ABSTRACT

Tojo, K. and Udo, K., 2018. Analysis of beach recovery after the 2011 Tohoku Earthquake Tsunami based on shoreline extraction by ISODATA technique. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 171–175. Coconut Creek (Florida), ISSN 0749-0208.

The 2011 Tohoku earthquake tsunami caused the disappearance of beaches over a wide area. Understanding of the beach recovery process after the tsunami is important for long-term coastal management. This study aimed to develop a highly accurate method of shoreline extraction using satellite and aerial images and to clarify characteristics of beach recovery by analyzing shoreline changes in the tsunami-affected area. Shorelines extracted by the Iterative Self Organizing Data Analysis Technique (ISODATA) with tidal- and wave-corrections agree well with those obtained from topography measurements. In addition, the shorelines extracted from 406 images from before the tsunami to four years after it at 44 beaches demonstrated the shorelines tended to be recovered at plain coasts and not to be recovered at ria coasts. It is confirmed that the method based on ISODATA is highly accurate and significantly reduces the time and labor.

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