Abstract

Abstract. Models of landscape evolution provide insight into the geomorphic history of specific field areas, create testable predictions of landform development, demonstrate the consequences of current geomorphic process theory, and spark imagination through hypothetical scenarios. While the last 4 decades have brought the proliferation of many alternative formulations for the redistribution of mass by Earth surface processes, relatively few studies have systematically compared and tested these alternative equations. We present a new Python package, terrainbento 1.0, that enables multi-model comparison, sensitivity analysis, and calibration of Earth surface process models. Terrainbento provides a set of 28 model programs that implement alternative transport laws related to four process elements: hillslope processes, surface-water hydrology, erosion by flowing water, and material properties. The 28 model programs are a systematic subset of the 2048 possible numerical models associated with 11 binary choices. Each binary choice is related to one of these four elements – for example, the use of linear or nonlinear hillslope diffusion. Terrainbento is an extensible framework: base classes that treat the elements common to all numerical models (such as input/output and boundary conditions) make it possible to create a new numerical model without reinventing these common methods. Terrainbento is built on top of the Landlab framework such that new Landlab components directly support the creation of new terrainbento model programs. Terrainbento is fully documented, has 100 % unit test coverage including numerical comparison with analytical solutions for process models, and continuous integration testing. We support future users and developers with introductory Jupyter notebooks and a template for creating new terrainbento model programs. In this paper, we describe the package structure, process theory, and software implementation of terrainbento. Finally, we illustrate the utility of terrainbento with a benchmark example highlighting the differences in steady-state topography between five different numerical models.

Highlights

  • Computational models of long-term drainage basin and landscape evolution have a wide spectrum of applications in geomorphology, ranging from addressing fundamental questions about how climatic and tectonic processes shape topography, to performing engineering assessments of landform stability and potential for hazardous-waste containment

  • We review the various options that terrainbento offers for alternative treatment of hillslope processes, surface-water hydrology, channel incision, materials, and boundary conditions

  • When the dynamic soil option is used in combination with a sediment-tracking entrainment–deposition erosion law, the Stream Power with Alluvium Conservation and Entrainment (SPACE) numerical model described above is used in place of the simpler entrainment–deposition law

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Summary

Introduction

Computational models of long-term drainage basin and landscape evolution have a wide spectrum of applications in geomorphology, ranging from addressing fundamental questions about how climatic and tectonic processes shape topography, to performing engineering assessments of landform stability and potential for hazardous-waste containment (see, e.g., reviews by Coulthard, 2001; Pazzaglia, 2003; Martin and Church, 2004; Willgoose, 2005; Codilean et al, 2006; Bishop, 2007; Tucker and Hancock, 2010; Willgoose and Hancock, 2011; Pelletier, 2013; Temme et al, 2013; Chen et al, 2014; Valters, 2016). The basic principles of drainage basin evolution are reasonably well understood – such as the fundamental concept that erosion is driven by gravitational and water-runoff processes, the latter of which depend strongly on surface gradient and water flow – uncertainty remains concerning the appropriate forms of the governing transport laws for any particular set of materials and environmental conditions (Dietrich et al, 2003) This situation creates a need for comparative testing in order to gauge the overall performance of various mathematical formulations, to identify knowledge gaps in areas where numerical. Terrainbento takes advantage of Python class inheritance such that all common features of terrainbento model programs (such as input/output, and the handling of boundary conditions) are provided in a generic “ErosionModel” base class from which specific programs are derived This ErosionModel class enables modelers to craft and apply their own implementations without needing to reinvent the overarching software framework or the necessary utility functions. This paper presents and describes terrainbento version 1.0, including its basic structure, mathematical underpinnings, software implementation, and the 28 constituent model programs

General structure of a terrainbento model program
A note on terminology
Basic ingredients and governing equation
Soil-tracking model programs
Multi-lithology model programs
Process formulations
Model domain options
Basic model program
Hillslope processes
Continuity law for soil creep
Linear creep law
Linear depth-dependent creep law
Nonlinear depth-dependent creep law
Soil production
Hydrology
Variable source area hydrology
Stochastic precipitation and runoff
Water erosion
Erosion threshold
Incision depth-dependent erosion threshold
Shear-stress erosion law
Sediment-tracking entrainment–deposition hybrid model program
Entrainment–deposition hybrid model program with fine sediment
Entrainment–deposition model program with bedrock and alluvium
How alternative hydrology formulations influence terrainbento’s erosion laws
Soil and alluvium
Multiple lithologies
Variable climate
Boundary conditions
Base-level handlers
PrecipChanger
Overview
Terrainbento base classes
Basic model interface
Derived classes and use of Landlab components
Model and class naming scheme
Unit tests and model program verification
Conclusions
Support for users and potential developers
BasicDd
BasicSt
BasicSa
B10 BasicCc
B17 BasicDdRt
B20 BasicHySa
B24 BasicStVs
B25 BasicSaVs
B28 BasicChRtTh
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