Extended Abstract



Introduction

Soil erosion is a global risk that seriously threatens water and soil resources, and land changes, especially the destruction and change of forests, are important factors involved in increasing the potential of its occurrence. Therefore, planners and managers must be aware of forest cover changes and their role in causing soil erosion over some time. The evidence shows that with the increase in population and to meet the needs of the residents, the extent of forest lands in the Ghaleroodkhan basin has decreased and the amount of soil erosion has increased. Based on this, the current research seeks to evaluate the effect of changes in forest cover on soil erosion in the Ghaleroodkhan Fuman basin.



Methodology

In this research, to investigate land use changes (especially forest), Landsat satellite images from (OLI-TM) sensors for the years (1992-2023) were obtained from the American Geology website in August. Then, to prepare the images, geometric and atmospheric corrections were made on the images using the Flash method and Envi5.3 software. In the next step, using the object-oriented classification method and the nearest neighbor algorithm by Ecognition software, land use maps were extracted in 1992 and 2023. In the next step, by identifying the effective factors involved in the erosion of the region (including; land use, slope, lithology, soil, distance from the road, distance from the river, and rainfall) and preparing the information layers of each criterion in GIS, valuing and standardizing the layers using Fuzzy membership function and criteria weighting were done using Critique method. Eventually; The final analysis and modeling was done using MABAC multi-criteria analysis method.



Results and Discussion

It can be said that the largest area of use in 1992 is related to forest cover with an area of 222.17 square kilometers, which has decreased to 205.03 square kilometers in 2023. The next land use, which has the largest area in the Ghaleroodkhan basin, is the use of agricultural land. The amount of agricultural area in 1992 was about 161.03 square kilometers, which decreased by about 11 square kilometers in 2023 and reached 150.05 square kilometers. The land use of residential areas has changed the most in the last 30 years, in the starting year (1992) was about 33.01 square kilometers, and in 2023 it reached the area of 60.18 square kilometers.

According to the obtained results, the criteria of slope, land use, and lithology, respectively; In 1992, with weight coefficients of 0.164, 0.154, and 0.145, and in 2023, with weight values of 0.169, 0.158, and 0.142, they received the highest value of weight coefficient in both studied periods. . Also, according to the erosion zoning maps of the studied basin, it can be seen that in 1992, the area of the layer with very high and high erosion potential was 98.92 and 118.19 square kilometers, respectively. in 2023 respectively; 132.39 and 119.94 square kilometers of the basin surface have very high erosion potential.



Conclusion

The results of the study show a decrease in the area of forest cover in the Ghaleroodkhan basin during the study period. So about 1700 hectares of the forest lands of the basin have been reduced and converted to other uses. Mainly, a large area of the forested lands of the basin has been converted into non-forested lands such as agriculture, residential, and pastures, which indicates the not very suitable situation for protecting the region.

It can be acknowledged that according to the trend of land use changes during the studied period, the reduction of forest cover and its conversion to agricultural areas, pastures, and residential lands, as well as encroachment on the privacy and river bed in the form of changes in the use of the river to agriculture and residential. Along with other natural factors of the range, such as; The presence of sensitive and erodible formations, high slope, adequate rainfall, and the abundance of waterways have played the greatest role in increasing the soil erosion potential of the Ghaleroodkhan basin. Due to the severity of destruction in the study area, necessary management measures should be taken as soon as possible to prevent and reduce further damage to the forests of the area, as well as to reduce erosion. Eventually; It should be acknowledged that the use of the land use change map and the erosion risk zoning map obtained in the present study is a practical guide to know the state of forest destruction in the region and the erosion potential of the basin.

Keywords: Soil erosion, land use changes, MABAC, object oriented method, Ghaleroodkhan.