Surface-Average Velocity Conversion Estimation Formula for Small Stream Smart Measurement and Management System

A noncontact measurement method is used for measuring surface velocities as small streams have fast flow velocities and complex channel shapes, making it difficult to measure flow discharges in the event of a flood. These measurement methods convert the surface velocity into average velocity using the surface-average flow velocity conversion coefficient. Existing methods for estimating surface-average flow velocity conversion coefficients assume a flow velocity distribution according to water depth or use a simplified approach based on the roughness of the channel bed, thereby suffering from poor accuracy depending on the hydraulic characteristics of small streams or bed conditions. To solve this problem, we developed a surface-average flow velocity conversion coefficient estimation formula that reflects the hydraulic characteristics of small streams. To develop the conversion coefficient estimation formula, the flow velocity distribution was measured by depth for various flow conditions at a steep artificial river experimental facility, and the conversion coefficient was based on these measurements. The new estimation formula aligned with the results of the measurement conversion coefficient; therefore, it can be applied to a small-stream smart measurement management system, which is expected to enable more accurate discharge measurements. In the future, research will be conducted on the applicability of the developed estimation formula under various small-stream flow conditions.