Exploring the controls on long-term landscape evolution

Teaching workbook created as part of a group project at the CSDMS Spring School 2022.

Team members:

• Alex Lipp, Imperial College London
• Boontigan Kuhasubpasin, UCLA
• Jedidiah Dale, Washington University
• Marina Ruiz Sanchez-Oro, University of Edinburgh

Learning Goals

This is a modular course which allow students to explore the long-term evolution of landscapes using the Stream Power Law and Hillslope Diffusion models. During the course students will

• Understand how to implement a long-term landscape evolution model in LandLab.
• Demonstrate the effects of changing the diffusivity and erodibility parameters on landscape evolution
• Explore the impact of different spatial patterns of uplift
• Investigate the impact of orographic rainfall on landscape evolution
• Become familiar with the role of different lithological rock strength

Theory

Sediment diffusion and river incision process are essential tools that control landscape evolution.

Focusing on Sediment diffusion, the landscape evolves according to the equation:

where D is a hillslope diffusivity or transport-rate coefficient with dimensions of length squared per time and $z$ is elevation.

For a better understanding of the Sediment diffusion equation, see:

• Culling, W. (1963). Soil Creep and the Development of Hillside Slopes. The Journal of Geology 71(2), 127-161.

Focusing on the fluvial erosion process, the landscape evolves according to the equation:

where K_sp is the erodibility coefficient related with climate and lithology. m_sp and n_sp are positive exponents. These are usually thought to have the ratio:

A is drainage area and S is the slope of steepest descent. In -dz/dx, x is horizontal distance and z is elevation. U is an externally-applied rock uplift field.

For a great overview of the stream power equation, see:

• Whipple and Tucker, 1999 Dynamics of the stream-power river incision model: Implications for height limits of mountain ranges, landscape response timescales, and research needs, Journal of Geophysical Research.

According to the equations, there are several factors controlling surface evolution. In this notebook, we will explore the surface and river evolution as a result of diffusion erosion coefficient, lithology, uplift, and precipitation by using landlab, a Python-based modeling environment.

Method

In this repository, we use LandLab, a Python-based modeling environment, to allow students to understand how the diffusivity and erodibility coefficient, lithology, rock uplift rates, and precipitation all control the surface and river network evolution.

The major Landlab components that we will use in this notebook include FlowAccumulator, FastscapeEroder, LinearDiffuser, Lithology, LithoLayers, and SinkFillerBarnes.

Click the link below to explore the effect of each factor on long-term landscape evoluion.

We will explore...

1. Changing erosional parameters
2. Uplift pattern
3. Orographic precipitation
4. Lithology & Sediment Provenance

5. Synthesis - All variables at once

This lesson was part of the Community Surface Dynamics Modeling System (CSDMS) spring school 2022