ABSTRACT Quantifying the effect of vegetation distribution patterns on the mean velocity of overland flows is critical for understanding soil erosion. However, the effects on flow velocity of changing row spacing or column spacing individually, as well as predictive models for these configurations, remain understudied. This study conducted indoor experiments with five vegetation column and row spacing levels (0.01–0.09 m), eight flow discharges (0.3–1.0 L/s), and three slope angles (15°–45°). The results showed that the contributions of environmental factors to the velocity followed the order of flow discharge, slope angle, row spacing ratio, and column spacing ratio, and these factors exhibited strong interactive effects. Under the tested conditions, the flow regime was transitional, and the flow was supercritical. Flow velocity followed a power‐law relationship with the Reynolds number. A new predictive model for the velocity incorporating column spacing ratio, row spacing ratio, hydraulic gradient, and Reynolds number was developed. This model demonstrated superior predictive accuracy (with 75% of R 2 values exceeding 0.800) and reliability over two representative prediction models selected from the literature, making it particularly suitable for predicting the velocity on vegetated slopes with spacing configurations similar to those tested. However, since the flow regime in this study was transitional and supercritical flow, caution is required when extrapolating the results of this study to other flow regimes. The results provide a basis to inform the design of optimised vegetation layouts and improve the accuracy of soil erosion predictions on vegetated slopes.
Liu et al. (2026) studied this question.