ارزیابی اثر طرح آبخیزداری حوضة آبخیز کن بر میزان فرسایش و رسوب

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد آبخیزداری، دانشکدة منابع طبیعی دانشگاه تهران

2 استاد دانشکدة منابع طبیعی دانشگاه تهران

3 استادیار دانشگاه آزاد اسلامی، واحد گرمسار

4 استادیار دانشکدة منابع طبیعی دانشگاه تهران

چکیده

در ایران به‏ دلیل فقدان سابقة طولانی در اجرای طرح‏های حفاظت خاک و آبخیزداری، این اقدامات به صورت کمّی ارزیابی نشده و روش‏های مشخصی بدین منظور ارائه نشده است. در این تحقیق تلاش شده است اثر عملیاتِ آبخیزداریِ اجراشده در سال 1379 در حوضة آبخیز‏ کن بر میزان فرسایش و رسوب بررسی و موفقیت یا شکست طرح و علل آن روشن شود. بدین منظور، پس از تهیة آمار و اطلاعات مورد نیاز، متوسط بار معلق در دورة قبل (1347 ـ 1379) و بعد از اجرای طرح (1380 ـ 1387) با روش منحنی سنجة رسوب به طریق روش حد وسط دسته‏ها محاسبه شد. همچنین، فرسایش و رسوب‌دهی حوضه با استفاده از مدل MPSIAC محاسبه شد و نقشة فرسایش و رسوب‌دهی ویژه برای دورة بعد از اجرای عملیات با استفاده از نرم‏افزار Arc Map تهیه شد و در نهایت، دربارة میزان کارایی و تأثیر این عملیات بر میزان فرسایش و رسوب‌دهی حوضه داوری شد. نتایج مطالعات نشان داد که بر اثر اجرای این طرح، متوسط بار معلق از 47892 تن در سال در طول دورة آماری قبل از اجرای طرح به 22365 تن در سال در طول دورة آماری هشت‌ساله بعد از اجرای طرح و فرسایش و رسوب‌دهی از 66758 تن به 50549 تن رسیده است؛ این امر حاکی از اثر مثبت طرح بر کاهش میزان بار معلق و عدم ایفای نقش مؤثر در کاهش میزان فرسایش بوده است؛ به‏گونه‏ای که میزان فرسایش در سطح حوضه تغییر چشمگیری نداشته است. دلایل عمدة کارایی پایین طرح بر کاهش میزان فرسایش عبارت‌اند از: عدم اجرای عملیات بیولوژیک مناسب در سطح حوضه (اجرای کمتر از 25 درصد از حجم عملیات پیشنهادشده)؛ تمرکز عملیات بر اجرای عملیات مکانیکی؛ ضعف در نظارت و ارزیابی پروژه در طی همة مراحل اجرای آن؛ رعایت‌نکردن استانداردها و نکات فنی مانند منطبق‌نبودنِ مکان سازه‏های ساخته‌‏شده و مکان‏های پیشنهادشده؛ رعایت‌نکردنِ استانداردهای لازم در ساخت سازه‏ها و نامناسب‌بودن ابعاد سازه‏ها؛ و تخریب کف بند در سازه‏های سنگی ملاتی.
 

کلیدواژه‌ها


عنوان مقاله [English]

Evaluation of Watershed Plan on the rate of erosion and sediment in Kan basin

نویسندگان [English]

  • golaleh ghaffari 1
  • Hassan Ahmadi 2
  • Omid Bahmani 3
  • Ali akbar Nazari samani 4
1 M.s. student of watershed management, Natural Resources Faculty, University of Tehran.
2 - Professor of Natural Resources Faculty, University of Tehran.
3 Assistant Professor, Islamic Azad University, Garmsar Branch.
4 - Assistant Professor of Natural Resources Faculty, University of Tehran
چکیده [English]

In Iran due to the lack of long experience in the implementation of Soil Conservation and Watershed Management Plans, these measures have not been evaluated quantitatively and specific methods for this purpose have not been provided. In this research effort is to investigate the effect of watershed management operations performed in Can Basin in 1379, on the amount of erosion and sedimentation and rate of project success or failure and its causes. So after providing the required information and statistics and being sure about the authenticity and accuracy of statistics and statistical reconstruction of defects with conventional methods, to investigate the effect of implemented projects on erosion and sedimentation rates, average of suspended sediments in the period before project implementation (1986-2000) and in the period after project implementation (2001-2008) was calculated using sediment rating curves through intermediate technique class, and using daily water discharge, watershed erosion and deposition were also calculated using MPSIAC model. Specific erosion and deposition map was provided in the period after project implementation using Arc GIS software and finally the amount of efficiency and effect of this operation on the amount of erosion and deposition rates was judged. The results of studies showed that due to operating this plan, the average amount of suspended sediment has changed from 47892 tons per year during the statistical period before the plan to 22365 tons per year during the eight-year statistical period after it. The amount of erosion and sedimentation has shifted from 66758 tons to 50549 tons, which shows the positive effect of plan on reducing the amount of suspended sediment and the lack of effective role in reducing the rate of erosion. The main reasons for the low efficiency of Watershed Management Plan implemented in relation to decreasing the amount of erosion are: lack of suitable biological operations in the basin (less than 25 percent of the volume of the proposed action), focusing on mechanical operations, weaknesses in project monitoring and evaluation During all stages of its implementation, failure to observe the standards and technical points such as non-conforming structures built between locations and proposed locations, lack of standards in building the necessary structures and inappropriate dimensions of structures, destruction of floor section in mortar stone structures and etc.
 

 

کلیدواژه‌ها [English]

  • watershed management plans
  • erosion and deposition
  • Suspended Sediment
  • GIS

 

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