Author(s): Martin J. Marriott
Linked Author(s):
Keywords: Divided channel method; Meandering compound channel; Bends; Separation; Flooding
Abstract: Experimental work using physical laboratory models of idealised meandering compound channels is presented. The aspect of the work described in this paper is the effect that the overbank flow has on the conveyance of the inbank zone. It is shown for an arrangement with tight bends, which resulted in significant flow separation when flowing at or below bankfull, that the addition of overbank flow mobilised the conveyance of the inbank zone, and resulted in an increased conveyance from this zone. In contrast, for less sharp bends, where separation did not occur, the overbank flow acted to reduce the conveyance of the inbank zone, in line with recently derived prediction methods. Some limits of applicability of such methods are thereby demonstrated, and comparisons are made with the experimental results. The results are relevant to the prediction of flood levels from fluvial systems, particularly where meanders may be reintroduced as a programme of river restoration. Plots are included of velocity vectors obtained by physical measurement, and such information is considered useful for comparison with numerical modelling using computational methods. NOTATION A 1 Cross sectional area in zone 1 B Bankfull width Q 1 Flow in zone 1 Q 1 ´Zone 1 adjustment factor (see Equation 4) Q bf Bankfull flow r Radius of the main channel centreline y 2 Depth of flow in zone 2 y´ Overbank depth relative to bankfull depth (see Equation 3) m, K, cempirical coefficients from James and Wark (1992)
Year: 1999