Fluidized-bed: As an alternative method for rill erodibility modeling

Rill erodibility (Kr), which is a measure of the resistance of soil particles against disintegration in a rill under concentrated flow conditions, is a significant characteristic for rill initiation in a field.  The Process-based WEPP (Water Erosion Prediction Project) originally models Kr by linear excess shear stress (τ), and it is mostly obtained from mini-flume experiments at laboratory conditions. Alternatively, a critical value of flow stress (τ_cr) that points to fragmentation in rills can be modeled by a fluidized bed approach that quantifies the conditions in terms of cohesion (Co) and flow velocity (V_f) by considering the soil as a cohesive material. In there, the water as a fluid applies pressure on solid particle proportional to flow rate of the fluid (v). But, performed related studies on it were mostly tested for the limited soil types. The objectives of this study were to test these relationships and model the rill characteristic for the heavy textures of different soil types and investigate the role of basic soil properties on rill initiation. Experimental results showed that the stronger regression coefficient (R²=0.78) was found between Kr and flow velocity (V_f) monitored at the fluidization stage than that between Co & τ_cr at the studied soil conditions. However, correlations between constant and dynamic soil properties and the measured Kr, τ_cr, Co and V_f values were also quite remarkable (p<0.01) for next-generation modeling studies in terms of rill dynamics. It is believed that the fluidized-bed approach has a great potential to model Kr and encouragingly it is worth to be tested with wider data-sets under different soil-moisture conditions.

Keywords: Rill erodibility, Soil Cohesion, Fluidized bed approach, WEPP