Research Trends and Results
New Developments in Coastal Management--- Introducing the Concept of Disaster Mitigation and Preventive
Maintenance --SUWA Yoshio, Head; WATANABE Kunihiro (Dr. Agr.), Researcher
Coast Division, River Department
Keywords: coast, disaster mitigation, maintenance

1. Proposals released by Coastal Management
Review Committee
From October 4 to December 16, 2013, the Coastal
Management Review Committee, which consists ofmembers from the Rural Development Bureau, theFisheries Agency of the Ministry of Agriculture, Forestryand Fisheries, and the Water and Disaster Management
Bureau and Ports and Harbors Bureau of the Ministry ofLand, Infrastructure, Transport and Tourism, met 4 times
and released proposals. The committee discussed
coastal management for the future since various issues
have arisen in coastal areas of Japan since the 1999
revisions to the Seacoast Law, including damage bytsunamis resulting from the 2011 earthquake off thePacific coast of Tohoku and progressive deterioration incoastal protection infrastructure. In these meetings, theCoast Division supported the executive office in technicalmatters.
As particularly important subjects, the committee
discussed the "clarification of disaster mitigation
measures in coastal management" and "improvements tocoastal maintenance." This former was a new subject
since "disaster mitigation," which is an issue facing
coastal protection infrastructure, has never been discussed.
The latter subject aims to improve maintenance in coastal
areas, which timely responds to the launch of "First yearof social capital maintenance."
2. Clarification of disaster mitigation measuresin coastal management
The concept of "disaster mitigation," which was newly
introduced to coastal management, had been provided by
the Central Disaster Prevention Council in view of thedamage suffered from the Great East Japan Earthquake.
"Coastal dikes of resilient structure" and "green
embankments" (Figure) which integrates trees with a dike,were both raised by the Coast Division after the Great
East Japan Earthquake and are expected to be effective
towards reducing inland flood heights and ensuring
evacuation time by delaying dike breaks even in the caseof overtopping.
Introducing the concept of "disaster mitigation"requires consideration of land "area", in addition to theconventional concepts of coasts as a "line" and seas as"area." It will, therefore, greatly change the conventionalconcept of coastal management. In the future, it will benecessary to promote comprehensive measures fordisaster prevention / mitigation in coastal areas inclusiveof inland areas. This will require collaboration andcoordination with municipal evacuations, land utilization
planning and other disaster prevention and mitigation【樹木が成長した将来のイメージ】
樹木が成長した将来のイメージ】
measures.
海側低木植樹帯▽T.P.+7.20

1:2.4

1:2.
0

▽T.P.+3.00

Figure: Trees Integrated with Coastal Dike of
Resilient Structure
3. Improvement of coastal maintenance
Coastal protection infrastructure that was constructed
more than 50 years ago and is still in use accounts forabout 40% of the all infrastructure and rapid deterioration
is a related concern. In addition, the inclusion of not
only infrastructure but also erosion control measures forbeaches will make coastal management complicated.
Since the committee discussed the necessity of
preventive management, its importance was also
recognized for coastal areas managed mainly byprefectures.
However, since budgets and humanresources are limited, the need to strengthen cooperation
with private-sector organizations in developing activities
in municipalities or coastal areas was also discussed. Itwas, therefore, made clear that the trend in coastalmanagement is to include local residents without leaving
everything to governments.
4. OtherIn addition to the aforementioned two subjects, thecommittee discussed erosion control measures forbeaches, conservation of Okinotorishima Island, andmeasures for adapting to global warming. In the near
future, systems will be developed so that coastalmanagement may be performed in accordance with thecontents released by the committee.
[Reference]
Material on the Coastal Management Review Committee
http://www.mlit.go.jp/river/shinngikai_blog/kaigankanrin
oarikata/index.html