ORIGIN AND CHARACTERISTICS OF RIVER CHANNEL PATTERNS

A theory of the origin of channel patterns is developed and enables predictions of relationships and characteristics which are tested. It is concluded that meanders form where the discharge erodes and transports bank particles with comparable ease whilst braids characterise rivers with highly erodable banks. In both cases, the bank erosion may be induced either by deposition of input sediment (deposition meander or braid) or directly by a discharge with excess energy (erosion meander or braid). Deposition meanders form where the bank material is fine-grained relative to the deposited sediment; deposition braids where the bank material is coarse-grained or where banks are particularly incoherent and fine-grained. Erosion meanders carry a discharge which entrains bank particles in preference to bed particles and transports them downstream; erosion braids carry a discharge which transfers material from bank to bed without downstream movement. Comparisons are made between patterns and the effects of discharge, valley slope, channel material and the quantity and quality of sediment input are explored. The resulting predictions are tested using data from 57 natural rivers. © 1979.