Esther Ng Today Online 7 Oct 11;
SINGAPORE - Porous roads and using basements to store storm water are some ideas being bounced about by an expert panel formed to improve Singapore's flood protection measures.
Other recommendations include combining predictions on rainfall intensity and trajectory with rain gauges and water level sensors installed in canals, which will result in a real-time flood alert system that would "allow the agencies to give a better lead time to the community", said Professor Chan Eng Soon, who chairs the panel. He was giving an update yesterday on the panel's work since it was formed in July.
Among its preliminary recommendations, the panel said: "PUB should move to a process of new generation drainage systems models that can adequately replicate systems performance, evaluate potential interventions and provide flood-risk mapping."
Meeting for five days from Sept 26 to 30, the panel also proposed holistic flood control measures such as tapping and reusing storm water to flush toilets.
"The question is not just on collection, but the infrastructure that goes with it," Prof Chan said. For example, households will need separate pipes connected to a storm water tank and that would incur cost.
As for porous roads, there is the question of cost of building infrastructure of pipelines.
"In the past, perhaps there was more emphasis on conveyance, (but now), the solution is not just a canal, but a system of canals and ponds and other things you can put in place to manage storm water," Prof Chan said, adding that the PUB was familiar with these various approaches.
Asked what constraints national water agency PUB faced in implementing these ideas, Prof Chan, who is also the Dean of the Faculty of Engineering at the National University of Singapore, pointed that PUB had done much to reduce flooding "drastically" with the Bukit Timah "bypasses" and that the recent floods only happened in the last two years. "So all along (the measures) seemed to work very well," he said.
In addition, the PUB has proposed an increase in design standards through the revised Code of Practice on Surface Water Drainage, and in terms of storm drainage, Singapore compares well to other metropolitan cities, he added.
Going forward, the panel recommends that the agencies take a "risk-based approach" of quantifying of the options and the cost of infrastructure, guided by potential implications of climate change and the use of comprehensive modeling and scenario analysis.
The panel will conclude its review and submit a final report in January.
Better storm data needed to prevent floods
Feng Zengkun Straits Times 7 Oct 11;
MAKING Singapore less flood-prone is not simply a matter of building bigger canals.
The Government needs to study weather patterns and collect better information about rain - before it falls, and even as it is falling.
It should then use this data to design canals that can better handle the occurrence of freak storms.
These are among the first recommendations made by a panel of local and international experts set up in June to look into recent floods.
'It's no longer enough to just think about canals and drains in terms of how much water they can hold,' said the chairman of the panel, Professor Chan Eng Soon, at a press conference to announce its findings yesterday.
'We need data so we can use computer models to test different types of storm patterns.'
The collection of better data would involve the installation of equipment such as rainfall radar, flow meters, rain gauges and water sensors, added Prof Chan, who is the dean of the engineering faculty at the National University of Singapore.
This is necessary because rainfall patterns seem to have changed. The panel said there is evidence that the maximum intensities have increased over the past 30 years.
Such data would let engineers decide whether future canals and drains can handle freak storm patterns such as the rain that flooded Orchard Road in June last year, Prof Chan said.
That storm had come in two short but intense bursts, overwhelming the Stamford Canal's ability to cope with the volume of water.
'Conventional design approach and standards are not sufficient to secure an adequate drainage system for the future,' concluded the panel.
It noted that national water agency PUB had already started on improving the system and that measures under way to address the Bukit Timah floods 'appear to be sound', but added that more can be done.
In the long run, the agency should also expand its programme to add ponds and vegetation at canals to slow and retain more rainwater, said Prof Chan.
He added the panel is also considering other long-term solutions such as porous roads which can soak up rainwater.
The panel, made up of 12 local and foreign experts, was set up by the Ministry of the Environment and Water Resources after intense rain caused a flood at Orchard Road for the second year in a row.
Members include Professor Toshio Koike from the Department of Civil Engineering, University of Tokyo, and Mr Kan Yim-fai, chief engineer of the Land Drainage Division at Hong Kong's Drainage Services Department.
The panel met last week and will convene again in January next year to finalise its report, which will be submitted to the ministry.
Prof Chan declined to comment on the effect of increased urbanisation in Orchard Road, which was also fingered for the floods there.
'We are still looking into that,' he said.
Mr Steven Goh, executive director of the Orchard Road Business Association, hopes the panel will consult building owners and businesses along Orchard Road before submitting its final report.
Among the association's ideas is a 'green lung' behind Ngee Ann City which can help absorb rainwater.
'We are the people on the ground, so we will be able to contribute valuable information,' he said.
Not Marina Barrage's fault, say experts
Straits Times 7 Oct 11;
THE Marina Barrage was not responsible for the floods in Orchard Road. That was the conclusion of the panel of experts set up in June to tackle the flood problem.
The barrage was built in 2008 to reduce flash floods in low-lying regions of Singapore.
But all of the country's major floods have happened after its construction, leading many to blame it. They said the barrage was slowing down the flow of rainwater into the open sea.
The panel's chair, Professor Chan Eng Soon, said it used a computer program to recreate the storm conditions during the Orchard Road floods but removed the barrage from the picture. It found that the floods would still have occurred even without the barrage.
Flood experts urge PUB to relook drainage system
Vimita Mohandas Channel NewsAsia 6 Oct 11;
SINGAPORE: An expert panel looking at flood protection measures has called on national water agency PUB, to look at a new drainage system for Singapore.
The panel, headed by Professor Chan Eng Soon, Dean of the Faculty of Engineering at the National University of Singapore, said the model must adequately replicate systems performance, evaluate potential interventions and provide flood-risk mapping.
The panel also urge PUB to increase monitoring of systems performance, such as collecting more real-time information on rainfall.
Professor Chan said: "It's not just modelling. At the frontiers, it's a combination of sensing and modelling. We thought that coupling the two, monitoring and sensing, would allow PUB to do a lot more and moving also towards a real-time system.
"If you look at the integration of say weather radar, rain gauges, water level metres and the flow metres in canals, you can combine all this together with the models and then turn them to predictive systems."
The panel also noted that canals and drains were no longer enough to handle rainfall here.
It said ponds and porous roads could be added to the drainage system.
Porous roads will allow rainwater to seep through the roads, as opposed to flooding the sides.
Another suggestion is to collect storm water at basements of buildings, which could then be reused for various purposes, such as flushing toilets.
The panel added that the current conventional design standards are not sufficient to secure an adequate drainage system for the future and this could be attributed to the rising maximum rainfall intensities in Singapore in the past 30 years.
The panel also ruled out Marina Barrage as the cause of massive floods in the last two years which hit parts of Singapore's shopping belt, Orchard Road.
The panel will submit a final report in January 2012.
- CNA/fa
Expert panel: Singapore drains can't cope with more rainfall
Reico Wong my paper AsiaOne 7 Oct 11;
The current design and network system of canals and drains in Singapore are no longer adequate to handle the higher rainfall levels here, said the Expert Panel on Enhancing Flood Protection yesterday.
So, more "robust" ways are needed to slow down the flow of storm water and increase its drainage, said the panel's chairman, Professor Chan Eng Soon.
Possible ways include building porous roads to soak up storm water and adding greenery at the top of buildings to help capture and retain rain.
Singapore's drainage infrastructure could also be enhanced, such that rainwater in a particular area is drained out through a network of canals, instead of just one, Prof Chan said.
He revealed that those were some of the preli- minary suggestions raised at a meeting of the expert panel at the end of last month. It is studying the feasibility of the suggestions.
The panel, comprising 12 Singapore and foreign experts, was set up in June by the Ministry of the Environment and Water Resources, after repeated serious flooding incidents across the country in the last two years.
The panel is expected to conclude its review of Singapore's flood-protection measures and submit a final report in January.
At a press conference held at the National University of Singapore, Prof Chan noted that Singapore's storm water-drainage system compares well to those of other metropolitan cities, adding that all drainage systems have a finite capacity.
"Conventional design approach and standards are not sufficient to secure an adequate drainage system for the future, especially given global climate changes," he said.
"PUB needs to consider a wider range of measures that mitigates the effects of urbanisation. I think it could look at solutions in a more holistic way."
Such an approach would not just focus on storm- water drainage - which is what PUB, the national water agency, has done in the past - but would also consider other issues like storing and retaining rainwater.
The design of a new drainage system should also take into account other unpredictable risks, such as the possibility that rainfall could be even heavier in the future. Prof Chan noted that the system has to factor in the drainage standards the country wants to achieve, as well.
Singapore ultimately needs to move to a better, "new-generation" drainage model, with enhanced systems-performance monitoring and better capabi- lities to map out areas prone to flooding, he said.
This will provide more accurate operational infor- mation to water agencies, so that they can warn the public earlier about impending floods.
Another recommendation by the panel was for the PUB to find better ways to use storm water to meet Singapore's water needs.
For instance, rainwater could be sent through separate pipes to homes and be used for flushing toilets and gardening, pointed out Prof Chan.
He added that the panel has ruled out the Marina Barrage as a cause of the recent floods here, after conducting relevant tests. A technical study found that the floods would have occurred, even without the existence of the barrage, he explained.
MEDIA STATEMENT BY PROF CHAN ENG SOON, CHAIRMAN, EXPERT PANEL ON DRAINAGE DESIGN AND FLOOD PROTECTION MEASURES
The Expert Panel on Drainage Design and Flood Protection Measures convened its second meeting from 26 to 30 September 2011.
MEWR undated;
2 The Panel was briefed on national water agency, PUB’s drainage planning and design process and the operations of Marina Barrage. The Panel was also briefed by the Meteorological Service Singapore on historical rainfall trends. A site visit was also made to the ABC Waters project at Kallang River-Bishan Park. At an earlier session, the expert panel also visit the Marina Barrage, the Stamford and Bukit Timah Catchments.
3 The Panel had a good discussion and arrived at some preliminary findings and recommendations on PUB’s drainage design and flood protection measures. The Panel will further deliberate on these recommendations before submitting a final report to the Ministry of the Environment and Water Resources.
4 In essence, the Expert Panel recognises that any drainage system, whatever the standards, has a finite capacity. From time to time, intense rainfall will overwhelm the system, and there will be residual risks that need to be managed. This applies to all cities in the world as it is part of a natural process.
5 The Expert Panel’s preliminary findings are:
a) Much good work has been done by PUB. In terms of storm drainage, Singapore compares well to other metropolitan cities.
b) There is evidence (from Meteorological Service Singapore’s analysis of a study of rainfall intensity) that the maximum rainfall intensities in Singapore have increased in the recent past 30 years (from 1980 to 2010).
c) Based on the evidence provided (from modelling simulations by PUB), Marina Barrage was not the cause of the flood incidents in 2010 and 2011.
d) Measures being undertaken to address the Bukit Timah floods appear to be sound and should alleviate the flooding problem in the area.
[These measures include the widening and deepening of Bukit Timah Canal at the stretch from Jalan Kampong Chantek to Maple Ave, and the upgrading of the Bukit Timah First Diversion Canal from Maple Ave to Clementi Road]
e) Conventional design approach and standards are not sufficient to secure an adequate drainage system for the future. The Panel acknowledges that PUB has recognised this and has proposed an increase in design standards through the revised Code of Practice (COP) on Surface Water Drainage.
6 The Panel also proposes the following preliminary recommendations:
a) PUB should move to a process of new generation drainage systems models that can adequately replicate systems performance, evaluate potential interventions and provide flood-risk mapping.
b) There should be increased monitoring of systems performance (rainfall radar, flow meters, rain gauges and water level sensors) to provide better operational information, help validate models and facilitate early warning.
c) PUB to consider a wider range of measures that mitigates the effects of urbanisation (e.g. compensatory storage for new developments and redevelopments). A wider range of measures may be more appropriate for the management of flood risk in the future.
d) PUB to consider added benefits of drainage in the context of the wider future needs of Singapore (e.g. storm water reuse, improved water quality, biodiversity, amenities)
e) PUB to consider further revisions to the current Code of Practice on Surface Water Drainage based on:-
Systems approach
Use of Risk-based approach, guided by trends in rainfall intensities and potential implications of climate change and standards
Use of comprehensive modelling and scenario analysis
The Expert Panel will conclude its review and submit a final report in January 2012.
