*The article appeared on the Malaysian Stormwater Organisation (MSO) Bulletin, STORMWATER 01/2024.

The FAQs were addressed by Dato’ Ir. Ahmad Fuad Embi, a member of the MSO Executive Committee and director at River Care Associates.

This dialogue is modeled after FAQs or Frequently Asked Questions, which is the same approach adopted by Google when you search for answers on any particular topic. In this case, the Malaysian Urban Stormwater Management Manual, better known as MSMA is already more than 20 years old  and this FAQ is really more about giving new generations of engineers involved in stormwater management the history behind it and what the new issues are that urgently need to be addressed. In later Bulletins, we will be posting more FAQs and elaborating more on the new issues.

MSMA was first published in 2000 by DID. A second, more compact edition was published in 2012, along with a series of twenty Malaysian Urban Stormwater Management Standards that represent some twenty-five selected chapters from the original voluminous 48 chapters. A third edition is being planned by DID to cover additional scope not in the original two editions.

1.Who  is the regulatory authority for stormwater management or drainage in urban areas?

Drainage in urban areas falls under the jurisdiction of the local authorities, as they have adequate legislation provided for it under the Street, Drainage, and Building Act (SDBA). By the 1990s, a growing number of PBTs were being upgraded to Bandaraya status, and their engineering divisions had sufficient technical capability to deal with specialized problems brought about by rapid urbanization. But the rest of the PBTs do not have such capabilities. Their small engineering divisions were hard-pressed to deal with everyday problems such as road, building, and infrastructure maintenance. These depend on DID to approve the drainage design for new developments.

2. Why was MSMA published by the DID and not by the Ministry of Local Government?

In 1971, the country was hit by the largest floods on record. KL was badly flooded for days. In 1972  the Cabinet assigned the function of flood mitigation to the DID, targeting the large-scale river flooding which affects every state in the country. Over the next 30 years, DID carried out river basin studies for all the large rivers in the country, besides implementing hundreds of flood mitigation projects through conventional hard engineering measures such as dams, diversions, channelization, and concrete-lining of river banks.

But then there began to emerge a growing problem everywhere: river flooding in urban areas. Booming areas like Damansara will flash flood every time with just normal conventional rainfall.

Conventional drainage by “rapid disposal” design as practiced by developers, was actually the main cause of such flash floods. Every new development creates higher discharge peaks at their outlets, which, when combined with adjacent developments, inevitably create flash floods in the receiving rivers.

DID was introduced to the more sustainable “detention and retention” approach at the first urban drainage symposium held in the country in 1994. To solve the river floods, DID decided that there would have to be new guidelines for urban drainage design for developers.

3. Why did DID not just adopt existing manuals from traditional English-speaking countries like Australia, the US or the UK?

Surprisingly, the MSMA manual is among the early manuals on urban stormwater management to be published. The UK manual for SuDS (Sustainable Drainage Systems) was only published in 2007, whereas the Australian Guidelines for Urban Stormwater Management were published in 2000.

In any case, we did not have any local experts who could write every aspect of the manual.  Most of the first MSMA manual was written by Australian and American consultants who pioneered the new approach to stormwater management, such as Dr. Larry Roesner.

4. Is the manual all about controlling floods and stormwater quantity?

Floods have always been the main issue as far as stormwater and rivers are concerned in Malaysia. Flood mitigation projects in the country runs into the hundreds of millions of Ringgit every year. And it seems to be rising decade on decade. It is estimated that as much as 8 billion ringgit has been spent on such projects for the Sg Klang catchment alone.

But the manual is about managing the three main aspects of stormwater:

Quantity control – to prevent and reduce flooding.

Quality control – to reduce pollutants from entering waterways, and

Erosion and sediment control, especially at construction sites.

5. How much success have we achieved on quantity control of stormwater in urban areas ?

In general, large new developments (above tens of hectares) all have permanent ponds to comply with the requirements for attenuation of discharge from the area. Most small developments, however, remain a problem as they usually do not have the space for such ponds, and many local consultants are not conversant with on-site detention (OSD) design, such as using car parks, roof-tops  or green areas for temporary storage. When you have an accumulation of such developments, of course, the same old problem reappears. This is when the DID will have to come in, building regional ponds.

Without the MSMA requirement, there would certainly have been more flash floods. And the government would certainly incur huge costs to acquire land to build more regional ponds.

6. What drawbacks or benefits have MSMA quantity control measures brought to new developments, especially for housing?

The large number of ponds that began to appear in housing developments created a new maintenance problem for local authorities, as they need to be desilted regularly and the greenery prevented from returning to the jungle. DID had to be given the budget and new function in many states. But the last two decades, however, a clear trend began to emerge among major housing developers in the country. They no longer have detention ponds that are a blight on the landscape of the area. Instead, these ponds became the central features of recreation and attraction for buying houses in that area, and are beautifully landscaped as shown in the photo below.

Unfortunately, such features are costly to maintain, and as soon as they are handed over to the local authorities, the ponds and greenery quickly deteriorate into marshlands.

On the bright side however, many such developments have found a way out by getting the residents to pay a monthly fee, usually tied in to their security fees, so that their precious landscaping can still be maintained by private contractors. This is not at all extraordinary, as people are more than willing to pay for their security and a higher standard of living. And people are savvy enough nowadays to know that property values in such serene areas will appreciate over the years.

7. What about the management of stormwater quality?

Awareness of erosion and sediment control has definitely reached all levels of the construction industry, although a lot remains to be done to ensure that ESCP plans are effective. Since sediment is the biggest polluter of waterways all over the world, it could be said to be addressing stormwater quality. However, MSMA requirements for stormwater quality have never been imposed on new developments.

8. Is that because stormwater quality requirements are too difficult for developers to comply with?

That may well be the case for MSMA 1 which was a formidable 48 chapters (in two 4-inch thick volumes), and it certainly takes time for local engineers to understand the subject matter and become familiar with cross-referencing throughout the chapters.

But this problem was well resolved by MSMA 2 which considerably simplified the design procedures. All that needs to be done is to refer to the design charts in Chapters 10 and 11 (samples below) to arrive at pond, swale or wetland sizes to comply with the requirements of Total Suspended Solids (TSS), Total Phosphorus(TP) and Total Nitrogen (TN).

9. Is it important that stormwater quality requirements be imposed on new developments?

It certainly is. Every new development is a new source of pollution for urban waterways, just as it is a new source of peak discharge. When combined in the hundreds in an urban area, they result in enormous problems that become too difficult to be resolved by remedial treatments on the river. They have to be tackled at the source. Authorities can then be tasked with systematically tackling pollution from old developments.

10. Are there new issues in stormwater quantity control in urban areas that need to be addressed?

The latest review of flood mitigation projects in the Sg Klang catchment has revealed three new areas that urgently need to be addressed:

i. Maintenance grass-cutting

The current practice of cutting grass in Green areas such as road and river reserves, roundabouts, parks and public areas down to soil level results in too thin a layer of vegetative cover. This leads to erosion of the topsoil and subsequent compaction from the pounding of our heavy tropical rains.

As a result, these Green areas are as impermeable as road surfaces and do not absorb rainfall, depriving the subcatchment of its much-needed detention properties.

ii. Urban Reforestation

The conventional method of urban landscaping with trees widely spaced 5 – 10 m apart only further aggravates the above problem of loss of rainfall permeability. Most such trees suffer from low water tables as rainfall is mostly lost to surface runoff.

What is urgently needed is ‘Urban Reforestation’ that packs trees, bushes and shrubs together in all Green areas as propagated by the Miyawaki method (see above photos). This will solve the problem of impermeability and soil loss, which are important components for stormwater storage I.e., quantity control. There are also other important benefits such as cooling and filtering the air and increasing biodiversity.

iii) Urban Heat Islands (UHI)

While there is considerable discussion on climate change(CC), there is very poor awareness of the phenomenon of UHI in Malaysia. There is even a budget provided to plant 100 million trees over 10 years to fulfill Malaysia’s commitment to the accord on CC.

But few seem to be aware of UHI. This is despite the fact that developed countries began tackling the problem more than 20 years ago. It is all the more exasperating when we take into account that they only have 4 to 5 months of summer in a year when this phenomena exerts its harmful effects, compared to our 12 months. It is already well established that UHI increases rainfall intensity and volume in the urban area concerned.

We need urgent countermeasures like Green Roofs and Green Infrastructure, which can cool down urban areas suffering from UHI. Singapore has some 80 strategies lined up to cool Singapore. We could do very well just to adopt a few of them.

At the very least, if a majority of the 100 million trees could be planted in urban areas, there could be significant difference to our UHI problem. Especially if they are planted in designated hotspots, which for the Klang Valley, have been identified through recent studies. At the same time, we still fulfill our CC commitments!