Is “soil anti-scourability” a rational methodology for assessing soil erosion resistance? Insights from a case study and a concise discussion

Abstract

The soil erosion resistance (SER) is a critical property of soils with respect to their ability to resist the erosive force exerted by the overland flow. Various flume-based methodologies were utilized to investigate that property and abundant datasets of SER had been established. Meanwhile, a unique methodology for the assessment of SER, the “anti-scourability methodology” (ASM), proposed by Chinese researchers had been widely used across China for more than 60 years and rich data had been obtained. In recent years, several reports using the ASM had appeared in international journals in English, which implied a potential spread of the methodology outside China in the future. However, the ASM had some intrinsic drawbacks that would impede its worldwide application, although it is a simple and practical methodology. This paper discussed the connection between the ASM and the commonly adopted “detachability methodology” (DTM), and compared their performances in the assessment of SER based on a case study on the Loess Plateau using a modified desk-top scouring flume. The results showed that the ASM and DTM are both under the flume-based methodology framework and the index values of ASM could be transformed into the soil detachment rate values. However, as a methodology in the “pre-model-era”, the ASM could only give researchers an overall picture of SER under different soil management conditions, rather than mechanistic understandings of soil detachment process compared to the DTM. The small-sized flumes typically used in the ASM might not distinguish the differences of SER between sufficiently revegetated land use types due to the low level of hydraulic design. Nevertheless, the ASM could be a useful tool for the long-term monitoring of SER across large landscapes because of its low costs and simplicity. To enhance this simple and practical approach, the upper limit of flow discharge of flumes should be no less than that used in the DTM researches (e.g., no less than 25 m² h⁻¹ in most researches), therefore to obtain scouring forces strong enough to distinguish the SER across a broad range of soil types and management conditions. This is the first study that clarified the nature of ASM as an empirical simple tool for the assessment of SER and proposed its potential application outside China. Meanwhile, we suggested that the existing data of soil anti-scourability indices should be synthesized for further study.