With sinkholes recently making the headlines, it’s easy to worry that one will form under you while you’re walking on pavements.
On 23 Aug, an eight-metre-deep sinkhole formed in Kuala Lumpur, “swallowing” a woman. Despite rescue and recovery efforts, the woman has yet to be found.
Source: Dewan Bandaraya Kuala Lumpur on Facebook
Since then, other sinkholes have been reported around the world.
In Seoul, South Korea, a sinkhole trapped an SUV and its two elderly passengers.
Meanwhile, another case in Taiwan led to two damaged two motorcycles.
Source: Yonhap via The Korea Herald
Singapore has also had its fair share of sinkholes, with the most recent one occurring in 2022. Fortunately, these sinkholes have only resulted in minor injuries.
But is Singapore at risk of more sinkholes? And what are some of the signs to watch out for if you’re worried?
While you might be tempted to call any large hole that appears in the ground a sinkhole, the term actually refers to “a natural surface depression caused by dissolution of soluble rocks at depth”, according to the British Geological Survey.
Simply put, the process starts when rocks and soil underneath the surface have been washed away by water.
It then leaves an underground chasm that causes the surface to collapse or sink in.
Water is often the primary cause of sinkholes, according to ABC News.
As such, leaking water pipes, as well as intense rainstorms or floods can trigger sinkholes to form.
The former is trickier to anticipate as the initial damage occurs underground — with little to no indication of a problem on the surface.
Depending on the type of soil, the process of erosion can take days or years.
The YouTube channel Practical Engineering demonstrates how water moving underground can eventually cause a hole to form above, even if there are few signs of a looming catastrophe.
Sinkholes have appeared in Singapore in the past, with the Straits Times (ST) reporting a total of five sinkholes in 2013.
The first one appeared at Keppel Road on 30 January 2013 and was believed to have been caused by an underground pipe leak.
Source: The Online Citizen
A car had plunged into the hole when its driver mistook it for a puddle.
The second sinkhole of 2013 appeared a few months later on 5 March at Clementi Road.
A motorcyclist who had fallen into the three-metre-deep chasm suffered minor injuries.
Source: The Online Citizen
However, the cause of this sinkhole is unclear because there were no nearby construction or pipe leaks.
Three days after the sinkhole at Clementi Road was filled in, it reappeared.
No one was injured, but geotechnical engineers suggested that the recurrence was due to acidic water from underground streams dissolving the rocks underneath.
On 16 March 2013, a hole as wide as a lane of traffic appeared in Woodlands.
Source: SG Car Mart
As a result, both sides of the road were blocked while repairs were conducted.
Experts determined the cause to be the ongoing construction for the Downtown Line 2 nearby.
The Land Transport Authority (LTA) said that construction had ruptured a water pipe and the leak caused the sinkhole to form.
The fifth sinkhole of 2013 occurred towards the end of the year on 23 December.
Another hole as wide as a lane of traffic appeared on Commonwealth Avenue West.
The road had caved in while workers were laying down underground electrical cables. The cause appeared to be heavy rain. No one was injured.
Since then, reports of sinkholes in Singapore have been rare.
However, in late April 2015, a tipper truck sank into a sinkhole on Upper Changi Road East where it was stuck for over two hours.
Source: TODAY
No one was injured in the incident. The sinkhole was attributed to nearby construction for Downtown Line 3.
The final reported sinkhole in Singapore was on 15 Nov 2022. It was the result of tunneling work on Farrer Road.
The tunnel boring machine was excavating a tunnel for PUB’s Deep Tunnel Sewerage System Phase 2 at the time of the incident.
According to The Straits Times (ST), the machine was undergoing maintenance when the “ground in front of the tunnel face destabilised”.
A sinkhole then formed on a slip road leading from Holland Road to Farrer Road.
Source: PUB, Singapore’s National Water Agency on Facebook
The affected sections of the roads were only fully reopened in March 2023.
However, much like previous cases, no one was injured.
Mr David Ng from Singapore’s Institution of Engineers said in an interview with Channel NewsAsia (CNA) that the chances of someone falling into a sinkhole in Singapore are “very remote”.
He added that sinkholes in Singapore are mainly caused by construction, particularly tunneling for sewage and MRT lines.
But because Singapore’s natural soil is “not particularly susceptible”, sinkholes are rare here.
According to the American Geosciences Institute, sinkholes are most likely to occur in places where water can dissolve bedrock.
This is especially the case for easily eroded “soft rocks” such as limestone.
In the United States, Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania are the areas most prone to sinkholes.
The National Geographic Society notes that the land surrounding the Dead Sea in the Middle East is also prone to sinkholes.
According to ABC Australia, there are a few signs that might help you spot a sinkhole before it collapses.
These include fresh cracks in the foundation of buildings, interior walls, and the ground outside.
Sturdy trees suddenly tilting or falling may also indicate that their roots have been dislodged.
That said, experts have assured that the risk of people getting injured by a sinkhole is minimal.
So long as the proper precautions are put in place for construction activity that may result in sinkholes, the public should be safe.
Also read: KL sinkhole victim’s family conducts religious ceremony at scene before leaving for India
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Featured image adapted from The Online Citizen and SG Car Mart.
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