EFFECTS OF STRATIGRAPHIC VARIATION IN ROCK STRENGTH ON EROSION RATE PATTERNS IN LANDSCAPE EVOLUTION FROM NUMERICAL MODELS AND COSMOGENIC SAMPLING IN GRAND CANYON AND GRAND STAIRCASE

Over the last few decades, a suite of numerical models has been developed for studying river history and evolution that is almost as diverse as the subject of river history itself. A distinction can be made between landscape evolution models (LEMs), alluvial architecture models, meander models, cellular models and computational fluid dynamics models. Although these models share some similarities, there also are notable differences between them, which make them more or less suitable for simulating particular aspects of river history and evolution. LEMs embrace entire drainage basins at the price of detail; alluvial architecture models simulate sedimentary facies but oversimplify flow characteristics; and computational fluid dynamics models have to assume a fixed channel form. While all these models have helped us to predict erosion and depositional processes as well as fluvial landscape evolution, some areas of prediction are likely to remain limited and short-term owing to the often nonlinear response of fluvial systems. Nevertheless, progress in model algorithms, computing and field data capture will lead to greater integration between these approaches and thus the ability to interpret river history more comprehensively.

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Along-stream variations in valley flank erosion rates measured using 10Be concentrations in colluvial deposits from Atacama canyons: implications for valley widening

10.5194/egusphere-egu2020-2316 ◽

2020 ◽

Author(s):

Valeria Zavala ◽

Sebastien Carretier ◽

Vincent Regard ◽

Stephane Bonnet ◽

Rodrigo Riquelme ◽

...

Keyword(s):

Erosion Rate ◽

Landscape Evolution ◽

Sediment Flux ◽

Lower Probability ◽

Upward Migration ◽

Channel Mobility ◽

Erosion Rates ◽

Valley Flank ◽

Lateral Erosion ◽

Bed Slope

The downstream increase in valley width is an important feature of fluvial landscapes that may be evident to anyone: even if local exceptions exist, wide fluvial valleys in plains are distinctive of narrow upstream mountainous ones. Yet, the processes and rates governing along-stream valley widening over timescales characteristic of landscape development (>1-10 ka) are largely unknown. No suitable law exists in landscape evolution models, thus models imperfectly reproduce the landscape evolution at geological timescales, their rates of erosion and probably their response to tectonics and climate. Here, we study two 1 km-deep canyons in northern Chile with diachronous incision initiation, thus representing two time-stage evolutions of a similar geomorphic system characterized by valley widening following the upward migration of a major knickzone. We use 10Be cosmogenic isotope concentrations measured in colluvial deposits at the foot of hillslopes to quantify along-stream valley flank erosion rates. We observe that valley flank erosion rate increases quasi-linearly with valley-bed slope and decreases non-linearly with valley width. This relation suggests that lateral erosion increases with sediment flux due to higher channel mobility. In turn, valley width exerts a negative feedback on lateral valley flank erosion since channels in wide valleys have a lower probability of eroding the valley sides. This implies a major control of river divagation on valley flank erosion rate and valley widening. Our study provides the first data for understanding the long-term processes and rates governing valley widening in landscapes.

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Factors controlling the interaction between tectonics and surface processes in convergent orogens: insight from analogue and numerical models

10.5194/egusphere-egu2020-8014 ◽

2020 ◽

Author(s):

Riccardo Reitano ◽

Claudio Faccenna ◽

Francesca Funiciello ◽

Fabio Corbi ◽

Sean Willett

Keyword(s):

Landscape Evolution ◽

Numerical Models ◽

Tectonic Setting ◽

Laser Scanner ◽

Sprinkler System ◽

Surface Processes ◽

Oblique View ◽

Surface Uplift ◽

Geomorphic Features ◽

Set Up

Convergent orogens are the best places on Earth for studying the interaction between surface processes and tectonics. They display the highest surface uplift rates and in turn are more likely affected by erosion. The balance between tectonics and erosion is responsible for many aspects in the evolution of a mountain belt. Despite the growth of analysis techniques, our understanding is still limited by the impossibility to observe these processes through their entire evolution. In particular, understanding how single parameters affect the system is necessary to unravel the nature of these multiple-interrelated processes.Here we propose a new series of analogue models reproducing a simplified and scaled natural convergent orogenic system, to investigate the evolution of landscapes in which both tectonics and erosion/sedimentation are present. The growth of the orogenic wedge is driven by a rigid plate pushing the rear of the model. Deformed brittle granular material is a mixture of silica powder, glass microbeads and PVC powder. This mixture allows for the observation of both deforming structures and geomorphic features. Erosion is simulated by a water sprinkler system, providing a fine mist as precipitation which collects into simulated rivers, shaping the landscape. The model therefore allows observing the interaction between tectonics and surface processes. We analyze the model evolution monitoring oblique-view with cameras and top-view with a laser scanner. The latter is useful for measuring the mass balance between input fluxes (tectonics) and output fluxes (erosion) and in fulfilling a proper parametric study on the cause-effect relationship. The effect of different parameters on landscape evolution (e.g., precipitation rate, convergence velocity) is investigated systematically.Our preliminary results analyze the relationship between single parameters and their effect on the models, allowing a proper definition of the role played in the landscape evolution. We also set up a benchmark with numerical models using DACI3ELVIS code in the same tectonic setting.

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Bedrock river erosion through dipping layered rocks: quantifying erodibility through kinematic wave speed

Earth Surface Dynamics ◽

10.5194/esurf-9-723-2021 ◽

2021 ◽

Vol 9 (4) ◽

pp. 723-753

Author(s):

Nate A. Mitchell ◽

Brian J. Yanites

Keyword(s):

Wave Speed ◽

Rock Strength ◽

Numerical Models ◽

Rock Properties ◽

Kinematic Wave ◽

Stream Power ◽

New Approach ◽

Migration Rates ◽

Base Level ◽

Landscape Morphology

Abstract. Landscape morphology reflects drivers such as tectonics and climate but is also modulated by underlying rock properties. While geomorphologists may attempt to quantify the influence of rock strength through direct comparisons of landscape morphology and rock strength metrics, recent work has shown that the contact migration resulting from the presence of mixed lithologies may hinder such an approach. Indeed, this work counterintuitively suggests that channel slopes within weaker units can sometimes be higher than channel slopes within stronger units. Here, we expand upon previous work with 1-D stream power numerical models in which we have created a system for quantifying contact migration over time. Although previous studies have developed theories for bedrock rivers incising through layered stratigraphy, we can now scrutinize these theories with contact migration rates measured in our models. Our results show that previously developed theory is generally robust and that contact migration rates reflect the pattern of kinematic wave speed across the profile. Furthermore, we have developed and tested a new approach for estimating kinematic wave speeds. This approach utilizes channel steepness, a known base-level fall rate, and contact dips. Importantly, we demonstrate how this new approach can be combined with previous work to estimate erodibility values. We demonstrate this approach by accurately estimating the erodibility values used in our numerical models. After this demonstration, we use our approach to estimate erodibility values for a stream near Hanksville, UT. Because we show in our numerical models that one can estimate the erodibility of the unit with lower steepness, the erodibilities we estimate for this stream in Utah are likely representative of mudstone and/or siltstone. The methods we have developed can be applied to streams with temporally constant base-level fall, opening new avenues of research within the field of geomorphology.

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Bedload transport controls bedrock erosion under sediment-starved conditions

Earth Surface Dynamics ◽

10.5194/esurf-3-291-2015 ◽

2015 ◽

Vol 3 (3) ◽

pp. 291-309 ◽

Cited By ~ 23

Author(s):

A. R. Beer ◽

J. M. Turowski

Keyword(s):

Erosion Rate ◽

Landscape Evolution ◽

Bedload Transport ◽

Minor Importance ◽

Stream Power ◽

Catchment Scale ◽

Data Set ◽

Erosion Processes ◽

Bedrock Erosion ◽

Mountainous Landscape

Abstract. Fluvial bedrock incision constrains the pace of mountainous landscape evolution. Bedrock erosion processes have been described with incision models that are widely applied in river-reach and catchment-scale studies. However, so far no linked field data set at the process scale had been published that permits the assessment of model plausibility and accuracy. Here, we evaluate the predictive power of various incision models using independent data on hydraulics, bedload transport and erosion recorded on an artificial bedrock slab installed in a steep bedrock stream section for a single bedload transport event. The influence of transported bedload on the erosion rate (the "tools effect") is shown to be dominant, while other sediment effects are of minor importance. Hence, a simple temporally distributed incision model, in which erosion rate is proportional to bedload transport rate, is proposed for transient local studies under detachment-limited conditions. This model can be site-calibrated with temporally lumped bedload and erosion data and its applicability can be assessed by visual inspection of the study site. For the event at hand, basic discharge-based models, such as derivatives of the stream power model family, are adequate to reproduce the overall trend of the observed erosion rate. This may be relevant for long-term studies of landscape evolution without specific interest in transient local behavior. However, it remains to be seen whether the same model calibration can reliably predict erosion in future events.

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Blame it on the Weatherman: How critical is rainfall to geomorphology?

10.5194/egusphere-egu2020-13216 ◽

2020 ◽

Author(s):

Chris Skinner ◽

Nadav Peleg ◽

Tom Coulthard ◽

Peter Molnar

Keyword(s):

Landscape Evolution ◽

Numerical Models ◽

Temporal Variations ◽

Rainfall Data ◽

Fluvial Systems ◽

Sediment Yields ◽

Geomorphic Response ◽

Observation Methods ◽

Input Dataset ◽

Temporal Averaging

The geomorphic activity of fluvial systems at any scale is ultimately driven by precipitation often in the form of rain. In numerical models, such as landscape evolution models, an input dataset of rainfall is commonly used to drive the model, often using a coarse spatial and/or temporal averaging. Beyond availability, characteristics of the rainfall data itself are frequently overlooked and the impacts of these on the results of the model not considered. However, landscape evolution models are sensitive to spatial and temporal variations in rainfall data and rainfall observations themselves contain spatial and temporal uncertainties, the nature of which varies between different observation methods.This presentation synthesises the results of several linked studies highlighting the role rainfall can play in the modelling of geomorphology. First, we examine how the spatial and temporal resolution of the driving rainfall data is applied at influences the model outputs, with more than 100% difference in simulated sediment yields between the coarsest and finest resolutions used. Secondly, the role the source of the rainfall data plays, through comparison of observations from different methods, is explored showing that the uncertainty between the observations propagates non-linearly to simulated sediment yields.To investigate these sensitivities the CAESAR-Lisflood model was used in combination with the STREAP weather generator to produce high-resolution estimates of rainfall, conditioned by observations, for the longer timescales required for landscape evolution studies. This pairing opened up the opportunity to investigate changes of geomorphic response to future predicted changes to rainfields due to climate change, showing that this is more complex than when considering changes to rainfall volumes alone.

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From perched high elevation surfaces to sediment entering the foreland: the dynamics of erosion, deformation and landscape evolution in the Argentine Precordillera

10.5194/egusphere-egu2020-20270 ◽

2020 ◽

Author(s):

Gregory Hoke ◽

Pedro Val ◽

Gregory Ruetenik ◽

Robert Moucha

Keyword(s):

Numerical Modeling ◽

Landscape Evolution ◽

Numerical Models ◽

Foreland Basin ◽

Detrital Zircons ◽

Mountain Range ◽

Time Lags ◽

Cosmogenic Nuclide ◽

Stratigraphic Record ◽

Argentine Precordillera

The geomorphic processes that control temporal and spatial patterns of erosion, sediment storage and evacuation in an active mountain range (source) have a direct impact on how the signal of tectonics and climate, are recorded in the adjacent sedimentary basins (sinks). Stream power based numerical models of landscape evolution predict strong time lags between rock uplift and waves of erosion in the foreland, but this is difficult to test without proper resolution between source and sink signals..&#160; Confirmation of model results is typically gleaned through observations that are either snapshots of processes in modern systems, or inversion of the stratigraphic record to decipher what occurred in the uplands. While cosmogenic nuclide derived, catchment wide erosion rates in the modern rivers provide a snapshot of processes happening in the last thousands of years, thermochronmeters average over the &#8805; millions of years it takes a rock to ascend from the closure isotherm to the Earth&#8217;s surface,making it difficult, if not impossible to capture a minimally time averaged signal of the geomorphic system in the stratigraphic record. Paleoerosion rates from the residual cosmogenic nuclide concentration of buried sediments offer a means to bridge the gap in resolution.&#160;&#160;This study combines numerical modeling and cosmogenic nuclide paleoerosion rates in the Argentine Precordillera to build a rich picture of how this foreland basin system, from the hinterland through the foreland basin evolves in time and space. Our modeling shows that the dynamics of wedge-top basin formation behind a rising, and then subsequently inactive range have profound and systematic effects on the geomorphic signals both upstream and downstream of the wedge-top basin. Downstream, it is clear that there are strong, million year time lags in the uplift-triggered erosive pulse and spatial controls on where the sediment delivered to the foreland is sourced. Upstream, aggradation in the wedge top leads to the development of a wave of low erosion into the hinterland that results in the creation of perched surfaces coeval to erosive pulses downstream. In the Argentine Precordillera at 30&#176;S an 8 Ma record of paleoerosion rates from the wedge top and foreland basin deposits along with detrital zircons provenance in the foreland largely verifies the predictions of the numerical modeling. Similarly, upstream of the wedge-top basin, there are concordant knickpoints and large, broad planation surfaces perched some 1500 m above the floor of wedge top as predicted by the low erosion wave pulse. Our combination of numerical modeling and paleoerosion rates capture the dynamic evolution of mountain range at million to thousand year timescales.&#160;

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Formulation and Experimental Validation of a New Erosion Flow Model

Volume 1: Pipelines and Facilities Integrity ◽

10.1115/ipc2016-64064 ◽

2016 ◽

Cited By ~ 1

Author(s):

Rebecca Owston ◽

Dalton McKeon

Keyword(s):

Experimental Data ◽

Particle Size ◽

Empirical Data ◽

Erosion Rate ◽

Numerical Models ◽

Experimental Testing ◽

Fluid Viscosity ◽

New Model ◽

Functional Relationships ◽

Material Hardness

In the present work, a multivariable study has been conducted to systematically evaluate the effects of impact angle, material hardness, flow rate, sand concentration, particle size, and fluid viscosity on erosion. Experimental testing consisted of a submerged sand slurry jet impacting a flat plate in different orientations. Weight loss data, as well as profilometer surface scans have been collected on coupons to fully define the erosion. Empirical data trends were evaluated to provide insights into functional relationships between erosion rate and the parameters varied in the study. Interestingly, it was determined that scaling of experimental testing with regard to proppant concentration could be accomplished, since erosion rate normalized by the mass of sand impacting the eroded surface proved to be a constant. A total of five existing computational erosion models were evaluated against experimental data for both qualitative and quantitative performance. Results indicate that two models achieve relatively good comparison with experimental data without the need for case-specific tuning of model constants. This suggests that the use of these numerical models for erosion prediction in scenarios where tuning is not possible (due to lack of time/data), may still provide a reasonable estimate for the rate of material loss on equipment. As the culmination of experimental testing and computational benchmarking efforts, a new erosion model was also formulated. This model was based on both the experimental results and behavioral observations from existing submodels. The new model explicitly included contributions to erosion from the following variables: impact velocity, particle size, material hardness, and angle of impact. Improvement in simulated erosion rate agreement with empirical data was observed for all cases over existing submodels. However, those cases with higher particle diameters benefited the most. Using the new model, error compared to experiments was below 50% for all cases except one.

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