EXTRACTION OF FLOODED AREAS DUE TO THE 2011 CENTRAL THAILAND FLOOD USING ASTER AND TERRASAR-X DATA Fumio Yamazaki a) , Jun Shimakage b) , Wen Liu c) , Takashi Nonaka d) and Tadashi Sasagawa d) a) Professor, Graduate School of Engineering, Chiba University, Japan. b) Graduate Student, Graduate School of Engineering, Chiba University, Japan. c) JSPS Research Fellow, Tokyo Institute of Technology, Japan. d) Satellite Business Division, PASCO Corporation, Tokyo, Japan. ABSTRACT In this study, the flooded areas following the 2011 central Thailand flood were extracted using VNIR and TIR images of ASTER and ScanSAR-mode images of TerraSAR-X. The existence of water body was easily recognized for open spaces without trees and buildings from the NDVI value. The surface temperature was also found to be effective in detecting floods in a wide open space although it is limited by its coarse spatial resolution. The SAR intensity images were the most effective because water surfaces showed weak backscatter and they can be acquired at nighttime and under cloud-cover conditions. The extracted results were validated by a high-resolution optical satellite image. Index Terms— Floods, synthetic aperture radar, optical sensors, thermal sensors 1. INTRODUCTION In the autumn of 2011, a large scale flood occurred along the Chao Phraya River in central Thailand [1]. A large amount of water flowed down to wide areas and many associated failures occurred in civil infrastructures and lifeline networks, and hence the flood brought serious effects for a long period. Approximately 9% of the whole nation’s area in 44 prefectures out of 77 prefectures in Thailand suffered from the flood. Many industrial estates were affected, and it caused the disruption of the supply chains of world's industries, such as automobile and electronics. In order to grasp the extents of large-scale disasters at an early stage, the use of satellite remote sensing is effective. In this study, visible near-infrared (VNIR) and thermal- infrared (TIR) imagery of Terra/ASTER and ScanSAR- mode imagery of TerraSAR-X were employed to grasp the extent of the affected area due to the 2011 central Thailand flood. The extracted results were examined by a high- resolution Ikonos image and field survey data [2]. 2. THE STUDY AREA AND ASTER IMAGERY This paper studies on a part of Chao Phraya River basin, about 30 km in width and 110 km in length (“ASTER” in Fig. 1) from the north of Ayutthaya to the Gulf of Thailand through the capital city Bangkok. This region is the heart of Indochina as well as the most important one for the Kingdom of Thailand since it contains the center of administration and economy (Bangkok), cultural heritage (Ayutthaya), international and domestic air transportation hubs (Suvarnabhumi and Don Mueang airports) and also a number of industrial parks operated by Industrial Estate Authority of Thailand. Since the flooded areas were large, ASTER sensor onboard Terra satellite were employed. ASTER has 3 bands in Visible and Near-Infrared (VNIR) radiometer with 15 m resolution, 6 bands in Short-Wavelength Infrared (SWIR) radiometer with 30 m resolution (currently out of order), and 5 bands in Thermal-Infrared (TIR) radiometer with 90 : Study Area : ASTER : TerraSAR‐X : Ikonos 50km Study Area 53.6km x 12.7km ASTER 112.7km x 28.8km Ikonos 7.3km x 5.0km Fig. 1 The Chao Phraya River basin and the areas covered by satellite images used in this study 707 978-1-4799-1114-1/13/$31.00 ©2013 IEEE IGARSS 2013