rec Confidential Rainfall_Intenstiy_Charts1.xls,RAINFALL CHART-malacca, Page 1 of 2

DESIGN RAINFALL CHART FOR MALACCA

Rainfall Intensity-Duration-Frequency (IDF) Curves

Average rainfall intensity (mm/hr) for ARI and duration t (minutes) for an average return interval R (years)

is given by:

ln(RI t ) =a + b ln(t) + c (ln(t))

2 + d (ln(t))

3

(RI t ) = exp(a + b ln(t) + c (ln(t))

2 + d (ln(t))

3)

where a, b, c & d are constants

Table 13.A1: Coefficient for the IDF Equations (30 < t < 1000 min) for Seremban

ARI

(year) a b c d

2 3.7091 1.1622 -0.3289 0.0176

5 4.3987 0.7725 -0.2381 0.0112

10 4.9930 0.4661 -0.1740 0.0069

20 5.0856 0.5048 -0.1875 0.0082

50 4.8506 0.7398 -0.2388 0.0117

100 5.3796 0.4628 -0.1826 0.0081

5 5.743 145.9 5.698 144.7 6.905 175.4 8.278 210.3 9.346 237.4 10.915 277.2

Table of Rainfall Intensity

Duration, t 1-month 1-year

(min) in/hr mm/hr in/hr mm/hr in/hr mm/hr in/hr mm/hr in/hr mm/hr in/hr mm/hr

10.0 6.065 154.0 6.810 173.0 7.852 199.4 9.000 228.6 10.068 255.7 11.270 286.3

11.0 5.862 148.9 6.623 168.2 7.618 193.5 8.712 221.3 9.741 247.4 10.880 276.4

12.0 5.692 144.6 6.468 164.3 7.423 188.6 8.472 215.2 9.469 240.5 10.555 268.1

13.0 5.549 141.0 6.336 160.9 7.258 184.4 8.269 210.0 9.239 234.7 10.279 261.1

14.0 5.427 137.8 6.223 158.1 7.117 180.8 8.095 205.6 9.041 229.6 10.043 255.1

15.0 5.320 135.1 6.125 155.6 6.995 177.7 7.944 201.8 8.870 225.3 9.839 249.9

16.0 5.227 132.8 6.039 153.4 6.887 174.9 7.812 198.4 8.720 221.5 9.660 245.4

17.0 5.145 130.7 5.963 151.5 6.793 172.5 7.696 195.5 8.588 218.1 9.502 241.4

18.0 5.072 128.8 5.896 149.8 6.709 170.4 7.592 192.8 8.471 215.2 9.362 237.8

19.0 5.007 127.2 5.836 148.2 6.633 168.5 7.500 190.5 8.366 212.5 9.236 234.6

20.0 4.649 118.1 5.411 137.4 6.153 156.3 6.961 176.8 7.765 197.2 8.578 217.9

22.0 4.397 111.7 5.130 130.3 5.829 148.1 6.587 167.3 7.348 186.6 8.109 206.0

24.0 4.187 106.3 4.897 124.4 5.559 141.2 6.276 159.4 6.999 177.8 7.718 196.0

25.0 4.169 105.9 4.887 124.1 5.543 140.8 6.254 158.8 6.973 177.1 7.682 195.1

26.0 4.009 101.8 4.699 119.4 5.330 135.4 6.013 152.7 6.705 170.3 7.387 187.6

28.0 3.857 98.0 4.530 115.1 5.134 130.4 5.788 147.0 6.452 163.9 7.103 180.4

30.0 3.725 94.6 4.383 111.3 4.964 126.1 5.592 142.0 6.233 158.3 6.857 174.2

32.0 3.612 91.8 4.253 108.0 4.811 122.2 5.417 137.6 6.041 153.4 6.637 168.6

34.0 3.506 89.1 4.130 104.9 4.668 118.6 5.254 133.4 5.860 148.8 6.433 163.4

35.0 3.455 87.8 4.072 103.4 4.600 116.8 5.176 131.5 5.774 146.7 6.335 160.9

36.0 3.406 86.5 4.015 102.0 4.534 115.2 5.101 129.6 5.690 144.5 6.241 158.5

38.0 3.310 84.1 3.906 99.2 4.408 112.0 4.957 125.9 5.531 140.5 6.062 154.0

40.0 3.220 81.8 3.803 96.6 4.290 109.0 4.822 122.5 5.380 136.6 5.894 149.7

42.0 3.135 79.6 3.706 94.1 4.178 106.1 4.694 119.2 5.237 133.0 5.735 145.7

44.0 3.053 77.6 3.613 91.8 4.073 103.4 4.574 116.2 5.103 129.6 5.586 141.9

45.0 3.014 76.6 3.569 90.6 4.022 102.2 4.517 114.7 5.038 128.0 5.515 140.1

46.0 2.976 75.6 3.525 89.5 3.973 100.9 4.461 113.3 4.975 126.4 5.445 138.3

48.0 2.902 73.7 3.442 87.4 3.878 98.5 4.353 110.6 4.854 123.3 5.312 134.9

50.0 2.832 71.9 3.362 85.4 3.788 96.2 4.251 108.0 4.739 120.4 5.185 131.7

55.0 2.671 67.9 3.180 80.8 3.582 91.0 4.017 102.0 4.475 113.7 4.896 124.4

60.0 2.527 64.2 3.017 76.6 3.399 86.3 3.809 96.7 4.241 107.7 4.640 117.8

65.0 2.398 60.9 2.870 72.9 3.234 82.2 3.623 92.0 4.031 102.4 4.411 112.0

70.0 2.282 58.0 2.738 69.5 3.086 78.4 3.456 87.8 3.841 97.6 4.205 106.8

75.0 2.176 55.3 2.618 66.5 2.952 75.0 3.304 83.9 3.670 93.2 4.019 102.1

80.0 2.080 52.8 2.508 63.7 2.830 71.9 3.166 80.4 3.514 89.2 3.850 97.8

85.0 1.992 50.6 2.407 61.1 2.718 69.0 3.040 77.2 3.371 85.6 3.696 93.9

90.0 1.912 48.6 2.315 58.8 2.615 66.4 2.924 74.3 3.240 82.3 3.554 90.3

95.0 1.837 46.7 2.230 56.6 2.519 64.0 2.817 71.6 3.119 79.2 3.423 87.0

100.0 1.769 44.9 2.151 54.6 2.431 61.8 2.718 69.0 3.007 76.4 3.303 83.9

110.0 1.646 41.8 2.009 51.0 2.273 57.7 2.541 64.5 2.807 71.3 3.086 78.4

120.0 1.539 39.1 1.885 47.9 2.136 54.2 2.387 60.6 2.633 66.9 2.898 73.6

130.0 1.446 36.7 1.776 45.1 2.014 51.2 2.251 57.2 2.480 63.0 2.733 69.4

140.0 1.363 34.6 1.680 42.7 1.906 48.4 2.130 54.1 2.345 59.6 2.586 65.7

150.0 1.290 32.8 1.593 40.5 1.810 46.0 2.022 51.4 2.224 56.5 2.455 62.4

160.0 1.224 31.1 1.516 38.5 1.723 43.8 1.926 48.9 2.115 53.7 2.338 59.4

170.0 1.164 29.6 1.445 36.7 1.644 41.8 1.838 46.7 2.017 51.2 2.231 56.7

180.0 1.111 28.2 1.381 35.1 1.573 39.9 1.758 44.7 1.928 49.0 2.135 54.2

190.0 1.062 27.0 1.323 33.6 1.507 38.3 1.685 42.8 1.846 46.9 2.046 52.0

200.0 1.017 25.8 1.270 32.2 1.447 36.8 1.619 41.1 1.772 45.0 1.965 49.9

210.0 0.976 24.8 1.220 31.0 1.392 35.3 1.557 39.5 1.704 43.3 1.891 48.0

220.0 0.938 23.8 1.175 29.8 1.340 34.0 1.500 38.1 1.640 41.7 1.822 46.3

230.0 0.903 22.9 1.133 28.8 1.293 32.8 1.447 36.8 1.582 40.2 1.758 44.7

240.0 0.871 22.1 1.094 27.8 1.249 31.7 1.398 35.5 1.527 38.8 1.699 43.1

For t < 30 min, the following equation is used to find the rainfall intensity

P d = P 30 - F D (P 60 -P 30 ) where P 30 and P 60 are the 30-minute and 60-minute duration depths;

F D is the adjustment factor for storm duration

Table 13.3: Values of F D

Duration, t2P 24h (mm)

(min) < 100 120 150 > 180

5.0 2.08 1.85 1.62 1.40

6.0 1.92

7.0 1.76

8.0 1.60

9.0 1.44

10.0 1.28 1.13 0.99 0.86

20-year 50-year 100-year

All equations are based on the URBAN STORMWATER MANAGEMENT MANUAL FOR MALAYSIA

Vol 4 - Design Fundamentals

Coefficients of the IDF Polynominal Equations

2-year 5-year 10-year

rec Confidential Rainfall_Intenstiy_Charts1.xls,RAINFALL CHART-malacca, Page 2 of 2

11.0 1.18

12.0 1.09

13.0 0.99

14.0 0.90

15.0 0.80 0.72 0.62 0.54

16.0 0.70

17.0 0.61

18.0 0.51

19.0 0.42

20.0 0.47 0.42 0.36 0.32

22.0 0.38

24.0 0.28

26.0 0.19

28.0 0.09

30.0 0.00 0.00 0.00 0.00

2P 24h is the 2-year 24-hour rainfall depth