IDF Curve — Rainfall Intensity
Ref: MSMA 2nd Edition (2012), Chapter 2, Eq. 2.2; constants from Table 2.B1 (Appendix 2.B)
Source: all station constants (λ, κ, θ, η) are taken verbatim from MSMA 2nd Edition (2012) Table 2.B1 in Appendix 2.B (high ARI, 2–100 year, storm duration 5 min – 72 hr). The manual publishes the equation with duration in hours; this calculator accepts minutes for convenience and converts internally. Use Custom mode to enter site-specific constants from Table 2.B1 (high ARI) or Table 2.B2 (low ARI, 0.5–12 month).
i = (λ × T^κ) / (d + θ)^η
Ref: MSMA 2nd Edition (2012), Chapter 2, Eq. 2.2; constants from Table 2.B1 (Appendix 2.B)
Rainfall Station
Active IDF Constants
λ = 61.976 κ = 0.145 θ = 0.122 η = 0.818
Single-Point Lookup
Common: 2, 5, 10, 20, 50, 100 years (valid 2–100 yr per Table 2.B1)
Valid range 5 min to 72 hr (4320 min) per MSMA Eq 2.2
Rainfall Intensity
—mm/hr
Engineering aid only — final design must be endorsed by a registered PE under BEM.
IDF Table — Intensity (mm/hr)
| Duration (min) | 2-yr | 5-yr | 10-yr | 20-yr | 50-yr | 100-yr |
|---|---|---|---|---|---|---|
| 5 | 250.2 | 285.7 | 316.0 | 349.4 | 399.0 | 441.2 |
| 10 | 189.4 | 216.3 | 239.1 | 264.4 | 302.0 | 333.9 |
| 15 | 153.9 | 175.7 | 194.3 | 214.9 | 245.4 | 271.3 |
| 30 | 101.1 | 115.4 | 127.6 | 141.1 | 161.2 | 178.2 |
| 60 | 62.4 | 71.2 | 78.8 | 87.1 | 99.5 | 110.0 |
| 120 | 37.0 | 42.3 | 46.8 | 51.7 | 59.1 | 65.3 |
| 180 | 27.0 | 30.8 | 34.1 | 37.7 | 43.1 | 47.6 |
| 360 | 15.6 | 17.8 | 19.7 | 21.7 | 24.8 | 27.5 |
Station: Kuala Lumpur — Ibu Pejabat JPS (Stn 3116003) | λ=61.976, κ=0.145, θ=0.122, η=0.818