How Soil Particle Size Affects Erosion on Gently Sloping Layers

Jenn Hoskins
23rd September, 2025

How Soil Particle Size Affects Erosion on Gently Sloping Layers

Field observations of the Kapo soil slopes reveal a distinctive vertical rhythmic stratigraphy (a) that is highly susceptible to severe erosion forms, including deep gully formation (b, c) and extensive slope cracking (d).

Image adapted from: Liu et al. / CC BY (Source)

Key Findings

  • In Wensu County, China, slopes composed of chalky soil are highly vulnerable to erosion due to rainfall, cracks, and unique geological conditions
  • Slopes with coarse-grained sand resist erosion better than those with fine soil, as water flows through sand more easily, reducing pressure buildup
  • Cracks in the soil act as primary channels for water, accelerating erosion and contributing to slope damage, especially when combined with fine soil composition
Soil erosion poses a significant threat to land productivity and human well-being globally. Arid regions are particularly vulnerable, and understanding the mechanisms driving erosion is crucial for effective prevention and control. Recent research undertaken by a team from Xinjiang University, the Geological Bureau, Xinjiang, and other institutions[1] focuses on the specific challenges presented by the Kapo slopes in Wensu County, Xinjiang, China – areas characterized by chalky, steep formations alongside rivers. The study addresses a key issue: how different soil compositions react to rainfall, and subsequently, how this impacts slope stability. Historically, quantifying soil erosion has been complex, with large-scale assessments often underestimating the role of localized factors like rainfall intensity[2]. This new research aims to provide more specific data to improve preventative measures. The research team used rainfall simulation equipment within an indoor model box to mimic real-world conditions. They tested nearly horizontal laminated soil slopes composed of three different grain sizes – coarse-grained sand, fine soil particles, and a mixture – to observe erosion patterns under varying rainfall amounts. The core finding was that rainfall, the inherent properties of the slope soil, and the presence of cracks are the primary drivers of erosion damage. As rainfall increased, the slopes exhibited a pattern of progressive damage, starting at the base and moving upwards. Slopes with coarse-grained sand demonstrated greater resistance to erosion due to their high permeability, meaning water flowed through the sand more easily, reducing the buildup of pressure and subsequent erosion. Conversely, slopes composed of fine soil particles were far more susceptible, experiencing significant gully erosion. This aligns with the broader understanding that soil texture plays a critical role in erosion susceptibility. Crucially, the study highlighted the importance of cracks in the soil. These cracks acted as dominant seepage channels, channeling water and accelerating the erosion process. This finding builds on earlier work that identified land use/cover change and landscape fragmentation as key influences on soil erosion[2], as these factors often contribute to increased cracking and surface runoff. The expansion of urbanization, for instance, can lead to more impervious surfaces and altered drainage patterns, exacerbating these issues. The research team observed that the anti-erosion ability of some rammed earth structures, such as those found in the Great Wall of Shanhaiguan, is due to the formation of a protective gray-green soil crust[3]. While this study doesn’t focus on rammed earth directly, it does demonstrate the potential for natural soil features to enhance stability. The formation of this crust, and the mechanisms behind it, are areas for further investigation. The findings from contribute to a more nuanced understanding of erosion processes in arid environments. By focusing on specific soil compositions and controlled rainfall conditions, the study provides valuable insights into the interplay between soil properties, crack formation, and erosion damage. This information can be used to inform targeted slope prevention and control strategies, moving beyond broad-scale assessments to address localized vulnerabilities.

AgricultureEnvironmentEcology

References

Main Study

1) Effects of soil particle size on rainfall-induced erosion of near-horizontal layered slopes

Published 22nd September, 2025

https://doi.org/10.1371/journal.pone.0331153

Related Studies

2) Study on soil erosion and its driving factors from the perspective of landscape in Xiushui watershed, China.

https://doi.org/10.1038/s41598-023-35451-7

3) Experimental test and mechanism analysis of soil crust erosion resistance of rammed earth Great Wall in rainy season.

https://doi.org/10.1038/s41598-024-59706-z


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