O A RIGINAL RTICLES

748
Journal of Applied Sciences Research, 7(6): 748-752, 2011
ISSN 1819-544X
This is a refereed journal and all articles are professionally screened and reviewed
ORIGINAL ARTICLES
Flood Control in Karau Watershed, Center Kalimantan Province, Indonesia
Prima Hadi Wicaksono
Department of Water Resources, Faculty of Engineering, University of Brawijaya, Malang, Indonesia
ABSTRACT
This paper studied the ability of Talohan river capacity due to 2 years return period of design flood.
Talohan River was located in Barito Timur Regency, Center Kalimantan Province Indonesia. Downstream of
river was used as residence. Analysis of streamflow profile used software HEC-RAS 3.1.3. Result was used
to recommend kind of river improvement due to flood control such as improvement of river section or building
dyke.
Key words: river capacity, flood control
Introduction
Floods were natural disasters that could cause great economic damage, and loss of life and livehoods.
Estimation of discharge was vital and hence it had been a focuss of research for decades (Tayfur, Gokmen,
2011). When information on catchment characteristics was limited, the channel geometry method, which relates
streamflow data using regression analysis, was often employed for estimating flood discharge. Channel
geometry equations which relate discharge to channel width or channel cross sections were considered to be
most reliable. Once hydraulic geometry equations were defined for a stream, the cross-section area
measurement was all that was needed for estimating the discharge at an ungauged river (Tayfur, Gokmen,
2011).
The optimal combination of flood protection option was determined to minimize flood damages and
construction cost of flood control options along the river. The needed design flood values for decided options
especially when the lengths of recorded data were short, might require usage of various statistical distributions
(Oztekin, Tekin, 2011). These distributions enable us to predict values having return periods greater than the
lengths of the recorded series. Therefore, selection of the distribution most suitable to the recorded sample
series was imported from these aspects.
In recent years, the eefects of flood damages had motivated the development of new methodologies for
the simulation of the hydrology or hydraulic behavior of river systems to address territorial planning as well
as floodplain management and risk analysis (Camici, S., 2011). The estimation of design flood values to be
adopted for flood risk assessment or floodplain management represents a crucial factor; the value of floodprone areas and the assessment of dam safety rely on the estimation of the design flood for an assigned
probability of exeedance. The magnitude of floods depended generally on flood peak, volume, and duration.
Therefore, a multivariate analysis should be carried out for design flood estimation.
Materials and methods
Location of this study was in Karau watershed, Dusun Tengah District, Barito Tengah Regency, Eenter
Kalimantan Province, Indonesia. This area was fall between west latitude 1048’00” and east longitude
115009’03”. Area number of watershed was 2397.04 km2 and the length of main river was 182.8 km. Number
of population was 24.058 people, Dusun Tengah District was divided into 18 villages: Dayu, Tampa, Kalamus,
Patung, Ipu/Mea, Wuran, Saing, Rodok, Ampah, Ampah Dua, Netampin, Putai, Puri, Lenggang, UPT II, Lebo,
Unsum dan Baruyan. Location of study was as Figure 1 and 2.
Corresponding Author: Prima Hadi Wicaksono, Department of Water Resources, Faculty of Engineering, University
of Brawijaya, Malang, Indonesia
J. Appl. Sci. Res., 7(6): 748-752, 2011
749
Fig. 1: Location of study.
Fig. 2: Karau watershed.
Karau River and Talohen River was part of Barito River. Barito River was the biggest river in Kalimantan.
Parts of Barito River were fountioned as natural drainage during the rainy season. The capacity of Karau River
and Talohen River was reduced because of sedimentation, river stream was be wide or narrow so that the flow
was not so fluent. This condition was the impact of reduction land cover in the upstream watershed so that
increased erosion. Erosion would enter to river and it caused the capacity of river was reduced. The steps of
this study were as follows:
- To carry out homogeneity test for water level data
- To calculate maximized water level.
- To calculate design water level due to frequency analysis.
- To analyze design flood using rating curve.
- To analyxe profile of river flow using HEC-RAS version 3.1.3. The result was storage capacity and critical
points where occurd flood.
- To plan structure of flood control such as building dyke, improving river stream.
- To analyze profile of river flow using HEC-RAS version 3.1.3. (after handling effort)
- To determine the pattern of floof control due to the analysis result.
Coefficient of Manning Roughness:
River section was planned in the form of trapezoidal. Form of section was analyzed with Manning formula
as follow (Chow, Ven Te, 1997):
J. Appl. Sci. Res., 7(6): 748-752, 2011
Q
1 2 3 12
R S .A
n
Note:
Q =
n =
R =
A =
P =
S =
750
(1)
design flood (m3/s)
Coefficient of Manning Roughness (m.det)
A/P = radius of hydraulic
wet area of section (m2)
wet surrounded (m)
channel bed slope
Non Erosion Channel:
Flow velocity was based on aloowed maximized velocity (average maximized velocity which did not cause
polishing at channel wall. With assumed as uniform flow. Formula of Manning was used to calculate the
section at one control point (Raju, Ranga K.G., 1986):
V
1 2 3 12
R S
n
(2)
R
A
P
(3)
A  H ( B  z.H )
® for trapezoidal section
P  B  2H 1  z 2
Note:
V
R
A
P
H
B
N
=
=
=
=
=
=
=
® for trapezoidal section
flow velocity (m/s)
radius of hydraulic (m)
wet area of section (m2)
wet surrounded (m)
depth of water (m)
width of river bed (m)
coefficient of Manning Roughness
Result and Discussion
Fig. 3: River cross section TL-79 (location of AWLR).
Figure 3 was described river cross section TL-79 as the location of AWLR. Then average slope was
calculated due to long section as fllow:
Average slope (Irata-rata) =
Based on table of Manning (Chow, Ven Te, 1997), it was got n channel = 0,028 (sandy river bed). Then
it could be determined discharge per-metre of height and there was drawn rating curve (relation between water
level and discharge) as described in Table 1 and Figure 4.
J. Appl. Sci. Res., 7(6): 748-752, 2011
Table 1: Rating Curve.
H
Elev.
A
(m)
(m)
(m2)
1
2
3
0
41.46
0.00
1
42.46
6.29
2
43.46
21.38
3
44.46
39.54
4
45.46
60.27
5
46.46
84.80
6
47.46
113.57
7
48.46
148.47
P
(m)
4
0
24.78
34.76
40.45
47.40
56.03
65.91
85.13
751
n
5
0
0.028
0.028
0.028
0.028
0.028
0.028
0.028
R
(m)
6
0.00
0.25
0.62
0.98
1.27
1.51
1.72
1.74
slope
7
0
0.001
0.001
0.001
0.001
0.001
0.001
0.001
v
(m/s)
8
0.000
0.453
0.817
1.112
1.325
1.489
1.623
1.636
Q
(m3/s)
9
0.000
2.844
17.462
43.978
79.876
126.252
184.369
242.957
Fig. 4: Rating Curve.
Design flood at any return period for upstream Karau was described as Table 2. Based on Table 2, it
could be calculated design flood at downstream Karau (Table 3) and Talohen watershed (Table 4) due to
comparison of watershed number area. Number area of upstream Karau was 2397.040 km2, downstream Karau
was 2350.681 km2, and Talohen watershed was 46.359 km2..
Table 2: Design flood at upstream Karau.
Return period (year)
H (m)
1
1.220
2
5.807
5
7.070
10
7.732
25
8.376
50
8.890
Elevation (m)
42.680
47.267
48.530
49.192
49.836
50.350
Q (m3/s)
5.055
178.109
279.164
342.429
411.071
470.924
Table 3: Design flood at downstream Karau.
Return period (year)
H (m)
1
0.907
2
4.318
5
5.258
10
5.750
25
6.229
50
6.611
Elevation (m)
42.367
45.778
46.718
47.210
47.689
48.071
Q (m3/s)
4.957
174.665
273.765
335.806
403.121
461.816
Table 4: Design flood at Talohen watershed.
Return period (year)
H (m)
1
0.907
2
4.318
5
5.258
10
5.750
25
6.229
50
6.611
Elevation (m)
42.367
45.778
46.718
47.210
47.689
48.071
Q (m3/s)
4.957
174.665
273.765
335.806
403.121
461.816
Geometry of Data:
Data of cross section was described as coordinates which represented as station and elevation from left
side to the right one. It meant from upstream to downstream (Figure 5).
Design Flood:
Input discharge for HEC-RAS was design flood with return period of 1,01 year, 2 years, 5 years, 10 years,
J. Appl. Sci. Res., 7(6): 748-752, 2011
752
25 years and 50 years. Maximed water level due to AWLR recorder during the 10 years was 8,15 m and water
level with 25 years of return period was 8,376 m. Recapitulation of sections which was not able to store flood
was as Table 5.
Fig. 5: Geometry of Karau watershed.
Table 5: Recapitulation of river section that was not able to store flood.
Discharge
Section that was not able to store flood (TL)
Q 2 th
30, 31, 39, 41, 47, 48, 52, 54, 55, 62, 63, 73-75, 83, 88, 89,
Q 5 th
6, 7, 9-11, 13-16, 18-22, 28-32, 37, 39-43, 53-51, 52, 54, 55, 62-63, 71-75, 83, 87-89
Q 10 th
TP1, 1-16, 18-23, 26-33, 35, 37, 45, 47-49, 51, 52, 54-59, 62, 63, 71-75, 77-78, 83-89, 91
Q 25 th
TP1, 1-67, 69, 71-75, 77-85, 87-89, 91, 93, 95-98
Q 50 th
TP1, 1-100
Conclusion:
Based on analysis as above, it could conclused as follow: some sections at Karau Watershed and Talohen
Watershed was not able to store discharge mainly in the downstream. Therefore it was needed some
improvement efforts to control flood. It could be used return period of 25 years for design. Improvement of
river sections had to be carried out at TL 54, 55, 60-63, 65-76, 82 to 93, 96 to100. The average width of
improvement was 15 m. Dyke had to be build at TL 1-16, 18-33, 37, 39, 41 to 45, 47, 48, 52, average height
of dyke was1,5 m from natural sand.
References
Camici, S., A. Tarpanelli, L. Brocca, F. Melone and T. Moramarco, 2011. Design Soil Moisture Estimation
by Comparing Continuous and Stirm-Based Rainfall-Runoff Modelling. Research Institute for GeoHydrological Protection, Natinal Research Council, Via Madona Alto 126, 05127 Prugia, Italy.
Chow, Ven Te, 1997. Hidrolika Saluran Terbuka. Jakarta: Erlangga.
Oztekin, Tekin, 2011. Estimation of the Parameters of Wakeby Distribution by a Numerical Least Squares
Method and applying it to the Annual Peak Flows of Turkish Rivers. Journal of Water Resource Manage,
25: 1299-1313.
Raju, Ranga K.G., 1986. Aliran Melalui Saluran Terbuka. Jakarta: Erlangga.
Tayfur, Gokmen and Singh, P. Vijay, 2011. Predicting Mean amd Bankfull Discharge from Channel CrossSectional Area by Expert and Regression Methods. Journal of Water Resource Manage, 25: 1253-1267.