Evaluation of models to predict the deflation threshold of wet dune sand

Reliable predictions of wind erosion depend on the accuracy of determining whether erosion occurs or not. Amongst the several factors that govern initiation of soil movement by wind, surface moisture is very significant, Some frequently used models as well as some recent models that predict the threshold shear velocity for particle detachment of wet soils by wind were evaluated, The experiments were conducted in a wind tunnel on prewetted dune sand with moisture contents ranging from 0.003 kg kg(-1)(air dry) to 0.040 kg kg(-1). Sand samples were exposed to different wind speeds for two minutes. Moisture content was determined gravimetrically before and after the experiment, whereas saltation of sand particles was recorded electronically with a saltiphone. Shear velocities were deduced from wind speed profiles, A new concept was developed to determine the threshold shear velocity. Comparison of different empirical and physical-conceptual models showed that there exist large differences between the predicted results. When comparing the predicted shear velocities to the observed values, it was concluded that the differences were substantial, At a moisture content close to -1.5 MPa, the increase relative to the dry threshold shear velocity ranged from 6% to 179%