Evaluation of Fractal Models in Describing Particle Size Distribution of Sediment (Case of study: Fooladmahale of Semnan)

The objective of current study was to invstigate the accuracy of Tyler and Wheatcraft, Bird et al. and Kravchenko and Zhang fractal models in describing particle size distribution (PSD) of sediment in 14 successive check dams for two depths of 0-15 and 15-30 cm. Sediment PSD were determined in 28 samples using hydrometer method . The referred fractal models were fitted on sediments PSD data. Results indicated that there was no regular relationamong fractal dimensions insuccessive check dams. In addition, sediments transport from surroundingsoils was more observable in check dams. Two-parameter models of Bird et al. and Kravchenko and Zhang presented a better fit compared to one-parameter model of Tyler and Wheatcraft. The results of statistical analysis proved that the sigmoid function was able to describe the relation between fractal dimensions and clay, sand and silt percentage with a greater accuracy compared to the linear sigmoid function. Stepwise regressionanalysisdetermined astrong and significant correlation (R2= 0.97**) between fractal dimensionobtained from Tyler and Wheatcraft modelwithclay and sandcontents. According the result of this study, the determination of sediment PSD is possible bymeasurement of clayandsand amount.