Report of Riverfront Research Institute

No.18

ABSTRUCT

September, 2007

Foundation for Riverfront Improvement and Restoration

Experimental research on restoration of the gravel bed of the
Makomanai River, Sapporo Hokkaido (interim report)
Hiroki TAKAHASHI/Noboru MARUOKA/Kiyoshi TAKEUCHI/Keizou WATANABE

The Makomanai River has many rock-bedded sections where the bedrock has been
exposed as a result riverbed degradation. This is thought to have been caused by a
combined effect of the narrow valley flat, soft rock, decreases in sediment supply due tothe check dams constructed in the 1980s, and the fixed water route of the river due tothe river improvement carried out in the 1960s. The rock-bedded river channel, lacks
river structures created by gravel (sediment) transport and scour–deposition processes
and does not have shallows or pools suitable as habitat for benthos and fishes. Floodcontrol problems caused by the scouring of revetment foundations are another matter ofconcern.
This study is underway, therefore, on technical measures to restore the gravel bed of the
Makomanai River based on adaptive management approach.
In this study, a series of model experiments was conducted on various structures andconfigurations of facilities for accelerating gravel deposition, and, according to theexperiment results, possible structures and configurations of experimental facilities were
narrowed down and on-site experiments were conducted. Then, after monitoring-based
verification, measures to be taken to restore the gravel bed of the Makomanai River
were identified.
Key words: rock bed, gravel bed, nature restoration, experimental management,
monitoring

1

River improvement to restore Thorea okadae habitats : Yasumuro
River experience -The 4th reportKentaro TAKI/Hideyuki WATANABE/Kazuyuki SAKANOI/Fumihiro TOI/Motoi
SEKI/Nobuyoshi SUGINO

In the Yasumuro River, a Class B river running in the town of Kamigori in Hyogo
Prefecture, the habitats of riverine species including Thorea okadae (chisujinori inJapanese), a rare algal species, are deteriorating because of such river works as theconstruction of multipurpose dams and agricultural weirs and channel widening. In
order to restore the river environment of the Yasumuro River, in November, 2004, theNishiharima Residents Bureau of the Hyogo Prefectural Government formulated theYasumuro River Restoration Plan featuring Thorea okadae as a symbol of restorationand has been implementing various measures according to the plan in cooperation withthe local community.
In 2005, flush releases of water by consecutive operation of agricultural weirs andstreambed disturbance (a measure popularly called "plowing a river") were carried out
experimentally. Because the effectiveness of these measures was verified, it has been
decided to carry them out on a continual basis.
This paper briefly reports on the following surveys and studies and test construction
conducted in fiscal 2006 according to the Yasumuro River Restoration Plan. In the 2006
study, a two-dimensional unsteady flow analysis model taking into consideration thelodging process of tall herbaceous plants due to the force of flowing water wasconstructed to reproduce the hydraulic quantities (e.g., water depth, flow velocity,
vegetation resistance, bed resistance) in normal times and in times of flood
two-dimensionally. Also, river channel shapes for keeping the river environment in agood condition were determined by using the calculation results obtained from the
newly constructed numerical analysis model.
Key words : nature restoration, Thorea okadae, lodging process of tall herbaceous plants,horizontal twodimensional unsteady flow analysis, test construction2

Research for riverbed excavation experiment in Awasa district,
Chikuma River
Shin-ichiro TATE/Minoru KOBAYASHI/Nobuyuki OHASHIThis paper reports the results of a series of research conducted by the Chikuma River
Ecology Research Group over a period of three years on the impact of experimental
riverbed excavation in the Awasa district of the Chikuma River on the river ecosystem.
Through field surveys, the Chikuma River Ecology Research Group conducted studies
on what kind of riverbed excavation should be done in order to restore the riverenvironment of the Chikuma. Because the low-flow channel had been fixed and thehigh-flow channel had become part of the land and was predominantly covered withalien plants, the high-flow channel was cut down into a stepped shape so that thefrequency of submersion rose locally. A major flood occurred during the research
process, making it possible to compare a human impact such as riverbed excavation anda natural impact of flood.
The bed of the high-flow channel stripped of vegetation and cut into a three-level step
shape made uniform mixture of gravel, sand and silt, and buried seeds began to sprout
all at once. In the water edge zones that formed wetland-like environments, nativeplants including rare species began to grow. After the excavation, aquatic insect species
recovered its diversity and the number up to just about same level as the control area inaround two and a half months. On the other hand, the alien plants died after the flood
water covered the riverbed and native species gave priority over afterwards.
Thus, a series of studies has shown that (1) it is possible to restore the natural riverside
vegetation including rare species, (2) the fauna and flora can recover from the impact of
excavation of the scale considered in a relatively short period of time and (3) when
excavating a riverbed, it is desirable to create the physical environments as diverse as
possible.
Key words : riverbed excavation, human impact, flood, natural impact, river ecosystem,
alien plants, native species

3Restoring gravel bars in the middle reaches of the Kinu River
Teruaki MASUKO/Yoshio MAEMURA/Tomokazu MISHINA/Seiji UCHIDA

There used to be large gravel bars dotted with boulders and large rocks in the middle
reaches of the Kinu River, and those gravel bars provided rare habitat for animals andplants (e.g., Eusphingonotus japonicus, Aster kantoensis) peculiar to gravel bars.
In the post-WWII years, the flood safety of the Kinu River as a whole was improved
dramatically as a result of large-scale river improvement projects (e.g., levees,
revetments, dams, check dams).
Locally, however, flood control problems such as streambed degradation and bankerosion have become problems in recent years, and the general trend is toward
meandering deformation accompanied by a transition from a multi-row channel to asingle-row channel. Meandering deformation is directly contributing to a decrease ingravel bars by causing, for example, a decrease in submersion frequency and tree
growth.
The intrusion of the exotic species Eragrostis curvula has also altered the habitats ofspecies endemic to gravel bars such as Aster kantoensis and Eusphingonotus japonicus,
causing those species to decrease steeply.
This paper reports on an ongoing study on the restoration of gravel bars that provide
habitat for species endemic to gravel bars including monitoring that is also in progress.
Key words : Kinu River, gravel bar restoration plan, test construction, monitoring, sandbar, species endemic to gravel bar, exotic species

4Nature restoration plan for the lower reaches of the Ishikari River
Kiyoshi TAKEUCHI/Noboru MARUOKA/Satoshi DAIMON

The area along the lower reaches of the Ishikari River used to be a wetland area dottedwith lake. As a result of various river improvement projects including cut-off projects,
urban areas and large expanses of agricultural land have emerged, and these areas havebecome centers of society, economy and culture in Hokkaido. The improvement projects
for the Ishikari River have greatly contributed to the development of the river basin but
also have had a great impact on the river basin and the environment of the river. The
resulting environmental changes are thought to be the cause of the disappearance ofAcipenser medirostris, Grus japonensis and Hucho perryi that, according to records,
used to inhabit the Ishikari River.
This report concerns the formulation of a nature restoration plan for the lower reaches of
the Ishikari River. Because it is difficult to fully restore the nature that existed in thepast from today's highly developed state of society and because diverse environments
distributed over a large area are to be restored, the plan was designed to include a
general scheme for restoring the lower reaches of the Ishikari River and a direction ofrestoration.
In this study, environmental elements used by representative species of life using theenvironment of the Ishikari River and how those environmental elements are used wereidentified for the purpose of investigating (1)the relationship between the historicalchanges in the river basin and the river and the resulting changes in the physical andsocial environments and (2) the relationship between the environmental characteristicsof the study area and the environment used by various species of life. After investigatingthese relationships, measures to be taken in connection with ongoing and planned river
improvement projects were identified.
Key words : Ishikari River, nature restoration, wetland, lake, riparian woods, indicatorspecies, adaptive
management5Restoring the gravel bars of the Ina River : verifying a hypothesis byexperimental river works（interim report）
Takayoshi TSUZUKI/Yoshifumi KODAMA/Kentaro TAKI/Satoko GOTO

The Ina River used to be blessed with such riverine features as gravel bars and shallows
and pools that provided habitat for diverse species of plants and animals. The diverse
morphological features of the river and a wide variety of plants and animals formed
complex and beautiful riverscapes and provided local residents with places for relaxing
and communing with nature. In recent years, however, the environment of the Ina Riverhas been undergoing changes such as a decrease in sand and gravel bars, tree growth
and the intrusion of exotic species and is becoming increasingly monotonic and simple.
With the aim of mitigating these problems by use of the natural resilience of the river,
the implementation of a nature restoration project for inducing a desirable response(effect) by giving an appropriate impact (improvement) is currently under study so as torestore the diversity of life by conserving and restoring the river environment andhelping the river re-create itself.
In this study, experimental river works for gravel bar restoration were carried out inorder to take adaptive and phased measures to reverse the declining trend of the gravebar environment, one of the most urgent problems among the problems being
encountered in connection with the restoration of the natural environment of the Ina
River. This paper reports on the experimental river works.
Key words : Ina River, nature restoration, gravel bar, flood-induced disturbance,experimental river works, frequency of submersion

6

Present state and analysis of river restoration in Japan
Susumu DOMON/Masafumi ITO/Jyunzo SAGO

In January, 2003, the Nature Restoration Act, a new law enacted with the aim ofrestoring lost ecosystems and other natural environments took effect. Under this law,
local efforts involving a wide variety of local entities have been underway throughout
the country for the conservation, restoration and creation of rivers, wetlands, tidal flats,
seaweed beds, rural forests, rural communities, forests, coral reefs, etc. The river
departments of the Ministry of Land, Infrastructure and Transport and local
governments are also planning or implementing river restoration plans in 47 areas inorder to improve river environments.
Local efforts to improve river environments, however, are being made independently,
and no effort is being made to share and integrate project information. This report has
been prepared for the purpose of sharing information on river environment restorationand performing a basic analysis necessary for the evaluation river restoration efforts.
Information was collected from Web sites, pamphlets and booklets, taking into
consideration the availability of information on local project information. By using theinformation thus collected, river restoration efforts in Japan were identified andanalyzed.
As a result, it has been found that nature restoration councils were formed in 26 areas,
nature restoration projects to be completed by a certain time in the past were
implemented in 5 areas, and projects targeted at certain species were carried out in 8
areas. Wetlands account for about 30 percent of all river environment elements to berestored, followed by the continuity of rivers, shallows and pools, the continuity ofwater bodies associated with river banks, lake shores, gravel beds, tidal flats and reed
beds, and water–land transition zones.
Key words : river environment, nature restoration project, nature restoration council,
regional cooperation

7

From nature-oriented river works to nature-oriented rivermanagement
Nobuyuki OHASHI/Yasushi HORIKAWA/Minoru KOBAYASHI/Tatsuji KIMURA /Shinichi YOSHIMURA

The ministerial circular issued in 1990 on the implementation of "nature-oriented riverworks" initiated natureoriented river works in Japan with the aim of conserving or
creating riverine habitats and beautiful natural environments. Although initiated as pilot
projects, nature-oriented river works have now become the norm for all river projects.
The nature-oriented river projects carried out in the past, however, include projects that
effectively combined a flood control function and an environmental function, but theyalso include many standardized projects that simply imitated methods used for otherriver sections.
This paper verifies the present state of nature-oriented river works, reviews the pastefforts and problems of nature-oriented river works identified by the Nature-oriented
River Works Review Committee established in September, 2005, in order to deliberate
on a desirable direction of nature-oriented river works in the coming years, and reports
the results of deliberations on the measures to be taken to solve the problems indicatedby the committee.
Key words : nature-oriented river management, river management, river works
following a major disaster8

Classification and mapping of vegetation at Watarase Retarding Basin
Masanori
IIJIMA/Yoshifumi
KODAMA/Miwa
KASHIWABARA/Tomoyuki ANMA/Yoshio TSUKAMOTOTOMIZAWA/Satoshi

The Watarase Retarding Basin has a surface area of about 33 km2 and is one of thelargest retarding basins in Japan. Besides playing a key role in flood control and water
utilization in the Tone River System, the Watarase Retarding Basin is positioned as oneof the major low moors (wetlands) in Japan and provides habitat for a wide variety ofplants and animals by forming a rich natural environment founded on reed beds.
Compared with what used to be, however, the present Watarase Retarding Basin has
smaller numbers and areas of ponds and wetlands, and the old landscapes formed byopen water surfaces surrounded by large ecotones have mostly vanished. It has been
pointed out that the environment of the retarding basin has degraded. It is therefore
necessary to conduct studies on how the natural environment of the Watarase Retarding
Basin can be conserved and restored.
In this study, in order to obtain basic information necessary for the conservation andrestoration of the Watarase Retarding Basin, the types of vegetation functioning as thefoundation for the ecosystem habitat of the retarding basin were analyzed on the basis of
the results of a 2005 belt transect survey on vegetation and fundamental environmental
conditions, and an analysis was performed for vegetation mapping of Regulating
Reservoir No. 2 of the Watarase Retarding Basin. As a result, the accuracy of analysis
for the mapping of vegetation types dominatedby the common reed and the silver banner grass, both of which are tall hygrophytic
herbaceous plants, was enhanced by analyzing the fundamental and physicalenvironmental data for the common reed and the silver banner grass separately.
Key words: common reed and silver banner grass, vegetation type, TWINSPAN,
decision tree, elevation, groundwater depth, groundwater fluctuation, hyperspectrum

9

Soil seed bank survey at Watarase Retarding Basin
Miwa TOMIZAWA/Yoshifumi KODAMA/Masanori IIJIMA/Toshihiro SUZUKI/Asako
FUKUSHIMAIn order to devise ways to make effective use of the soil seed bank for wetland
restoration at the Watarase Retarding Basin, seed bank surveys were conducted by using
soil samples taken at multiple locations in the retarding basin. On the basis of the survey
results, this paper reports on the usefulness of the soil seed bank and considerations inusing it.
In the 2005 and 2006 surveys, soil samples taken from three different depths at threedifferent locations at the Watarase Retarding Basin were sowed under four different
water level conditions. As a result, a total of 5,839 individuals in 157 plant species in 43
families were identified. At all soil sampling locations, about 40 percent, in terms ofboth the number of species and the number of individuals, of the identified plants were
either wetland or aquatic plants. This suggests that the soil at the retarding basin can beused for the restoration of wetland vegetation. Of all endangered species of surface
vegetation identified at the soil sampling sites, about 40 percent (8 species) have beenfound in the seed bank, too. Other endangered species that have hardly been sighted in
the Watarase Retarding Basin area, such as Ceratopteris thalictroides and Penthorum
chinense, have also been found in the soil seed bank, indicating that the use of the seedbank is an effective way to restore vegetation including these species.
The seed bank survey, however, has also revealed the presence of many alien species
that had not been sighted in the surface vegetation at the soil sampling sites, indicatingthat the seeds of alien species are also stored in the soil at the Watarase Retarding Basin.
Among those alien species, Solidago altissima is a perennial plant species that, if
established, is likely to greatly influence the surrounding vegetation. It was considerednecessary, therefore, to use these alien species only after carefully examining thequantities of the seeds of these alien species and the depths at which those seeds exist.
Key words : soil seed bank, vegetation restoration, wetland restoration, endangered
species, alien species

10Determining the cross section of the Ichinomiya River (Chiba
Prefecture) by a simple environmental impact assessment method
Susumu DOMON/Hideki TAMURA/Jyunzo SAGO/Kenzo MAEDA

The Ichinomiya River in Chiba Prefecture is a rare, environmentally important river inthe Kujukuri area in that it has estuary sand spit (tidal flat). The estuary sand spit has
been selected as one of the 500 most important wetlands in Japan (Ministry of theEnvironment). In view of the flood damage involving the Ichinomiya River in 1989 and1996, a Special Emergency Project for the Control of Severe River Disaster was
adopted for the river.
Although the project was completed, channel excavation has been continued since 2006
in the lower-reach section near the estuary along the urbanized hinterland city of
Ichinomiya.
This paper reports on the method of determining the cross-sectional shape, to be formedby excavation, of the estuary excavation section using a quantitative habitat evaluation
method. IFIM (Instream Flow Incremental Methodology) is a representative method forquantitative riverine habitat evaluation, but HEP (Habitat Evaluation Procedure)developed in the United States is attracting attention in the area of environmental impact
assessment.
In this study, a simplified version of the HEP was used. Scores were calculated asfollows. (1) Indicator species were selected on the basis of available information andbiological survey results. (2) The value of 1m × 1m mesh areas of habitat for indicatorspecies was rated in terms of an index ranging from 0 to 1. (3) The rating score for an
entire habitat was calculated by summing the indices for individual mesh areas. It was
decided to use a terraced-bank cross section capable of carrying the current design flood
discharge.
Key words : quantitative evaluation method, HEP, river improvement, channel
excavation, Ichinomiya River

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Environmental problems and goals of the improvement of the Aiwari
River
Mitsuru ABE/Noboru MARUOKA/Satoshi DAIMON

Following the flood of August, 1980, of the Aiwari River, a Class B river flowing
through Kitakyushu City, an improvement project for the Aiwari River was launched,
and river improvement works including levee construction and excavation have been
underway from the lower reaches to the upper reaches of the river. In the Aiwari River,
however, an environmental survey was conducted in 2000, and rare plant and animal
species including Limonium tetragonum, a halophytic plant species listed in the
Ministry of the Environment's Red Data Book as a "Threatened II" species, were found.
In this study, the present river environment of the Aiwari River was investigated,environmental problems to be addressed in connection with river improvement wereidentified, and measures to be taken to solve the problems were considered. This paper
reports the results thus obtained.
As a result of the study, on the basis of the environmental problems of the Aiwari River,four goals were identified: (1) conserving the estuary environment that provides habitatfor Limonium tetragonum, (2) creating a wide variety of flows, (3) creating diverse
waterside environments and (4) ensuring of water amenity. To achieve these goals,
methods and implementation zones were proposed for (1) conserving, creating andrelocating the habitat of Limonium tetragonum, (2) forming the base flow channel, (3)creating backwaters and (4) the construction of stepped revetments, etc.
Key words : Aiwari River, channel plan, river environment, Limonium tetragonum,
halophyte, tidal flat, fish habitat, base flow channel, backwater12

On the current state and problems of nature-oriented river works
using nature-friendly methods in Gifu Prefecture
Kazuhiro MORITA/Yoshimasa OTAKEThis paper outlines the present state and problems of the nature-oriented river works
using nature-friendly methods (called "nature-friendly river works" in Gifu Prefecture)
carried out in Gifu Prefecture in fiscal 2006 and reports on what was achieved as aresult of those river works.
In view of the review of nature-oriented river works made in 2005, the Ministry of Land,
Infrastructure and Transport redefined its river management policy from"nature-oriented river works" to "nature-oriented river management" and is planningriver projects that are more nature-oriented than conventional projects. In Gifu
Prefecture, nature-oriented river projects began in 1990. In 2001, the practices at thattime were reconsidered. As a result, the Nature-friendly Method Study Group wasestablished jointly by industry, citizens, academia and the government as a "project forriverfront restoration project," and efforts have been made in the areas of"manufacturing," "human resources development" and "field research." To assist in"manufacturing," the Naturefriendly
Method Certification System was instituted to disseminate information on
nature-friendly methods of river improvement that are effective in conserving, restoringor creating the natural environment and thereby encourage the development of
nature-friendly products. In this fiscal year, the Nature-friendly Method Certification
System was reviewed to identify the present state and problems of nature-oriented riverworks in Gifu Prefecture. As a result, a number of problems were pointed out. For
example, it is often thought that the goal of living with nature can be achieved simply
by using nature-friendly methods without clearly defining objectives to beaccomplished, and river improvement methods that have been successful for other rivers
are used without understanding the mechanism of the rivers to be improved.
Key words : nature-oriented river works, nature-friendly method, review

13River environment as viewed from the results of National Survey onRiver Environments: an overview of the first to third round survey
results
Tetsuya OTSUKA/Satoshi MAEDA/Mitsuru ABE

The third round of the National Survey on River Environment, which began in 1990,
was completed in 2005. In this study, the results of the first to third rounds of the
National Survey on River Environments were reviewed, and the river environments ofClass A rivers were evaluated.
The first to third rounds of the National Survey on River Environments identified 411
fish species, 1,848 species of benthic animals, 3,814 species of plants, 365 species ofbirds, 27 species of amphibians, 20 species of reptiles, 71 species of mammals and12,113 species of terrestrial insects. Thus, the riverine biota has been almost
exhaustively covered, and the survey has shown that rivers are important habitat for
wildlife in Japan.
To evaluate river environments determined according to the results of the National
Survey on River Environments, attempts were made at classifying rivers from theviewpoint of fish, evaluating the water quality environment from the viewpoint ofbenthic animals and evaluating the degree of naturalness of dry riverbed areas. In the
TWINSPAN classification of rivers from the viewpoint of the fish biota, rivers in Japan
were classified into five types: Hokkaido type, East Japan Sea-of-Japan type, East Japan
Pacific Ocean type, West Japan Type I and West Japan Type II. In the study of the water
quality environment by the average score method based on the benthic animal survey
results, the water quality environments of the middle and upper reaches of Class A
rivers were mostly considered excellent. In the study of the degree of naturalness of dry
riverbed areas according to the butterfly index based on the terrestrial insect survey
results, it was concluded that dry riverbed areas in suburban areas retained some
precious pieces of nature. Thus, it has been shown that river environments can beevaluated on a nationwide scale on the basis of data accumulated through the National
Survey on River Environments.
Key words : National Survey on River Environments, river environment, evaluation,
TWINSPAN method, average score method, butterfly index

14

Scoping of project benefit measurement using CVM
Akihiko NAKAYA/Minoru KOBAYASHI/Nobuyuki OHASHI/Mizuki KONNO/Suguru
KATSUMOTO/Aki IWASAKIThis paper reports the results of a fact-based study on approaches to scoping, which isimportant when calculating the benefits of a river environment improvement project by
the Contingent Valuation Method (CVM).
A review of examples of benefit measurement revealed that CVM is often used whenmeasuring the benefits from a river environment improvement project. In CVM, themethod of determining the scope of WTP (willing to pay) measurement greatly
influences benefit calculation. People involved in project benefit measurement,
therefore, are in need of externally justifiable criteria for scoping.
For projects that can be expected mainly to enhance utility value as in the case of a
project for promoting the use of a river, it is appropriate to determine the scope ofmeasurement on the basis of the results of surveys on the use zones of similar existing
projects. In this study, scoping guidelines for different types of projects have beendeveloped according to the results of fact-finding surveys conducted in the use zones ofrivers.
For projects that are expected to enhance not only utility value but also non-utility value
such as projects for nature restoration or water environment improvement, it has been
proposed that the scope of measurement be determined by using the degree ofrecognition of a river of interest as an indicator. It has also been pointed out thatfact-finding surveys should be conducted for each project.
Key words : CVM, benefit, WTP, scope of measurement, river environment
improvement, use zone of a river, the degree of recognition of a river15

Robinia pseudoacacia removing effect of root removal after fellingtrunks and future problems
Kouta TANNO/Satoshi MAEDA/

It is generally known that Robinia pseudoacacia, an exotic species of North American
origin, is highly capable of regenerating even after felling trunks. In order toexterminate Robinia pseudoacacia, therefore, it is necessary either to remove the stumps
and the rhizomes and other underground parts completely or to kill the plants. The
technology, however, to effectively remove or kill the underground parts of this species
has not yet been established. In this study, for the purpose of evaluating theeffectiveness of Robinia pseudoacacia root removal by use of a backhoe, identifying
problems and finding ways to exterminate Robinia pseudoacacia effectively, surveys
and measurements including phytosociological vegetation surveys, sprout density
surveys and sprouting source measurement were conducted in the year after root
removal. On the basis of the study results thus obtained, problems to be addressed andmeasures to be taken were studied, and four field trial plans for Robinia pseudoacacia
regeneration control were developed. These regeneration control plans were carried out
during the period from December, 2006, to March, 2007.
For the study river, the Aka River, a restoration project has been underway since 2005.
Under the project, efforts are being made to remove Robinia pseudoacacia in order torestore the natural vegetation habitat of the Aka River.
Key words : Aka River, nature restoration, Robinia pseudoacacia, root removal,
sprouting16

River channel management and monitoring methods considerate of theecosystem of the upper reaches of the Tone River
Masanori
IIJIMA/Yoshifumi
FURUMATSU/Kikuko MIYAZAKI

KODAMA/Miwa

TOMIZAWA/MasahiroThis paper deals with a method for efficiently monitoring future environmental changes
in the upper reaches (85.5K–186.5K) of the Tone River developed by taking into
consideration such factors as the relationship with channel characteristics and physicalenvironmental conditions, and the historical changes in the river channel.
In this study, the upper reaches of the Tone River were zoned into three sections, namely,
the upper section, the middle section and the lower section, by taking into account thechannel conditions and the environmental elements such as human-made structures. The
ecosystem characteristics of these sections were determined by making use of dataobtained from the results of National Surveys on River Environments, and"characteristic places" were identified by relating fundamental units for evaluating river
space habitat functions with space units (space elements for classifying naturallandscapes). Species dependent on "characteristic places" were identified as"characteristic species," and habitat maps by which to determine the effects of futurechanges in the river environment were created. In addition, in order to enhancemonitoring efficiency and determine habitat functions, typical sections in the three(upper, middle and lower) river sections were classified as reach scale sections andselected as monitoring sites. By studying the monitoring sites thus determined, river
channel management and monitoring methods considerate of the ecosystem of the upper
reaches of the Tone River were developed.
Key words : riverbed degradation, frequency of submersion, habitat map, monitoring
site

17

A study on feasibility of Lake Biwa shore management not dependenton shore-based conservation facilities
Kentaro TAKI/Yoshifumi KODAMA/Takayoshi TSUZUKI/Sadakazu ITO/Yohei KATO

Rapid shore erosion of Lake Biwa began to occur frequently around 1992, and the Shiga
Prefectural Government has been working on the development of lakeshore
conservation facilities designed basically for integrated shore protection (a combinationof jetties, beach nourishment and gentle-slope revetments). However, althoughlakeshore conservation measures are effective in preventing erosion only in the areas
where they have been implemented, there is concern about landscape degradation andadverse effects on the ecosystem caused when the shoreline is stabilized in a
saw-toothed shape. There is a need, therefore, for lakeshore management that does notdepend on lakeshore conservation facilities. It has been pointed out that patterns ofwater level changes and changes in sediment supply from rivers are factors causingchanges in Lake Biwa's shore configuration, the degree to which these factors affectlakeshore configuration has not yet been elucidated.
In this study, a numerical analysis model capable of keeping track of the sedimenttransport process from mountains to rivers and lakeshore areas (from a sediment flow
system to a littoral drift system) was developed to quantitatively evaluate the effect ofeach factor on lakeshore configuration. The newly developed numerical analysis model
was also used to explore possibilities of lakeshore management that is not dependent onlakeshore conservation facilities. As a result, it was found that a dynamic equilibrium
state or a deposition tendency achieved by (1) supplying the sediment deposited at themouths of tributary rivers by bypassing it in the form of littoral drift and (2) keeping thewater level of Lake Biwa at or below BSL+0.3m (BSL=Biwako Surface Level:reference water level of Lake Biwa).
Key words : lakeshore erosion, shoreline, water level fluctuation, the rate of sedimentsupply, sediment flow system, littoral drift system, the state of dynamic equilibrium

18

Development of a river environment management support system
Yasushi HORIKAWA/Satoshi MAEDA/Nobuyuki OHASHI

Information used for river management is diverse and exists in the form of, for example,
electronic data or in print form. Among the river environment-related information, theresults of the National Survey on River Environments have been stored as electronic
data in a nationally standardized format, and the information thus accumulated in an
integrated form is available from a system as searchable and analyzable data. Data on
the results of other river environment surveys, however, conducted for purposes otherthan the National Survey on River Environments have not yet been integrated and madeavailable in the form of a standardized database system. Consequently, it may not be
possible to share and make effective use of data in an organization if different purposesof survey, implementing entities or years of survey are involved, because of data
problems such as scattering, loss, inability to tabulate, perform global checks or search,a lack of preliminary information necessary for a project. In order to enable riveradministrators to make effective use of information, therefore, it is hoped that not only
survey results are made available in a standardized format, but also those survey results
and river environment data collected for different purposes are integrated into a
database system and a system is developed that provides searchable data to otherdepartments in connection with the design, management and implementation ofenvironmental and other facilities.
It was decided, therefore, to develop, by the prototyping model method, a management
support system integrating various functions, such as a GIS-based search function, afunction for chronological management of river environment information maps and adata update and registration function, in order to assist in river management tasks
associated with design, planning and construction by providing a user-friendly interface,
upgrading the database and providing search capability.
Key words : integration and compatibility support system, river environment
information, database, GIS

19

A study on river environment improvement planning from theviewpoint of river system planning: a case study on the Kano River
SystemTakehiko
IWASAKI/Minoru
KAWANABE/Kazuhiro NAMIKI

KOBAYASHI/Koji

TAKAHIRA/Norihiro

In 2005, according to the belief that when planning for the improvement of a riverenvironment, it is important to do so from the viewpoint of the entire river system,
MLIT (Ministry of Land, Infrastructure and Transport) projects for the integrated
improvement of the river system environment were instituted by integrating
environmental improvement projects for rivers and environmental improvement
projects for dam areas. Under the new project system, it became necessary, whensubmitting a budgetary request for a project, to clarify the purpose, necessity, content
and other details of the project by drawing up a long-term plan for the river system
concerned including water environment improvement projects, nature restoration
projects, utilization promotion projects, etc. This study focused on the development of awell-balanced integrated river system environmental improvement plan by looking at,
as a case study, the Kano River in the Kano River System, a Class A river for which ariver improvement plan was formulated in December, 2005.
For the development of the draft plan, the present state and problems of environmental
improvement were identified through literature research from the viewpoints of thewater environment, the natural environment and river utilization, and a direction of
long-term improvement and priority in project implementation were considered while
trying to achieve consistency with the fundamental river management policy and theriver improvement plan. The direction of long-term improvement was considered tomeet the following basic requirements: (1) the conservation of the excellent
environment of the Kano River, (2) the restoration of deteriorating or decreasing
environments and (3) the creation of new environments that are being hoped for becauseof changing social conditions.
Key words : river system environmental improvement project, water environment
improvement, nature restoration, utilization promotion, river improvement plan

20

Application of DNA polymorphism analysis technology to the riverenvironment (interim report)
Kazuhisa KIDO/Katsuhiro GOTO/Jyunzo SAGO/Tatsuo OMURA/Kozo WATANABE

The amendment of the River Act in 1997 added a new objective, namely, environmental
conservation, to the two main objectives, "flood control" and "water utilization," of river
improvement, and a new policy for river administration was indicated. In 2003, theNature Restoration Promotion Act was enacted with the aim of restoring lost
ecosystems and other natural environments. The new law calls for the conservation,
restoration and creation of natural environments in Japan including rivers, wetlands,
seaweed beds, rural areas, forests and coral reefs.
The Convention on Biological Diversity signed at the United Nations Conference on
Environment and Development (Earth Summit) in 1992 views biological diversity atthree levels, namely, ecosystem, species and genetic, and calls for conservation efforts
at those levels.
The conventional practice in river improvement is to evaluate biological diversity at the
species level and plan and implement river improvement accordingly. For better
conservation of biological diversity, however, it is necessary to take into consideration
genetic diversity, which is the genetic variety among individuals within a species, as anindicator of biological diversity, as well as the variety of species. Genetic diversity canbe evaluated by conducting a DNA polymorphism analysis. Focusing on this DNA(deoxyribonucleic acid) polymorphism analysis as a means of genetic diversity
evaluation, this study aims to propose a concrete method of application and otherspecifics.
Prepared as an interim report, this paper reports on the basic studies and analyses
conducted before developing a concrete method of application and, because aconclusion has not yet been drawn, on what has been achieved thus far.
Key words : DNA, heterozygosity, genetic diversity, genetic distance, river environment,
Hydropsyche orientalis

21

A model study on integrated implementation of high-standard leveeand urban redevelopment projects
Toshihiko ITO/Toshiya YAMADA/Junichi NAKAGAKI

Although it has been common practice to implement urban high-standard levee projects
in relatively large areas such as former factory sites, in the coming years it is necessary
to implement high-standard levee projects in areas built up with wooden structures. It isa prerequisite to implement a high-standard levee project in the form of a multipurpose
project combining high-standard levee construction and community development. In
areas built up with wooden structures, however, community development projects are
difficult to implement because the residents of those areas include a high percentage ofowners and leaseholders of small building lots. For those land owners and leaseholders,an urban redevelopment project is an attractive option because it makes it possible tosecure a floor area comparable to that of the existing structures by making intensive useof land. In this study, a model study was conducted on integrated implementation ofhigh-standard levee and urban redevelopment projects.
Key words : high-standard levee, urban redevelopment, cost allocation

22

A study on high-standard levee projects taking advantage of regional
characteristics
Tsuyoshi KONNO/Yoshio MAEMURA/Kiyotaka MATSUMOTO/Jun KOIZUMIThis paper reports the results of a study on what a high-standard levee project in a
suburban area should be like.
High-standard levees have been planned and constructed as integral part of community
planning in view of the future of the riverside community concerned. However, mainly
because of the economic slump following the bursting of the economic bubble and thedeterioration of the finances of the local governments implementing joint projects,
high-standard levee construction, which requires a huge amount of expenditure, has notprogressed as expected.
In recent years, the compact city concept, which, by thinking of the area within walking
distance as the living sphere, aims to prevent urban sprawl, regenerate the community
and make the community a better place to live in, has been drawing attention. In
riverside areas located in the suburbs of municipalities, therefore, the task of riversidecommunity development itself has become difficult to achieve.
In view of this situation, this study focused on the region along the upper reaches of the
Ara River that is located in the outskirts of the municipalities along the river and that
includes many urbanization control areas. In the study, urban facilities that can be
developed together with high-standard levees were identified, taking into consideration
the river characteristics, and problems expected if a joint project is to be implemented
were studied.
Key words : high-standard levee, riverside municipality, joint project, community
development, urban facility

23

Seismic performance regulations of super levees under level 2
earthquake motions
Hiroshi MORI/Yoshifumi KODAMAIn March, 2007, the Ministry of Land, Infrastructure and Transport issued the guideline
for the verification of the seismic performance of river structures including conventional
levees (earthen river dikes) under level 2 earthquake motions. There is an urgent needfor studies on similar verification of the seismic performance of super levees and theestablishment of an evaluation method.
This report introduces an approach to the determination of seismic performance
regulations for super levees built on liquefiable ground under level 2 earthquake
motions. The accuracy of a seismic analysis method (dynamic deformation analysis)that can be used to evaluate seismic performance was made either by comparison withdamage sample data and centrifuge model test results or by finite element mesh density
evaluation in connection with the influence on surface displacement or inclination. As aresult, it has been shown that the analysis method is capable of reproducing actual
failure behavior with fair accuracy. As an alternative to the factor of safety evaluationby the seismic coefficient method, which tends to overestimate the factor of safety, aseismic design verification flow for evaluating seismic performance in terms ofdeformation, one of the seismic performance attributes of levees, is presented.3
Key words : level 2 earthquake motion, super levee, seismic performance regulation,
seismic analysis method

24

Riverfront utilization efforts for the Ota River
Fumihiro TOI/Yoshifumi KODAMA/Takayoshi TSUZUKI/Isao SHIOMI/Hiroshi INO

The city of Hiroshima, which has been formed by the delta of the Ota River, ischaracterized by as many as six rivers running through its urban center, a rare
topography in Japan. The percentage of water surface in the urban area is one of thehighest among the cities in Japan. As a city of water along with Osaka, Hiroshima ismaking pioneering efforts to create a city taking advantage of its rivers.
On March 23, 2004, a government circular titled "On Exceptional Measures under theRules for Permitting the Use of River Zones for Facilities for the Restoration of Cities
and Other Areas" was issued in connection with urban restoration projects and regional
restoration programs that have been underway in recent years. Thus, it has become
possible make flexible use of various systems associated with the use of river zones inorder to enhance the utility value of dry riverbed areas and promote community building
efforts taking advantage of riverfront space. This means that it has now become possible
for private enterprises to hold various events and run commercial establishments such as
open cafes in river zones, all of which were not permitted under the old regulations.
This paper reports the impact of a social experiment that has been conducted since lastyear on the exceptional measures under the rules for permitting the use of river zones of
the Ota River in Hiroshima City.
Key words : rules for permitting the use of river zones, social experiment, Ota River,open cafe

25Planning for maintenance cost reduction by allowing private use of aregulating reservoir
Kenichi YAMAKI/Hideyuki WATANABE ／ Toshikazu ASANUMA ／ Shingo
SHIINAThe Osagami Regulating Reservoir, which is under construction in the city of
Koshigaya, Saitama Prefecture, is a facility designed for the flood control of the
Motoara River, a tributary of the Naka River in the Tone River System, and for theretention of stormwater runoff due to the land development carried out for the Specified
Land Readjustment Project for Koshigaya Lake Town. One characteristic of thisregulating reservoir is that it serves as an artificial lake in normal times to create anamenity-oriented waterfront environment.
It is important that this regulating reservoir retains its excellent waterfront space in the
coming years.
A plan has been developed, therefore, for minimizing the maintenance cost and laborburden on the government while maintaining the high standard of river space
management for the regulating reservoir.
Key words : Koshigaya Lake Town, Osagami Regulating Reservoir, waterfront space,maintenance, cost reduction, use permitting rules, social experiment26

A study on development of inland waterway transport
Katsuhiro GOTOU/Kazuyuki SAKANOI ／ Jun MOTOHASHI

The role of inland waterway transport (including river navigation and coastal shipping )(IWT) is being reconsidered from the viewpoints of environment-friendly andenergy-efficient , easing traffic congestion, ensuring emergency transportation functionsin the event of disasters, and supporting tourism and recreation activities.
The purpose of this study is to identify current trends and problems of IWT in Japan andindicate a direction toward development of IWT from the viewpoints of normal use andemergency use. In normal times, IWT can be used to transport dangerous goods andwaste materials in order to contribute greatly to the mitigation of urban environmental
problems. In emergency times, there is a possibility that IWT is useful to transport
emergency relief goods, stranded commuters, and debris of earthquake-damaged
structures. A case study of the Ara River showed that IWT can contribute, to somedegree, to relief activities for the riverside municipalities.
As a next step, it is hoped that practical problems on promoteing the use of IWT are
identified, methods of partnership of the organizations concerned are clarified, and therole and effectiveness of IWT are publicized, through social experimentation.
Key words : inland waterway transport, logistics, disaster management, regional
development, emergency jetty, social experimentation, World Water Forum27

Study on global warming countermeasures in riverside urban areas
Masafumi ITO/Yoshio MAEMURA/Hideki TAMURA

During the one-hundred years ending in 2004, the heat island effect resulting fromdecreases in vegetative cover and increases in artificial land cover including buildings
has caused the annual mean temperature in large cities in Japan such as Sapporo, Tokyo,
Nagoya and Fukuoka to rise by 2.2 to 3.0°C. These temperature rises have become amajor social problem because they are 1 to 2°C greater than the rises in annual mean
temperature in medium and small cities in the country.
In view of this situation, micrometeorological observation was carried out in areas along
the Ara River in Kagaguchi City (Saitama) and in Akabane (Kita Ward, Tokyo) with theaim of investigating the effect of river areas such as river water surfaces and high water
channels, in which the rate of evapotranspiration is higher than in land-side areas, on the
mitigation of temperature in riverside urban areas. This paper reports the results of the
micrometeorological observation.
The observation results confirmed the temperature-lowering effect, taking into
consideration of the river space of the Ara River and the surface cover provided by thehigh-standard levees, and cool breezes confirmed the temperature-lowering effect inland-side areas, along with the extent of such influence and its changes over time.
Key words : high-standard levee, heat island effect, micrometeorological observation,
temperaturelowering effect28

Evaluating the hydrological cycle conservation system for Hachioji
New Town by using the SHER Model
Hideki TAMURA/Yoshio MAEMURA/Daikichi OGAWADA

Prior to the full-scale construction work for the Hachioji New Town project being
implemented by Urban Renaissance Agency, the Committee on the Hydrological Cycle
Conservation System for Hachioji New Town (chaired by Prof. Katsumi Musiake ofFukushima University) was established to deliberate on ways to reduce the burden on
the hydrological system caused by the large-scale urban development planned for the
project. As a result, the committee developed a hydrological cycle conservation system(hereafter referred to as "the System").
The development of Hachioji New Town has been carried out in accordance with thepolicy of the System. The development has now reached the final stage, and various
facilities planned as part of the System are nearing completion. In order to verify theeffectiveness of the System, the committee met again to evaluate the effectiveness of thehydrological cycle conservation system quantitatively by using the SHER Model, a
distributed hydrological model. This paper reports on the quantitative evaluation of the
System made by the committee.
The effectiveness of the System at a certain point in future when land use plans arecarried out and the planned amount of development to be handled by the System iscompleted was estimated. As a result, it was concluded that the goals of the flood
control plan and the plan for low-water river works could be achieved at thedownstream end of the Hyo-e River in the project area. It has therefore been shown that
it is important to continue the system development according to the current plan.
Key words : new town development, hydrological cycle, hydrological cycle
conservation system, distributed hydrological model, SHER Model, stormwater
infiltration facilities, storage facilities, crushed-stone storage and infiltration facilities

29

Policy for measures against washed-up trash
Muneaki MASUOKA /Yoshifumi KODAMA/Hideki TAMURA/Tetsuro SHIBATA

In coastal areas in Japan, damage caused by trash washed ashore, such as hampering thefunctions of coastal conservation facilities and degrading coastal environments, has
become a serious problem that requires urgent countermeasures.
In this study, problems associated with washed-up trash were identified by investigating
the actual state of washed-up trash and evaluating current coastal management practices
in dealing with washed-up trash, and a policy for measures against trash washed ashore
was drawn up.
In order to investigate the actual state of trash washes ashore in Japan, a nationwide
survey on washed-up trash was conducted intensively over a period of about month toprevent recounting trash washed ashore twice or more. This was the first attempt of its
kind in Japan.
Key words: coast, beach, shore, washing ashore, trash, environment, life, citizens, NPO,
cooperation, mutual assistance30