Modelling sediment dynamics due to hillslope-river interactions: incorporating fluvial behaviour in landscape evolution model LAPSUS

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.

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To slide or not to slide: explicit integration of landslides and sediment dynamics in a landscape evolution model

10.5194/egusphere-egu2020-13064 ◽

2020 ◽

Author(s):

Benjamin Campforts ◽

Charles M. Shobe ◽

Philippe Steer ◽

Dimitri Lague ◽

Matthias Vanmaercke ◽

...

Keyword(s):

Landscape Evolution ◽

Sediment Dynamics ◽

Evolution Model ◽

Mitigation Strategies ◽

River Channels ◽

Stream Power ◽

Explicit Integration ◽

River Dynamics ◽

Fluvial Processes ◽

Source To Sink

Landslides are key agents of sediment production and transport. Ongoing efforts to map and simulate landslides continuously improve our knowledge of landslide mechanisms. However, understanding sediment dynamics following landslide events is equally crucial for developing hazard mitigation strategies. An outstanding research challenge is to better constrain the dynamic feedbacks between landslides and fluvial processes.&#160; Fluvial processes simultaneously (i) act as conveyor belts evacuating landslide-derived sediment and (ii) lower the hillslope&#8217;s base level triggering further landsliding. Landslides in turn can choke river channels with sediment, thereby critically altering fluvial responses to external tectonic or climatic perturbations.Here, we present HYLANDS, a hybrid landscape evolution model, which is designed to numerically simulate both landslide activity and sediment dynamics following mass failure. The hybrid nature of the model is in its capacity to simulate both erosion and deposition at any place in the landscape. This is achieved by coupling the existing SPACE (Stream Power with Alluvium Conservation and Entrainment) model for channel incision with a new module simulating rapid, stochastic mass wasting (landsliding).&#160;In this contribution, we first illustrate the functionality of HYLANDS to capture river dynamics ranging from detachment-limited to transport-limited configurations. Subsequently, we apply the model to a portion of the Namche-Barwa massive in Eastern Tibet and compare simulated and observed landslide magnitude-frequency and area-volume scaling relationships. Finally, we illustrate the relevance of explicitly simulating stochastic landsliding and sediment dynamics over longer timescales on landscape evolution in general and river dynamics in particular under varying climatologic and tectonic configurations.With HYLANDS we provide a hybrid tool to understand both the long and short-term coupling between stochastic hillslope processes, river incision and source-to-sink sediment dynamics. We further highlight its unique potential of bridging those timescales to generate better assessments of both on-site and downstream landslide risks.

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Implementation of runoff attenuation features into a landscape evolution model for the assessment of the impact on catchment sediment dynamics

10.5194/egusphere-egu2020-5008 ◽

2020 ◽

Author(s):

Eleanor Pearson ◽

Jonathan Carrivick ◽

Rob Lamb

Keyword(s):

Landscape Evolution ◽

Water Storage ◽

Flood Management ◽

Sediment Dynamics ◽

Evolution Model ◽

Small Catchment ◽

Management Schemes ◽

The Impact ◽

Grazing Livestock ◽

Over Time

Runoff attenuation features such as bunds and leaky barriers&#160;are increasingly incorporated into catchment flood management schemes. However, with any structure resulting in a barrier to flow, sediment dynamics are also affected, which will in turn affect the feature&#8217;s hydraulic effectiveness over time. The geomorphological impact of these features is often overlooked. This work looks at using the CAESAR-Lisflood landscape evolution model to assess how to implement runoff attenuation features into a catchment and evaluate their corresponding impact on sediment dynamics and subsequent change to water storage efficacy. The simulations were based on a small catchment, situated south of the Yorkshire Dales, UK, where the land is primarily used for grazing livestock. Features were implemented through the editing of the underlying topography&#160;allowing features to be fully erodible and scenarios were created based on feature shape, size and quantity. Of the features implemented, there was no unified response to the flood event simulated. Generally, many of the features themselves were affected by erosion, reducing their ability to hold water over time. Fewer features experienced deposition upstream compared to those experiencing erosion, which may suggest scour as opposed to sedimentation as a management issue that would need to be monitored. Nonetheless, the model scenarios run permitted an optimal design and layout of runoff attenuation features within the catchment to be established.

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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

10.5194/gmd-2020-74 ◽

2020 ◽

Author(s):

Benjamin Campforts ◽

Charles M. Shobe ◽

Philippe Steer ◽

Matthias Vanmaercke ◽

Dimitri Lague ◽

...

Keyword(s):

Sediment Transport ◽

Landscape Evolution ◽

Flow Direction ◽

Spatial Scales ◽

Sediment Dynamics ◽

Evolution Model ◽

Sediment Delivery ◽

River Dynamics ◽

River Incision ◽

The Impact

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 interaction among these earth 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 Topo Toolbox 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 in HyLands 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 is calculated using a Mohr-Coulomb stability analysis while landslide-derived sediment is routed and deposited using a multiple flow direction, non-linear 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 configurations. 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.

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