Evaluating flood peak attenuation effectiveness of levee management strategies in braided river reaches: a case study of the lower Yellow River

This study focuses on the braided river of the lower Yellow River, analyzing the effects of two artificial levee management schemes-wide levee spacing and narrow levee spacing-on flood peak attenuation and spatial distribution under different return periods (5-year, 10-year, and 100-year floods). The results demonstrate that both schemes significantly reduce flood peak discharges, with the attenuation magnitude increasing as the flood return period becomes longer. The wide levee spacing scheme exhibits superior peak reduction performance under extreme flood conditions, achieving a maximum reduction of 985.6 m³/s and an average reduction of 342.02 m³/s during the 100-year flood event, though accompanied by a water level rise of 0.57-1.14 m. The narrow levee spacing scheme ranks second, with a maximum reduction of 669.51 m³/s and an average reduction of 290.32 m³/s, with water levels rising by 0.66-1.45 m. Spatially, the levee schemes may slightly increase peak discharge at upstream sections (e.g., Daliusi) while achieving significant reductions at downstream sections (e.g., Baocheng). The wide levee spacing scheme is more suitable for addressing high flood risks, particularly in extreme flood scenarios, while the narrow levee spacing scheme is better suited for moderate flood control, balancing peak attenuation and upstream-downstream flow distribution. This study provides a scientific basis for flood control and optimization design in braided river reaches.