A probabilistic framework for the cover effect in bedrock erosion

Turowski, Jens M.; Hodge, Rebecca

doi:10.5194/esurf-5-311-2017

Cited by 32 publications

(47 citation statements)

References 44 publications

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“…For example, the crosssection saltation-abrasion model of Nelson and Seminara (2011) resolves flow hydraulics and channel width variations with high fidelity but cannot be feasibly applied at the landscape scale. Similarly, the bed cover evolution models of Turowski (2009), Hodge and Hoey (2012), Nelson and Seminara (2012), Johnson (2014), and Turowski and Hodge (2017) focus specifically on cover dynamics at the reach scale. While principles from these models could be incorporated into larger-scale landscape evolution models, several of the models (Hodge and Hoey, 2012;Nelson and Seminara, 2012;Johnson, 2014;Turowski and Hodge, 2017) are formulated for a fixed bedrock bed, thus limiting their potential for application to problems of long-term landscape evolution.…”

Section: Reach-scale Vs Landscape-scale Approachesmentioning

confidence: 99%

“…Similarly, the bed cover evolution models of Turowski (2009), Hodge and Hoey (2012), Nelson and Seminara (2012), Johnson (2014), and Turowski and Hodge (2017) focus specifically on cover dynamics at the reach scale. While principles from these models could be incorporated into larger-scale landscape evolution models, several of the models (Hodge and Hoey, 2012;Nelson and Seminara, 2012;Johnson, 2014;Turowski and Hodge, 2017) are formulated for a fixed bedrock bed, thus limiting their potential for application to problems of long-term landscape evolution. The 2-D mixed bedrock-alluvial models proposed by Inoue et al (2016Inoue et al ( , 2017 could potentially be incorporated into existing landscape evolution model frameworks, but the feasibility of such an integration is unclear as the models have been tested over hourly to daily timescales, not geologic timescales.…”

Section: Reach-scale Vs Landscape-scale Approachesmentioning

confidence: 99%

“…Their results support the experimental results of Chatanantavet and Parker (2008) showing that both the linear decline in exposure with increasing q s /q c and the abrupt shift from fully exposed to fully alluviated bed are possible, with the former occurring at low slopes and high bed roughness, and the latter occurring at high slopes and low bed roughness. Turowski and Hodge (2017) explicitly tracked erosion and deposition governing the transfer of particles between two mass reservoirs: the stationary particles on a non-erodible bedrock bed and the mobile particles in the water column. They showed that the relationship between bedrock exposure and q s /q c can take a wide range of forms depending on, among other factors, the probability of increasing bed cover for a given fraction of exposed bed.…”

Section: Approaches To Mass Conservationmentioning

confidence: 99%

“…The models of Hodge and Hoey (2012), Nelson and Seminara (2012), and Turowski and Hodge (2017) incorporate statements of sediment mass conservation to explore cover dynamics on a stationary bedrock bed. Hodge and Hoey (2012) used a cellular automaton model of alluvial cover evolution that allowed probabilistic entrainment and deposition of sediment on a non-eroding bedrock bed.…”

Section: Approaches To Mass Conservationmentioning

confidence: 99%

“…In doing this, our model follows a substantial number of previous contributions. Specifically, Hodge and Hoey (2012), Nelson and Seminara (2012), and Turowski and Hodge (2017) used explicit treatments of sediment morphodynamics to explore spatial and temporal changes in bed cover on a nonerodible bedrock bed in response to different forcings. Turowski (2009) used a stochastic sediment erosion and deposition framework in conjunction with the saltation-abrasion model for bedrock erosion to explore both cover variation and its influence on bedrock erosion rates.…”

Section: Comparison To Previous Channel Evolution Modelsmentioning

confidence: 99%

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The SPACE 1.0 model: a Landlab component for 2-D calculation of sediment transport, bedrock erosion, and landscape evolution

2017

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Abstract. Models of landscape evolution by river erosion are often either transport-limited (sediment is always available but may or may not be transportable) or detachmentlimited (sediment must be detached from the bed but is then always transportable). While several models incorporate elements of, or transition between, transport-limited and detachment-limited behavior, most require that either sediment or bedrock, but not both, are eroded at any given time. Modeling landscape evolution over large spatial and temporal scales requires a model that can (1) transition freely between transport-limited and detachment-limited behavior, (2) simultaneously treat sediment transport and bedrock erosion, and (3) run in 2-D over large grids and be coupled with other surface process models. We present SPACE (stream power with alluvium conservation and entrainment) 1.0, a new model for simultaneous evolution of an alluvium layer and a bedrock bed based on conservation of sediment mass both on the bed and in the water column. The model treats sediment transport and bedrock erosion simultaneously, embracing the reality that many rivers (even those commonly defined as "bedrock" rivers) flow over a partially alluviated bed. SPACE improves on previous models of bedrockalluvial rivers by explicitly calculating sediment erosion and deposition rather than relying on a flux-divergence (Exner) approach. The SPACE model is a component of the Landlab modeling toolkit, a Python-language library used to create models of Earth surface processes. Landlab allows efficient coupling between the SPACE model and components simulating basin hydrology, hillslope evolution, weathering, lithospheric flexure, and other surface processes. Here, we first derive the governing equations of the SPACE model from existing sediment transport and bedrock erosion formulations and explore the behavior of local analytical solutions for sediment flux and alluvium thickness. We derive steadystate analytical solutions for channel slope, alluvium thickness, and sediment flux, and show that SPACE matches predicted behavior in detachment-limited, transport-limited, and mixed conditions. We provide an example of landscape evolution modeling in which SPACE is coupled with hillslope diffusion, and demonstrate that SPACE provides an effective framework for simultaneously modeling 2-D sediment transport and bedrock erosion.

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Section: Reach-scale Vs Landscape-scale Approachesmentioning

confidence: 99%

Section: Reach-scale Vs Landscape-scale Approachesmentioning

confidence: 99%

Section: Approaches To Mass Conservationmentioning

confidence: 99%

Section: Approaches To Mass Conservationmentioning

confidence: 99%

Section: Comparison To Previous Channel Evolution Modelsmentioning

confidence: 99%

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The SPACE 1.0 model: a Landlab component for 2-D calculation of sediment transport, bedrock erosion, and landscape evolution

2017

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Bayesian geomorphology

Korup

2020

Earth Surf Processes Landf

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Summary The rapidly growing amount and diversity of data are confronting us more than ever with the need to make informed predictions under uncertainty. The adverse impacts of climate change and natural hazards also motivate our search for reliable predictions. The range of statistical techniques that geomorphologists use to tackle this challenge has been growing, but rarely involves Bayesian methods. Instead, many geomorphic models rely on estimated averages that largely miss out on the variability of form and process. Yet seemingly fixed estimates of channel heads, sediment rating curves or glacier equilibrium lines, for example, are all prone to uncertainties. Neighbouring scientific disciplines such as physics, hydrology or ecology have readily embraced Bayesian methods to fully capture and better explain such uncertainties, as the necessary computational tools have advanced greatly. The aim of this article is to introduce the Bayesian toolkit to scientists concerned with Earth surface processes and landforms, and to show how geomorphic models might benefit from probabilistic concepts. I briefly review the use of Bayesian reasoning in geomorphology, and outline the corresponding variants of regression and classification in several worked examples. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

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Sediment flux‐driven channel geometry adjustment of bedrock and mixed gravel–bedrock rivers

Baynes

Lague

Steer

et al. 2020

Earth Surf Processes Landf

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Sediment supply (Q s) is often overlooked in modelling studies of landscape evolution, despite sediment playing a key role in the physical processes that drive erosion and sedimentation in river channels. Here, we show the direct impact of the supply of coarse-grained, hard sediment on the geometry of bedrock channels from the Rangitikei River, New Zealand. Channels receiving a coarse bedload sediment supply are systematically (up to an order of magnitude) wider than channels with no bedload sediment input for a given discharge. We also present physical model experiments of a bedrock river channel with a fixed water discharge (1.5lmin À1) under different Q s (between 0 and 20gl À1) that allow the quantification of the role of sediment in setting the width and slope of channels and the distribution of shear stress within channels. The addition of bedload sediment increases the width, slope and width-to-depth ratio of the channels, and increasing sediment loads promote emerging complexity in channel morphology and shear stress distributions. Channels with low Q s are characterized by simple in-channel morphologies with a uniform distribution of shear stress within the channel while channels with high Q s are characterized by dynamic channels with multiple active threads and a non-uniform distribution of shear stress. We compare bedrock channel geometries from the Rangitikei and the experiments to alluvial channels and demonstrate that the behaviour is similar, with a transition from single-thread and uniform channels to multiple threads occurring when bedload sediment is present. In the experimental bedrock channels, this threshold Q s is when the input sediment supply exceeds the transport capacity of the channel. Caution is required when using the channel geometry to reconstruct past environmental conditions or to invert for tectonic uplift rates, because multiple configurations of channel geometry can exist for a given discharge, solely due to input Q s .

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A probabilistic framework for the cover effect in bedrock erosion

Cited by 32 publications

References 44 publications

The SPACE 1.0 model: a Landlab component for 2-D calculation of sediment transport, bedrock erosion, and landscape evolution

The SPACE 1.0 model: a Landlab component for 2-D calculation of sediment transport, bedrock erosion, and landscape evolution

Bayesian geomorphology

Sediment flux‐driven channel geometry adjustment of bedrock and mixed gravel–bedrock rivers

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