ABSTRACT This graphical abstract shows how flow-division imbalance emerges in a tidal river network under climate stress and engineering intervention. Drivers such as tides, reduced discharge, sea-level rise, and hydraulic structures alter boundary conditions and enhance tidal backwater effects at bifurcations, leading to asymmetric flow distribution. The main channel becomes dominant (90% flow) with increased velocity and erosion, while secondary channels weaken (10% flow) and undergo sedimentation. This shift is reflected by an increase in the Flow Division Index (FDI) from 0.7 to 0.9. The figure highlights that local interventions cannot restore balance, and that effective management requires adaptive, network-scale approaches. Flow division at river junctions strongly influences flood routing, channel stability, and network resilience in tidal systems, yet it is often treated as a fixed parameter in management. This study investigates flow-division behaviour in the strongly tidal, highly branched Sai Gon–Dong Nai river system under combined climate stress and engineering intervention. A calibrated one-dimensional hydrodynamic network model is applied as a diagnostic tool to analyse discharge partitioning, water levels, and flow velocities across 19 zones during 2014–2023. Results demonstrate that flow-division imbalance is persistent and structurally embedded at the network scale. Main channels convey 75–95% of total discharge under baseline conditions, increasing to 90% under climate stress, with associated water-level rises of 0.07–0.16 m and velocity increases of 5–10%. Engineering interventions reduce peak water levels by approximately 20–30% but do not restore balanced connectivity, particularly in secondary branches subject to strong backwater control. Under combined forcing, intervention effectiveness is non-additive, with climate forcing offsetting much of the hydraulic benefit. These findings reveal a decoupling between flood mitigation and flow redistribution, highlighting flow division as a distinct operational objective for managing climate-stressed tidal river networks.
Chung et al. (Wed,) studied this question.