Comparison of Hydraulic Behavior of Single-Baffled Block Stepped Spillways Between Regular and Irregular Designs

This study evaluated the hydraulic performance of regular and irregular stepped spillways experimentally to reduce the hydraulic leap length and enhance energy dissipation. The study tested fourteen physical models with 40° and 45° slopes and step numbers of 5 and 10, analyzing the effect of a single barrier block and its horizontal position through 98 rectangular flume experiments to evaluate energy dissipation and hydraulic jump length. The results showed that when the nappe flow transitioned to the skimming flow, energy dissipation decreased as discharge increased. Irregular stepped spillways achieved higher energy dissipation than regular ones by about 10–25%, with five-step models outperforming ten-step models due to increased turbulence. A strong positive relationship between discharge and hydraulic jump length was also observed, with jump length increasing by approximately 30–45% at 40° and 45° slopes. Five-degree irregular stepped spillways produced the shortest hydraulic jump lengths, confirming that step irregularity reduces downstream residual energy. Adding a single barrier block improved performance by shortening the hydraulic jump by about 20–35%, especially at higher discharges, with the optimal position at B/2. Overall, an irregular stepped spillway with a barrier block at B/2 was identified as the most effective configuration, enabling shorter hydraulic jumps, smaller stilling basins, and more efficient and economical spillway designs.