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Spatial Estimation of Soil Erosion and Sediment Yield in GIS Environment Using SEDD and RUSLE Models: A Case Study Roudzard Watershed in Khuzestan Province
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Shekoufeh Davoudi   , Heidar Ghafari * , Ahmad Farrokhian Firouzi |
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Abstract: (810 Views) |
Introduction
Today, soil erosion is recognized as one of the major contemporary environmental and socio-economic problems. Because it affects agriculture, natural resources, environment and social economy. Although effective measures have been taken in different countries to reverse the adverse effects of soil erosion on a large scale, the rate of soil erosion on a global scale is still very worrying. For example, it has been estimated that approximately 75 billion tons of surface soil are lost annually on a global scale as a result of erosion. The results of studies in Iran also indicate a high rate of soil erosion. The available evidence indicates that the quantity of water erosion in Iran ranges between 1 and 4 billion tons per year. Therefore, efforts to reduce soil erosion should be continued more than before. In this regard, it is very necessary to quantify and identify the spatial distribution of soil and sediment loss areas to provide up-to-date information for policy makers and experts to devise effective strategies for water and soil protection and reduce the adverse consequences of soil erosion.
Materials and Methods
The study area of Rudzard watershed is located in the southwest of Iran and the east of Khuzestan province, which leads to Ramhormoz city in the south and Izeh city in the north. The average annual rainfall of the area is 500 mm, with an annual average discharge of 3.69 cubic meters per second. The region is primarily utilized for forest, pasture, and agricultural activities, which collectively occupy 35%, 30%, and 35% of the total area, respectively. Rainfall data from stations inside and outside the basin during a period of 15 years (2005 to 2019) on a daily basis from the General Directorate of Meteorology of Khuzestan Province and runoff and sediment data from hydrometric stations from the General Organization of Water and Electricity of Khuzestan which was prepared. The data of the 30-meter elevation digital model and Landsat 7 satellite images were obtained from the website of the United States Geological Survey. The satellite images were used to calculate the vegetation factor. Soil science information was also collected through sampling and previous studies. Finally, the amount of erosion was calculated using the RUSLE model. Sediment volume and sediment delivery rate were also estimated using the SEDD model.
Results and Discussion
Rainfall erosivity and topography are the most important factors influencing soil erosion with an average of 10.1 (MJ mm ha-1 h-1 y-1) and 9.3, respectively. The soil erodibility factor varied between 0.023 and 0.034 with an average of 0.028. The vegetation factor also varied between 0.14 and 0.27 with an average of 0.19. Finally, based on these five factors, the annual average of soil erosion in the region was found to be 7.2 tons per hectare per year based on the RUSLE model. The analysis of the results showed that the highest amount of soil erosion was obtained in the forest areas with steep slopes, and the second and third highest amount was obtained in the pasture and agricultural areas, respectively. The reason for the high erosion rate in the forest areas is the slope of more than 50% in these areas. Based on the average of categories method, the average annual sediment production of the whole area was calculated as 210,000 tons per year, which is equivalent to 2.45 tons per hectare per year, considering the area of the area. The average sediment delivery ratio of the basin was estimated to be 34% based on the average erosion and sedimentation. The results of the SEDD model also showed that the sediment delivery ratio in the whole area varied between 0 and 0.99, and its highest value was obtained in the areas adjacent to waterways. Further investigation showed that the highest sediment delivery ratio was associated with forest and pasture land. This is because these two land uses are mainly located in sloping areas. On the other hand, the lowest ratio of sediment delivery was related to agricultural lands due to the low slope.
Conclusion
The results showed that the use of simulator models with small and easily accessible inputs, such as RUSLE and SEDD models, has an acceptable efficiency in estimating the amount of erosion and sedimentation, especially in large areas limited by lack of data. Elevation and slope factors were found to be the most important erosion and sediment transfer factors in this area, such that the highest erosion and sedimentation rates were obtained on forest lands with slopes greater than 50%, and the lowest erosion was associated with agricultural lands with low slopes. Although the use of experimental models such as RUSLE and SEDD to evaluate soil erosion and sedimentation in watersheds is common, the accuracy of the results obtained from them is often due to the lack of real data of erosion and sedimentation in most watersheds of the country. Therefore, it is suggested that the accuracy and validity of the results of the SEDD model as a model with low and accessible inputs in several watersheds, especially representative watersheds that have an appropriate database or through the method such as cesium 137 should be investigated. |
Article number: 1 |
| Keywords: Simulation, Sediment Delivery Ratio, Sediment Rating Curve |
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Full-Text [PDF 2126 kb]
(387 Downloads)
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Type of Study: Research |
Subject:
Special
Received: 2024/01/14 | Accepted: 2024/02/19 | Published: 2024/09/15
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