1st International Conference on Engineering and Technology Development ISSN 2301-6590

(ICETD 2012)
Universitas Bandar Lampung
Faculty od Engineering and Faculty of Computer Science

Analyze The Characteristic of Rainfall and Intensity

Duration Frequency (IDF) Curve at Lampung Province
Susilowati #1)
#1
Department of Engineering ,Bandar lampung University (UBL)
susilowatirifat@yahoo.co.id, susilowatirifat@ubl.ac.id

Abstract— This research was done to analyze the characteristic of more interested in analyzing the frequency of extreme climatic
rainfall based the short term duration of rainfall data at BMG events on rainfall intensity and different duration by using IDF
Maritim Lampung station, BMG Raden Inten II Bandar Lampung curve.
station, Masgar Tegineneng Climatology station and Kotabumi This research is aimed to analyze the rainfall characteristics
Geophysical station. From the results of the research intensity in Lampung province. The result is IDF curves that can be used
duration frequency (IDF) curve will be made based on: (1) Analysis to calculate the flood discharge plan which is used for planning
of rain distribution frequency of short term rainfall data from each
flood control building.
statios. (2) Analysis of rainfall intensity for every rain duration in
particular measurement uses Van breen intensity method and
Hydrological system is affected by extreme events like floods
Hasper der weduwen intensity method then least square (kuadrat and droughts. Magnitude of extreme events is inversely to the
kecil) is used to calculate rainfall intensity approach by Talbot, frequency of the occurrence, remarkable extreme events are
Sherman and Ishiguro formula’s, the purpose is to determine the very rare. The purpose of frequency analysis related to the
equality of rainfall intensity to targeted region. extreme events which relate to frequency of occurrence through
From the result of the research, it could be summarized as follows the application of probability distribution. Frequency analysis
;(1) The data of rainfall used is short term rainfall data (5, 10, 15, based on statistical properties of the past events data was done
30, 45, 60, 120 minutes, 3 hours, 6 hours and 12 hours) and as to obtain the rainfall probability in the future with the
annual maximum series, (2) Type of distribution that appropriate
assumption that the statistical properties of the future rainfall are
with all observation station is Log Pearson Type III Distribution,
(3) The rainfall intensity of Van Breen method used Talbot
still equal to the statistical properties of rainfall in the past.
equality, it is used as reference to form IDF curve. The intensity In statistic, there are four frequency distributions that are
equality was valid only to data of rain in all observation year at widely used in hydrology, they are: normal distribution, log-
every station. (4) The IDF Curve showed that high rainfall intensity normal, Gumbel and Log Pearson III. Each distribution has
happen in short duration (5) the IDF curve can be used to distinctive properties, so that the rainfall data must fit tested
determine planning flood by using rational method. with the statistical properties of each distribution. The selection
of an incorrect distribution can lead to significant estimation
Keywords — Rainfall, intensity, duration and frequency errors, either overestimated of underestimated (Sri Harto 1993).
In the diversion process of rain into streams, there are some
traits that are important to be considered, they are: rain intensity
I. INTRODUCTION (l), rain duration (t), the depth of rain (d), frequency (f), and the
Earth’s globally changing climate conditions due to the influence area of rain (Soemarto, 1987). High intensity of rain
greenhouse effect has an impact on weather conditions / means rain or water depth per unit time. In other words, rainfall
Indonesian regional and local climate extreme. The real impact intensity states the amount of rainfall in the short term that
of climate aberration (extreme climate) is the increased intensity describes rain per hour. To obtain the value of rain intensity in a
of rainfall, flash floods and tide flood (rob), local hurricane / particular place, the measuring instrument used should be able
tornado, increased urban temperatures, droughts and landslides. to record the amount of rainfall volume and duration until the
For the first time in 23 years Bandar Lampung city was attacked rain had stopped. In this case the measuring instrument used is
by flash flood. The floods caused by 4 hours rain since Thursday automated rain measuring instrument. (Asdak, C, 1995).
evening (12.18.8). In addition to threatening floods, landslides
also threaten some region such as West Lampung, Tanggamus, To change rainfall into rain intensity can be used various
and Way Kanan. methods including:
These climate change conditions have the potentiality to 1. Van Breen Method
affect the engineering design standards in the future. In planning Van Breen formula is based on the assumption that the
the flood control building (drainage channels, levees, etc) the rainfall duration in java is concentrated for 4 hours with an
data of rainfall input is needed. Experts in civil engineering effective rate of 90% from total rain in 24 hours. The
(water), geomorphology, and land and water conservation are formula is:

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1st International Conference on Engineering and Technology Development ISSN 2301-6590
(ICETD 2012)
Universitas Bandar Lampung
Faculty od Engineering and Faculty of Computer Science

90%R 24 Xt = Selected maximum daily rainfall,

I= ………………(1) (mm/ 24 hour)
4
To determine the intensity according to Hasper-Der
Note, I = Rain intensity (mm/hour) Weduwen used the following formula:
R24 = Maximum rainfall (mm/24 hour) Rt
I = ………………..(6)
Based on Van Breen curve pattern in Jakarta, the amount of
t
rainfall intensity can be approximated by the equation: Note,
I = Rain intensity ( mm/hour)
54R T  0,007R T
2
Rt = Rainfall (mm),
IT = …….(2) t = time (hour)
t c  0,31R T
Note, Analysis on the relationship of two important parameters
IT = Rain intensity (mm/hour) in the form of intensity and duration can be associated
when concentration tc statistically with a frequency of occurrence. The graphical
tc = Concentration time (minute) presentation of this relationship is a curve of intensity-
RT = Maximum daily rainfall duration-frequency (IDF) (Loebis, 1992). This curve can be
(mm/24 hour) used for the runoff calculation and for peak discharge
calculation when using rational formula by selecting the
2. Hasper Der Weduwen rainfall intensity proportional to the time of rainfall runoff
This method is the result of investigation conducted in from the top to the observed point in the downstream of the
Indonesia by Hasper and Der Weduwen. The formula is drainage area (waktu tiba = arrival time). This curve also
obtained based on the daily rainfall tendency which are shows the magnitude probability of rainfall intensity for the
grouped on the basis of the assumption that the rain has duration of rainfall at random.
symmentrical distribution of the rainfall duration (t) is less In the planning of waterworks, it is necessary to plan the
than 1 hour and rainfall duration are from 1 – 24 hours. amount of water discharge to be channeled through the
waterworks. For the water discharge volume to be
channeled, we can determine the specific flood discharge
The formula used is: which is large enough. When rainfall data is available, then
1 < t ≤ 24 , so the flood estimation can be done with rational equation,
which is expressed in the following formula (Chow, 1964):
11300t  R t 
…..........…(3)
t  3,12 100 
R=
Qp = 0,278 C I A ……......(7)
Note,
11300  R t  Qp : Top discharge (m3/second)
0 < t ≤ 1 , so R = …….(4)
t  3,12 100  C : Coefficient run off, based on
Watershead characteristic
and I : Rainfall intensity, for rain duration equals
concentration duration (tc) (mm/hour)
 1218t  54  A : Area of Watershead a (Km2)
Rt = Xt   ................(5)
 X t (1  t )  1272t  II. RESEARCH METHOD
Rainfall data used in this research were taken from automated
Note, rain measuring instrument Hellman type in station:
t = Rain duration (minute)  Lampung Maritime BMG Station (observed 2000 – 2001;
R, Rt = rainfall according to Hasper-Der Weduwen 2003 – 2008)

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1st International Conference on Engineering and Technology Development ISSN 2301-6590
(ICETD 2012)
Universitas Bandar Lampung
Faculty od Engineering and Faculty of Computer Science

 Raden Inten II BMKG Station Bandar Lampung (observed TABLE 3.1

RAINFALL DATA AT MARITIME LAMPUNG BMG STATION
2001 – 2008)
 Masgar Climatology Class II Station Tegineneng (observed
2004 – 2008)
 Geophysics Station Kotabumi (observed 1998 – 2005, 2007
– 2008)

To get the IDF curve at each observation station, analysis

procedure was performed as follows:
1. Determine the maximum daily rainfall for each year
data
2. Determine the statistical parameters of data that has
been sorted from smallest to largest, are: mean,
standard deviation (S), coefficient of variation (Cv),
coefficient of skewness (Cs), coefficient of kurtosis Source: Maritime Lampung BMG Station
(Ck).
3. Determine the appropriate type of distribution that is TABLE 3.2
based on statistical parameters. RAINFALL DATA RADIN INTEN II BMKG STATION BANDAR
LAMPUNG
4. Tested with Chi-Square and Smirnov Kolmogorov to
determine whether the selected type of distribution is
appropriate.
5. Calculate the amount of rainfall design for a specific
time based on selected type of distribution, expressed
by a simple formula as follows (Haan, 1979):
XT = X + KT. S ……………….. (8)
Note :

XT = rain design with time T year

X = average magnitude
S = standard deviation
KT = frequency factor for time T year
6. Calculate rainfall planning to be rainfall intensity using
Van Der Breen and Hasper-Der Weduwen for the Source: Radin Inten II BMKG Station, Bandar Lampung
duration of each rain.
TABLE 3.3
7. Calculate rainfall intensity approach using least squares RAINFALL DATA AT MASGAR CLIMATOLOGY CLASS II STATION
method that are Talbot formula, Sherman and Ishiguro. TEGINENENG
This method was used with the intention of
determining the intensity of rain which is closest to
regional planning / planning area.
8. Depiction of the daily rainfall intensity curve with a
certain time.

III. DISCUSSION

Rainfall data used in this research is a maximum daily rainfall

data derived from automated rain measurement instrument type
Hellman at some stations as follows:
Source: Masgar Climatology Class II Station, Tegineneng

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1st International Conference on Engineering and Technology Development ISSN 2301-6590
(ICETD 2012)
Universitas Bandar Lampung
Faculty od Engineering and Faculty of Computer Science

TABLE 3.4 TABLE 3.6

RAINFALL DATA GEOPHYSICS KOTABUMI BMG STATION RAINFALL INTENSITY, DURATION, AND FREQUENCY AT RADIN
INTEN II BMKG STATION BANDAR LAMPUNG

Source: Calculation Result

TABLE 3.7
Source: GeophysicsStation, Kotabumi
RAINFALL INTENSITY, DURATION, AND FREQUENCY AT MASGAR
CLIMATOLOGY STATION
The result of frequency analysis in this research is the type of
distribution which is in accordance with statistical parameter at
all observation stations are Log Pearson Distribution Type III
and has been
tested with Chi_Square Test and Smirnov Kolmogorov test.
Rainfall intensity values for all four observation stations shown
in table 3.5 to table 3.8

TABLE 3.5
RAINFALL INTENSITY, DURATION & FREQUENCY AT MARITIME
LAMPUNG BMG STATION

Source: Calculation Result

TABLE 3.8
RAINFALL INTENSITY, DURATION, AND FREQUENCY AT
GEOPHYSICS STATION KOTABUMI

Source: Calculation Result

Source: Calculation Result

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1st International Conference on Engineering and Technology Development ISSN 2301-6590
(ICETD 2012)
Universitas Bandar Lampung
Faculty od Engineering and Faculty of Computer Science

Results of rainfall analysis in this research were as follows:

1. Based on the observation on all stations showed that
rainfall intensity in Van Breen method using Talbot
equation was used as a reference to create IDF curve,
because it has the smallest different value. The
intensity equation is valid only for the rain data in the
year of observations at each station.
2. From the rainfall intensity tables, it can be seen that the
smaller rainfall duration the bigger rainfall intensity
value.

From this research, four IDF curve are obtained (Frequency

Duration Intensity Curve) for each return period (2, 5, 10, 25,
50, and 100 years) from each observation station, as shown in
Fig. 1 to 4.

Fig. 2. IDF Curve BMG Radin Inten II Station Lampung

Station

Fig. 1. IDF Curve BMG Maritime Lampung Station

Fig. 3. IDF Curve Masgar Climatology Station

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1st International Conference on Engineering and Technology Development ISSN 2301-6590
(ICETD 2012)
Universitas Bandar Lampung
Faculty od Engineering and Faculty of Computer Science

IV. CONCLUSSION

From the discussion and the results of the research, it can be

concluded as follows:
1. Rainfall used are short term rainfall data (5, 10, 15, 30,
45, 60, 120 minutes, 3 hours, 6 hours, and 12 hours)
and an annual maximum data (annual maximum
series).
2. Type of distribution which is in accordance with all
observation stations is Log Pearson Type III
distribution.
3. Rainfall intensity in Van Breen method using Talbot is
used as a reference to create the IDF curve.
4. From the IDF curve showed that high intensity rainfall
happened in a short duration.
5. IDF curve can be used to determine the flood plan by
using rational method.
Fig. 4. IDF Curve Geophysics Station Kotabumi REFFERENCES
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