Deriving Optimal Analysis Method for Road Surface Runoff with Change in Basin Geometry and Grate Inlet Installation

Road surface-runoffs have been analyzed using various approaches, but inaccurate analysis methods lead to overestimation of the drainage capacity, causing unexpected flood damage in low-lying urban areas. Previous studies have highlighted the importance of considering various parameters for accurate road surface-runoff analysis. This study involves road surface-runoff analysis using an enhanced approach considering simplified and modified drainage basin geometries, road surface and gutter flow travel times, and inlet interception efficiency as key parameters under various road conditions. The topographical road conditions were set as follows: Width (6 m), longitudinal slope of road (2-10%), road surface slope (2%), and transverse slope of gutter (2-7%). The results show that using a modified basin considering road slope conditions for estimating actual flow path length and travel time is better for flow analysis than the simplified rectangular basin. Additionally, the runoff analysis should consider the roadside inlet installation conditions, given that the bypass discharge (i.e., rainfall runoff that is not intercepted by upstream inlets) flows downstream and affects the downstream flow characteristics. Based on these results, an optimal road surface-runoff analysis method was developed, which is expected to be useful for road design.