Estimation of sedimentation and erosion potentials of Ruin River catchment using hydrophysical model (CSY)

Today, soil erosion is considered one of the most important problems in the world, and due to the long period of soil formation in Iran, the importance of this problem is more prominent in this country. This annual process causes the destruction of land, the reduction of soil fertility and the filling of reservoirs of dams. The best place for erosion control is catchment areas. It is necessary to pay attention to watersheds in the process of erosion, especially the basins whose rivers play an important role in providing drinking water for residential areas, agriculture and river treatment projects. In this research, using hydrophysical models (CSY), the sedimentation potential of the sub-basins of the Ruain River catchment area in the southern slopes of Aladagh Mountains in northeastern Iran was calculated. The results of this research showed that factors such as size, topography, erodibility, precipitation and vegetation cover in the sub-basins of this river basin have the greatest effect on the sedimentation potential of the sub-basins of this river, and the erosion and sedimentation potential is the same in all the sub-basins of this river. is not. Based on this, the sedimentation potential for Ruin sub-basin was 390.05 tons equivalent to 47.84%, for Mahmoudi sub-basin 182.04 tons equivalent to 22.32%, for Kalat sub-basin 143.91 tons equivalent to 17.65% and for Shiravieh sub-basin 99.27 equivalent to 12.17%. Therefore, the Ruin and Mahmoudi sub-basins are more sensitive to erosion processes than the other two sub-basins and should be properly managed by implementing soil protection plans and proper management of the erosion process.

Erosion is the movement of soil from one place to another and in any possible way, the natural process of this process is necessary for nature, but a large amount of it will lead to unfortunate consequences such as the filling of lakes and dams, the reduction of soil fertility, the increase of the sediment load of rivers and the destruction of ecosystems. had Erosion occurs under the influence of various factors, and knowledge of these factors will have a significant effect on reducing erosion and sediment load of rivers. Today, the increase of sediment measuring stations in river catchment areas has made it easy to measure their sediment load, and most of the world's rivers are equipped with these stations, with all the possible improvements in this field, some catchment areas still lack this device. In addition, these stations cannot predict the amount of erosion in the future, and it is not possible to install measuring devices for all basins and their sub-basins, so estimating the amount of erosion and sedimentation of the watershed using the model Experimental studies can be considered as a suitable program to protect the soil and prevent the harmful effects of erosion and help to obtain reliable data in the stations.

Due to the high rate of erosion and the slowness of soil formation, the study of this process gained more speed. With the presentation of the cycle of erosion by Morris Davis in 1884, the process of erosion attracted the attention of more researchers (Shahdad, 2009). With the passage of time and the increase of agricultural activities, erosion became more intense and the need for scientific studies in this field increased and became academic and many experimental methods such as USLE, MPSIAC, WEPP, EPM, SWAT, MUSLE, geomorphology, Hydrophysics, Musgrave and... were presented and researchers such as Gavrilovich (1988), Weiss Kamir and Smith (1978), Musgrave (1947), Gab Hart and Johnson (1982) (1982), Zonta in Italy and... in this field conducted studies (Maqami Moghim et al. 1402). In Iran, due to the long time of formation, the high rate of soil erosion and the lack of equipment and hydrometric stations, experimental methods of estimating sedimentation and erosion have attracted the attention of researchers, and researchers such as Mahmoud Abadi (1384), Naderi (1389), Khosravi 1390), Qadzavi (1391), Ahmadi (1396) and Haghi Abhi (1398). Conducted studies in this field. One of the new methods of experimental estimation of erosion among the methods proposed in Iran that has attracted the attention of Iranian researchers is The hydrophysical method is CSY, which has been used by researchers in Iran due to its ease. In a study conducted in the Nozhian watershed in Lorestan province, a jury concluded that the hydrophysical model is more accurate compared to the EPM and MPSIAC models. (Davari et al., 2014). In another study in the Kesilian basin of Mazandaran, compared to the geomorphological method, the results of the hydrophysical method had a greater distance with the statistics recorded at the hydrometric station of this basin (Mohsani et al., 2015). Damghan River used this method to estimate erosion potentials and considered it a suitable method to estimate sediment in a relative manner in this basin (Maqami Moghim et al., 1402). With this method, it is possible to identify the erodible points of the basin more easily, as a result, planning for high-risk points is done with more precision (Ahmadi, 2016). Ruin River is one of the watersheds of the southern slopes of Aladagh highlands in the northeast of Iran, which has received less attention from researchers. . The abundant accumulation of sediment in the alluvial cone of this river indicates severe erosion in its catchment area (Figure 1). Despite severe erosion, its sedimentation and erosion potential has not been studied. The only information related to the sediment measurement of this river is its hydrometric station, which is located in the southwest of Iraqi village which records the sedimentation of this river in general. For this reason, the information about the erosion potential in the sub-basins of this river is still unknown. This can cause many problems for the people living in this area, especially the industrial complex in the south of this basin as the largest industrial complex in northeastern Iran. For this reason, it is necessary to calculate its sedimentation potential for the principled exploitation of natural resources and reducing the harm of erosion.