What Is A Flash Flood?

Flash flood is a sudden, localized flood of great volume and short duration usually caused by heavy rain. In the case of Orchard Road, the area is surrounded by hills and is essentially a valley. Flash floods occur in this area partly because of the unique topography of Orchard road, but also due to increasing rainfall intensity brought about by changing weather patterns. A recent analysis by the Meteorological Service Singapore (2012) indicates that rainfall over Singapore has become more intense over the past 30 years.

What Is The Situation of Flash Flood Along Orchard Road?

Recently, the increase in flash floods occurrences has been a serious issue troubling Singapore. The floods came about due to the higher-than-average rainfall that aggregated over a short period of time. With a tropical rainforest climate, it is inevitable that Singapore experiences high rainfall, especially during the monsoon seasons which happen twice a year (Northeast monsoon season from December to early March; Southwest monsoon season from June to September). Hence, the government has put in place various flood control to deter the reoccurrence of such unfortunate flooding.

However, over the years, Orchard Road has been one of the hardest hit areas for flash flood occurrences. In June 2010, heavy rain of about 4 inches over two hours caused shopping malls like Lucky Plaza and Liat Towers to be severely flooded. The flooding caused some shopping malls’ car park basements to be submerged in water. Rescuers had to pull out about 70 passengers from cars and buses too. The Public Utilities Board (PUB) later revealed that the main reason for flooding was because of the storm that traveled along the Stamford canal catchment came in two intense bursts that generated runoff that overwhelmed the capacity of the Stamford canal, which then overflowed. Another reason for flooding was because the drainage system under Orchard Road, the Stamford Canal, was choked. It later installed five debris-trapping grates at Stamford Canal (Joanne Chan, 2010).

One year later in June 2011, a torrential downpour lasting several hours triggered another flash flood along Orchard Road. This time, Lucky Plaza and Liat Towers were not affected as flood barriers were activated at the start of the downpour. Yet, Tanglin Mall, St Regis and Traders Hotel, among others also situated along Orchard Road, were not spared from the flooding. Tanglin Mall and St Regis claimed they did not receive flood alerts from PUB, due to a technical glitch in the flood alert software. PUB also explained that flooding to the buildings was due to heavy rainfall directly into the basements. This resulted in the buildings’ internal drainage pumps not being able to cope with the huge amount of water.

More recently, sustained heavy downpour in December 2011 caused yet another flash flood along Orchard Road, affecting areas like the open area of Liat Towers, underpass between Lucky Plaza and Ngee Ann City, and the basement of Lucky Plaza. Liat Towers had reportedly activated its automatic flood barrier system, and as an added measure plastic barriers had been distributed too. Unfortunately, they failed to come in time to stop the floodwaters, as levels reached knee height and poured into the basement-level shops. Sandbags placed near the various buildings’ entrances proved not to be able to handle the 152.8mm of rain which fell on Orchard Road in three hours too. Additionally, despite having already raised a 1.4km stretch of Orchard Road from Orange Grove Road to Cairnhill Road in 2010, the PUB said the rain was “still too intense”, hence resulting in the serious flooding (Grace Chua and Feng Zengkun, 2011).


As Orchard Road is Singapore’s central shopping district, and also a major tourist attraction lined with high-end shopping malls, the fact that it is so frequently hit by severe flash floods is extremely unsettling. Obviously, the problem of flash flood occurrences along Orchard Road is dire. Luckily, the government has put in place flood control methods to salvage the situation. But with automatic and manual flood barrier systems failing to operate in time, and raised roads not having any effect in controlling flooding, these flood control measures have proved to be ineffective. More projects like the widening of drains and construction of a nearby Rochor Canal are also underway to help ease the flooding problem along Orchard Road. But how effective can these projects be? Will they successfully contain and control flash flood happenings?

The issue of flash floods is especially prominent to the densely populated and highly urbanised Singapore. Hence, we are keen to investigate the extent to which the government’s failure to control flash floods along Orchard Road could be due to its reactivity to the problem. We also hope to, through this project, look into other cities’ flood control methods and suggest recommendations to better control the situation of flash flood occurrences along Orchard Road.  


Flash floods have been a frequent incident taking place along Orchard Road.