تأثیر پوشش گیاهی صلب بر نرخ انتقال رسوب در سواحل

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی آب، دانشکده کشاورزی، دانشگاه شهرکرد، شهرکرد، ایران

2 گروه سازه‌های آبی، گروه علوم و مهندسی آب، دانشکده کشاورزی دانشگاه شهرکرد، شهرکرد، ایران.

چکیده

بار رسوبی یکی از عوامل مهم و تأثیر­گذار در عملکرد هیدرولیکی و ساختار ریخت­شناسی سواحل تلقی می­شود. یکی از راهکار­های کاهش انتقال رسوب، استفاده از پوشش گیاهی به عنوان یک بیوسیستم جهت به دام انداختن رسوب است. پوشش گیاهی با انسداد جریان، تغییر تلاطم و ایجاد مقاومت بر میزان انتقال رسوب تأثیر می­گذارد. در این پژوهش تأثیر تراکم پوشش گیاهی روی نرخ انتقال رسوب در خط ساحلی بررسی شده است. به­منظور بررسی این اثر مدل ساحل و پوشش گیاهی دریک فلوم لبه چاقویی مجهز به سیستم نیروسنج (لودسل) و دستگاه سرعت سنج صوتی داپلر (ADV) تعبیه شد. آزمایش­ها در دو چیدمان مثلثی و مستطیلی که شامل تراکم 12 تا 273 ساقه در واحد سطح می­باشد، انجام شد. نتایج نشان داد که با افزایش تراکم پوشش و تعداد ردیف­های پوشش، نرخ انتقال رسوب کاهش می­یابد؛ بطوری‏که در بیشترین تراکم نرخ انتقال رسوب تا 80 درصد افزایش داشته و در کمترین تراکم این میزان به 20 درصد رسیده است. همچنین چیدمان مثلثی در بیشترین تراکم 25 درصد و در کمترین تراکم 3 درصد نسبت به چیدمان مستطیلی در کاهش نرخ انتقال رسوب برتری داشته است. با توجه به متغیر های مورد بررسی در این پژوهش تغییرات عدد تراکم بیشترین تاثیر را در نرخ انتقال رسوب دارد، بطوریکه با افزایش تراکم پوشش گیاهی نرخ انتقال رسوب کاهش می­یابد. با استفاده از فرمول­های تجربی نظیر کامفوس، گالوین، سرک و فن در میر به مقایسه نتایج استخراج شده از این آزمایش با مطالعات سایر پژوهشگران پرداخته شد. باتوجه به تحلیل­های آماری انجام شده فرمول سرک اصلاح شده می­تواند مقدار رسوب منتقل شده را با ضریب همبستگی 92 درصد برای حالت با پوشش تخمین بزند.

کلیدواژه‌ها


عنوان مقاله [English]

The Effect of Rigid Vegetation on the Sediment Transport Rate on the Coast

نویسندگان [English]

  • Golnaz Mirzakhani 1
  • Elham GhanbariAdivi 2
  • Roohalla Fattahi 2
1 MSC Graduated, Department of Water Science Engineering, Shahrekord University, Shahrekord, Iran
2 Department of Water Science Engineering, Shahrekord University, Shahrekord, Iran
چکیده [English]

Sedimen load is one of the important factors affecting the hydraulic performance and morphological structure of the beach. One of the solutions to reduce sediment transportation is vegetation as a bio system for sediment trapping. Vegetation due to flow obstruction and turbulence change, affects sediment transport. In this study, the effect of vegetation density on sediment transport rate along the shoreline was investigated. To consider this effect, beach and vegetation models were embedded in a knife edge flume equipped with a load cell and an Acoustic Doppler Velocimeter system (ADV). Experiments were performed in two triangular and rectangular layouts with a density of 12 to 273 stems per unit area. The results showed that by increasing the density of the vegetation and the number of tree rows, the sediment transfer rate decreases; So that in the highest density, the sediment transfer rate has increased up to 80% and in the lowest density this amount has reached 20%. Also, the triangular arrangement at the highest density was 25% and at the lowest density, it was 3% superior to the rectangular arrangement in reducing the sediment transfer rate. According to the variables studied in this investigation, density number changes have the greatest effect on sediment transfer rate, so that sediment transfer rate would decreases by increasing vegetation density. Through experimental formulas such as Kamphuis, Galvin, C.E.R.C and Van Der Meer, the obtained results were compared with the other studies.According to the statistical analyzes performed, the modified C.E.R.C formula would calculate the estimated sediment by a correlation coefficient of 92%.

کلیدواژه‌ها [English]

  • Vegetation؛ Coast؛
  • Sediment
  • ؛ Wave
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