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You are here : eLibrary : IAHR Asia Pacific Division Proceedings : 19th IAHR APD Congress, Hanoi 2014 : Session 1: ENVIRONMENTAL HYDRAULICS : STUDY ON PICK-UP RATE IN A RIVER UNDER FLOODS BASED ON ACOUSTIC DOPPLER VELOCIMETER MEASUREMENT
STUDY ON PICK-UP RATE IN A RIVER UNDER FLOODS BASED ON ACOUSTIC DOPPLER VELOCIMETER MEASUREMENT
Author : A. SUGIMURA 1, cand Y. NIHEI1
Pick-up rates of bottom sediment in rivers and lakes are important for sediment budget, bed evolution and water-quality environments. A lot of laboratory experiments using open and enclosed channels have been conducted to examine the fundamental property of pick up rates under various flow conidions (e.g., van Rijn, 1984; Otsubo and Muraoka, 1985). In contrast, previous field studies for directly measuring in-situ pick-up rates of bottom sediments were limited.
On the other hand, the authors developed a device which may easily measure an in situ pick-up rate of sediments under various flow conditions (Nihei and Yamasaki, 2005). Using the new device, we clarified pick-up rates of bottom sediments in an urban river before and after flood events. However we can not investigate temporal variations of pick-up rates under flood conditions.
The present study aims to clarify the temporal variations of pick-up rates in a river under flood conditions. For this, an acoustic Doppler velocimeter which can measure three-dimensional velocities and echo intensity closely related to turbidity (e.g., Nakagawa et al., 2012), was applied to measure the pick-up rates in a river. In this study, the field measurements using an ADV were done in the Oohori River which flows into Lake Taganuma, one of well-known eutrophic lakes in Japan. In the measurements, we installed turbidity sensors and ADCP to continuously monitor turbidity and vertical velocity profile, respectively. Using these data, we analysed turbulent quantities such as Reynolds stress and pick-up rates of sediments.
The main conclusions in this study are as follows:
1) The echo intensity measured by the ADV was found to be highly related to the turbidity. It means that the ADV can evaluate easily time series of pick-up rates of sediments.
2) The hysterisis between water level and turbulent quantities under floods was dominant in the flood with relatively higher unsteadiness parameter (Nezu et al., 1997).
3) The correlations between the pick-up rates and bottom shear stress were influenced by API(Antecedent Precipitation Index) and flood magnitude.
File Size : 77,311 bytes
File Type : Microsoft Word Document
Chapter : IAHR Asia Pacific Division Proceedings
Category : 19th IAHR APD Congress, Hanoi 2014
Article : Session 1: ENVIRONMENTAL HYDRAULICS
Date Published : 10/03/2015
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