detention basin Phone 6012-710-2620
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Ph 6012-710-2620
Manual Saliran Mesra Alam Malaysia (MSMA), which is known in English as the Urban Stormwater Management Manual for Malaysia is the urban drainage design procedure first released 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 structures to comply with the requirements of MSMA. 11 years after its first publication, DID has completely amended the first edition of MSMA (MSMA1) with the publishing of the second edition (MSMA2). There are numerous changes in the second edition include (based on case studies completed for Kuala Lumpur):
1. The design rainfall has increased by up to 126% for 10 out of the 14 rainfall stations in Kuala Lumpur.
2. The design flow using the Rational Method has increased 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 storage volume of a detention basin has increased by up to 130%.
The hike in the magnitudes of the main design parameters as described above can be due to the changes between the first and the second editions of MSMA as follows:
1. Longer precipitation data covering 100 more rainfall stations in Peninsular Malaysia. This gives rise to in higher rainfall intensities for certain durations and Average Recurrence Intervals.
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 different hydrograph peaks and shapes.
3. The coefficient of runoff in the Rational Method is now determined according to the types of landuse, and not affected by rainfall durations and intensities, and whether a catchment is urban/rural in condition. This resulted in changes in the estimated peak flow.
4. The Time-Area Method in MSMA2 is affected by the changes in the rainfall intensites, temporal patterns and the loss model used. For Kuala Lumpur it is noted that the rainfall 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 the first edition. MSMA2 used the approximate method based on a set of approximation tables and this has resulted in an over estimation of the Site Storage Requirements.
6. The storage volume of a detention basin has increased using MSMA2 compared to the first edition because of the increase in the rainfall intensities, temporal patterns and the choice of loss rate.
In view of the many changes in computational methods between the first and second editions of MSMA, a tool is developed to help engineers to perform the computations using both editions precisely and to allow comparison be made of their changes speedily. The tool is a stormwater design software developed for MSMA- known as the MSMAware. The software is written 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 rainfall stations in the state and their temporal patterns are programmed into the software.
detention basin Phone 6012-710-2620
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