A review on hydraulics characteristics of stepped gabion weir

Gabion weir is hydraulically efficient and ecologically compatible structure widely used for energy dissipation and flood moderation. This review critically examines the hydraulic performance of stepped gabion weirs over the past three decades, including flow regimes, discharge characteristics, water surface profiles, energy dissipation, air–water interaction, and scour behaviour. Existing studies indicate that gabion weirs provide improved energy dissipation and reduced scour compared to solid stepped weirs due to the combined effects of overflow and through-flow. However, limitations remain regarding scale effects in physical modelling, limited replication of field conditions, progressive clogging of the porous matrix in longer time, absence of generalised equation for predicting energy dissipation and maximum scour depth, insufficient validation of experiment and numerical model for higher steps number. The review identifies future research directions including improving understanding in transition from nappe to skimming flow, physical and numerical modelling to reduce scale effect, analysing application of end sill and its transverse and longitudinal arrangement for hydraulic performance, and understanding complex behaviour of interaction between through flow and overflow. It also identifies area of application of machine learning for further research. A consolidated set of parameters from existing studies are also provided in this paper that will help for future research.