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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]

This paper reports a new variant of the model of the morphological pattern for thermokarst plains with fluvial erosion involving numerous remote sensing data. This variant of the model takes into account different trends of the thermokarst processes for watershed plains and lowered bottoms of khasyreis (drained thermokarst lakes). The model is tested at eight key sites differing in physiography, climate, and geocryology. Testing is based on high-resolution remote sensing data. The model is verified with a statistical analysis of lake area distributions within both watershed plain surface and lowered bottoms of khasyreis, demonstrating a state of dynamic balance in the course of emergence, growth, and drainage of the thermokarst lakes. The analysis shows that the morphological pattern of the thermokarst plains with fluvial erosion changes evolutionarily, with a reduction in the area of the main watershed surface according to a dependence close to exponential; the specific type of the dependence results primarily from the ratio of the lake generation density and the location density of the fluvial sources. [ABSTRACT FROM AUTHOR]

The residual oil in the fluvial reservoir of Gudong Oilfield is still widely developed even after decades of development. In order to explore the remaining oil in the subsurface fluvial reservoir, we need to have a better understanding on fluvial sandbody characteristics. This paper aims to demonstrate how to quantify anatomy on meandering fluvial architecture. Sedimentologic data from core descriptions of Guantao Formation in Gudong Oilfield were used to identify architectural elements. The upper Guantao Formation consists of ten lithofacies composing five different types of architectural elements. By integrating the available core, well logs, and seismic data, the fluvial sandbody distribution was analyzed. To characterize the fluvial channel geomorphology, we used seismic inversion to explore the stratigraphic correlation and stacking patterns of different channels, and the sandbody isopach map was obtained by the sandbody thickness in each layer. The architectural elements distribution in the plane was mapped by the sandbody isopach map and its profile characteristics. According to the investigation of meandering fluvial outcrops, subsurface meandering fluvial seismic geomorphology, and modern river morphology, the upstream-bar portions are always eroded because of the downstream channel migration. Statistics on the morphometric parameters (bar width/looplength, upstream deflection angle, downstream deflection angle, etc.) of modern meandering river (Ob River) were obtained from the Google Earth. It is found that the bar width/looplength and upstream deflection angle, upstream deflection angle and downstream deflection angle in modern meandering river have a good relationship, and we can have a quantitative architectural characterization on the point bar. This study quantified lithofacies thickness and proportion in different architectural elements of Guantao Formation, which ensures a high resolution anatomy on the small scale architecture. By using this method, the lithofacies proportion in each architectural element was computed, and through the statistics of architectural elements proportion in the Gudong Oilfield, the different lithofacies proportions in the block 6 can be computed. [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]

Fluvial geomorphology, which describes the form and processes of rivers, is increasingly being incorporated into river assessment procedures. However, the complexity of geomorphic processes makes a single universal and standardized assessment protocol a challenging and possibly impractical task. In this paper, we present a set of recommendations for choosing appropriate river assessment procedures and measuring geomorphic indicators to effectively capture important geomorphic processes required to support river management goals. We outline steps for building a river assessment procedure based on an adaptive approach rather than a one‐size‐fits‐all approach, where the geomorphic indicators, spatial and temporal scale, and methodologies used are carefully chosen based on the goals of the management project; the assessment aims to support. Guidance for choosing the appropriate geomorphic indicators is based on their significance (usefulness in characterizing the system), ease of measurement, and temporal scale needs. We also present recommendations on measurement techniques for each indicator while highlighting recent technological and methodological advancements that help overcome resource challenges often faced in river assessment. Given the wealth of scientific and technological developments in the field of geomorphology, it is possible to improve how geomorphic form and function are measured and incorporated into river assessments that support watershed management goals. [ABSTRACT FROM AUTHOR]

In his comment, Gabet summarized his critiques regarding our identification of migrating knickpoints in the Sierra and our estimates of both timing and magnitude of surface uplift made using a wide variety of independent measures of fluvial geomorphology. Here, we review the evidence we used to interpret particular features as migrating knickpoints in a transient landscape and demonstrate that the evidence presented by Gabet in no way shows these are stationary features that can be attributed to heterogeneous lithology alone. The challenges we faced and assumptions we made to determine timing from these river profile forms were summarized in the original paper and again in Gabet's comment. We chose a range-wide approach using systematic topographic analysis and an ensemble of methods precisely because we recognize the modern heterogeneity and dynamic late Cenozoic geologic history. With this approach, we identified trends in timing and magnitude of surface uplift that were consistent along much of the length of the range and in both tributary and mainstem rivers. We were able to identify signatures of late Cenozoic tilting amidst the influence of heterogeneous lithology, latitudinal climate gradients, drainage area exchange, and variable depositional histories. We hope that readers recognize that rather than ignoring local complexity, the tectonic mechanism of late Cenozoic westward tilt and the ensuing transient response can explain the diversity in observed geomorphology. Particularly, geomorphic features such as the along- and between-river variability in incision as well as the distribution and form of both mainstem and tributary knickpoints and knickzones can be reconciled when such a transient response is filtered through the heterogeneous lithology and basin area exchange characteristic of the west side Sierra Nevada. Thus, while challenges preclude pinpointing timing of the most recent tectonic event within the late Cenozoic using river profile forms alone, we maintain that a significant tectonic event perturbed Sierra river profiles in the past 11 million years. In many landscapes, an estimate with such a degree of uncertainty would not move the needle on our understanding but for the Sierra, where some contend no major tectonic event has occurred since the late Cretaceous, this uncertain estimate is valuable. [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]

Reach-scale river restoration or environmental water allocation (EWA) exercises typically address the magnitude and temporal dynamics (frequency, duration, timing, rate of change) of flows required to sustain desirable ecological conditions along a river. The role of geomorphology in this process is to broaden the gaze beyond flows to consider larger and longer-terminteractions between valley lithological structure, and the feed and fate of flow-sediment mixtures. This paper proposes the integration of numerical morphodynamic modelling in evaluations of environmental water requirements for non-perennial riverscapes (channel--riparian--floodplain environments). The paper presents a methodological framework, and proof of concept case study from the Touws River, South Africa, for the application of morphodynamic modelling in EWA. The paper illustrates operational approaches to modelling the complexity of dryland mixed bedrock-alluvial (and mixed-load) riverscapes with highly variable non-perennial flow regimes, including an approach to generating initial bed conditions for numerical experiments by 'morphodynamic spin-up', and approaches to synthesising and presenting numerical experiment output in the formof a dynamic range of potential variability inmetrics of physical habitat suitability and diversity, and disturbance/renewal regimes. Such efforts can assist in enhancing field observations and testing field-based hypotheses of flow-sediment regime--physical habitat associations, extending the timescales of analysis beyond field observation, and constraining uncertainty about the dynamic range of variability in responses to predicted future flow-sediment regime modifications. Further research is needed to develop growth models appropriate for key non-perennial river vegetation types, to support bio- morphodynamic modelling of geomorphology--vegetation interactions, and to determine or predict appropriate inlet sediment concentrations for historical and future modification scenarios. [ABSTRACT FROM AUTHOR]

Meandering rivers are complex systems that support high rates of biodiversity and the livelihoods of millions of inhabitants through their ecological services. Meandering rivers are often located in remote locations and cover long distances. As a result, observational satellites are crucial for investigating and monitoring meandering river dynamics. Satellite remote sensing technology is responsible for many advances in our knowledge about the variables that affect these rivers and their interaction with their surrounding floodplains. Furthermore, new sensors and the advent of cloud computing are allowing researchers to revisit theories that have hitherto lacked observational evidence to support them. In this paper, we review articles that have applied remote sensing techniques to analyse river meander migration processes. Our findings show that the majority of articles analysed the meandering rivers of the Ganges/Brahmaputra (29.0% of all articles) and the Amazon Basin (26.1%). We propose that these two locations are popular for different reasons: to improve management in highly populated floodplains of Ganges/Brahmaputra, and to investigate the meandering mechanisms without major anthropogenic interference in the Amazon Basin. Furthermore, most of the articles used Landsat for river monitoring (80.7%) and tracked the river changes throughout time using satellite time series (82.0%). However, the incorporation of Synthetic Aperture Radar satellites in papers was minimal, and only a small fraction (13%) of studies utilized cloud computing platforms for processing satellite images. Finally, we discuss new possibilities in terms of sensors and processing that might in the future advance our knowledge of river geomorphology. [ABSTRACT FROM AUTHOR]

This paper investigates, from a geomorphological and hydrogeological point of view, the development of piping-sinkhole phenomena at a retreating fluvial-terrace scarp along the lower Ticino River, near Casottole, northern Italy. Piping forms and features are well documented in the literature as complex soil erosion phenomena, usually associated with clayey or carbonate substrata, or to specific fluvial deposits. Such phenomena appear to have never been mapped in the lower Ticino area, and up to now, no evidence of piping-sinkhole occurrence in terraced alluvial plains strictly associated with terrace scarp erosion processes have been observed and reported in the literature. The geomorphological peculiarities of the area were assessed through field surveys, photographic and drone imaging, photointerpretation, and GIS analysis. Moreover, the riverbed morphological evolution was evaluated since the 1950s, and the hydrogeological conditions were analysed. Finally, a large piping-sinkhole database composed by 35 landforms was assembled in a WebGIS system. The piping-sinkhole phenomena were associated with the presence of perched water tables with flows towards the Ticino River, whose origin can be associated with site conditions, the large up dip network of surface water, and local irrigation practices. The research presented here provides a new contribution to the understanding of sinkhole occurrence and formation in previously unstudied terrace-scarp settings, and new insights for fluvial-terrace scarp modelling. Furthermore, it represents an important knowledge base to inform sustainable and effective measures for environmental management and hydrogeomorphic risk mitigation with reference to terrace scarp erosion and sinkholes. • First description of piping-sinkholes forms and features in the lower Ticino River • Large (up to 50 m) scarp piping-sinkholes straddle the retreating terrace scarp edge. • Decades of observations show direct relationship with river meander migration. • Piping-sinkholes can form suddenly causing important disruption. • The forms are still evolving due to a combination of natural and anthropic factors. [ABSTRACT FROM AUTHOR]

This paper presents new sedimentological, geomorphological, and optically stimulated luminescence (OSL) geochronological evidence for fluvial evolution of the mid- to lower River Tyne through the Lateglacial to late Holocene. These data reveal a series of fluvial terraces produced by cycles of aggradation and incision, conditioned by glacial inheritance and driven by changing sediment availability and hydrological regime. The distribution and stratigraphy (where available) of nine river terrace and their associated sediments have been recorded. At two key sites the sediments have been dated using OSL measurements to constrain the fluvial geomorphology. Significant entrenchment of the fluvial system, followed by aggradation formed the earliest fluvial terrace (T1), which encompasses environments spanning the transition from deglaciation into Greenland Interstadial 1 (GI-1). Incision below T1 began towards the end of GI-1, with three terraces (T2 – T4) between the abandonment of T1 and the early Holocene (15.0–9.2 ka). Climatic shifts, limited vegetation cover/soil development, and peri −/paraglacial landscape instability conditioned the development of the early postglacial fluvial landsystem. Three further terraces (T5 – T7) developed during the mid- to Late Holocene (6.6–3.1 ka), and comprise most of the valley floor. Climatic instability, glacial inheritance, and widespread anthropogenic disturbances are reflected in greater hillslope-channel coupling during this period. The extent of later Holocene terraces (T8 – T9) is limited as the river became isolated from flanking hillslopes entrenched between existing river terraces. Fluvial landscape evolution in formerly glaciated catchments is strongly conditioned by the cold stage legacy that introduced excess sediment and landscape instability into the catchment. Subsequent catchment-wide responses are variable and non-linear, with valley floors operating in a series of reach-wide responses. There is a need for greater chronological control to constrain the Lateglacial and Holocene evolution in the Tyne catchment, but also to further our understanding of region-wide responses to external drivers and local dynamics. • Lateglacial to late Holocene fluvial response recorded from river terrace sequence. • Fluvial landscape strongly conditioned by glacial legacy. • Catchment-wide responses are non-linear and valley floors operated as reach-wide responses. • River responded to climate and/or landscape perturbations at ∼16, 11.9, 8.7, 4 ka. [ABSTRACT FROM AUTHOR]

Braided river as a primary alluvial river pattern is of great importance on fluvial geomorphology, aquatic habitat, river exploitation and ecological protection. According to the literature review on braided rivers, the basic definition and morphological characteristics are described, and several classic methods and parameters of morphological characterization are introduced. In addition, field methods of obtaining high-precision DEM are summarized as well as the application of flume experiment and numerical model which advantages and disadvantages are pointed out, respectively. This paper describes the general composition of different morphological units of braided river, and lists the evolution mechanism of bar formation, anabranching adjustment and lateral migration, bank erosion and floodplain deposition. The primary controlling factors of morphodynamics and evolution of braided river, such as stream power, bed sediment particle size, sediment supply, riparian vegetation and valley width, are compared and analyzed. Meanwhile, a promising direction for alluvial river dynamics is to unravel formation causes, morphological characteristics, and fluvial processes of braided rivers with different spatial scales on the Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]

This paper documents the various factors contributing to the evolution of landforms in the Kosi River valley, Ukhaldhunga area of the Kumaun Himalaya, Uttarakhand. The area falls in the major tectonic boundary between the Lesser Himalaya and the sub-Himalaya. Passing through the Parewa-Ukhaldhunga-Dabara area, this tectonic contact is known as the Main Boundary Thrust (MBT), which is characterized by presence of varied landforms. Study of the development of geomorphology, particularly those evolved in the MBT zone, suggests that the morphological features are intimately associated with the tectonic activities related to the movement of rocks along the MBT and the surface processes such as fluvial and mass movement. The various landforms observed in the MBT zone include strath terraces, fill terraces, paleochannels and V-shaped valley that pertain to fluvial genesis; gravity induced landforms such as landslide debris and colluvial fans; and tectonic landforms such as linear fault traces, swerving/swing of river course and linear depressions. Signature of recent tectonic activity along the MBT is observed between Dabara and Khakrakot. The activity is evident in the form of 8-km-long active fault trace trending NW-SE. Normal fault related landforms are observed in the hanging wall block of the MBT. Neotectonic strath terraces and fill terraces are well developed in the MBT zone. Multiple events of recurrence of landslides are evident from exposed section of landslide debris fans. The bedrocks are highly sheared, suggesting successive tectonic movements along the MBT. As a consequence, tectonic wedges have developed in the bedrocks. These wedges have facilitated for the recurrence of a number of landslides. The anthropogenic activities have also aggravated the slope stability. Truncation of older debris fan surfaces by an erosional/fault scarp is observed and the scarp separates the older fans from the youngest debris fan deposit. The scarp runs parallel to the MBT and Kosi River. Swerving of the Kosi River is as a result of the tectonic forcing along active lineaments/faults. The trend of lineaments of the maximum and high density is NE-SW, which is transverse to the trend of the NW-SE trending Himalayan fold-thrust belt. [ABSTRACT FROM AUTHOR]

• IDI variation showed a decreasing trend in 2000–2010, followed by an increasing trend up to 2019. • Frequency of smaller, immobile bars is high as compared to the medium and larger bars which controls the IDI. • Multi-regression analysis shows peak flood stream power is better correlated to IDI variation. • Disorderness of the braided reach highlights existence of hierarchical energy dissipation. Understanding the morphological erraticism for large braided river systems is still a challenging issue in the present era of fluvial geomorphology. The present paper reports thorough spatio-temporal variability of sand bar dynamics (2000–2019) and their influence on the braided belt disorderness in the large braided Brahmaputra River. The sand bar area is detected using the modified normalized difference water index (MNDWI), and an entropy-based intensity disorder index (IDI) is further proposed to measure the spatio-temporal disorderness in the post-monsoon period. The IDI varies at a lowest value of less than 0.5 to a highest value of more than 0.9 for the selected study reach. Interestingly, IDI displays a declining trend for the first decade, followed by an increasing trend in the subsequent time slice, which signals the large-scale heterogeneity in process-form interactions for the Brahmaputra. An attempt was made to establish relationship between IDI, stream power derivatives (monsoon, peak flood, and post-monsoon), and bar area classes in order to facilitate a process-based understanding of the geomorphic adjustments. In comparison with other stream power derivatives, the peak-flood stream power showed a better correlation with the disorderness measure of the reach. Finally, this study has highlighted that smaller, highly immobile bars have significant control on the IDI variations and govern the yearly planform disorderness of the Brahmaputra. Further, the findings of this study can be used to construct a process-form-interaction framework for large braided river systems. [ABSTRACT FROM AUTHOR]

Present-day river forms and processes are in many cases conditioned by the consequences of anthropogenic modifications such as dams, embankments and gravel mining. Fluvial geomorphologists have typically investigated the effects of these human impacts using a so-called expert-based approach, whereby observed association or synchronicity between geomorphological changes and a given, preidentified impact, are interpreted as evidence of causation. This approach has important limitations when the effects of multiple human interventions interact along the same river corridor or overlap with the legacy of natural changes affecting the sediment - water balance. In such situations, the establishment of causal links between channel morphology and single impacts is not as straightforward as commonly assumed and the conclusions are susceptible to 'confirmation biases'. In this paper we highlight this risk through an assessment of human impacts on the Rhône River within a multi-driver context. The French Rhône is an excellent example of an Anthropocene river impacted by two main development phases during the twentieth century: embankments (1890s–1930s) followed by a series of multiple dams (1950s–1990s). We began by laying out several geomorphologically consistent hypotheses for the geomorphological trajectory of the Rhône over the twentieth century. Next, we tested these hypotheses against grain size data collected in the field in a structured and hypothesis-oriented way. Using this hypothesis-driven and deductive attribution analysis we identified the relative impacts of the different development phases on the present-day grain size distribution and in particular on armouring in the Rhône River, and proposed a hierarchy of dominant drivers of geomorphological change along the Rhone over the last century and a half. Our results led us to conclude that in the case of the Rhône, the effect of dams on armouring was negligible compared to a legacy of natural heritages and embankments. [ABSTRACT FROM AUTHOR]

The process of interpretation, and the ways in which knowledge builds upon interpretations, has profound implications in scientific and managerial terms. Despite the significance of these issues, geomorphologists typically give scant regard to such deliberations. Geomorphology is not a linear, cause-and-effect science. Inherent complexities and uncertainties prompt perceptions of the process of interpretation in geomorphology as a frustrating form of witchcraft or wizardry — a dark art. Alternatively, acknowledging such challenges recognises the fun to be had in puzzle-solving encounters that apply abductive reasoning to make sense of physical landscapes, seeking to generate knowledge with a reliable evidence base. Carefully crafted approaches to interpretation relate generalised understandings derived from analysis of remotely sensed data with field observations/measurements and local knowledge to support appropriately contextualised place-based applications. In this paper we develop a cognitive approach (Describe-Explain-Predict) to interpret landscapes. Explanation builds upon meaningful description, thereby supporting reliable predictions, in a multiple lines of evidence approach. Interpretation transforms data into knowledge to provide evidence that supports a particular argument. Examples from fluvial geomorphology demonstrate the data-interpretation-knowledge sequence used to analyse river character, behaviour and evolution. Although Big Data and machine learning applications present enormous potential to transform geomorphology into a data-rich, increasingly predictive science, we outline inherent dangers in allowing prescriptive and synthetic tools to do the thinking, as interpreting local differences is an important element of geomorphic enquiry. [Display omitted] • A multiple lines of evidence approach to geomorphic enquiry is proposed. • A cognitive framework outlines the transformation of data into knowledge. • Reading the landscape is contextualised in a Describe-Explain-Predict approach. • Plural knowledges relate Big Data to field insights and local/traditional knowledge. • Examples interpret the character, behaviour and evolution of landscapes. [ABSTRACT FROM AUTHOR]

This paper describes the evolution of a sector of the southern coastal plain of the Pelotas Basin, southern Brazil, between the last Pleistocene sea-level lowstand and the Holocene highstand, based on geomorphology and high-resolution stratigraphy. A fluvial drainage system associated with an incised valley developed during the Last Glacial Maximum (LGM) was identified. Two high-resolution 2D and 2.5D geophysical profiles using Ground-Penetrating Radar (GPR) show a Pleistocene fluvial system's former path, starting close to its present mouth inside Mirim Lagoon crossing the coastal barriers and reaching the inner continental shelf, covering some 60 km across the coastal plain. During the LGM, with the sea-level at −120 to −130 m and the coastline positioned close to the shelf edge (distant 200 km from the present coastline), the fluvial system excavated a ~31.5-m deep channel. Two cores, 36 and 32 m long, show that the paleochannel was filled with sedimentary deposits after 19.4 ka BP, and the facies succession represents the transition from fluvial, to estuarine, to the coastal barrier, and finally to inner shelf depositional environments, generated by processes connected to LGM and the Postglacial Marine Transgression (PMT). The study region behaved as a sediment by-pass zone, connecting the adjacent coastal plain's inner portion with the inner continental shelf. The studied area presents an unusual record of the LGM at a coastal plain domain. [Display omitted] • Records of the Last Glacial Maximum on the coastal plain. • Coastal stratigraphy transition: from basal fluvial to coastal barrier deposits. • Integrating GPR records and Drill Holes data on coastal evolution investigation. • Seismic facies and radarfacies as proxies for coastal evolution. • First record of continuous paleochannel in Southern Brazil. [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]