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calculated. Using SAR image interference analysis, it is possible to observe ground surface displacemet without being influenced by weather and day or night [2]. Here, we use the following 9 SAR images acquired from the ALOS-2 satellite passing over Japan. Interference SAR image (inSAR) analysis of 8 periods (① ~ ⑧) with pairs next to each other were carried out to obtain river bed fluctuations of about 8 km river section on the upstream of 50th groundsel in Omukawa River (Table 2). Table 2 Satellite specification and SAR image analysis periods Items of satilite No Analysis period from to Satellite ALOS PASAR-2, SM-1 mode ① 2014/09/19 2014/11/28 ② 2014/11/28 2015/04/03 Running direction North toward ③ 2015/04/03 2015/06/26 ④ 2015/06/26 2016/03/18 Survey direction Right side ⑤ 2016/03/18 2016/06/24 ⑥ 2016/06/24 2016/11/25 Polaried wave 35.4°HH ⑦ 2016/11/25 2017/03/03 ⑧ 2017/03/03 2017/06/09 2.3.2. Analysis method In SAR image analysis, the width of river channel more than 5 times the minimum image resolution (3m) is needed, so that we choose the middle to downstream river section of Omukawa River as a study site, where sediment discharge observation has been carried out at the downstream end since 2011. In calculating the volume of sediment transport in the river way, the channel was divided into 58 blocks, in order to remove the range of river crossing constructions (e.g., bridges, groundsels etc.) where there is no displacement during floods. Furthmore, each block was subdivided into meshes of 5m squares. The procedure of interference analysis of SAR image was shown in Fig. 6 and Fig. 7. Fig. 6 Procedure of SAR image interference analysis ① Creating an initial interference image (interferogram generation) ② Removal of orbital stripes and topographical stripes ③ Noise filtering (coherence image creation and interference image filtering) ⑤ Precise orbit correction (change unwrapped phase information to height (or displacement) value) ④ Phase unwrap (phase unwrapping) 366