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Stormwater Management -

By Ir. Richard Yong, Director, River Engineering Division;Dr. Md Nasir Md Noh, Senior Assistant Director, Department of Irrigation and Drainage

We have to live by theconsequences ofdevelopment for better or

for worse. Since 20 to 30 years agoMalaysia has been straddled by fastpace development projects. Withyearly precipitation between 2000mmand 3000mm, the degree of excessrunoff generated from developedareas apart from silts coming frombare land areas are merely too taxfulto deal with. Without notice, flashflood occurs in a few minutes leavingmost of the urban dwellers in awry.The aftermath is even worse since theleft over is not only rubbish but alsoa few inches of mud.

Scenes of garbage flowing intorivers and chemical discharge fromindustrial plants have been toocommon in the recent past. It all stemsfrom the uncontrolled discharge ofstormwater runoff into rivers.Imprudent urbanisation with narycare for the environment hascontributed to the decline of our riverwater quality. The time has come fora change in the way we manage ourstormwater runoff.

MSMA – Towards a New Paradigm

In 2001, a major move was takenin the course of Malaysian urbanstormwater management. In Januarythat year, the Cabinet officiallyapproved the Urban StormwaterManagement Manual for Malaysia(Manual Saliran Mesra Alam orMSMA) to steer drainagedevelopment.

MSMA is a technical guidedesigned to assist regulators, planners,

designers, developers, thepublic and otherstakeholders towardsachieving sustainablestormwater managementin Malaysia. Replacingthe Department ofIrrigation and Drainage’s30-year old UrbanDrainage Design Manual,MSMA could not havearrived at a better time.

While the old manualwas based on pureengineering solutions,MSMA provides a moreholistic solution thatemphasises, amongothers, institutional andlegal issues, strategicplanning, and largerenvironmental issues(stormwater quantity andquality controls), and

Pollution: Rampant Dumping of Rubbish intoConcrete Drain

Flash Flood: The Livelihood of Urban Dwellers

Manual SaliranMesra Alam

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aesthetic aspects. Seen as a major steptowards an integrated watercatchment management in thecountry, it illustrates the ever-growing awareness among policy anddecision-makers of the need toapproach stormwater relatedproblems in a holistic and integratedfashion.

What’s Ailing Our Rivers

In short, flooding and pollution.In forested areas, most of the rainfallinfiltrates into the soil or is trappedby the plants. A portion may reachthe groundwater table or flow torivers and streams. The fertile topsoillayers serve as gigantic sponges

MSMA’s fundamental principlesAccepted shared responsibility

DECISION-MAKING in sustainable stormwater management, based on the concept of sustainability, requires a healthycooperation, information exchange, communication and coordination between the various stakeholders.

Stakeholders are those who are affecting or affected by, the decision made with respect to the stormwater. Theyextend from individual consumers, agricultural and industrial sectors, public authorities, non-governmental organizationsand grassroots groups, to scientific communities and politicians.

Stormwater management recognises the important part each stakeholder plays in developing and implementingstormwater management strategies and action plans.

Integrated landuse planningLAND-USE activities are crucial functions of the quality and quantity of stormwater.For example, there are many instances where environmentally, socially and economically inappropriate or poorly planned

physical developments have been allowed resulting in flash flooding or worsening water quality.To achieve an integrated land-use planning, there is a need to ensure the existence of sufficient information and

understanding of the area in question. On top of that, the decision-making process towards such aim should be participatoryin nature and holistic in its methodology.

Water-sensitive urban designWATER-SENSITIVE urban design can be viewed as design which minimises the impacts of development on the total

water (or hydrologic) cycle and maximising the benefits of stormwater systems. Some of the key elements of water-sensitive urban design are:� Minimisation of changes to the hydrological characteristics of a catchment;� Minimisation of pollution entering the stormwater system and rehabilitation of the system whenever possible; and� Minimisation of local biodiversity deterioration

Multi-purpose stormwater infrastructureTHE current practice of adopting only conveyance-oriented approach for runoff control is not cost-effective, socially or

economically.Where such drainage facilities can fulfill other functions besides controlling water quantity, the results of the cost-

benefit analysis may turn to be much more appealing and desirable. Potential benefits of adopting a multi-use stormwaterfacility include:� a reduction in the capital cost of providing drainage infrastructure;� lower cost open space and recreational facilities compared with non-drainage corridor areas;� access to a low cost secondary water supply source;� increased real-estate market values enabling a greater investment return; and� increased potential of commercial exploitation of the recreational values of drainage corridors and waterways.

River Siltation: Costly to maintain and increases water treatment cost

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acting as natural temporary waterretention media. Flooding is less likelyto occur in such areas and pollutionis naturally mitigated.

With urbanisation, more concretestructures and thus less rainwaterinfiltrates into the ground. Roads,roofs, car parks, and paved surfacesallow a significant increase inrainwater runoff quantity. Stormwaterruns easily and rapidly into concretedrains; sometimes too rapid that riverscannot cope with the sudden deluge.

To make matters worse, many ofour rivers are also heavily silted dueto massive ground clearing in theupper water catchment. Siltationreduces the river carrying capacity.Combined with the rapid runoff, flashfloods occur or frequently mud floods.

Apart from flooding, a moreinsidious problem exists – waterpollution. It affects the aquaticbiodiversity, the recreational andaesthetic values of the river. Morecritically, the problem may result inthe decreased supply of raw water forour clean water supply system.

Rainfall also absorbscontaminants from the atmosphere.They accumulate on surfaces and flowinto the concrete drains only to beeasily and rapidly transported intorivers. This stormwater runoff

contains massive concentration ofcontaminated elements that degradethe water quality.

As if that was not enough,effluents from industrial activities,domestic sewage and rampantdumping of public solid wastes havecontributed to the worsening riverpollution problem. These pollutingactivities have greatly usurped theself-purification capacity of ourrivers. In normal circumstances, ariver is capable of purifying itself.However, massive discharge of wastehas killed many of them.

Why Pure Engineering SolutionsSometimes Fail

Traditionally, engineers tend tosolve flooding problems by the rapiddisposal method, a method by whichstormwater is discharged into thereceiving waters or rivers as quicklyas possible. This is achieved byconstructing concrete drains thatallow brisk removal of water into therivers.

Under natural state, rivers purifydirty water by means of physical,chemical and biological processes.With the introduction of concretedrains inside the water body, the selfpurification processes substantiallydiminish.

So in an ironic twist, instead ofproviding the solution, the rapiddisposal method has only exacerbatedthe flooding and pollution problemsin Kuala Lumpur and other cities.

Only recently, dispensing with thedominant idea of rapid disposal andpractice, a new breed of engineers andprofessionals figured out that perhapsconcrete drains are not the solutionat all.

In fact, the drains are the sourceof the problem. Equipped with betterunderstanding of the water cycle, theyhail the “back-to-nature” doctrine,something often overlooked in theconventional engineering discipline.It is the doctrine that best embodiesthe spirit of MSMA.

Detention Pond: Enhances property value, serves as water storage for food, pollutioncontrol and recreational

Grass Swale: Increases infiltration, safe and aesthetic

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Focal Points of MSMA

The stormwater managementpractice underlined by MSMAemphasises on structural and non-structural approaches. This is toensure that land developmentactivities that comprise property, roadand agriculture, among others, couldbe balanced with the future capacityof the river basin through sound waterand soil conservation techniques.

Water quantity and quality controlstrategies in MSMA are set againstthe overarching theme of sustainablestormwater management. MSMA’sfundamental principles are defined inthe side story.

These underlying ideas give birthto the various measures or strategiesunder which water quantity andquality issues are tackled. The mainobjectives of proper stormwatermanagement in Malaysia are to:� provide safety for the public,� minimise and control nuisance

flooding and provide for the safepassage of less frequent floodevents,

� stabilise the landform and controlerosion,

� protect property,� enhance the landscape,� optimise the land available for

development, and� minimise the environmental

impact of runoff on water quality

Water Quantity Control Strategies

A distinct character in the manualinvolves the storage-orientedapproach to control water quantity,that is, to reduce flooding orinundation problems as opposed tothe conveyance-oriented approach.

Techniques under this approachprovide for the temporary storage ofstormwater runoff at or near its pointof origin and then gradually releasedinto the river, or infiltration into thesurrounding soil. The former iscategorised as detention while thelatter as retention.

Besides minimising flood damageand disruption in the catchment, themethod offers a practical opportunity

to reuse stormwater runoff as secondclass water supply for irrigation anddomestic purposes such as carwashing and plant watering.

Detention facilities can becategorised into the following:� on-site storage: small-scale runoff

storages constructed onindividual, residential, commercialand industrial lots;

� community storage: facilitiesconstructed in public open spacesand sporting facilities;

� regional storage: large-scalecommunity facilities at the lowerend of catchments prior toreceiving waters.

Detention techniques include thefollowing:� small on-site tanks and above-

ground storage areas;� dry detention basins;� ponds and wetlands;� flood reservoirs; and� urban lakes.

Retention or infiltrationtechniques include:� dispersion trenches, pits, wells,

and “soakaways”;� directing roof runoff to pond areas

within lots for infiltration;� grassed swales;� pervious stormwater pipes;� porous pavements or parking lots;� trenches and basins; and� recharge wells.

Water Quality Control Strategies

The techniques to addressstormwater pollution into threemajor areas: housekeeping bestmanagement practices (BMPs),source control BMPs, andtreatment control BMPs. The lattertwo are relevant in MSMA.

Source Control BMPsThis category aims at keeping

stormwater runoff and pollutantsat their sources. Thus, it does notinvolve direct significant flowdownstream to the receivingwaters. Its application is a two-in-one technique to manage waterquantity and quality issues.

The techniques include perviousareas and buffer strips towardswhich runoff is directed,infiltration controls and porouspavements.

Treatment Control BMPsExamples of these strategies are:� lakes primarily as biological

treatment systems� water quality control ponds and

wetlands as physical andbiological treatment systems,upstream of lakes

� gross pollutant traps on inletsof lakes and water quali tycontrol ponds and wetlands tointercept trash, debris and thecoarser fractions of sediment.

Wetlands: Provides effective water purification - back to nature

Gross Pollutant Trap (GPT): Engineered pollutant removal system

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� “off-stream” sediment basins intoland development to intercept andchemically treat if necessaryrunoff prior to its discharge tostormwater systems and/orreceiving waters.

Sediment loading due to erosionfrom land development is one of theworst ecological impacts ofdevelopment. Techniques to controlthese do exist but they are not widelyused.

Thus, one of the most effectivecontrol measures facing this problemis to ensure that developers submitan Erosion and Sediment ControlPlan (ESCP) before earthworkscommence. This plan should beposted at the construction site andthe relevant authority shouldperiodically visit the site to inspectthe control measures and enforce theplan.

Conclusions

In a nutshell, MSMA attempts tomaintain or preserve our naturalwater resources on a sustainable basis.Stormwater management is adynamic discipline. MSMA is merelya guide based on proven models.Although the philosophy and theprinciples behind it remain fixed atleast for now, a stormwater manageris not restricted to stick to thoserecommended in the manual. In fact,it is encouraged and deemed apositive move towards theenhancement of stormwater andwater management in the country.

Stormwater management practicein Malaysia is based on the basicrequirements generated from thenational needs in paving the righttrack towards achieving sustainableriver basin initiatives. Developers,plantation owners and various

Government agencies involved in landclearing activities have to worktogether to ensure that excess runoffand silts are not affecting the adjacentareas as well as receiving water bodies.

For completed developmentprojects, property especially, themeasures proposed under MSMAenhance the value added of theseproperties and adjacent lands withoutjeopardising its market value. This hasbeen proven in all projects involvingMSMA.

In the long term, total success inthe whole process should originatefrom proactive actions with amplesupport and good coordinationbetween government agencies, non-Governmental organisations andevery stakeholder involved. One day,with relentless effort, we can behopeful that our vision of achieving“Clean, Living and Vibrant Rivers”will come true. BEM