Investigation of sand mining potential from the Qarechai river bed

In this study, the sedimentation process in QareChai River (located in Markazi province) and the possibility of sand mining and construction activities in the margin and floodplain areas was evaluated. To do this, by simulating the river flow, the rate of erosion and sedimentation was simulated in a length of 29.8 km near the Khondab city. After preparing the required and basic information and data related to bed materials and sediment gradations, the river sediment flux and distributions along the river were investigated using the HEC-RAS model. After calibrating the model, Wilcock sediment transport formula was selected as the most appropriate equation for estimating sediment discharge with an error of 6% in comparison with the values ​​measured at the hydrometric station. Accordingly, the amount of bed changes in the level of each river section, the amount of sediment and the changes in the longitudinal profile of the river over a 10-year period were simulated. The results showed that during 10 years, there was an average of 13 cm of erosion. The average erosion in the intervals of 6 km from upstream to downstream is 18, 21, 14.8 and 3.2 cm, respectively. Therefore, it is impossible to extract river bed materials in this period. In addition, the creation of a hole with a length of 6 km, a wide of 50 m, and depths of 20 and 50 cm from the deepest point of the river at a distance of 6 km downstream showed that these holes will remain constant after 10 years and will not return to their original conditions before mining. Therefore, when the erosion rate reached its minimum value, it will be possible to extract sediment at a distance of 6 km downstream.