گسترش فرسايش خندقي و طبقه بندي آن در حوضه آبخيز رباط ترك دليجان

Investigating factors controlling of gully erosion in Robat Turk basin - Delijan

فرسايش خندقي از جمله زيان­بارترين انواع فرسايش آبي و از فرآيندهاي مهم تخريب خاك به­شمار مي ­آيد كه در بعضي موارد باعث ايجاد كانال­ هايي با طول، عرض و عمق زياد مي­ شود. اين نوع فرسايش يكي از انواع فرسايش آبي است كه موجب تخريب اراضي و بر هم خوردن تعادل در پهنه­ هاي منابع طبيعي و اراضي كشاورزي مي ­شود. در اين پژوهش، به­ منظور شناسايي مهم­ترين عوامل مؤثر در شكل­ گيري خندق ­هاي حوضه آبخيز رباط ترك در شهرستان دليجان از استان مركزي اقدام به جمع­آوري اطلاعات از طريق انجام بازديد­هاي ميداني و اندازه­ گيري ­هاي مورفومتري 10 خندق، نمونه ­برداري خاك از مقاطع هدكت، بخش مياني، دهانه خروجي و حوضه آبخيز هر خندق شد. پارامتر­هايي از جمله اسيديته، هدايت الكتريكي، ماده آلي، كربنات­ كلسيم، رطوبت اشباع، ظرفيت نگهداري،وزن مخصوص و بافت خاك در آزمايشگاه اندازه ­گيري گرديد. جهت تحليل داده ­ها از روش­هاي تحليل خوشه ­اي و تحليل واريانس يك‌طرفه استفاده شد؛ خندق­ها بر اساس ويژگي­ هاي مورفومتري و بر اساس خصوصيات فيزيكي و شيميايي خاك خوشه‌بندي‌شده كه در هر دو مرحله خندق­ها به سه خوشه تقسيم گرديدند. براي شناخت علت قرارگيري خندق­ها در خوشه­ هاي متفاوت از تحليل واريانس يك‌طرفه استفاده‌شده است. نتايج تحليل واريانس نشان مي دهد خوشه هايي كه بر اساس ويژگي­هاي مورفومتري ايجاد شدند، داراي اختلاف معني­داري در ميزان ماده آلي، درصد رطوبت اشباع و رس حوضه آبخيز مي­ باشند و خوشه­ هايي كه بر اساس خصوصيات فيزيكي - شيميايي ايجاد شدند، داراي اختلاف معني­داري در ميزان ماسه، سيلت، ظرفيت نگهداري، رطوبت اشباع و ماده آلي هستند.

Gully erosion is one of the most harmful types of water erosion and of important processes of soil erosion which causes formation of long wide deep canals. The Robat Turk is part of the Shour watershed basin which joins to Qomroud (one of the Panzdahe-Khordad’s Dam basins) and finally to the Salt Lake. The basin’s area is 112.67 km2, located in the longitude of 50⁰46’ to 50⁰52’ of East and the latitude of 33⁰42’ to 33⁰50’ of North. Forty soil samples were taken, dried, milled, sieved by a 2 mm sieve, and analyzed for physical and chemical properties including acidity, electrical conductivity, organic matter, calcium carbonate content, saturated humidity, holding capacity, balk density and the texture of soil. Acidity and electrical conductivity were analyzed after making a 1:1 solution through pH- and EC- meter, respectively. In order to statistically analyze the data, considering the different variables, cluster analysis has been used to allocate the gullies to different groups, acquire the actual groups, and reduce the volume of the data. One-way analysis of variance used to investigate the difference between the groups’ averages, or investigate and determine the existing discrepancies between the morphologically clustered gully groups. The results show that the studied gullies classify to three clusters. Homogenous clusters were found based on the Ward method and the Euclidean distance. In the distances less than 12 (Dlink/Dmax×100) the difference between the morphologically studied gullies are so that they can be classify to three clusters. These clusters were resulted from the variance analysis (ANOVA) based on the difference in depth and in the ratio of the width to the depth of gully’s output. The gullies in the first cluster have the maximum depth and the gullies in the second cluster have the maximum ration of width to depth. Different physical and chemical properties of the soil in the studied gullies are so that they can be clustered in three groups. The gullies with all physical and chemical properties were modeled in three homogenous groups results show that the organic matter of HDKT and the output’s width, saturated moisture and the upstream clay content have a meaningful difference. The comparison of average values of the organic matter of HDKT and output’s width based on the variance analysis has the meaningful difference of F=13.63, P=0.004 and F=5.73, P=0.034, respectively.