ADCP measured flow current of the middle-lower Changjiang River channel |
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| Authors: | Qiang ZHANG Yafeng SHI Zhongyuan CHEN Tong JIANG |
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| Institution: | (1) Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China;(2) Department of Geography and Resource Management, Institute of Space and Earth Information Science, The Chinese University of Hong Kong, Hong Kong, China;(3) State Key Laboratory for Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, China |
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| Abstract: | The water column flow velocity of 36 river sections in the river reach between Hankou (Wuhan) and Wuxue of the middle-lower
Changjiang River. Their cross sectional distribution patterns in relation to the river channel morphologies were examined
by using ship-mounted ADCP (Acoustic Doppler Current Profiler) instrument. The results indicate four (I-VI) types of river
channel morphology associated flow patterns: I—laterally deepening riverbed topographic pattern; II—symmetrical to asymmetrical
riverbed topographic pattern; III—relative flat riverbed topographic pattern, and IV—sandbar supported riverbed topographic
pattern. All these correspond to the different patterns of flow velocity distribution. The maximum flow velocity is usually
related to the deeper water depth, but irregular water column distribution of flow current velocity results often from the
vortices’ current associated with river knots. Deeper river water depth is usually identified in the river reach located slightly
downstream to the river knot, where faster flow velocity occurs. Downward change in flow velocity fits semi-log law, showing
an exponential decreasing flow current with the maximum flow velocity near the water surface. However, in the river reach
near the river knots, the water column distribution of flow current velocity does not fit the semi-log law, showing the irregular
flow current pattern. This study, in context of river catchment management, highlights the controls of riverbed morphology
to the flow current structure, which will shed light on the post study of Three Gorges damming in 2009. |
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| Keywords: | flow velocity distribution pattern ADCP the middle Changjiang River |
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