A Simple Model of the Variability of Soil Depths

Geochem Geophys Geosyst

Egli

et al. 2019

Self Cite

The importance of gradual erosion relative to landsliding depends predominantly on the slope angle. One factor of critical influence in landsliding along with slope angle and slope shape is the soil depth. Understanding soil depth development on steep topography is fundamental for understanding and predicting the occurrence of landsliding at threshold landscapes. We develop a model to predict soil depth that addresses both threshold and gradual processes. If erosion is a gradual process, soil depth increases until the soil production rate no longer exceeds the erosion rate, and steady state is reached. The predicted soil depth (x) is proportional to the ratio of the infiltration to the erosion rate. Identifying a predictive result for erosion as a function of slope angle (S) allows a test of both the erosion and soil production models with field observations. The same theoretical approach to soil production should be applicable when the principal erosion process is shallow landsliding. After landslides, soil recovery initially follows our predicted power law increase in time, though with increasing time background erosion processes become important. At a time equal to a landslide recurrence interval, the soil depth can exceed the steady state depth by as much as a factor 2. By comparing predicted and observed x(S) results, we show that the accessed result for erosion as a function of slope angle is accurate. Soils deeper than the depth predicted at the landslide recurrence interval are beyond the stability limit. This result suggests an important practical relevance of the new soil production function.

“…Further, it is in accord with a century of the theory of soil development (Yu et al, 2017), from Dokuchaev (1948) onward (translation 1948, original from 1883).…”

Section: Introductionmentioning

confidence: 62%

Section: Percolation Modelmentioning

confidence: 99%

Section: Percolation Modelmentioning

confidence: 99%

Section: Geochemistry Geophysics Geosystemsmentioning

confidence: 99%

Section: Other Sgm Parametersmentioning

confidence: 99%

See 3 more Smart Citations

Comparison and Contrast in Soil Depth Evolution for Steady State and Stochastic Erosion Processes: Possible Implications for Landslide Prediction

Geochem Geophys Geosyst

Egli

et al. 2019

Self Cite

Flow, Transport, and Reaction in Porous Media: Percolation Scaling, Critical‐Path Analysis, and Effective Medium Approximation

Sahimi

2017

Reviews of Geophysics

141

We describe the most important developments in the application of three theoretical tools to modeling of the morphology of porous media and flow and transport processes in them. One tool is percolation theory. Although it was over 40 years ago that the possibility of using percolation theory to describe flow and transport processes in porous media was first raised, new models and concepts, as well as new variants of the original percolation model are still being developed for various applications to flow phenomena in porous media. The other two approaches, closely related to percolation theory, are the critical‐path analysis, which is applicable when porous media are highly heterogeneous, and the effective medium approximation—poor man's percolation—that provide a simple and, under certain conditions, quantitatively correct description of transport in porous media in which percolation‐type disorder is relevant. Applications to topics in geosciences include predictions of the hydraulic conductivity and air permeability, solute and gas diffusion that are particularly important in ecohydrological applications and land‐surface interactions, and multiphase flow in porous media, as well as non‐Gaussian solute transport, and flow morphologies associated with imbibition into unsaturated fractures. We describe new applications of percolation theory of solute transport to chemical weathering and soil formation, geomorphology, and elemental cycling through the terrestrial Earth surface. Wherever quantitatively accurate predictions of such quantities are relevant, so are the techniques presented here. Whenever possible, the theoretical predictions are compared with the relevant experimental data. In practically all the cases, the agreement between the theoretical predictions and the data is excellent. Also discussed are possible future directions in the application of such concepts to many other phenomena in geosciences.

Where Are We and Where Are We Going? Pedogenesis Through Chemical Weathering, Hydrologic Fluxes, and Bioturbation

Hydrogeology, Chemical Weathering, and Soil Formation

Egli

Faybishenko

2021

Self Cite

A review of the status of fundamental research into soil genesis and development is given, together with a discussion of the outstanding problems from various perspectives, such as the geological, hydrological, and soil ecological points of view. The urgency of understanding what soil is, how it forms and evolves, relates fundamentally to its connection with the cycling of water and those elements of deep significance to biology, e.g. carbon, nitrogen, and phosphorus, as well as to the uptake and fate of the (mostly) solar energy input. The coupling is inherent in the close relationships between soil genesis and the formative process of chemical weathering, together with its abiotic drawdown of atmospheric carbon, as well as the relationship between soil evolution and the biological processes that change the soil. Each of these phases links soils to the atmospheric carbon composition and the Earth's climate system. More recently, the link between soil formation and Earth's water cycle has become clearer with the recognition that field weathering rates are more likely flux-limited (water, organic acids, and reaction products) than kinetics-limited. While a link between water and CO2 drawdown appears explicit in the photosynthetic reaction, the relationship between plant productivity and transpiration fundamentally links water and cycling of elements such as carbon, nitrogen, and phosphorus. The summary is intended to place the works of the present book into the context of present research efforts and future goals.