Most people think of Japan as a land of earthquakes and volcanoes — but Derek Muller argues the nation faces an equally formidable threat from water. The rainfall simulator at NIED (National Research Institute for Earth Science and Disaster Prevention) in Japan isn't just an impressive engineering feat; it's becoming essential as extreme weather events intensify.
The Amazon vs. Yakushima
Muller makes a striking comparison early in the piece: "yakushima Island near the southern part of Japan is one of the wettest places on Earth receiving up to 10 m of rain every year for comparison the Amazon rainforest gets only about 3 m of rain per year that's three times less than yakashima Island." This framing effectively conveys just how extreme Japan's rainfall truly is — and why studying it matters. The Amazon, often imagined as a tropical deluge, receives far less precipitation than this single Japanese island.
The facility itself can simulate rainfall intensity ranging from 15mm per hour to 300mm per hour. Muller notes that "the most rainfall ever measured in 1 hour occurred on the 22nd of June 1947 when 305 mm of rain fell on the town of Holt Missouri" — a figure that establishes the benchmark for what the simulator can recreate.
Why Raindrops Don't Look Like Cartoon Drops
Muller offers an accessible explanation of physics: "there are two forces that act on a raindrop gravity and air resistance and the larger raindrops have a higher weight to surface area ratio and so they have a higher terminal velocity so they will be falling faster." He then addresses a common misconception with direct language: "a raindrop that's 1 mm in diameter Falls at only about 2 m/s while a 3mm raindrop Falls at 6 m/s."
The most counterintuitive insight comes when Muller corrects our intuitions: "it's a misnomer out there that water makes it the material slipperier so it rains and it soaks into the ground and it makes it slipperier that's not true water is actually an anti-lubricant for many materials including quartz." This is where the piece becomes genuinely useful — showing that rain doesn't lubricate soil, but instead fills pores with water, increasing pressure that breaks apart slopes. The physics here is counterintuitive: we assume water acts as a lubricant when it actually acts as a destabilizing force by reducing friction between soil grains.
The Scale of Japan's Flooding Problem
Muller presents devastating statistics: "in July 2018 there were floods all over the country due to the rainfall from typhoon praon some regions of the country received nearly 2 MERS of rain in just 10 days and the resulting floods were enough that more than 8 million people had to be evacuated from their homes over 200 people died and the damage to property from the flooding was more than 1 trillion yen."
He also notes Tokyo's sophisticated infrastructure: "Tokyo the capital city of Japan is very vulnerable to flooding there are more than a 100 Rivers criss-crossing the city of nearly 40 million people to prevent the rivers from overflowing there are pipes and tunnels under the city leading to an enormous water storage tank." The underground system for October 2019's Typhoon Hagab "diverted 12 million cubic met of water and prevented an estimated 1.7 billion in damage."
Landslides: A More Complex Problem
The piece emphasizes that landslides are harder to predict than flooding: "the complexity of the physics of landslides is why the work done at the large scale rainfall simulator is so important" because "there's so many factors that affect if a landslide will occur how large it could be how fast it will move and how much damage it will do not just the slope angle or the amount of new rain but the type of soil the minerals present and the vegetation growing on top of the slope."
Muller points to an alarming trend: "in the forests of British Columbia humans are really good at causing landslides and we're shaping the land a heck of a lot more quickly than geological processes do" — with deforestation creating a ten-fold increase in landslide events. He cites a Seattle study suggesting "more than 85% had at least partial human trigger" for slides.
Climate Change: The Accelerating Threat
The piece's most urgent argument arrives near the end: "as the world heats up due to Humanity's addiction to fossil fuels extreme weather events are becoming more common compared to 30 years ago the number of rain events in Japan with an intensity of 50 mmph have become 40% more common rainfall at Double that intensity has become 70% more common."
Climate change will increase the rate of flooding and the occurrence of landslides in the future which is why the work done at the world's largest rainfall simulator is becoming more and more important.
Counterpoints
Critics might note that while Muller effectively frames Japan's infrastructure as impressive, he doesn't fully explore whether similar facilities exist elsewhere — or what international collaboration on flood and landslide research looks like. The piece also leans heavily into the sponsor segment (NordVPN) which disrupts narrative flow somewhat. Additionally, the claim about "human trigger" for landslides in Seattle could use more rigorous sourcing.
Bottom Line
This piece's strongest contribution is making the invisible physics of rainfall visible — showing how water fills soil pores and breaks apart slopes rather than lubricating them. The statistics on Japan's evacuation efforts and damage costs are genuinely alarming, and the climate change data adds urgent context. The biggest vulnerability is that Muller treats infrastructure as the solution without fully interrogating whether engineering alone can keep pace with accelerating extreme weather. The piece makes a compelling case for why rainfall simulators matter — but it leaves an open question about whether prevention-focused infrastructure can actually outrun the worsening storms ahead.