A method for establishing the critical threshold for aeolian transport in the field

Abstract

A basic feature of any wind-eroding surface is its threshold -the wind speed at which sediment transport is initiated. A new method was developed and tested that allows for the rapid determination of threshold under natural wind conditions in the field. A mathematical expression that relates saltation activity and relative wind strength was reformulated so that threshold may be calculated from measurements of saltation activity and the mean and standard deviation of wind speed. To test the new method and determine its usefulness, a field experiment was performed within a region of low-relief dunes on the Southern High Plains of West Texas. The experimental system consisted of a 2-m meteorological tower and a piezoelectric saltation sensor. It was found that during periods of active aeolian activity, threshold values could be calculated every 5 minutes. This new method allows for routine monitoring of surface threshold conditions in the field. Example threshold calculations are presented and they demonstrate that the method works well. Published in 2004 by John Wiley & Sons, Ltd.

Diurnal variations of saltation activity at Tazhong: the hinterland of Taklimakan Desert

“…Following Stout (2004), the critical threshold wind velocity was computed using the following equation:…”

“…When c = 1, it indicates continuous occurrence of saltation during observation; when c = 0, there is no saltation activity occurring; U -1 is the inverse of normal distribution function of c. Critical threshold was determined at 5-min intervals for saltation activity values between 0.02 and 0.98 (Stout 2004). Figure 3 shows the diurnal distribution of saltation seconds of all days.…”

“…In this study, the critical thresholds of four seasons are calculated with the method following Stout (2004). During all seasons (Fig.…”

Threshold wind velocity as an index of soil susceptibility to wind erosion under variable climatic conditions

“…The threshold wind velocity is variable and can be affected by soil surface conditions (soil moisture, vegetal cover and roughness) as well as by climatic factors (precipitation, temperature, evapotranspiration and relative humidity) (Stout, 2003(Stout, , 2004. Some authors found a larger influence of soil water contents and some atmospheric variables such as air humidity (Ravi et al, 2004(Ravi et al, , 2006 and air temperature on the threshold wind velocity (Gregory and Darwish, 1989;McKenna-Neuman, 2003).…”

“…The wind tunnel provides a controlled environment that allows a careful and systematic study of the threshold conditions (Stout and Zobeck, 1996;Stout, 2004), but it does not reflect exactly the field conditions. Furthermore, wind tunnel experiments have been used to test numerous empirical and theoretical models that express threshold velocity as a function of soil moisture (Bagnold, 1941;McKenna-Neuman and Nickling, 1989;Fecan et al, 1999;Cornelis et al, 2004).…”