CHAPTER 7: URBAN DRAINAGE MANAGEMENT

MSMA- Manual Saliran Mesra Alam Malaysia (Urban Stormwater Management Manual for Malaysia)

What is MSMA?

MSMA stands for the Manual Saliran Mesra Alam Malaysia (MSMA) or the Urban Stormwater Management Manual for Malaysia. It is the drainage design guideline published by the Jabatan Pengairan dan Saliran Malaysia (Department of Irrigation and Drainage Malaysia).

The document is officially enforced by the Malaysian Government in 2001. It is required by law in Malaysia for all to design drainage works to comply with the requirements of MSMA.

Who is Affected by MSMA ?

The groups affected by the implementation of MSMA include various professional groups e.g., civil engineers and engineers from other disciplines, architects, landscape architects, town planners, surveyors, quantity surveyors, environmental scientists and other professionals.

Besides the professional groups, the following groups are also affected: developers, contractors, government regulators like the Department of Irrigation and Drainage and the Public Works Department, Department of the Environment, local councils, students, land owners and other stakeholders.

Purpose of MSMA 

The main concept of MSMA is about controlling the runoff from a development site via a “control-at-source” approach as opposed to the “rapid-disposal” approach adopted earlier (DID, 1975).

Two major parameters to be controlled are the quantity and quality of discharges. These two components must be addressed at the source or the site of development. The quantity and quality of discharges going out from the site must not exceed those before the development.

To achieve the above, structural and hydraulic components such as site storage facilities, control structures and underground infiltration modules must be designed and installed within the site.

The ultimate objective is to ensure zero development impact in both quantity and quality of runoff from a development site.

History of MSMA

Before 2000, engineers in Malaysia applied the “Planning and Design Procedure No. 1” published by D.I.D. in 1975 (DID, 1975) for their drainage design. This document was around for about 25 years. This is a relatively simple document to use- with only 242 pages covering ten chapters.

But this has changed with the introduction of MSMA in 2000 (DID, 2000 abbreviated hereinafter as MSMA1). The new Manual is much more thorough in its coverage of subject matters compared to the old procedure. It contains 48 chapters spanning more than 1,100 pages. Its content reflects the latest advances in the field of stormwater quantity and quality management from around the world, with many major changes in approaches and procedures.

In 2011, the Department has published an updated version of the same manual, known as MSMA 2nd Edition (DID, 2011- abbreviated hereinafter as MSMA2). This document was launched by the Department in early 2012 and enforced on 1 July, 2012. The document is roughly half the thickness of the first edition. There are many changes from the first edition. 

Problems of Complying with MSMA Requirements

Many are finding it difficult to comply with the requirements of MSMA due to:

1. Many professionals find that the design procedures inside MSMA is difficult to understand and too complicated to apply. For example, in the first edition of MSMA, there were only 35 rainfall stations, but now in MSMA2 there are 135 rainfall stations in Peninsular Malaysia.

2. With the introduction of MSMA2, the magnitudes of many design parameters have increased, for example: storms, temporal patterns, peak discharges, hydrographs and changes in the storage volumes of On-Site Detention (OSD), detention basins and sediment basins. As a result, the drainage structures designed using MSMA2 are larger than MSMA1. This results in an increase in the cost of development and problems of undersized structures in areas designed using earlier drainage guidelines.

3. The problem of compliance is made more difficult as many regulators themselves are not well versed with the requirements of MSMA.

4. MSMA2 do not cover East Malaysia in many topics e.g., design storms, termporal patterns and OSD, thus making it difficult for East Malaysian states to adopt the guideline.

5. Many state DID’s have adopted different interpretation of the guideline, thus making it more difficult to comply.

Increase in Design Parameters

Design Storm increased by 126% in MSMA 2

Design Discharge by Rational Method up by 131%

Design Discharge by Time-Area Method up by 127%

Changes in temporal patterns

Increase in Storage Volumes

Detention basin storage up by 130% in MSMA 2

Sedimen basin volume up by 165% in MSMA 2

Site Storage Requirement for OSD increased by 190%

Combined Rainwater Harvesting and OSD MSMA 2

Problems Compounded by Changes in MSMA2

The problems of compliance with MSMA requirements is further compounded by the changes brought about by the introduction of MSMA2.

Based on our research, we found many changes between the first and second editions of  MSMA. Details of our research is presented in separate papers HERE. The key findings based on our case study for Kuala Lumpur are as follows:

1. The design storm has increased by up to 126% for 10 out of the 14 stations in Kuala Lumpur.

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

3. The peak discharge using the Time-Area Method has increased by 127%.

4. The Site Storage Requirement for OSD for a factory site has increased by 190%.

5. The volume of detention basin for a site has increased by up to 130%.

6. The volume of wet sediment basin has increased by 165%.

7. The requirement to provide rainwater harvesting according to the procedure outlined in MSMA(2011).

8. 

What is Sustainable urban drainage systems (SuDs)?

Sustainable urban drainage systems (SuDs) offer a natural approach to managing drainage.

When vegetation and permeable surfaces are replaced by concrete, paving or roofed structures, less surface water is absorbed into the ground and more is directed to the surface water drains.

Instead of channelling surface water through a network of pipes to a watercourse, sustainable systems slow and hold back the water, allowing natural processes to break down pollutants, and release it in a more controlled way.

This reduces the impact of new and existing building developments on the surface water drainage, which in turn minimises the chances of flash flooding in extreme weather conditions.

SuDS techniques include:

· green roofs (covered with vegetation)

· permeable surfaces

· infiltration trenches, filter drains and filter strips

· swales – shallow drainage channels

· detention basins, purpose-built ponds and wetlands

Benefits of SuDS:

· prevents water pollution

· slows down surface water run-off and reducing flood risk

· reduces the risk of sewer flooding during heavy rain

· recharges groundwater in areas prone to drought

· provides habitats for wildlife in urban areas

· creates green spaces in urban areas.

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What are Stormwater Detention Tanks: Differences to Water Retention Tanks

Water Retention Tanks

Water tanks are used to store water harvested from rooftops (rainwater) and/or hard surfaces on your property (stormwater). What makes them “retention” tanks, is that the water is retained to be used for one purpose or another, rather than simple allows to drain.

Investing in a water tank makes good sense, regardless of whether you’re in an urban or rural area. There are plenty of good reasons to install a water tank:

· You might live in an area where there are strict water restrictions.

· You might be in a Council area where you’re required to install a tank or there is no town water service.

· You might want to harvest rainwater to irrigate your garden.

· You wish to top up your swimming pool without depending upon mains water

· You’re sick of washing the car with a bucket.

· You don’t want to drink water with added chemicals

· You want to pay less for water you use around your home.

Stormwater Detention Tanks

New houses often have onsite detention facilities constructed as part of their home drainage system such. Such facilities normally include stormwater detention tanks. Detention means the water will be “detained” for a limited period. Stormwater detention tanks are intended to remain empty, except during periods of rainfall and for a short time thereafter.

Unlike normal rainwater tanks, the distinguishing feature of a stormwater detention tank is that is specially fitted with a valve to slowly release water over time. You have basically two options with a stormwater detention tank solution:

1. use two water tanks, one to harvest rainwater and the other for stormwater detention, or

2. use a specially made dual use water retention/detention system.

Reference

1. https://www.youtube.com/watch?v=O5tobzjoDdA
2. https://www.youtube.com/watch?v=2RjTuH3X-h8
3. https://www.youtube.com/watch?v=rtaZiZ1Q2l4
4. https://www.youtube.com/watch?v=k49pxVfxEN0
5. https://www.youtube.com/watch?v=ocueUHs5d9c