Annual Journal of Hydraulic Engineering, JSCE, Vol.52, 2008, February
Annual Journal of Hydraulic Engineering, JSCE, Vol.52, 2008, February

SEDIMENT YIELD AND TRANSPORTATIONANALYSIS: CASE STUDY ON MANAGAWA
RIVER BASIN
Chadin CHUTACHINDAKATE1 and Tetsuya SUMI2
1Member of JSCE, Doctoral Student, Dept. of Civil and Earth Resources Engineering, Kyoto University (Katsura
Campus, Nishikyo-ku, Kyoto 615-8540, Japan)
2Member of JSCE, D. Eng. , Associate Professor, Dept. of Civil and Earth Resources Engineering, Kyoto University(Katsura Campus, Nishikyo-ku, Kyoto 615-8540, Japan)

Sediment system in watershed is not only sediment yield but also including sediment transportation
along the rivers. In this study, the Geographic Information System (GIS) combined with sediment yieldmodel can be enhancing the evaluation of soil erosion estimation. Surface erosion on Managawa river
basin is computed with the Modified Universal Soil Loss Equation (MUSLE) and it is verified to reflect
the hydrological processes be able to estimate soil losses. In the sediment transport routing module, totalload equation is applied to carry sediment from soil surface erosion to deposit in Managawa dam.
According to annual accumulation sediment volume data in Managawa reservoir during 1981 – 2003, theestablish model and simulation results are satisfy. The efficiency of the Modified Universal Equation withsediment routing in rivers is more than the simple Modified Universal Equation.

Key Words : Sediment Yield, Sediment Transportation, Soil Erosion, MUSLE, Managawa Dam

1. INTRODUCTIONManagawa Dam is located on the high rainfall
density and steep slope area caused sedimentproblems. Every year the bottom levels of reservoir
are observed then we can know annual sedimentdepositing volume. There exist many kinds of soil
erosion models, both physical models and empiricalmodels and also there are many useful numericalformulas to predict annual sediment yield. The mostpopular soil erosion equation is Universal Soil Loss
Equation (USLE). Simple empirical methods suchas Universal Soil Loss Equation (USLE) (Musgrave,
1947; Wishchmeier and Smith, 1965), Revised
Universal Soil Loss Equation (RUSLE) (Renard etal., 1991) or Modified Universal Soil Loss Equation(MUSLE) (Williams, 1975) are frequently used for
estimation of surface erosion and sediment yieldfrom catchment areas. In Modified Universal Soil
Loss Equation (MUSLE), the rainfall energy factor
is replaced with a runoff factor and optimizeshydrologic process of sediment yield thus these
improve the sediment yield prediction. The main

objective of this study is computing annual
depositing sediment volume in Managawa dam byusing soil erosion model and sedimenttransportation model. Erosion on sub-basin causedby rainfall and surface runoff is computed with
Modified Universal Soil Loss Equation (MUSLE),
which time interval is day continuously from 1983
to 2004. After outlets of each sub-basin, sedimentwill be transported by main channel. This study
shows the results of these combined systems.

2. STUDY AREAManagawa Dam constructed during 1965-1977
in Fukui prefecture is located at latitude 35º 55' 50"
N and longitude 136º 32' 31" E. Managawa Dam isa concrete arch dam with 127.5 m height, 357 m
width and 115 MCM capacity designed for
irrigation, water supply and power generation where
Managawa river is a tributary of Kuzurui river.
Catchment area above the dam is about 223.7 km2
that the mean elevation is 830 m above mean sea
level and land slope is about 0.45. Since there are- 157 -

Fig.1 Managawa river basin

Kumokawa Dam and Sasougawa Dam situated on
up stream of Managawa Dam as shown in Fig.1,
sediment will be captured by those dams but
Kumokawa Dam has been filled full by sediment.
Therefore sediment supply to Managawa Dam isalso generated from watershed above Kumokawa
Dam. During the study period, 1981-2004, theaverage annual rainfall is 2391 mm. The area iscovered by forest where accounts for 94% area of
total watershed. The major soil types in the study
area are sandstone, mudstone and conglomerate(Managawa Dam office, 2005)
3. METHODOLOGY
In this study, the computing an annual sedimentvolume depositing in dam by mathematical model isnecessary to input the models; soil erosion model,
hydraulic model and sediment transport model, withhydrology data, hydrodynamic data, sediment data,
geographic data and topographic data.
(1) Data collection and data analysis
Hourly rainfall data from 1981-2004 werecollected by 8 rain gauges located on Managawa
river basin and the results from plotting double mass
curve of each rainfall stations are reliable.
Distribution of rainfall could be affected bytopographical data such as elevation and so on, theThiessen method was used to estimate rainfall
within the entire catchment.
Discharge and water level data are available inhourly to input as boundary condition in hydraulicmodel which outflows from Kumokawa Dam andSasougawa Dam are the upper boundaries and waterlevel at Managawa Dam is the lower boundary.
Geographic Information System (GIS) data used
for finding out parameters in soil erosion model are
Digital Elevation Model (DEM) 50m x 50m, land
use and soil type. For land use information, there areavailable in 1976, 1987, 1991 and 1997 however theFig.2 Land use 1997, 2 = Agricultures, 5= Forest, 6=Waste
Land, 7=Building, A= Small Building, B=Water Body

most of land use of the study area is forest and it
does not so much change by time as shown in Fig.2.
Calculating soil erosion, Modified Universal
Soil Loss Equation (MUSLE), in this study apply
with the Soil and Water Assessment Tool (SWAT)
that the watershed modeling framework isdelineated starting from the digital description of thelandscape as Digital Elevation Map (DEM), land
use and soil data sets using ArcView interface,
Spatial Analyst, with geomorphologic assessment
procedures to obtain soil erosion from each
sub-basin. Managawa river basin was divided in to 9
sub-basins which one sub-basin on upper
Sasougawa Dam is neglected because that dam willcapture all sediment from upper part. After that thecalculated daily sediment supply from each
sub-basin will be taken to input as lateral sedimentinflow to Managawa River model whichhydrodynamic (HD) and sediment transport (ST)models are calculated by MIKE 11 developed by
DHI Water and Environment. Flow chart of thisstudy is shown in Fig.3.
RainfallLand use

DEM

Input
MUSLE (SWAT model)
OutputSoil erosion
Discharge

X-section
River line

Sediment
Property

Input
Hydrodynamic and Sediment Transport model
OutputSediment volume
Fig.3 Scope of this study- 158 -

Soil type(2) Modified Universal Soil Loss Equation(MUSLE)The Soil and Water Assessment Tool (SWAT) isa long term distributed parameter model, designed
to predict the impact of land management practice ina watershed (Arnold et al., 1998). In this study, theSWAT ArcView interface (DiLuzio et al., 2001)
was used to write SWAT input files from GIS data
layers. SWAT model calculates soil erosion causedby rainfall-runoff process using MUSLE. The model
is a modified form of the USLE. The difference
between the two approaches that in MUSLE rainfall
energy factor is replaced with a runoff factor which
represents energy used in detaching and transporting
sediment. SWAT model requires a Digital Elevation
Model (DEM) from which it determines thedrainage network and divides the basin into
sub-basins defined by grid cells, spatially related
one to another, that each has geographic position in
the watershed defined by surface topography.
This study applies SWAT model only to find out
the soil erosion of each sub-basin at each outlet
point. The MUSLE is used in this study which is
given as Eq.(1). From MUSLE, the shortest timeinterval of output is daily and this study need daily
sediment yield data to input in sediment transportmodel.

Y = 11.8(Qs q p Aarea ) 0.56 K ⋅ C ⋅ P ⋅ LS ⋅ CFRG (1)Where Y is the sediment yield on a given day(ton), Qs is the surface runoff (mm), qp is the peakrunoff rate (m3/s), Aarea is area (km2), K is the USLE
soil erodibility factor, C is the USLE cover andmanagement factor, P is the USLE support practicefactor, LS is the USLE topographic factor and
CFRG is the coarse fragment factor. SWAT
estimates the surface runoff (Qs) with the SCS curve
number method and the peak runoff rate is
calculated with the rational method:qp =c ⋅ i ⋅ Aarea
3 .6

(2)

Where qp is the peak runoff rate (m3/s), Aarea isarea (km2), c is the runoff coefficient, i is the rainfall
intensity (mm/hr) and 3.6 is a unit conversion factor.
There are 8 sub-basins which sub-basin no.1, 2
and 3 are on the dam area so those sub-basins will
directly supply sediment into dam. The soil erosionof those areas from MUSLE will be directly sum up
to total sediment volume as shown in Fig.4 andFig.5 and the sub-basin No.9 is not supplying
sediment to Managawa Dam.

Fig.4 Sub-basins in this study
No.6
No.7
No.1
No.4

No.8

No.5

No.2
No.3

Sub-basin No.
8.2 km
10.6 km
14.4 km
Fig.5 Location that sediment yield of each sub-basin fromMUSLE supplied to the main river system(3) Hydrodynamic and Sediment Transportmodels
The hydrodynamic module (HD) contains animplicit, finite difference computation of unsteadyflows in rivers. The non-linear equations of open
channel flow (Saint Venant Equation) can be solved
numerical between all grid points at specified timeintervals for given boundary conditions.
The basic equation is governed by the continuity
and momentum equations:
∂Q ∂A
+
=q
∂x ∂t

(3)

⎛ Q2 ⎞
⎟⎟
∂⎜⎜ α
2
∂Q
⎞ n gA Q Q
⎛ ∂h
⎝ A ⎠
= 0 (4)++ gA⎜ + S 0 ⎟ +
4
∂t
∂x
⎠
⎝ ∂x
A2 R 3

Where Q is discharge (m3/s), A is cross section
area (m2), q is lateral inflow (m2/s), α
ismomentum distribution coefficient, h is water level(m), S0 is bed slope, n is Manning’s roughness
coefficient (s/m1/3) and R is hydraulic radius (m)The sediment transport computations are madein parallel with the hydrodynamic computations.
The sediment transport equations are solved in timeand space as an implicit function of the- 159 -

80
Changing in sediment volume (%)

corresponding values of the hydraulic parameters. In
this study, total load model Acker and White (1973)
presented a semi-empirical sediment transport modeis used for computation.
a) Boundary conditions, calibration andverification for Hydrodynamic model
Outflows from Kumokawa Dam and Sasougawa
Dam are set to upstream hydrodynamic boundaries
and water level at Managawa Dam is set to down
stream boundary as shown in Fig.6.
To calibrate Hydrodynamic model by changing
roughness coefficient which this study select year
1995 and 2004 for calibration and year 1998, 2002
and 2003 are for verification. The efficiency index(EI) for calibration is 94 % and for verification is
88% while roughness coefficients, Manning M, are20, 20 and 15 for branch 1, 2 and 3 in sequence.
b) Sensitivity analysis of sediment transportmodel
Daily sediment yield from MUSLE computation
will be supplied to the main river system at outlet
points of each sub-basin. Acker and White equationneed to input grain size diameter (D50). The
distributed grain size diagram of 4 sediment
samplings in Managawa Dam in 1998 is shown in
Fig.7. Sample 1, 2 and 3 were taken near dam
body and sample 4 was taken around upstream delta
deposits. Based on these data, the sedimenttransportation model will apply the approximate
value for D50 as 0.005 m in this study.

60
40
20
0

-20

0

0.002

0.004

0.006

0.008

0.01

-40
Grain size daimeter (m)Fig.8 Sensitivity analysis of grain size diameter effect toaccumulation sediment volume in 1995

For reference, sensitivity analysis of grain size
diameter is shown in Fig.8. When grain size
becomes finer, sediment accumulation volume
becomes larger.

4. RESULTS(1) Topographic results
This study has generated a watershed to 8
sub-basins as shown in Fig.4 excluding Sasougawa
dam basin. From 50m x 50m grid, we can obtain
topographic information as area, average slope andaverage elevation in Table 1.
(2) Soil surface erosion results
Average annual sediment yields (t/ha) for each
sub-basin during 1981 to 2004 were computed by
MUSLE with SWAT model as shown in Table 2.

Managawa Dam
D/S BD

Table 1 Topographic information of each sub-basin
Branch3
Sub
basin
1
2
3
4
5
6
7
8

Nagashima
stationKumokawa Dam
U/S BD
Branch1

Sasougawa Dam
Branch2
U/S BDFig.6 Hydrodynamic boundary conditions
100

Area
(km2)
9.39
12.76
11.54
9.84
27.35
8.01
17.64
53.81

Slope
(%)
0.44
0.52
0.52
0.45
0.45
0.49
0.42
0.44

Elevation
(m)
546
363
546
704
557
1089
705
629

Manning’s
n
0.035
0.035
0.035
0.035
0.035
0.035
0.035
0.035

80

Percent

Table 2 Annual average soil surface erosion from MUSLE
60

20

0
0.00001

Sub-basin
1
2
3
4
5
6
7
8

Sample1
Sample2
Sample3
Sample4Model400.00010.001
0.01
Size (m)0.1

1

Fig.7 Sediment distribution curve of 4 samplings inManagawa Dam, 1998

- 160 -

Average Erosion (t/ha/year)
9.66
12.04
12.08
9.86
10.39
10.94
9.26
10.58

(5)

Where Sy is the average sediment yield (m3), Ya
is the sediment yield (t/ha), Area is sub-basin area(km2) and σ is soil density about 2.65 t/m3.
(3) Sediment volume in dam
The volume of sediment depositing in the large
dams are measured every year in Japan. Sedimentvolume data of Managawa Dam is also available
from starting operation until recently year but somedata was disappear because of technical error as
shown in Table 3.
After sediment yield from each sub-basin wascomputed by MUSLE, those data were used to input
in total load transport model, Acker and White(1973). And then sediment will be routed along theriver and deposited in the dam reservoir. Computed
results are shown with observed ones in Table 3.
Observed data in 2004 was extremely large mainly
because of the Fukui heavy rainfall in July 18, 2004.

Computed Volume (m )42,304
75,10877,73066,52353,33773,66075,52554,324
93,670106,494
58,157
41,52566,901
52,65260,281
52,33942,950121,724
66,31550,65481,551
83,042
63,617
145,913∑ (ln( A ) − A
e =1

eo

2

ep

ln m

(6)

)

2

Where Aeo is the observed soil loss for event
e, Aep is the predicted soil loss and Aln m is themean value of ln( Aeo ) for all the events selected.
The Nash-Sutchliffe efficiency for thiscombined MUSLE and sediment transport model isabout 0.30 where a model efficiency of 1.0
represents a perfect fit of the model to observed
values. Negative values indicate that use of theaverage is a better predictor than the model(Nash-Sutchliffe, 1970). The Nash-Sutchliffe
efficiency for the simple MUSLE is -0.84 and thenthe present model of MUSLE with the river routing
system is increasing the efficiency.
RainfallComputed
Observed

5E

Year
Observed Volume (m )
1981
1982
1983
78,664
1984
15,768
1985
166,9071986
16,726
1987
23,477
1988
59,272
1989
79,652
1990
353,591
1991
1992
1993
175,980
1994
1995
106,271
1996
1997
4,812
1998
249,132
1999
41,822
2000
2001
101,227
2002
237,574
2003
36,322
2004
1,078,341(-) data is not available

3

Z ln = 1 − e =1n

eo

19 0
81
19
83
19
85
19
87
19
89
19
91
19
93
19
95
19
97
19
99
20
01
20
03

3

∑ (ln( A ) − ln( A ))Sediment Volume (cu.m)

Table 3 Observed and computed sediment volume, 1981-2004,
in Managawa Dam

n

Year

Fig.9 Annual rainfall, observed and computed accumulation
sediment volume- 161 -

Annual Rainfall (mm)σ

5 0 1 0 1 5 20 2 5 3 0 3 5
0 0 0 0 0 0 0 0 0 00 0 0∑ Ya ⋅ Area ⋅ 100

The computed sediment volumes in this study
show large differences with the observed data
because the observed data have some errors in someyear. Therefore, total accumulated sedimentvolumes were compared between them. Observedand computed total sediment volumes until year
2003 were 1,747,197 m3 and 1,560,381 m3
respectively, which error is about 10%. In someyear, the accumulative data are not much difference
as shown in Fig.9. Therefore, the sediment yield andsediment transport model in this study can be used
to estimate the sediment accumulation volume inManagawa Dam.
In order to determine efficiencies of the MUSLE
model, a logarithmic form of Nash-Sutchliffe modelis adopted, which is given by:

0

Sy =

5. DISCUSSION

3
2
2
3
1
+0 E+0 E+0 E+0 E+0 E+0
6
6
6
6
6
5

Sub-basin No. 2 and 3 show high erosion rate
because these slopes are so steep. The average
sediment yield from the whole watershed calculated
from Eq.(5) is about 60,161 m3/year.

reservoir sedimentation volumes and its tendency if
basic characteristics of each catchment such as
topographical, geological, meteorological conditions
may change.

Annual Rainfall (mm)

3500
3000
2500
2000
1500
1000

6. CONCLUSION

500
0
0

1

2

3

4

5

This study is an attempt to estimate the yearlyvolume of sediment deposition in Managawa Dam
using the Modified Universal Soil Loss Equation(MUSLE) with sediment transport model. The
MUSLE was developed for simulating the impact ofland management practices on eco-hydrologic
system (Arnold et al., 1995). The results of annual
sediment accumulating volume for this study area
show large differences with the observed data but
total volumes almost coincided very well. In orderto improve the model, other modifications may beneeded to compute sediment yield and transport
process in high flood periods. However, this model
can be used to estimate reservoir sedimentation
volumes and its tendency if catchment’s conditions
may change.

Annual Disharge (MCM)

Computed Sediment Volume
1000x(cu.m)

Fig.10 Relationship between Annual Discharge and Annual
Rainfall, 1981-2004
400
350
300
250
200
150
100
50
0
0

1

2

3

4

5

Annual Discharge (MCM)

Observed Sediment Volume
1000x(cu.m)

Fig.11 Relationship between Annual Discharge and Computed
Sediment Volume
400
350
300

ACKNOWLEDGMENT: The authors would liketo express our sincere gratitude to Managawa Dam
Office and NEWJEC for their willingness to supply
the necessary data for analysis in this research.

250
200
150
100
50
0
0

1

2

3

4

REFERENCES

5

1)

Annual Discharge (MCM)

Fig.12 Relationship between Annual Discharge and Observed
Sediment Volume

In order to improve the model, the relationshipamong annual rainfall, annual discharge, andobserved and computed sediment volumes areanalyzed. The annual runoff flowed into Managawa
Dam has good correlation with annual rainfall as
plotted in Fig.10. The annual sediment volume in
dam is not only depended on the soil surface
properties and rainfall but depended on discharge
also. Fig.11 and Fig.12 show that the computed
sediment volume from the model has moderately
correlation with annual discharge but the observed
one is varying more widely. R-square of computed
sediment volume and annual discharge is 0.34,
whereas the one of observed sediment volume andannual discharge is 0.16. Correlation may be
dropped by the large rainfall events and othermodifications are needed to compute sediment yieldand transport process in such high flood periods.
However, this study shows that this MUSLE withsediment transport model can be used to estimate

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- 162 -

(Received September 30, 2007)