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• Frequency Analysis ( Hydraulic structures-Flood)
• Introduction- method- data- results
18908-37759-1-PB.pdf
Civil Engineering Forum Volume XXII/2 - May 2013
1365
ANALYSIS OF HYDRAULIC FLOOD CONTROL STRUCTURE AT PUTAT BORO RIVER
Ruhban Ruzziyatno Directorate General of Water Resources, Ministry of Public Works, Republic of Indonesia
Email: [email protected]
ABSTRACT
Putat Boro River is one of the main drainage systems of Surakarta city which drains into Bengawan Solo river. The primary problem when flood occur is the higher water level of Bengawan Solo than Boro River and then backwater occur and
inundates Putat Boro River.
The objective of the study is to obtain operational method of Putat Boro River floodgate to control both inflows and outflows
not only during flood but also normal condition. It also aims to know the Putat Boro rivers floodgate operational function to
reduce inundation. Putat Boro river water level variation and Bengawan Solo river water level variation were used for
simulation of Boro river floodgate routing. The simulation used 10-year inflows, 50-year inflows, and 100-year inflows return
period and Boro water level variation are +82.50 m, +83.00 m and +84.00 m. The results of the study show that the effective opening of floodgate are 0.35 m - 0.55 m for +82.05 m of Bengawan Solo
water level, 0.50 m – 0.65 m for +82.55 m of Bengawan Solo water level and 0.70 m – 0.85 m for +83.48 m of Bengawan Solo
water level, for reducing water level of Boro river flooding.
Keywords: Flood, drainage systems, floodgate and flow routing.
1 INTRODUCTION
Flood that occurs periodically in dense populated area,
particularly in urban area has caused damages and
losses to physical structures, even loss of human lives.
Flood in 1966 inundated almost 2/3 of Surakarta city
including urban area. Inundation attained 1 m up to 2
m depth and caused 90 people died.
Boro River is one of many drainage canals flowing
into Bengawan Solo River. Its catchment comprises
Sewu, Pucang Sawit, Jagalan, Purwodiningratan, and
Tegalharjo sub district, Jebres district, Surakarta city.
Flood that occurs almost every year is affected by
backwater phenomena. It occurs when water level of
Bengawan Solo River is higher than ground level of
catchment of Boro River. The flood control of Putat
Boro River has three gates.
2 FLOOD ROUTING AND FLOW OVER GATE
SYSTEM
Flood routing is used to determine flood hydrograph
at a point based on monitored hydrograph at another
point upstream on a watercourse. Flood hydrograph
can be traced from riverbed or a dam (Soemarto,
1989). There are some flood routing methods, a well-
known one is Muskingum developed by Mc Carthy
(1938 in Ven Te Chow, 1989) as shown in Equation
(1)
tQtIS .. (1)
where S is storage change in the i-th time interval
(m3), I is volume of inflow (m3), Q is volume
of outflow in the i-th time interval (m3), and t is
interval of duration (second, hour, day).
The foregoing equation can be elaborated as follows.
t
S QQII nnnn
)(
2
1 )(
2
1 11 (2)
t
H AQQII nnnn
)(
2
1 )(
2
1 11 (3)
HAtQQtII nnnn .).( 2
1 ).(
2
1 11 (4)
where In is inflow in the beginning of t (m3), In+1 is
inflow in the end of t (m3), Qn is outflow in the
beginning of t (m3), Qn+1 is outflow in the end of t
m3), A is the water surface area at an observed time
(m2), and is change in water elevation during t (m).
The following equation is used for flood routing
analysis through sliding floodgate.
12... ghbaKQ (5)
where Q is discharge (m3/s), K is sinking flow
factor, is discharge coefficient, a is floodgate-
opening (m), b is floodgate width (m), g is
acceleration due to gravity (m/s2), and h1 is depth of
water in front of floodgate above threshold (m).
Volume XXII/2 - May 2013 Civil Engineering Forum
1366
Value of K and µ for sinking flow factor and
discharge coefficient (Ministry of Public Works,
1986) are provided in Figure 1 and Figure 2,
respectively. Peak discharge is analyzed by using
rational method (Sri Harto, 2000), (Chow, 1964) as
follows
Qp = k C I A (6)
where Qp is peak discharge (m3/s), k is 0.278, C is
runoff coefficient which depends with characteristic
of the catchment area (0 C 1) (Chow, 1988), I is
rainfall intensity during time concentration
(mm/hour), and A is watershed area (km2).
Figure 1. Value of K for sink flow factor.
Figure 2. Value of for discharge coefficient.
Kirpich (1940) developed a formula to analyze time
concentration (Chow et al, 1988) as follows.
385.0 2
.1000
.87.0
S
L tc (7)
where tc is time concentration (hour), L is river length
(km), and S slope of the river (m/m).
3 METODOLOGICAL APPROACH
The research uses some secondary data obtained from
several source, there are Main Project of Bengawan
Solo River Region Development, Bengawan Solo
River Basin organization, and Public Works Office of
Solo (see flowchart in Figure 3).
a) Watershed map is gained from visual earth map
with scale of 1:25.000 that is resulted storage
characteristic as shown in Figure 4.
b) Daily rainfall maximum data which is used to
analyze design rainfall with specified return
period, then flood hydrograph can be presented as
in Figure 5.
c) Putat Boro watershed characteristic
d) Daily water level maximum in Jurug obtained
from AWLR.
Figure 3. Research flow chart.
0.5
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
h1/a
Civil Engineering Forum Volume XXII/2 - May 2013
1367
Figure 4. Inundated area and storage volume of Boro River.
Figure 5. Flood hydrograph of Boro River with several
return periods.
4 RESULTS AND DISCUSSIONS
Simulation of flood analysis through Putat floodgate
applies return period of 10, 50, and 100 years and
+84.00 m maximum water level in Boro River
(Hupstream). If it is exceeded, there will be the overflow
from Boro River). Peak discharges are presented
below.
4.1.1 Inflow with a return period of 10 years
Based on 16.14 m3/s Qp Boro, + 82.50 m, + 83.00,
and + 84.00 m Boro River level, and + 82.05 m, +
82.55, + 83.48 m Bengawan Solo (Hdownstream) River
level, varying results of Putat floodgate-opening are
obtained as shown in Table 1.
Table 1. Simulation result with Qp-10 years
Hupstream
Hdownstream
+ 82.50 m + 83.00 m + 84.00 m
+ 82.05 m 0.20 m -
0.40 m
0.20 m -
0.50 m
0.20m -
0.50 m
+ 82.55 m - 0.20 m -
0.55 m
0.20 m -
0.60 m
+ 83.48 m - - 0.20m -
0.75 m
Graphic results are depicted from Figure 6 to Figure
11
Figure 6. Q10-Hupstream=82.5 m and Hdownstream=82.05 m with variation in floodgate-opening.
Figure 7. Q10- Hupstream =83.00 m and Hdownstream =82.05 m
with variation in floodgate-opening.
0 2 4 6 8
10 12 14 16 18 20 22 24 26
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Time (hour)
Qp-2 Qp-5 Qp-10 Qp-25 Qp-50 Qp-100
Time concentration
Volume XXII/2 - May 2013 Civil Engineering Forum
1368
Figure 8. Q10- Hupstream =84.00 m and Hdownstream =82.05 m
with variation in floodgate-opening.
Figure 9. Q10- Hupstream =83.00 and Hdownstream =82.55 m with variation in floodgate-opening.
Figure 10. Q10- Hupstream =84.00 m and Hdownstream =82.55 m
with variation in floodgate-opening.
Figure 11. Q10- Hupstream =84.00 m and Hdownstream =83.48 m
with variation in floodgate-opening.
4.1.2 Inflow with a return period of 50 years
From 21.87 m3/s Qp Boro, + 82.50 m, + 83.00, and +
84.00 m Boro River level, and + 82.05 m, + 82.55, +
83.48 m Bengawan Solo (Hdownstream) River level,
varying results of Putat floodgate-opening are
obtained as shown in Table 2.
Table 2. Simulation result with Qp-50 years
Hupstream
Hdownstream + 82.50 m + 83.00 m + 84.00 m
+ 82.05 m 0.2 m -
0.45 m
0.2 m -
0.55 m
0.2 m -
0.55 m
+ 82.55 m - 0.2 m -
0.60 m
0.2 m -
0.70 m
+ 83.48 m - - 0.2 m -
0.90 m
Graphic results can be seen from Figure 11 to Figure
17
Figure 12. Q50- Hupstream =82.50 m and Hdownstream =82.05 m with variation in floodgate-opening.
Figure 13. Q50- Hupstream =83.00 m and Hdownstream =82.05 m
with variation in floodgate-opening.
Civil Engineering Forum Volume XXII/2 - May 2013
1369
Figure 14. Q50- Hupstream =84.00 m and Hdownstream =82.05 m
with variation in floodgate-opening.
Figure 15. Q50- Hupstream =83.00 m and Hdownstream =82.55 m with variation in floodgate-opening.
Figure 16. Q50- Hupstream =84.00 m and Hdownstream =82.55 m
with variation in floodgate-opening.
Figure 17. Q50- Hupstream =84.00 m and Hdownstream =83.48 m
with variation in floodgate-opening.
4.1.3 Inflow with a return period of 100 years
From 24.63 m3/s Qp Boro, + 82.50 m, + 83.00, and +
84.00 m Boro River level, and + 82.05 m, + 82.55, +
83.48 m Bengawan Solo (Hdownstream) River level,
varying results of Putat floodgate-opening are
obtained as shown in Table 3.
Table 3. Simulation result with Qp-100 years
Hupstream
Hdownstream + 82.50 m + 83.00 m + 84.00 m
+ 82.05 m 0.2 m -
0.45 m
0.2 m -
0.45 m
0.2 m -
0.60 m
+ 82.55 m - 0.2 m -
0.60 m
0.2 m -
0.70 m
+ 83.48 m - - 0.2 m -
0.90 m
Graphic are depicted from Figure 18 to Figure 23
Figure 18. Q100- Hupstream =82.50 m and Hdownstream =82.05
with variation in floodgate-opening.
Figure 19. Q100- Hupstream =83.00 m and Hdownstream =82.05 m
with variation in floodgate-opening.
Figure 20. Q100- Hupstream =84.00 m and Hdownstream =82.05 m
with variation in floodgate-opening.
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Figure 21. Q100- Hupstream =83.00 m and Hdownstream =82.55 m
with variation in floodgate-opening.
Figure 22. Q100- Hupstream =84.00 m and Hdownstream =82.55 m
with variation in floodgate-opening.
Figure 23. Q100- Hupstream =84.00 m and Hdownstream =83.48 m with variation in floodgate-opening.
The results of simulation show that for water level of
Bengawan Solo River (Hdownstream) + 82.05 m and 10
years of Qp , the floodgate-opening that can lower
water level of Boro River maximally is 0.35 m - 0.45
m (can be seen at Figure 6, Figure 7, and Figure
8),while the floodgate-opening for 50 years of Qp is
0.40 m - 0.5 m (can be seen at Figure 12, Figure 13,
and Figure 14), and about 0.40 m - 0.55 m for 100
years of Qp (can be seen at Figure 18, Figure 19, and
Figure 20).
When Bengawan Solo elevation (Hdownstream) rises up
to + 82.55 m due to 10 years of Qp, the floodgate-
opening for maximum level reduction is
approximately 0.50 m - 0.55 m (can be seen at Figure
9 and Figure 10), 0.55 m - 0.65 m for 50 years of
Qp(see Figure 15 and Figure 16), and 0.55 m - 0.65
m for 100 years of Qp (see Figure 21 and Figure 22 ).
For + 83.48 m Hdownstream and 10 years of Qp , the
floodgate-opening that can result maximum reduction
of Boro River level is approximately 0.70 m (see
Figure 11), 0.85 m for 50 years of Qp, (see Figure 17),
and 0.85 m for 50 years of Qp (see Figure 23). If the
floodgate is opened more than those values, it may
cause backwater from Bengawan Solo River
(Hdownstream).
5 CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
According to the result of flood routing simulation
towards Putat Floodgate using 10 years, 50 years, and
100 years of return period of flood hydrograph with
variation in water elevation of Boro River, +82.50 m,
+83.00 m dan +84.00 m, it can be concluded that :
a) For +82.05 m Bengawan Solo Rivel level, the
effective floodgate-opening is 0.35 m – 0.55 m
b) For +82.55 m Bengawan Solo Rivel level, the
effective floodgate-opening is 0.50 m – 0.65 m
c) For +83.48 m Bengawan Solo Rivel level, the
effective floodgate-opening is 0.70 m – 0.85 m
d) Putat Floodgate can be operated with the
maximum floodgate-opening as long as no
backwater occurs
5.2 Recommendations
The followings are some recommendations to
optimize flood control system as the main goal.
a) Operating management of Putat Floodgate should
be improved by referring to the gate operational
guide.
b) Procurement of pump needs to be realized to
prevent backwater occurrence due to the overflow
from Bengawan Solo River.
REFERENCES
Chow, V.T., Maidment, M.R., and Mays, L.W.
(1988), Applied Hydrology, McGraw-Hill, New
York.
Ministry of Public Works. (1986). Standar
Perencanaan Irigasi KP-04 [Irrigation Design
Standard KP-04], Publisher Agency of Public
Works Ministry, Jakarta.
Soemarto. (1989). Hidrologi Teknik [Hydrology
Engineering], PPMTT, Malang.
Sri Harto, Br. (2000). Hidrologi – Teori, Masalah dan Penyelesaian [Hidrology – Theory, Problems and
Solving], Nafiri, Yogyakarta.
