, 18, Observation of bedforms in the downstream reach of Rumoi River by using a brief acoustic bathymetric system Ryosuke AKAHORI, Yasuyu

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1 , 18, Observation of bedforms in the downstream reach of Rumoi River by using a brief acoustic bathymetric system Ryosuke AKAHORI, Yasuyuki HIRAI, Mineo KONDO 1 Ph.D. ( ) 2 ( ) 3 ( ) In this study, a brief bathymetric system which was designed for observing bedform evolution under flood conditions was proposed. The system consists of a RTK-GPS system and a commercially available fish finder, and it was installed on a radio-control air boat. The proposed system is able to be built at a very low price comparing to existing systems employing other professional acoustic bathymetric instruments or multi-beam bathymetric systems. Also, the system is expected to improve the safety of observation of bedforms under flood conditions by using a radio control platform. The proposed system was applied to observe the river bed topography in Rumoi River in Hokkaido, Japan. The result shows that the bed topography observed by the proposed system is qualitatively accurate, and the results of the wavenumber analysis of the observed bed elevation along the downstream direction shows good agreement with that by using the existing multi-beam survey data. Key Words : acoustic bathymetry, bedform, GPS, GIS ) 2) 1 KP-2/0 300m mm/h

1 2 10 21 12 8 2 ADCP 0.75m/s 12 8 12 14 3.

2 ADCP 0.75m/s (1) 3 GPS ADCP Lowrance HDS-8HDS-8 50/200kHz Structure Scan GPS HDS-8 GPS IKKI-RS GPS GPS GPS RTK-GPS Nikon Trimble5700 RTK-GPS KP0.2 HDS-8 RTK-GPS HDS-8 RTK-GPS GPS 3) RC 4) Structure Scan - 455/800kHz 4 RC 5) 6)

RTK-GPS Ground-based reference station: Trimble 5700 300m 2.6m 100m 1.

3 Lowrance HDS-8 a b RTK-GPS : Trimble 5700 A B C Structure Scan: LSS-1 : HRS / Dsub9 : RS232C A: SONER B: PWR/DATA C: ENET a: ENET1 b: SONER : HDS-8 GPS Receiver: IKKI-RS : Structure Scan RTK-GPS Ground-based reference station: Trimble m 2.6m 100m 1.3m 3 50m 50m 5 RC 4 RC 6 (2) HDS-8 1 RC m RTK- GPS 6 RTK-GPS GPS HDS-8 GPS GIS ESRI ArcGIS

4 HDS HDS-8 30cm GPS KP0.2 30cm 4. (1) HDS-8 GIS : Inverse Distance Weighted (IDW) : 0.2m : 0.2m GIS x RMS = GIS 10 8 HDS-8 HDS-8: 1.9m 1.3m : 0.2m HDS-8 (2) 150m 12 8 HDS m m m 1 12 HDS-8 0.2m 1.9m 0.2m 11 HDS HDS MS Excel HDS HDS HDS

5 図 7 HDS-8 による観測結果 2011 年 12 月 8 日第 2 セッション測線が横断方向に密に分布を基に IDW 法を用いて補間することで得られた河床標高コンター図 9 HDS-8 による観測結果 2011 年 12 月 8 日第 2 セッション測線が横断方向に密に分布を基に IDW 法を用いて補間することで得られた標高値に対する陰影図図 8 留萌開発建設部によるマルチビーム測量観測結果 2011 年 12 月 14 日に対する河床標高コンター図 10 留萌開発建設部によるマルチビーム測量観測結果 2011 年 12 月 14 日の標高値に対する陰影図

6 z(m) multibeam 1208 HDS-8 session HDS-8 session distance(m) m z(m) multibeam 1208 HDS-8 session HDS-8 session distance(m) 12 80m amplitude multibeam HDS-8 session1 HDS-8 session k: wavenumber FFT amplitude multibeam HDS-8 session1 HDS-8 session k: wavenumber FFT 5. GIS FFT 1) 33 pp ) Akahori, R., Shimizu, Y.: Bedforms in the Kushiro River: wavenumber analysis of a high-resolution DEM obtained from a multi-beam survey, Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, pp , ) 4 60 pp ) 3 pp ) RC 1 pp ), 50, pp ( )

報文留萌川下流部河床形状の季節的変動に関する観測調査 Observation of Bedforms in the Downstream Reach of the Rumoi River by Using a Brief Acoustic Bathymetric System 川村 * 里実 **

報文留萌川下流部河床形状の季節的変動に関する観測調査 Observation of Bedforms in the Downstream Reach of the Rumoi River by Using a Brief Acoustic Bathymetric System 川村 * 里実 ** 報文留萌川下流部河床形状の季節的変動に関する観測調査 Observation of Bedforms in the Downstream Reach of the Rumoi River by Using a Brief Acoustic Bathymetric System 川村 * 里実 ** 赤堀良介 *** 伊藤丹 **** 近藤峰男 ***** 吉田浩幸 KAWAMURA Satomi,