Tuncer DEMİR

1232

Importance of clast size and shape on selective bedload transport in a coarse-gravel bed river: Trout Beck, England

Bu makale Trout Beck akarsuyunda taşınan çakıl ağırlıklı yatak malzemesinin boyut ve şekil özelliklerinin taşınma üzerindeki etkilerini araştırmak amacıyla gerçekleştirilen arazi çalışmalarına dayanmaktadır. Taşınan yatak malzemesi iki farklı zamanda örneklenmiş olup, yatak yükü malzemesi örneklemesi ise Wolman yöntemi uygulanarak beş ayrı yerde yapılmıştır. Doğal bir akarsu yatağında çakılın boyut ve şekil özeliklerine bağlı olarak oluşan seçici taşınma ve çakılların yatak boyunca dağılımının niceliksel olarak belirlenmesi amacıyla mıknatıslı çakıl deneyleri yapılmıştır. Örneklenen yatak malzemesi ve tutulmuş yatak yükü malzemesinin karşılaştırılması sonucunda anılan yerde çakıl boyutuna bağlı olarak belirgin bir seçici taşınma, buna karşılık çakıl şekli itibariyle kısmi bir seçici taşınma söz konusu olduğu anlaşılmıştır. Tutulmuş malzeme içerisindeki küçük boyuttaki çakılların oranı, yatak malzemesindekine göre daha fazladır. Yatak malzemesiyle karşılaştırıldığında, tutulmuş yatak yükü içerisindeki küresel ve prizma benzeri çakılların oranı daha fazla, buna karşılık çubuk (ovalimsi) ve bıçak benzeri yassı çakılların daha az oranda olduğu belirlenmiştir.Mıknatıslı çakıllarla yapılan deney sonuçları ise, hem çakıl boyutuna hem de çakıl şekline bağlı olarak seçici taşınma örneklerini ortaya koymuştur. Küçük boyut kategorisindeki çakıllar (32-64 mm), akarsu yatağı talveğini takiben en uzak mesafeye taşınmışlardır. Şekil özellikleri itibariyle, hemen bütün ölçüm dönemlerinde, küre şekilli çakıllar hem sayıca fazla hem de taşınma mesafesi açısından büyük değerler göstermiştir. Çubuk ve kısmen prizma şekilli çakıllar da seçici taşınma örneği göstermişlerdir; ancak yassı şekilli çakıllar gerek sayı itibariyle, gerekse taşınma mesafeleri itibariyle oldukça düşük değerler sergilemişlerdir.

İri çakıl yataklı bir akarsu kanalında tane boyut ve şeklinin seçimli yatak yükü taşınmasındaki önemi: Trout Beck Nehri, İngiltere

This paper describes field experiments designed to investigate importance of shape and size of natural clasts in bedload transport in an upland coarse-gravel bed river, the Trout Beck. Transported bedload was trapped twice on different occasion and bed material was sampled at five sections according to the procedure outlined by Wolman. Magnetic tracing experiment was carried out at the same reach to quantify the selective transport of different size and shapes of coarse river gravel and determine their spatial sorting within a natural stream channel. In general, comparison of sampled bed material and trapped bedload showed much stronger size selectivity, and to some extent, shape selectivity. Smal clasts in the trapped bedload were over-represented compared to the residual material. In the trapped bedload sphere and disc-like clasts were over-represented, while blade and rod-like clasts were under-represented. Results of the magnetic tracing experiment also showed evidence of both size and shape selectivity. Preferential movement occurred in the fine clasts (32-64 mm) size classes with tracers located along the channel thalweg moving the greatest distance. In terms of shape, during virtually all survey periods, sphere clasts were transported the greatest distance and greatest in numbers. Rod and, to some extent, discs also moved preferentially but blades moved only short transport distances and less in number.
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Yerbilimleri-Cover
  • ISSN: 1301-2894
  • Başlangıç: 1976
  • Yayıncı: Hacettepe Üniversitesi Yerbilimleri Uygulama ve Araştırma Merkezi
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Importance of clast size and shape on selective bedload transport in a coarse-gravel bed river: Trout Beck, England

Tuncer DEMİR

Catapsydrax, Globorotalia, Globigerinoita' nın (planktik foraminifer) Mut Havzası denizel miyosen istifindeki biyostratigrafisi ve sistematik paleontolojisi

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