The Reason King Yeongjo Ordered the Excavation of the Stream Bed

There was a project where the king summoned 200,000 people and had them excavate only the soil from the stream bed for two months. Soil washed down from the bare mountains filled the stream bed, so no matter how high they built the dikes, it was only a temporary fix. That's why they dug downwards instead of upwards. What's even more impressive is what came next. To prepare for the next excavation, they carved four characters into the bridge pillars to serve as a marker. When those characters were buried by soil, it meant it was time to dig again.