ارزيابي برخي روش هاي زمين آمار در برآورد سرعت آستانه فرسايش بادي، در دشت سيستان

Assessment of Some Geostatistics Methods for Evaluation of Wind Erosion Threshold Velocity in Sistan Plain

Wind erosion is one of the most important desertification processes in windy regions of Iran such as Sistan region that "120 days" wind dominated it which must be controlled using biological and mechanical approaches. A fundamental parameter in windbreak design is wind erosion threshold velocity trend. The most effective method for threshold velocity measurement is direct measurements in field. Due to heterogeneity in nature, understanding its spatial and temporal distribution is essential. Therefore this study carried out to survey spatial distribution of threshold wind velocity as a main effective factor in wind erosion, to compare different methods on threshold wind velocity interpolation and to provide spatial distribution map of threshold wind velocity. For determination of sampling points a regular grid of sampling on topographic map was drawn and the selected dots in contact of grids for sampling points were considered. Then theirs coordinate systems transferred into GPS system. The wind erosion threshold velocity was measured by erosion meter system directly and carefully. Then kriging, co-kriging and Inverse Distance Weighting methods using Gs+ and GIS softwares were used to determine wind erosion threshold velocity. For comparing these methods, cross validation were used by statistical parameters such as MAE and MBE. The results indicate that best semivariogram model in threshold wind velocity estimation at the study region is spherical model with RSS of 1.6 and correlation coefficient of 0.98 but there was not significant difference between kriging and co-kriging methods and both methods were introduced as suitable methods for interpolating in this region.