AUTOMATIC MEASUREMENTS OF STREAM FLOW USING FLUVIAL ACOUSTIC TOMOGRAPHY SYSTEM Kiyosi KAWANISI, Arata, KANEKO Noriaki GOHDA and Shinya

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1 AUTOMATIC MEASUREMENTS OF STREAM FLOW USING FLUVIAL ACOUSTIC TOMOGRAPHY SYSTEM Kiyosi KAWANISI, Arata, KANEKO Noriaki GOHDA and Shinya NIGO Discharges of a tidal river and a gravel-bed river were measured using an innovative technology called Fluvial Acoustic Tomography (FAT). Reciprocal sound transmission was performed between two acoustic stations located on both sides of rivers. The FAT system makes a breakthrough with the following aspects: (a) accurate time with GPS clock signals, (b) high signal-to-noise ratio with 10th order M-sequence modulation, (c) deducing cross-sectional average velocity from multi-paths that cover the cross-section, (d) low power consumption, small and lightweight. Even for a tidal river with periodic intrusion of salt wedge, the river discharges of the FAT system were in good agreement with the discharges observed by an array of ADCPs. The discharge measurement by the FAT system was carried out successfully even in flood events with high suspended sediment concentration and large ambient noise levels of sound. The discharge of the FAT system also agreed well with the results of the ADCPs and the float observations during the flood events. Key Words: acoustic velocitimeter, acoustic tomography, discharge, saltwater intrusion, tidal estuary, gravel-bed river H-Q ADCP 1) H-ADCP 2) 3,4) 5) 1 ADCP 6) ADCP PIV 7) H-ADCP 4,8) H-ADCP 9) 10) (FAT) 11 13) FAT

2 -1-2 (FAT) FAT M GPS GPS 10 M SN GPS 2 ITC

3 図-3 太田川放水路祇園地点における測定概要図-4 太田川放水路河口部における測定概要

-5 ITC3422 30 khz T227 25 khz ±20 % T227 25 khz 30 khz 2km 30 khz (1) -2 9km 3 0.

4 -5 ITC khz T khz ±20 % T khz 30 khz 2km 30 khz (1) -2 9km m 1:9 120m 3m -3 ITC FAT T227 (2) FAT FAT m H-Q 40 mm 115 m 0.8 m T227 Hyperion G3, 4000mAh, 14.8V (1) FAT

5 -6 (a) (b) (c) (d) ADCP H-Q FAT ADCP -7-6(b)-(d) 3 30 cm (c) (d) ADCP FAT ADCP FAT ) -7 FAT ADCP (b) 10 Medwin 14) -8(c) -8(d) FAT

6 -8 (a) (b) (c) (d) (2) :00-18:00-9 FAT H-Q FAT SN

7 FAT 10 5% -10 Medwin 14) FAT 0.25 FAT FAT M GPS (FAT) FAT FAT (FAT) FAT FAT ( 31 ) ( ) ( ) 1),, : ADCP,, Vol. 52, pp , ),,, : H-ADCP,, Vol. 11, pp , ),, :,, Vol. 50, pp , ) : H-ADCP, B, Vol. 63(4), pp , ) Chiu,C.L.,Hsu,S.M.andTung,N.C.:Efficient methods of discharge measurements in rivers and streams based on the probability concept, Hydrological Processes, Vol. 19, pp , ),,, : ADCP,, Vol. 52, pp , ),,,,,,,,,, :,, Vol. 45(2), pp , ) Sloat, J. V. and Gain, W. S.: Application of acoustic velocity meters for gaging discharge of three lowvelocity tidal streams in the St. John River Basin, Northeast Florida, U.S. Geological Survey, Water- Resources Investigations Report, Vol , 26 pp., ),, : H-ADCP,, Vol. 52, pp , ) :,, 62 pp., ), RAZAZ, M.,, :,, Vol. 55, pp ) Kawanisi, K., Razaz, M., Kaneko, A. and Watanabe, S.: Long-term measurement of stream flow and salinity in a tidal river by the use of the fluvial acoustic tomography system. Journal of Hydrology, 380(1-2), pp , [doi: /j.jhydrol ] 13), Razaz, M.,,,., Vol.54 pp ) Medwin, H.: Speed of sound in water: A simple equation for realistic parameters, J. Acoust. Soc. Am., Vol. 58, p. 1318,

DVIOUT-ajhe

DVIOUT-ajhe 58, 2014 2 OBSERVATION OF TIDAL BORES IN QIANTANG RIVER USING FLUVIAL ACOUSTIC TOMOGRAPHY SYSTEM 1 XIAO-HUA ZHU 2 3 4 5 6 Kiyosi KAWANISI, Xiao-Hua ZHU, Taiki KYUTOKU, Kazuhiko ISIKAWA, Masao IKEDA and