Open AccessExtraction of Inundation Areas Due to the July 2018 Western Japan Torrential Rain Event Using Multi-Temporal ALOS-2 Images
Author(s) -
Wen Li,
Fumio Yamazaki,
Yoshihiro Maruyama
Publication year - 2019
Publication title -
journal of disaster research
Language(s) - English
Resource type - Journals
eISSN - 1883-8030
pISSN - 1881-2473
DOI - 10.20965/jdr.2019.p0445
Subject(s) - flooding (psychology) , coherence (philosophical gambling strategy) , event (particle physics) , field survey , extraction (chemistry) , environmental science , intensity (physics) , hydrology (agriculture) , remote sensing , aerial photos , geography , cartography , physical geography , geology , geotechnical engineering , statistics , psychology , physics , chemistry , mathematics , chromatography , quantum mechanics , psychotherapist
A series of heavy rainfalls hit the western half of Japan from June 28 to July 8, 2018. Increased river water overflowed and destroyed river banks, causing flooding over vast areas. In this study, two pre-event and one co-event ALOS-2 PALSAR-2 images were used to extract inundation areas in Kurashiki and Okayama Cities, Okayama Prefecture, Japan. First, water regions were extracted by threshold values from three-temporal intensity images. The increased water regions in July 2018 were obtained as inundation. Inundated built-up areas were identified by the increase of backscattering intensity. Differences between the pre-and co-event coherence values were calculated. The area with decreased coherence was extracted as a possible inundation area. The results of a field survey conducted on July 16, 2018 were used to estimate the optimal parameters for the extraction. Finally, the results from the intensity and coherence images were verified by making comparisons between a web-based questionnaire survey report and the visual interpretation of aerial photographs.