SEDIMENT TRANSPORT PROCESSES IN
MOUNTAIN AREA OF KINUGAWA RIVER
Catherine G. Jaceldone 1
MEE15625

Supervisors: Atsuhiro Yorozuya 2
Shinji Egashira 3

ABSTRACTThis study aims to develop a sediment transport model incorporated in Rainfall Run-offInundation (RRI) Model. The sediment transport process model is able to analyze thesediment transport processes in Kawamata River Basin located in the upstream of Kinugawa
River. Sediment transport rates, riverbed deformation and sediment size distributions areevaluated at four areas. The model is calibrated in RRI Model at Typhoon No.7 of September
2007. Then, the model was processed again with the prepared sediment parameters and inputs.
Results obtained from the present model show that sediment armoring of riverbed and highconcentration of suspended and wash load are predicted in upstream area. Fine sediment istransported and trapped behind Kawamata Dam. Bed load transport rate is high at peakdischarges. Sedimentation processes in a channel are attributed to flood discharge, particle
size of bed sediment, river shape and river slope.
Keywords: Sediment transport, sediment budget, river bed evolution, flow discharge,
Kawamata River Basin
INTRODUCTION AND BACKGROUND
Kawamata River Basin is part of Kinu River Basin that flows to Tonegawa River which isthe largest river in Japan. Water source from Kinunuma swamp and terminates in Kawamata
Dam. The catchment area is approximately 179.40 sq.km. with water surface area of 259
hectares. The basin is characterized by high and steep topography . Valley widths are narrow
and rivers are short giving a large ratio of peak flow discharge to basin area. Thus, massive
sediment movement takes place often during heavy rains. As a result, there is a greater riskof sediment induced disasters. Sediment disasters causes damage to lives, properties andenvironment. In this regard, it is a necessity to give attention on the sediment transport
processes on any river system.
The main objective of this study is to develop a model to analyze the sediment transport
processes in Kawamata River basin. Usually, inundation analysis on rivers neglects the effectof sediment. Due to the fact that all rivers have sediments, it is necessary and helpful for
designers to include the effects of sediment movements on river analysis. To develop suchmethod, a 1-D sediment transport model is combined with the Rainfall Run -off Inundation
model. The proposed method will be able to predict flood hydrograph at any point of channel
network, sediment discharges such as bed load, suspended load and wash load, evaluate river
bed deformation and sediment size distribution at any point of channel network if the rainfall
condition is specified in the drainage basin
1Engineer II, PDD, Department of Public Works and Highways Region III, Philippines
Associate Professor, Public Works Research Institute, Japan
3Professor, International Centre for Water Hazard and Risk Management, Japan
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METHODOLOGY AND THEORYTo predict sediment transport
processes on a given drainage basinin the course of rainfall run-off,sediment models are incorporated inRRI Model. Figure 1 shows
sequential activities of the study.
Rainfall Run-off Inundation (RRI)
Model is a two-dimensional model
capable of simulating rainfall run-off
and flood inundation simultaneously(Sayama et al. 2012). The flow on theslope grid cells is calculated with the2D diffusive wave model by the massbalance equation while the channel
flow is calculated with the 1D
diffusive wave model by themomentum equations described as
Figure 1 Sequential steps of the study
follows:
𝑖−1,𝑗𝑖,𝑗𝑖,𝑗−1𝑖,𝑗𝑞𝑦− 𝑞𝑦𝑑ℎ𝑖,𝑗 𝑞𝑥− 𝑞𝑥++= 𝑟 𝑖,𝑗 − 𝑓 𝑖,𝑗𝑑𝑡∆𝑥∆𝑦−𝑘𝑎 ℎ𝑞𝑥 =𝑞𝑦 =𝑖,𝑗

𝜕𝐻,
𝜕𝑥(1)

(ℎ ≤ 𝑑𝑎 )

1
𝜕𝐻
𝜕𝐻
𝜕𝐻
− (ℎ − 𝑑𝑎 )5⁄3 √| | 𝑔𝑛 ( ) − 𝑘𝑎 ℎ,𝜕𝑥𝜕𝑥
𝜕𝑥{ 𝑛𝜕𝐻(ℎ ≤ 𝑑𝑎 )−𝑘𝑎 ℎ,
𝜕𝑦1
𝜕𝐻𝜕𝐻
𝜕𝐻− (ℎ − 𝑑𝑎 )5⁄3 √| | 𝑠𝑔𝑛 ( ) − 𝑘𝑎 ℎ,𝜕𝑦𝜕𝑦𝜕𝑦{ 𝑛(2)(𝑑𝑎 < ℎ)(3)(𝑑𝑎 < ℎ)𝑖,𝑗where 𝑞𝑥 , 𝑞𝑦 : discharges from a grid cell at (i,j) in x and y directions, 𝑘𝑎 : lateral saturated
hydraulic conductivity and 𝑑𝑎 : soil depth times the effective porosity.
In general, riverbed is composed of non-uniform sediment. Change in bed elevation isdetermined by analyzing the sediment inflow and outflow at any point. Temporal change inriver bed elevation is described by:
𝜕𝑧𝑏1
𝜕𝑞𝑏𝑖+
∑(+ 𝐷𝑠 − 𝐸𝑠 + 𝐷𝑤 − 𝐸𝑤 ) = 0(4)𝜕𝑡 (1 − 𝜆)𝜕𝑥𝑖Ashida and Michiue’s bed load formula is employed, which is given by 𝑞𝑏 .
3𝜏∗𝑐𝑢∗𝑐𝑖𝑞𝑏𝑖 = 17𝑝𝑖 𝜏∗𝑒 2 (1 − ) (1 −)(5)
𝑞𝑏 = ∑ q𝑏𝑖
𝜏∗𝑢∗

(6)

Mass conservation equation of suspended sediment within the flow body is described by:∂𝑐𝑠𝑖 ℎ ∂r𝑖 𝑢𝑐𝑠𝑖 ℎ∂∂𝑐𝑠𝑖∑(+) = ∑ (ℎ𝜀𝑥) + 𝐸𝑠 − 𝐷𝑠(7)
𝜕𝑡𝜕𝑥
𝜕𝑥
𝜕𝑥𝑖𝑖

where 𝐸𝑠 is the erosion rate and 𝐷𝑠 is the deposition rate of suspended sediment.

2

The erosion rate for suspended sediment is calculated from equation 8 where 𝑤𝑜𝑖 is thesettling velocity and 𝐶𝑎𝑒𝑖 is calculated by Lane and Kalinske as:1 𝑢∗
𝑤𝑜𝑖 1.61
E𝑠 = ∑ E𝑠𝑖 = ∑ 𝑤𝑜𝑖 𝐶𝑎𝑒𝑖
(8)(9)
𝐶𝑎𝑒𝑖 = 5.55 {𝑒𝑥𝑝 (−)}
𝑟𝑏
2 𝑤𝑜𝑖𝑢∗𝑖𝑖
Deposition rate for suspended sediment is calculated by:
𝐶𝑠𝑖 𝛽𝑠𝑖D𝑠 = ∑ D𝑠𝑖 = ∑ 𝑤𝑜𝑖 𝐶𝑠𝑏𝑖
𝐶𝑠𝑏𝑖 =(10)(11)
1 − 𝑒𝑥𝑝(−𝛽𝑠𝑖 )𝑖𝑖
where 𝐶𝑠𝑏𝑖 is the concentration at reference level of size class iMass conservation equation of wash load and associated erosion – deposition rates aredescribed as:∂𝑐𝑤𝑖 ℎ ∂r𝑖 𝑢𝑐𝑤𝑖 ℎ∂∂𝑐𝑤𝑖∑(+) = ∑ { (ℎ𝜀𝑥)} + 𝐸𝑤 − 𝐷𝑤
𝜕𝑡
𝜕𝑥
𝜕𝑥
𝜕𝑥
𝑖

(12)

𝑖

Erosion and deposition rate of wash load can be calculated by equation 12 and 13 respectively.
∂𝑧𝑏D𝑤 = ∑ D𝑤𝑖 = ∑ 𝑤𝑜𝑖 𝐶𝑤𝑖
(13)
(14)
E𝑤 = −(1 − 𝜆)𝑓𝑖
𝜕𝑡𝑖𝑖
Sediment transport rate and associated channel change are influenced by sediment size ofbed surface. The fraction of size class 𝑑𝑖 is described in terms of mass conservation equationof size class 𝑑𝑖 for bed surface layer. This is given by:
∂𝑝𝑖1
∂𝑞𝑏𝑖
∂𝑧𝑏 𝑓𝑖(15)=(+ 𝐸𝑠𝑖 − 𝐷𝑠𝑖 + 𝐸𝑤𝑖 − 𝐷𝑤𝑖 ) −𝜕𝑡
1 − 𝜆 𝜕𝑥𝜕𝑡 𝛿DATAThe targeted rain is the 07 September 2007 flood event, hourly rainfall datas are downloadedin MLIT website in four gauging station located within the drainage basin, then, datas areconverted to data file. Discharge datas in Kawamata Station are downloaded to compare withthe simulated results of RRI model.
Download 3 arc second (90m) SRTM DEMs from the website of CGIAR-CSI for Japan.
Topographic file for Kawamata drainage basin such as Digital Elevation Model (Figure 1DEM), Flow Direction (Figure 2 DIR) and Flow Accumulation (Figure 3 ACC) wereprepared using ArcGIS, then converted to ASCII file.

Figure 1 DEM

Figure 2 DIR

Figure 3 ACC

For the preparation of sediment inputs for RRI, maximum size of sediments are calculated atdifferent points along the reach.Analysis of sediment size distribution was divided into threezones as shown in Figure 4. Using the log plot in Figure 4, distribution of particle sizes wascalculated and represented according to JIS A 1204 and used as sediment input. Sedimentmodels were introduced into the RRI source codes for the evaluation of sediment t ransport
processes in a channel and referred as sed_input.txt.

3Percentage finer than (%)

10080

y = 8.4228ln(x) + 31.817

60
4020Zone 200.01 0.1
110100 1000
Diameter of sediments (mm)Fig. 5 Log Plot of D criticalFig. 4 Particle Distribution

0102030405060708090100

Basin Avg Rain_calc
Obs Discharge

9/21

9/17

9/13

9/9

9/5

9/1

8/28

8/24

RRI Simulation

Basin Ave. Rain (mm/hr)

1000900
800
700600500
400300200
10008/20

Discharge (m3/s)

RESULTS AND DISCUSSION
In this study, RRI model was run several times to determine the parameters that gives thebest possible results. The model was calibrated for the flooding event of September 2007
(Figure 4) and showed a Nash Sutcliffe Efficiency (NSE) of 0.856.

Fig. 6 RRI Model Calibration (Sept. 2007)

0250500

750

Time Steps (hr)

800
700
600
500
400
300
200100024211815129630flow discharge (qr)flow depth_river (hr)

0250

500

750

Water Depth on River (m)24211815129630

flow discharge (qr)flow depth_river (hr)Water Discharge (m3/s)

800
700
600
500
400300200
1000

Water Depth on River (m)Water Discharge (m3/s)

Using the calibrated parameters, RRI with sediment models was run again. The results for
sediment transport processes are evaluated at three zones along the river reach and anotherone at Kawamata station. For this discussion, results are describe at Zone 1 (u pstream) andKawamata Station (downstream).

Time Steps (hr)Fig. 7&8 Temporal Changes of qr and hr in Upstream & Downstream
Figure 7 and 8 shows the relationship between flow discharges and flow depths in upstream
and downstream area. It can be observed that at period of peak discharge, flow depth start toincrease and goes down as discharge decreases. In upstream area, flow depth becomes zeroat end of flooding event while in downstream area, it can be noticed that flow depth remainsconstant after the flooding event due. This is due to the lowered riverbed elevation ofKawamata Lake.

4250
500
Time Steps (hr)

750

800
700
600
500
400
300
2001000

1950
1945
1940
1935
1930
1925
1920
1915
1910

flow discharge (qr)river bed elev (zb)

0

250
500
Time Steps (hr)750River Bed Elevation (m)0Water Discharge (m3/s)

1132
1130
1128
1126
1124
1122
1120
1118
1116

flow discharge (qr)river bed elev (zb)River Bed Elevation (m)Water Discharge (m3/s)

800
700
600
500
400
300
200
1000Fig. 9&10 Temporal Changes of qr and zb in Upstream & Downstream

0250500
Time Steps (hr)

1.E+10
1.E+081.E+06
1.E+04
1.E+02
1.E+00
1.E-02
1.E-04
1.E-06

750

800
700
600
500
400
300
200
1000

1.E+10
1.E+081.E+06
1.E+04
1.E+02
1.E+00
1.E-02
1.E-04
1.E-06flow discharge (qr)suspended load rate (qss)
bed load rate (qsb)wash load rate (qsw)

0250
500
Time Steps (hr)750

Sediment Discharge (m3/s)

flow discharge (qr)suspended load rate (qss)
bed load rate (qsb)wash load rate (qsw)

Water Discharge (m3/s)

8007006005004003002001000Sediment Discharge (m3/s)

Water Discharge (m3/s)

Figure 9 & 10 shows the relationship between the flow discharges and riverbed elevations in
upstream and downstream area. In upstream area, at onset of peak discharge, there is lower
sediment inflow than outflow rates. It was determined that at high flow discharges,
degradation occurs because of low sediment inflow rate. In downstream area, sediments aretrapped behind the dam, aggradation is evident. This is the point when critical bed shear
stress is very low, hence, sediments settles down.

Fig. 11&12 Temporal Changes of qr and qsb/qss/qsw in Upstream & Downstream

Percentage Finer (%)

Figure 11 & 12 shows the relationship between the flow discharges and sediment discharges
in upstream and downstream area. In upstream area, large sediments start to move at time ofpeak discharge and settle again at time of low flow. It implies that large particles are notbeing moved by the flow and main means of transportation was through suspension. Indownstream area, Bed load transport rate is high at point of peak discharges. Suspended loadand wash load dominates in this zone and prominent throughout the flooding event.
10090807060
504030201000.00001

Initial Condition
Zone 1
Zone 2
Zone 3
Kawamata Dam

0.0001

0.001
0.01
0.1
Sediment Diameter (m)Fig. 13 Temporal Changes ofParticle Size Distribution in Zone 1,Zone 2, Zone 3 & Kawamata Dam1

Figure 13 shows the temporal changes of particle size distribution in four locations. Basedfrom the results of simulation, upstream part has coarser materials because bed she ar stressis high at this area. After flooding events, larger particles remain and finer particles are beingtransported in downstream area. It can be noted that suspended load and wash load dominatesin the lake.

5CONCLUSIONS
A method to evaluate sediment transport processes in drainage basins is proposed. This model
is developed by combining sediment transport models with rainfall run -off model and isapplied to predict the sediment processes in Kawamata Dam drainage basin. The model isable to provide interesting results on sediment transport rates and river bed evolution.
However, there are several unsolved problems as follows :i.
The topographic map or DEM employed in study must give information nearly to theactual river channel because it has huge effect to the initial river bed slope.
ii.
Long term simulation (example, 10 years or more) is recommended, to settle down
the initial sediment discharges that would give a better result of sediment transport
processes.
iii.
A model that include the estimation of sediment production in the slope will improvethe understanding on sediment movement.
This developments are recommended to help designers to create a better sedimentmanagement strategies that will extend reservoir life and benefit downstream areas.
ACKNOWLEDGEMENTSFirst, I would like to give my deepest gratitude to our Almigh ty God, for His endless blessingsand guidance. I would like to express my gratefulness to my supervisors, Associate Professor
Atsuhiro Yorozuya and Professor Shinji Egashira, for their untiring e ffort to share theirknowledge. I would also like to give thanks to the researchers of ICHARM and appreciation
to the administrative staffs for their patience and friendship. Also, a big thanks to Japan
International Cooperation Agency (JICA) and National Graduate Institute for Policy Studies(GRIPS) for giving me the opportunity to attend this Disaster Management Policy Program(2015-2016). My special thanks to the Philippine government and my Department of Public
Works and Highways Region III family. Lastly, I would like to express my thanks to myhusband for his undying love and support. Also, to my kids, mother and siblings for theirmoral support.
REFERENCES
1. CGIAR-CSI. (2016). The CGIAR Consortium for Spatial Information.
2. Chilli, O. G. (2015). Prediction of Sediment Transport Processes in Nzoia River Using
Rainfall-Runoff Model (RRI ver.1.4.2). Master Thesis, ICHARM, PWRI.
3. Egashira, S. (2015). Mechanics of Sediment Transportation and River Changes. Lecture
Notes, ICHARM, PWRI.
4. Japan Society of Civil Engineers. (1999). Handbook of Hydraulic Formulas.
5. Kinugawa Integrated Dam Control Office, MLIT. (2012, November 8). Kinu and Kokai
River (Group of Dams).
6. Kinugawa Integrated Dam Control Office, MLIT. (n.d.). Kinu and Kokai River.
7. McCully, P. (1996). Sedimentation Problems with Dams. Silenced Rivers: The Ecologyand Politics of Large Dams.
8. Nikko Sabo Office, KRDB, MLIT. (2016). Protecting Comfortable and Healthy Lives.
NIKKO SABO, 5-7, 22-23.
9. Sayama, T. (November 2015). Rainfall-Run-off-Inundation (RRI) Model ver. 1.4.2.
Manual, ICHARM, PWRI.
10. Water and Disaster Management Bureau,MLIT. (n.d.). River basic information.

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