Every year in Japan, slope failures often occur due to heavy rainfall during the wet season and typhoon season. The main reasons for soil failure are thought to be the increase of soil weight from infiltrated precipitation, the decrease in shear strength, and effects of the increase groundwater elevation. It is therefore important to consider to characteristics of groundwater behavior to improve slope disaster prevention. Kiyomizu-dera experienced major slope failures in 1972, 1999, and 2013, and a large slope failure occurred nearby in 2015. The two most recent events occurred since observation of precipitation and groundwater conditions began at the site in 2004. In this research, we determine the relationship between rainfall and groundwater level using both a full-scale model experiment and field measurements. Results indicate strong connection between rainfall intensity and the velocity of increase in groundwater level, indicating that it is possible to predict changes in the groundwater level due to heavy rainfall.

1. [1] T. Ishizawa, N. Sakai, and T. Fukuzono, “Prediction method on rainfall-induced slope failure based on time variation of slope displacement rate observed by model experiments,” Landslides – Journal of the Japan Landslide Society, Vol.50, No.6, pp. 268-278, 2013 (in Japanese).
2. [2] T. Ishizawa, N. Sakai, T. Moroboshi, and T. Fukuzono, “Effectiveness of underground displacement measurement using inclinometer for prediction of slope failure,” Landslides – Journal of the Japan Landslide Society, Vol.50, No.6, pp. 256-267, 2013 (in Japanese).
3. [3] K. Kosugi, T. Mizuyama, and M. Fujita, “Accuracy of a shallow-landslide prediction model to estimate groundwater table,” Journal of Erosion Control Engineering, Vol.55, No.3, pp. 21-32, 2002 (in Japanese).
4. [4] N. Torii and T. Onishi, “A ground water level estimation model with simplified rainfall infiltration and seepage process in surface soil layer,” Journal of JSCE, Vol.67, No.4, pp. 441-452, 2011 (in Japanese).
5. [5] T. Takayanagi, O. Nunokawa, T. Sugiyama, and N. Ota, “Permeable experiment of model slope focused on relationship groundwater and saturation,” Japan Society of Civil Engineers 2009 Annual Meeting, iii-024, pp. 47-48, 2010 (in Japanese).
6. [6] K. Sako, R. Fukagawa, and T. Satomi, “Slope Monitoring System at a Slope Behind an Important Cultural Asset,” Journal of Disaster Research, Vol.6, No.1, pp. 70-79, 2011.
7. [7] Y. Arimitsu, M. Fujimoto, N. Hiaraoka, T. Danjo, Y. Ishida, and R. Fukagawa, “Characteristics of Rain Infiltration in Soil Layers on the Hillslope Behind Important Cultual Asset,” Intenational Journal of GEOMATE, Vol.10, pp. 2109-2115, 2016.
8. [8] K. Sako, R. Fukagawa, K. Iwasaki, T. Satomi, and I. Yasukawa, “Field monitoring on slope around important cultural asset in order to prevent slope disasters due to rainfall,” Geotechnical Engineering Journal, Vol.1, No.3, pp. 57-69, 2006 (in Japanese).
9. [9] J. Nakaya, K. Sako, S. Mitsutani, and R. Fukagawa, “Hydrological Environment in Subsurface Steep Slope – Groundwater Flow Passageway on Slope Behind Kiyomizudera –,” Journal of Disaster Research, Vol.6, No.1, pp. 80-87, 2011.
10. [10] M. Fujimoto, T. Danjo, T. Tsuchiyama, T. Kimura, and R. Fukagawa, “Detection of groundwater movement using a measuring method of sound of groundwater flow on the hillslope behind Kiyomizu Temple,” Journal of Disaster Mitigation for Historical Cities, Vol.8, pp. 145-150, 2014 (in Japanese).
11. [11] T. Danjo, S. Takakura, Y. Arimitsu, M. Fujimoto, T. Ishizawa, and R. Fukagawa, “Detection of groundwater in the slope behind an important cultural asset using an electrical resistivity survey,” Journal of Disaster Mitigation for Historical Cities, Vol.9, pp. 9-16, 2015 (in Japanese).