(بررسي پتانسيل رسوب دهي و فرسايش خاك با روش هيدروفيزيكي و مقايسه آن با روش ژئومورفولوژي مطالعه موردي: حوضه سامان (نوبران، استان مركزي

(The study of sediment and soil erosion using hydro physical model and comparison with geomorphology model (Case study: saman watershed, Nobaran , markazi Province

فرسايش خاك و توليد رسوب از جمله محدوديت هاي اساسي در استفاده از منابع آب و خاك به شمار مي آيد. رسوبات ناشي از فرسايش حوضه هاي آبخيز علاوه بر هدر رفتن خاك و كاهش حاصل خيزي موجب كاهش كيفيت آب مي شود. از اين رو ارزيابي فرايند هاي حاكم بر رفتار آنها به منظور درك بهتر سامانه هاي آبخيز داري و تبيين شيوه هاي مديريتي لازم و ضروري است. حوضه آبخيز سامان با مساحت 156 كيلومتر مربع و متوسط ارتفاع 2540 متر در شمال غرب استان مركزي واقع شده است. در اين تحقيق با استفاده از دو مدل هيدروفيزيكي و ژئومورفولوژي به بررسي پتانسيل رسوب دهي و فرسايش خاك در حوضه سامان پرداخته شده است، هدف اصلي تحقيق حاضر برآورد و تعيين پتانسيل رسوب دهي كل حوضه است. مطالعات بدست آمده در زير حوضه هاي سامان 1، وركبار 1 و چهار حد 2 با احتساب دو شاخص R و R2 نتايج مشابهي بدست آورد ولي در ساير زير حوضه ها نتايج به مقدار كمي تغيير نمود. بعد از محاسبه داده ها بر اساس مدل هيدروفيزيكي، نتايج بدست آمده با روش ژئومورفولوژي مقايسه شد. نتايج بدست آمده با روش هيدروفيزيكي نشان داد كه زير حوضه هريقان 2 با پتانسيل رسوبي 9.724 (با احتساب (R2 در km2 داراي بيشترين پتانسيل رسوبي و ميزان فرسايش و زير حوضه چهار حد 2 با پتانسيل رسوبي 1.147 كمترين شدت فرسايش را دارد. اما در روش ژئومورفولوژي زير حوضه حصار چاي 1 با پتانسيل رسوبي 6/07 بيشترين و زير حوضه هريقان 1 با پتانسيل رسوبي 1/226 كمترين شدت فرسايش را بدست آوردند. در نهايت نتايج بدست آمده در روش هيدروفيزيكي با احتساب R2 نتايج بهتري نسبت به R بدست آورد و مقايسه دو مدل نشان داد كه براي تعيين پتانسيل فرسايش حوضه سامان روش ژئومورفولوژي از روش هيدروفيزيكي مناسب تر است.

Soil erosion and sediment production is including fundamental limitations in the useing of soil and water resources. The sediment yield of watersheds in addition to the loss of soil and soil fertility decline, caused reducing water quality. Therefore, evaluation processes that govern their behavior to better understand and explain the systems Watershed management practices is essential. The aim of this study is to estimate the total sedimentation determine of the basin. Studies obtained in the sub-basin of Saman 1, Vrkbar 1, four level 2 including R and R2 provides the same results in other sub-basins and the results have changed slightly. After calculating the data in tables results were compared with geomorphology. The results obtained by Hydro physical indicated that the basin Hryqan 2 with scaling potential 9.724 (including R2) in km2 highest and sub-basin four level 2 scaling potential 1.147 have been severity of erosion, but the way geomorphology sub-basin fence Tea 1 with producing potential 07 / 6 highest and sub-basin Hryqan 1 with producing potential 226/1147 least erosion was in the case study. The results obtained in the method Hydro physical indicated the index R2 be the better results than the R. comparing the two models showed that for determining erosion potential watershed geomorphology method is more suitable from method of Hydro physical. Key word: hydro physical model, erosion, geomorphology model, sediment, saman watershed. Introduction Nearly 2 billion tons of resource soil is destroyed and massive damage equivalent to 18.5 × 1012 Rails enter the country. Therefore to prevent this damage, it is needed adopt suitable management for preventing erosion and sediment movement. Soil erosion is one form of soil degradation. While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. Excessive (or accelerated) erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases in agricultural productivity and (on natural landscapes) ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses. Water and wind erosion are the two primary causes of land degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significant environmental problems world-wideSoil erosion is a naturally occurring process on all land. The agents of soil erosion are water and wind, each contributing a significant amount of soil loss each year. Soil erosion may be a slow process that continues relatively unnoticed, or it may occur at an alarming rate causing serious loss of topsoil. The loss of soil from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks To archive to the aim the accurate data about the erosion in the watershed is necessary (intended, H. 1389: 18). Since soil erosion can be studied qualitatively and quantitatively, there are many models and more models for evaluation and were not giving much information about the erosion of soil. Specify a successful strategy to prevent erosion and reduce soil erosion depends on the mutual understanding between soil quality and erosion. Material and methods In order to achieve the purpose of the research the case study be studied and identify based on the model of geomorphology and geo physical. In this study, to obtain the production of sediment and soil erosion the geomorphology and hydro physical models be used. In the research, to prepare the database for estimation of sediment and erosion suitable map were produced, the including topography map, slop map, land use map, caver map, the layer database in the environment GIS software corrected and analysis. In the research using hydro physical and geomorphology models was used to estimate erosion and sediment production. Many data were collected by field. Result According to the results of study in Table 11 by Hydro physical model -sub-basin Hryqan 2 with producing potential 9.724 (including R2) highest and sub-basin four level 2 sby producing potential 1.147 least severe erosion was, but in the geomorphology model sub-basin fence Tea 1 by producing potential 07/6 was the highest rate producing erosion and sediment in case study and Hryqan 1 basin with producing potential 226/1147 be least erosion in the case study. The results of table 4 showed then the hydro physic model including R2 have better results than R, because the results obtained with R2 in the geomorphology model showed the closer result. After calculating the data in tables results were compared with geomorphology. The results obtained by Hydro physical indicated that the basin Hryqan 2 with scaling potential 9.724 (including R2) in km2 highest and sub-basin four level 2 scaling potential 1.147 have been severity of erosion, but the way geomorphology sub-basin fence Tea 1 with producing potential 07 / 6 highest and sub-basin Hryqan 1 with producing potential 226/1147 least erosion was in the case study. The results obtained in the method Hydro physical indicated the index R2 be the better results than the R. comparing the two models showed that for determining erosion potential watershed geomorphology method is more suitable from method of Hydro physical.