. While previous work has quantified different river planform shapes on the Earth's surface (e.g., meandering, wandering, and braided), little is known about how the pace and nature of river movement is different between river planform shapes. This is because we lack methods to measure and compare river movement across different river planform shapes. Here, we leverage a tool to quantify river movement from time series of satellite imagery that is equally applicable to all river planform shapes. We apply this method to calculate the timescales of river movement of 80 rivers worldwide for the last 37 years. We show that (a) braided rivers migrate faster than meandering rivers, and (b) braided rivers move over a smaller area relative to their size. Comparing results with geochemical observations from the Río Bermejo—a well‐studied river for sediment‐OC cycling—we show that our mobility framework may provide a new way to assess sediment and OC storage timescales in floodplains. Key Points: We quantify timescales of floodplain reworking and channel‐overlap decay from satellite imagery of 80 rivers worldwideFrom meandering to braided planform morphology, there is a reduction in the overlap timescale and the reworking timescaleMobility timescales provide a means for remotely quantifying terrestrial‐sediment and organic‐carbon storage and transit [ABSTRACT FROM AUTHOR]

• An efficient 2D shallow water hydro-sediment-morphodynamic model is presented. • Morphodynamic processes under the impact of cascade movable weirs are studied. • Disparate morphological changes may result under different operation schemes. • An alternating operation scheme is proposed to constrain morphological changes. Cascade movable weirs have been increasingly widely used for river landscaping, water storage and ecological wellbeing. The weirs disturb the prior equilibrium in line with fluvial hydrology, sediment transport and geomorphology, and may lead to profound changes in the river, of which, however, the understanding has so far remained poor. Here, the first of its kind, a computational modelling study is presented on the morphodynamic processes under the impact of cascade hydraulic lifting dams, a type of movable weirs, as to the middle Fen River, China. A two-dimensional shallow water hydro-sediment-morphodynamic model is applied to resolve the fluvial processes, which is physically coupled and computationally efficient based on Finite Volume Method, unstructured mesh, local time stepping and parallel computing. Computational results show that the cascade dams alter the flow and sediment transport locally and on the reach scale in a distinct manner under different operation schemes, which in turn incur disparate morphological changes. Collapse of all the dams all year round would lead to net degradation in the study reach, with the floodplains aggrading and the main channel degrading. Operation of all the dams all year round may induce an overall aggradation both on the floodplains and in the main channel. If all the dams collapse in flood seasons and operate in dry seasons (CF), degradation occurs in the main channel whereas the floodplains experience aggradation, with a net degradation. When only the dams in the main channel operate all year round (OM), the floodplains degrade while the main channel aggrades, resulting in a net aggradation in the study reach. Either aggradation or degradation may prevail locally on floodplains, in main channel and individual subreaches. The present findings lead us to propose a complex operation scheme of annually alternating CF and OM to constrain significant morphological changes. [ABSTRACT FROM AUTHOR]

Lukulo is a river that flows through pre-tertiary rocks to the recent. The long Lukulo fluvial processes which included erosion, transportation, and deposition were depicted in extensive alluvial deposits downstream of the river. This vast alluvial plain may be a deposit result of the Lukulo flood in the past. The paleo-flood study is a study of flood events in the past with the technique used, namely knowing slack water deposits. Delineation of slackwater deposits is necessary to determine the location of paleoflood deposition. Geomorphology of Lukulo watershed is needed as a preliminary study to determine the characteristics of the Lukulo watershed. Based on geomorphological analysis of the Lukulo watershed with river geomorphological analysis, field research, and literature studies, the result of this watershed geomorphology was obtained, namely; the morphology of the Lukulo watershed included an elongated oblong shape of the watershed, with an average Rc value of all three segments (upstream, middle, and downstream) of 0,52. The average drainage density (Dd) of river flows in the Lukulo watershed is 8,05 km/km2 (middle class). The Lukulo gradient upstream is 450, entering the middle is reduced to 300, and downstream the gradient is reduced to 100. The morphology and morphometry of the Lukulo watershed are interpreted to mean that Lukulo belongs to the medium-spanned watershed in terms of flood runoff and erosion. The lithology is a mixture of impermeable and permeable rocks. Delineation of diluvial and alluvial deposits is found in the upstream, middle, and downstream, of the Lukulo river. It depicts delineated paleoflood deposits in all segments of the river. [ABSTRACT FROM AUTHOR]

Much of Paul Bishop's published work can be classified under the heading of fluvial geomorphology. His distinctive approach was to use fluvial evidence to interrogate hypotheses regarding landscape evolution, an effort that inevitably led to reconciling evidence across a range of spatial and temporal scales. Here, examples from Paul's work are used to demonstrate his methodology and his considerable contributions to current understanding of landscape evolution. River long profiles reveal much about landscape history, although they integrate the effects of multiple boundary conditions and external forcing factors. Empirical, theoretical and modelling studies show how long profiles can be interpreted to address fundamental questions regarding the role of sediment in bedrock river incision and transient behaviour following climate change. The complex nature of transient landscape responses underpins much of Paul's work, and here examples form the Sierra Nevada, Spain and Namibia are used to illustrate how modern analytical techniques have revolutionised understanding of this transience. An assessment is provided of Paul's contributions to fluvial geomorphology and the wider discipline of geomorphology as a whole, noting the longevity of his contribution and the considerable impact that his collaborators, particularly his research students, have made, and continue to make. [ABSTRACT FROM AUTHOR]

Fluvial channel belts, the deposits accumulated in rivers surrounded by floodplain deposits, are sensitive environmental recorders. Across Mars, wind has exposed ancient channel belts via the preferential erosion of floodplain strata, creating landforms called fluvial ridges. However, river deposits observed by the Mars rover Curiosity are instead exposed along a series of steep slopes and shallow benches, and short, truncated ridges we call noses. Here, we tested the hypothesis that these exposures record channel‐belt exhumation with a preferential direction of scarp retreat (a slope‐aspect control), in contrast with models of fluvial‐ridge formation. Using a landscape evolution model sensitive to lithology and an Earth‐analog 3D‐seismic‐reflectance volume imaging fluvial stratigraphy, we generated synthetic erosional landscapes where channel‐belt exhumation created benches and noses rather than fluvial ridges, depending on the orientation of belts relative to the preferential direction of scarp retreat, which we suggest is set by winds steered along crater topography. Plain Language Summary: Ancient river deposits exist across Mars and can be identified in satellite data by erosional landforms called fluvial ridges. Fluvial ridges take the shape of ancient river deposits, and are useful for understanding the history of water on Mars. However, the Curiosity rover at Gale crater, Mars, has observed river deposits that are not associated with fluvial ridges, but rather bench‐ and nose‐like landforms that are not generally associated with ancient river deposits. We modified a computer model that generates fluvial ridges from ancient river deposits by adding a preferred direction for scarp retreat, which may exist in craters on Mars because crater topography steers winds, and winds currently drive erosion on Mars. Our model generated benches and noses rather than fluvial ridges, demonstrating that these landforms may be used as indicators of ancient river deposits in craters on Mars, similar to fluvial ridges. Key Points: River stratigraphy at Gale crater, Mars, is exposed along landforms distinct from the fluvial ridges commonly observed outside cratersAn erosion model with a preferential scarp‐retreat direction forms topographic benches and noses from river stratigraphy, rather than fluvial ridgesAlluvial strata in other craters on Mars may be exposed along noses and benches [ABSTRACT FROM AUTHOR]

Remote sensing plays a central role in the assessment of environmental phenomena and has increasingly become a powerful tool for monitoring shorelines, river morphology, flood-wave delineation and flood assessment. Optical-based monitoring and the characterization of river evolution at long time scales is a key tool in fluvial geomorphology. However, the evolution occurring during extreme events is crucial for the understanding of the river dynamics under severe flow conditions and requires the processing of data from active sensors to overcome cloud obstructions. This work proposes a cloud-based unsupervised algorithm for the intra-event monitoring of river dynamics during extreme flow conditions based on the time series of Sentinel-1 SAR data. The method allows the extraction of multi-temporal series of spatially explicit geometric parameters at high temporal and spatial resolutions, linking them to the hydrometric levels acquired by reference gauge stations. The intra-event reconstruction of inundation dynamics has led to (1) the estimation of the relationship between hydrometric level and wet area extension and (2) the assessment of bank erosion phenomena. In the first case, the behavior exhibits a change when the hydrometric level exceeds 1 m. In the second case, the erosion rate and cumulative lateral erosion were evaluated. The maximum erosion velocity was greater than 1 m/h, while the cumulative lateral erosion reached 130 m. Time series of SAR acquisitions, provided by Sentinel-1 satellites, were analyzed to quantify changes in the wet area of a reach of the Tagliamento river under different flow conditions. The algorithm, developed within the Python-API of GEE, can support many types of analyses of river dynamics, including morphological changes, floods monitoring, and bio-physical habitat dynamics. The results encourage future advancements and applications of the algorithm, specifically exploring SAR data from ICEYE and Capella Space constellations, which offer significantly higher spatial and temporal resolutions compared to Sentinel-1 data. [ABSTRACT FROM AUTHOR]

Metal-mining exploitation has caused ecosystem degradation worldwide. Legacy wastes are often concentrated around former mines where monitoring and research works are mostly focused. Geochemical and physical weathering can affect metal-enriched sediment locations and their capacity to release metals at a catchment scale. This study investigated how fluvial geomorphology and soil geochemistry drive zinc and lead dispersion along the Nant Cwmnewyddion (Wales, UK). Sediments from different locations were sampled for geochemical and mineralogical investigations (portable X-ray fluorescence, scanning electron microscope, X-ray diffraction, and electron microprobe analysis). The suspended sediment fluxes in the streamwater were estimated at different streamflows to quantify the metal dispersion. Topographical and slope analysis allowed us to link sediment erosion with the exposure of primary sulphide minerals in the headwater. Zinc and lead entered the streamwater as aqueous phases or as suspended sediments. Secondary sources were localised in depositional stream areas due to topographical obstruction and a decrease in stream gradient. Sediment zinc and lead concentrations were lower in depositional areas and associated with Fe-oxide or phyllosilicates. Streamwater zinc and lead fluxes highlighted their mobility under high-flow conditions. This multi-disciplinary approach stressed the impact of the headwater mining work on the downstream catchment and provided a low-cost strategy to target sediment sampling via geomorphological observations. [ABSTRACT FROM AUTHOR]

Bed irregularities of water bodies play a significant role in many hydraulic and river engineering experiments and models. Accurate measurement of river geomorphology requires great fieldwork effort. Optimizing the dataset size of measured points will reduce the time and costs involved. In this study, the geomorphology of a gravel bed river reach was measured using different spatial acquisition methods. Digital elevation models were created for each measurement method and the volumes of under/overestimation were calculated. The results show that the sampling methods had more effect on the accuracy of the interpolated geomorphology than the density of the measured points. By choosing an optimized sampling method, the measurement efforts decreased to less than 50%, with negligible errors of around 15 m3 and 10 m3 over and underestimation, respectively, in a water body area of around 2200 m2. These findings help to provide more accurate geomorphological data with less effort as inputs for experimental and numerical models to derive better results. [ABSTRACT FROM AUTHOR]

Hundreds of ancient palaeolake basins have been identified and cataloged on Mars, indicating the distribution and availability of liquid water as well as sites of astrobiological potential. Palaeolakes are widely distributed across the Noachian aged terrains of the southern highlands, but Arabia Terra hosts few documented palaeolakes and even fewer examples of open‐basin palaeolakes. Here we present a detailed topographic and geomorphological study of a previously unknown set of seven open‐basin palaeolakes adjacent to the planetary dichotomy in western Arabia Terra. High resolution topographic data were used to aid identification and characterization of palaeolakes within subtle and irregular basins, revealing two palaeolake systems terminating at the dichotomy, including a ∼160 km chain of six palaeolakes connected by short valley segments. Analysis and correlation of multiple, temporally distinct palaeolake fill levels within each palaeolake basin indicate a complex and prolonged hydrological history during the Noachian. Drainage catchments and collapse features place this system in the context of regional hydrology and the history of the planetary dichotomy, showing evidence for both groundwater sources and surface accumulation. Furthermore, the arrangement of large palaeolakes fed by far smaller palaeolakes, indicates a consistent flow of water through the system, buffered by reservoirs, rather than a catastrophic overflow of lakes cascading down through the system. Plain Language Summary: Evidence for hundreds of ancient lakes has been found on Mars, but these features are not distributed uniformly across the surface, and the vast majority of evidence for past lakes and valleys on Mars is found within the ancient southern highlands of the planet. In this work we describe a newly discovered system of ancient lakes and river valleys which end at the geologically important boundary between the southern highlands and northern lowlands. Global catalogs of ancient lakes on Mars have generally relied on relatively low‐resolution imagery and topography, but for the small area covered in this study we were able to utilize high‐resolution imagery, and produce new high‐resolution topographic maps. This detailed approach allowed identification of multiple past water levels within each lake, and paired with an analysis of other features formed by lakes and rivers, we reconstructed a history of lake filling, drainage, and eventual decline and disappearance. These reconstructions reveal that drainage through the system was sustained over a prolonged period, rather than a single catastrophic event. Discovery and description of similar systems across Mars with these techniques will aid in placing further constraints on the history of liquid water and habitable environments on Mars. Key Points: A detailed local study of a system of seven previously unknown palaeolakes near the dichotomy in western Arabia Terra, MarsHigh resolution topographic data aids in identification and characterization of palaeolakes and regional hydrological historyEvidence for a prolonged history of fluvial and lacustrine processes, with palaeolakes fed by groundwater and surface accumulation [ABSTRACT FROM AUTHOR]

During the dry season of the years 2016–2020, the Gallinas River in San Luis Potosí State, Mexico, experienced a completeoss of its downstream flow. These events impacted the Tamul waterfall, a tourist attraction with economicosses for the region. To investigate the causes, this research focuses on identifying the flow variations in different river sections using the EFDC model under different scenarios to determine the causes of flowosses resulting in the disappearance of the waterfall. To set up the conditions, measurements of flow and speed, photogrammetry, bathymetry, and digital elevation modeling were necessary. The EFDC model was calibrated based on data acquired from measurement campaigns from 2017 to 2018. Five scenarios were established with different inflow boundary conditions: 1.5, 30, 60, and 1000 m 3 /s. According to the modeling results, it can be inferred that the mostikely reason for the flow variations in the river is the clandestine water extraction and the influence of the karst geomorphology of the river that would generate specific infiltrations. [ABSTRACT FROM AUTHOR]

This study investigates the mineralogical, elemental, and spatial variability from source (proximal) to sink (distal) of Merapi basalt‐andesitic stratovolcano (Java, Indonesia) to better constrain volcaniclastic mineral sorting in fluvial, aeolian, and coastal environments. Merapi volcaniclastics are products of an active volcano with an ongoing quadrennial eruption, which can provide insights to constrain Mars' older and more recent volcaniclastics by focusing on anorthite, albite, and pyroxenes found on Mars' surface. We collected stream sediment samples across the Opak River that connects Merapi with the Indian Ocean. In addition to grain size analysis, all collected samples were subjected to X‐ray diffractometer and X‐ray fluorescence to quantify their mineralogical and elemental composition, respectively, like the CHEMIN instrument used by the Curiosity rover on Mars to investigate the geochemistry and mineralogy of geological units in Gale crater. Implementation of multivariate statistical analysis based on principal component analysis and Hierarchical Clustering of Principal Component are able to discriminate between fluvial, fluvio‐coastal‐aeolian, and marine influenced deposits. The quantitative assessment shows that the dominant mineralogy is influenced by pyroclastic materials dominated by plagioclase feldspars (albite and anorthite), followed by pyroxenes (augite and enstatite). Alteration modeling of Merapi samples favors a fluvial depositional environment rather than mass‐wasting from the crater rim for Gale crater rocks (i.e., Pahrump Hills, Hartmann's Valley, Karasburg, Sutton Island member) on Mars. Plain Language Summary: This research provides a detailed characterization of stream samples and surface deposits from the Opak River, the Parangkusumo Shoreface, and parabolic coastal sand dunes from an active Merapi stratovolcano (Java, Indonesia) transported from the source toward the sink. The paper aims to constrain pyroclastic mineral sorting from a basaltic to basalt‐andesitic volcanic origin throughout fluvial, coastal, and wind‐driven (aeolian) environments. We use similar methods as the MSL (Mars Science Laboratory) Team to investigate mineral sorting of volcaniclastic sediments in Gale Crater, specifically using X‐Ray spectroscopy collected by CheMin. The results of our research suggest that mineralogical sorting occurs throughout the depositional subenvironments, and they are related to the geomorphology of the river. Furthermore, the aeolian environment provides an additional sorting mechanism for the sand grains deposited in the shoreface. We also discovered a similar weathering trend of Merapi volcanic sediments with the findings from Stimson and Murray formation in Gale Crater, which supports their origin as sediment transported by the river during the wet phase of Mars. Key Points: Volcanic cyclic eruption, fluvial discharge, longshore current, and coastal volcaniclastic aeolian sand dunes are all interconnected from shaping the geomorphology of a reworked volcaniclastic terrain in Merapi sedimentary systemsMineral sorting variability can be observed in sedimentary bedforms and is strongly controlled by grain sizeChemical alteration index supports the hypotheses of Gale Crater's ancient aeolian Stimson formation and aqueous‐driven alteration of Murray formation on Mars [ABSTRACT FROM AUTHOR]

Interspersed inputs of wood and sediment bring about morphological change at confluences and the extent to which these processes are modified by anthropogenic disturbance has ramifications for stream fish assemblages. In this study, we used a 2X2 design and mark-recapture methods to assess the influences of confluence size (> 0.6, < 0.6) and upstream land cover (dominantly forested or urban) on reach-scale habitat change, the movement rate of three functional groups of stream fishes, and fish assemblage change at four headwater confluences in a Gulf Coastal Plain drainage in the southeastern United States. We found little evidence to suggest that confluence size contributed to differences in upstream mainstream and downstream mainstem habitat characteristics. Land cover did cause reach-scale, dissimilarities in channel morphology, streamflow, and physical complexity. Therefore, we suggest that physical complexity affected fluvial geomorphic processes and regulated base flow, thus influencing the magnitude of reach-scale habitat change. Accordingly, greater movement by water-column specialists in our urban reaches suggest that land cover indirectly modified this functional group's ecological response to reach-scale habitat change. Furthermore, our results indicated that the degree of intra-reach, assemblage change was likely a corollary of channel morphology stability. Our understanding of the extent to which land cover alters the geomorphic and ecological gradients associated with headwater confluences will be critical to ensure the conservation of sensitive species whose fitness is dependent on the integrity of these habitats. [ABSTRACT FROM AUTHOR]

Long-term landscape evolution is controlled by tectonic and climatic forcing acting through surface processes. Rivers are the main drivers of continental denudation because they set the base level of most hillslopes. The mechanisms of fluvial incision are thus a key focus in geomorphological research and require accurate representation and models. River incision is often modeled with a stream power model (SPM) based on the along-stream evolution of drainage area and channel elevation gradient but can also incorporate more complex processes such as threshold effects and statistical discharge distributions, which are fundamental features of river dynamics. Despite their importance in quantitative geomorphology, such model formulations have been confronted with field data only in a limited number of cases. Here we investigate the behavior of stochastic-threshold incision models across the southeastern margin of the French Massif Central, which is characterized by significant relief and the regular occurrence of high-discharge events. Our study is based on a new dataset combining measurements of discharge variability from gauging stations, denudation rates from 34 basins from 10Be cosmogenic radionuclide (CRN) concentration measurements in river sediments, morphometric analysis of river long profiles, and field observations. This new dataset is used for a systematic investigation of various formulations of the SPM and to discuss the importance of incision thresholds. Denudation rates across the SE margin of the Massif Central are in the 20–120 mm kyr -1 (equivalent to mm/ka in the figures) range, and they positively correlate with slope and precipitation. However, the relationship with the steepness index is complex and supports the importance of taking into account spatial variations in parameters (D50 , discharge variability k , runoff) controlling the SPM. Overall, the range of denudation rate across the margin can mainly be explained using a simple version of the SPM accounting for spatially heterogeneous runoff. More complex formulations including stochastic discharge and incision thresholds yield poorer performances unless the spatial variations in bedload characteristics controlling incision thresholds are taken into account. Our results highlight the importance of the hypotheses used for such a threshold in SPM application to field studies and notably the impact of actual constraints on bedload size. [ABSTRACT FROM AUTHOR]

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This article addresses a major theme in fluvial geomorphology on which Professor Ken Gregory contributed much pioneering research, that of quantitative relations of morphological change to discharge variations. It examines the morphodynamics and processes of adjustment of river channels to flow characteristics on event to decadal timescales, using field and remote sensing data collected over a 40‐year period for a very active meandering reach of the River Bollin, northwest England. The free meandering and rapid rates of changes provide insight into response timescales and processes. Morphological variations and rates of change are analysed in relation to peak flow parameters. The results show that the sinuosity has continuously increased since a resetting of the planform by multiple cutoffs in 2001, this autogenic trend underlying the effects of flow events. Width of the channel has varied by 50% between map dates, corresponding to discharge characteristics of each 6‐year period and integrating the impacts of individual events. A trend of decrease in intensity of erosion and deposition and of narrowing for the period 2001–2019 is apparent and may be an indication of the recovery and adjustment time to the major morphological changes in 2001. Other possible influences include decline in sediment supply but no obvious external cause is identified. A feedback effect of lower process rates producing less sediment from banks which decreases rates of channel movement may be occurring. A major contributor to the process rate decline and narrowing could be an increase in riparian vegetation cover. Complex sequences of change between peak flow events emerge, unrelated to discharge magnitude or numbers of peak events, and a process of basal bank sedimentation followed by upper bank deposition is evident. Channel capacity varies by up to 30% year to year, which has major implications for variability of flood risk and floodplain inundation. [ABSTRACT FROM AUTHOR]

The transport and deposition of mud in rivers are key processes in fluvial geomorphology and biogeochemical cycles. Recent work indicates that flocculation might regulate fluvial mud transport by increasing mud settling velocities, but we lack a calibrated mechanistic model for flocculation in freshwater rivers. Here, we developed and calibrated a semi‐empirical model for floc diameter and settling velocity in rivers. We compiled a global data set of river suspended sediment concentration‐depth profiles and inverted them for in situ settling velocity using the Rouse‐Vanoni equation. On average, clay and silt (diameters <39 μm) are flocculated with settling velocity of 1.8 mm s−1 and floc diameter of 130 μm. Among model variables, Kolmogorov microscale has the strongest positive correlation with floc diameter, supporting the idea that turbulent shear limits floc size. Sediment Al/Si (a mineralogy proxy) has the strongest negative correlation with floc diameter and settling velocity, indicating the importance of clay abundance and composition for flocculation. Floc settling velocity increases with greater mud and organic matter concentrations, consistent with flocculation driven by particle collisions and binding by organic matter which is often concentrated in mud. Relative charge density (a salinity proxy) correlates with smaller floc settling velocities, a finding that might reflect the primary particle size distribution and physical hosting of organic matter. The calibrated model explains river floc settling velocity data within a factor of about two. Results highlight that flocculation can impact the fate of mud and particulate organic carbon, holding implications for global biogeochemical cycles. Plain Language Summary: The fate of fine sediment in rivers is important for understanding contaminant dispersal, organic carbon burial, and the construction of river floodplains and deltas. Individual grains of silt and clay dispersed in water settle under the pull of gravity at extremely slow rates. However, in natural rivers, these mud particles can aggregate together into larger structures called flocs, resulting in far faster settling rates. Here, we built on prior work from estuaries to develop a settling velocity model for flocculated mud in freshwater rivers. Our results demonstrate that mud settling velocity increases in rivers with less vigorous turbulence because turbulence can break flocs apart. Mud settling velocity also increases with greater concentrations of mud and particulate organic matter, which promote particle collisions and binding. Counterintuitively, settling velocity decreases with greater clay abundance and greater river water salinity, possibly due to how they affect organic matter in binding mud particles into flocs. Our results improve understanding of floc behavior in rivers and indicate potential links between the routing of mud and organic matter, river geomorphology, and global climate. Key Points: Turbulence, sediment concentration and mineralogy, water chemistry, and organics affect river floc size and settling velocityControlling variables are incorporated into a model for mud floc diameter and settling velocity in rivers calibrated on a global data setMud flocs in rivers can respond to river hydraulics and biogeochemistry with implications for the carbon cycle and fluvial morphodynamics [ABSTRACT FROM AUTHOR]

The evolution of the fluvial landscape is the result of controls and processes that can be observed by the adjustments a river makes to its hydrological regime. The Negro River is the sixth‐largest river in the world by water volume and contains two complex anabranching systems, the Anavilhanas and Mariuá archipelagos, and despite its importance, there is a lack of hydrological survey data on its multichannel reaches. The objective of this study was to analyse the fluvial dynamics of the lower Negro River and the morphodynamics of the Anavilhanas Archipelago channels in the Amazon basin. The analysed set of fluviometric surveys and cartographic data indicated that the average water velocity and depth of the channels were the most sensitive variables for water discharge variability. In addition, the reduction in the width/depth ratio of the channels in the Anavilhanas region is associated with an increased number of islands, but not with a fluvial transport capacity increase. These landforms play an important role in modulating flood wave dynamics in the lower reach of the Negro River. Seasonal water storage occurs in the channels and lakes of the archipelago due to the backwater effect caused by the Amazon River, which is the main control in the spatiotemporal variation of water discharge along the Anavilhanas Archipelago. [ABSTRACT FROM AUTHOR]

As tides propagate inland, they become distorted by channel geometry and river discharge. Tidal dynamics in fluvial‐marine transitions are commonly observed in high‐energy tidal environments with relatively steady river conditions, leaving the effects of variable river discharge on tides and longitudinal changes poorly understood. To study the effects of variable river discharge on tide‐river interactions, we studied a low‐energy tidal environment where river discharge ranges several orders of magnitude, the diurnal microtidal Tombigbee River‐Mobile Bay fluvial‐marine transition, using water level and velocity observations from 21 stations. Results showed that diurnal tidal attenuation was reduced by the width convergence in seaward reaches and height convergence of the landward backwater reaches, with the channel convergence change location ∼40–50 km inland of the bayhead and seaward of the largest bifurcation. River events amplified tides in seaward regions and attenuated tides in landward regions. This created a region of river‐induced peak amplitude seaward of the flood limit (i.e., bidirectional‐unidirectional current transition), allowing more tidal energy to propagate inland. Tidal currents were attenuated and delayed more by river discharge than water levels, making the phase lag dynamic. The river impacts on the tides were delineated longitudinally and shifted seaward as river discharge increased, ranging up to ∼180 km. Results indicated the longitudinal shifts of river impacts on tides in alluvial systems can be estimated analytically using the ratio of river discharge to tidal discharge and the geometric convergence of the system. Our simple analytical theory provides a pathway for understanding the tide‐river‐geomorphic equilibrium along increasingly dynamic coasts. Plain Language Summary: Coastal cities and ports are affected by tides and rivers, concentrating industry, infrastructure, and economies in regions where tide‐river interactions affect flooding, erosion, and water quality. Tide‐river interactions are commonly studied in stable rivers with large tides, limiting the variability of tide‐river interactions, leaving the effects of river discharge on tides poorly understood, and the risks for coastal communities during large river discharge events difficult to determine. To study the effects of river discharge on tide‐river interactions, observations in Alabama were investigated, spanning the Tombigbee River through Mobile Bay to the Gulf of Mexico. Results show that channel geometry and river discharge affected the tides. As river discharge increased, flood‐ebb tidal currents became seaward only, causing a region up to ∼180 km (110 miles) long to change from estuarine to riverine. The shift was captured in a simple equation using the river‐tidal energy ratio and generalized geometry, suggesting the affected region increases with the range of river discharge and that the greatest flooding and erosion risks to coastal communities can change between the sea and rivers. This simple equation provides a new tool for managers to understand tide‐river interactions now and under future changes from human development and sea level rise. Key Points: Along the fluvial‐marine transition, river discharge attenuated tides in landward regions and amplified tides in seaward regionsRegions of bidirectional tidal flow became unidirectional as river discharge increased, shifting the tidal river ∼180 km seawardPlanform channel geometry (e.g., width convergence) may not be a robust indicator of the transition in tide‐river hydrodynamics [ABSTRACT FROM AUTHOR]

American black bears are considered dependent on high‐elevation forests or other montane habitats in the drylands of western North America. Black bear sign, including that of cubs, was observed throughout the summers of 2015, 2016, and 2018 along a perennial desert river in the Sonoran Desert of Arizona. We analyzed the contents of 21 black bear scats, collected from May to October of 2016 and 2018. Apache cicada nymphs (Diceroprocta apache) were the dominant food item, occurring in 90% of scats and comprising an average of 59% of scat contents. In the process of excavating these nymphs, bears created large areas of turned‐over soil, a form of ecosystem engineering with potential implications for soils, vegetation, and fluvial geomorphology. Given that species distributions are shaped by physiological and ecological contexts, as well as anthropogenic legacies, it is possible that black bears once occurred more commonly in desert riparian systems prior to widespread agricultural development, hunting, and dewatering. Although more research is necessary, we suggest that desert riparian systems may be an alternative habitat for black bears. Better understanding the diet and habitat breadth of American black bears is important in the context of increasing landscape fragmentation and militarization in the U.S.‐Mexican borderlands. [ABSTRACT FROM AUTHOR]

This article presents the geomorphological mapping of the Kalamas river delta in Thesprotia (Epirus, north-western Greece). The Kalamas (also known as Thyamis) is one of the three main deltas of this region. Detailed mapping was performed through analysis of field geomorphological surveys and interpretation of old maps, satellite images, aerial photos, and DEM. The evolution of the delta as well as its current morphology derives from complex interactions between alluvial, marine dynamics and human activities. Several palaeochannels have been identified, and the recent morphology of the delta has been altered by the construction of a dam and the canalization of the river during the second half of the twentieth century. The coastline is complex, and mainly consists of lagoons, sandy barriers and sand spits. Since part of the delta has been prograding for about fifty years, the current dynamics indicate erosion as well as progressive submersion of these low coasts. [ABSTRACT FROM AUTHOR]

Imagined concepts – made real by down‐to‐earth field verification, validated modelling, and using available technologies and empirical methods – are fundamental to research outcomes in geomorphology. This article reviews the functions that consequential concepts have served: as overall driving and embracing stimuli, or playing permissive roles at lower levels within projects; when they have come to the fore and declined in usage; how knowledge of them gets spread and tested; and where needs seem to be driving for the future. Within fluvial geomorphology there is demonstrably a multiplicity of conceptual approaches. Modern times also now involve greater external appraisal including financial and management control and research and teaching quality assessments. These are taking place in parallel with novel environmental changes that themselves pose new needs for hazard understandings and safeguarding. Challenges to address for practical reasons include forecasting the likely future geomorphic effects of climate change, tracking system impacts from the spread of human hardware across landscapes, and monitoring pollutant incursions into fluvial systems. Nevertheless, conceptual progress in understanding is also fundamentally dependent on advancing 'blue skies' research objectives. In a changing world, geomorphology has to pursue holistic goals and the multi‐temporal and multi‐scale spatial appreciation of landform development, and how this relates to other changing global systems, but also to grow what it conceives of doing for the public good. [ABSTRACT FROM AUTHOR]

Floodplain inundation has been viewed as a type of binary process set by the relative elevation between river stage and levee crest. However, recent reports in the literature show that this perception may have limited applicability. In particular, through‐bank channels, conduits that cross the main river levees or banks, facilitate conditions for an "inundation continuum," or inundation for a range of sub‐bankfull flows. Moreover, through‐bank channels and their networks provide a direct hydraulic connection between the main river and the floodplain interior. We analyzed through‐bank channel structure and floodplain topography and compared them to river surface elevation to provide greater insight on floodplain inundation processes. Results show that well‐developed levees with through‐bank channels facilitate frequent through‐bank inundation. Where levees are poorly developed, floodplain inundation occurs by overbank flow. Therefore, for a given discharge through‐bank and overbank inundation may occur simultaneously. For the Congaree River floodplain, we infer that this dichotomy of inundation processes leads to temporally and spatially complex inundation flow paths for a given river stage. Further, our analyses reveal that the inundation continuum concept should be considered in the context of having vertical, longitudinal, lateral, and temporal components. Plain Language Summary: Floodplains are the flat landscapes adjacent to rivers that are frequently flooded when the water level in the main river exceeds the bank height, or at bankfull river stage. Recent studies show that this traditional view is not necessarily valid because river levees and banks are not uniformly developed. We analyzed and compared measured water levels with floodplain topography, including the main riverbanks. Results show that along‐channel variations in levee height allow water to enter the floodplain at levels below the bankfull stage, and when connected to a floodplain channel network, flooding quickly develops in the floodplain interior. Additionally, the levee structure can vary such that parts of a river reach experience overbank flooding while other parts experience through‐bank flooding. Such variability in flooding processes promotes spatially and temporally complex flow paths that together facilitate floodplain sustainability. This study sheds light on the continuum of floodplain flooding processes, and on the controls of inundation processes on flow complexity and the hydraulic connectivity of the landscape. Key Points: Floodplain inundation is a fuzzy process, and the inundation continuum includes vertical, longitudinal, lateral, and temporal dimensionsThrough‐bank and overbank inundation of the floodplain occurred, on average, 1.3 and 0.6 months per year, respectivelyA range of levee geometries promotes the simultaneous occurrence of overbank and through‐bank inundation for a single discharge [ABSTRACT FROM AUTHOR]

Despite acknowledgement of zoogeomorphological impacts and a positive trajectory for biogeomorphology, the cumulative geomorphic significance of animals remains largely unknown across geomorphic scales. We do not know the proportion of erosion, transport and deposition that is mediated by animal activity in different environments and cannot answer questions like how changing animal distributions under climate change will affect sediment fluxes and landscapes? This partly reflects a healthy skepticism about the net significance of biological energy and zoogeomorphic processes when set against the orthodox assumption that geophysical energy dominates. Zoogeomorphology is regarded as a "niche" interest, or worse, as inconsequential. Drawing on examples from fluvial geomorphology, this essay challenges that skepticism with the aim of encouraging greater consideration of the relevance of coupled biomorphodynamic systems. Five assumptions that belittle the role of animals are considered: that the number of species acting as geomorphic agents is small and their abundance limited; that limited geographical extent and periods of activity preclude widespread effects; and that impacts on sediment fluxes and morphological change are insignificant. In the hope that some skepticism is overcome, four interrelated challenges for future research are outlined: empirical investigation of zoogeomorphic processes, scaling‐up process understanding, embracing new technologies and approaches, and developing suitably integrated modeling tools. Such advances, alongside a willingness to recognize coupled biomorphodynamic interactions as the norm, rather than the exception, can improve our ability to understand both geomorphological and ecological phenomena and transform our understanding of how landscapes interact with the animals that live on, and in, them. This article is categorized under:Water and Life > Conservation, Management, and AwarenessWater and Life > Nature of Freshwater Ecosystems [ABSTRACT FROM AUTHOR]

Significant growth in mountain rivers research since 1990 has promoted the concept that canyon‐confined mountain rivers have complex topographic features nested from base‐ to flood‐stages due to canyon structure and abundant large bed elements. Nesting means literally structures inside of structures. Mathematically, nesting means that multiple individual features and repeating patterns exist at different frequency, amplitude, and phasing, and can be added together to obtain the complete structure. Until now, subreach‐scale landform structure, including nesting, has not been quantified sufficiently to understand morphodynamic mechanisms that control and respond to such organization. Geomorphic covariance structure analysis offers a systematic framework for evaluating nested topographic patterns. In this study, a threshold stage in mountain river inundation was hypothesized to exist. Above this stage landform structure is organized to be freely self‐maintaining via flow convergence routing morphodynamics. A 13.2 km segment of the canyon‐confined Yuba River, California, was studied using 2944 cross‐sections. Geomorphic covariance structure analysis was carried out on a meter‐resolution topographic model to test the hypothesis. River width and bed elevation had significantly less variability than previously reported for lower slope, partially confined gravel/cobble river reaches. A critical stage threshold governing flow convergence routing morphodynamics was evident in several metrics. Below this threshold, narrow/high "nozzle" and wide/low "oversized" were the dominant landforms (excluding "normal channel"), while above it wide/high "wide bar" and narrow/low "constricted pool" were dominant. Three‐stage nesting of base‐bankfull‐flood landforms was dictated by canyon confinement, with nozzle–nozzle–nozzle nesting as the top permutation, excluding normal channel. [ABSTRACT FROM AUTHOR]

This research presents a geomorphological map of the Entella River floodplain (scale 1:10,000), one of the largest and urbanized Ligurian Tyrrhenian flat area. The coastal floodplain suffered substantial modifications due to human activities since the latter half of the nineteenth century, which transformed the natural landscape into an anthropogenic environment. Fluvial, marine and anthropogenic geomorphological features have been investigated through a multi-temporal analysis and the reviewing, re-elaboration and summarization of previous geographical and geomorphological materials. An historical analysis has been performed to reconstruct morphological modifications and their correlation with anthropogenic interventions. The main geomorphological map includes a multi-temporal analysis of shoreline and major anthropogenic landforms. Small sketch maps on the geographical, geological and land use settings are also provided. The detailed geomorphological map can be used for urban and land planning, including the mitigation of the meteo- and geo-hydrological risk, which historically has dramatically influenced the Entella coastal floodplain. [ABSTRACT FROM AUTHOR]