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Department of Physical Geography, Faculty of Geography and Planning, University of Isfahan, Iran. , reza.zakerinejad@ui.ac.ir
Abstract: (46 Views)
Extended abstract
1- Introduction
Water erosion is one of the main cause of land degradation and desertification in a large area in arid and semi-arid areas in the world. In Iran in result of poor vegetation and also the high amount of run off, causes the soil loss around 25 billion ton per year. Therefore, evaluation the intensity and amount of soil loss is very necessary for soil and water conservation. Many studies have been conducted in the field of evaluating the amount and intensity of water erosion as well as its risk classes in domestic and foreign studies, including a study that was conducted in the watershed upstream of the Letian Dam, which estimated the annual erosion and sediment production of this basin to be about estimated 20413 tons per year, in recent years’ water erosion has led to a major phenomenon of land degradation and desertification. Water erosion is controlled by climatic features, topography, soil characteristics, vegetation and land management The aim of this research is to investigate the trend and intensity of water erosion during the period (1992-2021) using the ICONA model, remote sensing data and geographic information system (GIS) in the Zohra-Jarhari watershed in southwest of Iran.
3- Methodology
In this research, the evaluation of the risk of water erosion using remote sensing data and the ICONA model in the two time periods of 1992 and 2021 in the Zahreh-Jargi watershed in southwest Iran is discussed. The model used in this research is ICONA erosion model. The ICONA model is a model proposed and developed by the Spanish Institute of Nature Conservation, and it also takes its name from the same institute. This model is a model for estimating the degree of erosion risk in watersheds, based on which the degree of erosion risk can be estimated on a large scale. Figure 2 shows the stages of the ICONA model. In this research, first, the land use map and NDVI index related to 1992 and 2021 were prepared based on TM and ETM+ satellite images. After that, the water erosion risk zoning map of the study area in the mentioned years was prepared based on the ICONA erosion model. By comparing the amount of erosion changes during the past years in the study area, the impact of land use change on the erosion of the area.
3- Results
The risk layer of the used model is created by combining two layers of erodibility and soil protection. Further, according to the tables related to the ICONA model, the two layers of erodibility and soil protection related to the years 1992 and 2021 have been combined with each other (Figure 5). From the comparison of the erodibility risk layers in 1992 and 2021 and according to the diagram in Figure 6, it can be concluded that the extent of 4 erodibility risk classes (low, medium, high and very high) has been increased and the extent of the very low class has been reduced. The main difference between the erosion zones of the studied basin in the studied time period is related to the classes of high erosion risk, which increased by 20.30 in 2021 compared to 1992, and the "very high" erosion risk class, which increased by 6.6 in 2021 compared to 1992. 14% have increased in level, it is worth noting that with the increase in the size of the high and very high risk classes, the size of the very low and low risk classes has also decreased in 2022.
4- Discussion & Conclusions
soil erosion process of the Zahra-Jarhari watershed, one of the large watersheds in the west of Iran, using the ICONA model and remote sensing data and using the geographic information system (GIS) in the two time periods of 1992 and 2021. . Therefore, for this purpose, the input layers to this model were first collected. The final results of the input indicators showed that the layer of high sensitivity areas in terms of the slope layer are located in the west and southwest of the studied watershed, which have a slope of less than 5%, and the high areas of the basin in the eastern parts of the basin and are located north of it, in fact, it can be said that the slope factor is one of the topographical indicators that are very influential on the sensitivity of the basin to soil loss. because with the increase in the slope, the amount of energy and erosive power of the waterway has also increased, which can lead to more harvesting and wastage of soil erosion. In terms of geological index, in the studied basin, the most sensitivity is related to the Quaternary alluvial formations, as well as Fars group formations, such as Mishan, Aghajari and Gachsaran formations. The alluvial formations of the present era are highly sensitive to erosion due to the looseness of the sediments, while limestone formations such as Asmari have a high resistance to soil erosion, and these formations are also a very suitable source of water resources due to the many seams and cracks.
1- Introduction
Water erosion is one of the main cause of land degradation and desertification in a large area in arid and semi-arid areas in the world. In Iran in result of poor vegetation and also the high amount of run off, causes the soil loss around 25 billion ton per year. Therefore, evaluation the intensity and amount of soil loss is very necessary for soil and water conservation. Many studies have been conducted in the field of evaluating the amount and intensity of water erosion as well as its risk classes in domestic and foreign studies, including a study that was conducted in the watershed upstream of the Letian Dam, which estimated the annual erosion and sediment production of this basin to be about estimated 20413 tons per year, in recent years’ water erosion has led to a major phenomenon of land degradation and desertification. Water erosion is controlled by climatic features, topography, soil characteristics, vegetation and land management The aim of this research is to investigate the trend and intensity of water erosion during the period (1992-2021) using the ICONA model, remote sensing data and geographic information system (GIS) in the Zohra-Jarhari watershed in southwest of Iran.
3- Methodology
In this research, the evaluation of the risk of water erosion using remote sensing data and the ICONA model in the two time periods of 1992 and 2021 in the Zahreh-Jargi watershed in southwest Iran is discussed. The model used in this research is ICONA erosion model. The ICONA model is a model proposed and developed by the Spanish Institute of Nature Conservation, and it also takes its name from the same institute. This model is a model for estimating the degree of erosion risk in watersheds, based on which the degree of erosion risk can be estimated on a large scale. Figure 2 shows the stages of the ICONA model. In this research, first, the land use map and NDVI index related to 1992 and 2021 were prepared based on TM and ETM+ satellite images. After that, the water erosion risk zoning map of the study area in the mentioned years was prepared based on the ICONA erosion model. By comparing the amount of erosion changes during the past years in the study area, the impact of land use change on the erosion of the area.
3- Results
The risk layer of the used model is created by combining two layers of erodibility and soil protection. Further, according to the tables related to the ICONA model, the two layers of erodibility and soil protection related to the years 1992 and 2021 have been combined with each other (Figure 5). From the comparison of the erodibility risk layers in 1992 and 2021 and according to the diagram in Figure 6, it can be concluded that the extent of 4 erodibility risk classes (low, medium, high and very high) has been increased and the extent of the very low class has been reduced. The main difference between the erosion zones of the studied basin in the studied time period is related to the classes of high erosion risk, which increased by 20.30 in 2021 compared to 1992, and the "very high" erosion risk class, which increased by 6.6 in 2021 compared to 1992. 14% have increased in level, it is worth noting that with the increase in the size of the high and very high risk classes, the size of the very low and low risk classes has also decreased in 2022.
4- Discussion & Conclusions
soil erosion process of the Zahra-Jarhari watershed, one of the large watersheds in the west of Iran, using the ICONA model and remote sensing data and using the geographic information system (GIS) in the two time periods of 1992 and 2021. . Therefore, for this purpose, the input layers to this model were first collected. The final results of the input indicators showed that the layer of high sensitivity areas in terms of the slope layer are located in the west and southwest of the studied watershed, which have a slope of less than 5%, and the high areas of the basin in the eastern parts of the basin and are located north of it, in fact, it can be said that the slope factor is one of the topographical indicators that are very influential on the sensitivity of the basin to soil loss. because with the increase in the slope, the amount of energy and erosive power of the waterway has also increased, which can lead to more harvesting and wastage of soil erosion. In terms of geological index, in the studied basin, the most sensitivity is related to the Quaternary alluvial formations, as well as Fars group formations, such as Mishan, Aghajari and Gachsaran formations. The alluvial formations of the present era are highly sensitive to erosion due to the looseness of the sediments, while limestone formations such as Asmari have a high resistance to soil erosion, and these formations are also a very suitable source of water resources due to the many seams and cracks.
Received: 2025/05/25
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