Considering the interaction of humans and rivers throughout history, further studies of rivers are required for providing a greater quality in human’s life. Rivers are not often direct in its path and tend to be meander. Hence, the curves are commonly forms that are found in rivers. These curves are of two types including “bends” and “meanders”. The former are made by human and the later are made naturally. In this study, geometric and hydraulic parameters of natural curves were measured and then the effects and interactions of these parameters were assessed. Therefore, seven curved reaches in Mazandaran Talar River and its branches were selected and essential parameters (considering facilities) including arch topography, bed grain size and flow rate were measured. Then regarding these data, the geometric and hydraulic parameters of arched reaches were extracted. Next focusing on these data and geometric and hydraulic parameters, the results were obtained which will be discussed further in the main text. According to the results, Leopold and Wolman, Allen, Davidson and Hey equations can be used to predict arches characteristics. To achieve better results, some coefficients were also proposed for these equations. The results of this study demonstrated that the bed grain size of arches is not uniform and in outer arch the particle size diameter is larger than inner arch. Some methods for measuring the shear velocity (based on available facilities) were evaluated and a good correlation was observed between Clauser, parabolic law or the boundary layer characteristics methods. Secondary flow in the arches was also assessed in this study and some of its influential parameters were determined.