“…For complex case studies such as the natural rivers with large transverse velocity shear, the dispersion coefficient estimation is time-consuming with a high level of uncertainties [10,16]. According to the previous studies, the flow depth (H), section width (B), mean flow velocity (U), bed shear velocity (U*), river shape parameter (b), channel sinuosity (s) in river sections and the combinations of them (e.g., the flow discharge, Q) are the most influential parameters for determination of the Kx [17,18,19,20,21]. Based on these hydraulic and hydrodynamic parameters, several researches were carried out to develop a formula for estimation of the Kx based on the following representation For this purpose, several methods including empirical/mathematical based equations [22,23,24,25], statistical and regression-based equations [14,17,26,27] and in recent years different models of soft computing such as adaptive neuro fuzzy inference system (ANFIS), support vector machine (SVM), Gene expression programming (GEP) and ANN [3,6,9,11,12,28,29,30,31] were used to predict and develop a formula that can be used in the estimation of Kx in natural rivers.…”