Starting from MITS 2.4.16.0, rainfall data of Sabah and Sarawak are implemented according to “Estimation of Design Rainstorm in Sabah and Sarawak (Revised and Updated 2018)”. Over 100 of raingauge locations are added for the East Malaysia region and are in conjunction with MSMA 2nd Edition. It is crucial especially in Sabah area, whereby it was limited only to MSMA 1st edition in stormwater management design previously. Other new items such as temporal pattern based on cluster categories and areal reduction factor (ARF) are also in the new version.
i. Raingauge Location
New Raingauge Locations are added in Sabah and Sarawak along with the map attached. The list of parameters for both Sabah and Sarawak can be referred to in Table 4.1 and Table 4.2, respectively.
ii. Areal Reduction Factor
Areal Reduction Factor (ARF) is a value applied to rainfall of a certain area and duration to give the areal rainfall of the same duration and return period. ARF is implemented based on Table 6.12 and 6.13 for Sabah and Sarawak region, respectively.
Take Kuching, Sarawak for example. Given the coefficient as stated below, the area of catchment is 10000 ha (100 km2) and 360 minutes (6-hr) duration for 10 years ARI.
ƛ = 84.6865, K = 0.1820, θ = 0.4599, ɳ = 0.7092
Rainfall Intensity (mm/hr) = \frac { (84.6865){ (10) }^{ 0.1820 } }{ { (6+0.4599) }^{ 0.7092 } }
= 34.30 mm/hr
Based on Table 6.13, the ARF of 100 km2 area for 6 hours is 0.772.
Areal Rainfall Intensity (mm/hr) = 0.772 x 34.30
= 26.48 mm/hr
MiTS auto calculates the rainfall intensity based on raingauge location, area and duration.
iii. Temporal Patterns
There are nine cluster regions in East Malaysia with 4 and 5 regions located in Sabah and Sarawak respectively with different Temporal Patterns. The nine clusters created are shown in Figure 6.1. Each of the clusters results in different temporal patterns, which are tabulated in Table 6.2 to Table 6.10.
Calculation and Temporal Patterns created in MiTS are reflected upon the region assigned in the input.
