Anybody who has spent even a few days in Singapore has probably experienced those quick downpours that can pose dramatic flooding problems for the island city’s drainage system.
Singapore is located on the Equator, in a climate that brings in downpours in almost unpredictable ways, especially in the wet season from November to January when the northeast monsoon blows from the cool Northern Hemisphere towards the Equator. Many pedestrians carry umbrellas along the densely-packed streets to protect against the sun, but the umbrellas can also come in handy for a quick splash, often without much wind, like a cold gravity shower that might last 20 minutes.
I experienced several of those quick downpours on weeklong work visit one year while shooting smart city videos of MIT autonomous driving pilots and other tech innovations. Pilot vehicles on a geofenced track in one downtown park needed optical sensors sensitive enough to detect raindrops, which would work to suddenly slow down the AV in motion. The other reality I witnessed was how quickly a massive city with concrete sidewalks and asphalt streets would act like bathtub draining away the rain—quickly, swiftly and even potentially violently.
Over the years, the city has had to adapt in ways to cope, with the idea of sending wireless messages to thousands of residents and businesses in more flood-prone neighborhoods. There is already a network of more than 1,000 existing sensors and connections to 500 CCTV cameras and rain gauges and weather radar sensors around the country. My first encounter with this smart city water-level response occurred way back in 2015...
Even now in 2025, I was pleasantly surprised to see the flood monitoring effort continues apace in Singapore –thanks to water-level sensors innovations and the city-nation’s resolve. A new report in The Straits Times based in Singapore explains that more than 600 water level sensors are to be installed islandwide by 2028 to improve flood monitoring, according to the national water agency, the Public Utilities Board. Flood alerts are to be integrated on Google Maps.
By the end of 2028 an additional 650 water level sensors will be installed in drains and canals to help PUB hasten the quick response when a flash flood in a particular road is expected. Yellow vans will be deployed to divert traffic from flood lanes and officers will install portable flood barriers.
The striking thing about Singapore is how the nation has decided to deploy water level sensors on such a massive scale. I heard in Kansas City, Missouri, years ago of a similar water-level sensor system just being rolled out in select locations, but Singapore’s response is on another higher level. Even if a single sensor would cost $10 to $100, the installation and networking involved would surely raise the price. AI can be expected to have a role.
Singapore is truly dense—as in building after building with mostly flat geography. It’s easy to comprehend on a visit there to, say, downtown Manhattan. By the numbers, Singapore has more than 8,000 people per square kilometer, making it one of the densest cities in the world (compared to a global average of 141 people per square kilometer). It’s higher density than New York and London, but lower than Tokyo and Bangkok. Overall, the city-nation has more than 6 million residents on 294 square miles.
To be sure, Singapore often gets credit for great urban planning and part of it is about a strong commitment by planners (and support by elected leaders) who understand the value of using smart technology like sensors to gauge water levels. And not just a few water level sensors, but thousands of them. The continuing effort to install such sensors shows a planning effort that works over many years -- the essence of good planning.
Singapore has seen a greater problem with flooding over the past decade, according to various sources, partly due to an increase in rainfall due to climate change. There have been more frequent and severe flash floods, and the government has spent $1.5 billion (US) to improve its drainage infrastructure, according to CNA, formerly Channel News Asia.
With tidal flooding in seaboard cities a problem globally and flooding even along rivers from hurricanes (like Helene in 2024 hitting western North Carolina) and other storms, early warning systems from sensors and other smart technology will undoubtedly play a bigger role. In many cases, as expected, it will not be whether the technology exists, but whether there is sufficient public will to deploy it.