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1. Title

Tsunami Disaster Mitigation Technique by Coastal Greenbelt

ID: DRH 12 Japanese traditional forest barrier Discussion note in PNG.
Hazard: Tsunami , Storm surge , Flood

Implementation Oriented Technology (IOT)

Proposer: Tetsuya Hiraishi
Date posted: 31 January 2008
Date published: 01 September 2008
Copyright © 2008 Tetsuya Hiraishi (proposer). All rights reserved.

Japanese traditional forest barrier Discussion note in PNG.


Tetsuya Hiraishi
Head, Wave Division, Port and Airport Research Institute
Nagase 3-1-1, Yokosuka, Japan 239-0826
Tel 81-46-844-5036, Fax 81-46-844-1274
e-mail hiraishi@pari.go.jp

2. Major significance / Summary

Coastal greenbelt composed of mangrove, coconuts, mango etc has an effect to reduce the tsunami flow velocity when its density and width becomes appropriate. The suitable arrangement of greenbelt is necessary to mitigate the coastal tsunami disaster especially in the Asia and Pacific area where the implementation of hard barriers like breakwaters is difficult.

3. Keywords

Tsunami force, Disaster mitigation, Greenbelt, Evacuation support tool, Tsunami countermeasure, Numerical simulation

II. Categories

4. Focus of this information

Implementation Oriented Technology (IOT)

5. Users

5-1. Anticipated users: Community leaders (voluntary base) , Administrative officers , NGO/NPO project managers and staff , Environmental/Ecological specialists , Others

5-2. Other users: Motivated researchers

6. Hazards focused

Tsunami , Storm surge , Flood

7. Elements at risk

Human lives , Human networks in local communities , Infrastructure , Coastal areas

III. Contact Information

8. Proposer(s) information (Writer of this template)

Tetsuya Hiraishi
Head, Wave Division, Port and Airport Research Institute
Nagase 3-1-1, Yokosuka, Japan 239-0826
Tel 81-46-844-5036, Fax 81-46-844-1274
e-mail hiraishi@pari.go.jp

9. Country(ies)/region(s) where the technology/knowledge/practice originated


10. Names and institutions of technology/knowledge developers

Port and Airport Research Institute

11. Title of relevant projects if any

This technology employes local plants according the regional condition. The technique is applicable to any coastal area with several coastal tree plants. (-comment2)

12. References and publications

Greenbelt Tsunami Prevention in South-Pacific Region, Report of Port and Airport Research Institute, Vol.42, No.2, 2003.

13. Note on ownership if any

IV. Background

14. Disaster events and/or societal circumstances, which became the driving force either for developing the technology/knowledge or enhancing its practice

The Papua New Guinea Earthquake in 1998 caused a heavy damage at the northern coast in the country. After the damage, a regional meeting to discuss on the countermeasures against tsunami hazard was held in Madan city in Papua New Guinea. The greenbelt countermeasures were proposed in the meeting because the cost for hard barriers was very large. Several physical and numerical works were done to evaluate the effect of greenbelt against tsunami. The experimental results in the Port and Airport Research Institute demonstrated that at least 15 trees per 100m2 might be necessary to reduce the tsunami force to the level safe to wooden houses.


1998 Tsunami hazard in Papua New Guinea


Japanese traditional forest barrier Discussion note in PNG

V. Description

15. Feature and attribute

A vertical column in the flow becomes an obstacle to reduce a flow velocity. The effect of resistance is evaluated by the drag coefficient term of a column in a steady flow. In the experiment, the drag force reduction in the greenbelt were studied.


Image of greenbelt

16. Necessary process to implement

Costal greenbelt can be planted in an appropriate area facing to tsunami hazard risk. In the first year the plant is very weak so the protection from sea wave and current is necessary.


Plantation of Pandung in Java

17. Strength and limitations

The dense coastal forest is effective to reduce the tsunami force and tsunami hazard. But the flow velocity in a access road between greenbelts units may become very fast. The evacuation along the access road becomes difficult.

18. Lessons learned through implementation if any

Plantation can be done by the local residence. The regional meeting to unite the local opinion is very important.

VI. Resources required

19. Facilities and equipments required

Appropriate vegetation in the target area and enough space in front of coastal villages.

20. Costs, organization, manpower, etc.

Coat is not so large.

VII. Message from the proposer if any

21. Message

The risk due to tsunami, storm surge and high wave increases rapidly in the recent years. The hard prevention like breakwater needs a lot of costs and construction time. The greenbelt coastal prevention technique becomes one of the most effective countermeasures done in few cost and relatively short time.

VIII. Self evaluation in relation to applicability

22. How do you evaluate the technology/knowledge that you have proposed?

It is a technology/knowledge that has fair applicability demonstrated by implementation in one or more field sites.

The experiment was done in the Port and Airport Research Institute.

23. Notes on the applicability if any

Any coastal trees are applicable to the greenbelt (Dense Coastal Forest). For example, a local plant (named BUNI) had an effect to reduce tsunami force. It was revealed in the field survey in Solomon Island (2007).(comment-4)

IX. Application examples


    E1-1. Project name if available

    East coast tsunami prevention project in Indonesia

    E1-2. Place

    East coasts in Indonesia Example of Mangrove plantation

    E1-3. Year


    E1-4. Investor

    Indonesia Government

    E1-5. People involved

    Local residence

    E1-6. Monetary costs incurred


    E1-7. Total workload required

    Two years

    E1-8. Evidence of positive result

    Several hazards were prevented.

X. Other related parallel initiatives if any


XI. Remarks for version upgrade


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