Tsunami evacuation mound ("inochiyama" or "mountain of life")

Tsunami evacuation mound ("inochiyama" or "mountain of life")
ENTRY DATE: 26 December 2014| LAST UPDATE: 26 December 2014
Categories: Disaster Prevention | Coastal disaster (Hard measures)
Technological Maturity: Being introduced and promoted in Japan.
Technology Owners:

Municipalities all over Japan

Needs Addressed

Provides a place of refuge, for evacuation from tsunami or storm surge where no high-rise buildings and high ground are available nearby. 

Adaptation Effects

Evacuation from tsunamis, storm surges. 

Overview and Features
  • The tsunami evacuation mound is an artificial structure such as a mound, to be used as a refuge from tsunamis. 
  • In some parts of Japan, dating from approximately 300 years ago, one can find refuge spots known as "inochiyama" (meaning mountain of life), which were built into slightly-elevated mounds as refuge from storm surges. As one of the lessons learned from the Great East Japan Earthquake in 2011, there has been an effort in recent years to have a fresh look at evacuation mounds in various places in Japan as refuges from tsunamis. 
Cost

Costs depend on scale. (In the case of the Minato inochiyama in Fukuroi City, on an area of 6,433 square meters, using 1,300 cubic meters of material for the mound, the total construction costs amounted to 215 million yen, of which 114.64 million yen were for construction, 65 million yen for land acquisition, and 7.5 million yen for design.)

Ease of Maintenance

Maintenance is about the same as required for a park, with generally no other work required. 

Considerations (technology transfer criteria, challenges, etc.)

Unlike the case of vertical tsunami evacuation towers and buildings, this technology requires a large amount of land to be available. 

Co-benefits, Suitability for Developing Countries
  • Compared to tsunami evacuation towers or other structures, the inochiyama can be constructed at low cost, considering the capacity in number of persons, and can also be used as a park during non-emergency times. 
  • Compared to structures like a tsunami evacuation tower with a service life of about 50 years, and requiring regular maintenance, the inochiyama is semi-permanent and can accommodate a large number of people. 
Examples

Case study: Fukuroi City, Shizuoka Prefecture

  • Based on its own independent simulation of a tsunami associated with a large-scale earthquake, Fukuroi City developed a tsunami evacuation plan for all residents living along the coast. 
  • In municipalities like Fukuroi with no nearby tall buildings and high ground, the conventional approach was to build a steel-framed evacuation tower to escape from tsunamis. However, such a tower can only be used during evacuation and/or training, the service life is limited, and maintenance is also difficult. 
  • After discussions between the city and local residents' associations, it was decided to utilize the knowledge of prior generations and to create an artificial mound as a facility for tsunami evacuation. 
  • Based on the city's independent tsunami simulation, the tsunami evacuation mound was built to have an elevation of 10 meters above sea level, and to accommodate about 1,300 persons on an area of 1300 square meters. Construction waste soil from other sites was used for the mound.
  • During non-emergency times, it is used as a park and as a place of relaxation for local residents.


Figure: Minato evacuation mound (inochiyama) in Fukuroi City

Information Resources

Fukuroi City, Shizukoka Prefecture (in Japanese)
http://www.city.fukuroi.shizuoka.jp/