Manuel Gómez Valentín Universitat Politècnica de Catalunya … · 2011-05-25 · Manuel Gómez...
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Design storms Manuel Gómez Valentín Universitat Politècnica de Catalunya E.T.S. Ing. de Caminos, Canales y Puertos
Transcript of Manuel Gómez Valentín Universitat Politècnica de Catalunya … · 2011-05-25 · Manuel Gómez...
Design storms
Manuel Gómez ValentínUniversitat Politècnica de CatalunyaE.T.S. Ing. de Caminos, Canales y Puertos
Rain data needed for the study
Information: level of hyetograph
Minimal level of information: a curve IDF/DDF
In general, poor suitable information fordirect use in studies of urban hydrology
Level of usual information
Information of daily rainfall (24 hours time step) Level of insufficient detail (problems in urban areas in
a few hours or even minutes) Difficulty of disagregrating information To propose relationships between rains of duration D
and those of duration 24 hours Problems due to that the rainfall data in 24 hours can
be a consequence of 2 or more rain events
How to obtain a curve IDF
Available in some observatories Obtained from the analysis of a historical time
series of rain events (20/30 years minimum) If it is not available: Options to establish synthetic IDF (Spanish
procedure in 5.2.IC regulation)
Synthetic IDF
Instruction 5.2. I.C.
Use of the maximum rainfall in 24 hours for theconsidered return period P24
Regionalización of the rain from a certain factor, variable according to the geographical situation ofthe observatory
Expression of the synthetic IDF
Expression proposed (studies of the CEH)
Relation between duration and average maximumintensity
12828
24 1.0
1.01.0
.24
)(),(
D
h RFTPTDI
Maximum rainfall in 24 hours
Information from the information provided in the meteorological zonal centers
Utilization of a statistical extreme distributions(Gumbel, SQRT-ET)
All of them give practically equal results forlow return periods
Regional factor Ratio between the maximum hourly average
intensity, and the daily average intensity
24
1
II
FR
Design storms
DISCHARGERAINFALL
BASINQ (t)I (t)
1.- Historical rainfall or time series generated from statistical methods
2.- Design storm, obtained frominformation included in the curve IDFIntensity - Duration - Frequency.
Rainfall patterns
Defined the rain duration, and known thequantity of rainfall associated to the returnperiod T, it is necessary to distribute along thetime the above mentioned amount of rain
To study guidelines of temporal distribution ofrainfall that repeat themselves in different rainevents– Huff's distribution– Distribution of the Soil Conservation Service
Huff's distributionR
ainf
all
Time
1 º 2 º 3 º 4 º
Rai
nfal
l
Time
1 º 2 º 3 º 4 º
Rai
nfal
l
Time
1 º 2 º 3 º 4 º
Rai
nfal
lTime
1 º 2 º 3 º 4 º
Distribution of accumulated rainfall depending ontime that fits to the first quartil, and for different probability values
Time of duration of the storm in %
Rai
nfal
lacc
umul
ated
in %
Probability
Rainfall patterns - Huff's temporal distribution
10% de Probabilidad
0
10
20
30
40
50
60
10 20 30 40 50 60 70 80 90 100
Tiempo de Duración de la tormenta en %
Lluv
ia to
tal e
n %
90% de Probabilidad
0
10
20
30
40
10 20 30 40 50 60 70 80 90 100
Tiempo de Duración de la tormenta en %
Lluv
ia to
tal e
n %
50% de Probabilidad
0
10
20
30
40
10 20 30 40 50 60 70 80 90 100
Tiempo de Duración de la tormenta en %
Lluv
ia to
tal e
n %
S.C.S's distribution.
0.0
0.5
1.0
0 3 6 9 12 15 18 21 24
Tiempo (horas)
Frac
ción
de
la L
luvi
a en
24
hora
s
IA
I
The IIIrdThe IInd
Time (hours)
Acu
mul
ated
rain
fall
Rainfall patterns of the SCSHIETOGRAMA TIPO I
0.0
0.1
0.2
0.3
1 3 5 7 9 11 13 15 17 19 21 23
Tiempo de tormenta (horas)
Frac
cion
de
la ll
uvia
cai
da
en 2
4 ho
ras
HIETOGRAMA TIPO IA
0.0
0.1
0.2
1 3 5 7 9 11 13 15 17 19 21 23
Tiempo de tormenta (horas)
Frac
cion
de
la ll
uvia
cai
da
en 2
4 ho
ras
HIETOGRAMA TIPO II
0.0
0.1
0.2
0.3
0.4
0.5
1 3 5 7 9 11 13 15 17 19 21 23
Tiempo de tormenta (horas)
Frac
cion
de
la ll
uvia
cai
da
en 2
4 ho
ras
HIETOGRAMA TIPO III
0.0
0.1
0.2
0.3
1 3 5 7 9 11 13 15 17 19 21 23
Tiempo de tormenta (horas)
Frac
cion
de
la ll
uvia
cai
da
en 2
4 ho
ras
Rainfall patterns: summary
Interesting approach, but with proper pattternsextracted at the local level
Do not use patterns derived from differentobservatories: reflex of meteorological situationsthat do not match with our study zone
Obtention of local patterns from registers of rainevents on few years (5-8)
Design storms from IDF curves
2.1. constant Rain or in block2.2. triangular Storm2.3. storm type Sifalda2.4. Double Triangle rainfall2.5. Keifer-Chu rainfall2.6. method of the Alternated Blocks
Constant rain or in Block
Inte
nsity
DurationT
Curve I.D.F
V = IT * T
IT
Triangular rain
maxIh 2
Tdrta .
Tdrtb ).1(
2TdhTdIV max
Sifalda rain type
0.25 D0.25 D D
I
0.5 D
2.3 Im
1.0 Im
0.15 Im 0.20 Im
B
To C
VOLUME OF RAIN
A = 14.11 %B = 56.44 %C = 29.45 %
Double triangle rainfall
4 h.3 h.
P2 (3 years P.R.)
P1 (10 years P.R.)
D
I
30 mint
Keifer-Chu type
fTdcI emed
2
).1(.fTd
fTdecIe
e
Tormenta de Diseño KEIFER-CHU
01
Td
(1-r).Tdr.Td
tbta
Inte
nsid
ad d
eP
reci
pita
cion
Tiempo
i
ib= f(tb)ia= f(ta)
dd Tr
bbrT
aa dttfdttfP)1(
0
)(
0)()(
)()( bad
tftfdTdP
f (ta) = f (tb) for any Td, then:
Also: medd ITP
d
meddmedd dT
diTIdTdP
Differing:
Defining:
Replacing:
Example: Calculation with Keifer-Chu
031.19)(44.477,4
)/(
mintI hramm
Tiem. Abs Tiem. Rel. Intendidad Precipitación(min) (min) (mm/hra) (mm)0.00 30.00 13.645.00 25.00 17.88 1.31
10.00 20.00 24.45 1.7615.00 15.00 35.44 2.5020.00 10.00 55.93 3.8122.50 7.50 73.58 2.7025.00 5.00 101.10 3.6427.00 3.00 136.00 3.9529.00 1.00 192.65 5.4830.00 0.00 235.27 3.5731.00 1.00 192.65 3.5733.00 3.00 136.00 5.4835.00 5.00 101.10 3.9537.50 7.50 73.58 3.6440.00 10.00 55.93 2.7045.00 15.00 35.44 3.8150.00 20.00 24.45 2.5055.00 25.00 17.88 1.7660.00 30.00 13.64 1.31
Precipitación Total 57.43
r = 0.50Td = 60 minc = 4,477.44e = 1f = 19.031
rt
rtTd ba
1
2
).1(.fTd
fTdecIe
e
0
50
100
150
200
250
0 10 20 30 40 50 60
Tiempo (min)
Inte
nsid
ad (m
m/h
ra)
r = 0.50r = 0.25
Hietograma of the obtained rain
Alternating blocks method
I5 'I10 'I15 '
Calculation process
Rain of the block 1 I5 ' = I1 Rain of the block 2: I10’ x 10 ' = I1 x 5 ' + I2 x 5 ' Rain of the block 3 I15’ x 15 ' = I10’ x 10 ' + I3 x 5 ' = I1 x 5 ' + I2 x 5 ' + I3
x 5 '
I5 ' =I1
I2=I10’ x 10’- I1 x 5’
Example: Calculation with the Alternating Blocks method
031.19)(44.477,4
)/(
mintI hramm
Duración Intensidad Lluvia Acum Incre. Lluvia Int. Bloque Int. Bloquemin mm/hra mm. mm. mm/hra ordenado5.00 186.32 15.53 15.53 186.32 16.6710.00 154.23 25.70 10.18 122.14 22.5415.00 131.57 32.89 7.19 86.25 32.1620.00 114.71 38.24 5.35 64.15 49.5825.00 101.69 42.37 4.13 49.58 86.2530.00 91.32 45.66 3.29 39.47 186.3235.00 82.87 48.34 2.68 32.16 122.1440.00 75.85 50.57 2.23 26.72 64.1545.00 69.93 52.44 1.88 22.54 39.4750.00 64.86 54.05 1.61 19.28 26.7255.00 60.48 55.44 1.39 16.67 19.2860.00 56.65 56.65 1.21 14.56 14.56
Intensity(mm/h)
Inc. ofrainfall (mm)
Acc Rainfall(mm)
Intensity(mm/h)
Duration(min)
Ordenatedblock
Hyetograph of Intensities
16.67 22.5432.16
49.58
86.25
186.32
122.14
64.15
39.4726.72 19.28 14.56
0
50
100
150
200
1 2 3 4 5 6 7 8 9 10 11 12
Time step of 5 minutes
Inte
nsity
(mm
/h)
