T. Moramarco and C. Saltalippi (Italy)
streamflow measurements, stage, velocity profile, discharge.
A simple model to estimate the cross-sectional mean flow velocity from the velocity points collected also during high flood is proposed. The approach assumes a parabolic trend of the mean and maximum velocity sampled along each vertical, in the flow area. The trend is derivable by three simple constraints. The accuracy of the method is compared to that of some approaches based on the two dimensional velocity distribution derived by Chiu [1]. The velocity data set sampled during eight flood events at three equipped sites along the upper Tiber river in Central Italy, are used as benchmark. The lower percentage error values in estimating the mean flow velocity showed its greater reliability also for high flood when the velocity points are collected only in the upper portion of the flow area. Moreover, the method provided satisfactory results also for new equipped river site, where the velocity data sample is too limited to estimate an accurate value of the entropic parameter, M, of Chiu's velocity distribution. Finally, because of its simplicity, the method is found very useful in the practical engineering, allowing both to short remarkably the time of the velocity measurements sampling and to estimate quickly the discharge.
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