Document Type : Research Article
Authors
1
Professor in Geomorphology, Department of Physical Geography, Tabriz University, Tabriz Iran
2
Associate Professor in Geomorphology, Department of Physical Geography, Tabriz University, Tabriz, Iran
3
Ph.D in Geomorphology,Department of Physical Geography, Tabriz University, Tabriz, Iran
Abstract
Soil erosion is one of the most important problems that has affected human life in recent years. The type and intensity of soil erosion in a region depend on climatic conditions, altitude, soil, and land use. Meanwhile, the importance of land use is greater than other factors due to the effective role of humans in influencing it. In this research, to estimate the amount of erosion and sedimentation in the Zimkan watershed, we used two methods, MPSIAC and EPM, each of which evaluates nine factors (geology, soil, climate, water flow, elevation, vegetation, land use, landform, and river erosion) and four factors (erosion, land use, soil sensitivity, and the average slope of the basin), respectively. Then, ArcGIS software and Sentinel-2 satellite sensor images were used in the ENVI 5.3 environment to prepare the related layers. The results showed that the erosion values in the MPSIAC and EPM models were 5,142.9 and 6,401.2 tons per year, respectively, and the amounts of sediment were 2,461.25 and 3,624.72 tons per year, respectively. The erosion class and severity of the basin's erodibility, in terms of soil loss, are in critical condition. The highest intensity of erosion and sediment production was observed in the outlet sections of the basin. It is necessary to implement management and protection policies at the watershed level. It was also found that the results of the MPSIAC method are closer to the actual observations in the basin than those of the EPM method.
Extended Abstract
Introduction
The amount of erosion in a watershed can be determined if there are sufficient records of discharge and sediment data by applying statistical methods. However, in many basins across the country, there are no measurements of soil erosion and sediment production, which requires the use of experimental methods to estimate soil erosion. To estimate the amount of sediment and erosion in a region, there are many methods, including the modified global equation of soil erosion. This model is a suitable method for calculating soil losses because the results show no significant difference from those measured in the region.
Material and Methods
The Zimkan or Zamkan river basin is located in the north of Dalaho city and the west of Kermanshah province. The drainage pattern of this basin is rectangular with an area of 2,324 square kilometers and flows from the southeast to the northwest. This basin is bounded from the west by the Piran basin and from the north by the Posht Teng basin and the Lima river basin. The basin is located at the geographical coordinates of 46°4'30" to 46°11'8" east longitude and 34°35'44" to 34°22'56" north latitude. The research was conducted using two models for comparison, and the methodologies of these two models and their outputs are introduced below.
EPM Model
Introduced in 1988 by Gavrilovic at the international conference on river regimes for estimating the amount of erosion and sedimentation, this model was applied after 40 years of research on erosion plots in Yugoslavia. This model estimates reliable and acceptable results of the erosion rate with four main factors. The factors of this model are mentioned in the table, and after scoring and processing the data with the help of ARC/GIS software, they were calculated.
MPSIAC Model
The PSIAC method was presented in 1968 by the Water Management Committee in the United States for calculating the intensity of soil erosion and sediment production in arid and semi-arid areas. This method was modified in 1982. In Iran, this model was implemented for the first time in 1973 in the Dez Dam watershed, and it evaluates nine factors to calculate erosion and sediment production. Each of these factors has been examined from both quantitative and qualitative perspectives, with five qualitative grades and quantitative scores ranging from -10 to +25.
Results and Discussion
This research was conducted with the aim of estimating the erosion and sedimentation of the study area using EPM and MPSIAC models and comparing the results with actual measurements. To present the results, the final layers were classified and information was extracted from them. By preparing the required maps from the layers of the previous stage and analyzing the obtained information layers, appropriate outputs were prepared.
Conclusion
The difference between the calculated values of the annual sediment amounts by the MPSIAC method is small. This is in contrast to the EPM model, where this difference is large, demonstrating the accuracy of the MPSIAC model in estimating the amount of sediment.
Additionally, the low erosion class covers the largest area of the basin, accounting for about 58% of the total area, while the high and medium erosion classes cover nearly the same area. This nevertheless indicates that the study area is predominantly affected by erosion. Finally, the specific and annual sediment yields of the Zimkan catchment calculated by the EPM and MPSIAC models show that the sediment delivery ratio and specific erosion estimates in this basin differ significantly between the two models. Based on this, the EPM model produced higher estimates for both parameters. Therefore, it can be concluded that the MPSIAC model is more reliable, as its outputs are closer to reality.
Keywords
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