Eco-DRR as Learned from Local History

Traditional and local
knowledge of Eco-DRR in
and around the Matsuura RiverCover photo: Kitamura Keita

Traditional and local
knowledge of Eco-DRR
in and aroundthe Matsuura River

Photo: Shimauchi Risa

Foreword

When I visited the Matsuura River for the first time, the hot summer had ended and fall had begun.

Atsushi Teramura from Kyushu University showed me the river and numerous traditional flood
control and irrigation facilities. Their usage of stones left the greatest impression on me. Stones cut
from nearby mountains were used to control the river flow, create weirs that lead water toward ricepaddies, and build the city of Karatsu on the sandbanks of the river mouth. The masonry techniquesthat were claimed to have originated from ancient practices in Korea and China can be credited
for the river scenery and streetscapes that have survived until the present day. By simply observing

the masonry all around, one can experience a close connection with the distant, far off continent
beyond the Genkai Sea that the river flows into. The traditional knowledge and technology of thelocal people used to obtain stones is still relied on to harvest the blessings of the river and avoid

disasters. The Matsuura River thus conveys a sense of connection between people across space andtime.

A refreshing sea breeze passes through Niji-no-matsubara stretching at the river mouth. Beyond

the beautiful pine forest forming an arc like a wing, the Karatsu Castle (also called the Maizuru

Castle) stands on a small hill as if it were floating on the wing. If you climb up to the castle whileobserving the stone walls arranged in an orderly fashion, the vast Genkai Sea spreads out before

you, and below you the river flows as if nestled close to the streets of the Karatsu city. If you walk

down to the city and stand on the long bridge crossing the river, you can observe the Karatsu Castle
reflected in the surface of the slowly flowing river. On calm days, the Matsuura River lends its
peaceful presence to the local people.

If you put the city of Karatsu behind you and travel upriver, you can see places where the riveris enclosed on both sides by mountains as well as areas where it flows by rice paddies and small

Photo 1. In the middle of the city of Karatsu

2

Photo 2. Morning on the Matsuura Rivervillages.
These old villages seem to avoid the river by clinging to the skirts of the mountains, and the ricepaddies receive water from the open levees during floods. On the river, masonry weirs deliver water
to the rice paddies and villages, many of them being so old that their construction date is unknown.

The Matsuura River has a long history of deep connections with the local people. The history of

how the local people have avoided disasters while receiving the blessings of the river is overflowing

in and around the river. It serves as a valuable space that facilitates learning about the traditional
relationship between people and the river. During spring, Japanese dace (ida) move upstream tobreed. On my first visit to the Matsuura River, I once again learned about the importance of yearly
rhythms of the river that repeat over and over again.

This river is featured in the second edition of the series “Eco-DRR as Learned from Local
History” . If this series can contribute to building improved relationships between human andnature amidst the current climate and socioeconomic changes by considering the history of therelationship woven in the Matsuura River, then the hard work of all those involved in its publication

will be rewarded. Although we have a long way to go, steady progress is being made in thisendeavor.

Yoshida Takehito

Research Institute for Humanity and Nature, Eco-DRR Project, project leader
Research Institute for Humanity and Nature, and University of Tokyo

Photo 3. The Matsuura River and Niji-no-matsubara, as seen from the
Karatsu Castle

3

Contents
Foreword
Yoshida Takehito …… 2
Traditional and Local Knowledge from the Matsuura River: The Useof Local Wisdom and Technology for Facing Nature's Blessings andTroublesFukamachi Katsue …… 6
【The History of the Matsuura River】
Overview of the Matsuura River
Teramura Jun ……10
Activities of Local People in the Matsuura River Basin During theAncient and Medieval Periods
Ichimoto Naoyuki ……14
Modern Irrigation and the Ceramics Industry on the Matsuura River
Ichimoto Naoyuki ……18
The Matsuura River and Karatsu Coal Fields in Modern Times
Teramura Jun ……20
【Remaining Traditional and Regional Knowledge】
The Stone Weirs of the Matsuura River
Teramura Jun……24
The Daikoku Weir and Other Stone Weirs Nationwide
Teramura Jun ……30
Haginoo Weir and UmankashiraPhoto: Shimauchi Risa

4

Teramura Jun……36

The Floodplain Open Levees of the Matsuura River
Teramura Jun, Kitamura Keita ……40
The Floodplain Open Levees of Okawano
Kitamura Keita ……46
The Cross-levees of Ono
Teramura Jun ……52
The funagata yashiki of the Hidari-Ikisa River
Teramura Jun ……54
The flood submerging bridges and low-level crossings of the
Matsuura River
Teramura Jun ……56
Niji-no-matsubara
Kitamura Keita ……60
【Future Traditional and Local Knowledge of Azamenose】
The Restored Floodplain Wetlands of the Matsuura River: Efforts at
Azamenose
Hayashi Hironori ……64
Collaboration With Local Society
Hayashi Hironori ……72
The Environment of Azamenose
Hayashi Hironori ……74
The Flood Control Function of Azamenose
Kitamura Keita ……78
【Traditional and Local Knowledge of the Matsuura River】
Traditional and Local Knowledge of the Matsuura River
Shimatani Yukihiro ……84

5

Traditional and Local Knowledge from the Matsuura
River: The Use of Local Wisdom and Technology for Facing
Nature's Blessings and Troubles
Kyoto University

Fukamachi Katsue

Water from the Matsuura River, which flows

through the northern part of Saga Prefecture, hasbeen used to sustain the daily life and farming
needs of the local people. Moreover, the river
has also been used for Japanese dace fishingand transportation. The river's floodplain has ahistory of disasters, such as floods caused by heavy

rains, and the locals have cleverly used its waters,stones, and flora and fauna to devise methods to
Photo 1. Matsuura River (Okawano, Imari City)

reduce damage from these natural disasters. For

example, Umankashira is Japan's oldest facility toenable rice paddy cultivation using the siphoning
principle to deliver water in a channel that is higher
than the surface of a river (the Matsuura River)to an opposite riverbank. Moreover, this facility
has continued to function along with the nearby
Haginoo Weir. Umankashira has been recognizedby the Japan Society of Civil Engineers as a Public

Works Heritage, which serves as the core of thelocal heritage focusing on nature, history, andculture. On the Matsuura River, there are a great
Photo 2. Civil engineering heritage Umankashira (Matsuuracho, ImariCity)

deal of examples of flood control and local irrigation

heritage, which reflect the local characteristics along
the river.

Moreover, the Matsuura River is surroundedby three prefectural natural parks, including
Kurokamiyama, Genkai Quasi-National Park, andNijinomatsubara (designated as a place of scenic

beauty). It is a location rich in natural and cultural

heritage. The riverside features stone monuments,
places of worship, nature (such as large trees), andvarious land features that tell the history of natural
Photo 3. Haginoo Weir (Matsuuracho, Imari City)6

and other disasters that have occurred there.

Through investigations and discussions focusing
on the traditional and local knowledge from the

Matsuura River basin, this booklet introduces

various applications of local wisdom andtechnologies for facing both nature's blessingsand troubles that connect the past, present, andfuture. This booklet is composed of four sections:
The History of the Matsuura River, Remaining

Traditional and Regional Knowledge, Future
Photo 4. A stone monument restored after a large flood (Matsuuracho,
Imari City)

Traditional and Local Knowledge of Azamenose, andTraditional and Local Knowledge of the Matsuura

River. This work attempts to comprehensively

explore methods of coping with natural disasters
that have been learned through past experiences

as well as methods of using resources provided
by nature. Along with scientifically validating

the meansof disaster prevention and mitigation

through geographical features, such as floodplain
embankments and ecosystems, this booklet
introduces efforts to link local and traditional

knowledge to town planning as well as actual
Photo 5. Large trees and a religious spot near the cross-levee (Ochicho,
Karatsu City)

examples showing the techniques and potential of
public works, such as river improvements.

The keyword of this booklet is Ecosystem-based

Disaster Risk Reduction (Eco-DDR), an approachthat emerged from international disaster prevention

and mitigation efforts. Healthy, rich ecosystems

play the role of directly reducing disaster risk andindirectly alleviating disaster impact. Let us allconsider how to respond to natural disasters whileemphasizing the importance of such ecosystems andthe local cultures that arise from them.
Photo 6. Discussion during a Matsuura River Eco-DDR

7

【The History of the Matsuura River】

Photo: Shimauchi Risa

The History of the Matsuura River
Kyushu University

Teramura Jun

Overview of the Matsuura River

plains, and in the mountains, there is a repeating

through the cities of Karatsu, Imari, and Takeo in themain channeland its tributaries is gentle, similar to the

The Matsuura River is a Class A river that runs
northern part of Saga Prefecture. With a river basin

area of 446 km , a river channel length of 47 km, and2

pattern of valleys and lowlands. The riverbed of thecurrent upstream.

headwaters originating in the Kurokami mountainAs a result, up until the Meiji and Taisho eras,

its main tributaries are the Kyuragi River and the

middle reaches of the river was common on thesystem, its river mouth flows into Karatsu Bay, andTokusue River.

transport by riverboat from the river mouth to the
Matsuura, Kyuragi, and Tokusue rivers.

There are plains in the downstream area and the Niji-

The river basin has a population of approximately

left bank near the river mouth. As well, on the left

Karatsu, which is located at the river mouth andno-matsubara pine forest on the coast, located on its
bank of the Matsuura River are Karatsu Castle and thestreets of Karatsu City.

Aside from the downstream area, there are no large
KaratsuCastle唐津城

虹の松原

DaikokiDam
大黒井堰

and agriculture production, at approximately 84 % and
15 %, respectively.

Many types of animals and insects inhabit the
Matsuura River basin. There is a rich variety of

minnows. Among these fish is the Japanese dace,which is locally called the ida and appears in legends

funagata
yashiki
舟形屋敷

Okawano floodplaincommon types of land use in this area are rural areas

freshwater fish, beginning with ayu and freshwaterOnocross-levee
大野横堤

Ikisa
River
伊岐佐川

Azamenose
アザメの瀬

大川野氾濫原霞堤
embankments

occupies only 1 % of the basin area. The most

(1) Fauna of the Matsuura River

KaratsuBay
唐津湾

Niji-no-matsubara

TokusueRiver
徳須恵川

100,000 people, with the only urban area being

throughout the region.

Cicadas are one insect commonly seen in the
MatsuuraRiver
松浦川

mountain valleys. In recent years, damage caused by
KyuragiRiver
厳木川

wild boars and deer has increased; therefore, fences
have begun to appear on farmland in rural areas

Haginoo Weir
萩の尾堰
Umankashira
馬ノ頭

between fields and forests.

The Azamenose in the Matsuura River basin is awetland created under a national nature restoration
Kurokamiyama
黒髪山系
systemproject, and in the richly restored natural environment,

bitterlings and shellfish abound in the ponds andchannels created.

Image 1. Matsuura River basin overview (created based on a Kashmir
3D super topographical map)10

(2) Geology of the Matsuura RiverBasin

The geology of the Matsuura River basin
can be broadly divided into two areas;east from the Kyuragi River and thedownstream portion of the Matsuura
River itself are composed of granite andgranodiorite in the granite series, whilemost of the remainder is made up ofsandstone, mudstone, and shale zones of
the Tertiary system.

When granite-series rocks are weathered,they become decomposed granite(sandy sediment), facilitating sedimentdisasters. This type of geology produces

a great volume of sand, thus leading therivers to become sandy, though they domaintain some relative clarity throughout
the water column.

Tertiary-system mudstone and sandstone

are comparatively soft, weather rapidly,

and are prone to landslides. There
are, therefore, many landslide zones
in mountainous areas. Moreover, areas

with this geology and terrain frequently

have terraced rice fields. The Matsuura
River basin also has such landscapes,

including the Terraced Rice Field of

Warabino, which has been designated as
an important cultural landscape.

Furthermore, sandstone is a soft type ofstone, thus making it easy to quarry andprocess. There are several quarries in theriver basin that produce stone for use inwalls and other such purposes.

Koshidake in the Kurokami mountainsystem, where the headwaters of theNo

L e g e n d Classifications Formation
symbols

Formation period

K12_pim_a

Igneous728

K12_pam_a

Igneous101

Pg2_sbs

Sedimentary

Mesozoic, early Cretaceous, Aptian,
Albian100

Pg3_sbs

Sedimentary167

Pg3_soss

Sedimentary

8

H_sad

Sedimentary

10

H_ssd

Q32-33_std

Sedimentary

Dune deposits

Coastal and dune deposits

Mesozoic, Quaternary, Holocene

488

N3-vba_ai

Igneous

Alkali basalt and trachybasalt, intrusive rock886

D 3 - P 1 _ Igneous
mscma_hg

Mesozoic, Neogene, Miocene,
Messinian to Pliocene

790

D3-P1_msp_ Metamorphic
hc

692

14

549

N3_vis_ai

Sedimentary

Igneous

Granodiorite, tonalite, mass, island arc / Mesozoic, early Cretaceous, Aptian,continental
AlbianGranite mass island arc / continental

Brackish water strata and marine and non-marine M e s o z o i c , Pa l e o g e n e , E o c e n e ,mixed strata sandstone, sandstone and mudstone Lutetian to Priabonian
interlayered and sandstone and mudstone
Brackish water strata and marine and non-marine M e s o z o i c , Pa l e o g e n e , E o c e n e ,mixed strata sandstone, sandstone and mudstone Lutetianinterlayered, and sandstone and mudstone
Marine strata sandstoneM e s o z o i c , Pa l e o g e n e , E o c e n e ,Lutetian

Valley plain, intermountain basin, river and coastal Mesozoic, Quaternary, Holocene
plain alluvium

Mesozoic, Quaternary, Mid-late late
Pleistocene, late Pleistocene

Mafic schist,
Pa l e o z o i c , Up p e r D e v o n i a n t ohigh P / T type wide area metamorphic rock, Permian age Cisuralian period
garnet zone
S e r p e n t i n i t e , h i g h P / T t y p e w i d e a r e a Pa l e o z o i c , Up p e r D e v o n i a n t ometamorphic rock, marginal mud belt
Permian age Cisuralian period
Andesite and basaltic andesite, intrusive rockMesozoic, Neogene, Miocene,
Messinian to Pliocene

Image 2. Matsuura River basin geological map (Geological Survey of Japan, AIST,
created from seamless Digital Geological Map of Japan, scale 200,000:1)

Matsuura River was a local source oftimes as well as their exchanges with distant regions.

been found in far-off locations, including

The Matsuura River basin also contains the Karatsu coal fields,

mounds of Okinawa. This provides clues

a great amount of coal, spanning from the last days of theobsidian production. This stone has
the Korean peninsula and the burial

which contributed to the modernization of Japan by yielding

to the activities of the people living inTokugawa shogunate to modern-day Japan.

the Matsuura River basin during ancient11(3) The Matsuura River its History

increasingly used and altered. The first Karatsu

obsidian stone tools have been found around

Matsuura and Tokusue rivers into one river. They

Numerous burial mounds and ruins containing

Koshidake, which serves as the source of the Matsuura
and was formerly also a major source of obsidian.
Moreover, with the presence of many such burial

mounds discovered in the river basin area, we cansee that people have inhabited the region since thed a i m y o — S h i m a n o k a m i Te r a s a w a — j o i n e d t h ewere once separate rivers which flowed downstream

into the plains. He also planted a pine forest along thecoast, where he strictly controlled logging, in order for
the forest to serve as a windbreak.

ancient periods. In the medieval period, the powerful

Along with Karatsu Bay, the mouth of the Matsuura

Matsuura River basin to Hirado.

served well as a port, and the industries based

Matsuura Clan controlled a wide area, from theIn the early modern period, a complicated variety
of domain (han) administrative divisions existed in

the area, including lands directly controlled by the
Shogunate—such as Karatsu-han and the Shogunate

territories and the Saga, Ogi and Hasunoike-hanof Hizen Province. Although Hizen Province wasRiver (which was unified by Shimanokami Terasawa)
there developed under the Karatsu Domain. The

Hizenshusanbutsuzuko (Illustrations of Hizen

Products) depicts products, such as coal, ceramics (e.g.,jars) and Japanese paper, being delivered by riverboat
on the Matsuura River to Karatsu and then shippedaround Japan.

controlled by the Saga Domain, it was further divided

Karatsu was also a major whaling center. The

political division of this area was extremely complex.

(ukai) as well as freshwater clam fishing. In addition,

into the Ogi and Hasunoike Domains, thus the

However, the smaller domains of the Hizen Province
were closely connected to the main Saga Domain.

Broadly speaking, the lower reaches of the Matsuura

River belonged to the Karatsu Domain (directly

controlled by the Shogunate), whereas the upper
reaches were Saga Domain territory.

Through out modern history, the river has been

KaratsuCastle唐津城

Hizenshusanbutsuzuko depicts fishing with cormorants
in terms of fish, the river is well-known for ayu andida. Ida is the Japanese term for Japanese dace, and at
the beginning of spring, these fish move upstream tobreed. The first storm of spring was, therefore, called

the “Ida Storm,” and the Matsuura River was called
the “Ida River.” Although there are many depictionsof the river's ayu in the Manyoshu, it is generally
believed that this may actually depict the nearby
Tamashima River.

During the Edo Period, Weirs were built on rivers
to increase agricultural land, and technology wasdeveloped to create long waterways that can carry
Niji-no-matsubara
虹の松原

water to rice paddies. Many river structures werebuilt using various methods; these include the stone
Daikoku Weir on the main Matsuura River andUmankashira, with a waterway under the river madeby Narutomi Hyogo Shigeyasu, which is revered as

the “god” of flood control in Saga and elsewhere even

Tokusue River

徳須恵川旧河道
former riverbed

now. There are also many Weirs and waterways thatcurrently take water from the river and transport itover great distances, operating the same way they did
Matsuura River
松浦川旧河道former riverbed

when they were built long ago.

Moreover, rice paddies, which are the primary reason

for building irrigation facilities, are a common sight
Image 3. Matsuura River downstream riverbed changes (created basedon a Kashmir 3D super topographical map)
12

along the Matsuura River. Due to the many villageslining its banks, we can see how the river provided

the Matsuura River have maintained a constant

the riverbanks are situated on a floodplain that has

transformed over time, these transformations are not

the foundation for human activity. However, because

experienced frequent flooding, it was necessary todevise methods for reducing flood damage.

relationship with it. Although this relationship hasdelineated by periods. They are always connected andbuild upon one another.

In many villages, houses were built on natural levees

By examining the region through the perspective of

the floodplain. As seen in the Okawano village, several

are connected and that the accumulated experience ofor mountainsides much higher than the elevation of
methods such as ring levees, were built surrounding

villages on low-lying land. In addition, because

the river, we can understand how humans and nature
the past leads us to the present day.

riverbank rice paddies were on floodplains, floodplain

open levees were formed to construct rice paddies
thereby reducing potential flood damage to the land.

Traditional flood control and irrigation facilities,
including embankments (e.g., open levees), were

not just built as we see them in their current form.

Successively higher embankments were constructed
over many years, thus providing a mechanism tolimit damage to fields for farming and houses. This

“try and see” method is an approach to traditionalriver technology that gradually improves functioning
based on the years of experience gained throughrepeated disasters. In the “try and see” method, theaccumulated methods of interacting with the riverare not merely old technology but are linked to thepresent and continue to be applied.

Works cited
Encyclopaedia of Rivers, p. 605
Matsuura River System Development Plan, Ministry of Land,
Infrastructure, Transport and Tourism, Kyushu Regional
Development Office, Takeo River Office (July 2009)
Geological Survey of Japan, AIST, Seamless Digital Geological
Map of Japan, scale 200,000:1 (detailed version, data updatedon: June 14, 2020), https://gbank.gsj.jp/seamless/
Sugihara, Shigeo. Estimating the Origin of Obsidian Relics

Azamenose is a wetland with rich natural resources

Excavated at Koshidake, and the Ryo Hirasawa and Suzuoke

restoration project in the Matsuura River middle

Ide, Isei. A History of Coal Mining in Saga Kinkado (February

and flood control functions created through a naturebasin, where traditional flood control technology wasapplied to create a natural environment.

Since ancient times, the local people living near

Ruins of Kyushu (2011)1972)
Karatsu History Compilation Committee. History of Karatsu(reprinted version), p. 17 (1991)
Kizaki, Seihyo, Hizenshusanbutsuzuko, Coal and Ceramics
Overview, copy National Archives digital archives

Painting 1. Hizenshusanbutsuzuko, fishing with cormorants (National Archives digital archives)
13

Activities of the Local People in the Matsuura River
Basin During the Ancient and Medieval Periods
Naoyuki Ichimoto
Imari Municipal Board of Education

Ichimoto Naoyuki(1) Status of Matsuura River Basin Ruins

Matsuura River basin. The above map is an excerpt

headwaters on the eastern slope of Jinroku

ruins issued by the government. Along the banks of

The current Matsuura River runs from its
Mountain in Yamauchichoinubashiri in Takeo City
to the river mouth in Karatsu Bay. The river passes
through the cities of Imari and Takeo as well as the

Karatsu City area and has a total length of 45.25

km. These three cities contain a large number ofruins from the primitive to early modern times,
giving the area an abundance of historical assets.

Water is essential for human life; therefore, a very
high number of ruins have been found in theof this basin area from a map of Saga Prefecture
the main Matsuura river, there are 191 ruins sites,
among which 172 are from the ancient to medieval
times. Let's have a look at a typical site along theriverbank to understand the historical role of the
Matsuura River.

(2) Daikoji Temple Ruins (Paleolithic to Jomon
Periods)

Daikoji Temple is a scattering ground andImage 1. Distribution of ruins in the Matsuura River basin (added to the Saga Prefecture ruins map)14early modern cemetery mixed site dated to thelength would exceed their width) around the Aira

Matsuurachomomonokawa. Geographically speaking,years ago). The following group is from the period

Paleolithic to Jomon periods and located in Daikoji,
the Matsuura River basin flows in a northerly
direction, meandering from Takeo City. The ruins

are situated on a 38 m river terrace created by theriver itself. The current distance in height from theriver is about 15 m. The excavation was conductedby the Imari Municipal Board of Education in 1990–
1991 due to a road improvement project in the area.

Here, I will introduce the results of the Paleolithic

Tanzawa ash-fall deposit period (29,000 to 26,000
wherein knife-shaped stone implements made offlakes of indeterminate form were primarily used(stone flakes chipped from the base stone throughvarious methods, such as striking) (the top left twoitems and the bottom right item in the photo). The

last is the group from the period wherein microlith

blades were primarily used (the left four items inthe bottom of the photo).

and Jomon period studies. Based on the excavatedartifacts, the site is thought to be from the Upper

Paleolithic (approximately 30,000 to 15,000 yearsago) and Jomon Periods (15,000 to 2,000 years ago).

Among these, there are Paleolithic stone implement
groups from three periods. The oldest of thesegroups is from the period that primarily used knife-

shaped stone tools (the top right two items in thephoto) made of stone blades (as a standard, they

were cut from the base stone to ensure that their
Photo 1. Artifacts excavated from the Daikoji Temple ruins

Light
Blue: Matsuura River
水色：松浦川Navy Blue: Matsuura River basin ruins
青：松浦川流域の遺跡（旧石器時代～中世）(Paleolithic to medieval periods)
黄色：松浦川流域の遺跡（近世）Yellow:
Matsuura River basin ruins (early modern)

15

Although the Jomon Period flint arrowhead artifacts

thought to have built campsites. While traveling tothey were used is unclear.

have built campsites, due to the discovery of piles

have been excavated, the exact period during which

In Imari City, Koshidake mountain provides a major

source of obsidian. This obsidian was treasured
as quality material for stone implements from the

Paleolithic to the first-half of the Yayoi Period. It
was traded throughout Kyushu and was transported

as far away as Okinawa and the Korean peninsula.
Since the Daikoji Temple ruins are nine kilometers

away from Koshidake, which is relatively close,
most of the stone tool materials from any period are

and from Koshidake, these people are thought toof heated stones that were in the ruins, serving
as proof of camping activities. This is a slightly

elevated area near the Matsuura River where it iseasy to obtain water, thus making it optimal forcampsites. The area is, therefore, thought to havebeen repeatedly used by people across multiple

periods. It is also thought that people made stone
tools from this obsidian and hunted at thesecampsites.

therefore Koshidake obsidian.

(3) Ukikunden Ruins (Yayoi Period)

This obsidian, as a quality material for stone tools,in Karatsu City. They are in front of two small hills

was a lifeline for the people in those periods. Therewas, therefore, a need to regularly obtain this stone

from Koshidake. There was, therefore, a need toregularly obtain this stone from Koshidake. While
traveling to and from Koshidake for this, people are

The Ukikunden ruins are located in Ukiazakunden
to the northeast of Yuhiyama, in the flat area of the
Matsuura River.

Ever since Rokuji Morimoto introduced these ruins
in 1930, the East Asian Archaeological Society anda joint Japanese-French expedition have conductedstudies, and the Karatsu Municipal Board of

Education has also conducted numerous excavations.
Precious artifacts have been excavated, and theHizen Karatsu City Excavated Artifacts (first-half of
the Yayoi Period; thin bronze swords, thin bronze

halberds, bronze swords, bronze halberds, bronze

dagger-axes, bronze mirrors with multiple knobs
and minute patterns, bronze bracelets, magatama,

green necklace gemstones) have been designatedas “National Important Cultural Property,” and the“Copper Tongue Excavated from the Ukikunden

Ruins” is a prefectural important cultural property.
The primary focus of this site is the late Jomon to

the early Yayoi Period shell mounds and the lateearly Yayoi to late Yayoi Period jar burial tombs.

Remains of dwellings have also been found, thus
a complete lifecycle can be seen in these ruins. In

particular, the 126 jar tombs indicate the scale ofthe site.

(4) Kurisozui Mound Tomb (Kofun Period)

The Kurisozui mound tomb is a circular ancient
tomb with a rectangular front 108.5m in length andPhoto 2. Bronze swords and bronze halberds excavated from the
Ukikunden ruins (Karatsu Municipal Board of Education, 1997)16

is located in Sozuisako in Karatsu City. According

to excavations conducted thus far, the site may bedated to the early fourth century. Regarding theThus far, a dry moat, partial stone barrier, and a

dugout stone chamber, and the front has a dugout

altered pentagon shape and features small earthwork

well have been found. The main compound has aninternal structure, the rear circular portion has aenclosures and hillside earthwork enclosures. This

stone chamber crossed by wooden beams. In theis a valuable ruin showcasing the conditions of astone chamber, there may have been an unusual

residential castle during the Warring States Periodboat-shaped wooden coffin in this type of tomb.

shogunate in western Kyushu, so Takeo City has

In the same chamber, one mirror and two green

designated it a historical site.

pipe-shaped necklace gemstones used as grave
accessories were discovered as well as a small knife

between the stone roof and the top of the chamber.
The mirror was a shipborne dragon mirror from thelater Han Dynasty, thus indicating that the person
buried in the tomb had a connection to mainland

Asia. Due to its academic importance, Karatsu City
has designated it a historical site.

(5) Sumiyoshi Castle Footprint (Medieval Period)
The footprint of the Sumiyoshi Castle is locatedin Yamauchichomiyano, Takeo City. The hilltop
castle, at the eastern foot of Kurokami mountain,
also served as a residence. Although the era when

it was constructed is unclear, the Goto Clan, which

controlled the Takeo City region, repaired the ruinsin the Warring States Period, which is how they
arrived at their present size and form.

Photo 3. Kurisozui mound tombnortheast)

Overview of Sumiyoshi
castle ruins

Stone EnmaRoad

Photo of dry moat (from theCastle entrance

Earthworks
Earthworks
Matsuura River( Sumiyoshi River)

Earthworks

ChannelSlope trench

Moat

Stone pagodas

Image 2. Sumiyoshi Castle footprint overview
17Modern Irrigation and the Ceramics Industry
on the Matsuura River
Imari Municipal Board of Education

Ichimoto Naoyuki(1) Irrigation Facilities with Continued Use in the Present Day; the Umankashira Weir

The irrigation facility called Umankashira is located in Matsuurachomomonokawa in Imari City. Construction forthis facility was planned by Narutomi Hyogo Shigeyasu—who was a chief retainer of the Nabeshima Clan and was
knowledgeable in civil engineering and engineering. The site was completed in 1611 (year 16 of the Keicho Era in

the Edo Period); the Structure was built to bring water from the lower water level of the Matsuura River to theMomonokawa plateau to enable rice paddy cultivation.

In terms of the order of the working mechanism for irrigation; first, a water diversion channel was created from Oide,
which has a higher water level and is approximately 1 km upstream, to draw in water from the main river. Next, thediverted water is drawn along the channel to the dam and flows down from the riverbank. Third, the water is thensiphoned across the riverbed using the rear part of an inverted siphon onto the opposite bank.

The inverted siphon water pipes were lengthened by connecting numerous bottomless pails with wooden connected
pipes called oketoi. It is believed that they were used to disperse the load on the pipes placed on the riverbed, whichhave now been replaced by concrete pipes.

However, the structure has functioned unchanged since the Edo Period, and it has been certified by the Japan Societyof Civil Engineers as a recommended civil engineering heritage.

Oide
Umankashira Weir

Photo 1. Aerial photo of Umankashira and related irrigation facilities (notations by the Geospatial Information Authority of Japan)
18

(2) Matsuura River Basin Kiln Sites

At the end of the medieval period, it is said that the Hata Clan, who were daimyos during the Warring States Period,
brought potters from Korea to start pottery production in Hizen. The Kishidake Castle, which was their base, wasgeographically close to, yet not directly in the Matsuura River Basin. Pottery production is considered to have started

in the 1580s in this area. However, with the Hata Clan's subsequent replacement (kaieki), the Korean potters left the

Kishidake area, and in the Keicho Era (1596–1615) pottery production had become scattered, resulting in the numberof kilns rapidly increasing. Due to these factors, there are many remains of kilns found in the Matsuura River basin
today. (reference: the ruins map in the previous section)

In Okawa-cho kawahara azatsuji in Imari City, there are six such kiln sites. Excavations have revealed that four kilns
originated from the same period of Kishidake pottery production to the time that this production dispersed. Thesesites are in three clusters; the Yakiyama upper kiln site, Yakiyama middle kiln site, and the Yakiyama lower A kiln site.

All of these were operated from the 1580s to around 1600; they are waritake kilns originating from the oldest period

for kiln sites in Hizen. At this stage, there was no mass production in firing or other measures for increased efficiency,

and there are no traces of multi-layered firing. The kilns at all these sites fell apart with the passage of time, and latercollapsed, thus their exact size is unclear.

Compared to the other two clusters, the Yakiyama upper kiln site is characterized by having produced a rich variety
of products. Among the pottery excavated were decorated Karatsu bowls and plates, other bowls and plates, mortars,

pots, lipped bowls, water pitchers, bottles, lids, vases, and jars. Out of the three site clusters, this was the only site
producing particularly large jars and other small and mid-sized items together.

At the Yakiyama middle kiln site, bowls, plates, pots, water pitchers, bottles, and other items have been excavated, but
no decorated Karatsu items have been found.

Decorated Karatsu plates, bowls, pots, bottles, mukozuke side dishes and lids, and other items have been unearthed at
the Yakiyama lower A site.

(3) Karatsu Ware Distribution and the Matsuura River

The name of the shipping port was used for Edo Period ceramics, not the area of origin. Therefore, the name Karatsu
was used, despite the fact that the products were produced in Imari and Takeo. These ceramics were most likely

shipped down the Matsuura River from these cities to Karatsu, because sunken Karatsu ware has been found at
various places in the riverbed.

Although at a glance it would not seem as if the Matsuura River and Karatsu ware were directly related, they have aclose connection.

Photo 2. Decorated Karatsu bowl and lid excavated from the Yakiyama upper kiln site
19

The Matsuura River and Karatsu Coal Fields
in Modern Times
Kyushu University

Teramura Jun

Image 1. Hizenshusanbutsuzuko, Coal and Ceramics Overview (National Archives digital archives)

There are many burial mounds in the Matsuura River

Coal was also used in large quantities in salt and tile

area since ancient times. In addition, at the beginning

Since ancient times, this region featured industries

basin, thereby indicating vibrant human activity in theof the early modern period, the originally separated
Matsuura and Tokusue rivers were joined, and themodern positions of the river and its mouth were
decided. Karatsu Castle was built alongside the Matsuura
River mouth, which served as a port during this period.

Karatsu prospered as a seaport on Karatsu Bay, and due
to riverboat transport on the mainstem of the Matsuurathat used large amounts of firewood, including Tatara
steelmaking and salting. There were, therefore, many
treeless mountains, and it is well known that a significant
amount of soil was lost.

Using coal in place of firewood provided a replacement
for the natural resource of wood.

River, as well as the Kyuragi and Tokusue branches,

The first part of the Karatsu coal field mined in earnest

routes. The Matsuura River supported trade in thein 1792 (year 4 of the Kansei Era), following which thethese channels flourished as shipborne transportation
Karatsu Domain as well as that from nearby Imari, Taku,
and Takeo.

Developments supporting transportation on the

Matsuura River from the final days of the Tokugawa
Shogunate to modern times were brought about by the
Karatsu coal fields.

was the coal mine in Ochimura along the Kyuragi River
coal field was fully opened in the Bunsei Era (1818–1829).
During this period, the primary method used for mining
was a “shoestring” method consisting of digging a holeso narrow a person could barely squeeze in. The person

would then load coal into a bamboo basket that was
pulled up to the surface. The tunnel dug for mining wascalled a mabu. Mabu was a common term in the mine

(1) Beginning of the Karatsu coal fields

tunnels, and it was also used in the Iwami silver minepeasant farmer in Doumeki, Kishiyama, Kitahata during

manbo and manpo.

The Karatsu coal fields were discovered by accident by a
the Kyoho Era (1716–1735). The Karatsuryakkijofuzuisen

and the Sado gold mine. There were also regions calledstates [archaic Japanese]; therefore, it appears that a(2) Coal Wholesalers and Riverboats

where coal mining was already prospering, to start coal

the Matsuura River (main river and tributaries), andperson who heard the rumors came from Fukuoka,
mining in the area.

During this period, coal was used in place of firewood.
20

making, which flourished around the Seto Inland Sea.

In the Karatsu Domain, coal mining was common along
the mined coal was loaded on riverside boat ramps.

This coal was collected at Mitsushima on the right bankof the river mouth, and was sold by coal wholesalersboth inside and outside the domain. During that time,thus, the conveyance was very efficient.

wholesalers by the Karatsu Domain; thus, these two

At the beginning of the Meiji Period, after Japan was

Karatsu coal fields.

into the country, and steam engines became widely used.

only Matsumotoya and Yoneya were approved as coal

wholesalers controlled the entirety of the mining in theRiverboat transport of the coal was arranged by thesewholesalers as well, and riverboats of 1.2 tons (2,000kin) and 2.4 tons (4,000 kin) traveled up and down the
Matsuura River.

Attached is an excerpt regarding coal from an old

drawing explaining the products of the Karatsu Domain
in the scene; this excerpt describes people mining coal,piling it on the riverbank, and then transporting it away
using riverboats.

( 3 ) T h e K a r a t s u C o a l F i e l d s o n t h e Wa v e o fModernization

At the end of the Edo Period, both demand for andoutput of Karatsu coal increased.

This was not only due to the increased demand for coalin daily life but also the extremely important change thatwas the opening of the nearby Nagasaki port. Due to theresulting increase in steamship traffic at the port, there

opened to the outside world, Western technology flowed
Steam-powered ships and trains were introduced, andthe demand for coal steadily increased. A navy base wasbuilt in Karatsu, and coal from the Karatsu coalfields
powered naval vessels.

With so many coal mines opening duringthe Meiji
Period, wealthy, powerful outsiders came to the area

to purchase coal mining rights and open new mines.
Near the end of the Edo Period, powerful clans became

conglomerates (zaibatsu), such as Mitsubishi, and went
into mining in the beginning of the Meiji Period. As

a result, the population of the Matsuura River basin
exploded, and the area became vibrant.

However, with the increased mining volume, riverboat

transport of coal approached a limit. Furthermore, railtransport was starting to spread, and steam-poweredtrains were introduced into the area. In 1905, Ochi andNishi-Karatsu were linked by rail lines, and the rivertransport of coal was quickly abandoned.

was a significant increase in the need for coal as a fuel.

Coal mining continued after World War 2, and at its

leading coal mines in Kyushu, experienced decreased

China and Singapore.

However, the Chikuho and Kasuya mines, which were

output at the same time due to technological limitations,peak, coal was sold throughout Japan and exported tosuch as those involving drainage.

The introduction of coal powered steam engines, coal

Due to this situation, the Karatsu coalfields, where

infrastructure, similar to the capillaries of the humanmining had only been conducted for a short time,
experienced many changes Some of these included theability to produce a notable volume of coal at relatively

low cost, as well as easy boat transport to destinations
such as Nagasaki and Fukuoka. Karatsu, therefore,
dominated the coal market in Nagasaki and other places.

Furthermore, the Matsuura River was a significant factor

power development, and the spread of electric power
body, all coincided with the beginning of modernization.

During such a turbulent period, the Karatsu coal fields
served as a foundation for this, and Matsuura riverboats
were essential for transportation of the product.

As we can see, the Matsuura River basin played a keyrole in the modernization of Japan.

in the development of these fields.

Most of their mines were close to the Matsuura Riverand two of its branches—Kyuragi and Tokusue Rivers.
After being mined, the coal could be placed onto

riverboats and transported to the mouth of the Matsuura
River. The transport distance was short, at only half thatfrom the Chikuho mine to the mouth of the Onga River;Works cited
Ide, Isei. A History of Coal Mining in Saga Kinkado (February
1972)
Ochimura History Compilation Committee. History of Ochimura,
Last Volume (1977)
Kizaki, Seihyo, Hizenshusanbutsuzuko, Coal and Ceramics
Overview, copy National Archives digital archives

21

【Remaining Traditional and Regional
Knowledge】

Photo: Shimauchi Risa

The Stone Weirs of the Matsuura River
Kyushu University

Teramura Jun

and other structures, such as channels, which use riverwater.

Due to this history, there are many stone weirs on the
Matsuura River.

(1) Movable and Fixed Weirs

There are numerous weirs on the Matsuura River. There
are many types of weirs, including drainage crossingsand civil engineering structures that let water through.
In Kyushu, they are often called iseki (weirs) because as
Photo 1. Reidaikyo Bridge (Misatomachi, Kumamoto Prefecture)weirs, they draw in water from wells (channels).

Modern movable weirs use power, such as motors, toraise and lower weir gates to adjust the water level.
There are many types of movable weirs with individuallyshaped gates and materials, and as appropriate, they canbe raised to draw in water and lowered during floods.

Weirs built using piles, grass, and brushwood before theearly modern times were constructed by sticking piles
into the river and placing grass, stones, or rectangulartimber between them. They were managed on a yearlybasis and were thus built during early Spring and
Photo 2. Yamada Weir (Asakura City, Fukuoka)

Since ancient times, Kyushu and its culture havecentered heavily around the use of stones, which areremoved in the Fall. Some weirs included a function
to automatically float away so as not to impede strong
floodwaters; such weirs required time-consuming

present in the many stone structures throughout thearea. Ninety percent of the stone arch bridges existingin Japan today are in Kyushu. In addition to the castles,
stone walls are extremely common in the terraced rice
fields of Kyushu.

Stonework became commonplace starting from the

Kofun Period, much of which continues to serve a
purpose in its original form in the present day.

This stonework was frequently used in rivers, including
embankment slopes, stone, and basket dikes. It was also

found in mizuhane structures to control the river, weirs,
24

Photo 3. Movable Weir

maintenance during such occasions. Although grass weirs

that cannot be confirmed because they either have been

River system in Saga Prefecture and the Kawaharazono

from concrete weirs, or cannot be approached due tocontinue to be used on the Jobaru River in the Chikugo
Weir on the Kushira River in the Kimotsuki Riversystem, very few of these have been sufficiently
managed.

covered in concrete and thus cannot be distinguishedfences built to keep animals away. Therefore, there
may be more stone dams than the confirmed number
indicated here.

Fixed weirs, however, consist of a permanent drainage

It is extremely rare for multiple stone dams to be built

Currently, most dams are built using concrete, but inDams usually take in water at a higher elevation thanframes were driven into the riverbed, and stones wereare usually built upstream from farm fields that use

crossing and let water through when they are raised.

the past, they were built using wood and stone. Wooden
inserted or piled up inside them, which ensured theon one river.

the area benefited (the location of use). Therefore, dams

structure was durable.

These weirs required a significant amount of labor toconstruct and were subject to notable external pressureduring floods, but they had the benefits of providing
stable water supply and requiring little effort tomaintain.

Nowadays, fixed weirs are no longer built by piling up
stones; most are built using concrete.

Photo 4. Kawaharazono Weir (Kanoya City, Kagoshima Prefecture)

Most new weir constructions are on major rivers and areof the movable type. On terrain with significant drops

and among mid-sized weirs, concrete fixed weirs are
relatively common. These types of weirs are frequently

used even for relatively small-scale agricultural water
intake and are thus considered most common among
these structures.

Stone weirs tend to be older than concrete ones, withmost considered to have been built between the Edo andShowa Periods. The number of stone structures has beensteadily declining as they are covered in concrete during
maintenance or are replaced with new weirs. ThroughPhoto 5. Concrete Weir

their very existence, these stone weirs have historicaland technological value.

The Matsuura River currently includes several such
weirs. Some fall within the range of large structures,
including the Daikoku and Haginoo Weirs, to smaller
valley weirs on tributary rivers.
(2) Matsuura River Weirs

We can currently confirm the existence of at least 75

stone weirs on the Matsuura River. There are others

Photo 6. Stone weir
25

them. The number and location of dams are related tonotably over time and even with early modern weir

between the dams, and the size of these structures.

tough and durable structures with masonry technology

the distance between the benefiting land, the channels

Before early modern times, water was drawn in close
to where it was to be used, by building numerous small
weirs.

However, doing so in modern times would lead tosignificant problems, in terms of damage risk andmaintenance efficiency. A trend has been noted of

consolidating multiple weirs into one location to draw inwater and distribute it into channels.

Although there is a high risk of weir damage if there are

numerous small eirs, even if one weir breaks it will notbuilding technology, many stone weirs were built asbased on the stone culture of Kyushu.

M o r e o v e r, m o s t o f t h e r i v e r b a s i n c o n s i s t s o f

sedimentary rocks, such as sandstone and mudstone;
thus, there is an abundant supply of relatively soft andeasy-to-process stones nearby.

(3) Age of Construction of Stone Weirs on the
Matsuura River

It is unclear when and by whom most stone weirs on the
Matsuura River were constructed. The names of most ofthese structures are also unclear.

lead to significant damage and the necessary functioning

There have been few new stone weir constructions sinceconsolidated weirs are large and tough structures, but ifbeen constructed at the beginning of the Showa Period.

will be divided amongst the other weirs. Suchthey are damaged, the effect is extremely widespread.

Both of these are methods to counter risk, but there is
an immense difference between the traditional thoughtof dispersing risk and the modern method of building
tough structures against assumed risk.

Therefore, based on perspectives that have varied

the end of World War II, and these are thought to have

However, we have yet to determine when the oldest weir
was built or during which period the most weirs wereconstructed.

Nevertheless, construction had already started on the
below-mentioned Daikoku Weir and the Haginoo Weir,
which are among the largest weirs on the Matsuura,

dating back to around the year 1500. Building such large

weirs required a higher level of technology compared
to building small ones; therefore, it is highly likely that

smaller stone weirs were built on the river before thistime.

Even if stone weirs are built well, they often become

damaged due to natural degradation over time; therefore,
not all of these weirs have survived.
(4) Stone Weir Shapes

Most existing stone weirs on the Matsuura River feature

various shapes that can primarily be classified into six
types, based on how the stones are stacked. Using cross-sectional shapes, the differences in stacking have beenclassified into the following methods:◆ Type methods[1] Horizontal typeThis type of dam is stacked in a step-like patternwhen observed from the side, and features rectangularstones laid horizontally. When viewed from the surface,
it appears similar to coursed masonry, but step-like
Image 1. Stone Weirs on the Matsuura River system26[1] A typical horizontally stacked dam[1] A horizontally stacked dam cross-section[2] A typical perpendicularly stacked dam[2] A perpendicularly stacked cross-section[3] A typical vertically stacked dam[3] A vertically stacked dam cross-section

stacking is not typical for stone walls.

perpendicularly. This is one of the typical methods

In weir construction, because the base of the structure

uncoursed masonry with square stone narrowing at one

can be firmly secured, they have a low center of gravity

and can withstand the intense water pressure. Although
they can be expected to dissipate the energy of the water

due to splashing on the stepped surface, the stones wear
down over time because of this.
[2] Perpendicular type

When viewed from the side, stones in these dams

are stacked to ensure that they appear to be cutof stacking masonry. Other river systems also haveend; however, on the Matsuura River, the stacking iscompleted with coursed masonry.

Most of the current hydraulic drop and bottom

protection structures are cut perpendicularly,and they
have an energy dissipating effect due to the difference inelevation. However, this difference in elevation leads to
the river-downstream from the weir-becoming deeper.

27[4] A typical arch dam[4] An arch dam cross-section[5] A typical steep slope dam[5] A steep slope dam cross-section[6] A typical gentle slope dam[6] A gentle slope dam cross-section[3] Vertical typewhen used for stone walls.

stacking in that dams of this type appear to be form a

Stones used in this masonry must be shaped with highlong ends of rectangular stones are placed in a vertical

the arch dam cross-section is symmetrically arranged.

Although this type of stacking is similar to horizontal
staircase when observed from the side, in this case, theorientation, as if piercing something from above.

It is one of the rarest types of stone-stacking methods tobe found.

[4] Arch type stacking

When observed from the side, this type of dam is curvedin an arch shape, which is also called “roll-stacking”
28

precision. Compared to horizontal and vertical stacking,[5] Steep slope typeThis method is close to both horizontal andperpendicular stacking, and the weir cross-section
surface does not feature steep slope unevenness. The

trapezoidal shape is a common structure among concrete
weirs.

- Dam with stones stacked horizontally- Dam with stones stacked perpendicularly- Stone arch dam- Stone dam with steep slope- Dam with stones stacked vertically- Stone dam with gentle slope
Image 2. Distribution of stacking methods[6] Gentle slope typeThis type of weir features a gentle slope, and compared

However, there are few perpendicularly stacked weirs

flow over the weir. Although this resembles the vertical

Haginoo Weirs, on the main stretch of the Matsuura

to other types of stacking, the shape allows water tostacking type, there is little unevenness on the surface,
thereby resembling a smooth ramp.

among the large stone weirs, such as the Daikoku andRiver. These large dams tend to be horizontally andvertically stacked.

◆ Distribution of stacking methods

Historical weirs, such as Haginoo Weir that was installedof stone weirs on the Matsuura River, accounting for 37

damage and deterioration which have resulted in the

Perpendicularly stacked weirs are the most common typeof the 75 known structures. The next most common typeof dam is the dam with a gentle slope, constituting 11of the 75 structures, among which 3 have been recently
constructed; thus, only 8 gentle slope dams feature thetraditional stacking method.

Further, among the characteristic stacking types, there
are nine horizontally stacked structures, four verticallyin the 1550s, have undergone multiple repairs forpresent-day structure. These weirs are thought to havebecome optimized through experience and innovation.

As a result of the earlier generations repairing andmaintaining the many remaining stone weirs on the
Matsuura River over a long period, the structures havebeen preserved in their original form.

stacked structures, and five arch weirs. There arenotably fewer of these structures, compared with theperpendicularly stacked weir sites.

29

The Daikoku Weir and Other Stone Dams
Nationwide
Kyushu University

Photo 1. Daikoku Weir orthoimage

30

Teramura Junwas also the border between the Karatsu and Saga

(1) History of the Daikoku Weir

The Daikoku Weir is an intake Weir created indomains.

1595 on the main section of the Matsuura River by
Shimanokamihirotaka Terasawa, the daimyo of the

Although construction started in 1595 (year 4 of the

Karatsu Domain at that time.

Bunroku Era), due to factors such as hard bedrock,the large size of the rock structures, and damage

This Weir was built on the border between thefrom frequent flooding, the Weir was not completed

Matsuuramura and Okawanomura villages, which

until nearly 40 years later in 1633 (year 10 Kanei

Sketch of the Daikoku Weir and theSurrounding Area

Gongen Mountain
Kurokamidangongen
Irrigation channel

Yoshimunedaigongen

Drainage channel

KosakaDaikoku Weir
Conduit channel

Water stop

pine
tree

slope

Temporaryreconstructed river

Daikokusama
depth 3m

Eastern enba

Channel2 depth 4m

depth 3m

water stopping stones,
and revetment masonrycollapsed (thereby
leading to large stones
being irregularly
scattered on theriverbed; this area isknown as “Nakajima.” )Channel 1
depth 3m,
Image 1. Daikoku Weir sketch (from 100 Years of Okawacho Agricultural History)31Era).

this religion. Moreover, due to the method of his

During construction, the daimyo Shimanokami

execution is considered closely related to this edict.

Terasawa was concerned about the many Weirs that

execution and the timeline of events, the monk's

had washed away and received the following advice(2) Structure of the Daikoku Weirshould build an island to divide the main riverand drawing in water from there is similar to thefrom a mountain priest named Kakyu Tashiro: “You(Nakanoshima) in two so that you can draw waterfrom the divided river.” The daimyo decided to use
this structure and thus completed the Daikoku Weir.

The method of dividing the river at Nakanoshima
Ishiibi on the Kase River in the neighboring Saga

Domain. Moreover, it includes numerous devices tocounter floods.

Moreover, because this weir was built using stone;[1] The Existence of Nakanoshima

Unfortunately, the required amount could not beleft bank (in Japan, the right and left banks use aa significant amount of this material was required.

found locally, so the stone was cut from nearby
Mount Bizan and transported to the weir site.

Shimanokamihirotaka Terasawa was originallyAt the Daikoku Weir, the river is divided on thedownstream orientation), and the diverted riverjoins the main Matsuura River again slightly
downstream.

a retainer of Nobunaga Oda. After the death of

Nobunaga, he served under Toyotomi Hideyoshi

and became the first Karatsu daimyo. He wasknowledgeable about public service projects, andanecdotes about the renewal of the downstream

section of the Matsuura River continue to be sharedin various regions even today. However, he was astrict ruler, who was known for his various public

service projects and his demanding collection ofannual tribute.

K a k y u Ta s h i r o w a s a m o n k w i t h e x t e n s i v e

Photo 2. Nakanoshimaknowledge and became a favorite of Shimanokami

Terasawa due to his wisdom. Hence, he gave HiariCastle, which was situated near the Daikoku Weir,
to the monk.

However, Kakyu, who provided advice about theweir, was executed by beheading for “having spoken
impertinently” to the daimyo.

His advice about the Daikoku Weir was initiallyindicated as the reason for his punishment, but

Kakyu had sympathized with his nephew from
Amakusa, who took shelter in his temple whileproselytizing Christianity. He was punished underthe edict of Toyotomi Hideyoshi, who banned
32

Photo 3. Intake Weir

Photo 4. Aerial photo of Ishiibi

The tributary river separated by Nakanoshima is

The land surrounded by the main stretch of thenotably smaller than the main Matsuura River;

Although in the literature, its meaning is indicatedthereby leading to further construction andriver and the diverted river is called Nakanoshima.

as “making an island,” it does not mean to “pile up

earth” in the middle of the river to make an artificial

therefore, such a sluice gate would also be smaller,management.

island. The original ground was excavated to create

There are also benefits to not directly using watertwo rivers was created. Using the original groundthat floodwater does not mix with the irrigationa branched river, and an island surrounded by the

without change led to the creation of an islandstronger than dumping earthen material would have.
[2] Drawing wWater from the Tributary River

from the diverted river for agriculture; this ensureswater, driftwood, and other matter not flowing

downstream. Reduced inflow of sediment is yet
another benefit of using this method.

There are numerous benefits related to the water

The Daikoku Weir was built during a time whenmain river.

structure was challenging. The weir features various

from the tributary river that divides the flow of the

Placing a sluice gate directly on the main section of
the river required a structure commensurate withthe size of the river. Building and managing such a

constructing such a strong, long, and massive
methods of dispersing the force of the river (e.g., inflood situations), to readily deliver the blessings ofthe river to the local people.

structure, which can easily become damaged, would
be burdensome.

33

Image 2. Dujiang Weir (tracing)

Nakanoshima, but the structure is more complicated,compared with that of Daikoku Weir. Ishiibi's tributary
river diverted by Nakanoshima features elephanttrunks and turtle stones, which are devices used toreduce the power of the river's current.

The water drawn at Ishiibi flows from the highest
point, of the low-lying area of Saga, by way of the
Drawing 1. Ishiibi (from the Sodoyoshu)(3) The Daikoku Weir and Similar Historical Weirs

Castle and surrounding agricultural fields.

The Daikoku Weir incorporates various traditional

Although the Ishiibi was built during 1615–1623,

creation of Nakanoshima. However, this technology

remained incomplete until 1633 due to difficulties

technologies, such as masonry stacking and thewas not only used in the construction of this structure.
Ishiibi is situated near the Daikoku Weir on the
Kase River in Saga. Ichinoi weir is a weir on the

Katsura River in Arashiyama, Kyoto. If we trace thesestructures to their origins, the Dujiang Weir in China

has a similar structure, regardless of the different size
and age.

construction started on the Daikoku Weir in 1595 but
related to building the structure. The Ishiibi was built
within this period, and although it is unclear whether
Kakyu referenced its structure, these two weirs arepresumed to be related.
[2] Ichinoi Weir

The history of the Ichinoi Weir, located on the

Katsura River in Kyoto where the river emerges from

[1] Ishiibi

the Hozukyo Gorge, extends to ancient times. The

chief retainer of the Saga Domain, during the Genwa

as the Kadono Ooi, which was built around the late

Ishiibi was built by Narutomi Hyogo Shigeyasu, aPeriod (1615–1623).

Similar to the Daikoku Weir, Ishiibi is a stone weirthat draws in water from a tributary river divided by a34

Tafuse River and is eventually used at both Saga

origins of the weir are considered to extend as far

5th century. Given its appearance has transformed

since then, we're able to see a variety of weirs in
Arashiyama. The rich natural beauty of the various

seasons reflected on the surface of its waters is thereason it is considered to be one of the best scenic

divert water with a Nakanoshima and draw water fromspots in Japan.

the diverted river branch.

The Ichinoi Weir currently has fixed and movable

The Li Clan that built the Dujiang Weir were

However, until the current concrete weir was

Moreover, it has been claimed that the Hata ( 奏 )parts and is perpendicular to the river current.

completed in 1952, the structure consisted of many

piles driven into the river and erected at an angle that
set it against the river flow.

Although its structure differs from the Daikoku
and Ishiibi Weirs, the Ichinoi Weir also has a

Nakanoshima, and it takes in irrigation water from adiverted river section.
[3] Dujiang Weir

The Dujiang Weir is an intake weir in Sichuanprovincial constables during the Qin ( 奏 ) Dynasty.
Clan that built the Kadono Ooi, which is the prototype

for the Ichino Weir, came from China. Hata ( 波 多 )is also a place name in the Matsuura River Basin, andone theory has it that they had some involvement with
the immigrant Hata ( 奏 ) Clan, similar to the case in

Kyoto. Although the locations, periods, shapes, andbackgrounds of these weirs completely differ, theirimportance can be gauged in terms of the technologythat has been continuously used across various
periods.

Province, China. Built in 3 B.C., with over 2,000 yearsof history, its original form has been maintained.

Similar to Daikoku, Ishiibi, and Ichinoi Weirs, theDujiang Weir also has a Nakanoshima and draws inwater from a diverted river branch.

Approximately 2,000 years ago, the water intake
method that was a prototype for the Daikoku Weir

had already been created. Considering the ages of theDujiang Weir(2,000 years old), the Ichinoi Weir (1,500

years old), and the Ishiibi and Daikoku Weirs (400years old), it is obvious these weirs have withstoodthe effects of time and thus attest to the great
durability and effectiveness of these structures, which

Works citedHometowns and Rivers Horita, Kaneo (1997)
100 Years of Okawacho Agricultural History Miyamoto, Iwami Chuoh
Publishing Co.
The History off Matsuura Yoshimura, Shigesaburo, Matsuura
Publishing Committee (1956)
Sodoyoshu Nanbu, Nagatsune (1834)
The Ichinoi Weir at Saga Arashiyama, which Irrigates Rakusai, which
Preserves Landscape and Natural Features Kyoto Prefecture
Agriculture, Forestry and Fisheries Division, Agriculture
Department, Maintenance Section (March 2006)

Photo 5. Ichinoi Weir

35

Haginoo Weir and Umankashira
Kyushu University(1) Haginoo Weir, Umankashira, and Oide

Similar to the Daikoku Weir, Old Matsuura-cho
momonokawa has the stone Haginoo Weir as well as a

Teramura Juncelebrated as a god of water at the Shiraishi Shrine in
the old Miyakicho.

structure called Umankashira which was built to carry

The main stretch of a large river should theoretically

opposite bank of the Matsuura River.

the river was running very high, drawing irrigation

Oide irrigation water drawn from Haginoo Weir to the

These structures, which were built by Narutomi
Hyogo Shigeyasu, were considered by the chiefretainers of the Saga Domain to be the “gods of flood
control and irrigation.”

Narutomi Hyogo worked on numerous flood control

and irrigation projects throughout the Saga Domain,
beginning with the Ishiibi on the Kase River. Having

built the water management system on the Saga

Plains, his achievements are praised throughout theprefecture, even today. In addition to town names

including Hyogomachi and Shigeyasumachi, he is

be the lowest point in the area. Therefore, even ifwater from the main part of the river would still be an
extremely difficult task. When drawing irrigation water,

it was necessary to do so upstream from the location
one intended to use the water in. However, the highwater-flow on the main stretch of a river also indicatesthat there are powerful floods-water intake structures,such as weirs, can also have a significant impact inreducing them. Therefore, notable effort and a highlevel of technology are required to draw water fromthe main part of a river.

The irrigation water taken in by the Haginoo Weir isdelivered to the agricultural fields of the Momonokawa
area on the opposite bank downstream by passing

through the Oide irrigation canal and throughUmankashira.

Umankashira

Haginoo

Image 1. Haginoo Weir, Umankashira, and Oide irrigation water level
diagram from a Geospatial Information Authority of Japan map
36

Drawing 1. The Haginoo Weir and Umankashira in the Sodoyoshu

(2) Haginoo Weir

The Haginoo Weir was first built in 1550 (year 19of the Tenmon Era), is a stone weir located on theflowing into the water channel by promoting sedimentsubsidence.

rightside of the riverbank, and has a sluice gate

Moreover, there is an open levee upstream from theis situated in the middle of a channel to further

the water level rises, the floodwater that backflows

included as well. For water intake, the sluice gate

take in irrigation water and has a spillway in caseof high water levels. Although this weir is similar to

Haginoo spillway; therefore, when a flood occurs andfrom here and overflows can return to the river.

the Daikoku Weir and Ishiibi, it is slightly different

Although the surface of the Haginoo Weir is now

main river. Thisprevents excessive sediment fromstacked quarried stone, and this masonry can bebecause there is a clear sluice gate situated on the

covered in concrete, it was originally built fromobserved even in the present day.
(3) Umankashira

Umankashira was built in 1611 (year 16 of the KeichoEra) by Narutomi Hyogo Shigeyasu.

Although the irrigation water drawn in by the Haginoo

Weir initially flows to the right bank of the Matsuura

River, it eventually flows over to the left bank bymeans of a channel that crosses the river. Some type
Sluice gate(Ishiibi)

Open
levee

of structure is required for a channel to cross a river,and the greater the volume of water, the tougher the

Shakeout

Sluice gate (Ishiibi)

Spillway downstream

HaginooWeir

Large stones stacked

Haginoo Weir

Photo 1. Haginoo Weir structure37

OutletUmankashiraPhoto 3. Tsujunkyo Bridge (Yamatocho, Kumamoto Prefecture)

Inlet
Matsuura River

Photo 4. A wooden water pipe spanning a stream that runs aroundfields in Akizuki, a historic building preservation district (Asakura
City, Fukuoka Prefecture)

Clockwise
Photo 2. Umankashira orthoimage

structure must be. Various devices have existed foruses the reverse siphon hydraulic principle for the

For example, for the Tsujunkyo Bridge in Yamatocho,

Umankashira draws water from a sinkhole on the rightas a large, stone arch bridge to ensure that water pipes

pipe called an oketoi. The pipe crosses the bed ofthis purpose since ancient times.

Kamimashiki District, Kumamoto Prefecture was built
could cross the Gorogataki River. Moreover, streams

and channels could be laid across using wood orbamboo pipes.

Using these methods to transport water, Umankashira
38

Image 2. Sketch of Umankashirawater channel to cross a river.

bank of the Matsuura River to a cylindrical water
the Matsuura River and gushes from an outlet on the
opposite (left) bank.

These pipes are created using wood, by overlaying

several pipes resembling cylinders on each other. Even

if there was warping due to floods or other causes,

technology, such as precise measurements.

easily corroded and had to be replaced each year,

Moreover, according to the Sodoyoshu, a similarpine logs or cube-shaped pipes, thus the original

with the one on the Matsuura River called Ouma andsuch a structure did not easily leak. Although oketoi
improved results were not obtained by using stronger
oketoi pipes were used again. They remained in use
for 300 years, until they were replaced by concrete

Umankashira was also included on the Arita River,the one on the Arita River called Kouma.

pipes in 1928.

The Umankashira channel splits into three upstream

from the sinkhole, with one of the channels leading

to the Matsuura River right bank and the other two
leading to the left bank through the Umankashira. It

also has two sluice pipes, because if there were only

one pipe and it were too big, it would collapse underpressure. If there are two pipes and one breaks, theother pipe can be used, and the positioning of thechannel after the siphon pipe outlet varies.

As observed from upstream, the left bank outlet is low,

Photo 5. Umankashira outlet, divided into upper and lower channels.

and the outlet on the right is high. The water flowing
from the right outlet irrigates the farm fields nearby

and eventually flows into the left channel downstream.

The left bank channel accepts drainage from the
nearby rice paddies while irrigating the Momonokawa
farm fields downstream.

A nogoshi is included at the outlet of the channel on
the left bank, through which excess water is dropped
into the Matsuura River.

A nogoshi is an overflow dike where a part of the

Photo 6. Umankashira nogoshi. The overflow portion has concrete block
pitching to resist damage.

channel ridge or another point is lowered, and itis hardened using various methods, such as stone

pitching, to ensure that floodwaters and irrigationwater can overflow at a specific point. These areseen throughout Saga Prefecture, such as in the flood
control sites on the Jobaru River and at the Hamaguri

waterworks, where it is used in the irrigation water
channel.

Reverse siphons like those at Umankashira are also

called Fusekoshi, and although they are used in thechannel connecting Tatsumiyosui and Kenrokuen in

Kanazawa City, Ishikawa Prefecture and the Tsujunkyo
Bridge mentioned above, these are public service

projects that would be difficult to build without sluice

pipes that did not leak or with the use of specialized

Photo 7. Jobaru River nogoshi. Part of the embankment is lowered sothat flood water flows from the chosen location.

Works cited
Sodoyoshu Nanbu, Nagatsune (1834)
Umankashira local information board
Imari as Seen in Drawings and Maps Imari Municipal History
Compilation Office (2007)

39

The Floodplain Open Levees of the Matsuura
River
Kyushu University

Most of the Matsuura River flows through aclassified into two types.

rapids in the upstream stretches of its tributaries,

Currently, the term “discontinuous levee” isgradual slope, with a gentle river current.

embankment stretching upstream and downstream,

mountainous region. Although there are many
the main river and the major tributaries have a very

Wide rivers narrow when they pass throughvalleys, and when floods occur, the riverbanks
often overflow upstream from the valley. In theused for open levees. Compared to a continuous
as is commonly noted on ordinary rivers,

embankments that purposefully do not continue forvarious reasons are called discontinuous levees.

plains of these mountainous areas, the Matsuura

The Shingendutsumi built by Shingen Takeda onthat frequently overflow are called floodplains, andlevee and is considered the first of such structures.

River has also frequently overflowed. These plains
any damage incurred by people due to flooding(including fatalities and damage to homes and otherproperty, such as farms) is called flood damage.

Floodplains are relatively flat, and water is readily
available; therefore, they are favorable locations forlarge farms, and since ancient times, people havebeen converting them into farmland.

On the Matsuura River, these plains have beendeveloped into rice paddies. However, heavy
rains causing flooding on the floodplains damage

agricultural land and crops. Moreover, since ancient
times, humans have taken the utmost effort to

the Kamanashi River is a well-known type of open
Shingen Takeda, however, did not use this term.

The first time open levees appeared in the literature
was during the Meiji Period, when it was used bya newspaper reporter named Morotomo Nishi in

his commentary titled Flood Control Theory. In his
work, he referred to a special type of embankmenton the Joganji River as a kasumi-gatatei (literally

a “mist-shaped embankment” ). Following this,perhaps due to frequent disasters occurring acrossJapan, politicians and civil engineers began using
the term “kasumi-tei’ (open levee) in the National
Diet and other venues, thus leading to the term
becoming widely used.

prevent flood damage.

Both the Joganji and Kamanashi rivers are striking

One such example being the open levee, atype of alluvial terrain formed when rivers with a

traditional flood control technology which isrepresentative of the Matsuura River.

examples of alluvial fan rivers. Alluvial fans are ahigh volume of sediment from mountainous areas
exit the mountains, and deposit the sedimentin a fan-like formation. Alluvial fan rivers are(1) The Two Types of Open Levees

characterized by having a steep gradient.

flood control technology in Japan and are broadly

However, the Matsuura River has a gentle slope

Open levees are a particularly well-known traditional

40

Teramura Jun, Kitamura Keitaacross its basin, thus the characteristics of both the

For example, if one does not hold the end of alevees (open levees) are observed across Japan,

force, the hose will wildly swing around. A similarriver and terrain notably differ. Yet, discontinuous
including on rivers with gentle slopes, such as the

Matsuura. The Toyo River in Aichi Prefecture, theKumozu River in Mie Prefecture, and the GokaseRiver in Miyazaki Prefecture are well-known forthese structures.

The same term “open levee” is also used for
traditional flood control facilities on rivers withcompletely different characteristics because theembankments are discontinuous. If the river has

hose or showerhead and turns on the water at full
phenomenon occurs in nature with alluvial fan
rivers.

In alluvial fans, a large volume of sediment

washes down from the mountains. However,
because there is also a large volume of water anda slope, waterways are easily formed, and springwater wells up; these are the notable benefits ofdeveloping agricultural land at these locations. The
Kaga Domain, one of the many tozama (outside)different characteristics, the facility purpose, origins,

daimyo in the Edo Period, possessed an expansive

fan open levee and a floodplain open levee are

the Ishikawa and Toyama prefectures, but most ofform, and functions will also differ. An alluvial
completely different structures.

Here, I will primarily use the term “alluvial fan open

agricultural land called Kaga Hyakumangoku inthis area featured rice paddies developed from analluvial fan.

levee” for levees on rivers with swift currents, such

Alluvial fan rivers in their natural state do not havefor structures on floodplains with gentle slopes.

flood control is required to control the course. For

as alluvial fan rivers, and “floodplain open levees”◆ Alluvial fan open levees

At levees on alluvial fans, short embankments arebuilt in succession for multiple layers.

On alluvial fan rivers, these are made using large
rocks, gravel, and sand. In this case, the river iswide and most of the width is covered by a gravel

riverbed. In such a wide river, the current flows
in various directions. Therefore, large floods often

lead to changes in the location of these rivers.

a fixed course and overflow their banks; therefore,

this reason, traditional flood control structures built
on alluvial fan rivers mostly in the Edo Period are
alluvial fan open levees.

To control the river course on an alluvial fan, first,

the “neck” of the river must be controlled at the
top of the fan to determine the river direction. Spurdikes, such as megaliths and large stone piles, areplaced to set the direction where the dike meetsthe river. At most such sites, the river is pushed

to the edges of the alluvial fan, because it enables-集落
Clusters-本堤
Main
levee )
( 霞堤
-控堤
Auxiliary levee-用水路・旧河道
Irrigation channels, old river courseNo.
1 levee
一番堤

二番堤
No.
2 levee
Image 1. Tedori River alluvial fan and open levees

三番堤No.
3 levee41

us to find a good location for drawing water. On

levees. Their locations and sizes transformed basedside of the alluvial fan, and the old river course

Joganji River, they became larger with each passing

the Tedori River, the river was fixed on the souththat remained in a webbed pattern in the alluvial

plain was used to allow irrigation channels for theon the level of importance and the period. On the
period.

development of rice paddies.

Alluvial fan open levees had two secondary

Next, a wide river was narrowed to some extent andbetween embankments and reducing the power of

fixed at a width that allows for the river to flow. In

places where the river did not flow in the intended

direction, short embankments were installed like fish
scales in a series. These embankments were built tofunctions; draining tributaries and local run-off fromfloods by planting forest buffer strips of bamboo,pine, or other trees in between the overlapping
areas.

ensure that when the river current hit, it bounced

Furthermore, alluvial fans have steep slopes, andof open levees.

were short, floodwaters from the discontinuous parts

back. These series of embankments marked the start

Currents on alluvial fan rivers are powerfuland contain a high volume of sediment, thus
making them very destructive. Therefore, manyeven if the overlapping portions of alluvial fan leveesof the embankment would not overflow into theembankments. Therefore, alluvial fan open levees
are open levees with:embankments were destroyed. However, during that- Fixed channels

nature and built embankments to ensure that even

- Drainage of local run-off

period, people were familiar with the great power of
if one were destroyed, the water would be stopped

by the next structure and the overflow would flow
back into the river. This is why several small,discontinuous levees are built in succession.

The series of alluvial fan open levees are called,
starting from upstream, No. 1 levee, No. 2 levee,- Overflow return to the river- Reduced backflow

A long time ago, when there were floods and watercollected within the open levee, fish and driftwood

would gather there. This created areas which wereused to catch fish and gather firewood.

and No. 3 levee. The embankments built in frontof the clusters inside the levees are called auxiliary

Drainage of local run-off
Branch inflow

Fixed channels
Spur dikes where floodwaters flow backReduced backflow
No overflow even during
backflow

Overflow return to the river
Even if the levee is breached, theoverflow is stopped at the next levee
Image 2. Alluvial fan open levee (created by: Teramura and Shimatani)

42

Floodplain open levee openings (the discontinuouspart) were in the farthest downstream point
where the embankments overlapped. When aflood occurred, floodwaters flowing from here

would backflow into the floodplain open levee andaccumulate there. Moreover, since this opening wasat the farthest point downstream, it was unnecessary

to use pumps or other equipment for drainage.
This area would naturally drain as the water level
reduced.
Photo.1

Pine trees in Arakawa

In some cases, because the mechanisms for handling◆ Floodplain open levees

the flow of floodwaters are extremely complex,

form from the alluvial fan open levees, whichfunctionality of these levees and have, therefore,

Floodplain open levees significantly differed infeatured a series of short embankments—the spacein the overlapping areas of the embankments was
extensive.

Moreover, certain areas of floodplain open levees

we lack sufficient knowledge for explaining thediscussed their functions.

We will later explain the flow validation forfloodplain open levees.

were often adjacent to river terraces and mountains,

These levees serve a role similar to very small damsin the open levees. If there was no suitable terrain,levee.

thus the builders found methods to limit the spacesuch as river terraces, embankments were created tothat collect floodwater by flowing it into an open

fulfill such a role.

Moreover, on floodplain rivers, because flood control

The basic function of this type of levee was fordifficult, if the water level is high on the main riverfloodwaters to accumulate in the space within the
open levee.

at the confluence points with tributaries is notably
due to flooding and the level of the tributary is nothigher, floodwaters cannot drain from this branch

to the main stretch of river. If this occurs and theRiver terrace slightly
elevated area

Rice paddy
Local run-off
pond

Embankment unlikely tocollapse even if there is an
overflow

Tributary inflow

Anti-flood pond created bybackflow

Forest buffer strip
Image 3. Floodplain open levee (created by: Teramura and Shimatani)

43

water overflows within the embankment, it is calledcapacity and on an individual level, there are still

often built at confluence points with tributaries;

current floodplain open levees across the river basin.

a levee internal flood. Floodplain open levees are
therefore, they have a function to contain suchfloods. There are often rice paddies within theselevees, thus it is thought that floodwaters bring

These rice paddies occupy a total of 140 ha and canretain up to 2.8 million m3 of floodwater.

fertile soil to this agricultural land. Moreover,This is three times the water retention capacity ofdownstream; another benefit is that because thisbuilt on the nearby Rokkaku River.

floodwaters that flow into farming areas reflux fromcurrent is slow, it does not damage farmlands by

the Mutabe dry retention basin that was recently

destroying rice plants or ridges between the fields.

The Mutabe dry retention basin cost approximately

Furthermore, planting bamboo groves or trees nearfloodplain open levee water retention function has athe opening serves to further reduce the current,

which can prevent driftwood and trash from flowing

11.1 billion yen; therefore, the Matsuura Riverpotential flood control value of 34.5 billion yen.

into agricultural fields.

The level of a river's flood control safety is not

In addition to catching fish and driftwood similar tothere are various other superior points in dams andalluvial fan open levees, when the rice plants wereinundated and the water receded, in various regions
people found methods to go into the rice paddies toshake off the water and mud.

Therefore, floodplain open levees serve thefollowing functions:- Floodwater retention with anti-flood ponds- Levee internal flood retention- Preservation and fertilization of agricultural lands
Moreover, they provide various secondary effects.
(2) Matsuura River open levees

The Matsuura River features a gentle slope andmany relatively small, basin-shaped flat areas

indicated merely by its water storage capacity;
floodplain open levees.

Matsuura River basin floodplain open levees
are characterized by mostly being located at theconfluences with tributary rivers, and in manycases are located in mountainous areas. In thiscase, mountainous areas indicate that terraces
and mountains are adjacent to the river, andthat the original terrain can be used in place ofembankments. They, therefore, play the role ofextremely firm embankments. Furthermore, because
tributary river confluence points are the joining

point for rivers, embankments will be discontinuousand naturally assume the shape of floodplain open
levees. The Matsuura River floodplain open levees
were built using natural terrain.

surrounded by mountains.

Floodwaters backflow into the floodplain open

The river basin has several open levees and spots

inundated with water. However, even in the present

with discontinuous embankments.

levees on the Matsuura River which are frequently
day, there are rice paddies in most of these levees.

These open levees are built on the gentle slopes

Even if this type of levee floods, if the water level

floodplain open levees.

drain, and thus the rice plants will not be inof flat lands therefore, they can be considered

These levees do not have notable water retention
44

some rice paddies with functions similar to theon the main river is reduced, the levee will naturallywater for extensive periods. Even if the plants arecompletely submerged, if the period of submersion

River mouth

Karatsu Bay

Tokusue River
Pools of water

Kyuragi River

Azamenose
OkawanoMomonokawa
Matsuura River

Haginoo Dam

Image 4. Floodplain open levees currently existing in the Matsuura River basin

is 48 hours or less, they will not die. In the casethat.

If the rice plants are in the blooming stage, theThe floodplain open levee of the Matsuura River isa regional asset embodying regional knowledge built
over many years.

damage will be significant; however, during otherseasons, damage to the rice paddies in floodplain
open levees is uncommon.

These levees on the Matsuura River serve as

an optimal flood-control technology to use thefloodplain while ensuring the least damage to
agricultural lands.

Works cited
Teramura, Jun; Okuma, Takashi. Research into the Function andClassifications of Discontinuous Embankments. A compilation of

The date when the Matsuura River floodplain open
levee was built has yet to be determined, but it isconsidered to have come to its current form basedon years of experience dating back to the Edo
Period or earlier.

civil engineering history research papers (2007) 26.0: 73-83
Okuma, Takashi. An Inquiry into the Functions and Etymology ofOpen Levees, a compilation of Japanese civil engineering history
research presentations (1987) 7.0:259-266
2017 Japan Society of Civil Engineers' Design Award, Japan
Society of Civil Engineers

45

The floodplain open levees of Okawano
Kyushu University

Kitamura Keita

Photo 5

Jono River

Photo 2
Matsuura River

Photo 1. The floodplain open levees of Okawano(1) Okawano

rice paddies are surrounded on four sides by thePrefecture is a farming village situated approximately

river terraces, and part of the ring levee.

Okawa-cho-okawano in Imari City in Saga
25 kms upstream from the mouth of the Matsuura

River. This area features the floodplain open levees
explained in the preceding section.

The Okawano levees are at the confluence of the
Matsuura and Jono rivers. Therefore, if the waterlevel on the main river increases, approximately

16 ha of rice paddies from the opening of thefloodplain open levees will become flooded. These
46

embankments on the main stretch of the Jono River,(2) Ring Levee Village

There is a village surrounded by an approximately
2.5 m ring levee at the same elevation as the ricepaddies. A ring levee is a bank surrounding thisvillage, with a long history. Based on the records,
the area was established as a village in the earlymodern times, with the ring levee being built at
the same time. However, the first levee was shorterPhoto 2. Ring levee village

than the current levee and was thus easily breached.

Therefore, this ring levee frequently collapsed

during floods, and homes inside were immersed.
The structure was raised and strengthened eachtime a flood occurred. The current form of the leveeGreat flood monument

was built in 1993, three years after the 1990 flood
damage.

There is a record of past flood damage in the ring

(September 1948)

Utility pole record(July 1990)

levee village (Photo 3). The great flood monument

was erected after the September 1948 flood, and thefloodwater level is inscribed on it. Moreover, the
1.6 m water level from the 1990 flood is recordedon the utility pole beside the monument. These
records convey the history of flood damage to future

Photo 3. Record of the floodwaters

generations.

Water level peak

Record heavy rains of 100 ml an hour occurred in
the Matsuura River basin on August 27 and 28,

2019. During this storm, floodwaters flowed into
the Okawano rice paddies from the opening of thefloodplain open levees. This was the most severe

Water level(m)(3) August 2019 Heavy Rains

About 40 hours

flood since the heavy rains of 1990, and one of thelargest such events to date.

I conducted local studies of this flood and simulated

Image 1. Changes over time in Jono River water levels

47

Water level(m)Photo 4. Rice plants after being covered in water

Direct distance from the water level metermeasurement location(m)Image2. Relation between the highest water level on the Jono River andthe water level traces in the rice paddies

recreations to study the floodplain open levee
flooding and the flood control effects.

(4) Local Study of Okawano Directly Following(5) Interview Surveys

I interviewed farmers living in the ring levee village

in Okawano. The farmers noted that the rice
harvest was not severely damaged, considering thelevel of flooding. In rice paddies in the past, therice plants were not destroyed by flooding and only

flood waste, such as driftwood, was carried in with a

low amount of sediment. This may be caused by thethe Heavy Rains

fact that the geology of the floodplain is mudstone—

are presented in the image. The normal water

washed away by rain. When the rains subside andReadings of water level gauges on the Jono Riverlevel is approximately 13 m, with the highest floodlevel being 19.05 m recorded at 8:30 am on August28, 2019. The water level returned to normal
approximately 40 hours after it had increased (Image
1).

The relation between the highest water level on the

Jono River and the water level traces in the ricepaddies is presented in the image. During this flood,

the mud that had covered the plants was eventually
the water level lowers, driftwood is removed. The
location where the driftwood accumulates is typically

pre-determined. The primary concern is regarding
disease. Immersion in water (such as when a flood

occurs) washes off the disinfectant, thereby leaving
plants susceptible to disease. Moreover, sinceancient times, it is said that floods increase thefertility of the soil, thus providing bigger harvests.

at least one meter of flooding was noted across

A close relationship was noted between the daily

consistent with the highest water level on the Jonorepresentative example of this is the Japanese dacethe rice paddies. This water level trace was mostlyRiver, regardless of the direct distance from thewater level meter measurement location.

life of the local people and the Matsuura River. A
locally called the ida. People are so familiar withthis fish that it was featured in the Kurokamiyama

The condition of the rice plants is shown in theimage (Image 2).

Although the rice plants were covered in water, few

plants were knocked down, and none were buried in
sediment. Only those near the floodplain open levee

opening were knocked down, along with the flood

protection forest. A large amount of flood waste,
including driftwood, was noted in this forest.
48

Photo 5. Floodplain open levee opening after a flood

be noted that the level at the floodplain open levee
opening is constant. Furthermore, the floodwatersthat pooled in the rice paddies naturally flow fromthe opening as the level on the main river reduces.
As a result, the rice plants were immersed for
between 8 to 40 hours.

With flooding from floodplain open levees, thepossibility of rice plants being knocked down or
Photo 6. Ida (Japanese dace) credit: Yuichi Kano (ffishu.asia)
Software

iRIC version3.0

SolverTerrain data

Nays2DH
Geospatial Information Authority of Japanbasic map information

Digital elevation model
5m meshWater level data
Ministry of Land, Infrastructure, Transport
and Tourism water level observatory August

Flow rate data
Shape format

2019 heavy rain measurement data (Kawanishi
bridge, Wadayama bridge)
Calculated by the Kawanishi bridge H-Q
method5m square mesh

Table 1. Software and data used

dying due to immersion for long periods is low,

thereby suggesting that damage to floodplains was
minimized.

The peak time cross-section flow rate over 40 m
downstream from the Okawano floodplain open

levee is presented in the image. The orange line

indicates when 16 ha of rice paddy flooding fromthe levee is allowed, as is currently the case,whereas the blue line indicates when this flooding iscontrolled by closing the levee opening. Comparing
these two lines with flooding from the floodplain

open levee, although the flow volume decreased
great snake legend, and the area around Okawano

was well-known for ida. Moreover, after a flood
occurred and the waters receded, people collected
and consumed the koi, crucian carp, and catfish left
behind.

until arriving at peak flow volume—the maximum
amount of water flow during a flood—after thispeak, the volume increased. In addition to a flow

volume peak cut of 5.3 m 3 /sec., the peak wasdelayed by 10 minutes.

When using normal anti-flood ponds, drainage is(6) Flood Simulated Re-creations

I conducted a simulated recreation of the floods
during the August 2019 heavy rains for the

Okawano floodplain open levee. The software anddata I used are presented in Table 1.

I also provide a flow speed vector image showing
the volume and direction of the flow at flood

peak time as well as a contour diagram showing
floodwater levels in different colors. If the flow
velocities at various locations are compared, it canbe noted that the velocity in the rice paddies is
extremely gentle, compared to that of the main
stretch of river. This is considered to be caused by
the inflow from the backflow out of the downstream
opening. Moreover, by observing water levels, it can

Image3. Okawano flow rate vector image and water level contour
image (flow volume peak time)49

Main river
Location No.

Floodplain

Flow rate Water level(m/sec)(m)

Location No.

Flow rate Water level(m/sec)(m)

Table 2. Location flow rate and water level (at main river flow volume peak)

Cross-section flow rate (m3/s)

During flood (15.0ha)
No flood

handed down locally. As a result, homes are notbuilt in low-lying, flood prone areas, and locals are

sure to strengthen ring levees. Moreover, during
the recent flood disaster, harm to people, flood
damage to houses, and damage to rice crop yields

were largely controlled. This levee and the use of its
Reduction

Increasesurrounding land involved structures that reduced
the effects of disasters, thereby fusing modern

advanced levee building technology with the wisdom
Time lapsed (min)shared by ancestors since the early modern times.

Image 4. The peak time cross-section flow rate over time 40m
downstream from the Okawano floodplain open levee

not conducted using pumps or sluice pipes between
floods, and the floodwaters are retained. The flood

flow volume cut is thus maintained. In comparison,
the floodwaters retained in the Okawano floodplain
open levee outflow naturally. Although the flow rate
peak cut volume is reduced as a result, a unique
phenomenon called a flow rate peak delay occurred.
(7) Summary

The floodplain open levee at Okawano had astructure that simultaneously reduced overflow flood
damage to rice paddies and the effects of thesedisasters. However, these were ineffective becauseof their structures. In Okawano, flood damage

experience since the early modern times has been
50

Works cited
Okawacho Onkochishinkai. Okawacho (1978)
Matsuura History Discussion Committee. Matsurokoku No. 60

51

The Cross-levees of Ono
Kyushu University

Teramura Jun

Photo 1. Ono cross-levee (photo: Ginji Oishi)

Photo 2. 1964 aerial photo (Geospatial Information Authority of Japan aerial photo MKU643-C10-14 processing)52

The remnants of a floodplain open levee can be foundin Ochichoono in Karatsu City. Observing this crosslevee, we can see knowledge of land use that conforms
to the river shape.

(1) The Ono area

The Ono area has an extensive history spanning over

400 years. One theory indicates that the Onuma area

during the Heian Period Wamyosho is the Ono areain the present day. Moreover, the Marukuma Shrine isconsidered to have been in its current location since
the Muromachi Period.

(2) Cross-levees and Villages

By observing old aerial photographs of the Matsuura
River, it can be noted that the flow of the river has

been altered. Until around 1980, the river around thisarea meandered notably around the current crosslevee.

Embankments were built in line with this meandering
section, and the embankment that is the current cross-levee continues on this extension. The end of thislevee continues to the mountains, and its embankmentalong the riverbank is discontinuous. This cross-levee
used to be a floodplain open levee. Around 1980, thismeandering portion of the river disappeared, and thislevee was closed. However, because only the crosslevee was sturdy, this remained as a river structure.

The function of using backflow to allow floodwatersfrom the opening to backflow is similar to the method

used at Okawano and other places. Moreover, placing

Drawing 1. Higashi-Matsuura District Town/Village Map (Section A) Ono
Village (taken from Saga Prefectural Library Digital Archives publicdomain content)

floods to prevent flood overflow, and materials werestored in sheds in the village.

Even if a flood occurred, most homes were in high,hilly places and were thus not affected. However, one
store was frequently flooded.

In the 1881 map, there is a house at the spot where
this store is located. Similar to the positions of otherhouses, sufficient land was used to ensure that homes
were not affected.

open levees on meandering sections of rivers iscommon in floodplain areas, as noted on the Toyo
River in Aichi Prefecture yoroi-tei (now called kasumi-

tei, or open levee, but formerly called yoroi-tei)
and the torinohakasane on the Shiota River in Saga
Prefecture.

Observing the 1881 (year 14 of the Meiji Period)
Higashi-Matsuura District Town/Village Map (SectionA) Ono Village, not only is the cross-levee visible but
also the positions of villages have remained mostly thesame.

Using the cross-levee and the road cross at thefloodwall gate, square lumber was inserted during

Photo 3. Floodwall gate with a prefectural road (photo: Naoto Tanaka)

Works cited
Ochicho History, Ochicho History Edition Committee , ed. (1971)

53

The funagata yashiki of the Hidari-Ikisa River
Kyushu University

Teramura Jun

Most of the Matsuura River basin is composed of

By building stone walls, slightly elevated ground, anddownstream and easternmost portions are made offloodwaters flow) from residential areas, these structures

sedimentary mudstone and sandstone, but the farthest
granite and granodiorite. Rivers in such areas have aheavy outflow of sediment and alluvial fans form easily;

embankments upstream (the direction toward which
protect houses from floods.

therefore, they are shallow in nature. The right Ikisa

On rivers with steep slopes situated on floodplains

is situated on a granite belt. In particular, the left Ikisa

floods flow from upstream, but they do not backflow

River, a downstream tributary of the Matsuura River,River tributary forms an alluvial fan. Rivers with alluvial

fans are prone to flooding and contain a high volumeof sediment; this type of terrain tends to damage
agricultural fields and residential areas. On such rivers,

the methods used to protect these areas from flood

damage are different, compared with the methods used
for rivers with a gentle slope (e.g., Matsuura River).

(such as those in alluvial fans), on floodplains, powerfulfrom downstream. Therefore, if protective measures
are only adopted in the direction facing the flow of
the flood, there is no need to take protective measures

downstream. With funagata yashiki, stone walls andother structures are built facing upstream. Floods havea powerful flow; therefore, such structures have an edge
facing upstream. The term funagata yashiki is derived

from the fact that these edges resemble the bow of a(1) Funagata yashiki

ship.

are also a method of controlling alluvial fan flooding.

(2) Hidari-Ikisa River funagata yashiki

flood control method called the funagata yashiki (literally

Dam and Mikaerinotaki waterfall, and because most of

The alluvial fan open levees presented on page 41
However, on the left Ikisa River, a traditional Japanese“boat-shaped Site” ) can be noted. The Oi River in
Shizuoka Prefecture is well-known for these structures.

Upstream on the Hidari-Ikisa River, we see the Ikisa
the basin is in a mountainous area, the 1.5 km farthest
downstream stretch that merges with the Ikisa River isa rapid river on an alluvial fan
plain.

Stone wall

At the farthest downstream

Elevated area

area, approximately 500 m

Treesfrom the confluence, we see a
funagata yashiki.
There are currently fiveconfirmed funagata yashiki on

the Hidari-Ikisa River. The

③
④

①
⑤

②

most upstream among themis a mound-like elevated areasurrounded by a stone wall.

There are trees on the mound,with a small shrine in the
middle of this little forest. In
Photo 1. Hidari-Ikisa River funagata yashiki54

the past, a local meeting placewas situated in these woods, thus making it an important
location for the local people. Houses are on the otherside of the mound surrounded by a stone wall, and there
is an entrance/exit point farthest from the river.

The second funagata yashiki from the upstream direction

faces the river as do the stone walls, extending upstream.
There is also bamboo on the riverbank, and bamboo inthis grove cannot be harvested.

Although there is a stone wall behind the second
funagata yashiki, there used to be another house directly

downstream from here; therefore, the stone wall is

Photo 2. Stone wall surrounding a houseconsidered to have been created for this structure.

Observing the third to fifth funagata yashiki from the

upstream direction together, there are no identifiable
stone walls upstream from the houses (with the

exception of those on the riverbank). However, there
are some residential areas at a spot one level lower
than upstream that use small differences in elevation

to function in a manner that is similar to the funagata
yashiki. Moreover, between houses, there are stone walls
and block fences which act as separate measures for
defending against flooding.

Photo 3. Stone fence and a bamboo grove(3) The History of funagata yashiki on the Hidari-Ikisa
River

It is unclear when the funagata yashiki in this area werebuilt.

In the Higashi-Matsuura District Ikisa Village Miniature

Drawing (drawn in 1881) no houses are depicted at thefarthest upstream point, whereas houses are portrayedfrom the second house from the upstream direction. The
presence of funagata yashiki is confirmed at the farthest
upstream point in an aerial photo from 1947 (year 22 of
the Showa Period) as well as a strip of trees upstream

Photo 4. A stone fence placed upstream becomes lower in the upstream
directionfrom the houses, which is the present status of the area.

The local people have indicated that significant flood
damage occurred in 1895 (year 28 of the Meiji Period).
Moreover, they have indicated that the houses to theriver side of the first funagata yashiki were washedaway, and stone walls and other structures around theremaining houses were fortified.

Over 100 years after these structures were built, they
continue to protect homes from floods.

Drawing 1. Part of the Higashi-Matsuura District Ikisa Village Miniature
Drawing55

The Flood Submerging Bridges and Lowlevel Crossings of the Matsuura River
Kyushu University

Although the Matsuura River was a shipping route,people have lived along its banks since ancient times.
The river is situated between various key points, suchas the Ariake Sea and Sea of Japan, Nagasaki andFukuoka, with roads (including the Karatsu Highway)

Teramura Jun

Flood submerging bridges have low piers and are shortin height. There are benefits to flood submerging
bridges including the fact that building costs are
significantly lower, and they do not obstruct theriver scenery. However, the disadvantages of thesehaving been developed nearby.

structures are that because they become submerged

People frequently crossed the river by various

there is a high risk of damage from floods. They

methods, including flood submerging bridges and lowlevel crossings, both of which have remained to thisday.

during floods, passage is temporarily impossible, andimpede the flow of floodwaters; therefore, there is anincreased possibility of damage from such disasters.
Based on these factors, this type of bridge is graduallydisappearing across Japan.

(1) Flood Submerging Bridges of the Matsuura
River

Flood submerging bridges are also called sinking- Flood Submerging Bridges on the Matsuura River

Currently, a total of nine flood submerging bridges

bridges or submersible bridges. When a flood occurs
and river water levels rise, the bridges become
submerged in the river. The flood submerging
bridge on the Shimanto River in Kochi Prefecture isparticularly well-known. Moreover, such bridges arecommon in this as well as the Oita prefectures.
These bridges are often placed across high water
channels and compared to conventional bridges built
at a higher elevation, in relation to embankments.

Photo 1. Flood submerging bridge on the Shimanto River

56

Image 1. Distribution of flood submerging bridges on the MatsuuraRiverexist in the Matsuura River system. Including thethree structures removed in 2019, traces of three
additional bridges have been confirmed.
Although there were more flood submerging bridges
in the past, I have yet to uncover knowledge aboutthem.
The removal of some of these bridges was part of the
Matsuura River improvement plan, and this may havebeen unavoidable on this river, which has witnessed
massive floods in recent years.
Photo 3. Removal of the Okawano flood submerging bridge

Photo 2. The Okawano flood submerging bridge

Photo 4. The Okawano flood submerging bridge had stone girders

Photo 5. The Sari flood submerging bridge57

In the river basin, this type of bridge is noted on
the Matsuura, Tokusue, Kyuragi, and Chokai Rivers.
These are the main river and its primary branches,
which are relatively large. These bridges can beclassified into those directly downstream from weirs
and those without any characteristic structures
nearby. Most flood submerging bridges without any
structures nearby are approximately half the height ofembankments, and the bridges downstream from weirs
tend to be in relatively lower locations.
Photo 6. Flood submerging bridge downstream from a weir

The currently existing bridges are all built using
concrete. However, the Okawano bridge removed
during the winter of 2019 was partially built usingstone girders. Therefore, we can imagine that thebridge had existed there for a long time.
(2) Matsuura River Low-level Crossings

At low-level crossings, a road is laid directly on theriverbed, with the river running over the road. They
are simple river crossing structures. Given that it isextremely dangerous to cross a river with a high flow
Photo 7. Low-level crossing

rate, even without flood conditions, the roads werenecessary and sufficient for past lifestyles (e.g., forcrossing the river to go to agricultural fields).
Even nowadays, this type of river crossing is observed
worldwide, primarily in rivers in mountainous areas.
- Matsuura River low-level crossings

Low-level crossings on the Matsuura River serve afunction ancillary to weirs—they provide a method forcrossing the river, and at normal water levels, the rivercurrent passes through the area under such a crossing.

Image 2. Distribution of low-level crossings on the Matsuura River

Photo 8. Flood submerging bridge and low-level crossing on the Tokusue
River
58

There are currently 20 of these crossings on the
Matsuura River, and 13 of the crossings serve
an ancillary function, such as river crossing. The
remaining seven seemingly do not have any suchfunction; they are merely low-level crossings.
In most cases, these crossings are on rivers smaller
than those that have flood submerging bridges,

Although ensuring the highest level of disaster safety
is an important task, flood submerging bridges andlow-level crossings that become submerged during
floods provide a cultural value that portrays therelationship between a river basin society and thehistory of life in the area. Therefore, we must consider
methods of increasing flood damage safety while
appropriately maintaining these structures.

and only one low-level crossing each is noted on amain river and primary branch. The crossing on theTokusue River, a primary branch, is unique because
half of it is a flood submerging bridge. Therefore,
we can say that these crossings are placed on rivers
smaller than those that host such bridges.
Low-level crossings come in various sizes, from thoseusable by light automobiles to those that can becrossed only on foot. Bridges can be observed near allthese crossings, which are used as extensions of ridges
or paths between rice paddies and as farm roads. They
are not the primary local roads.
(3) The Future of Flood Submerging Bridges andPhoto 9. A low-level crossing passable only on footLow-level Crossings

Flood submerging bridges on the Matsuura Riverare currently being removed. Moreover, it is highly
likely that they will all disappear in the near future.
They become submerged during floods, and thus
obstruct the downward flow of floodwaters. Due tothe blockage of water flow and driftwood becoming
lodged, the high probability of water damage isundeniable. Moreover, their use is limited because
most of the bridges cannot be crossed by cars.
Therefore, they are of low importance as roads andremoval are becoming alternative options.

Photo 10. A low-level crossing weir passable by cars

Low-level crossings face similar circumstances.
Although their removal is not as remarkable as thatof flood submerging bridges, because they servea secondary function to weirs, they are primarily
considered to be tentative river crossings, and there
is no reason to actively maintain them. There are
no prospects for their sufficient maintenance in the
future.
Photo 11. A flood submerging bridge with collapsed girders
59

Niji-no-matsubara
Kyushu University

Kitamura Keita

Photo 1. Niji-no-matsubara seen from afar (photo taken from the Kagamiyama observation platform.

(1) Niji-no-matsubara

wind, salt, and sediment that the winds carried

Karatsu Bay and is considered one of the three most

Shimanokami Terasawa passed an order to plantNiji-no-matsubara is a pine forest along the coast of
scenic pine groves in Japan. It has been designatedby the national government as a Special Place of
Scenic Beauty. This pine grove is approximately 500
m wide and roughly 4.5 km long. It has an area ofapproximately 214 hectares and contains 1 million
black pines. There are two theories about the originof its name: the first theory is that the original

length of the pine grove was two ri in length (about

8 km) and the second theory is that the arc shapeof the grove and its colorful scenery resemble arainbow (niji).

(2) Origin and Functions

The origins of Niji-no-matsubara can be traced

back to early modern times. Shimanokamihirotaka

led to damage to nearby fields. To prevent this,a black pine forest along the coast. Planting Nijino-matsubara enabled the coastal area to avoid thesalty sea breezes and windborne sand damage. To
preserve this grove, Shimanokami Terasawa issued

a notification that anyone damaging any of his
seven beloved pine trees would suffer a punishment
equivalent to the punishment issued for those who
commit murder.

The original purpose of Niji-no-matsubara was toprotect agricultural land from wind, salt, and sanddamage. This method is also considered to haveprotected the land against tsunami and tides. Whenthe March 11, 2011 Tohoku Earthquake occurred,

Terasawa, the first Daimyo of Karatsu, was focusedon developing new agricultural land. However,the northwest seasonal winds blowing in from

Karatsu Bay posed a problem to this plan. The

Image 1. Niji-no-matsubara
60

Photo 2. Shoro and shoro manju

(4) Preservation Activities

Although there are pine forests throughout Japan,
most of them are man made because such forests

cannot be maintained without human intervention.
These forests are established on soil that is lacking
in nutrients, (similar to that of beaches) however,this soil develops nutrients from fallen pine needles.
Other plants then gradually grow when thesenutrients become available. When this occurs, if
there are trees that grow taller than the pines, thePhoto 3. Inside Niji-no-matsubara

pine trees can no longer absorb sunlight and end

it was reported that the Kujukurihama beach andphenomenon is called succession. Black pines resist

the pine forest protected it against tsunami-inflicteddamage.

Nijinomatsubara also serves to function as a healthprotection forest. Although it is near the mainstreets of Karatsu City, this pine grove cleans
the air and blocks out noise to protect the living

environment of the local people and provides nature
recreation in the forest and sea.

up decreasing in number and disappearing. Thissalt damage and also grow well in wastelands.

During winter, they keep their needles which allows
them to maintain their ecological function. We
should preserve coastal black pine forests in orderto preserve their natural disaster reduction function.
To control succession, people rake fallen pineneedles to maintain pine forest functioning, which

prevents fertilization of the soil and ensures that

other vegetation does not grow. Pine needles wereused as fuel in the past; therefore, the fallen needles(3) The Blessings of the Groves

were collected. In recent years, however, this raking

from pine forests are all very useful. In particular,

withered and died due to pine weevils.

The lumber, fallen needles, and pine resin harvested
fallen pine needles are easily obtained by using

has been insufficient, and many pine trees havea pine needle rake; and during the early modern

Due to these circumstances, local civil society

in daily life. During World War 2, ship building

Niji-no-matsubara, and they have remained active

times, they were treasured as a source of fuelmaterials and pine oil were harvested here.
Moreover, shoro mushrooms are only found in such

black pine forests, thus this area is famous for its

organizations were formed to revitalize and preservein restoring the white sands and green pines of thispine grove.

shoro manju, which imitates the shape of thesemushrooms.

Having been designated a Special Place of Scenic

Beauty; Niji-no-matsubara is highly valued forits scenery. The contrast between the white
decomposed granite soil formed by the weathered

granite and the pine trees bent by the northwest
seasonal winds, called “white sand, green pines,”

has been appreciated by people since ancient times
as an example of beautiful oceanside scenery.

Works cited
Saga Prefecture History Committee. Saga Prefecture History
Middle Volume (early modern period) 1968
Okazaki, Hiroko; Ooki, Junichi. Survey Report on Kujukurihama
Tsunami Sedimentation and Coastal Topography Changes, Reportof the Journal of the Natural History Museum and Institute, Chiba(J. Nat. Hist. Inst. Chiba) 12(1) : 1-15. March 2012.
Watanabe, Taiki; Yokouchi, Norihisa; Okada, Tomohide; Mimizo,
Hiroyuki. Niji-no-matsubara Landscape Management Research:
The Relationship between Changes in Management Details andLandscape Evaluation, compilation of landscape and design
research and lectures. No.1 December 2005.

61

【Future traditional and local knowledge
and Azamenose】

Photo: Kitamura Keita

The Restored Floodplain Wetlands of the
Matsuura River: Efforts at Azamenose
Kyushu University(1) Matsuura River Overview and Azamenose

land cultivation, and decreased river continuity. The

Nature Revitalization Projects

decreased functioning of rice paddies, which have

Kurokamiyama system in the Kishima District ofis considered to have a significant negative impact

The source of the Matsuura River is in the
Saga Prefecture. The river flows north throughmountains, the Karatsu plains, and into the Genkai
Sea. The Matsuura River has a river basin area of

446 km and a river channel length of 47 kms. The
2main branches of this river are the Kyuragi and
Tokusue rivers. Approximately 84 % of the Matsuura
River basin is mountainous, and roughly 70 % ofthis mountainous area is covered by coniferous
forests. Natural stretches of rapids and deep pools

have remained in the middle and upper reachesof the basin, including the two aforementioned

branches. Most of the riverbed downstream is
occupied by medake (Pleioblastus Simonii) andAmur silvergrass (Miscanthus saccharif lorus)

a compensatory function for floodplain wetlands,(Shimatani 2003). In the Matsuura River, a centeredapproach to revitalizing such wetlands involves

making efforts for the recovery of animals that relyon this terrain and improving the river environment.

The center of this activity is the Azamenose area,

wherein a project is being conducted to revitalize
the wetlands. Due to the enactment of the Nature

Revitalization Promotion Act in 2003, increased

efforts have been made toward this end acrossJapan, and the Ministry of Land, Infrastructure,

Transport and Tourism (MLIT) has also started
revitalization work. Among the first of these is the
Azamenose Nature Revitalization Project.

clusters, with mostly common reeds and Korean

Azamenose is situated in the middle reaches of theare nearly 1 million people living in and aroundon its left bank, whereas no such structures are

willows in the middle and upper reaches. There

the river basin, with most of the population
concentrated in Karatsu City downstream.

Observing the changes over time in the floodplain

and the former riverbed of the river, the Matsuura

River used to have a floodplain of approximately
12.1 km and a former riverbed of nearly 2.0 km for2

2

a total of 14.1 km in floodplain wetlands. However,2

only approximately 1.1 km of this environment has
2remained (26 km upstream from the main stretchof the river), thus nearly 92 % of the original
wetlands have disappeared. The causes for theirdisappearance include; direct loss of wetlands

due to rice paddy development, loss of continuity

caused by flood control from river improvements
and lower water levels, concrete water channels for
64

Hayashi Hironori

Matsuura River. There are strong embankments

featured on the right side, thus leading this area tobecome flooded annually. On the Matsuura River,approximately three km upstream from here, there isa narrow, long meandering section called Komanaki.

A project to create a shortcut flood control channel

through this stretch was completed when studies
for the Azamenose area started. Upstream from thisnarrow section is a stretch that is prone to flooding,but the shortcut has decreased water levels one totwo meters on the river upstream from Komanaki,

thereby significantly reducing flooding damage.
Therefore, this channel at Komanaki was a key
flood control project in the upstream reaches of the
Matsuura River. Due to this project, however, there

was an increased risk of flood damage downstream,

Sea of Japan

Azamenose

0

2.5

5km

Matsuura River floodplain

Image 1. Azamenose location

we engage them in discussion.” This is how theand reaching an agreement to start the project

took over 20 years. The Azamenose area vicinity is

Azamenose nature revitalization project started.

to flooding, thus when flood control measures

The Azamenose project is not based on the Naturewater from the new Komanaki channel. Althoughendeavor. There was a voluntary review committee,

embankments and land acquisition, were consideredadvisors (not in the primary decision-making body).

a detention basin in the riverbed by acquiring land.

as nature revitalization plans; the project proceeded

following intent; “We will do nature revitalization

The project was conducted in this style because thein doing this will be on their motivation while

only involved one town, and the only agency ofthe last remaining downstream area that is prone
started in this area, it became possible to discharge

Revitalization Promotion Act; it is an MLIT

numerous flood control measures, including

with participants from academia serving as outside

for Azamenose, it was ultimately decided to work on

There were no authorized planning documents, such

The MLIT River Bureau at the time expressed thewith the committee discussing and altering plans.

projects if the local people want them, so the focus

subject area was relatively small, thus the project

Terraced rice fields(gakushuden)

Education Center

Shitaike

UwaikeTonboikecreek

Oxbow lakes
Matsuura River
Image 2. Map of Azamenose

65

A

B
Upstream

Downstream
Upstream

Downstream

C

UpstreamD

Downstream

Upstream
Downstream
Photo 1. Azamenose scenery: (A) Before work started (B) After nature revitalization (C) Under normal conditions (D) During flooding

the national government that was involved was

between the river surface and rice paddies was overoccurred in the Azamenose Review Committee. The

pumping from reservoirs and the Matsuura River.

the MLIT. Discussions regarding the projectissues regarding goal setting and accommodative
management methods were discussed and decided
by this committee.

To restore the wetland environment, hydrologicalcontinuity with the river and a flow rate changing

dynamic system were recreated by lowering the
ground level approximately 5 m. As a result, the(2) Azamenose Overview

wetland environment is maintained as usual, andthe Matsuura River (Image 1). The riverbed slope

maintain moisture in the wetlands, the new ground

Azamenose is located 15.6 km from the mouth ofof the main river here is 1/1350, which is classified
as segment 2 (Yamamoto 2004). This wetland has alength of 1,000 m and a width of approximately 400

m, for a total area of roughly 6.0 ha. It is composedof six ponds (Uwaike, Shitaike, Tonboike, oxbow

lakes, etc.), terraced rice fields, and creeks thatconnect to the main Matsuura River (Image 2).

The Azamenose area was used for rice paddies
before being developed into a floodplain wetland(Photo 1A). During that time, the height difference66

5 m, thus water was supplied to the paddies byfloodwaters can enter during floods (Photo 1B). To
level was T.P. 2.5 m, approximately the sametothat of the Matsuura River in normal conditions.
Moreover, the wetland creek riverbank elevation

was set at T.P. 3.5–4.0, referencing water levels fromthe past April floods, to ensure that floodwaters

during spring–summer can inundate the wetlands.
To maintain this environment, the ground wasadaptively excavated to ensure that in March 2006,
the creekbank elevation (elevation of the banks of

Shitaike and Uwaike) reached a depth of T.P. 3.0 m.

Moreover, Photo 2 shows changes in the Azamenoselandscape over time. Vegetation was not being

Image 2). There is also a creek in the wetland forland was barren. Floods, however, brought various

water enters from an inlet through the creek, and as

actively planted here, thus when work started, theseeds (Hayashi et al. 2011), thus in 2012, eight years

later, wetland vegetation, including willow trees over
five meters tall, had naturally recovered.

In Azamenose, it is necessary to prevent directdrainage and to allow floodwater in. During a flood,

the water level rises, the floodwater spreads acrossthe wetland (Photos 1C, D). During these events,

various matter and living creatures enter Azamenose(Image 3).

inflow of floodwater and sediment from upstream toTable 1 presents the results of calculating thefloods, the water flows in from an inlet locatedelevation, based on the results (Image 6) of

maintain the back marsh environment; thus, during

downstream (backwater method; the red arrow in

September 2001

There was a broad expanse offertile fields. The Azamenose Review Committee
was inaugurated in November 2001.

frequency and number of days of flooding byobserving water levels here for one year. One

March 2004

Immediately after work: The

body of water in the foreground is Shitaike. When
excavation started, the land was barren without
any vegetation.

April 2008

Four years after work: The bodyMay 2010

Six years after work: There isof water in the distance is Uwaike (completed

herbaceous vegetation, and willow trees havein 2006). Flooding delivered various seeds, andstarted to grow around Shitaike.

herbaceous vegetation is recovering.

67June 2011

Azamenose during flooding:

Azamenose in August 2012: The willow trees have

Floodwaters have flowed in from the maingrown, with the tallest tree exceeding five meters

Matsuura River, and the entire area has become ain height. The scenery is approaching the level of

pond.

improvement imagined by the Committee whenplanning started. Currently, Azamenose is lushwith valuable flora and fauna.
Photo 2. Azamenose scenery over the years

Table 1 Frequency and number of days of flooding by elevation at Azamenose

Elevation
TP 7.0TP 6.0TP 5.0TP 4.0TP 3.0TP 2.5Flood frequency(times/year)
3
5
7
9
21
27

Flood number of days
(days/year)
0.6
1.4
2.8
6.1
20.1
106.0

Bodies of water at each elevation(embankment height)
Tonboike
Creek, Shitaike, Uwaike

During flooding

Under normal conditions

Azamenose
Matsuura River main section

Azamenose
Matsuura River main section

Image 3. Azamenose is an independent body of water under normal conditions, but flooding delivers various objects and living creatures onto the land.

68Image 4. Changes in water level at Azamenose (February 2011 to January 2012)

significant characteristic of Azamenose is that varied

The most significant characteristic of goal 1 is notof such an environment and the terrain that it

as a target the revitalization of a habitat for common

wetlands are formed and maintained by the gradientcreates.

(3) Azamenose Nature Revitalization Projectthat it set specific revitalization goals, but that it set
species that rely on a floodplain environment. For

example, as seen with the Japanese crane on theKushiro marsh and the stork on the Maruyama

Goal Setting

River, in nature revitalization projects, endangered

wetlands have disappeared (Shimatani 2003), andof progress. However, for the Azamenose, the goalOn the Matsuura River, 92 % of the floodplain

most rice paddies (which played an alternative role

to wetlands) have ceased to provide such a function.
As a result, the numbers of catfish and koi, which
rely on these wetlands, have decreased along withspecies sometimes become indicators or symbols

was the revitalization of a habitat of all species,

including koi, crucian carp, catfish, and loach, thatused to be common.

opportunities for humans living along the river toIn the Azamenose nature revitalization project,

to revitalize the floodplain has led to efforts tolocal participation. In this process, many Review

encounter these fish. Adopting a centered approach
restore wildlife that rely on this habitat, thereby

improving the river environment. The Azamenose

nature revitalization project has been part of thisinitiative.

Two goals were set for the Azamenose naturerevitalization project;

1) Revitalize the river floodplain wetlands

the planning review was conducted throughCommittee participants shared their opinions;“We used to be able to catch creatures like loach,crucian carp, koi, catfish and river shrimp in therice paddies and rivers, so we came into contact
with animals every day,” and “Azamenose should

be a place where people can encounter other livingorganisms.” Goal 2 was established based on thisopinion.

2) Revitalize interactions between people and otherliving things69(4) Accommodative Management and Local

1. Decrease the ground elevation of the creek banks

Knowledge

from T.P. 3.5 m to T.P. 3.0 m to make the area

conducted to change ground elevation and terrain

frequency of 15–20 times/year)

In this project, accommodative management isgradient, along with monitoring the results ofsurrounding the creek into a wetland. (flooding

habitat and breeding circumstances of the local

2. To restrain the strong growth of terrestrial exotic

work was completed. After the first phase of work,change the slope gradient of Shitaike and the east

flora and fauna as well as groundwater levels after

intermediate monitoring was conducted from 2004
to 2005, and this revealed the following issues.

vegetation and expand the wetland vegetation area,side of Uwaike from a steep slope of 50–70 % to 20% to expand the frequently flooded surface area.

1. The creek and Shitaike ground elevation were

3. Plant willow trees to control the increase inrelatively high elevation of T.P. 3.2 m or more,of exotic herbaceous plants.

T.P. 3.5 m, and when in dry conditions and at theexotic Canadian goldenrod grows in thickets.

2. Increasing aridization was noted on the roadside(near town) of Shitaike, and there are clusters ofvegetation primarily including wasteland-like weeds,

wetland water temperatures and the strong growth

4. Build wooden fences on the creekbank to secure

the water surface width and control bank collapse
upstream.

thus the ecotone from the body of water to dry landMoreover, in the Azamenose design process, thepoor.

from local residents: “During floods, you should

wherein submerged and emergent plants thrive is

3. Clusters of single plants, such as the exotic
humectant Paspalum distichum, dominate thewater's edge at Shitaike.

Review Committee received the following proposals

allow overflow from downstream,” and “Just in case,
you should plant a bamboo grove on the upstream

embankment.” Therefore, the present form wasdesigned while referencing these comments.

4. Due to the establishment of willow trees broughtby floods and the expanded distribution of water
pepper, the creek has been covered in vegetationand open water is disappearing.

In response to these issues from 2005 to 2006, thefollowing changes were made to the project plans(Image 5).

Willow tree plantings

Expecting natural growth

Lower as much as

Expecting naturalof willow trees at the creek

possible to prevent thegrowth of willow trees

sideinvasion of exotic plants

at the pond side

Willow plantings

Town road

Matsuura River
Creek

Shitaike

Wetland vegetation
Current plan
Plan update

Image 5. Cross-section image at the initial and plan change stages (cited from the MLIT Kyushu Regional Improvement Bureau, Takeo River Office (2011)70

*This paper was written by making significant adjustments tothe existing paper by Hayashi et al. 2012b A Comprehensive
Report and Operational Evaluation of the Revitalized Floodplain
Azamenose Wetland Studies, pps. 2, 27-38.
Works cited
Shimatani, Yukihiro; Imamura, Masashi; Otsuka, Kenji;
Nakayama, Masafumi; Tomari, Koichi (2003): A Nature
Revitalization Plan for Azamenose on the Matsuura River
Advances in River Engineering 14, 451-456
Yamamoto, Koichi (2004): Structural Offshore River Studies,
Sankaido
MLIT Kyushu Regional Improvement Bureau, Takeo River Office(2011): Azamenose Records (Azamenose Area Environmental
Survey Report)
Hayashi, H.; Shimatani, Y.; Shigematsu, K.; Nishihiro, J.;
Ikematsu, S. and Kawaguchi, Y. (2012): A Study of Seed
Dispersal by Flood Flow in an Artificially Restored Floodplain
Landscape and Ecological Engineering 8, 2, 129-143
Hayashi, Hironori; Shimatani, Yukihiro; Ozaki, Ken; Ikematsu,
Shinya; Tsujimoto, Yotaku; Miyajima, Yasushi; Agata, Masahiro;
Masahiro; Suzuki, Taro; Soeda, Masashi; Kawahara, Teruhisa(2012b): A Comprehensive Report and Operational Evaluation of
the Revitalized Floodplain Azamenose. Wetland Studies pps. 2,
27-38.
Wa t a n a b e , N o r i s u k e ; H i r a k a w a , R y u i c h i ( 2 0 0 7 ) : F l o w
Characteristics of the Matsuura River Azamenose and its Impact
on the Main River, Annual Journal of Hydraulic Engineering 51,
673-678
Yamaguchi, Hirofumi; Mukai, Emi; Nakayama, Yuichiro (2005):
Research on Nature Suitability at Azamenose in the Initial Stageof the Azamenose Nature Revitalization Project. Osaka Prefecture
University Agrobiology Bulletin pps. 57, 25-32
Nature Revitalization Plan. Advances in River Engineering 14, 451456
Yoshitomi, Tomoyasu (2008): Proposal for a Nature Interpretation
Model in the Azamenose Nature Revitalization Project Area, Civil
Engineering Journal pps. 50(7), 40-45

71

Collaboration with local society
Kyushu University(1) Local Resident Participation and Forming
Agreement

Planning consideration for the Azamenose naturerevitalization project was primarily driven by the
Azamenose Review Committee (Image 1). Local
residents, persons from academia, and government
officials participated in monthly meetings to discuss plan
proposals, and maintenance and management systems.
Image 1 presents the Committee's structure. Althoughnature revitalization projects typically proceed basedon scientific studies conducted in academia, in the
Azamenose Review Committee, persons from this sector
served as advisors. The decision-making body comprised
the local residents who participated in the Committee,
which was inaugurated in November 2001, and held
over 150 meetings as of 2020. Moreover, the Committee
has the following seven rules for forming agreements,
as well as an autonomous organization, which is called
the Azame Association, is led by the local people toHayashi Hironori

support Azamenose activities, and continues to function
independently.
[1] Membership is not permanently fixed; participation
is voluntary.
[2] Discussions are conducted on a monthly basis (Evenmatters wherein decisions have already been made shallbe re-discussed based on the accumulation of knowledge
and changes in circumstances).
[3] All participants shall discuss and determine how the
Review Committee shall proceed.
[4] The Senior Citizens Association and the Women's
Association shall actively participate to work towardtaking in various local opinions and knowledge.
[5] Meetings shall be conducted in multiple venues;
there shall be no
fixed location.
Review Committee
Members

Review Committee Members

Local residents
Azame Association
Local elementary school students,
children
Women's Association
Senior Citizens Association
Riverside residents
Participating as main constituents

Decision-making body
Azamenose Review
Committee- Establishing plans- Maintenance management- Onsite surveys- Monitoring surveys

Government
Takeo River Office
Karatsu City
Participating as main
constituents

attitude shall be“Let's do this!”and not “Do it!”
[7] Persons fromacademia shallserve as advisors;

Advisors
Persons in academia
University, researchers
Government researchers
AdviceImage 1. Azamenose Review Committee structure (added to MLIT Kyushu Regional Improvement Bureau, Takeo River
Office (2011))
72[6] The basic

the main bodyshall consist
only of the local
residents.

(2) Local Resident-led maintenance and management
efforts

As previously stated, at Azamenose, work was driven
through the participation of local residents. Even
after a project was completed, the local people led
maintenance and management initiatives discussed in
the Review Committee. This work primarily consistedof (1) vegetation management (such as cutting grassand cleaning), (2) an environment education event was
conducted for elementary school students, and (3) local
traditional events. Although river managers and persons
from academia jointly participated in these activities
through auxiliary roles, these were all led by the NPO
Azame Association, which consists of local residents(Hayashi et al. 2010). In item 2, the environment
classroom was conducted for elementary school students;
these students learned about flora, fauna and the natural*This paper was written by making significant adjustments to theexisting paper by Hayashi et al. 2012b A Comprehensive Report andOperational Evaluation of the Revitalized Floodplain Azamenose
Wetland Studies, pps. 2, 27-38.
Works cited
MLIT Kyushu Regional Improvement Bureau, Takeo River Office(2011): Azamenose Records (Azamenose Area Environmental Survey
Report)Hayashi, Hironori; Shimatani, Yukihiro; Tomari, Koichi (2010):
Observations on Nature Revitalization Project Maintenance andManagement Structure. Advances in River Engineering 16, 535-540
Hayashi, Hironori; Shimatani, Yukihiro; Ozaki, Ken; Ikematsu, Shinya;
Tsujimoto, Yotaku; Miyajima, Yasushi; Masahiro; Suzuki, Taro; Soeda,
Masashi; Kawahara, Teruhisa (2012b): A Comprehensive Report andOperational Evaluation of the Revitalized Floodplain Azamenose
Wetland Studies pps. 2, 27-38.
Tomita, Ryoto (2010): The Possibility of Temporary Agreement in Natural
Environment Collaboration, with the Azamenose Nature Revitalization
Project as an Example. Journal of Environmental Sociology pps. 16, 7992

environment at Azamenose. This led to the fulfillment of

Watanabe, Atsuko; Washitani, Izumi (2006): Generational Differences

one of the initial Azamenose planning goals—revitalizing

as seen in Riparian Environment Biodiversity Awareness and Desire forinteractions between people and nature. Moreover,

Project Participation in the Region surrounding the Azamenose Nature

this activity motivated locals to undertake vegetation

Revitalization Project. Ecology and Civil Engineering 9 (1), 31-45

management, such as cutting grass and cleaning (Hayashi
et al. 2010). These maintenance and management
activities put into practice the “wise use” clause which isstated in the Ramsar Convention. Since 2011 the project
has received social collaboration project funding from
Kyushu University; through which locals, the University,and the MLIT have collaborated to outsource fixed
point photography and other work, install rainwatertanks, create Azamenose maps, and develop the lotus
pond for viewing, among other initiatives. In particular,
the lotus pond (Photo 2) completed in 2014 marks thefulfillment of a proposal by the Azamenose Women's
Association (a review committee consisting of the local
women, MLIT officers, female Karatsu City employees,
and female students from Kyushu University) to improve

Photo 1. The environment classroom

the attractiveness of the area from the perspective of
women. After completion, the lotus pond became apopular topic on social media and as well as a new
attraction at Azamenose.
Furthermore, the Azamenose summer vacation
environment classroom started in 2007 has been
conducted continuously for 13 years until now (2019).
With many participants coming from outside areas(primarily the Fukuoka metropolitan area) in recent
years, activities at Azamenose are picking up speed.

Photo 2. The Azamenose lotus pond
73

The Environment of Azamenose
Kyushu University

Hayashi Hironori(1) Changes in Floraconfirmation of 11 families and 35 species of fish.

(MLIT 2011), Azamenose flora are divided into

species confirmed through this monitoring. In 2003,

Based on the results of a monitoring study
the following clusters; wetland plants (e.g., water
caltrops (Trapa japonica), water pepper (Persicaria

hydropiper), and mizosoba (Polygonum thunbergii)),

quasi-wetland plants (e.g., fall panicum seeds(Panicum dichotomiflorum Michx.) and Salix pierotii),and wasteland plants (e.g., Canada goldenrod andAmbrosia trifida(Solidago altissima)). At points

Image 1 presents yearly trends in the number ofwhen only the creek was completed, monitoring only

confirmed 12 species. From 2004, when Shitaike wascompleted, although there were some variations,
24–28 species were confirmed each year. A totalof 19 species, including cyprinid fishes, catfish(Silurus asotus), loach (Misgurnus anguillicaudatus)and medaka (Oryzias) have been confirmed overlower than the T.P. 3.0 m that one would expect intime. In particular, cyprinid fishes, catfish, loach,then stabilized. Functioning as a breeding groundrevitalization goals because they require a floodplain

a wetland, the share of wetland plants increased andfor wetland vegetation, one of the initial planninggoals, is thus considered to be mostly achieved.
(2) Changes in Fish Fauna

wetland environment during spawning season.
Based on these facts, Azamenose is considered topossess a certain advantage as a habitat for such

Seven years of monitoring have led to the

Number of species confirmed

and others were species mentioned in the planningspecies.

During development

After development
Azamenose

At the 15.8K point on the Matsuura River
Image 1. Changes over time in the number of fish species confirmed at Azamenose (cited from MLIT Kyushu Regional
Improvement Bureau, Takeo River Office (2011))

74

Number of larval fish hatching

Photo 1. Confirmed eggs and larval fish

Azamenose

Main river

Image 2. Comparing cyprinid fish spawning potential at Azamenose and on the main Matsuura River(3) Revitalization of Fish Spawning Habitatof the Matsuura River (Image 2). Therefore, we

confirmed to spawn in Azamenose (Photo 1).

spawning ground for fish on the Matsuura River.

Many cyprinid fishes, and catfish have been

These species primarily do so in water grass andcan assume that this wetland plays a key role as a

emergent plants near the shore. In the initial project(4) Bivalve Habitat Revitalization

may spawn here. Moreover, as explained in theassumed to be a revitalization goal. However, itplanning, these fish were identified as species that
following section, numerous mussels have been

confirmed in Azamenose.Among these mussels,

spawning has been confirmed for Acheilognathus.

In addition, a total of 22 species of larvae andjuvenile fish, including the freshwater minnow, darkchub, Acheilognathus rhombeus, Tanakia lanceolata,
Japanese dace, Sarcocheilichthys variegatus, Biwia

zezera, and loach, have been confirmed. Given their

existence, it is possible for Azamenose to function asa spawning ground for these fish as well. According
to a study by Ozaki et al. (2010), the number of

eggs spawned by cyprinid fishes at Azamenose is

50 times higher than those on the main stretch

In initial project planning, mussels were notbecame clear in 2007 that approximately 1,500 ofthem lived in Shitaike (Hayashi et al. 2009). The

three species confirmed were Sinanodonta lauta,
Unio douglasiae, and Lanceolaria grayana (Photo2). Among the 1,500 such creatures, 98 % wereSinanodonta lauta (Hayashi et al. 2009). Azamenose

is, therefore, considered a particularly favorable
habitat for these mussels. However, due to theconfirmation of a water caltrops invasion in 2008,
and this vegetation entirely covering Shitaike inthe following year, an oxygen deficiency was notedin this body of water. This caused the death of the
majority of mussels in Shitaike. However, a 201475

survey confirmed that a large number (estimated1,000) of mussels (mostly Sinanodonta lauta andUnio douglasiae) continued to inhabit Uwaike andTonboike. The causes of this are considered lower
levels of nutrient salt and organic matter supplied

during flooding, compared to Shitaike because theseareas are somewhat removed from the inlet (about

150 m) as well as the invasion of water caltrops
seeds (Lie et al. (2014)).

It is also clear that Sinanodonta lauta is distributed
only in limited locations on the main Matsuura

Photo 2-1. Mussels of the order Unionoida confirmed at Azamenose(Sinanodonta lauta)

River (Hayashi et al. 2011), thus Azamenose

functions as an important habitat for thesemussels
in the river system.

(5) Issues at Azamenose

Two Azamenose nature restoration project goals(1. restoration of the river floodplain wetlands, 2.
revitalization of interactions between people andother living things) have mostly been achieved,
thus the project can be deemed a success. However,significant issues related to Azamenose continue
to persist. One future issue regarding vegetation

Photo 2-2. Mussels of the order Unionoida confirmed at Azamenose (Unio
douglasiae)

is developing countermeasures against exotic flora
represented by the Canada goldenrod and Ambrosia
trifida, which grow prolifically in areas with low

flooding frequency. In particular, the cover provided

by tall trees, such as willows, has led to methodsof controlling and removing exotic fauna into view,
and in the future, we will need to respond to theseissues. Furthermore, in wetlands, where elevationis relatively low, the strong growth of willow trees
is remarkable. This plays a key role in maintaining

Photo 2-3. Mussels of the order Unionoida confirmed at Azamenose(Lanceolaria grayana)

Photo 3. Comparison before and after felling willow trees (left: before, right: after)76

the wetland environment and in providing a habitat

for fauna. Moreover, there were concerns regarding
trapping garbage and sediment. As a result, after

discussion by the Review Committee, it was decided*This paper was written by making significant adjustments to theexisting paper by Hayashi et al. 2012b A Comprehensive Report andOperational Evaluation of the Revitalized Floodplain Azamenose
Wetland Studies, pps. 2, 27-38.

to periodically thin the willows on a large scale(Photo 3). Although both functions of providing areasonable scenic view and a habitat for fauna arebeing maintained, it has been determined that thecontinued observation of transitions in flora and to
conduct discussions is appropriate.

Maintenance and management activities at
Azamenose are led by the NPO Azame Association.

Although there is currently a strong structure for
this, the participating members have become fixed,
and the people involved are aging. Developing theirWorks cited
Hayashi, Hironori; Tsujimoto, Yotaku; Shimatani, Yukihiro, Kawaguchi,
Yoichi (2009): A Case Study on the Anodonta Genus Ecology andInvasive Systems in Revitalized Wetlands. Annual Journal of HydraulicEngineering 53, 1141-1146
Hayashi, Hironori; Shimatani, Yukihiro; Ozaki, Ken; Ikematsu, Shinya;
Tsujimoto, Yotaku (2011): Research on Flow Characteristics of Order
Unionoida Mussels. Annual Journal of Hydraulic Engineering 55, 13931398
Hayashi, Hironori; Imaguma, Yusuke; Shimatani, Yukihiro (2012a): An
Investigation of the Physical Control Factors of Canada Goldenrod

successors is, therefore, an urgent issue. Currently,

Clusters in Floodplain Wetlands. Advances in River Engineering 18-29,

between the senior citizens and elementary school

Hayashi, Hironori; Shimatani, Yukihiro; Ozaki, Ken; Ikematsu, Shinya;

an active intergenerational exchange is conducted

students through environment classrooms andother activities, but the parents of the children
rarely participate in any such initiatives. The
primary reason for this is thought to be due to abusy, middle-aged lifestyle with little free time. For
these activities pertaining to developing successors,each generation is continuously involved in orderto create maintenance and management systems.

Establishing a mechanism that enables this todevelop successors is the most important issue forthe future. Moreover, because some items used tomaintain and manage the terraced rice fields for

34
Tsujimoto, Yotaku; Miyajima, Yasushi; Agata, Masahiro; Masahiro;
Suzuki, Taro; Soeda, Masashi; Kawahara, Teruhisa (2012b): A
Comprehensive Report and Operational Evaluation of the Revitalized
Floodplain Azamenose. Wetland Studies pps. 2, 27-38.
Kadoya, T.; Suda, S.I.; Nishihiro, J. and Washitani, I. (2007): Procedurefor Predicting the Trajectory of Species Recovery based on the Nested
Species Pool Information: Dragonflies in a Wetland Restoration Site as aCase Study. Restoration Ecology 16, 397-406
MLIT Kyushu Regional Improvement Bureau, Takeo River Office(2011): Azamenose Records (Azamenose Area Environmental Survey
Report)Ozaki, Ken; Hayashi, Hironori; Nakajima, Jun; Ikematsu, Shinya;
Shimatani, Yukihiro (2010): Research on the Functioning of Revitalized
Wetlands as Fish Spawning Sites. Ecology and Civil Engineering Society,
Collection of Speeches from the 14th Presentation Symposium 39-42

environmental study require payments for expenses,

Liu, Jia; Hayashi, Hironori; Inaguma, Yusuke; Ikematsu, Shinya;

fundraising is also required. Although funding

Quality and Feeding Environment for a Freshwater Mussel’s (Anodonta

such as fuel for tractors and insect repellent, somefrom the national government and local authorities
currently covers these expenses, this funding is notguaranteed to continue. Acquiring the minimum

amount of funds required for maintenance andmanagement is a significant issue.

Shimatani, Yukihiro; Minagawa, Tomoko (in press): Factors of Water
lauta) Survival in a Restored. Wetland Society of Wetland Scientists
Nakamura, Futoshi (2003): Thinking, Studies and Plans concerning Riverand Wetland Nature Restoration, with the Restoration of the Wetlands,
Floodplains and Meandering Waterways of the Kushiro Marshes as
Examples. Ecology and Civil Engineering 5(2), 217-232
Shimatani, Yukihiro; Inamura, Masashi; Otsuka, Kenji; Nakayama,
Masafumi; Tomari, Koichi (2003): The Azamenose Nature Restoration
Plan Advances in River Engineering 14, 451-456
Yoshitomi, Tomoyasu (2008): Proposal for a Nature Interpretation
Model in the Azamenose Nature Revitalization Project Area. Civil
Engineering Journal pps. 50(7), 40-45

77

The Flood Control Function of Azamenose
Kitamura Keita

Kyushu University

fixed point camera

Matsuura River

Azamenose

Opening

Photo 1. Azamenose(1) Azamenose(2) Onsite Conditions During Flooding

revitalization floodplain wetland project, it has

intervals by using a fixed-point camera from the

Although Azamenose is a complete nature
the same structure as the floodplain open levees
explained in the previous chapter. In other words, it

has a creek drainage opening, situated downstream.
Different from these open levees, however, theembankment upstream from the opening is fivemeters lower than the embankment on the opposite

I captured pictures of flooding conditions at regular
positions shown in Photo 1 during the August 2019heavy rains (Photos 2–5). On the Matsuura River,the flow is from the left of the photo to the far
right. The arrows in Photos 2–5 show the directionof the floodwater flow.

bank. I verified the type of flooding that occurs at

At 10:00 on August 27 (Photo 2), for the first time,

the flood control effects using an onsite study ofwater levels in the downstream pond. Similar to

Azamenose, which has such a structure, as well as

the flooding in the August 2019 torrential rains anda recreation simulation, similar to the Okawano
floodplain open levee.

flooding into Azamenose was caused by increased
the floodplain open levee type of flooding, thebackwater phenomenon occurs from the opening
due to increased water levels on the main stretch of

the river. This supplies floodwaters to Shitaike andUwaike. During that time, the floodwater current at
Azamenose was extremely gentle.

78

9:00 on August 28, 2019
Water level peak

10:00 on August 27, 2019
Occurrence of backwater phenomenon from opening
Photo 2. Azamenose(10:00 on August 27, 2019)

Photo 4. Azamenose(9:00 on August 28, 2019)13:40 on August 28, 2019
Retention/drainage from opening

18:20 on August 27, 2019
Occurrence of flow from upstream to downstream
Photo 3. Azamenose(18:20 on August 27, 2019)

Photo 5. Azamenose(13:40 on August 28, 2019)

Photo 6. Azamenose during a flood (11:30 on August 29, 2019)79

The state of Azamenose after the flood is shown in
Photo 6. Going downstream from upstream, grovesof mixed trees, including bamboo and willows, fell inthe direction of the flow (the trees being upset in thismanner is called a “disturbance” ). This indicates themagnitude of the disturbance from the flooding fromupstream.
Water level(m)(3) Flood Recreation Simulation

I conducted a flood recreation simulation of theAugust 2019 torrential rains under the same conditions
as the Okawano floodplain open levee mentioned
above (Image 1).

For the Azamenose calculation results, the image

shows a vector image expressing the magnitude anddirection at the time of the highest floodwater flow
Image 1. Azamenose flowrate vector and water level contour images (atflowrate peak)

After 18:20 (around sunset; Photo 3), flow fromupstream to downstream on the main part of the river
was confirmed, even in the wetland.

After dawn, water levels were trending upward, andaround 9:00 on August 28 (Photo 4) they approachedtheir peak. Judging from the photo, I estimated thedifference between the embankment crown on the left

levels in color. During this time, water levels arehigher than the Azamenose embankments, meaning
floodwater will flow downstream here. This led to themain riverbed expanding. As a riverbed expands, theflowrate subsequently decreases. At Azamenose, due
to the water level on the main Matsuura River being

higher than the embankments and the main stretchof riverbed widening, we can determine there is an
overall decrease in the flowrate.

bank of the main river and the water level to be 1–2 m.

Image 2 changes over time in the cross-section flow

After the peak at around 9:00, although waterorange line indicates the current allowance of overflow

levels trended downward, flood waste continued toflow. However, around 13:00 on the same day in
Azamenose, the flow from upstream to downstream(from the left to the right in the photo) on the main
stretch gradually weakened and completely stopped

around 13:40 (Photo 5) leading to flood waste pilingup. Inflow and outflow of this waste ceased, and thewater levels gradually subsided.

Looking at the above time lapse images, between
18:20 on August 27 and 13:40 on August 28, thefloodwater levels were higher than the Azamenose

embankments, thus indicating that the flood flowed infrom upstream.
80(peak), and a contour image showing the floodwater

rate 150 m downstream from Azamenose. The solidfrom the embankments, and the green solid line

indicates control of flooding from the embankments.
Comparing these two lines, when overflow from theseembankments was controlled, the peak flow rate
significantly increased.

At Azamenose, when the main river water level ishigher than the embankments, the main flow moves

downstream, as if the riverbed had expanded. As aresult, the riverbed flowrate decreases. This causes
pooling here, which results in a significant flow rate
peak cut effect.

Based on this, when a disturbance occurs in thefloodplain due to the Azamenose embankments
being low, we can observe that a significant flowrate

adjustment effect occurs. Even in disaster reduction
systems using the same floodplain, for rice paddies(which are the main land use in floodplain open leveeareas), these disturbances are a major disadvantage.

The primary purpose of rice paddies is for harvesting
rice; therefore, such events may cause the rice plants
to collapse or wither and die. In comparison, for

Azamenose (i.e., floodplain wetlands), disturbances
are actually a benefit because they maintain wetland

ecosystems. A significant number of Acheilognathus
rhombeus (Acheilognathus genus) were confirmed inthis area after this flood. Azamenose also acts as a
refuge for fish during floods.

Photo 7. Acheilognathus rhombeus confirmed after the flood

Cross-section flow rate five zone transfer average

Flooding from embankment
No flooding from embankment

Changes over time
Image 2. Changes over time in the cross-section flow rate 150 m downstream from Azamenose (five zone transfer average)81

【Traditional and Local Knowledge of the
Matsuura River】

Photo: Shimauchi Risa

Traditional and Local Knowledge of the
Matsuura River
Kyushu University

Shimatani Yukihiro

structures that continue to be used, including
Niji-no-matsubara, open levees, cross-levees,

and funagata yashiki. In the Azamenose wetland
revitalization project conducted by the MLIT, theprimary objective was nature revitalization, butthere is also a significant floodwater retentionfunction. Such projects that adeptly use the powerof nature can be called Eco-DDR or hybrid Eco-

DDR that represent Japan based on traditional
This booklet was written with a focus on the

Matsuura River as part of Eco-DDR (Ecosystem-

surpassing disaster.

by Takehito Yoshida of the Graduate Program on

This booklet also presents a general history of the

not be familiar with Eco-DDR, it is a disaster riskboats can easily travel upstream. Karatsu City,

global attention in recent years and uses ecosystems

on an important trading route since ancient times.

global warming.

crossing, transited by several small- and medium-The concept of disaster risk reduction andand the Omura and Imari Bays. In these areas, thephilosophy that preserving ecosystems by reducing

Matsuura River was an ancient artery connecting(including broad wetlands, tidal flats, and forests)

observed that there are 191 ruins situated along thephilosophy of humans actively using the power

the medieval period or earlier, thus this region was

damage prevention forests). In many cases, these

periods.Rice farming was first introduced in Japan

based disaster risk reduction) research represented

Environmental Sciences. Although readers may

Matsuura River. The river has a gentle slope where

reduction and prevention method that has gained

which is located at the mouth of the river, has been

to respond to frequent natural disasters caused by

The river basin is composed of a low ridge andlength rivers that connect easily to the Ariake Sea,

prevention using ecosystems comprises both the

upstream region is a source of obsidian, and thedisasters through conserving natural environments

Japan to the Asian continent. In this booklet, weresults in disaster prevention as well as the

Matsuura River. Among these, 172 sites were fromof ecosystems (such as coastal forests and flood

developed beginning in the prehistorical and Jomon

philosophies are combined. There are also hybrid

in the downstream reaches of the Matsuura River.

structures that have gained attention in recent years.

From the end of the medieval period, the ceramics

The Matsuura River, which is the primary focus ofthere. In the Edo Period, the region was a source

The Matsuura River has various traditionaltransportation route.

Eco-DDR combining ecosystems and man-madethis booklet, is a treasure trove for these structures.

84

technology reaping the blessings of nature andindustry started by Korean potters prosperedof coal, thus the Matsuura River was active as a

Starting in the early modern period, flood control

projects.

works including the Karatsu domain, the Niji-no-

Several traditional Eco-DDR currently remain on(Hatae River) and the Matsuura Rivers, the Daikoku

thus serve as a museum. When dealing with climate

and irrigation projects became commonplace, withmatsubara improvement, the joining of the Tokusue

Weir, and Umankashira under the Saga domain.

Currently, many old stone Weirs can be foundthroughout the Matsuura River floodplain. Alongwith the domain's projects, local construction also

the Matsuura River, with its extensive history, andchange, the knowledge of our predecessors provides
crucial suggestions. Please bring this book alongwhen you visit the Matsuura River Eco-DDR.

accounted for various flood control and irrigation

Onsite survey scenery photos (December 16–17, 2019)85◆ List of authors (in alphabetical order)

Fukamachi Katsue

Kyoto University Graduate School of Global
Environmental Studies

Shimatani Yukihiro
Graduate School of Engineering, Kyushu University
Professor of River Engineering

Associate Professor of Landscape Ecology andPlanning

Teramura Jun

Kyushu University, Faculty of Engineering

Hayashi Hironori

Kyushu University, Faculty of Engineering
Associate Professor of River Engineering

Ichimoto Naoyuki

Research Fellow in Civil Engineering History andRiver Engineering
Yoshida Takehito
Graduate School of Arts and Sciences, University of

Imari Municipal Board of Education, Lifelong Learning

Tokyo/Research Institute for Humanity and Nature

Division, Cultural Assets Section

Associate Professor of Ecology

Kitamura Keita
Graduate School of Engineering, Kyushu University
Graduate Student in River Engineering

Eco-DRR as Learned from Local History

Traditional and local knowledge of EcoDRR in and around the Matsuura River
EditionDecember 2021

Publisher

Research Institute for Humanity and Nature457-4,
Motoyama, Kamigamo, Kita-ku, Kyoto
603-8047, JAPAN
TEL：+81-75-707-2100
FAX：+81-75-707-2106
URL：https://www.chikyu.ac.jp

Project

Research Institute for Humanity and Nature
Eco-DRR Project
Research and Social Implementation of EcosystembasedDisaster Risk Reduction as Climate Change
Adaptationin Shrinking Societies

DesignShimauchi Risa

Editing

Shimauchi Risa, Teramura Jun, et al.

Print

Hokuto Print Co., Ltd.

ISBN

978-4-906888-86-3
Esta obra está bajo una Licencia Creative Commons
Atribución-NoComercial-CompartirIgual 4.0 Internacional.
©︎2021 Research Institute for Humanity and Nature