World BOSAI Forum 2017 in Sendai
TEAMS Session

Importance of Coastal eco-DRR which
Promote Land-Ocean Interaction in Japan
Osamu Matsuda
Professor Emeritus, Hiroshima University
International EMECS Center
Nov. 28, 2017 : Sendai International Center, Japan

Coastal forest at Tago-no-ura by HOKUSAI (Traditional eco-DRR)

“Fish Breeding Forest”(Uo-tsuki-rin) of Japan has long history

Fish Breeding Forest as eco-DRR
Present legal system of “Fish Breeding Forest” which conserves fish
resources along coast is based on the law enacted in 1897.
About 60,000 ha of coastal forest are designated as F.B.F in Japan.
(Photo taken at Akou Coast, Hyogo prefecture)

Willow branch technology (Ryu-shi-kou) to prevent river bank erosion
used to be very common in Japan (Traditional eco-DRR)

However, land based development of urban area entirely
changed coastline
Water quality has been
improved. However,ecosystem services
by natural sea shore
were seriously affected.

Negative effects on:
HabitatSpawning ground
Nursery

Osaka Bay

Osaka (Kansai) Int. Airport

Tidal flats and sea grass beds disappeared. No natural shoreline at all.

Land reclamation and artificial coastline of urban areaseriously affected function of shallow area
(tidal flat & sea grass bed etc.) andalso land-sea interactions
1947 年撮影（米軍）
太田
川
放水路

京橋
川

元
安川

太田
川

天
満川

2000 年撮影（国土地理院）
太田
川
放水路

天
満川

太田
川

元
安
川

猿候
川

京橋
川

Vertical Wall

猿候
川

瀬野川

Concrete Structure【空中写真から見た埋立状況：広島市周辺】

Inner Hiroshima Bay（中国地方整備局）

１１

Non-eco-DRR

Introduction to the case of rural area:
Satoumi activity of Ago Bay in Shima City, Mie pref.
・Satoumi as a new concept of coastal management
was first proposal by Prof. T. Yanagi in 1998.
・Outline of “Satoumi ”:
Satoumi is a coastal area where biological productivity
and biological diversity has increased through humaninteraction (Ministry of the Environment).

Ago Bay of Shima City was the venue of G7 summit

Satoumi Promotion Section, Shima City:

Ago Bay at a glance looks very nice.
However, there area many problems
such as decreasing pearl production
and fish catch.

Ago Bay Restoration Project: 2003-2007
Interdisciplinary study supported by JST and Mie Pref.
“Follow up” programs: 2008Acknowledgement: Dr. Hideki Kokubu,Mie Fisheries Research InstituteArea of existing tidal flat and area of tidal flat historically lost：existing：lost84 ha
185 haca.70% of tidal flat has been
already lost (indicated in red)
英虞湾海域面積：2710 haTypical “ria” coastline
河口干潟
（現存）
前浜干潟
（現存）
耕作地
（消失）
荒れ地
（消失）

Reduction of Shallow Coastal Area

Reclaimed tidal flat withconstruction of dyke

dyke

Approximately 70% of tidal flat area
has been lost by coastal development

LandWetland

Sea

Former tidal flat area
( freshwater system )Marine environment

Unused wetland
behind of the dyke“Hypertrophic”

Tidal flat in frontof the dyke
“Oligotrophic”

Unused wetland

Tidal flatDyke
Non-eco-DRR

Sea bottom“Eutrophic”

Sea grass bed

Schematic drawing of the characteristics of shallow area in Ago Bay.
Dyke prevented land-sea interaction and material circulation.
Artificial dyke gave negative effects to both sides of dyke.

The Situations around the Dyke

・Legal restriction
・Protection against disasters
・Ownership of the wetland

Very difficult toremove the dyke

New tidal flat restoration project with opening floodgate
started in April., 2010Improvement of small scale land-sea interaction in rural area

堤防に設置された⽔⾨
Floodgate on the concrete dike

⽔⾨解放による海⽔導⼊
Promoting the water exchange

Floodgate on the concrete dyke

Introduction of natural tidal movement
by opening the floodgate was madeNow, this type of restoration is ongoing at 4 sites of Ago Bay.

Outline of Tidal Flat Restoration Area at Ishibuchi
Area:ca.2ha

イベント解放区
海域
Event area
Sea
実験区
水門
Experimental area
NFloodgate
干潟再生海域 D em onstration area
海草移植区 Planting of seagrass

Change of Sediment Quality（AVS, COD）
10

海水導入区 (St.3：+ 0.5m )海水導入区 (St.5：±0m )堤防前自然干潟 (St.6：+ 0.5m )堤防前自然干潟 (St.7：±0m )AVS（mg/g）

8+ 0 .5 m±0 m⑦6+ 0 .5 m

⑥±0 m

海域

③⑤4N

水門
D L:+ 0 .5 m

2

海水導入実験区
調査地点（St. 1 ～7 ）0
事前調査12506/10

09/10

12/10

03/11

06/1109/11

海水導入区 (St.3：+ 0.5m )海水導入区 (St.5：±0m )堤防前自然干潟 (St.6：+ 0.5m )堤防前自然干潟 (St.7：±0m )COD（mg/g）

100

75After introduction of sea
water,
AVS and COD in sediment ofaffected station decreased.

50

250
事前調査06/10

09/10

12/10

03/11

06/11

09/11

Sediment quality improved.
by promotion of waterexchange

Changes of macrobenthos after water exchange
Benthic ecosystem restored (eco-DRR)
50

堤防前自然干潟
再生干潟
3740

アサリ
Ruditapes philippinarum

スズキの稚魚Lateolabrax japonicus

34

種類数（種/m2）

ハゼの稚魚
G oby

Species No./m2
3230

2020

1030

2930
1624

21
1739

18

60

ソトオリガイLaternula marilina

事前調査 3ヶ月後 6ヶ月後 9ヶ月後 11ヶ月後 14ヶ月後 18ヶ月後
2000

堤防前自然干潟
再生干潟

ボラの稚魚
Mugil cephalus

ケフサイソガニ
Hemigrapsus penicillatus

湿重量（g/m2）

1500

1000

778589.5500

イオウハマグリ
Pitar sulfureum

イボウミニナ
Batillaria zonalis

Biomass(ww/m2)

0343.3

7.2

680

421.6

70

事前調査 3ヶ月後 6ヶ月後 9ヶ月後 11ヶ月後 14ヶ月後 18ヶ月後

Future Possibilities: more than 500 candidate areas
Restoration activities are expected to spread out all around Ago Bay.
N

三重県志摩市
阿児町鵜方-2
阿児町神明
阿児町鵜方-1
浜島町塩屋
浜島町
迫子-1

浜島町迫子-2

浜島町浜島
阿児町立神

大王町波切
志摩町和具-1

Total number of fallow
志摩町越賀
志摩町御座
field :
514
志摩町和具-2
Hamajima-town: 128
Ago-town:
191
Daio-town:
98
Shima-town:
97

志摩町布施
田

大王町船越-1

志摩町片田

大王町船越-2

Conceptual view of “ Satoyama ” and “ Satoumi ”“ Satoyama ”
forestagriculture

Village“ Satoumi ”

land-sea interaction

Combined restoration of “ Satoyama ” and “Satoumi ” is more effective from the view point ofmaterial flow and land-sea interaction

Official Policy of Shima City
Basic Plan of Satoumi Creation,
Basic ICM Plan, established by
Shima City Government (2012. 3)

Satoumi Creation Committeewith varieties of stakeholders
officially started (2012. 8 -)Shima City :A New Satoumi Community
We can earn !
We can learn !
We can enjoy !

Public involvement is very important for restoration activities
Clam stocking and seagrass planting

Citizen’s participation
improved
people-sea interaction
アサリの放流Clam stocking

海草の移植 Seagrass planting

“ Better life through wise and sustainable
coastal management ”
Cross-boundary and cross-generational
community collaboration are key element

Thank you for your attention!
Background: Once lost tidal flat area
restored by opening the gate