International Journal of Engineering Business
and Social Science
Vol. 1 No. 04, April 2023, pages: 331-339
e-ISSN: 2980-4108, p-ISSN: 2980-4272
https://ijebss.ph/index.php/ijebss
331
Analysis of the Effect of Land Use on Flood Discharge in the
Pangkajene River Basin, Pangkajene Regency and the Islands
Muhammad Rizal Zainuddin
1
, Mary Selintung
2,
Rita Lopa
3
Civil Engineering Study Program, Hasanuddin University Makassar
Email: rizalmuh2023@gmail.com
Submitted: 08-03-2023 Revised: 12-03-2023, Publication: 03-04-2023
Keywords
Abstract
Flood Discharge, Land
Use, Pangkajene
Watershed
Changes in land cover that occur have an impact on hydrological conditions in a
watershed. The hydrological condition referred to by the amount of watershed output is
the discharge which describes the amount of water. This study aims to determine the
effect of changes in land cover on river flow in the Pangkajene watershed. Data were
analyzed using hydrological analysis and land use change. The results showed that there
was an increase in design flood discharge of ±18.83 m³ in each return period. Changes
in land use that occur are the area of rice fields, ponds, and settlements increases while
the area of forest decreases. The increase in the value of flood discharge is not significant
because changes in land use have not changed much either.
© 2023 by the authors. Submitted
for possible open access publication
under the terms and conditions of the Creative Commons Attribution (CC BY SA)
license (https://creativecommons.org/licenses/by-sa/4.0/).
1. Introduction
Rapid human growth causes the comparison between population and agricultural land to be unbalanced. This
causes the ownership of agricultural land to become increasingly narrow. This situation often encourages some farmers
to encroach on forests and other unproductive land as agricultural land. All of this has an impact on the occurrence of
critical land which stems from less than ideal land cover by vegetation that is able to withstand erosion. Land cover
under conditions of intensive and less conservative ownership and farming methods is one of the problems that are
interrelated with erosion and sedimentation (Linsley Jr et al., 1975).
If a variety of trees are cut down in a watershed, this means a reduction in ground cover vegetation and an
increase in the area of the exposed area. If there is precipitation, there will be an increase in the hitting power of rainfall,
runoff, and erosion will occur. Increased erosion and landslides in the catchment area will eventually increase the
sediment load carried by rainwater. Disruption to a watershed ecosystem can vary, especially from the inhabitants of
a watershed, namely humans. If the function of a watershed is disrupted, the hydrological system which is the main
function of the watershed is disrupted, the capture of rainfall, absorption and storage of water is reduced, or the
distribution system becomes wasteful (Lopa & Shimatani, 2013). This event will cause an abundance of water in the
rainy season, and vice versa greatly reduced water in the dry season. This causes fluctuations in river discharge between
the dry season and the rainy season to differ sharply. So if the river discharge fluctuations are very sharp, it means that
the watershed function is not working properly, if this happens it means that the quality of the watershed is low (Lopa,
2012). In terms of rainfall, the watershed area can be divided into 2 (two), namely areas that function as infiltration
332 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS
IJEBSS Vol. 1 No. 04, April 2023, pages: 231-339
areas and areas that function as drainage areas. Whether the area functions or not is closely related to land use
(Rachmayanti et al., 2022).
Administratively, the Pangkajene watershed is in the Saddang river area (WS) in South Sulawesi Province
with a watershed area of 440 km2 and a river length of 30 km. The Pangkajene River functions as a catchment area, a
source of raw water, for agricultural and fishery activities. Apart from that, on the Pangkajene River there is also the
Tabo-tabo Dam which is located in Tabo-tabo Village (Raudkivi, 2013), Bungoro District, Pangkep Regency, where
this dam is a dam that controls the Pangkajene River flood which is capable of providing raw water of 33.34 l/s.
Geographically, the Pangkajene River is located between 4°50'55.6” South Latitude – 4°45’40” South Latitude and
119°30’41.4” East Longitude – 119°41’12” East Longitude (Lubis, 2016).
2. Materials and Methods
This research is quantitative descriptive (Lawrence Neuman, 2014). The purpose of this type of research is to
make systematic, factual and accurate descriptions, drawings or drawings of the facts, characteristics and relationships
between the phenomena studied . The research location is the Pangkajene Watershed for land use changes to flood
discharge in Pangkep Regency, South Sulawesi Province.
Figure 1. Map of Research Locations
Data source
In this study, two data sources were used, namely primary data, namely data obtained from the research location,
namely topographic maps, hydroclimatological data, forest data, agricultural and plantation data, settlement data,
population data, land use change data, the above data were processed. to be used as a reference in determining the
flood discharge that occurs due to changes in land use. Secondary data is data obtained from literature or previous
research reports about the research location. Besides that, library data was also collected, namely collecting
theoretical data, documents, obtained through library books, training, magazines, journals, and other books that were
in accordance with the research material (Sudarto & Mukhlisin, 2010).
Data Analysis Techniques
In this study, the flood discharge conditions analyzed were runoff and flow discharge. The data used is data for 10
years from 2009 – 2018. Meanwhile, annual land use data is obtained from the large growth rate of land area per
year from 2009 – 2018.
IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 333
IJEBSS Vol. 1 No. 04, April 2023, pages: 231-339
Figure 2. Research Flowchart.
3. Results and Discussions
Pangkajene Watershed Land Use
The development of the population and its activities, the progress of the economy of the people of Pangkep
Regency and the influence of advances in technology and information as well as national and global changes encourage
changes in the selection of settlement locations and activities, the development of activities and functions of a location
and region will ultimately change the use of space (Marasabessy et al., 2020).
Changes in the use of settlement space for housing needs, trade and service buildings, and other settlement
equipment occur in line with the population distribution of existing conditions, so that the use of residential space will
be more expansive from existing locations.
334 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS
IJEBSS Vol. 1 No. 04, April 2023, pages: 231-339
Figure 3. 2009 Pangkajene Watershed Land Use Map
Figure 4. 2018 Pangkajene Watershed Land Use Map
Figure 5. Graph of Changes in Land Use in 2009 and 2018
The results of the analysis of changes in land use in the Pangkajene Watershed in 2009-2018 can be seen in Figure
5, you can see changes in land cover where there has been an increase in land in the Water Body from 3.16 Km² to
3.18 Km², Shrubs 114.10 Km² to 115 .17 Km², Forest 121.94 Km² to 105.88, Residential 2.08 Km² to 6.31 Km²,
Agriculture 106.73 Km² to 109.72 Km², Rice fields 79.19 Km² to 82.73 Km², Tambak 9, 36 Km² became 13.25 Km²,
Open Land 3.51 Km² became 3.56 Km², and mining land became new land of 0.24 Km² in the last 10 years.
Regional Average Rainfall
Based on the distribution of rain station locations that affect the Pangkajene watershed, the rain stations used are Tabo-
tabo station, Pangkajene station, and Leang Lonrong station. From the results of regional rain analysis usingpolygon
Teissen, then the maximum daily rainfall obtained as shown in the table.
Table 1. Average Rainfall in the Pangkajene Watershed Area.
IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 335
IJEBSS Vol. 1 No. 04, April 2023, pages: 231-339
No
Year
Rainfall Max
Will
Rain
Yes
Group
those
Lon
two
Coefficient
0.38
0.11
1
2009
221
151
178.11
2
2010
182
164
139.22
3
2011
172
117
218.53
4
2012
157
80
127.06
5
2013
138
110
103.89
6
2014
89
87
71.56
7
2015
113
102
82.84
8
2016
123
91
94.59
9
2017
81
118
99.02
10
2018
178
142
154.66
Design Rainfall
Design rainfall is the largest annual rainfall with a certain probability that may occur in an area at a certain return
period. In this calculation the design rainfall is calculated using frequency analysis, calculating the statistical magnitude
of the relevant data (X, s, Cv, Cs, Ck).
X Average = S Xi
n
= 1269.49
10
= 126.95 mm/year
Standard Deviation :
Sx = S ( Xi - X )²
n - 1
0.5
Sx = 1929.59 = 46.30
9
Coefficient of Variation :
v = Sx = 46.30 = 0,36
336 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS
IJEBSS Vol. 1 No. 04, April 2023, pages: 231-339
X 126.95
Coefficient Skewness:
Cs = n S (Xi – X)³
(n-1) (n-2) Sx³
= 10 601574.85 = 0.84
(9) (8) 99252,85
Kurtosis Coefficient :
Ck = n² S (Xi – X)⁴
(n-1) (n-2) Sx⁴
= 10² 93005686.25
(9) (8) (7) 4595406,82
= 4.01
Based on these statistical values, the appropriate billing can be estimated.
Quality Statistics:
Normal : Cs = 0 ; Ck = 3
Log Normal : Cs = 3 Cv
Gumbel : Cs = 1,14 ; Ck = 5,4
Log - Pearson Type III : If everything is not there.
Based on the analysis of statistical parameters belonging to the Log distribution type -Pearson Type III.
Data is sorted from smallest to largest (or vice versa).
Table 2. Probability Data.
No.
X
m(n+1)
%
(mm)
1
82.8444
0.0909
9.0909
2
94.5919
0.1818
18.1818
3
99.0220
0.2727
27.2727
4
103.894
6
0.3636
36.3636
5
127.056
8
0.4545
45.4545
6
139.222
3
0.5455
54.5455
7
154.660
0
0.6364
63.6364
8
178.110
0
0.7273
72.7273
9
218.534
9
0.8182
81.8182
10
0.0000
0.9091
90.9091
IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 337
IJEBSS Vol. 1 No. 04, April 2023, pages: 231-339
Furthermore, it can be estimated that the rain is planned according to the anniversary period that you want to
plan and the frequency factor (K) according to the selected distribution. By using the formula X(t) = Xaverage + K .
The following Sdevs are obtained by Plan Rain with various return times.
Table 3. Rain Plans With Various
Time Repeat
Further testing with Chi-squared.
K = 1 + 3.32 log n
= 1 + 3.32 log 10
= 4.32 = 4 Classes
Table 4. Calculation of the Chi Square Test for Log DistributionPearson Type III
Flow Coefficient
One of the important concepts in flood analysis is the runoff coefficient (runoff) which is usually denoted by C. The
coefficient C is defined as the ratio between the peak surface runoff rate and the rainfall intensity (Riswal & Sukri,
2020).
Table 5. Flow coefficient (C)
Land Cover
Coefficient
Forest
0.20
Agriculture
0.5
Check the Bushes
0.22
Plantation
0.475
Ricefield
0.525
Settlement
0.9
pond
0.6
Open Land
0.6
338 e-ISSN: 2980-4108 p-ISSN: 2980-4272 IJEBSS
IJEBSS Vol. 1 No. 04, April 2023, pages: 231-339
From the results of the analysis, the flow coefficient for land use in 2009 was C = 0.360, the flow coefficient
for land use and flow coefficient for land use in 2019 was C = 0.372. The results of the flow coefficient will be used
as an evaluation in calculating the design flood as part of the data input in the calculation of effective rainfall.
Analysis of Planned Flood Discharge on Land Use.
To find out changes in flood discharge due to changes in land use in the Pangkajene Watershed, it is necessary
to analyze the 2009 and 2018 surface runoff discharges and then make a comparison. In the analysis of the calculation
of the planned flood discharge, the method used is the Nakayasu HSS method.
Figure 6. Pangkajene Watershed Flood Hydrograph in 2009
Figure 7. Pangkajene Watershed Flood Hydrograph in 2018
Further, a comparison of the flood debits of the 2009 and 2018 plans was carried out to find out the extent of
the influence of land use changes. A recapitulation of the flood debit and the amount of change from 2009 to 2018 can
be seen in the table.
Table 5. Maximum Flood Debt Summary and Changes from 2009 to 2018
IJEBSS e-ISSN: 2980-4108 p-ISSN: 2980-4272 339
IJEBSS Vol. 1 No. 04, April 2023, pages: 231-339
4. Conclusion
Changes in land use in the Pangkajene watershed caused an increase in the runoff coefficient (C) in 2009 by 0.360
and in 2018 by 0.372. The increase in the value of the flow coefficient will affect the increase in flood discharge. The
results of the design flood discharge analysis show that in 2009 and 2018 an increase in flood discharge was obtained
by 3.45% or ± 18.83 m3/s in each return period.
It is hoped that there will be similar and ongoing research on this matter, especially in watersheds (DAS) which
have a high potential for changing land use into residential areas as a result of the supporting infrastructure development
itself.
5. References
Lawrence Neuman, W. (2014). Social research methods: Qualitative and quantitative approaches. Pearson.
Linsley Jr, R. K., Kohler, M. A., & Paulhus, J. L. H. (1975). Hydrology for engineers.
Lopa, R. (2012). An evaluation of river restoration effectiveness in a housing land development area. The University
of Kyushu, Japan, Dissertation.
Lopa, R., & Shimatani, M. (2013). Belajar dari Pengalaman Jepang dalam Upaya Mengendalikan Banjir dengan
Restorasi Sungai. Proceeding HATHI.
Lubis, F. (2016). Analisa frekuensi curah hujan terhadap kemampuan drainase pemukiman di kecamatan kandis.
SIKLUS: Jurnal Teknik Sipil, 2(1), 34–46.
Marasabessy, M., Pallu, M. S., Lopa, R. T., & Thaha, M. A. (2020). Development of flood forecasting model and
warning systems at Way Ruhu–Ambon. IOP Conference Series: Earth and Environmental Science, 419(1),
12115.
Rachmayanti, H., Musa, R., & Mallombassi, A. (2022). Studi Pengaruh Perubahan Tata Guna Lahan Terhadap Debit
Banjir Dengan Menggunakan Software HEC HMS: Studi Kasus DAS Saddang. Jurnal Konstruksi: Teknik,
Infrastruktur Dan Sains, 1(1), 1–9.
Raudkivi, A. J. (2013). Hydrology: An advanced introduction to hydrological processes and modelling. Elsevier.
Riswal, K., & Sukri, A. S. (2020). Kajian Koefisien Aliran Terhadap Perubahan Debit Banjir Pada DAS Karalloe
Dengan Aplikasi ArcGIS seman. TIK, 6, 1–8.
Sudarto, S., & Mukhlisin, M. (2010). PENGARUH PERUBAHAN TATA GUNA LAHAN TERHADAP
PENINGKATAN ALIRAN PERMUKAAN: STUDI KASUS DI DAS GATAK, SURAKARTA. Jurnal
Purifikasi, 11(1), 29–40.