Comparison of different mass transport calculation methods for wind erosion quantification purposes

Abstract

Quantitative estimation of the material transported by the wind under fi eld conditions is essential for the study and control of wind erosion. A critical step of this calculation is the integration of the curve that relates the variation of the amount of the material carried by the wind with height. Several mathematical procedures have been proposed for this calculation, but results are scarce and controversial. One objective of this study was to assess the effi ciency of three mathematical models (a rational, an exponential, and a simplifi ed Gaussian function) for the calculation of the mass transport, as compared to the linear spline interpolation. Another objective of this study was to compare the mass transport calculated from fi eld measurements obtained from a minimum of three discrete sampling heights with measurements of nine sampling heights. With this purpose, wind erosion was measured under low surface roughness conditions on an Entic Haplustoll during 25 events. The rational function was found to be mathematically limited for the estimation of wind eroded sediment mass fl ux. The simplifi ed Gaussian model did not fi t to the vertical mass fl ux profi le data. Linear spline interpolation generally produced higher mass transport estimates than the exponential equation, and it proved to be a very fl exible and robust method. Using different sampling arrangements and different mass fl ux models can produce differences of more than 45% in mass transport estimates, even under similar fi eld conditions. Under the conditions of this study, at least three points between the soil surface and 1·5 m high, including one point as closest as possible to the surface, should be sampled in order to obtain accurate mass transport estimates. Additionally, the linear spline interpolation and the non-linear regression using an exponential model, proved to be mathematically reliable methods for calculating the mass transport.

Field wind erosion measurements with Big Spring Number Eight (BSNE) and Modified Wilson and Cook (MWAC) samplers

“…(2) was used as a reference for comparisons with other equations. This result is according to the results obtained by Panebianco et al (2010) who found that the exponential equation is a very flexible and robust method to estimate the HMT in a loam sandy soil of the semiarid pampas.…”

“…(5), probably because the integration heights were different in each study: Buschiazzo and Zobeck (2005) integrated from the soil surface compared from 12.5 cm in this study. In a loamy-sand soil of the semiarid Pampas the use of different sampling arrangements and different mass flux models has produced differences of more than 45% in mass transport estimates, even under similar field conditions (Panebianco et al, 2010). HMT calculated with different equations correlated significantly (p b 0.01 Table 5) but the slope of the regression equation was not 1.…”

“…(1), (2), (3) and (4) respectively) which fit a HMF variation as a function of height, between 12.5 and 150 cm height. The integrations were made between 12.5 and 150 cm height, because little changes in the lower boundary for the vertical integration have different effects on the amount of material calculated with each equation (Funk et al, 2004;Panebianco et al, 2010). Table 1 Grain-size distribution and mean grain-diameter of each soil.…”

“…Buschiazzo and Zobeck (2005) carried out field measurements with the BSNE samplers and found that the HMT calculated with a potential equation is from 40% to 55% lower than those calculated with the rational equation (Stout and Zobeck, 1996). The use of different sampling arrangements and different mass flux models can produce differences of more than 45% in mass transport estimates, even under similar field conditions (Panebianco et al, 2010).…”

Dynamics of volcanic ash remobilisation by wind through the Patagonian steppe after the eruption of Cordón Caulle, 2011

“…Considering the BSNE efficiency3233 range and the limitations of the methodology34 discussed in the methods section, the values presented here could be underestimated by up to around 50%, especially at the plane and the convex areas. However, the main reason for the underestimation in that case was due to the fact that the distribution of the mass flux across height was exponential, which is not the case in most of the datasets observed herein, especially during the periods of greater mass fluxes (Fig.…”