Developing Relations Between Soil Erodibilty Factors in Two Different Soil Erosion Prediction Models (USLE/RUSLE AND WEPP) and Fluidized Bed Technique for Mechanical Soil Cohesion.

Soil erosion models are valuable analysis tools that scientists and engineers use to examine observed data sets and predict the effects of possible future soil loss. In the area of water erosion, a variety of modeling technologies are available, ranging from solely qualitative models, to merely quantitative equations. The main purposes of this study performed in USDA-National Soil Erosion Research Laboratory (NSERL) can be summarized as developing soil erodibility equations in the defined models by obtaining new data set under rainfall experiments and intending to fill a gap between the USLE/RUSLE-based erosion prediction technology and the process-based WEPP model which is partitioned depending upon the water erosion process (splash (detachment), interrill and rill erosion processes).  In this context, soil erodibility potentials of two different soil samples were collected from the State of Washington and qualified under simulation conditions and the relationships between process-based erodibility parameters such as interrill and rill erodibility and critical shear stress and the empirically based USLE/RUSLE-K term were investigated. Rainfall simulations were performed in NSERL lab under a sequence of rainfall intensities: 50 mm h^-1 for one hour, 25 mm h^-1 for 20 minutes, 75 mm h^-1 for 10 minutes, and 100 mm h^-1 for 10 minutes to obtain erosion data sets with 4 different intensities.  This data was used to derive interrill erodibility (K_i). A mini-flume with a gradually increasing flow rate conditions was used in order to derive rill erodibility (K_r) and critical shear stress (τ_c). And, Fluidized Bed Technique, proposed new approach for measuring mechanical soil cohesion in laboratory conditions was performed to obtain newly relationships between models and technique.

Key words: soil erodibility, interill erodibility, rill erodibility, critical shear stress, fluidized bed technique, USLE/RUSLE, WEPP