برآورد حجم رسوب ناشي از فرسايش در حوضه ي آبريز رودخانه ي كردشيخ به روش هاي تجربي با استفاده از سامانه ي اطلاعات جغرافيايي

The sediment yield potential estimation of Kordshikh river watershed basin using MPSIAC, EPM and Fournier model in the GIS framework

در اين پژوهش ميزان فرسايش و رسوب زايي حوضه ي آبريز رودخانه ي كردشيخ، با استفاده از مدل هاي تجربي پتانسيل فرسايش، MPSIAC و فورنيه با به كارگيري نرم افزار ايلويس مورد مطالعه قرار گرفت. در روش MPSIAC تاثير و نقش نه عامل مهم و موثر در فرسايش خاك و توليد رسوب (زمين شناسي سطحي، خاك، اقليم، رواناب، توپوگرافي، پوشش زمين، كاربري زمين، وضعيت فرسايش و فرسايش رودخانه اي) در حوضه، ارزيابي و بسته به شدّت و ضعف هر عامل، امتياز يا عددي به آن تعلّق گرفت. از مجموع امتيازات يا اعداد به‌دست آمده براي عوامل مختلف، ميزان رسوب دهي حوضه از رابطه ي Qs=38.77e0.0353R محاسبه گرديد، كه در آن Qs ميزان توليد رسوب و R مجموع امتيازات عوامل نه گانه است. طبق اين رابطه در حوضه ي آبريز رودخانه ي كرد شيخ Qs=533.67(m3/Km2.yr) مي باشد. در مدل پتانسيل فرسايش چهار مشخّصه، شامل ضرايب فرسايش حوضه، كاربري زمين، حساسيت خاك به فرسايش و شيب متوسّط حوضه در شبكه هاي ايجاد شده در نقشه‌ مورد برّرسي قرار گرفت. ميزان رسوب ويژه در حوضه، طبق اين روش GSP=248.94(m3/Km2.yr) محاسبه گرديد. در مدل فورنيه ميزان توليد رسوب با توجّه به روش اوّل محاسبه گرديد و به صورت زير به دست آمد: .

Soil is one of the most important resources in nay country and its degradation causes great losses for human beings, specially in arid and semi- arid regions. One of the existing views in watershed is a kind of management based on the analysis of a set of factors influencing watershed basin as a unit of soil and water resources. Geographical Investigation System (GIS) is used as an efficient means in evaluating and solving of many Problems of natural resources. In this connection, the rate of erosion and sediment yield of Kordshikh river, located in 20 Km west of Qir in Fars province, was studied using experimental models of MPSIAC, EPM and Fournier. In MPSIAC model the effect of nine important factors on soil erosion and sediment yield (surface geology, soil, climate, run off, topography, land cover, land use, present erosion condition and channel erosion) was evaluated and numerical values were assigned to them in terms of intensity and weakness of each factor. Using the sum of those values through equation Qs=38.77e0.0353R, where Qs is specific sediment (m3/ km2. yr) and R is sediment yield score, the rate of sediment yield of the basin was measured. The measured Qs for Kordshikh river was Qs= 533.67. In EPM method four coefficients (basin erosion, land use, soil sensitivity to erosion and basin mean dip) were investigated in constructed network in the map. Specific sediment rate in the basin using this method was Gsp=248.94 (m3/km2.yr). In Fournier model, Qs, the rate of specific sediment, was obtained using his first method (log Qs=2.65 log pw2/pa 0.46 log H (tan S) – 1.56) was Qs=207.91 (m3/km2.yr).