Environmental Erosion Research

fa پهنه‌بندی مناطق مستعد فرسایش خاک با استفاده از روش آنالیز پارامترهای مورفومومتریک اصلاح شده و میزان تولید رسوب (مطالعه موردی: حوضه میانراهان) Zoning of Areas Prone to Soil Erosion Using the Analysis of Modified Morphometric Parameter Method and Sediment Production (Case Study of Mianrahan Basin) مدلسازی و تحلیل زمانی و مکانی رخداد انواع مختلف فرسایش محیطی پژوهشي Research  فرایند فرسایش خاک و تشدید آن بر اثر مدیریت و بهرهبرداری نامناسب، هر ساله خسارتهای زیادی به حوضههای مناطق مختلف ایران وارد میکند. در میان روشهای متعدد مطالعات فرسایش خاک، روش آنالیز پارامترهای مورفومتریک روشی ارزان، سریع و کارآمد برای مطالعه فرسایش خاک است. حوضه نیمهخشک میانراهان به علت رخنمون سازندهای مختلف، تنوع شرایط ژئومورفولوژی، توپوگرافی ناهموار و رونق معیشت کشاورزی و دامپروری همواره در معرض خطر فرسایش خاک قرار دارد؛ بنابراین، پهنهبندی پتانسیل فرسایش خاک این حوضه برای مدیریت علمی و توسعه پایدار آن ضروری است. هدف پژوهش حاضر، پهنهبندی پتانسیل فرسایش خاک در زیرحوضههای حوضه میانراهان است. در این پژوهش، از روشهای WSA و میانگینگیری ـ که مبتنی بر محاسبه و رتبهبندی پارامترهای مورفومتریک است ـ استفاده شد. نتایج نشان داد که بر اساس این دو روش، به ترتیب 49/47% و 53/65% مساحت حوضه میانراهان در پهنههای با پتانسیل فرسایش خاک زیاد قرار دارد و نیازمند اجرای طرحهای حفاظتی است. روش WSA به علت استفاده از پارامترهای مورفومتریک شکلی، خطی و ناهمواری و محاسبه ضریب همبستگی بین آنها، در مطالعات پهنهبندی پتانسیل فرسایش خاک کارایی بهتری دارد. زیرحوضههای جنوبی، شمالی و مرکزی حوضه میانراهان نیز در زمینه فرسایش خاک به ترتیب پتانسیل کم، متوسط و زیاد دارد که میزان این پتانسیل، متأثر از شرایط ناهمواری و شکل زیرحوضهها است و پارامترهای مرتبط با شکل حوضه و ناهمواری حوضه، بیشترین تأثیر را در میزان پتانسیل فرسایش خاک زیرحوضه‌ها دارد.   1- Introduction Soil erosion is the most common type of degradation on the earth's surface, which leads to the separation, displacement and deposition of soil particles (Kogo et al ., 2020). In semi-arid regions, water erosion is the most common type of soil erosion process (Benzouka et al., 2022), which destroys soil fertility and threatens agriculture (Novara et al., 2011). Accelerated type of soil erosion is a global problem due to economic and environmental consequences (Lim et al., 2005), which threatens sustainable development (Maslink et al., 2017). According to the FAO (1984), the average soil erosion in Iran is 4.3 times the global average (30 to 32 tons/hectare/year). The resulting annual damage is estimated at about $ 56 billion (Gholami, 2003). The interstate basin is subject to soil erosion due to the lithological diversity of rugged topography, semi-arid climate and the prevalence of agriculture and animal husbandry. Therefore, evaluation of soil erosion potential and estimation of sediment rate for optimal management and sustainable development in this basin seem necessary. The purpose of this study is to evaluate and rank sub-basins, and interstate basins in terms of erosion prone areas and to estimate their sedimentation based on morphometric examinations. 2- Methodology In this study, the Mianrahan basin area, drainage network and its sub-basins were first extracted and the waterways were ranked based on the Straler method. In this study, two methods of WSA and averaging were used to prioritize soil erosion potential of the Mianrahan basin. The WSA method is based on the ranking and correlation techniques and initially the correlation matrix is obtained between the morphometric parameters. Then the correlation sum (SC) is calculated for each column and the total sum (ST) as the sum of all columns. The weight (W) of each morphometric parameter is calculated by dividing the correlation sum by the total sum (Equation 1). To rank sub-basins, the parameter composition index (CPI) is calculated for each of them (Equation 2). The sub-basins with the highest values of parameter composition index have the highest rank and have the highest soil erosion potential (Cadam et al., 2019). In the second method, the sub-basin priority is determined by the erosion potential based on the initial ranking and then averaging the rankings of each sub-basin (Doss, 2014). Sub-basins with the highest mean rank have the least potential for soil erosion and sub-basins with the lowest mean rank have the highest potential for soil erosion. 3- Results According to the WSA method, sub-basins No. 2, 5, 7 and 13 are in the zone with high erosion potential that cover 47.49% of the area of the interstate basin in total. Sub-basins No. 4, 6, 8 and 12 are located in the zone with medium erosion potential and cover 23.22% of the area of the interstate basin. Sub-basins No. 1, 3 and 11 are located in an area with low erosion potential and include 26.63% of the study area and sub-basins. No. 9 and 10 are located in an area with very low erosion potential and they encompass the corridors with 2.66% of the basin area. Sub-basins No. 1, 3, 7, 9 and 12 have moderate erosion potential and occupy 31.84% of the study basin area. Sub-basins No. 2 and 6 as well as sub-basins 4, 5, 8 and 11 have high and very high soil erosion potential, respectively, and these zones cover 38.54% and 27% of the area of the interstate basin, respectively. 4- Discussion & Conclusions The results of the two models indicate significant overlaps, especially in determining the erosion zones in the southern and northern sub-basins of the interstate basin. However, in the rugged sub-basins in the center of the basin, the two models used have significant differences in the detection of erosion zones. WSA method for zoning soil erosion potential uses correlation between 13 linear morphometric, shape and roughness parameters. But the averaging method uses 7 linear and shape morphometric parameters and simple averaging to zone the soil erosion potential. The averaging method in mountainous basins is not efficient due to the lack of roughness parameters. Therefore, it can be said that the WSA method because of using different morphometric parameters and having accurate calculation has a better performance for zoning studies of soil erosion potential. Finally, it can be said that the amount of soil erosion potential in sub-basins, and intermediate basins is affected by topographic conditions and ruggedness of sub-basins, and the parameters related to basin shape and basin roughness have the greatest impact on soil erosion potential. Sub-basins located in the central areas of the interstate basin have a high potential for soil erosion and demand the implementation of watershed management plans to reduce the soil erosion potential.   پارامترهای مورفومتریک, پهنه‌بندی, حوضه میانراهان, روش WSA, فرسایش خاک. Morphometric parameters, Zoning, Mianrahan basin, WSA Method, Soil erosion. 190 208 http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-663-3&slc_lang=fa&sid=1 mansor parvin منصور پروین mansorparvin@pnu.ac.ir 10031947532846007896 10031947532846007896 Yes Payame Noor University, Iran گروه جغرافیا، دانشگاه پیام نور، ایران