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Will Singapore’s MRTs be resilient to flash floods in the future?
Written by Vincent Wee and myself who have worked on flood resilience projects
ISMAIL WEILIANG
The Climatebender
VINCENT WEE
Co-author
Civil Engineer
Views are entirely ours
and not connected to any company
Flood disasters have almost tripled
Globally, major disasters have almost doubled in the last 20 years, comparing 2000-2019 (7,348) to 1980-1999 (4,212). Fuelled by climate change, flood disasters have increased the most, almost tripling. (UNDRR, 2020).
Flash floods in Singapore
Singapore is not spared from the brunt of climate change either. It has been affected by several events of exceptionally high rainfall, resulting in the Orchard Road flash floods in 2011, and more recently, the flash floods at Bukit Timah in April 2021. Flash floods of different magnitudes have occurred at many locations across the city state despite PUB’s expenditure of billions of dollars for drainage upgrading and revisions of flood management system and policies. These measures take time and money to implement, and are becoming increasingly difficult in our densely built-up environment.
Flood Resilience of MRTs
The rail transport system (Mass Rapid Transit - MRT) in Singapore forms the backbone of the public transport system, with plans to expand the network to 360km by 2030. Singapore currently has more than 130 MRT stations across 6 lines. A larger portion of these stations are underground, and would be susceptible to damages due to flooding. While rainfall durations might be relatively short, the impacts to the transport infrastructure can be longer lasting, especially if it concerns the loss of lives, damage to equipment and the inability to move people from one point to another.
Turning Risk into Opportunities
Existing design guidelines of entrances to underground MRTs work well in protecting it from flood waters. The minimum platform level is higher than the adjacent ground or road and an additional crest level is provided to stop water ingress.
With the increasing occurrence and unpredictability of future flood events with climate change, will Singapore’s MRTs be resilient to flash floods in the future? Short answer is yes with adaptable and scalable approaches delivered to improve our flood resilience. Planning for “no-flood” scenarios has become increasingly challenging and the “acceptable flood” scenario may be the most feasible where the underground transport network remains accessible to the public while keeping out the floodwaters. The underground transport network is more than just an underground facility and needs to allow people to move between transport nodes and reach their intended destinations, and not remain stuck during the flood event surrounded by a moat.
Potential Deliverables:
1) Design codes or guidelines can be revised to consider site factors and the functional and operational needs of the site.
2) Detailed studies can be conducted for flood prone areas on the surrounding topography, surface water flow paths and high risk flood areas, what severity and duration of floods are tolerable, what infrastructure is critical for operation rain or shine for the economy and society to remain functional, and other considerations deemed to be important to the people.
3) Flood risk mitigation measures can be mostly passive, and important infrastructure and facilities need to remain operational and accessible (while lower priority landuses might inevitably be sacrificed when flood events’ severity exceed what the mitigation measures are designed for practically).
We need to recognise that design codes usually prescribe the minimum requirements and the prescriptions might not always be sufficient to deliver a desirable outcome considering the interests of the general public. In a more uncertain world, design has to be more site and context specific and go beyond mere code compliance, for flood resilience to be achieved.
Authors:
Vincent Wee is a civil engineer at Arup Singapore. He holds a Bachelor of Environmental Engineering with a Civil Infrastructure Minor from National University of Singapore. He works on various rail infrastructure and maritime projects at advance engineering design, tender and construction stages, and masterplanning works related drainage, sewerage and utilities. He has developing interests in drainage and coastal protection works.
Ismail Weiliang is a climate resilience consultant with over half a decade of experience and specialises in flood risk advisory for Asia. His work involves advising governments and development banks on strategies to transform climate risks into resilience. He also founded “The Climatebender” a non-profit organisation that provides humanitarian relief to communities vulnerable to the climate crisis.
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