SEDIMENTARY PROCESSES/Fluvial Geomorphology 657 Figure Channel and floodplain styles (A) The braided course of the Upper Waimakariri River, New Zealand; (B) the Rangitata River at Peel Forest, New Zealand, showing vegetated islands and braid bars; (C) the meandering River Tywi, Wales, UK, showing gravel point bars and water filled cut off channels being filled by fine grained flood sediment; (D) the anastomosing Columbia River, British Columbia, Canada, showing channels, levees with trees, and backswamps (a recent avulsion has created a new disorganized channel in the background) bar-filled channels (the bars being submerged and migrating at high flows, with scour holes where flow threads join, and deposition at zones of flow divergence) and the latter vary in sinuosity, symmetry, and migration pattern (Figure 7B) Illustrations of four channel-style prototypes are shown in Figure A similar kind of approach may be taken with architectural ensembles as a whole Table shows the order and suborder classification of floodplains The classes are broadly based on energy and sediment size, with subdivision according to factors such as confinement in relatively narrow valleys and the presence of particular sedimentation styles The observed styles have specified ranges of stream power and grain size, but these may overlap or leave gaps on a stream power/grain size plot (Figure 9) The same also applies to data for rivers designated as braided, meandering, and straight This is probably because factors other than bankfull power and bed material size are important Such factors include bank strength (related also to vegetation), the role of overbank flows in bank breaching (as in cut-offs, crevasse formation, and avulsion), and the rate of supply of finer sediment It is not easy to produce a set of simple process/environment criteria to underpin a qualitative subdivision of ensemble or floodplain types Such discrimination has been noted, however, on gradient/discharge plots for channel types (Figure 10) Drainage Basins Despite local complexities, drainage basins as a whole exhibit general trends in controlling factors from source to mouth (or with increasing drainage area) and therefore in fluvial styles These are illustrated schematically in Figure 11A, though it should be appreciated that individual catchments may be complex as a result of factors such as lithological