Landslide-generated impulse waves are among the major geological disasters in the Three Gorges Reservoir area of China, affecting both the main stream and the tributaries within its range. While river bifurcation has an enormous impact on the propagation attenuation of landslide-generated impulse waves, the bifurcation propagation mechanism differs from that of flood flows. In this study, the common Y-shaped river channel structure in a reservoir area was generalized and 18 groups of physical experiments on wave bifurcation in such river channels were carried out. The hydrodynamic characteristics of the landslide-generated impulse waves during the bifurcation process, across deflection angles of 0° to 150°, were revealed using the particle image velocimetry (PIV) flow field. The experimental results indicated that the impulse waves during the bifurcation process could be categorized into three stages: the dispersion stage without lateral constraints, the collision and reflection stage within the bifurcated river channel, and the oscillation propagation stage. In the experiment, the sudden lateral propagation of impulse waves at the bifurcation point resembled the dam-break wave phenomenon. Based on this observation, leading to the formation of a calculation method for the far-field bifurcation prediction of landslide-generated impulse waves in Y-shaped river channels. Based on the experimental results, the proposed calculation method was verified and corrected. After calibration against the experimental data, the prediction error was reduced from a range of -44.8% to -19.0% to a narrower range of -20.6% to +18.9%. Finally, we proposed two propagation modes unique to wave bifurcation, namely one-side half-limited and one-side unlimited propagation. The findings can be directly applied to assess impulse waves generated by landslides in other complex river networks worldwide, allowing more accurate assessment of geological disasters in reservoirs. This research also provides a more accurate and comprehensive basis for relevant disaster prevention and emergency responsive strategies.
 

landslide-generated impulse waves,Y-shaped river channel,bifurcation propagation of impulse waves,bifurcation mode,amplitude prediction