Conventional Point-Velocity Records and Surface Velocity Observations for Estimating High Flow Discharge

Flow velocity measurements using point-velocity meters are normally obtained by sampling one, two or three velocity points per vertical profile. During high floods their use is inhibited due to the difficulty of sampling in lower portions of the flow area. Nevertheless, the application of standard methods allows estimation of a parameter, alpha, which depends on the energy slope and the Manning roughness coefficient. During high floods, monitoring of velocity can be accomplished by sampling the maximum velocity, u(max), only, which can be used to estimate the mean flow velocity, u(m), by applying the linear entropy relationship depending on the parameter, M, estimated on the basis of historical observed pairs (u(m), u(max)). In this context, this work attempts to analyze if a correlation between alpha and M holds, so that the monitoring for high flows can be addressed by exploiting information from standard methods. A methodology is proposed to estimate M from alpha, by coupling the historical information derived by standard methods, and new information from the measurement of u(max) surmised at later times. Results from four gauged river sites of different hydraulic and geometric characteristics have shown the robust estimation of M based on alpha.