TAT 901 HYDROLOGY MASMA MANUAL SALIRAN MESRA ALAM

TAT 901 HYDROLOGY MASMA -MANUAL SALIRAN MESRA ALAM MALAYSIANur Liza Binti Rahim School of Environmental Engineering

MALAYSIA NATURE FRIENDLY DRAINAGE MANUAL • MASMA is a new urban stormwater design procedures and guidelines for Malaysia. It was introduced in year 2000 • It consists of about 1100 pages in 20 volumes and in 48 chapters • MASMA replaces PDPI (Planning Design Procedures) which was published in 1975, PDPI consists of only 242 pages in 10 chapters

Why MASMA is produced?

THE REASONS MASMA IS PRODUCED. . We know development caused flooding because of 2 main reasons: 1) Increase in impervious area result in less infiltration and more rainfall become surface runoff. Bigger volume of water to be drained. 2) Better drainage system result in higher efficiency and faster flow to downstream area, higher peak and lower time base.

CONT. . Development also caused siltation due to land clearing. The silt is deposited in the river channel thus reducing the capacity of river through increase in the level of river bed The previous action to solve the problem is through rapid disposal of water to the sea. Drain is enlarged and river is lined etc. however, with development, flooding still occur. There is also limitation in river enlargement and the process is very expensive In year 2000, a new manual called MASMA was introduced. It was then gazette by federal government and is now a law It is hoped that the new manual will help reduce the cost of river enlargement, river desiltation etc.

What is new in masma?

All development must ensure Qpeak after < Q peak before development It change the original concept of Rapid-Disposal to the concept of Control-At. Source. That mean new construction of the following is required: OSD(On site detention), Community Detention & Regional Detention It include emphasis on water quality and water quantity. More comprehensive coverage about subject matter which is surface runoff. More emphasis on computational method. Control at source concept includes structures such as detention pond, storage tank, sediment fence etc.

Tank under car park Use sand for lawn area Put pipes under car park OSD Must be designed to handle up to 5 yr flood Tank on top of roof Use car park as a tank/s storage area

Normally is a lake or big infiltration basin COMMUNITY DETENTION Must ensure post development peak < pre dev. peak Must be designed to handle 100 yr flood

REGIONAL FACILITIES Must have storage reservoir and can include infiltration basin Must designed to handle 100 year flood

An infiltration basin is a shallow depression created by excavation or berming that captures stormwater and stores it until it can infiltrate into the soil. Infiltration basins typically serve drainage areas from 2 to 20 ha (5 to 50 ac). In an ultra-urban setting it is strongly recommended that they be used in an off-line configuration because sediment accumulation and particulates from stormwater runoff can clog the system. The principal advantages of infiltration basins are that they help preserve the natural water balance of a site, they can serve large or small developments, and they can be integrated into a site's landscaping or open space.

Hydrologic and hydraulic modelling Computation of design storm Computation of peak discharge Among things that are included in MASMA are: Design of sediment basin Design of detention basin Reservoir routing

RATIONAL METHOD Q = Ci. A Q = discharge C = coefficient (between 0 and 1) i = rainfall intensity A = area of catchment Modified Rational Method Q = Cs. Ci. A Where, Cs = storage coefficient Rational method is only valid for catchment area of 0. 8 km 2 = 80 hectare. For bigger catchment area, we need to do computer modelling and need to use runoff routing computer model.