Akademik Veri Yönetim Sistemi
Yerbilimleri, sa.28, ss.33-47, 2003 (Scopus)
The aim of this study is to investigate the downstream changes in bedload clast size and shape along the Cwm Treweryn stream, Brecon Beacons, South Wales. A total of 21 sites (including six tributary entry points) were used to evaluate downstream changes in bedload size and shape (form, roundness and sphericity) characteristics. At each sites. 100 surface clasts with b axes (intermediate) greater than 32 mm were sampled. Many of the earlier studies found that, due to abrasion and sorting processes, particle size decreases and roundness increases in a downstream direction. However, in contrast to these studies, the Cwm Treweryn stream does not conform this simple downstream pattern, instead shows irregular and complex changes in both size and shape along the channel. In terms of size characteristics, bed material at all 21 sites represented a wide range of size fractions and hence poor sorting. The dominance of disc-shaped clasts with blades the second most frequent shape along the entire channel length is attributed to the structural and lithological characteristics of the predominance of Old Red Sandstone. As a result, comparatively small downstream changes were determined in bedload clast size and shape (roundness, sphericity) and these changes are attributed to the combined effect of different factors, including the lithology of the bedload (Old Red Sandstone), the short river course, and occasional inputs of angular fresh material from the channel banks and bed.