Morphology of riffle–pool sequences in the River Severn, England

摘要: Despite the occurrence of pool-riffle sequences in many rivers there are few data concerning unit morphology. Of criteria proposed to identify units, only two methods can be regarded as objective and robust. These â��zero-crossingâ�� â��control-pointâ�� methods. In this paper statistics developed from method describe streamwise morphology 275 riffles 285 pools which form a near-continuous 32.1km bed River Severn Shropshire, England. Yalinâ��s theoretical relationship between pool:riffle length (i�¬p) channel width (W): i�¬p = 3W applies Severn. Reach-average riffle height (H) is constant proportion bankfull depth (h); typically H i�� 0.16h. Riffle positive function length. Pool pool However both increase more rapidly than bed-level amplitude; such that long or relatively â��flatâ��. As gradient reduces, bedforms flatten become asymmetric stoss sides proximal slope lengthen at expense lee distal slopes. The statistical relationships height, water similar those for equilibrium subaqueous dunes. partially consistent with analysis relating bedform (Lr) i.e. Lr i�i2i�°h wherein i�i 1 steep near-equilibrium but 2 3 relative decreases long-low features. A consideration turbulence indicates frequency coherent turbulent-flow structures associated riffle-pool mixing order 60 seconds. morphological dynamic similarity dunes raises intriguing questions respect self-similar, convergent organization periodic alluvial classification particularly.