GM2.3 | New approaches for monitoring and modelling sediment transport
EDI PICO
New approaches for monitoring and modelling sediment transport
Convener: Marijke de VetECSECS | Co-conveners: Anshul YadavECSECS, Shawn Chartrand, Laure Guerit, Rebecca Hodge
PICO
| Fri, 08 May, 08:30–10:15 (CEST)
 
PICO spot 3
Fri, 08:30
Sediment transport is a fundamental component of all geomorphic systems (including fluvial, aeolian, coastal, hillslopes and glacial), yet it is something that we still find surprisingly difficult both to monitor and to model. Robust data on where and how sediment transport occurs are needed to address outstanding research questions, including the spatial and temporal controls on critical shear stress, the influence of varying grain size distributions, and the impact of large magnitude events. Recent developments have provided a) new opportunities for measuring sediment transport in the field; and b) new ways to represent sediment transport in both physical laboratory models and in numerical models. These developments include (but are not limited to) the application of techniques such as seismic and acoustic monitoring, 3D imaging (e.g. CT and MRI scanning), deployment of sensors such as accelerometers, replication of field topography using 3D printing, use of luminescence as a sediment tracer, remote sensing of turbidity, discrete numerical modelling, and new statistical approaches.

In this session we welcome contributions from all areas of geomorphology that develop new methods for monitoring and modelling all types of sediment transport, or that showcase an application of such methods. Contributions from ECRs and underrepresented groups are particularly encouraged.

PICO: Fri, 8 May, 08:30–10:15 | PICO spot 3

PICO presentations are given in a hybrid format supported by a Zoom meeting featuring on-site and virtual presentations. The button to access the Zoom meeting appears just before the time block starts.
Chairpersons: Marijke de Vet, Anshul Yadav, Shawn Chartrand
08:30–08:35
08:35–08:37
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PICO3.1
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EGU26-22274
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ECS
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On-site presentation
Anne Baar, Brendan Murphy, Stuart McLelland, and Daniel Parsons

Coastal systems are highly dynamic environments where sand and mud are transported under the complex interactions of bathymetry, currents and waves. A better understanding of the natural dynamics at the scale of individual bars is required for a fundamental understanding of the formation of coastal environments and how they will respond to changes in the future. However, many coastal environments consist of spatially varying mixtures of sand and mud, while current sediment transport predictors and empirical relations of bar dynamics do not take into account the effect of cohesive sediment. The current research therefore aims to characterize the relative influence of clay on the direction of sediment transport and the resulting morphodynamic change of coastal bars under the combined action of waves and currents.

To this end, experiments were conducted in the Total Environment Simulator, a large-scale wave-current flume facility at the University of Hull (6m x 11m, 0.4m deep). The experimental setup consisted of a circular mound of a mixture of sand and clay, placed on top of a flat sand bed in the centre of the flume. The experimental conditions were systematically varied between runs, with 4 different clay percentages of the mound, and 5 different combinations of wave height and current velocity, while keeping the total bed shear stress constant. Flow velocity, water level and bed levels were monitored during each run, and the bed was scanned before and after each experiment.

Observations of the mound morphology show lateral diffusion due to sediment transport perpendicular to the wave direction under the influence of gravity, and streamwise migration due to sediment transport in the direction of the flow. Increasing the cohesivity altered the relative influence of the waves and currents on the direction of sediment transport and therefore the final shape of the mound. With increasing clay content, relatively more lateral and less streamwise transport occurred under the same hydrodynamic conditions. Furthermore, wave height had a greater control on the morphology with increasing clay content, since higher waves were more effective in winnowing out the clay into suspension and thereby mobilizing the sand fraction. These results imply that coastal and estuarine environments with spatially varying clay content will adapt differently to changing hydrodynamic conditions. In systems with a relatively high clay content, wave energy will have an important control on dynamics as it is needed to mobilize the sediment.

How to cite: Baar, A., Murphy, B., McLelland, S., and Parsons, D.: Cohesive sediments alter coastal bar dynamics under waves and currents, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22274, https://doi.org/10.5194/egusphere-egu26-22274, 2026.

08:37–08:39
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PICO3.2
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EGU26-19732
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ECS
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On-site presentation
Robert Houseago, Rebecca Hodge, Will Norris, and Takuya Inoue

Sediment entrainment thresholds in rivers have been widely studied, informing the prediction of bedload transport rates that underpin morphodynamic modelling. However, quantification of sediment entrainment in complex channels with varying degrees of bedrock exposure and sediment cover remains limited. Here, physical modelling was conducted to simulate a 1:10 scaled model of a bedrock reach from the River Garry in Scotland. Sediment entrainment thresholds were measured for isolated grains corresponding to selected percentiles of the bed grainsize distribution (D10, D50,  D90) over a bedrock surface with five sediment cover percentages (0, 25, 50, 75, 100%). Bed roughness metrics (e.g. standard deviation of bed elevation) of each bed were calculated. Sediment entrainment was found to be modulated by the bed roughness, resulting from the bedrock topography and infilling of depressions with sediments. Particle tracking revealed the spatial transport of sediment grains, along with the influence of localised bed roughness features on sediment dynamics.

How to cite: Houseago, R., Hodge, R., Norris, W., and Inoue, T.: Sediment transport in rough bed rivers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19732, https://doi.org/10.5194/egusphere-egu26-19732, 2026.

08:39–08:41
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PICO3.3
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EGU26-3492
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ECS
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On-site presentation
Gracia Salloum, Damien Trujillo, Franck Weingertner, Guillaume Gomit, and Sebastien Jarny

The erosion of riverbeds and banks in navigable channels controls the stability of the channel, the flow of sediment, and the maintenance of navigation depth. Understanding the erosion dynamics of natural sediments is crucial for predicting morphodynamical changes due to human-induced hydraulic influences.

This research examines the erosion characteristics of transitional fine to medium sand sediments from the Saône River (France), with the goal of establishing an empirical erosion law that connects hydraulic shear to sediment transport in these materials. Granulometric analyses revealed well sorted medium sand (D50 ≈ 140 –160 μm), suggesting weak cohesion yet hydraulically mobile beds. Flume experiments performed under regulated flow conditions demonstrated a gradual onset of erosion within a flow rate range of 26–47 l/s, indicating that incipient motion takes place along a continuum rather than at a specific critical threshold. Time-dependent experiments indicated an initial period of quick detachment succeeded by a decrease in erosion rate, influenced by surface armoring and a depletion of the easily entrainable fraction. Dimensionless transport data were fitted using the Meyer-Peter and Müller (1948) and Van Rijn (1984) expressed respectively as Φ = 140.3(θ − 0.07)4.43 and Φ =0.00153 d-0.3(θ/0.07 - 1)4.43 with R2 ≈ 0.74. The steep exponents highlight the nonlinear sensitivity of transport to excess shear stress, characteristic of transitional sediments. The derived relationships provide a quantitative foundation for predicting ship-induced erosion and sediment mobilization in navigable river systems.

This research was funded in whole or in part by the Agence Nationale de la Recherche (ANR) under project ANR-23-CE51-0032-01

How to cite: Salloum, G., Trujillo, D., Weingertner, F., Gomit, G., and Jarny, S.: Definition of an Erosion Law for Sediments of the Saône River, France, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3492, https://doi.org/10.5194/egusphere-egu26-3492, 2026.

08:41–08:43
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EGU26-3485
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Virtual presentation
Sebastien Jarny, Gracia Salloum, Guillaume Gomit, and Lionel Thomas

The accumulation of cohesive sediments is one of the most prominent issues in many tidal estuaries, as it has major implications on estuarine morphodynamics and on water quality and dredging strategies to support harbor activities. The work presented here focuses on the Gironde estuary, and more specifically on the Cadillac site located 40 km upstream of Bordeaux, where sediments were taken from the banks at low tide.

The first step was to characterise the physical properties of these materials by means of a granulometric analysis and rheological tests. Granulometric analysis (Mastersizer 3000, Malvern) is used to ensure the homogeneity of the sediments taken during the various campaigns. These reworked materials are then studied from a rheological point of view (HR2, TA Instruments) in order to identify in particular their yield stress for setting in motion. To do this, flow tests were carried out in a coaxial disc geometry in order to define the corresponding rheogram. The Hershel-Bulkley behaviour law is then applied to the descent curve to identify the yield stress. Once the protocol has been established, the effect of concentration is measured by diluting the sediments taken and the concentration is measured a posteriori by weighing the samples before and after drying. In this way, the law governing the evolution of yield stress as a function of concentration can be established.

Erosion tests were then carried out in a laboratory channel. The sediments were placed in the space left free between two ramps placed at the bottom of the channel. Initially, the threshold stress for setting the various samples in motion was established by gradually increasing the flow rate in the channel for a given height of water. The flow rate at which movement starts to occur on the sediment surface is noted. This flow rate is then translated into parietal stress on the bottom using PIV calibration on a rigid surface. It is assumed that the friction stress on the rigid bottom is equal to the minimum stress required to set the sediment in motion. These tests are repeated for different sediment concentrations. In a second phase, flows greater than the minimum flow are applied for 45 minutes and the quantity of sediment eroded is obtained by a double weighing method and by optical measurement using a 3D camera. In this way, the erosion rate, defined by the change in mass over time on a given reference surface, can be established and its evolution as a function of flow parameters and rheological properties can be determined. The final aim is to be able to propose an erosion law corresponding to the sediments of the Gironde estuary, which could then be used in numerical modelling.

This work was supported by the French National Agency for Research in the context of EMPHASE project (ANR-19-FQSM-0003).

This work pertains to the French Government program “Investissements d’Avenir” EUR INTREE, reference ANR-18-EURE-0010.

How to cite: Jarny, S., Salloum, G., Gomit, G., and Thomas, L.: Definition of an erosion law for cohesive sediments from Gironde estuary using rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3485, https://doi.org/10.5194/egusphere-egu26-3485, 2026.

08:43–08:45
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PICO3.5
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EGU26-7831
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ECS
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On-site presentation
Margaux Hofmann, Kyle Roskilly, Georgina Bennett, and Stuart N. Lane

Glacier-fed streams and their downstream ecosystems are influenced by bedload transport. An excess of bedload supply can lead to hazards, whilst an insufficiency can degrade in-stream habitats.  However, the processes by which bedload is mobilised and transported in such environments remain poorly understood, partly because its direct monitoring is challenging. Recent developments in micro-electromechanical systems (MEMS), particularly inertial measurement units (IMUs) for environmental applications, allow this gap to be addressed. Whilst IMU sensors have been primarily used for landslide and rockfall monitoring, their application to fluvial sediment transport is still emerging. Here, we use an innovative approach in which "smart rocks", rocks equipped with triaxial IMUs (accelerometers, gyroscopes, and magnetometers), are deployed in an Alpine proglacial environment. In combination with wireless data transmission, they can be described as “smart” as they can collect data autonomously and transmit it over quite long distances, via Long Range Wide Area Network (LoRaWAN) technology, which allows near real-time communication.

This work presents preliminary results from field tests conducted in autumn 2025 in the proglacial forefield of the Bas Glacier d’Arolla (Swiss Alps) in order to assess their applicability in a realistic alpine environment and to evaluate their potential for capturing bedload transport. Detailed results of a single particle during the flushing of hydropower infrastructure allow quantification of the forces associated with particle entrainment, transport, and resting phases. Central to the method are issues associated with data transmission and particle traceability. However, this preliminary work already demonstrates the potential of smart rocks as a promising tool for improving our understanding of bedload transport in alpine environments, especially for understanding sediment transport processes at the individual particle scale.

How to cite: Hofmann, M., Roskilly, K., Bennett, G., and Lane, S. N.: Using smart rocks to improve understanding of bedload transport in a proglacial forefield, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7831, https://doi.org/10.5194/egusphere-egu26-7831, 2026.

08:45–08:47
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PICO3.6
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EGU26-9287
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ECS
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On-site presentation
Marius Allebe, Dominik Brill, and Stéphane Bonnet

Luminescence is now used to date the exposure of rocks at the Earth’s surface or to measure their erosion rates. These methods are based on the observation that the luminescence of a rock exposed to sunlight is not only reset (bleached) at the surface but also at depth below the surface. For a stable surface, this bleaching depth (PBl) increases over time, forming a “bleaching front” that propagates into the rock interior. For an eroding surface, models show that a balance establishes between erosion and bleaching, and that PBl then depends on the erosion rate. Here, we present luminescence measurements performed on pebble surfaces sampled along a river in order to assess whether longitudinal variations in PBl could be used to quantify pebble transport durations or their abrasion (attrition).

Our study focuses on the Ardèche River (France), a ~120 km long river which is a tributary of the Rhône River. In its headwaters, in the Cévennes (french Massif Central), the eroded bedrock consists of Paleozoic metamorphic and plutonic rocks (including granites) and Quaternary volcanics. Then, along most of its course (~ 90 km) the river flows and cuts into Mesozoic carbonates. In its downstream end, it forms a  ~200 m deep and 30 km long gorge (“Gorges de l’Ardèche”), before connecting to the Rhône.

We consider here the luminescence of pebbles and cobbles sampled on twelve site along the Ardèche modern floodplain. For this purpose, we first characterized the granulometric distribution of alluvial bars on the 12 sites and then sampled granitic cobbles considering the D50 and D90 of the distributions.

Luminescence profiles (IRSL) of granite pebbles show PB1 depths ranging between 2 and 10 mm. For the D50 fraction, the luminescence signal reflects a progressive downward deepening of PB1, from the upstream area to the entrance of the gorges. Within the gorges, a slight reduction in PB1 depth is observed that we attribute to enhanced pebble abrasion within the gorges. Our results suggest that luminescence could form the basis of a new method for investigating the transport and abrasion of pebbles in fluvial systems.

 

How to cite: Allebe, M., Brill, D., and Bonnet, S.: Evaluation of luminescence techniques for investigating the transport and abrasion of pebbles in fluvial systems: the Ardèche River (France), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9287, https://doi.org/10.5194/egusphere-egu26-9287, 2026.

08:47–08:49
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PICO3.7
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EGU26-11627
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ECS
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On-site presentation
Bo-Yuan Chen and Wei-An Chao

Sediment transport is a fundamental process governing river hydraulics and channel morphology. During hyperconcentrated flows and flooding events, conventional optical and in situ sampling techniques are often unable to capture sediment transport behavior continuously. Previous studies have shown that contact-based hydroacoustic measurements can capture acoustic signals generated by particle impacts on the riverbed and enable continuous observations under high stream power conditions (Geay et al., 2017). However, contact-based hydroacoustic sensors are vulnerable to damage during flood events, resulting in high maintenance costs. To address this limitation, this study develops a low-cost, autonomous hydrophone system capable of continuous hydroacoustic recording. The system was tested in a large-scale field artificial channel constructed along the Landao Creek at Huisun Forest Station, Taiwan, where controlled discharges supplied from the upstream Nenggao Main Canal enabled experiments under dry-bed, steady-flow, and flood-peak conditions. To assess the performance of the autonomous hydrophone, a multi-physics sensing framework was established by synchronously deploying the hydrophone, a distributed acoustic sensing (DAS) system, and a microseismic sensor (SmartSolo). Under identical hydraulic and sediment supply conditions, hydroacoustic, ground vibration, and fiber-optic strain-rate signals were simultaneously recorded and analyzed to infer sediment transport behavior and riverbed activity. For data analysis, power spectral density (PSD) was employed as the primary frequency-domain method to analyze band-limited energy variations using a moving-window approach. In addition, waveform clipping events were detected and statistically analyzed to further identify high-energy transient events, which were used as an auxiliary indicator of bedload activity. The results indicate that the autonomous hydrophone reliably captures acoustic signatures associated with sediment transport and exhibits strong consistency with DAS strain-rate and microseismic observations, demonstrating its potential for integrated sediment transport monitoring in controlled artificial channel experiments.

 

Keywords: sediment transport; low-cost autonomous hydrophone; fiber-optic strain rate; microseismic signals

How to cite: Chen, B.-Y. and Chao, W.-A.: A Low-Cost Autonomous Hydrophone System Integrated with Multidisciplinary Observations for Sediment Transport Monitoring in a Large-Scale Field Artificial Channel, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11627, https://doi.org/10.5194/egusphere-egu26-11627, 2026.

08:49–08:51
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EGU26-13958
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ECS
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Virtual presentation
Abdullah Al Jahib, Md Asadullahil Galib Fardin, and Sameer Mahmud Khan

Being a country with heavy monsoon rains and seasonal flooding, every year Bangladesh faces severe damage, some of which are irreparable. The flood of 2024 which occurred in August, severely affected the north-eastern and south-eastern part of the country. Feni district was severely affected because of heavy water flow from the Dumboor dam in Tripura state. Subsequently, bringing massive amount of sediment load through the hilly area. These flooding events cause significant damage to human life in the region, the flood-associated sediment is also crucial for the region's agriculture. Therefore, the purpose of this study was to find the amount of sediment deposited due to the flood in the Feni floodplain. To achieve this objective, interferometry methods were used to create the Digital Elevation Models (DEMs) of the floodplains before and after the flood. To analyze the flood-plain state before the flood, two images were selected from 29th May to 10th June and two images were selected after the flood between 8th to 20th October. Single Look Complex (SLC) products were chosen, which consist of focused SAR data, geo-referenced using orbit , attitude data from the satellite and provided in slant-range geometry. The Sentinel-1 images were pre-processed . Than phase was unwrapped, and converted to DEM. The software SNAP, which is a common architecture of all Sentinel toolboxes, was used for DEM generation. After the DEM generation, 8 profiles were drawn to observe the change in topography due to sedimentation by HEC-RAS software. It was found that there was an average of 2.7 cm sediment deposition throughout the region and a 7.5 cm maximum deposition.

How to cite: Jahib, A. A., Fardin, M. A. G., and Khan, S. M.: Post-Flood Sediment Deposition Analysis Using SAR Interferometry: A Case Study of the 2024 Flood in Feni district, Bangladesh, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13958, https://doi.org/10.5194/egusphere-egu26-13958, 2026.

08:51–08:53
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PICO3.8
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EGU26-11075
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ECS
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On-site presentation
Guillaume Piasny, Pierre-André Garambois, and Laurent Schmitt

Lateral channel mobility is a key process controlling the morphodynamic evolution of large gravel-bed rivers, yet it remains difficult to represent numerically because of the strong coupling between flow hydraulics, sediment transport and bank erosion. This communication presents a data-driven approach for morpho-sedimentary model calibration, based on several complementary research articles derived from extensive field measurements and combining dense field instrumentation with a rich multi-sensor dataset to constrain detailed numerical models.

The proposed framework is applied to the morphodynamic modelling of an actively migrating meander of the Moselle River (north-eastern France), located within the Wild Moselle regional nature reserve. A multi-year field monitoring program included topo-bathymetric LiDAR surveys, water level records, ADCP velocity measurements, photogrammetric monitoring of bank erosion, direct (in situ) and indirect (hydrophone) bedload measurements, and particle mobility analyses using painted bed patches and RFID tracers.

A high-resolution 2D hydro-sedimentary model was implemented using TELEMAC-2D coupled with SISYPHE to investigate the processes governing meander dynamics. Model parameterization was constrained by in situ measurements, enabling the reproduction of observed flow patterns, sediment transport and bank erosion processes. Particular attention was paid to the contribution of bank-derived sediments to bedload transport and their role in channel morphodynamic.

Results show that the morpho-sedimentary model is capable of reproducing observed bank retreat, highlighting the potential of data-constrained two-dimensional approaches to represent inherently three-dimensional erosion processes. This modelling framework provides a robust basis for assessing future channel evolution and for exploring river management scenarios addressing lateral channel mobility and associated risks to infrastructure destabilization.

How to cite: Piasny, G., Garambois, P.-A., and Schmitt, L.: A data-driven framework for calibrating 2D morpho-sedimentary models in gravel-bed meandering rivers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11075, https://doi.org/10.5194/egusphere-egu26-11075, 2026.

08:53–08:55
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PICO3.9
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EGU26-12030
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ECS
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On-site presentation
Anshul Yadav and Rachel Glade

The movement of bedload sediment results from episodic grain motion involving hops and rests
controlled by hydrodynamic forces and collisions with the bed surface. Despite extensive research
studying the velocity distributions, there is no firm consensus regarding particle-scale dynamics,
particularly whether velocity distributions exhibit exponential-like or gamma-like characteristics.
In this work using high-resolution LES–DEM simulations, we investigate how observational
thresholds and flow conditions shape grain motion statistics. Our results demonstrate that velocity
threshold choices critically affect the observed distributions as including low-velocity events
produces exponential-like streamwise (vx) and Laplace-like cross-stream (vy) velocity distributions,
while filtering these events yields gamma and Gaussian forms. The streamwise velocity
distribution maintains its exponential character across flow intensities, but cross-stream
distributions evolve from Gaussian to Laplace-like as turbulent forcing strengthens. Fine-scale
analysis of velocity–acceleration phase space exposes highly asymmetric acceleration signatures
controlled by impact-driven collisions, whereas coarser temporal averaging generates symmetric
patterns. Hop distances exhibit Weibull-type distributions with stable scale factors, while the
relationship between hop length and duration transitions from quadratic to linear dependence
across all flow regimes, revealing inherent scale-dependent transport mechanisms. Throughout the
investigated conditions, bedload transport rates increase predominantly via nonlinear growth in the
number of mobile particles (particle activity), with mean particle velocities showing minimal
variation. These findings reconcile contradictory literature on bedload kinematics, emphasizing the
dominant role of particle mobilization dynamics, and reveal how measurement protocols introduce
systematic biases in grain-scale statistical characterization.

How to cite: Yadav, A. and Glade, R.: Temporal Resolution Controls on Ensemble Statistics of Bedload Transport, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12030, https://doi.org/10.5194/egusphere-egu26-12030, 2026.

08:55–08:57
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PICO3.10
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EGU26-13574
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ECS
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On-site presentation
Sahansila Shrestha, Francesca Pianosi, Elisa Bozzolan, Diane Doolaeghe, Nicola Surian, and Simone Bizzi

In this work, we employ Global Sensitivity Analysis (GSA) to quantify the robustness of sediment fluxes and sediment budgeting simulated at the river network scale. These simulations are subject to significant uncertainties when determining key drivers of transport capacity estimation, such as active transport width, river slope, or grain size distribution. These parameters, already difficult to estimate accurately at the scale of individual river cross-sections, become even more challenging to constrain at the network or entire river scale.  

We achieve this by applying the network scale sediment transport model, D-CASCADE (Dynamic CAtchment Sediment Connectivity And DElivery), to the 528 km long Po River basin in Northern Italy. D-CASCADE divides a river network into discrete units, termed ‘reaches’, and uses an empirical sediment transport formula to estimate how sediment is transported through this network. The river Po was divided into 35 reaches of homogenous geomorphic characteristics of a few kilometers each, and the model includes the input from 21 of its main tributaries.  We simulated the sediment transfer across this network for five hydrological years (2017-2021), with a daily time step.

Monte Carlo simulations were conducted using 1000 realizations, jointly perturbing the nominal value of 9 input parameters, such as active transport width, slope, roughness coefficient, and initial grain size distribution (GSD), for all the 35 reaches composing the Po River course. Specifically, the proposed methodology aims at assessing whether the plausible variations of the input parameters (that we established from field data and expert judgement) affect the nature of a river reach in the simulations, as sediment source (negative sediment budgeting), sink (positive sediment budgeting), or at equilibrium (sediment budget under a threshold), hence impacting its geomorphic behavior. The results indicated a strong robustness in classification, as no transition from source to sink was observed in any reach in the network. Nonetheless, some reaches shifted from being classified as either source or sink to

Regional Sensitivity Analysis (RSA) was then applied to identify which uncertain parameters have the greatest influence on such transitions. The RSA results showed that the active width, slope, roughness coefficient, and active layer depth are the primary input parameters affecting the river's state in gravel-dominated reaches, while the initial grain size distribution (GSD) is important in its sand-dominated reaches.

The presented approach applied to such network models allows for testing whether modelled river reaches maintain similar geomorphic behaviour despite the input uncertainties, while also identifying river network segments that exhibit an increased sensitivity and to which parameters. These insights can help prioritize efforts in data collection (known to be resource and time-demanding) and/or guide model calibration (known to be computationally expensive) towards parameters and locations whose improvements would most effectively reduce the final model uncertainty.

 

 

 

How to cite: Shrestha, S., Pianosi, F., Bozzolan, E., Doolaeghe, D., Surian, N., and Bizzi, S.: Are the source and sink behaviour simulated by a network-scale sediment transport model credible?  , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13574, https://doi.org/10.5194/egusphere-egu26-13574, 2026.

08:57–08:59
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PICO3.11
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EGU26-15663
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ECS
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On-site presentation
Marine Le Minor, Dimitri Lague, Jamie Howarth, and Philippe Davy

Catastrophic sediment release in fluvial systems is largely driven by landsliding that occurs naturally in mountain belts during extreme events, such as earthquakes or storms. Sediments are routed through the river system until they are stored either permanently in alluvial fans and lakes or temporarily in floodplains. The river response to such catastrophic sediment release has already been studied with 2D numerical models using a single effective grain size. Yet, in natural systems, sediment grain-size distributions can span several orders of magnitude and evolve during transport.

We present the new multi-grain-size sediment transport and sorting model SEDSCAPE (Sediment Entrainment Deposition and Storage based on the Concepts of Accessibility and Partial Equilibrium). This model was developed to predict how sediments of heterogeneous sizes that originate from landslides triggered by extreme events such as earthquakes and storms propagate through a river system. As modelling the 3D response of a river reach is computationally challenging, we couple SEDSCAPE with STRIMM (Lague, 2010), a model of river width evolution, to provide a simplified 2.5D approach. In turn, we can predict both morphodynamic changes and the full spectrum of sediment fluxes towards the floodplain and at the river outlet, and thus the sedimentary records in these locations.

We conducted numerical simulations of a constricted river reach consisting of a straight channel with floodplains on both sides. A time series of sediment and water discharges was applied to predict the response of a river reach affected by a landsliding event over several months to years. For comparison purposes, similar simulations were conducted with a single grain size.

Numerical simulations reveal: i) how different levels of sediment mobilization (water discharge) control sediment sorting processes and in turn sediment fluxes, ii) how the grain-size specific signals propagate in a river reach and are preserved in the channel and floodplain stratigraphy in response to a catastrophic sediment release, and ii) how the channel width adjusts with stochastic flow conditions and sediment supply.

The comparison between single- and multiple-grain-size simulations highlights the relevance of the multiple-grain-size approach to predict the response of a river reach to a catastrophic sediment release. Indeed, only the multi-grain-size approach is able to capture the hysteresis of transport, and different hysteresis patterns are obtained depending on the grain size as they have heterogeneous levels of mobilization and are not affected by sorting processes in the same way.

These results were obtained in the context of the SCALEES (Signature of sediment CAscades following Landslides triggered by Extreme Events in the Stratigraphy) project funded by the European Union. One key outcome of this project is the development of numerical models that will allow us to predict the full signal (all grain sizes) of sediment cascades preserved in stratigraphy in response to an extreme event. It will also pave the way for inverting the stratigraphic record of landslide-induced sediment cascades for quantitative insights into their response amplitudes and relaxation times.

How to cite: Le Minor, M., Lague, D., Howarth, J., and Davy, P.: Application of a coupled model of channel width evolution and multi-grain size sediment transport to predict the full signal (all grain sizes) of sediment cascades preserved in stratigraphy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15663, https://doi.org/10.5194/egusphere-egu26-15663, 2026.

08:59–10:15
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