single-dr.php

JDR Vol.12 No.4 pp. 741-747
doi: 10.20965/jdr.2017.p0741
(2017)

Paper:

Preliminary Study on Long-Term Flooding After the Tsunami

Toshitaka Baba*,†, Junichi Taniguchi*, Noriko Kusunoki*, Manabu Miyoshi**, and Hiroshi Aki**

*Tokushima University
2-1 Minamijosanjima, Tokushima City, Tokushima 770-8506, Japan

Corresponding author

**Nita Consultant Co. Ltd., Tokushima, Japan

Received:
January 13, 2017
Accepted:
April 18, 2017
Online released:
July 28, 2017
Published:
August 1, 2017
Keywords:
long-term flooding, Nankai earthquake, paleographical survey, numerical analysis
Abstract

After the Nankai earthquake in 1946, the resultant flooding lasted for a long time, because seawater remained on land after the tsunami in Kochi city. Large-scale flooding occurred in Ishinomaki city immediately after the Great East Japan Earthquake in 2011. Long-term flooding may hamper disaster responses such as rescue and recovery activities. This paper studied the risks of long-term flooding after the Nankai earthquake in Tokushima city based on a paleographical survey and numerical analysis. The paleographical survey identified statements such as “seawater sometimes flowed onto the land at the full tide,” suggesting occurrences of long-term flooding after previous Nankai earthquakes. The numerical analysis separately calculated values inside and outside the levee.

The tsunami waveforms outside the analysis area obtained by tsunami numerical simulation was used as the boundary condition of the inland flow modeling, that is water was introduced inside the levee when the tsunami water level exceeded the upper end of the levee. The two layers of ground surface and the drain were defined to calculate the flow, including water exchange between the two layers, and the water was drained forcefully outside the levee using a drainage pump. The possibility of long-term flooding in the analysis area is suggested when a large-scale earthquake occurs in the Nankai trough.

References
  1. [1] The Touhoku Regional Development Bureau, “92% of drainage caused by tsunami disappeared ∼ Emergency drainage measures go to final stage,” http://www.thr.mlit.go.jp/Bumon/kisya/saigai/images/34655_1.pdf,2011 [accessed May 26, 2016]
  2. [2] A. Mikami and N. Tsujino, “Damage to Levee Embankments in Kochi City Area during the 1946 Showa-Nankai Earthquake,” Historical Earthquake, Vol.27, pp. 27-39, 2012.
  3. [3] Kochi Prefecture, “Results of the Nankai earthquake long-term flood countermeasure investigation,” 2013, http://www.pref.kochi.lg.jp/soshiki/010201/files/2015041500011/2013040300465_www_pref_kochi_lg_jp_uploaded_life_84591_289930_misc.pdf [accessed Jan. 6, 2017]
  4. [4] Shikoku Region Development Council, “Final report of survey on ground change in Shikoku region – entity of Shikoku regional ground change occurred at the time of the Nankai earthquake (December 21, 1947) and thereafter,” 1956.
  5. [5] Tokushima Prefecture, “Knowing the Nankai Earthquake, monuments of earthquakes and tsunamis in Tokushima,” 2008, http://www.jishin.go.jp/main/bosai/kyoiku-shien/13tokushima/material/tksm_22_3.pdf [accessed Jan. 6, 2017]
  6. [6] Baba, T., N. Takahashi, Y. Kaneda, K. Ando, D. Matsuoka, and T. Kato, “Parallel implementation of dispersive tsunami wave modeling with a nesting algorithm for the 2011 Tohoku tsunami,” Pure appl. Geophys., Vol.172, pp. 3455-3472, doi:10.1007/s00024-015-1049-2, 2015.
  7. [7] M. Miyoshi, T. Tamura, H. Ali, and M. Fujita, “The Relationship between Rainfall and Flood Damage Caused by Inner Water Flooding in Hachiman, Tokushima,” Civil Engineering Society Shikoku Branch Heisei 25 Natural Disaster Forum Proc., pp. 69-77, 2013.
  8. [8] J. Honma, “Discharge coefficient for trapezoidal weir [1],” J. of Civil Engineering Society, Vol.26, No.9, pp. 849-862, 1940.
  9. [9] J. Honma, “Discharge coefficient for trapezoidal weir [2],” J. of Civil Engineering Society, Vol.26, No.6, pp. 635-645, 1940.
  10. [10] I. Aida, “Numerical Experiments for the Tsunamis Generated off the Coast of the Nankaido District,” Bulletin of the Earthquake Research Institute, Vol.56, pp. 713-730, 1981.
  11. [11] The Japanese Cabinet Office, “Study Meeting of the Giant Earthquake Model of Nankai Trough,” 2012, http://www.bousai.go.jp/jishin/nankai/mode [accessed March 26, 2016]
  12. [12] Y. Okada, “Surface deformation due to shear and tensile faults In a half-space,” Bulletin of the Seismological Society of America, Vol.75, pp. 1135-1154, 1985.
  13. [13] K. Sugawara, Y. Sugisawa, and Y. Karino, “Rapid Reconstruction of Pumps for Regional Drainage Destroyed by Tsunami in the Great East Japan Earthquake,” J. of the Japanese Society of Irrigation, Drainage and Rural Engineering, Vol.80, pp. 903-906, 2012.

*This site is desgined based on HTML5 and CSS3 for modern browsers, e.g. Chrome, Firefox, Safari, Edge, IE9,10,11, Opera.

Last updated on Dec. 12, 2017