Stationary wave trains are commonly interpreted as indicators of critical flow and linked to undular hydraulic jumps (UHJs) in steep rivers, yet the conditions governing their formation and hydraulic significance remain unclear. In this study, controlled flume experiments were conducted to deliberately generate stationary wave trains across a range of slopes and discharges. These experiments enabled detailed measurements of wave geometry, flow depth, and velocity, allowing for systematic analysis of their hydraulic behavior. 

Stationary wave trains were observed in both subcritical and near-critical regimes depending on slope. Comparing different gravity wave celerity equations as well as non-wave-based equations, the intermediate-depth dispersion relationship consistently provided the most accurate estimates of mean flow velocity. The results demonstrate that stationary wave trains are not limited to classical UHJs or strictly critical conditions but instead represent organized surface gravity waves that persist across a range of flow regimes. These findings support wave-based velocity estimation methods and clarify how stationary wave trains can be interpreted in natural river systems.