How River Floods Work
Since mid-September 2026 floods have reached 51 Thai provinces. This film explains the fundamentals behind every river flood, using the Chao Phraya basin that covers a third of Thailand: where monsoon rain comes from, why soaked soil sends water to the river, how four rivers become one funnel, why dams cannot both store and protect, why a sinking delta city fears the tide, and what a “100-year flood” really means. Soak the soil, send a storm down the basin, run a dam through a wet season and roll thirty years of odds yourself.
The funnel to the sea
Follow a raindrop from the mountains to the Gulf of Thailand.
The wind that brings the water
Half a year of rain, arriving from the ocean.
Soak in or run off
Every raindrop has two roads.
A full sponge
Why late-season rain does the most damage.
Higher and sooner
What a city does to a river.
Four rivers become one
A third of Thailand drains through Nakhon Sawan.
Two jobs, one bucket
A reservoir cannot be full and empty at once.
When both dams were full
How a drought set up a flood.
A city at sea level
The last link in the chain pushes back.
The ground goes down
Pumping water out of the ground lowered the city.
Every link failed at once
The flood that stopped factories around the world.
The hundred-year flood
A name that misleads almost everyone.
Monkey cheeks
Store the water, wait for the tide.
The funnel to the sea
Every link can be strengthened. None can be removed.
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