Resistance of soils to concentrated flow erosion: A review

The soil's resistance to concentrated flow erosion is an important factor for predicting rill and (ephemeral) gully erosion rates. While it is often treated as a calibration parameter in process-based soil erosion models, global change studies require the estimation of erosion resistance from measurable soil properties. Several laboratory and field experiments have been conducted to determine the erosion resistance of various types of soils, but no attempts have been made hitherto to summarize all these data and to explore them for general trends. In this study, all available data on the resistance of topsoils to concentrated flow erosion in terms of channel erodibility (Kc) and critical shear stress (tau(cr)) has been collected together with all soil and environmental properties reported in literature to affect the soil erosion resistance. Reported Kc values for cropland topsoils range between 0.002 10(-3) s m(-1) and 250 10(-3) s m(-1) (n=470), whereas tau(cr) values range between 0 and 15 Pa (n=522). It is demonstrated that so far, the heterogeneity of measurement methods, the lack of standardized definitions and the shortcomings of the flow shear stress model hamper the comparability of soil erosion resistance values from different datasets. Nevertheless, combining Kc and tau(cr) data from different datasets, a general soil erosion resistance ranking for different soil textures can be proposed. The compiled dataset also reveals that tillage practices clearly affect Kc (Kc for conventional tillage > Kc for reduced tillage > Kc for no tillage) but not tau(cr). It was concluded that Kc and tau(cr) are not related to each other and that soil and macro-environmental properties affecting the foremost do not necessarily affect the latter as well and vise versa. Often Kc seems to be a more appropriate parameter than tau(cr) to represent the differences in soil erosion resistance under various soil and environmental conditions (e.g. bulk density, moisture content, consolidation, tillage). The two parameters represent different quantities and are therefore both needed to characterize the soil's resistance to concentrated flow erosion. (c) 2006 Elsevier B.V. All rights reserved.