design rainfall Ph 6012 710 2620

design rainfall Ph 6012 710 2620

http://msmaware.com/blog/documentation/


Phone 6012 710 2620





Manual Saliran Mesra Alam Malaysia (MSMA), or the Urban Stormwater Management Manual for Malaysia is the urban stormwater drainage design guide first distributed by the Department of Irrigation and Drainage Malaysia (D.I.D) in 2000. It is required by law for all engineers in Malaysia to design drainage works to fullfil the requirements of MSMA. 11 years after its first publication, DID has completely updated the first edition of MSMA (MSMA1) with the publishing of the second edition (MSMA2). There are a lot of alterations in the second edition include (taken from case studies done for Kuala Lumpur):





1. The design storm has increased by up to 126% for ten out of the 14 rainfall stations in Kuala Lumpur.





2. The design flow using the Rational Method has risen by up to 131% for commercial and city area.





3. The Site Storage Requirement for OSD for a factory lot in Kuala Lumpur has increased by up to 235%,





4. The volume of a detention pond has risen by up to 130%.





The hike in the magnitudes of the main design parameters as described above can be attributed to the differences between the first and the second editions of MSMA as follows:





1. Longer rainfall data covering 100 more storm stations in Peninsular Malaysia. This results in higher rainfall intensities for certain durations and ARI's.





2. West Malaysia is now grouped into five regions for the derivation of the storm temporal pattern, compared to previously where it was divided into east and west coast of the Peninsula. The differences in temporal patterns give rise to dissimilar hydrograph peaks and shapes.





3. The coefficient of runoff in the Rational Method is now set according to the types of landuse, and not affected by storm durations and intensities, and whether a catchment is urban/rural in condition. This resulted in differences in the estimated peak flow.





4. The Time-Area Method in MSMA2 is affected by the differences in the storm intensites, temporal patterns and the loss model used. For Kuala Lumpur it is noted that the storm intensities have increased and the storm temporal pattern is more peaky, thus resulting in a more peaky flow hydrograph.





5. The Site Storage Requirement (SSR) based on the Approximate Swinburne Method in MSMA2 is higher than that using the Swinburne Method in MSMA1. The second editon used the approximate method based on a set of approximation tables and this has resulted in an over estimation of the SSR's.





6. The volume of a detention pond has increased using MSMA2 compared to MSMA1 because of the increase in the storm intensities, temporal patterns and the choice of loss rate.





In view of the many differences in computational procedures between the first and second editions of MSMA, a tool is developed to help engineers to carry out the computations using both editions precisely and to allow comparison be made of their differences quickly. The tool is a stormwater design software created for MSMA- which is known as the MSMAware. The software is developed by Ir. Dr. Quek Keng Hong who is a professonal engineer in Malaysia. MSMAware also covers the East Malaysian state of Sarawak where more than a dozen storm stations in the state and their temporal patterns are included into the software.

















design rainfall Ph 6012 710 2620










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