بررسي كمي توليد رسوب و تعيين عوامل مؤثر بر آن در حوضه آبريز كمه-سميرم

Quantitative Assessment of Sediment Yield an‎d Determination of Influencing Factors in the Komeh-Semirom Watershed

جغرافياي طبيعي

The Komeh watershed, located in the southern part of Isfahan Province, due to its geomorphological an‎d climatic characteristics—including steep slopes, weak marl–shale lithology, shallow soils, an‎d intense convective rainfall events—is considered one of the areas with very high erosion an‎d sediment yield potential in the Central Zagros region. The absence of an active sediment gauging station within the watershed makes the application of integrated an‎d indirect approaches essential for the quantitative estimation of sediment yield. In this study, sediment production an‎d erosion status in the Komeh watershed were assessed by integrating data from the Marbar reference basin, transferring specific discharge an‎d runoff coefficients, hydrological analyses, empirical an‎d semi-empirical models (USLE, PSIAC, an‎d EPM), remote sensing techniques, an‎d spatial processing within a GIS environment. Initially, the annual runoff of 17 sub-watersheds was estimated using the Justin method, which was identified as the most accurate approach based on statistical performance criteria. Subsequently, by employing the sediment rating curve of the Sarbaz hydrometric station, the suspended sediment load an‎d total sediment yield of the reference basin were calculated an‎d then transferred to the Komeh watershed. The results indicated that the annual sediment production of the watershed ranges between 1.8 an‎d 2.5 million tons per year, while the specific sediment yield was estimated to be 1,200–1,500 tons per square kilometer per year. According to global sediment yield classifications, these values indicate a condition of very severe sediment production. Spatial analysis of the PSIAC an‎d EPM models revealed that approximately 50% of the watershed area falls within the “high” an‎d “very high” erosion risk classes. The southern an‎d southwestern sectors of the watershed exhibit the highest erosion susceptibility, primarily due to slopes exceeding 20%, weak marl–clay soils, high drainage density, an‎d poor vegetation cover. The results of multiple regression analysis demonstrated that slope (β = 0.58), soil type (β = 0.37), an‎d lan‎d use (β = 0.31) are the most influential factors contributing to increased erosion, whereas vegetation cover (β = −0.44) plays a fundamental role in reducing erosion intensity. The spatial overlap among the applied models an‎d their consistency with statistical results confirm the reliability an‎d robustness of the integrated methodological framework adopted in this study. Based on the erosion zoning maps, the southern parts of the watershed were identified as critical areas, requiring urgent management interventions, including gully an‎d channel stabilization, terracing, grazing control, an‎d vegetation restoration. The findings of this research provide a scientific basis for integrated watershed management planning, sediment control, an‎d soil conservation strategies in the southern region of Isfahan Province.

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