Effects of Tsunami Wave Erosion on Natural Landscapes: Examples from the 2011 Tohoku-oki Tsunami
The 2011 Tohoku-oki Tsunami affected approximately 600 km of the northeastern coast of the Japanese Honshu Island, leaving traces of destruction on man-made buildings and depositing mud- to boulder-sized sediment. Our field observations at Aneyoshi along the Sanriku “ria” coast, where a maximum run-up height of 39.2 m was recorded, add to the limited number of studies of tsunami wave effects on natural landscapes. We found evidence for (1) tsunami wave erosion that exposed bare rock by stripping basal hillslopes of regolith and vegetation, including trees, (2) transport and deposition of coarse gravel, and (3) scour-hole generation around a large boulder and a large sea wall fragment. Computer simulations indicate that the highest first wave reaching the Aneyoshi coast may have been about 20 m high, that the combined duration of the first three waves was tens of minutes to 1 h, and that the maximum wave velocity on land reached over 10 m/s and probably exceeded 20 m/s in the lower, wide reach of the Aneyoshi valley. We hypothesize that hillsides along the Sanriku Coast have been stripped by erosion of numerous ancient tsunami events recurring at century or even decadal scales, since at least the mid-Holocene. The cumulative effects of tsunami erosion on the hillslopes and their long-term evolution are important potential topics for future studies.
Keywords2011 Tohoku Tsunami Aneyoshi Erosion Hillslopes Ria coast Sanriku Scour holes Sediment
We thank an anonymous reviewer for the useful comments that improved the manuscript. This research was supported by the National Science Foundation-funded Rapid Response Research (RAPID) project (EAR-1138061), and by a research grant from the Tohoku University for an emergency field survey following the 2011 Tohoku-oki Tsunami.
- Baker VR, Costa JE (1987) Catastrophic flooding. Allen and Unwin, Boston, pp 1–21Google Scholar
- Chida N, Matsumoto H, Obara S (1984) Recent alluvial deposit and Holocene sea-level change on Rikuzentakata coastal plain, northeast Japan. Ann Tohoku Geogr Assoc 36(4):232–239 (in Japanese)Google Scholar
- FLO-2D Software Inc (2009) FLO-2D reference manual, version 2009. FLO-2D Software Inc, NutriosoGoogle Scholar
- Friend JA (1992) Achieving soil sustainability. J Soil Water Conserv 47:156–157Google Scholar
- Goto C, Ogawa Y, Shuto N, Imamura F (1997) IUGG/IOC time project, numerical method of tsunami simulation with the leap-frog scheme: IOC manuals and guides. UNESCO, Paris, 130 pGoogle Scholar
- Imamura F, Koshimura S, Oie T, Mabuchi Y, Murashima Y (2011) Tsunami simulation for the 2011 off the Pacific coast of Tohoku Earthquake (Tohoku University model version 1.0). 12 ppGoogle Scholar
- Ohishi M (2011) Time-lapse photography of tsunami at Kawashiro, Omoe Peninsula, Miyako City and the maximum run-up height at Aneyoshi: The geological Society of Japan web site http://www.geosociety.jp/hazard/content0054.html
- Paris R, Wassmer P, Sartohadi J, Lavigne F, Barthomeuf B, Desgages É, Grancher D, Baumert P, Vautier F, Brunstein D, Gomez C (2009) Tsunamis as geomorphic crisis: lessons from the December 26, 2004 tsunami in Lhok Nga, west Banda Aceh (Sumatra, Indonesia). Geomorphology 104:59–72CrossRefGoogle Scholar
- PARI (Port and Airport Research Institute) (2011) Results of the GPS-mounted wave buoys at Kuji, Miyako, and Onahama. http://www.pari.go.jp/files/3609/130613169.pdf
- Shuto N, Satake K, Matsutomi H, Imamura F, Koshimura S (eds) (2007) Encyclopedia of Tsunami. Asakura publishing Co, 368 p (in Japanese)Google Scholar
- Simkin T, Fiske RS (1984) Krakatau, 1883: the volcanic eruption and its effects. Smithsonian Institution Press, Washington, D.C., 400 pGoogle Scholar