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Numerical models of landscape evolution

Eroding landscapes: fluvial processes. Numerical models of landscape evolution. Mikaël ATTAL. Acknowledgements: Jérôme Lavé, Peter van der Bee k and other scientists from LGCA (Grenoble) and CRPG (Nancy). Marsyandi valley, Himalayas, Nepal. Summary of last lecture.

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Numerical models of landscape evolution

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  1. Eroding landscapes: fluvial processes Numerical models of landscape evolution Mikaël ATTAL Acknowledgements: Jérôme Lavé, Peter van der Beek and other scientists from LGCA (Grenoble) and CRPG (Nancy) Marsyandi valley, Himalayas, Nepal

  2. Summary of last lecture At least 7 different fluvial erosion laws. - 3 “stream power laws” (erosion = f (A, S)) - 4 laws including the role of sediment (f(Qs) ≠ 1) Low amount of field testing but recent work strongly support that: - sediments exert a strong control on rates and processes of bedrock erosion (f(Qs) ≠ 1); - sediments could have “tools and cover effects”.

  3. Lecture overview I. Examples of models and applications II. The Channel-Hillslope Integrated Landscape Development model (CHILD)

  4. Numerical models of landscape evolution (2002) (2002) Willett, JGR, 1999:

  5. Numerical models of landscape evolution  3D 1) Examples of models and applications 2) The Channel-Hillslope Integrated Landscape Development model (CHILD)

  6. Tectonics Geomorphic modelling systems: simulate the evolution of a topographic surface under a set of driving erosion and sedimentation processes (CHILD, CASCADE, etc.) Climate parameters Hillslope transport + landslide threshold Initial topography Fluvial sediment transport + deposition + bedrock erosion Flexural isostasy Additional parameters and algorithms: fluvial hydraulic geometry, bedrock and sediment characteristics, role of vegetation, etc. CHILD

  7. Modelling landscape evolution • The elevation of each node changes through time under the effects of: • hillslope processes (erosion, transport, deposition), • fluvial processes (erosion, transport, deposition), • tectonics. Different models include different sets of parameters and/or treat the processes differently: no “universal” model of landscape evolution

  8. Modelling landscape evolution Models = fantastic tools integrating the effects of a wide range of processes in space and time, but… Processes are SIMPLIFIED, and some of them are badly constrained (e.g. fluvial incision laws, role of vegetation, etc.)  Need FIELD DATA to constraint parameters and processes. Combination of numerical modelling studies + field studies  test and calibration of models,  hypothesis testing,  sensitivity analysis.

  9. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) + Simple model (e.g. 1 fluvial incision law = under-capacity model, law 6) + Includes landsliding + User friendly  easily coupled with other models: thermal models for the lithosphere (van der Beek et al., 2002), tectonic models (Cowie et al., 2006) - Simple model (e.g. 1 fluvial incision law) - No rainfall variablility - Rigid mesh

  10. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 1: SE African margin (van der Beek et al., 2002) Margin formed during rifting 130 Ma ago. Height of topographic scarp ~1.5 km

  11. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 1: SE African margin (van der Beek et al., 2002) Aim: discrimination between 2 end-member models for the evolution of the margin

  12. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 1: SE African margin (van der Beek et al., 2002) Aim: discrimination between 2 end-member models for the evolution of the margin Coupling with thermal model for the lithosphere

  13. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 1: SE African margin (van der Beek et al., 2002) Aim: discrimination between 2 end-member models for the evolution of the margin Coupling with thermal model for the lithosphere

  14. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 1: SE African margin (van der Beek et al., 2002) Aim: discrimination between 2 end-member models for the evolution of the margin Preferred model: plateau degradation + lithologic variations

  15. JGR, 2002 CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 2: morphological response to the growth and lateral propagation of fault-related folds; application to the Siwaliks hills (Champel et al., 2002; van der Beek et al., 2002) Question: can variations in detachment dip explain differences in drainage patterns along the Himalayan front?

  16. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 2: morphological response to the growth and lateral propagation of fault-related folds; application to the Siwaliks hills (Champel et al., 2002; van der Beek et al., 2002) Question: can variations in detachment dip explain differences in drainage patterns along the Himalayan front?  dip of the detachment exerts a major control on drainage development: variations in dip could explain differences in drainage patterns along the Himalayan front

  17. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 3: landscape development in response to fault interaction and linkage in extensional settings (Cowie et al., 2006)

  18. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 3: landscape development in response to fault interaction and linkage in extensional settings (Cowie et al., 2006) Questions: are rivers flowing across active faults antecedent to tectonics? What is the effect of fault interaction on drainage patterns? What are the implications for sediment routing? Eliet & Gawthorpe, 1995

  19. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 3: landscape development in response to fault interaction and linkage in extensional settings (Cowie et al., 2006)

  20. CASCADE (Braun & Sambridge, 1997, van der Beek and Braun, 1999) Example 3: landscape development in response to fault interaction and linkage in extensional settings (Cowie et al., 2006)  Drainage patterns result from fault interaction  tectonic control on sediment routing and sediment fluxes to adjacent basins

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