Tuesday, December 2, 2008

Flood Mitigation : What Go Wrong

If there is a single good policy that Dr Mahathir had produced over his 22 years in power, it would probably be the 2001 Urban Storm Water Management Manual or Manual Saliran Mesra Alam (MSMA) .

According to the interpretation of the Department of Irrigation and Drainage (DID), the MSMA incorporates the control-at-source approach in storm water management. This approach utilizes detention/retention to temporary store some of the water, infiltration to reduce the runoff and purification to improve the water quality reaching the river system. With the new approach, the impact of new development on the quality and quantity of the runoff can be minimised.

The goal of this Manual is to provide guidance to all regulators, planners and designers who are involved in storm water management. It identifies a new direction for storm water management in urban areas in Malaysia.

From 1st January 2001 onward all new development in Malaysia are mandated to comply with this new guideline that requires the application of Best Management Practices(BMPs) to control storm water from the aspect of quantity and quality runoff to achieve zero development impact contribution.

7 years later, the frequent occurrence of flash floods in Malaysia have not diminished, the situation continued to deteriorate to the extent where even Penang Hill was flooded.

The MSMA if implemented properly will help to eliminate piecemeal approach of past practice of construction projects by giving sufficient attention to the interrelationships between various elements of those projects or fully considering whether the projects will provide an integrated level of flood protection for the area.

One may tend to ask why the flood situation continued to deteriorate if there is such a good policy in place.

The fundament flaw is due to the strange interpretation of the DID over the design, concepts, criteria and regulatory requirements of MSMA. This cause uproar from the Real Estate and Housing Developers Association (Rehda) of KL over KL City Hall’s decision to make it mandatory for property developers to construct underground water tanks for rainwater storage at residential and commercial properties as part of the city’s flood alleviation plan.

The MSMA never endorse the idea of utilizing detention/retention facilities to temporary store some of the rain water. What the MSMA want to achieve is to ensure that developers, architects and builders are required to address storm water runoff issues in terms of providing analytical forecasts of the changes in overland flow, stream discharge and use of correct BMPs (Best Management Practices) related to particular projects. Best Management Practices (BMPs) are any procedure, protocol, structural device or site design that prevents or mitigates storm water runoff.

The on site detention facilities as recommended in the MSMA are meant to harvest rainwater for future usage. The on site detention facilities when integrate with community and regional detention facilities are part of the components for a water treatment solution. One good example is the NEWater project of Singapore. But here in KL, we didn’t see any indication that the DID is working with any relevant water authority in identifying the sites for building community or regional detention facilities nor any plan to build a water reclamation plant.

The DID never consider what will happen when all those underground water storage tanks start to flush out the water after rain subside. Flushing storm water back to the drainage system will eventually lead to flooding. You may now say that no flash floods have occurred any more as flooding will only occur after the delay of several hours. Technically speaking there will be no more flash floods except delayed floods.

The DID committed another mistake by limiting the enforcement of the regulatory requirement of MSMA to only new project or new development.

This explain why all the flood mitigation projects endorsed by the DID do not take into consideration the MSMA recommended flash flood solutions.

No person could reasonably interpret the provision of MSMA in the manner that the DID did which is inconsistent with the principles of adaptive management articulated in the MSMA.

This episode show that the failure of most mitigation plans so far is not a result of a lack of scientific technological knowledge, but rather of a fundamental flaw of how the authorities interpret the MSMA. When flood mitigation plan is applied in this way it is doomed to be ineffective in the best of cases and counter-productive in the worst.

With fools roaming like Maharaja in this Bolehland, you still believe that the so called experts can solve our flash floods problems?

The primary flood mitigation solution of the DID is river dredging. Each time a river has been straightened, dredged, bermed, and armored to mitigate flood damage without respect for the physical form and function of its channel and floodplain, adjustments were set in motion that, more often than not, led to further erosion.

For a straightened river in Malaysia’s geologic setting, it is only a matter of time before a flood drops a very large load of sediment at some point along its course. The wedge of sediment that builds in the channel during the recession of the flood may cause the river to avulse, or leave the channel, and head cut back through the landscape from the point where it returns to the channel further downstream. These events can erode river banks tens of feet and sometimes create whole new channels through adjacent lands.

We will then found ourselves in an unending and escalating cycle of spending billions of ringgits to maintain river channels, repair and rebuild flood damaged roads and bridges, and protect adjacent land uses from destruction by erosion or flooding, only to see these river management investments fail during the next flood or result in increased damage elsewhere.

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