ENVIRONMENTLighten the load
Reservoir sedimentation problems are common the world over in both developed anddeveloping countries. In this article, Sameh A Kantoush, Tetsuya Sumi and Yasuhiro
Takemon from Kyoto University, explain how Japan is putting its experience to good use
and promoting good reservoir sedimentation management for the future.

T

Sediment Utilization

Sediment Property

HE catastrophic hydro-geomorphologSuspended load +Wash load +Damical events associated with earthquakes
bed loadsuspended loadand volcanic eruptions, landslides, debris
ForestBottomset
bed
Topsetbedflows and slope collapses are the major
bed
H.W.L.
sources of sediment production in Japan, and are
the most serious disasters among all water-relatd
L.W.L.
ende
ed ones. In Japan, the annual average loss of life
susp
s
,
d
a
e
lo d
B
from landslide hazards is 170, which tragically is
ash
nd w
Wash
a
Delta
set to increase after the country’s disaster of 11
Downstream
load
March 2011. Japanese rivers are characterised byareahigh sediment yields due to topographical, geological
Midstream area
Upstream areaand hydrological conditions. This has consequently
caused sedimentation problems for many reservoirs
constructed for water resource development or flood
control purposes. A significant amount of sediment
Soil
Main component:
Main component:
Main component:
storage capacity at the reservoirs, which was designed
Classification
Clay and Silt
Sand
Gravel and Sandfor 100 years, has already been lost because sedimenAverage size grain
Gravel = 3, Sand = 11
Gravel = 12, Sand = 41
Gravel = 28, Sand = 43
tation has occurred faster than expected.
distribution (%)
Silt = 50, and Clay = 37 Silt = 32, and Clay = 15
Silt = 21, and Clay = 8
Reservoir sediment management has become necessary in Japan: to prevent the siltation of intake
Fine grained
Fc = above 90%
Fc = about 50%
Fc = under 30%
fraction, Fc
facilities and aggradation of the upstream river
bed in order to secure the safety of dams and the
Natural water
w = above 100%w = about 50 to 60%
w = under 40%
content, w
river channel; to maintain the storage function ofreservoir, and ensure sustainable water resource
Density Porosity
Low
Highmanagement for the next generation; and to release
Ignition Loss Ig
Ig = about 10%
Ig = about 7%
Ig = about 4%
sediment from dams with an aim to conduct comprehensive sediment management in a sediment
Organic materials
LowHightransport system.
/Nutrient
Currently, Japanese reservoir sedimentation manFor construction
Soil improving material,
Aggregate, base course,
agement is embarking on new methods. In additionbanking material,
landfill, planting base etc
to conventional techniques sediment replenishment,
For agriculture
fertilizer, etc
sediment flushing and sediment bypass techniques
For ceramic industry
are being adopted at some dams: eg at Murou Dam
Ceramic soil,
River supply, artificial
brick cement etc
beach replenishment,
on Uda river, Unazuki and Dashidaira Dams on the
For environment
wetland restoration etc
Kurobe river, Miwa Dam on the Tenryu river andAsahi Dam on the Shingu river.
In order to solve long term environmental problems in relation to water resources, the influences Figure 1: Delta formation and properties of deposited sediments within reservoirs and applicationsof geo-, eco- and socio-system changes on water of different types of sediments
resource systems have been analysed in our laboD ams and sediment production
ratory from a risk management perspective. Integrated river basin
management which harmonises flood control and water use with The modern development of Japanese dams can be traced back overenvironmental conservation is also being studied. We are working on 100 years. Dams were built originally for the utilisation of water
several subjects such as: asset management of dams and development for water supply and agricultural purposes. With subsequent ecoof reservoir sediment management methods; model development of nomic development however, several other functions were added
eco-sediment hydraulics by habitat structures analysis; and interac- such as hydro generation, industrial water use and flood control At
tion between the aquatic environment and ecological systems.
present, multipurpose dams make up the majority of Japanese dams.
To establish effective integrated river basin management measures, Approximately 3000 dams over 15m in height have been constructed
several monitoring techniques have been developed and implemented but the total reservoir storage capacity is only 1Bm3 (Sumi, 2003).
at different dam projects. In Japan, a comprehensive approach has
Japan’s topographical, geological and hydrological conditions
already been adopted for sound sediment circulation in the sediment have great impacts on sediment yield in river basins. There aretransport system, which is achieved by moving sediment from moun- two large fault lines, the Median Tectonic Line and the Itoigawatains through to the coastal areas.
Shizuoka Tectonic Line, where weathering is proceeding in particular.

38

may 2011 INTERNATIONAL WATER POWER & DAM CONSTRUCTIONUTTARAKHAND JAL VIDYUT NIGAM LTD.
H.O, “UJJWAL” Maharani Bagh, GMS Road, Dehradun-248006(Telephones- 0135-2763508, 2763808, 2763508)

SHORT NOTICE INVITING BIDSFORRENOVATION, MODERNISATION AND UPGRADATION OF (3x10 MW) KULHAL HYDRO-ELECTRIC PLANT DISTRICT DEHRADUN IN UTTARAKHAND, INDIA
THROUGH
INTERNATIONAL COMPETITIVE BIDDING (ICB) ROUTENIB No: - RMU (YV)/2010-11/01
Dated.25-03-2011
1. Uttarakhand Jal Vidyut Nigam Ltd., a Public Sector Undertaking of the State Government of Uttarakhand in India, invites Single-Stage Sealed Three-Envelope bids
from eligible bidders through International Competitive Bidding (ICB) route for Renovation, Modernization and Upgradation of (3x10 MW) Kulhal Hydro-electric Plant
in Dehradun District in the State of Uttarakhand in India.
2. SCOPE OF WORK:
Refurbishment/Replacement of:g
Vital parts of the generating units such as turbine runner blades, guide vanes, governors and excitation system, stator and rotor etc., Station Auxiliary Systems.
g Hydraulic Steel Structures, Civil Works.
The work of RM&U shall include reverse engineering, design and engineering, manufacture, shop fabrication, assembly, testing and inspection at Supplier's works,
packing, loading and forwarding, dispatch, delivery at site, unloading and storage at site, insurance, handling at site, complete erection, including a s s o c i a t e d c i v i lworks, testing, start-up, commissioning, successful performance testing and handing over of all facilities.
3. GENERAL DETAILS
3.1 Bid Security
INR 23.1 Million (Indian Rupees Twenty Three Million and One Hundred Thousand only)
3.2 Cost of bid documents
INR 100,000.00 (Indian Rupees One Hundred Thousand only) in the form of Demand Draft / Bankers Cheque drawn in favour of"Uttarakhand Jal Vidyut Nigam Ltd." ,( STATE BANK OF INDIA, Account no. 30024638487) and payable at Dehradun, plus applicable
Trade Tax. Presently, Trade Tax is13.5%.
3.3 Commencement of sale of bid documents/Date of start of downloading of bid documents : 15-04-2011
3.4 Date for Pre-Bid meeting : 25-05-2011
3.5 Last date/time for submission of bids : 26-07-2011 upto 1200 hours, Indian Standard Time (IST)
3.6 Date/time of opening of Techno-commercial bids : 27-07-2011 at 1100 hours, Indian Standard Time (IST)
3.7 Validity of bid : 180 (one hundred eighty) days from the date of opening of Bids.
3.8 Date of execution and completion: 3 (three) lean seasons, starting from October 01, 2011 to May 31, 2014.
4. For Detailed Notice Inviting Bids, Scope of Work, Qualifying Criteria, and other details, prospective bidders are requested to visit "Uttarakhand Jal Vidyut Nigam
Ltd." website www.uttarakhandjalvidyut.com. Bid documents may be downloaded from Uttarakhand Jal Vidyut Nigam Ltd. website, for which an amount of INR
100,000.00 (Indian Rupees One Hundred Thousand only) plus applicable Trade Tax, towards cost of bid documents in the form of Demand Draft / Bankers' Chequedrawn in favour of "Uttarakhand Jal Vidyut Nigam Ltd.", (STATE BANK OF INDIA, Account no. 30024638487) and payable at Dehradun, shall compulsorily accompany
bids. Alternatively, bid documents may be obtained from the following Offices of Uttarakhand Jal Vidyut Nigam Ltd. on payment of INR 100,000.00 (Indian Rupees One
Hundred Thousand only) plus applicable Trade Tax towards cost of bid documents, in the form of Demand Draft / Banker's Cheque drawn in favour of "Uttarakhand Jal
Vidyut Nigam Ltd.",( STATE BANK OF INDIA, Account no. 30024638487) and payable at Dehradun:g General Manager, (E&E), Uttarakhand Jal Vidyut Nigam Ltd., Ganga Bhawan, Yamuna Colony, Dehradun- 248001, Uttarakhand, India
g Deputy General Manager (M&U), Yamuna Valley, Uttarakhand Jal Vidyut Nigam Ltd., Dhalipur -248142, Dehradun, Uttarakhand, India
g Manager (A&S), Uttarakhand Jal Vidyut Nigam Ltd. , Ujjwal, Maharani Bagh, GMS Road, Dehradun-248006, Uttarakhand, India.

“Avoid wasteful use of Electricity”

Dy. General Manager
M&U - Yamuna Valley, Dhalipur,
Uttarakhand Jal Vidyut Nigam Ltd.
Dehradun, Uttarakhand, INDIA

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Water Power& DAM CONSTRUCTIONMARCH 2010

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MARCH 2010

NEW TECHNOLOGYNEW TECHNOLOGY

March 2009 saw us obtain Lloyds approval for the completed
structural designs and the electronic and electrical designs were also
finalised. The construction of the Proteus demonstrator itself began
in the middle of last year with the finished device currently being
moved to the Humber (February 2010).

The Proteus generator under construction

A NATOMY OF A TIDAL POWER GENERATOR
Weighing more than 150 tonnes and stretching to around 20m
long, with a beam of 14m, the full-scale demonstrator of theProteus NP1000 consists of a steel hull, vertically mounted turbine,and buoyancy chambers. The vertical shaft within the Neptune
Proteus connects to a 1:200 gearbox and generator in the deckhousing. Associated valves and electrical and electronic processing
and control for the Proteus are mounted onshore, connected by afloating cable-bridge.
Looking at the Proteus’ turbine in more detail, this is a 6mx6m
vertical axis cross-flow design which is mounted within a patented
symmetrical Venturi diffuser duct below the steel deck. A cross-flow
turbine – such as that adopted in the Proteus – is a radial free stream
turbine and due to its specific speed is classified as a slow-speed turbine. Practically, guide vanes impart a rectangular cross-section to thewater jet which then flows through the blade ring of the cylindricalrotor, first from the outside inward and then – after passing throughthe inside of the rotor – from the inside outward.

A powerful proposition
Jack Hardisty is the technical director of Neptune Renewable Energy in the UK. Here he
explains why tidal stream power is a serious contender in the renewable energy field

Developments in tidal stream technology

W

HEN it comes to discussions on green energy it is all
too easy to overlook tidal stream power when set
against the high profile rollout of other renewablesources of energy such as wind, wave and solar. The
reality, however, is that tidal stream, on a cost benefit analysis,stacks up extremely well against the alternatives and is increasingly being looked upon as a serious contender in the renewableenergy field.
The fact that, to date, tidal stream has been largely untapped canbe attributed to a number of factors, particularly the need for proofof-concept devices to be developed and trialled, something which is
now happening on the ground. A major advantage with tidal streams
is their predictability, which means we can forecast output to a highdegree of accuracy and for many years into the future. The capacity
factor is therefore fully determinant. The utilisation of sheltered estuarine sites, which nevertheless evidence strong tidal streams, provides
ease of maintenance compared to wind or wave with a significant
reduction in O&M costs.

New concepts in pumped storage

Fish ladder construction

Serving the hydro industry for over 60 years
001wp0310fc_v3_CS.indd 1

11/3/10 08:25:39

C OMMERCIALLY SUSTAINABLE
Thankfully, things are changing and, after considerable time andeffort, tidal stream energy has now reached the stage where it
can be offered at a commercially sustainable level. For our own
part, at Neptune Renewable Energy Ltd (NREL), we have beendeveloping a tidal stream power capability for the past five years.
Building on an intensive research and development process, wehave reached a major landmark with the announcement that weare in a position to deploy the first full-scale demonstrator of ourvertical-axis Proteus tidal stream power plant in the Humber
Estuary at Hull, England.
The Proteus, to be moored in the Humber for an initial threemonth trial, features a lightweight exoskeletal structure. It has

12

012_014wp0310neptune_CS.indd 12

NEW TECHNOLOGY

View inside the tidal power generator

C ONTROLLING THE FLOWW HY THE H UMBER ?

The device’s rotor is maintained at optimal power outputs by setsof computer-controlled shutters within the duct and by the variable
electrical load.
Focusing on the patented flow control shutters on the Proteus, thesemaximise the area of water hitting the turbines to increase torque andpower output.
Crucially, the efficiency of all turbines depends upon the tip speed
ratio (TSR), specifically the ratio of the tip speed to the fluid speed.
In the case of the vertical axis, cross-flow rotors on Proteus, maximum efficiencies are achieved at TSR =0.35. The computer controlled
shutters direct the flow at variable angles onto the blades in order tomaintain this optimum TSR regardless of flow speed and thus maximise the electrical output.
Within the Proteus, the axle torque is taken by a right angle gearing to 2 x 250kW permanent magnet DC generators and then, via
industrial regenerative drives and control systems, cabled ashore andgrid connected.
Theoretical work and laboratory experiments, suggest that we will
be able to realise an overall efficiency for the Proteus in situ of greaterthan 25% and, potentially, generate 30% more electricity compared
to traditional hydro designs.

Power from Proteus

The Humber Estuary for the first deployment of Proteus as its depth
and tidal flow is considered one of the best locations in the British
Isles for tidal stream power, whilst also being relatively close to ourbase in North Ferriby, East Yorkshire. The Humber has also been
identified consistently as one of the key areas of concentrated tidal
stream power potential in British waters, a case in point being the UK
Atlas of Offshore Renewable Energy Resources (2004) published onbehalf of the DTI (Department of Trade and Industry).
Another benefit of the Humber area was that we were able tocall upon the expertise of local naval architects IMT Marine, engineers Water Hydraulics, Ormston Technology in Beverley and Dane
Electrical Engineering in Scarborough.
Once deployed we anticipate that the advanced Neptune Proteus
NP1000 will generate at least 1000MWh/yr - this is based on a peakspring tidal stream site of about 3m s-1.

M UNICIPAL SUPPORT
Throughout the process, at a municipal level, Hull City Council
has been extremely supportive of our efforts and this type of backing is a key consideration for any project of this type. The Council
can clearly see the economic and practical benefits of Proteus andhave already agreed that the output from the demonstrator will
help to power The Deep Submarium (an aquarium tourist attraction in Hull).
Upon the completion of the demonstrator trials, the aim is to havethe world’s first tidal stream power array, consisting of advanced
Proteus designs, up and running close to The Deep in the Humber
during 2011-12. When it comes to the environment, as the Proteus
is a moored system, so the demonstrator will have a minimal impact
when located in the Humber. Also, the bulk of its steel and composite
construction can be recycled in the future.

T ESTING TIMESThe Proteus demonstrator

The demonstrator will be deployed in the Humber Estuary

been specifically designed for estuarine sites where there are not
the problems, and stresses, associated with wave activity but
which nonetheless exhibit powerful currents and have the advantage of lower access, cabling and maintenance costs comparedwith offshore environments. Looking at the potential to roll-out
Proteus, we consider that there are at least 10 estuarine sites in
Britain with peak spring currents of more than 2.5m/s-1 which
could quite comfortably support this technology. There are, literally, hundreds of suitable sites worldwide.
As highlighted, the major benefit offered by tidal stream power isthe delivery of a predictable source of renewable energy compared tomore variable, less consistent, options such as wind. Certainly thisreliability has to be seen as a key benefit when it comes to the supplyof energy to individual sites and also to the national grid. Crucially,
once moored in the free stream, the state-of-the-art Proteus is able towork equally well in ebb and flow currents.
Work on the £2M (US$3M) full-scale Proteus NP1000 demonstrator was undertaken over six-months from May 2009, with 25
shipyard workers involved in the construction phase. The completed
unit is in the process of being transferred to Hull with commissioning
anticipated shortly thereafter.
The patented NP1000 device, which once in place is scheduled togo through in-situ tests on the Humber, is the culmination of five
years of intensive effort by the team at Neptune and our partners.
Key landmarks in the development process over this time include:
the design, construction and testing of 1/10 and 1/40 scale tankmodels. During the first-half of 2007, computational fluid dynamics(CFD), mathematical and physical modelling resulted in a numberof design modifications. By 2008 we were ready to seek investment
for the full-scale demonstrator. With sufficient funding in place,

MARCH 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

11/3/10 09:02:23

WWW.WATERPOWERMAGAZINE.COM MARCH 2010

012_014wp0310neptune_CS.indd 13

Extensive model tests at the University of Hull’s Total Environmental
Simulator Research Facility have allowed the design to be continuously refined and optimised in a number of crucial ways to reach thestage of the Mark III design of the Proteus NP1000. The Mark I version was constructed at 1/10 scale and tested in the tidal River Hull.
Detailed CFD analysis was then conducted to refine the rotor andduct design with the result that, for a Mark II version, the rotor wasredesigned and duct angle reduced by seven degrees. Also, a single
deflector plate was replaced by two sets of three vertical shutters to
direct the flow close to the optimum angle of 16 degrees onto therotor. Further enhancements introduced for the Mark III (patented)
design of the Proteus NP1000 focused on the rotor, ducts and buoyancy chambers.

O PERATIONAL AND COST BENEFITSE NERGY PRODUCTION
Cost engineered for estuarine energy production the Proteus offers
considerable practical benefits including:13

11/3/10 09:02:41

At this stage we are not aware of any similar device which is designed
to capture the shallow water resource at significantly lower capitaland O&M costs. Certainly, a major innovation is the cross-sectional
shape that has been adopted by our patented design. In the Proteus’square turbine cross-section 30% more electricity per unit channel
width is generated compared to circular turbines. Additionally the
CFD tested and patented flow control shutters adopted, with their
computer control, are able to increase the impacted length of theflow on the turbine to almost half of the circumference, thus increasing shaft torque and power outputs.
When it comes to operation and maintenance, all Neptune turbine
components have been designed to be serviceable on site except for
the lower bearing which can be serviced and replaced with local drydocking. Crucially, the device can be towed to site using a small tug.
Overall, we believe that our Proteus device delivers reduced capitaland operation and maintenance costs and, as a moored system, its
environmental footprint is low – making it an attractive option inparticularly sensitive locations.

F ACING THE FUTUREU Generating electricity at both capital and operating costs that are
significantly less than other tidal stream power devices and comparable to onshore wind.
U Greater proximity of the generating capacity to the grid or distribution supply points.
U Ability to be moored in relatively sheltered locations meaning that waves
are not impacting on the structure, with the potential for damage.
U Being close to land means simpler installation (including cabling)
and maintenance.

14012_014wp0310neptune_CS.indd 14

The future for Neptune Renewable Energy and Proteus is extremely
bright, especially in light of the growing focus on renewable power
generation in the wake of the Copenhagen summit. This technology can be successfully expanded and applied to other sites in the
UK. It can also be looked at as a practical power proposition forlocations worldwide. IWP & DC

For more information on Neptune Renewable Energy Ltd(NREL) please visit www.neptunerenewableenergy.com
MARCH 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

11/3/10 09:02:57

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R eservoir sedimentation in Japan

Top: Figure 2; Relationship between reservoir sedimentation rate and years
after dam completion. Above: Figure 3; Relationship between annual storage
capacity loss and gross storage capacity

Weathering is also seen in many other regions. The annual average precipitation is approximately 1700mm, and sometimes intensive rainfall
such as 100mm in an hour or 200-500mm in a day can be recorded.
Consequently reservoir sedimentation has been accelerated especiallyin the Chubu and Hokuriku regions in the centre of the main island.
Reservoir sedimentation problems in Japan originated with siltation at power plant intakes at small hydro projects on the mainstream,
and then scoring gates were set up as a countermeasure. Later on as
sedimentation proceeded to affect medium sized dams, the increased
flood risk caused by sedimentation at the upstream channel of reservoirs became an object of public concern, and the importance of
sedimentation management was recognised on a nationwide scale.
Storage capacity can be secured without difficulty at run-of-riverprojects. However, maintaining storage capacity becomes a major
issue at hydropower and flood control dams.
When estimating design sediment storage capacity, various proposed
equations (on the basis of topography, geology or reservoir capacity)and the actual sedimentation records of neighbouring dams or erosion
control dams have been referred to. However, in some cases, because
the amount of inflowing sediment was assumed to be significantly
large, a sediment storage capacity of less than 100 years (eg 30 or 50
years) had to be used. And in other cases, where a 100-years design
sediment storage capacity was secured, the actual sediment yield largely
surpassed the originally estimated sediment yield. Consequently, more
sediment has already accumulated than the design sediment yield andactive storage capacity is decreasing year by year.

Figure 4: Sediment management strategies in reservoirs

40

In Japan, following the widespread recognition of sedimentation
problems, all dams with a storage capacity over 1Mm3 have been
obliged to report their sediment condition to the authorities every
year since the 1980s. As of 2000, 877 dams (one-third of all damsin Japan), reported annual changes in sedimentation volume and theshape of accumulated sediment. Such a nationwide survey with accumulated data is regarded to be a valuable asset on a global basis.
Reservoir sedimentation is a complex process which differs foreach river and reservoir. However, it is almost characterised by thedelta formation as shown in Figure 1.
The schematic view of Figure 1 has been drawn by field boring dataof 30-40 reservoirs in Japan. After flowing into a reservoir, sedimentforms a delta composed of deposits graded according to the deposition characteristics of the reservoir (JDF 2003). As shown, the longitudinal profile of sediment deposits is not necessarily horizontal; areas
at higher elevations are more prone to such phenomena as a reduction in effective capacity and backwater formation. Coarse sediment
composed mainly of gravel and sand deposited in the upstream zoneof the topset bed is not easy to move by lowering the reservoir waterlevel or dredging the shoulder region of the midstream zone.
Figure 2 shows the relationship between reservoir sedimentation
rates and the ageing of dams. Here, the sedimentation rate is calculated using sedimentation volume to gross storage capacity. Withdams constructed before World War II and used for more than 50
years, sedimentation proceeded in the range from 60 to beyond 80%
in some hydroelectric reservoirs. Likewise, for the dams constructed between 1950 and 1960, or from the postwar years of recovery
through the high economic growth period and used for more than 30
years, sedimentation rates beyond 40% were found in many cases.
The influence of sedimentation in those hydroelectric reservoirs
depends on the type of power generation.
Following this period, large numbers of multi-purpose dams wereconstructed. This type of dam does not have high sedimentation
rates compared with hydroelectric ones, although the rates of 20%
to beyond 40% were found in some dams. Since maintaining storage
capacity is directly linked to maintaining the function of dams suchas flood control, the influence of sedimentation in the multi-purpose
reservoir becomes greater.
Figure 3 shows the relationship between the annual storage capacity loss and the gross storage capacity. The annual storage capacity
loss generally decreases with an increase in the gross storage capacity and the reservoir life is extended. Figure 4 shows the relationshipbetween the annual storage capacity losses and specific storage capacity(mm), which is defined as a ratio of gross storage capacity to catchment area. Many multipurpose dams have specific storage capacitiesof 50-1000mm and annual storage capacity losses of approximately
1.0 to 0.1%. The schematic diagram of Figure 4 shows how suchcomprehensive sediment management is undertaken and classified in Japan. It can be summarised into the following three points(Kantoush and Sumi, 2010):
1) To prevent the siltation of intake facilities and aggradations of the
upstream riverbed to secure the safety of dams and river channel.
2) To maintain the storage function of reservoirs and realise sustainable water resource management.
3) To release sediment from dams. A new policy in Japan in relation
to comprehensive sediment management is a sediment transportsystem. The amount of sediment supplied from rivers to coasts wasradically reduced with the construction of erosion control Sabodams or storage dams in mountain areas, and acceleration of aggregate excavation from riverbeds after World War II. As a result, various problems arose including riverbed degradation in downstream
channels, oversimplification of the river channel, and retreat of theshoreline due to the decrease in sediment supply to the coast.
Sediment of approximately 200Mm3 is produced from mountainous
areas every year. A volume of 100Mm3 is deposited in reservoirs, andthe remaining 100Mm3 is discharged into downstream rivers.
In the latter, 4Mm3 is allocated for gravel excavation. From
1950-60, however, a considerable amount of aggregate was taken sothat the amount of sediment supplied to coasts through estuaries was
APRIL 2011 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

Environment

remarkably reduced. Regarding the sediment budget for sand along
the coastline, erosion (350,000m3) surpasses deposition (250,000m3)
and therefore coastal erosion is still proceeding. At present, it is said
that eroded coasts account for approximately 60% of the Japanese
shoreline of about 34,000km. Furthermore, approximately 40% ofsuch erosion is attributed to the decrease in the amount of sedimentsupplied from rivers, including reservoir sedimentation.
A sediment transport system represents a target region for management, in which attention is focused on the movement of sedimentfrom mountainous regions to coastal regions, compared with a water
system representing the conventional movement of water. There is a
growing need for the broad-based management of sediment, which
covers mountain sediment supply through the downstream river
channel and coastal region.

M onitoring techniques
In order to evaluate environmental influences and the effectivenessof sediment management measures, such as sediment replenishment,
sediment flushing and sediment bypassing, various types of sedimentmonitoring techniques should be developed. Here, new measurement
techniques for suspended sediment concentration, surface velocities,
and sediment morphological changes such as sediment erosion anddeposition in reservoirs are introduced.
Suspended sediment concentration
Monitoring the quantity and the quality of sediment transport during
flood events in rivers and reservoirs is very important. Automatedmeasurement of suspended sediments (SS) is crucial to the study of
sediment transport. We have developed and implemented various
SS monitoring techniques for both continuous turbidity measuring(SMDP, turbidity, and image processing techniques) and bottle sampling for calibration. SS monitoring systems based on a differential
pressure transmitter (SMDP) were implemented in Miwa, Unazuki
and Dashidaira dams. The turbidimeter that uses optical backscatter and relates nephelometric turbidity unit NTU to SS is known forcontinuous and automated field sampling, were installed for sediment monitoring in the Kurobe river. Digital optical cameras recorded
the sediment-water mixture in-situ, to determine the SS. We used amethod to measure SS which relates light intensity with SS in theflow, and is considered linearly correlated with SMDP measurements.
A calibration procedure was carried out for the camera and for eachsingle pixel in the region, to establish the relation between SS and thevalues of gray scale in the frames representing light intensities. Almost
every two seconds, measurements for SS and SMDP measurements
were correlated with corresponding images. The same calibration
procedure was applied to all pixels in the region of analysis. The estimation of pixels density is made by DigiFlow software.
Two dimensional surface velocity
Large-scale particle image velocimetry (LSPIV) is an extension of aquantitative imaging technique to measure water surface velocities.
In the present applications we utilised the monitoring video camera,
CCTV (CIT-7300) from Mitsubishi Electric Corporation. The camera
was connected with a computer to record the data directly. The flow
videos recorded at 30fps and 740 x 480 pixels. Naturally occurring
turbulence, sediment clouds, differences of water colour and bed
feature reflections on the flow surface were used as seeding tracers.
The combination of these tracers is present during floods or sediment
bypassing in reservoirs and tunnels as well.
Three dimensional sediment deposition and morphology
Laser scanning uses surveying techniques to generate digital terrain
models (DTMs), a fundamental tool to detect, classify and observemorphological changes in river channels during and after sedimentmanagement. The 3D reconstruction of the terrain with Reigle laser
scanning methods is one of the modern ways to reproduce the natural
surface of the ground with high accuracy and high automation. Such amethodology offers the advantages typical of noncontact techniques,
and moreover permits to collect in short time dense 3D point clouds
WWW.WATERPOWERMAGAZINE.COM may 2011

over the surface of interest, to record a perspective image (intensity
data and sometimes RGB data).
There are various terrestrial laser scanners available, characterised by different accuracy, measurement range and speed of dataacquisition. The distance is measured applying different principles:
the time-of-flight principle (ranging scanners), the phase difference,and triangulation. Ranging scanners are able to survey objects andscenes with greater distances and so were adopted for the sedimentflushing project. The 3D Laser Scanner Riegl LMS-Z210 system wasused to realise in different epochs the side bank erosion process ofthe sand bar formed in the Unazuki reservoir (Sumi and Kanazawa,
2006). This scanner covers wide areas and collects four measurements
for each impulse: two angles, the distances and the intensity of thereceived echo impulse. The polar coordinates are immediately transformed in a local 3D Cartesian system (sensor system). Automatic
recognition of targets by intensity images matching is supported
Tracing of bed load transport
There are gaps to quantitatively assess the sediment deficit caused bylarge dams on a large river system, based upon regular, systematic andextensive direct measurements of total load (both in suspension andas bed load) upstream and downstream of the reservoirs. Recently,
the radio frequency identification (RFID) method was successfully
employed in various streams using mobile antennae to determine thedisplacement of single transponder-tagged particles.
The RFID system consists of a reader and control unit, antennae
and transponder (tags) used for tagging the object of interest. Several
types of passive and active tags have been developed. The active tags
have a battery inside, which increase the reading distance for 5m.

P rojects and case studies
Controlling reservoir sedimentation means in fact the control of
sediment deposition in reservoirs. Sediment flushing is a removal
strategy to pass the sediment through the reservoir and sediment
bypassing is a routing technique to pass sediment inflow around so
as not to accumulate in reservoirs. In Japan, it is common practiceto trap mainly coarse sediment by sediment trapping with checkdams which have been constructed just upstream of the reservoir
areas and remove accumulated coarse sediment by excavation. The
sediment replenishment method is one of the new measures of sediment management.
Sediment flushing is vital for the preservation of long-term storage
in reservoirs. However, downstream impacts can act as a constraint
in the planning and operation of sediment flushing. In order to understand the processes and the impacts of flushing, two examples are
given of the Unazuki and Dashidaira reservoirs, located at the Kurobe
River. For both reservoirs sediment inflow is extremely high compared with storage capacity. During minimum pool level the incoming
floods erode a flushing channel in the deltaic deposits. The channel
is gradually increased in width by bank-erosion processes during thisperiod. Quantitative and qualitative monitoring measurements during
flushing have been conducted for the sediment erosion process with
3D laser scanning, surface velocity (LSPIV), and suspended sedimentconcentrations (Kantoush et al, 2010a). The flushing channel within
Dashidaira reservoir has a stable profile and extends across the entire
impoundment width of 170m at distance of 640m from the dam(Sumi et al., 2009.
The Kurobe river originates in mountainous areas with peakelevation above 3000m. The main river flows for about 85km into
Toyama Bay. The average river bed slope which ranges from 1/5 to
1/80 is about 1/30. The mean annual precipitation ranges from 24004100mm. Sediment flushing has been conducted on the Dashidaira
Dam since 1991.
Since the completion of the Unazuki Dam in 2001, seven sedimentflushing and seven sediment sluicing operations have been conducted. When a flood in excess of 300m3/sec (250m3/sec in some special
cases) of inflow occurs at the Dashidaira Dam between June andAugust, a coordinated sediment flushing is performed. Whenevera flood in excess of 480m3/sec occurs at the Dashidaira Dam after

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ENVIRONMENT

sediment flushing, a secondary draw-down
flushing is performed. These sediment flushing and sluicing practises have been taking
place by agreement between the Kurobe River
Sediment Flushing Evaluation Committee
and the Kurobe River Sediment Management
Council, considering the natural flow regime
in the Kurobe River as well as the impacts of
sediment discharge downstream. The floods
occur primarily due to melting snow in May
and the rainy season from June to August. The
flushing period of June to August was chosen
by considering these natural flow regimes andthe impacts on fishing and agricultural water
use both in the downstream river and the connected sea shore area.
In recent years, water flow in excess of
300m3/sec (sometimes 250m3/sec) of inflow
at the Dashidaira Dam has been occurring
several times a year, and a flood in excess of
480m3/sec has occurred about once a year.
The threshold values are considered to beappropriate to perform sediment flushing
operations regularly.

M orphological process at
U nazuki reservoir
Several field measurements were conducted inorder to evaluate the morphological evolution
during drawdown flushing within Unazuki
reservoir. By using 3D laser scanning technology the morphological changes of sediment in
the reservoir were measured during and after
flushing in July at different times as shown in
Figure 5. The morphological topography withthe water surface is clearly visible in Figure 5.
Field measurements of time and spatial variations of the water surface during drawdown
flushing at night were also conducted. The
water surface elevation along the measuring
line is shown in Figure 5(right). This figure
shows how the shock waves generated by thescouring gate propagated over the sedimentbed. The observed flushing wave propagatesalong the measuring line at different time
steps.
Table 1 shows the actual amount of sediment flushed out of Dashidaira Dam since2001. The flushing volume data was obtainedby measuring the cumulative amount of sediment in the dam reservoir after the previous
year’s sediment flushing operation to the endof May. (Sumi et al, 2009).
The relationship between the quantity offlushed sediment and the quantity of waterused during sediment flushing operations canbe seen in figure 6(a). To measure the quantityof water used, we calculated the total discharge
in two periods: (1) from the start of drawing
down the reservoir water level to the completion of recovering the water level, and (2) fromthe start to the end of the free flow flushingphase.
As shown in Figure 6, the duration of sediment flushing (namely
the total discharge) is planned to be longer depending on the quantity of sediment to be flushed as seen by the 2005 flushing example.
Figure 6(b) shows sediment flushing efficiencies at the DashidairaDam, which are calculated by the quantity of flushed sediment andthe quantity of water used defined by the above two periods. The sed-42

Top: Figure 5; (left) 3D laser scanner measurements of deposition and water
surfaces within Unazuki reservoir and time series of measured water surface
elevations (right). Middle: Figure 6; (a) Relationship between the quantityof water used; (b) the quantity of flushed sediment and flushing efficiency.
Above: Figure 7; Stationary flow fields and corresponding velocity in the reservoir of Miwa dam for (a) Mode 1, (b, c) Mode 2. (Kantoush et al, 2011)
may 2011 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

Environment

iment flushing efficiency which is calculated by the quantity of waterused during the free flow phase was about 0.01 to 0.03. The sedimentflushing efficiencies became much higher in 2007 as a relatively lower
water level operation was maintained for a long time prior to thesediment flushing. This operation pushed the accumulated sediment
to the dam prior to the free flow operation, which made the flushing
more efficient than usual during the free flow operation.
To make the sediment flushing operation more sophisticated at the
Kurobe river, work is in progress to develop rainfall-runoff models
using radar data, to monitor sediment transport using 3D laser scanners and LSPIV technology, and to monitor highly turbid water andthe sediment transport rate.

M anagement techniques
In the following part of the article three different sediment management techniques were evaluated at different projects. The hydraulicbehaviour of flow and sediment in tunnels still needs to be clarified inorder to design safe and economical sediment bypass tunnels, as wellas establish countermeasures for abrasion damage on channel bed
surfaces. The number of bypass tunnel is expected to increase in the
future and some are under construction (Koshibu and Matsukawa
dams), or in the planning stages (Yahagi, and Sakuma dams).
Several parameters have been monitored namely, upstream precipitation, turbidity, water quality, fish, benthic animals, and attachedalgae. This data can be used for switching operation modes. The
first normal mode is that all incoming flood flow will overflow thediversion weir into the main reservoir (Mode 1). While the second
mode is some part of the incoming flood flow will be diverted to thebypass tunnel after opening the main bypass gate (Mode 2). The lastmode is the refilling mode by closing the main bypass gate (Mode3). Generally we can use inflow discharge to design and guide thetiming for switching these operation modes. In order to increase theperformance of sediment bypassing and removal efficiency, we need
to focus on surface flow patterns and suspended sediment concentration in the approach flow area to the bypass tunnel according todifferent modes.

M iwa dam bypass system
The sediment bypass tunnel at Miwa Dam was Japan’s first experience of a sediment management technique which diverts mainly suspended sediment concentration at a multipurpose dam. Miwa dam
is located on the Mibu river, a tributary of the Tenryu. It is a 69mhigh gravity concrete dam with a 29.95Mm3 gross storage reservoir
and a 311km2 catchment area. Since the dam was completed, several
extreme runoff events caused serious disasters and sediment yield.
About 20Mm3 of sediments were deposited by 2002 since the completion of the dam and a sediment bypass system was completed in
March 2004.
Based on theoretical considerations and recorded field data, theannual sediment inflow at Miwa dam was evaluated at an averageamount of 0.68Mm3, of which 0.525 Mm3 was wash load and 0.16
Mm3 was bed load combined with suspended load. The complex sediment countermeasure system consists of the following installations:• Check dam; the sediment is periodically excavated and transported
by private gravel agencies.
• Diversion weir of 0.51 Mm3 combines the functions of training andtrapping the sediment. The wash load that flows down through thecheck dam is directed together with the flood water from a bypass
channel into a bypass tunnel. Here two cameras (3 and 4) areinstalled to monitor the flow velocity in the bypass channel. Duringhigh flood the facility allows the training dikes and trap weir totrap the coarse grain sizes that overflow from the check dam inorder not to flow into the tunnel. The approach flow infront of
the main gate is monitored by camera 1 and 2 for flow field analysis
before and after the gate opening for switching modes. Moreover,for SS monitoring two points with two different instruments are
installed.
• Flood bypass tunnel of 4.3km long, 7.5m diameter, 1% slope, and
WWW.WATERPOWERMAGAZINE.COM may 2011

Sediment flushed out of
Dashidaira Dam since 2001
Maximum
discharge
Inflow(m3/sec)

Average
Discharge
Inflow(m3/sec)

Flushing
Volume(103m3)

Maximum
SS (mg/l)

Average SS(mg/l)

2001
Flushing

333

277

590

90,00015,0002001
Sluicing

491

273

-

29,0006700

2002
Flushing

362

215

60

22,0004500

2003
Flushing

777

217

90

69,0007100

2004
Flushing

356

229

280

42,00010,0002004
Sluicing

1152

281

-

16,0007300

2005
Flushing

958

290

510

47,00017,0002005
Sluicing 1

835

275

-

90,00016,0002005
Sluicing 2

790

250

-

40,0007300

2006
Flushing

308

246

240

27,0005200

2006
Sluicing 1

378

203

-

12,0002500

2006
Sluicing 2

685

264

-

27,0005200

2006
Sluicing 3

529

196

-

7400

1800

2007
Flushing

418

245

120

25,0003500

Average ofFlushing

502

246

270

46,0009100

Average ofSluicing

694

249

-

31,6006700

Average ofall data

598

247

270

38,8007900

300m3/sec capacity.
• Auxiliary reservoir sediment discharge facility is under planning todischarge wash load that flows into the reservoir together with floodwater, into the downstream reaches as a flood control measure.
The main purpose of this project was to evaluate the effectiveness ofthe sediment bypassing system and develop digital image techniques
to measure SS and flow field. These will assist in operating sediment bypass tunnels efficiently for managing diverted floods withwash load from the reservoir. The observed efficiencies of bypassed
sediment reported hereafter will provide a basis for determining thebest management practice for existing and future planned bypass
tunnels.
LSPIV and Fx-8100 techniques were applied for two different
study areas in front of bypass tunnel approach flow in the reservoirof Miwa Dam. Recorded images at two modes were treated to evaluate the approach flow in three zones, considering the possibility ofthe vortex formations that can influence the bypass efficiency. Flow
field measured by LSPIV are shown in Figure 7. The main flow was
directed towards the diversion weir at Mode 1 and a circulation in
front of the bypass tunnel was formed.
The velocity magnitudes inside the reservoir have low values of
30cm/sec (Figure 7(a) right). Two zones in front of the bypass were
measured, before and after the log boom. The flow field of zone 1(see Figure 7(a) on the left), reveals the effect of the bypass opera-

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ENVIRONMENT

Figure 8: Sediment replenishment site in Uda River downstream of Murou Damtion in Mode 2. The separation of the flow in the reservoir leads toa small retention in the immediate upstream part of the reservoir
and therefore to high turbidity. This process is localised in the left
side of the reservoir. This result in flow separation on the right andleft to the weir and bypass can be illustrated clearly in Figure 7(c).
Interesting effects of the flow separations in front of the bypass, suchas a concentration of inflow to the bypass and an increase in velocities, can be detected by the measurements Figure 7(c) on the right. The
LSPIV measurements in zone 2 (see Figure 7(c) on the right) reveal theimpact of the contraction due to the trap weirs.
Inflow suspended sediment concentration were recorded by four
different monitoring techniques (Image processing, SMDP, turbiditymeter, and Sampling). The peak concentration is almost equal to inflow
discharge peak and turbid flow from 2500 to 1000mg/l was bypassed.
Turbidity trend was well monitored by several measurement data andvery much helpful to switching from Mode 1, Mode 2 and Mode 3.
Sediment bypass system in Miwa dam is effectively routing incoming fine sediment directly to the reservoir downstream. The measured
efficiency of sediment bypassed by optical turbidity meter was up to
80% of the total inflow sediment. This efficiency was also measured atselected events by image processing which is a very useful tool in characterizing the performance of bypass tunnel operation. Moreover, themeasured surface flow velocities and suspended sediment concentrations in the context of sediment management in reservoirs are important for the validity of the numerical analysis of Miwa Dam.

S ediment replenishment technique
In Japan, it is common practice to remove accumulated coarse sediment by excavation and dredging and to make effective use of theremoved sediment. The sediment replenishment method is one of
the new measures of sediment management. Here trapped sediment(mainly at sediment trapping check dams) is periodically excavated andthen transported to be placed temporarily downstream of the dam ina manner decided according to the sediment transport capacity of thechannel and the environmental conditions. Therefore, the sediment isreturned to the channel downstream in the natural flooding processes.
The procedure consists of four steps: Extracting mechanically theaccumulated sediment at the check dam; Transporting it by truck to
the downstream river; Placing the sediment with specific geometry;
Monitoring flow, sediment, and environmental parameters.
The replenished sediment is placed at such an elevation in order toreduce the turbidity during normal flow periods. The top of the sediment is adjusted so that the sediment is completely submerged during
flood at several times a year and all sediment is eventually transported
downstream. Several considerations have to be given to environmental problems in the lower river basins, occurrence of turbid water,and safety risks due to sediment deposition in the channel. Concretemeans are being explored taking into consideration sediment particle
sizes and the scale of flood that is suitable for safe implementation.

44

In Japan, sediment replenishment projects are being undertaken withdifferent configurations and characteristics of sediment and discharges.
Some of these projects are successful when placed sediments are washedduring high flows. But in the other part of these projects, sediment
replenishment is not mobilised or transported according to the postproject monitoring. The central challenge in sediment replenishment
research is to determine sediment and flow characteristics, which operation to implement, and how to determine sediment replenishment factors. Indeed, river morphodynamics is a complex process that involves
a high degree of interaction between the flow and sediment transport.
And several significant gaps in the scientific understanding of these processes remain, particularly concerning how riverbed deposition, mobility
and geometry are influenced by changes in the flow discharge from the
upstream dam and replenishing sediment volumes. Replenishment scenarios may, therefore, induce undesirable morphological and ecologicalconsequences as well as significant channel adjustments that can resultin failure of the restoration project itself. It is necessary to better understand reversibility, direction and time scale of changes, and the sustainability of a replenishment intervention before it is implemented.

M urou D am sediment replenishment
The test site for this study is placed by the Japan Water Agency (JWA)on the right side bank of Uda River downstream of Murou dam in
Nara prefecture. Planning, design, implementation and long-termmonitoring of Murou dam replenishment tests have been guided by
JWA. Photographs in Figure 8 show the 2010 field test of Murou
dam stilling basin and the placed sand in the downstream reach 150m
from the dam site. The cross-section of the placed sediment geometry
which has a trapezoidal shape with a groove channel near the river
right bank is shown in Figure 8.
Various sediment volumes since 2006 have been supplied to Uda
river downstream of Murou Dam (Kantoush et al, 2010b). The
volume of placed sediment is limited to several hundred cubic meters
each time. Two types of flow are used to transport the placed sediment; natural flood and artificial flushing flows discharge from thedam. To implement this method, consideration has to be given toenvironmental problems in the lower river basins, to the occurrenceof turbid water, and to safety risks due to sediment deposition in thechannel. Concrete means are being explored, taking into consideration the particle sizes of sediment, such as the scale of flood suitable
for the safe implementation.
The evolving bed topography and grain size distribution are monitored, along with water surface, velocities and rate of sediment transport at the downstream end of the river. Measurements are performed
at various cross sections along the river. With the field experiments theprocesses are directly visible and a wealth of valuable data is obtainedwith relative ease, and will be used for further calculation or validation
Figure 9: Looking downstream photographs of morphological evolution during
artificial flushing of placed sediment at Uda River bank.

may 2011 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

Environment

100%
Percentage ofbed grain size

Figure 10: Variations of river bed material size in 13 cross sections along Uda River>20cm

5~20cm<5cm

80%

Percentage ofbed grain size

Percentage ofbed grain size

Murou Dam60%
of numerical models. To understand the process of scourPlaced
No.1 (0.1km)
Sediment
ing and deposition during the artificial flushing of the40%
No.2 (0.2km)
placed sediment series of pictures are taken at different
No.2-1 (0.2km)
20%
No.3 (0.3km)
time and discharge as shown in Figure 9.
No.4 (0.5km)
0%The figure clearly depicts the process of erosion andNo.5 (0.8km)(a) 1 2 2-1 3
4 5 6 7 7-1 8 9 9-1 10
flow behaviors. The erosion at the base of the placed
No.6 (0.9km)>20cm
5~20cm<5cm
sediment causes the sand mass of placed sediment bank No.8 (1.3km)
100%
No.7 (1.0km)
to slide downward and deposit. Deposited sand mass is80%No.7-1 (1.1km)
then flushed due to water flow. The width of erosion
60%
during the whole flushing periods is one to three times
the height of the placed sediment. The erosion region
40%
developed from a straight bank line into the crenulated20%
shaped (half moon shape) as seen in Figure 9 b). At theNo.9 (2.6km)
0%peak discharge the water level increased at t3 produce(b) 1 2 2-1 3
4 5 6 7 7-1 8 9 9-1 10
a greater erosion area and the water enters the grove>20cm
5~20cm<5cm
channel in the placed sediment as shown in Figure 9(c).
100%No.9-1 (3.2km)
Artificial flushing increases the erosion rate and trans80%
ports the sediment out of the placed sediment region.
60%
The peak discharge lasts for two hours and permits
40%
No.10 (4.0km)
a deeper cut in the placed sediment bank. With peak
20%
flow, the eroded volumes increase in the range of 4%.
Reduction of discharge at t5 reduces the erosion rate,0%(c) 1 2 2-1 3
4 5 6 7 7-1 8 9 9-1 10
therefore 50m3 of the placed sediment remains asshown in Figure 9(f). By looking downstream in Figure
9, the erosion start at the inner bank of the placed sediment till the half moon shape is formed due to gradually increase of
the discharge at t1 and t2, see Figure 9(a, b).
Figure 10 shows bed material size in three different monitoring
Sameh A. Kantoush, Tetsuya Sumi, and Yasuhiro
times and 13 observation points along the river. Before sediment
Takemon, Disaster Prevention Research Institute, Kyoto
replenishment in point No 2 and No 2-1, the material is coarser
University, Goka-sho, Uji-shi, 611-0011, Japan,
gravel than in the farther downstream points No 4 and No 7 (Figure10(a)). After flushing, the fine material content of the channel deposits
References
increased. The sediment deposition in point No 2 and No 2-1 after
replenishment consist of a nearly continuous layer of fine sand, but no[1] Sumi, T., 2003: Reservoir sedimentation management in Japan, The 3rdchange occurs further downstream (Figure 10(b)). But after natural
World Water Forum, The 3rd World Water Forum, Kyoto-Chiga-Osaka., Japan.
floods there less sediment volume is placed and the bed material is[2] Japan Dam Association, 2003, Dam Yearbook (in Japanese)transported. Much of the coarsest sediment is supplied to point No[3] Kantoush, S. A., and Sumi, T., 2010: River morphology and sediment2, and No 4 (Figure 10 (c)). The amount of supplied sediments is not
management strategies for sustainable reservoir in Japan and European Alps,
effectively influenced on the river bed after natural flood occurs.
Ann. Disas. Prev. Res. Inst., Kyoto Univ., 53(B), pp. 821-839.
By replenishing sand at different locations of the Uda River within[4] Palmieri, A. (2003): Social and economic aspects of reservoir
the downstream reaches, the replenishment may direct future supconservation, The 3rd World Water Forum, Kyoto-Chiga-Osaka., Japan.
plements for a more widespread dispersal of suitable sand for fish
[5] Sumi, T. (2000): Flushing efficiency on sediment flushing operation
spawning. In order to put the downstream sediment replenishment
in Reservoir, Journal of Japan Society of Dam Engineers, 10(3), 211-221
method to practical use, it is also important to share information with
(Japanese).
the people concerned in the same river basin, such as fishery workers[6] Sumi, T. and Kanazawa. H., 2006: Environmental study on sedimentassociations and environmental groups, and endeavor to make theflushing in the Kurobe River, 22nd international congress on large dams,
method socially acceptable. Sediment replenishment for the purpose
Barcelona, Q.85-R.16, 219-242.
of keeping a dam functional needs to be performed semi-permanently.
There is a need to increase the amount of the supplied sediment and[7] Kantoush, S. A., and Sumi, T., 2011: Sediment replenishing measures forrevitalization of Japanese rivers below dams, 34th IAHR Biennial Congress,
artificial flow discharge every year. The increasing amount of flushing
Brisbane, Australia.
flow discharges should erode the placed sediment and move typicalsize gravel of 10cm.
[8] Sumi, T., Kobayshi, K., Yamaguchi, K., and Takata, Y., 2009: Study on the

I ntegrated management
In case of sediment management, it is necessary to find out the appropriate combination of flow and sediment release to meet the demandsof various functions based on hydrology, water quality, river morphology and the ecosystem. Furthermore, an integrated sediment management approach should be considered in a sediment routing system
which covers not only the river basin but also connecting coastal area.
Selected sediment management measures should be evaluated by abenefit/cost analysis. Sediment management of reservoirs is a complicated process which will affect reservoir sustainability and downstream river health. So we should start to implement it on a step bystep basis by conducting field monitoring under an adaptive management concept. IWP & DC
WWW.WATERPOWERMAGAZINE.COM may 2011

applicability of the asset management for reservoir sediment management.
23rd Congress of ICOLD, Brasilia, Brazil, Q.89-R.4.
[9] Kantoush, S. A., Sumi, T., Suzuki, T., Murasaki, M., 2010: Impacts of
sediment flushing on channel evolution and morphological processes:
Case study of the Kurobe River, Japan”, International Conference on Fluvial
Hydraulics, River Flow 2010 Braunschweig, Germany, ISBN 978-3-93923000-7, pp. 1165-1173.
[10] Kantoush, S. A., Sumi, and T., Kubota, A., 2010: Geomorphic responseof rivers below dams by sediment replenishment technique”, International
Conference on Fluvial Hydraulics, River Flow 2010 Braunschweig, Germany,ISBN 978-3-939230-00-7, pp. 1155-1163.
[11] Kantoush, S. A., Sumi, T., and Murasaki, M., 2011: Evaluation of sediment
bypass efficiency by flow field and sediment concentration monitoring
techniques, J. of Hydraulic Engineering, JSCE, Vol.55, pp. 169-173.

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