Author(s): Mohammad Givehchi; Mahmoud F. Maghrebi; Kiyosi Kawanisi
Linked Author(s): Kiyoshi Kawanishi
Keywords: Isovel contours; Reverse flow; Discharge estimation; Tidal river
Abstract: In tidal rivers with comparatively large width, estimation of the instantaneous discharge is a formidable task. In order to estimate the discharge a large number of measured velocity points are needed, each point should be collected in a reasonable time interval. The flow characteristics in a tidal river with partially reverse flow are much more complicated. Maghrebi has previously introduced a model for the production of isovel contours in a normalized form, which can be used for estimation of discharge in artificial and natural channels. It is assumed that the velocity at each arbitrary point in the flow section is affected by the hydraulic characteristics of the boundary. In the present study, for the first time, the model is applied to a tidal river with partially reverse flow, which is caused by opening a sluice gate located asymmetrically close to the right bank of the Ohta floodway in Hiroshima, Japan. An acoustic Doppler current profiler (aDcp) was used to measure the velocity profiles at different verticals. Then, the actual discharge in the river is estimated as the summation of the product of point velocity multiplied by the representative area over the whole section. In addition, the estimated discharge based on each measured point and the predicted isovels of flow cross section is obtained. The results show that the corresponding errors for the measured points away from the solid boundaries and the boundary of flow between the two opposite directions along a vertical, which are associated with lower absolute values of isovels, are reasonable.
Year: 2007