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  • 1
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    Online Resource
    Elevation change and stability on a prograding delta
    American Geophysical Union (AGU) ; 2017
    In:  Geophysical Research Letters Vol. 44, No. 4 ( 2017-02-28), p. 1786-1794
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 44, No. 4 ( 2017-02-28), p. 1786-1794
    Abstract: The subaerial Wax Lake Delta is aggrading toward a stable elevation on a time scale of 16 years Higher elevations of the delta fluctuate around equilibrium as change is episodic, not continuous Peaks in elevation distributions do not necessarily indicate corresponding elevation equilibria
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Issue
    URL: Article
    DOI: 10.1002/grl.v44.4
    DOI: 10.1002/2016GL072070
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2017
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  • 2
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    Fluvial erosion/transport equation of landscape evolution models revisited
    American Geophysical Union (AGU) ; 2009
    In:  Journal of Geophysical Research Vol. 114, No. F3 ( 2009-07-30)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 114, No. F3 ( 2009-07-30)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2008JF001146
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2009
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    detail.hit.zdb_id: 2016800-7
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    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
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  • 3
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    Use of terrestrial photosieving and airborne topographic LiDAR to assess bed grain size in large rivers: a study on the Rhine River
    Wiley ; 2020
    In:  Earth Surface Processes and Landforms Vol. 45, No. 10 ( 2020-08), p. 2314-2330
    Details
    In: Earth Surface Processes and Landforms, Wiley, Vol. 45, No. 10 ( 2020-08), p. 2314-2330
    Abstract: Most grain size monitoring is still being conducted by manual sampling in the field, which is time consuming and has low spatial representation. Due to new remote sensing methods, some limitations have been partly overcome, but methodological progress is still needed for large rivers as well as in underwater conditions. In this article, we tested the reliability of two methods along the Old Rhine River (France/Germany) to estimate the grain size distribution (GSD) in above‐water conditions: (i) a low‐cost terrestrial photosieving method based on an automatic procedure using Digital Grain Size (DGS) software and (ii) an airborne LiDAR topo‐bathymetric survey. We also tested the ability of terrestrial photosieving to estimate the GSD in underwater conditions. Field pebble counts were performed to compare and calibrate both methods. The results showed that the automatic procedure of terrestrial photosieving is a reliable method to estimate the GSD of sediment patches in both above‐water and underwater conditions with clean substrates. Sensitivity analyses showed that environmental conditions, including solar lighting conditions and petrographic variability, significantly influence the GSD from the automatic procedure in above‐water conditions. The presence of biofilm in underwater conditions significantly altered the GSD estimation using the automatic procedure, but the proposed manual procedure overcame this problem. The airborne LiDAR topographic survey is an accurate method to estimate the GSD of above‐water bedforms and is able to generate grain size maps. The combination of terrestrial photosieving and airborne topographic LiDAR methods is adapted to assess the GSD over several kilometers long reaches of large rivers. © 2020 John Wiley & Sons, Ltd.
    Type of Medium: Online Resource
    ISSN: 0197-9337 , 1096-9837
    URL: Issue
    URL: Article
    DOI: 10.1002/esp.v45.10
    DOI: 10.1002/esp.4882
    Language: English
    Publisher: Wiley
    Publication Date: 2020
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    SSG: 14
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  • 4
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    Dynamic bedrock channel width during knickpoint retreat enhances undercutting of coupled hillslopes
    Wiley ; 2022
    In:  Earth Surface Processes and Landforms Vol. 47, No. 15 ( 2022-12), p. 3629-3640
    Details
    In: Earth Surface Processes and Landforms, Wiley, Vol. 47, No. 15 ( 2022-12), p. 3629-3640
    Abstract: Mountain landscapes respond to transient tectonic and climate forcing through a bottom‐up response of enhanced bedrock river incision that undermines adjoining hillslopes, thus propagating the signal from the valley bottom to the valley ridges. As a result, understanding the mechanisms that set the pace and pattern of bedrock river incision is a critical first step for predicting the wider mechanisms of landscape evolution. Typically, the focus has been on the impact of channel bed lowering by the upstream migration of knickpoints on the angle, length and relief of adjoining hillslopes, with limited attention on the role of dynamic channel width. Here, we present a suite of physical model experiments that show the direct impact of knickpoint retreat on the reach‐scale channel width, across a range of flow discharges (8.3 to 50 cm 3  s −1 ) and two sediment discharges (0 and 0.00666 g cm −3 ). During knickpoint retreat, the channel width narrows to as little as 10% of the equilibrium channel width, while the bed shear stress is 〉 100% higher immediately upstream of a knickpoint compared to equilibrium conditions. We show that only a fraction of the channel narrowing can be explained by existing hydraulic theory. Following the passage of a knickpoint, the channel width returns to equilibrium through lateral erosion and widening. For the tested knickpoint height, we demonstrate that the lateral adjustment process can be more significant for hillslope stability than the bed elevation change, highlighting the importance of considering both vertical and lateral incision in landscape evolution models. It is therefore important to understand the key processes that drive the migration of knickpoints, as the localized channel geometry response has ongoing implications for the stability of adjoining hillslopes and the supply of sediment to the channel network and export from landscapes onto neighbouring depositional plains.
    Type of Medium: Online Resource
    ISSN: 0197-9337 , 1096-9837
    URL: Issue
    URL: Article
    DOI: 10.1002/esp.v47.15
    DOI: 10.1002/esp.5477
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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  • 5
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    Supercritical river terraces generated by hydraulic and geomorphic interactions
    Geological Society of America ; 2018
    In:  Geology Vol. 46, No. 6 ( 2018-06-01), p. 499-502
    Details
    In: Geology, Geological Society of America, Vol. 46, No. 6 ( 2018-06-01), p. 499-502
    Type of Medium: Online Resource
    ISSN: 0091-7613
    URL: Article
    URL: Article
    DOI: 10.1130/G40071.1
    DOI: 10.1130/2018164
    Language: English
    Publisher: Geological Society of America
    Publication Date: 2018
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    SSG: 13
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  • 6
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    Performance of automated methods for flash flood inundation mapping: a comparison of a digital terrain model (DTM) filling and two hydrodynamic methods
    Copernicus GmbH ; 2021
    In:  Hydrology and Earth System Sciences Vol. 25, No. 6 ( 2021-06-03), p. 2979-2995
    Details
    In: Hydrology and Earth System Sciences, Copernicus GmbH, Vol. 25, No. 6 ( 2021-06-03), p. 2979-2995
    Abstract: Abstract. Flash floods observed in headwater catchments often cause catastrophic material and human damage worldwide. Considering the large number of small watercourses possibly affected, the use of automated methods for flood inundation mapping at a regional scale can be of great help for the identification of threatened areas and the prediction of potential impacts of these floods. An application of three mapping methods of increasing level of complexity is presented herein, including a digital terrain model (DTM) filling approach (height above nearest drainage/Manning–Strickler or HAND/MS) and two hydrodynamic methods (caRtino 1D and Floodos 2D). These methods are used to estimate the flooded areas of three major flash floods observed during the last 10 years in southeastern France, i.e., the 15 June 2010 flooding of the Argens river and its tributaries (585 km of river reaches), the 3 October 2015 flooding of small coastal rivers of the French Riviera (131 km of river reaches) and the 15 October 2018 flooding of the Aude river and its tributaries (561 km of river reaches). The common features of the three mapping approaches are their high level of automation, their application based on a high-resolution (5 m) DTM, and their reasonable computation times. Hydraulic simulations are run in steady-state regime, based on peak discharges estimated using a rainfall–runoff model preliminarily adjusted for each event. The simulation results are compared with the reported flood extent maps and the high water level marks. A clear grading of the tested methods is revealed, illustrating some limits of the HAND/MS approach and an overall better performance of hydraulic models which solve the shallow water equations. With these methods, a good retrieval of the inundated areas is illustrated by critical success index (CSI) median values close to 80 %, and the errors on water levels remain mostly below 80 cm for the 2D Floodos approach. The most important remaining errors are related to limits of the DTM, such as the lack of bathymetric information, uncertainties on embankment elevation, and possible bridge blockages not accounted for in the models.
    Type of Medium: Online Resource
    ISSN: 1607-7938
    URL: Article
    DOI: 10.5194/hess-25-2979-2021
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
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  • 7
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    HyLands 1.0: a hybrid landscape evolution model to simulate the impact of landslides and landslide-derived sediment on landscape evolution
    Copernicus GmbH ; 2020
    In:  Geoscientific Model Development Vol. 13, No. 9 ( 2020-08-31), p. 3863-3886
    Details
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 13, No. 9 ( 2020-08-31), p. 3863-3886
    Abstract: Abstract. Landslides are the main source of sediment in most mountain ranges. Rivers then act as conveyor belts, evacuating landslide-derived sediment. Sediment dynamics are known to influence landscape evolution through interactions among landslide sediment delivery, fluvial transport and river incision into bedrock. Sediment delivery and its interaction with river incision therefore control the pace of landscape evolution and mediate relationships among tectonics, climate and erosion. Numerical landscape evolution models (LEMs) are well suited to study the interactions among these surface processes. They enable evaluation of a range of hypotheses at varying temporal and spatial scales. While many models have been used to study the dynamic interplay between tectonics, erosion and climate, the role of interactions between landslide-derived sediment and river incision has received much less attention. Here, we present HyLands, a hybrid landscape evolution model integrated within the TopoToolbox Landscape Evolution Model (TTLEM) framework. The hybrid nature of the model lies in its capacity to simulate both erosion and deposition at any place in the landscape due to fluvial bedrock incision, sediment transport, and rapid, stochastic mass wasting through landsliding. Fluvial sediment transport and bedrock incision are calculated using the recently developed Stream Power with Alluvium Conservation and Entrainment (SPACE) model. Therefore, rivers can dynamically transition from detachment-limited to transport-limited and from bedrock to bedrock–alluvial to fully alluviated states. Erosion and sediment production by landsliding are calculated using a Mohr–Coulomb stability analysis, while landslide-derived sediment is routed and deposited using a multiple-flow-direction, nonlinear deposition method. We describe and evaluate the HyLands 1.0 model using analytical solutions and observations. We first illustrate the functionality of HyLands to capture river dynamics ranging from detachment-limited to transport-limited conditions. Second, we apply the model to a portion of the Namche Barwa massif in eastern Tibet and compare simulated and observed landslide magnitude–frequency and area–volume scaling relationships. Finally, we illustrate the relevance of explicitly simulating landsliding and sediment dynamics over longer timescales for landscape evolution in general and river dynamics in particular. With HyLands we provide a new tool to understand both the long- and short-term coupling between stochastic hillslope processes, river incision and source-to-sink sediment dynamics.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    URL: Article
    DOI: 10.5194/gmd-13-3863-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
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  • 8
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    Size, shape and orientation matter: fast and semi-automatic measurement of grain geometries from 3D point clouds
    Copernicus GmbH ; 2022
    In:  Earth Surface Dynamics Vol. 10, No. 6 ( 2022-12-02), p. 1211-1232
    Details
    In: Earth Surface Dynamics, Copernicus GmbH, Vol. 10, No. 6 ( 2022-12-02), p. 1211-1232
    Abstract: Abstract. The grain-scale morphology and size distribution of sediments are important factors controlling the erosion efficiency, sediment transport and the aquatic ecosystem quality. In turn, characterizing the spatial evolution of grain size and shape can help understand the dynamics of erosion and sediment transport in coastal, hillslope and fluvial environments. However, the size distribution of sediments is generally assessed using insufficiently representative field measurements, and determining the grain-scale shape of sediments remains a real challenge in geomorphology. Here we determine the size distribution and grain-scale shape of sediments located in coastal and river environments with a new methodology based on the segmentation and geometric fitting of 3D point clouds. Point cloud segmentation of individual grains is performed using a watershed algorithm applied here to 3D point clouds. Once the grains are segmented into several sub-clouds, each grain-scale morphology is determined by fitting a 3D geometrical model applied to each sub-cloud. If different geometrical models can be tested, this study focuses mostly on ellipsoids to describe the geometry of grains. G3Point is a semi-automatic approach that requires a trial-and-error approach to determine the best combination of parameter values. Validation of the results is performed either by comparing the obtained size distribution to independent measurements (e.g., hand measurements) or by visually inspecting the quality of the segmented grains. The main benefits of this semi-automatic and non-destructive method are that it provides access to (1) an un-biased estimate of surface grain-size distribution on a large range of scales, from centimeters to meters; (2) a very large number of data, mostly limited by the number of grains in the point cloud data set; (3) the 3D morphology of grains, in turn allowing the development of new metrics that characterize the size and shape of grains; and (4) the in situ orientation and organization of grains. The main limit of this method is that it is only able to detect grains with a characteristic size significantly greater than the resolution of the point cloud.
    Type of Medium: Online Resource
    ISSN: 2196-632X
    URL: Article
    URL: Article
    DOI: 10.5194/esurf-10-1211-2022
    DOI: 10.5194/esurf-10-1211-2022-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2736054-4
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  • 9
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    Statistical modelling of co-seismic knickpoint formation and river response to fault slip
    Copernicus GmbH ; 2019
    In:  Earth Surface Dynamics Vol. 7, No. 3 ( 2019-07-24), p. 681-706
    Details
    In: Earth Surface Dynamics, Copernicus GmbH, Vol. 7, No. 3 ( 2019-07-24), p. 681-706
    Abstract: Abstract. Most landscape evolution models adopt the paradigm of constant and uniform uplift. It results that the role of fault activity and earthquakes on landscape building is understood under simplistic boundary conditions. Here, we develop a numerical model to investigate river profile development subjected to fault displacement by earthquakes and erosion. The model generates earthquakes, including mainshocks and aftershocks, that respect the classical scaling laws observed for earthquakes. The distribution of seismic and aseismic slip can be partitioned following a spatial distribution of mainshocks along the fault plane. Slope patches, such as knickpoints, induced by fault slip are then migrated at a constant rate upstream a river crossing the fault. A major result is that this new model predicts a uniform distribution of earthquake magnitude rupturing a river that crosses a fault trace and in turn a negative exponential distribution of knickpoint height for a fully coupled fault, i.e. with only co-seismic slip. Increasing aseismic slip at shallow depths, and decreasing shallow seismicity, censors the magnitude range of earthquakes cutting the river towards large magnitudes and leads to less frequent but higher-amplitude knickpoints, on average. Inter-knickpoint distance or time between successive knickpoints follows an exponential decay law. Using classical rates for fault slip (15 mm year−1) and knickpoint retreat (0.1 m year−1) leads to high spatial densities of knickpoints. We find that knickpoint detectability, relatively to the resolution of topographic data, decreases with river slope that is equal to the ratio between fault slip rate and knickpoint retreat rate. Vertical detectability is only defined by the precision of the topographic data that sets the lower magnitude leading to a discernible offset. Considering a retreat rate with a dependency on knickpoint height leads to the merging of small knickpoints into larger ones and larger than the maximum offset produced by individual earthquakes. Moreover, considering simple scenarios of fault burial by intermittent sediment cover, driven by climatic changes or linked to earthquake occurrence, leads to knickpoint distributions and river profiles markedly different from the case with no sediment cover. This highlights the potential role of sediments in modulating and potentially altering the expression of tectonic activity in river profiles and surface topography. The correlation between the topographic profiles of successive parallel rivers cutting the fault remains positive for distance along the fault of less than half the maximum earthquake rupture length. This suggests that river topography can be used for paleo-seismological analysis and to assess fault slip partitioning between aseismic and seismic slip. Lastly, the developed model can be coupled to more sophisticated landscape evolution models to investigate the role of earthquakes on landscape dynamics.
    Type of Medium: Online Resource
    ISSN: 2196-632X
    URL: Article
    DOI: 10.5194/esurf-7-681-2019
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2736054-4
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  • 10
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    Investigation of stochastic-threshold incision models across a climatic and morphological gradient
    Copernicus GmbH ; 2022
    In:  Earth Surface Dynamics Vol. 10, No. 3 ( 2022-06-02), p. 473-492
    Details
    In: Earth Surface Dynamics, Copernicus GmbH, Vol. 10, No. 3 ( 2022-06-02), p. 473-492
    Abstract: Abstract. 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.
    Type of Medium: Online Resource
    ISSN: 2196-632X
    URL: Article
    URL: Article
    DOI: 10.5194/esurf-10-473-2022
    DOI: 10.5194/esurf-10-473-2022-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2736054-4
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