Simulation of a Dam Break Triggered Flood, the Case of Situ Gintung Disaster on March 27, 2009

MUSLIM WATER RESEARCHERS COOPERATION

MUWAREC-YK09
14 -15 December 2009
at Yogyakarta, INDONESIA

Editors:
Djoko Legeno
Sri Harto Brotowiryatmo
Data' Ahmad Fuad Embl
Abu Bakar Muhammad

~N1ROIMETA

'-' . The trajectories of the growth curves can be linear or non-linear In time. It depends on the nonlinearity parameter. P. in the following equations.

b={~
w~er

r. [oro < tb.:s;;r. and hb=hrJ- (hd- hbm { ; r, forO < tb s; 1'"

(1)

(b is time during the developing of the opening from the stan of the failure . Index m or over bar
accounts for the mean or the average value. The period of the development of the opening from sIan
to end , T, is another lmponant parameter determining the peak of the flood hydrogrdph.

According to Fread. 1988, [I], based on data of 43 dam failures having dam height of 5 m to 95 m,
there arc empirical relationship for the peak discharge, tht! period of opening development. and the
average width of the opening.

•

Qp=370(V,h,)

os

r=o{V,
]'"
,
2

h,

•

b=9.5k

0'

-

Qp=3.lb

o (V , b , t~

[ 1'"+ /

c/
C

'

[h; J

A

and C= 23.4 -d- .
b

(2)

*0

Where v" A" and are tht full storage level (FSL) reservoir volume, the FSL reservoir surface are,
and coefficient of breaking type respectively.
Evcn though the data are rather sparse. this relation can be used to make an initial guess of the peak
flood discharge. The hydrodynamic simulation of the flow leaving for downstream valley from the
reservoir through the opening can be simulated such as flow over a weir and the decrease of reservoir
....-ater can be simulated using either pool·levei storage assumption or dynamic routing approximation.
The 10 dynamic routing approximation. that is implemented in HEC-RAS, descretizes the St Venant
equations [2[.

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iutemal/(Jflai Conference on Sustainable Development for Water and Waste Water Treatment

aQ ~ a;{A+A,,)_q=o
aX
at
alsQ) v~f1
- -+
at

j

Q' / )
/ A

ax

oil

+ gi-+Sf+Se+S;)+L'=O
~ax

(3)

Where Q. A. and h arc the cross-sectional discharge. wetted area. and waler depth respectively. Sis
slope and index r. e, and i. account for friction , expansion or contraction, and mud viscosity
respectively. L· is the lateral inf!ow momentum influence and q is the lateral flow discharge per unit
length.
The data of Situ Gintung that are available for the simulation arc tile measured cross-se2"
"'00

."
""
.00
200

,

,

>200
26Mar 2009

2400

"'"

27 Mar 2009

2400

1200
l 8 Mar 2009

2400

1200
29 Mar 2009

2400

1200
10 Mar 2009

""

Fig. 5: Situ Glntung inflow hydrograph at March 26-27. 2009 used iII the simulation.
3.

RESULTS AND DISCUSSION

Sim>Jlations of the dam failure and the flood were done with the following setting. The opening of the
dam failure size is of 100 ft (30.5 m) width at the base and 28 ft (8.5 m) depth. Breach weir coeffi cient
15J is set to 2.6. The breach start time is set to be at 4:00 and the breach formation time is of 1 hour.
The breaking mechanism is assumed to be overtopping [6J. The innow hydrograph is set (0 reach the
peak discharge 2 hours before breaking. The Manning roughness coefficient of the dowllstream valley
is set to 0.03 [71 .
TIll! results of the simulation are as fol1 o\,\ls. The result of the nood routing triggered by the darn

breaking of Situ Gintung is shown in Figure 6 to Figure 14

277

Simulation of a Dam Break Triggered Flood, the Case ofSilu Glntung Disaster on March 27, 2009

WS 2JMAR2009 05.0

"'~

aa .... SI&

Fig. 6: Perspective view or th~simulaed
one hour and rorty minul~

reaches and water surrace e1evalion at hour 5;40, March 27, 2009,
after breaking.

1

1

"

i

EG 2!M"~09
O~
C!11 Z;MAR201:.>J 0nncl Diu3rce PI)

Fig. l' The long-seclion orsurrace water level allhe dam and along Ihe downstream rearh at hour 4:50 on
March 21. 2009.

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International Cooference on Sustalnable Development (or Water and Waste Water Tnatment

- '-

~-

.,-~

-

r

-'- --

r

g

i
I

Fig. 8: The long·section of surface water level at Ihe d am and along the downstrtam rtach al hour 6:50 on
March Z7, Z009
_ _ 01 _

.......

11$: 11
_~

,:I
~,

~

is

I

,

-- -

.

- -

-

1000

'"

i
~

,.,

'""1

~

~.
~

~

~

-

-

1-~

- - /0~

,

I\
I\

-

"w

\

•

1
1200

1Il00
,

~

1

'""

21M at2009

Fig. 9: Stage and now hydrograph at crou-seclian no 88 located 107.6 ft (32.8 111) downstream of the dam.

279

Simulation of a Dam Break Triggered Flood. the Case of Situ Gintung Disaster on March 27. 2009
"'en: t1an v I

KTVer. SIW glnwng Keacn : gflomgJ

1"(::':

I)"

,

400-,--------,,------,---;-------.,.--------;---,-18000

-IH

- -~,

380

360

340

{-1\ ~ .....

-

320

I\

300

Legend

16000

Stage

Fbw

14000

Missing Data
12000
10000
8000
6000
4000

i

---J

2000

280

260+-.,r_"T~i

0600

1200

1800
26Mar2009

I

Time

2400

I

0600
27Mar2009

Fig. 10: Stage and flow hydrograph at cross-section no 64 located 1551 ft (472.8 m) downstream of the
dam.
situ ginlung gintun;;! 3

20

Legend

Vel Chrj Max WS
Vel Right Ma x WS

E
0>
iY

Vel Le ft Max WS

15

0:;

>

:§

,0

u
0:;

>

500

1000

1500

2000

2500

Main Chame l Distance (ft)

Fig. 11: The long-section of maximum velocity along the downstream valley of Situ Gintung.

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International Conference on Sustainable Development for Water and Waste Water Treatment

Fig. 12: The maximum velocity at cross-sections and zones of left bank. channel. and right bank along the
downstream valley of Situ Gintung Dam.

The simulation result gives peak flood discharge 17 561 cuftls or about 497.3 m3/s at 32 m
downstream of the dam and 16 785 cuftls or about 475.3 m3/s. This numbers reach ten times of the
inflow flood peak discharge.
It can seen fron'! the simulation result that the maximum velocity reach nearly 19 ftls or about 6.3 m/s
in the downstream valley. On the bank. the maximum velocity reach nearly 15 ftls or about;) m/s. The
approximate value of the average velocity is of about 9 ftls or 3 m/s in the channel and 4.5 ftls or 1.5
m/s on the bank. T\lis such velocity has devastating effect on housing or other utilization of the area.
As for the water depth. at just downstream of the dam. the maximum water depth reaches up to 20 feet
or about 7 m. Further downstream the maximum water reaches up to 9 ft to 14 ft or about 3 m to 4.5
m. These values are measured from the bottom of the channel. From the photographs that were taken
just after the breach the water depth on the bank reaches up to 2.5 m to 3 m. Therefore. the simulation
results are in reasonable range~

281

Simulation of a Dam Break Triggered Flood, the Case of Situ Gintung Disaster on March 27, 2009

Fig. 13: Photograph of the evacuation period. It can be seen that the water surface reach the ceiling of
houses located on the bank. The flood water surface was still high after sun rise time.

Fig. 14: Photograph of severa! days after the breach. The water surface marks can be seen at the wall of
the mosque on the bank.

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International Conference on Sustainable Development for Water and Waste Water Treatment

4.

CONCLUSSION
1.

2.
3.
5.

The simulation of the flood dynamics triggered by the breaking of the Situ Gintung dam
gives reasonable results.
The result gives rough estimation of the maximum velocity and depth along the down stream
valley of the dam after the breach both on the channel and the banks.
The simulation can be implemented for other dams to give warning and gUidance for actions
to be enforced for land use management at downstream valley of the dam.

ACKNOWLEDGEMENT

The authors would like to express many gratitudes to the Organizing Committee of the Internationai
Conference on Sustainable Water and Waste Water Treatment for encouraging us to participate to the
conference and for accepting this paper in the very last moment. Many thanks are also addressed to
the computational assistants, Mr. Pudji Harsanto and Mr. Luqman who have given their help in
preparing the computational works during the study period, and to Mr. Roby and all other assistants
can not to be mentioned here, who have helped in preparing the needed data.
6.

REFERENCES

[1) Fread. "DAMBRK Model User Mannual", 1988.
[2) Brunner, Gary W, "HEC-RAS River Analysis System Hydraulic Reference Manual", 2008, US
Army Corps of Engineers, Hydrologic Engineering Center.
[3] PT Kwarsa Hexagon, "Studi Pendahuluan Penanganan Konservasi dan Pengelolaan Sumberdaya
Air di Wilayah Sungai Ciliwung-Cisadane", 2006, PPKSDA Ciliwung-Cisadane, Direktorat
Sungai dan Danau, DiUen Penataan Ruang dan Pengembangan Wilayah, Departemen Pemukiman
dan Prasarana Wilayah, Jakarta.
[4J Puslitbang SDA Depl. PU, "Laporan Penyelidikan Geoteknik Situ Gintung Pasca Keruntuhan" ,
2009.
l5) Fread, "NWS FLDWAV Model: The Replacement of DAMBREAK for Dam-Break Flood
Prediction", 1993, Proceedings: 10th Annual Conference of the Association of State Dam Safety
Officials, Inc., Kansas City, Missouri, September 26-29. Pp 177 - 184
[6J Brunner, Gary W, "HEC-RAS River Analysis System User's Manual", 2008, US Army Corps of
Engineers, Hydrologic Engineering Center.
[7] Chow, Ven Te, "Open Channel Hydraulics", 1992, McGraw-Hill.

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