The Impact of Sand and Gravel Mining on River Bedload Amount and Gradation (Case Study: Zaremrood River, Mazandaran Province)

Sand and gravel mining from the rivers bed in the country has been increased in the recent years which causes changes in the rivers systems. Irregular excavation of sand and gravel regardless of the river sedimentation capacity causes changes in river sediment balance and morphology. In this study to investigate the impacts of the sand and gravel mining on the bedload amount and gradation in Zaremrood river, the bedload was sampled by placing pit sampler in the river bed. Granulometric analysis of sediment was carried out for each sample separately using ASTM method. Their weights were measured in the laboratory, too. Then, the sizes of diameters D10, D50, D90, mean grain size and the values of sorting, skewness and kurtosis were obtained in micron and Φ scale using GRADISTAT software. Finally, a significant difference between the sediment statistics of the upstream and downstream cross sections of sand and gravel mining in SPSS22 software was investigated. The results showed that the sizes of diameters D10, D50, D90, and mean grain size, sorting showed a significant difference in the bedload samples of the upstream and downstream cross section of the mining place. However, skewness and kurtosis of bedload sediment particles size did not show significant difference in the mentioned samples. Also, sand and gravel mining from river bed in the study reach caused the bed erosion, dislocation of sedimentary layers and changes in the sediment balance.