|LI, JUNRAN - New Mexico State University|
|OKIN, GREG - University Of California|
|Herrick, Jeffrey - Jeff|
|BELNAP, JAYNE - Us Geological Survey (USGS)|
|MUNSON, SETH - Us Geological Survey (USGS)|
|MILLER, MARK - Us National Park Service|
Submitted to: Geophysical Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2010
Publication Date: 5/26/2010
Citation: Li, J., Okin, G.S., Herrick, J.E., Belnap, J., Munson, S.M., Miller, M.E. 2010. A simple method to estimate threshold friction velocity of wind erosion in the field. Geophysical Research Letters. 37:Article L10402.
Interpretive Summary: Wind erosion causes land degradation, reduces air quality and causes damage to infrastructure. Predicting wind erosion requires a knowledge of the wind speed, and the wind speed necessary to detach particles from the soil surface, or 'threshold friction velocity' (TFV). The depends on both soil characteristics and distribution of vegetation or other obstructions.While several reliable methods can be used to characterize the spatial pattern of obstructions, there is currently no simple, accurate method for quantifying soil surface effects on TFV. This paper presents the results of tests of an air (BB) gun, pocket penetrometer, torvane, and roughness chain Results were compared with measurements made in a wind tunnel. Wind tunnel measurements are considered to be the most precise, but are impractical for most applications. The results show that TFVs were best predicted using the air gun and penetrometer measurements.
Technical Abstract: Nearly all wind erosion models require the specification of threshold friction velocity (TFV). Yet determining TFV of wind erosion in field conditions is difficult as it depends on both soil characteristics and distribution of vegetation or other roughness elements. While several reliable methods have been established for characterizing the spatial pattern characteristics of roughness elements, there is currently no simple, accurate method for quantifying soil surface effects on TFV. This study provides a physically-based, fast, and easy-to-apply method to estimate TFVs on both bare and protected surfaces. Wind tunnel experiments and a variety of ground measurements including air gun, pocket penetrometer, torvane, and roughness chain were conducted in Moab, Utah and cross-validated in the Mojave Desert, California. Patterns between TFV measured in wind tunnel and ground measurements were examined to identify the optimum method or combined methods for estimating TFV. The results show that TFVs were best predicted using the air gun and penetrometer measurements for crust-free or slightly crusted soils in Moab sites (R2=0.90, P<0.001). This empirical method, however, systematically underestimated TFVs in the Mojave Desert sites when compared to wind tunnel measurements. Further analysis showed that TFVs in the Mojave sites can be satisfactorily estimated with a correction of rock cover (R2=0.83, P<0.01), which is presumably the main cause of the underestimation of TFVs. The proposed method may be also applied to estimate TFVs in environments where other non-erodible elements such as woody debris and postharvest residuals are found.