Author(s): Xiaonan Tang; Donald W. Knight
Linked Author(s): Xiaonan Tang, Donald W. Knight
Keywords: Compound channel; Modelling; Overbank flow; Zonal & total discharges -1
Abstract: Two stage channels exist in many natural rivers, and in certain cases mult i-stage channels are deliberately formed in order to increase conveyance capacity in times of floods. To predict the stage-discharge relationship, tradit ional channel division methods are still widely used in pract ice because o f their simplicity. However it is well-known that these methods either under-est imate or over-estimate the channel discharge. More recent ly a so-called ‘weighted divided channel method’ (WDCM) has been proposed by Lambert & Myers (1998) that can improve the estimat ion of both zonal discharge and the overall discharge. The values o f weight ing factor ( (cid: 93) ) recommended for use in the WDCM for the Flood Channel Facility (FCF) data with smooth floodplains and rough floodplains are 0. 5 and 0. 2 respectively. Atabay & Knight (2006) show that the weight ing factor ( (cid: 93) ) is not well established, varying with both channel shape and roughness distribut ion, besides not being physically based. Despite this, the WDCM is a promising approach that is simple to apply. In this paper, a mod ified WDCM method is presented that gives better predictions for homogeneously roughened channels. In addit ion, a new method, named the ‘horizontal single method’ (HSM) is recommended, based on empirical formulae, that gives good estimates of both zonal and total discharge for homogeneously and heterogeneously roughened compound channels.
Year: 2007