A new approach using the Interacting Divided Channel Method (IDCM) for discharge prediction in partly vegetated channels

Predicting flow discharge through vegetated channels is critical to planning and decision-making in river management and restoration as well as in the design and operation of hydraulic structures. An accurate flow discharge estimation in composite channels with mainstreams and vegetated areas remains a very complex issue. In this study, we show how we can predict the total and zonal discharges of partly vegetated channels by adapting the Interacting Divided Channel Method (IDCM), applied with a curved interface approach and with the presence of large-scale roughness elements. The proposed approach was validated by conducting various experiments on a physical model consisting of a very large rectangular channel partly covered by rows of vertical, rigid, circular, and rough steel cylinders representing emergent rigid vegetation. Based on the experimental results as well as data collection from previous studies, the consideration of transverse momentum transfer in terms of apparent shear stress at a curved interface plane has shown improved performance, in predicting flow discharges, with IDCM versus the classical Divided Channel Method (DCM). Furthermore, we have proposed a series of easily applicable expressions to predict the zonal flows of a partly vegetated channel.