[ad_1]
SINGAPORE: Precipitation patterns in Singapore have been unusual in recent months. Stormy rains have persisted since August.
On August 11, heavy rains caused an accumulation of water, 50 mm deep, on Aljunied Road, and on August 14, flash floods occurred at the junction of Craig Road and Tanjong Pagar Road.
This past weekend, Bukit Timah channel pictures filled to the brim were widely shared on social media.
But, as much as people have been concerned, the chances of the water from the Bukit Timah canal spilling onto the road are almost non-existent.
READ: Climate change, floods and droughts: Here’s how Singapore could be affected
While the occasional flash floods haven’t caught us by surprise, many Singaporeans still remember those Orchard Road floods in 2010 and 2011 to date, when a month-long rain fell within a few hours.
On June 16, 2010, two heavy morning rains tore through the Stamford Canal, causing flooding of up to 300mm along Singapore’s trade belt. Older buildings like Lucky Plaza, Liat Towers and Delfi Orchard saw their basements flooded with water.
Insurance claims arising from business interruptions, property and vehicle damage were worth S $ 23 million.
And on December 23, 2011, 152mm of rain fell for three hours, partially submerging cars and low tents.
During the last two weeks, the rains have been quite heavy. The question arises whether Singapore is close to a once-in-a-hundred-year storm, like the one that drove millions from their homes in China this year. The answer is no.
A man rests outside a flooded tent after heavy rains caused flooding in Quzhou, Zhejiang province, China, June 30, 2020 (China Daily via REUTERS).
READ: Comment: China struggles with ‘once in a century’ floods that may be a new normal
In North Sumatra, where floods occur every monsoon season with some regularity, the Indonesian military and other disaster relief authorities face the ordeal of quickly evacuating residents.
Singapore, in a different geographic location, is highly unlikely to face the national flood emergencies that China or Indonesia regularly go through, stemming from coastal flooding and river overflow, but it will still face a complex set of challenges, especially in around flash floods inland.
READ: Comment: Kelantan’s epic struggle with big yellow floods every monsoon
BUILDING TO FACE FLASH FLOODS
Managing urban floods has always been a difficult and complex process. Coupled with the unpredictability, scope and magnitude of climate change, it is an even tougher task for a small city-state like Singapore.
Cities all over the world are familiar with this situation, as increasing urbanization with concrete structures and surfaces does not allow water to be absorbed quickly into the ground.
Drainage infrastructure can funnel rainwater from major downtown neighborhoods into rivers and other low-lying areas, but offsets should discourage reliance on engineering to solve flooding.
READ: Comment: Rising temperatures, fires and floods highlight the importance of understanding extreme weather events
Singapore, in particular, has severe land limitations, with unit costs of land among the highest in the world.
As the then Minister of Environment and Water Resources Masagos Zulkifli pointed out in February 2018, expanding the canals to remove flood water from the city indefinitely is not a viable solution, due to the high costs and the land it needs. .
There is also the possibility that future heavy rainfall events will exceed the design capacity of the improved drainage, especially due to climate change.
Part of the Bedok Canal flooding its banks, January 8, 2018 (Photo: Alex Lo)
Engineering can help cope with flooding, but it would require large investments and strong public support.
Tokyo, a city facing somewhat similar constraints, chose to build the world’s largest underground reservoir where floodwater from extreme rains and major typhoons can be diverted. The entire structure took 12 years to build and cost US $ 2 billion (S $ 2.72 billion).
However, the assets and lives saved only during the extreme flood of 2014 justified the enormous cost.
This flood protection system is likely to continue to serve Tokyo well. According to the Japan Meteorological Agency, storms are increasing due to global warming. Rainfall of more than two inches per hour increased by 30 percent over the past 30 years, and those of more than three inches per hour, 70 percent.
These events are now being observed in many parts of the world.
READ: Comment: What Singapore can do to prepare for the next flood
LISTEN: Get to the Big Picture of Climate Change Science
CITY PREPARED TO FACE A STORM TODAY
Since the 2010-2011 floods in the Orchard Road area, PUB, Singapore’s national water agency, has done remarkable work in flood management.
Over the past decade, it has improved drainage design standards, ensuring that they can handle higher rainfall intensities for much longer periods.
It has incorporated green infrastructure into its flood management strategy, such as the Aguas Activas, Hermosas y Limpias program to integrate canals and reservoirs into community spaces, and the construction of rooftop gardens.
It has also taken advantage of digital solutions, including the use of water sensors in drains and gutters to detect high water levels and new weather monitoring tools to forecast which street will see heavy rain, which is why PUB flood response teams can be implemented quickly.
File photo of the Stamford Bypass Canal.
Like Tokyo, Singapore has developed an underground repository, albeit on a much smaller scale. The 2 km long Stamford Diversion Canal was built in 2014 to divert stormwater into the Singapore River through underground tunnels.
Altogether, Stamford’s holding tank, an underwater storage facility the size of a football field, relieves drains on Holland Road during periods of heavy rain. These projects will prevent severe flooding in the Orchard Road area in the future.
Due to advanced PUB planning, Singapore’s flood prone areas have been reduced to less than 29 hectares in 2018, compared to around 79 hectares in 2008.
READ: Comment: Let Singapore’s green spaces grow wild
BUT THE FLOODS ARE MORE COMPLEX
As much as Singapore is better prepared to handle flash floods, can Singapore really say that we are ready for the next big one?
Calculating a 100-year flood with any degree of reliability is a difficult task. The flood hazard assessment requires information on its severity, frequency of occurrence, total area affected, and duration.
Each of these factors is difficult to predict. The combination of all significantly increases the degree of uncertainty.
This challenge is even more complex as long-term rainfall records, necessary for any flood planning, are not available before independence.
READ: Comment: How effectively can Singapore adapt to rising sea levels?
Intense thunderstorms are complex systems, especially in Singapore’s hot and humid environment. Air convections that influence thunderstorms are unpredictable and can change direction and frequency very quickly.
It is not uncommon to see strong thunderstorms in part of Singapore and not rain in areas only 5 to 8 km away. This irregularity complicates long-term flood management planning across the island.
Dark clouds over buildings in Singapore. (Photo: Howard Law)
There is also growing evidence from around the world that the challenge will be greater with climate change, as extreme rainfall increases.
A warm climate can worsen the situation and make it more complex, as a warmer atmosphere holds more moisture, intensifying sudden storms that cause flooding.
What used to be a full month’s rain can fall in a few hours, overwhelming the area’s drainage capacity. A 100-year storm centered on the Marine Basin, which has an area of 10,000 ha, means that 130 mm of rain can fall in one hour. This would fill some 5,190 Olympic swimming pools.
READ: Comment: Jakarta, World’s Fastest Sinking City Faces Greatest Flood Challenge
ADAPTATION AND MITIGATION TO THE REALITY OF FLOODS
With climate change, a real alternative for the future will be for Singaporeans to learn to live with small flash floods for short periods.
For example, in cities like Dhaka, what is considered a major flood in Singapore is locally called a waterlogging, a reference to rainwater overwhelming urban drainage systems.
Considered a perennial problem, people have learned to adapt their lives to these temporary inconveniences in the lowlands.
An ambulance is seen trapped in flood water near the Changi Fire Station on June 23 morning. (Photo: Nicholas Ong)
READ: Explainer: Why it is important to adapt to climate change
Globally, urban planners must strive to coordinate water and urban planning more effectively. Urbanization has led to increased stormwater runoff, so mitigation measures such as permeable pavements and mangroves should be considered, but are considered in only a handful of countries.
Additionally, Singapore’s new $ 5 billion Coastal and Flood Protection Fund helps prepare for a different type of flooding: coastal flooding caused by climate change. Aiming to protect the city-state from rising sea levels more effectively, it strengthens Singapore’s overall resistance to flooding from various water sources.
In the final analysis, no matter what action is taken, the chances of climate change-induced flooding occurring in Singapore, or anywhere else in the world, will never reach zero.
Therefore, the only effective solution is to plan for a future in which people will have to live with changing conditions.
Prof Asit K Biswas, is a Distinguished Visiting Professor at the University of Glasgow, UK. Dr. Cecilia Tortajada is Principal Investigator, Institute for Water Policy, Lee Kuan Yew School of Public Policy, National University of Singapore.
