신비한사전

There's an island that was completely blown up with explosives in 1968 to build Yeouido. It's Bamseom Island in the Han River, and surprisingly, it's now more than four times larger than before it disappeared. This happened because the spot where it was bombed was precisely where the water current slowed down, causing the sand carried by the Han River to continuously accumulate. They could have excavated it again, but in the meantime, marsh plants started to take root and migratory birds began to land. So, what the Seoul Metropolitan Government chose was not to manage it further, but to completely let go. By blocking access and only removing trash, this island is now home to 138 species of plants and 50 species of birds. It's as if the river redrew the island that humans had erased.

Did you know that the Yeouido where the National Assembly and 63 Building now stand was a sandy plain 60 years ago that would completely become the riverbed when it rained? To reclaim the land, a dike had to be built, but since the ground was all sand, the water would erode it from below unless it was encased in stones. There was neither the money to bring in so many stones from outside nor the time left before the monsoon season. The solution the Seoul Metropolitan Government came up with was to blow up Bamseom, which was blocking the waterway. This was a strategy to both widen the river and obtain rocks for the dike, solving two problems at once. Thus, a 16m high, 7.6km circumference dike was built in 110 days, and what's even more surprising is that the southern샛강 (saetgang, tributary stream) was intentionally left as an extra waterway to receive floodwaters.

Did you know there are 92 million tons of trash buried right under the silver grass fields of Sangam-dong's Haneul Park in Seoul? The trash discarded by Seoul for 15 years solidified into two mountains, each 98m high, and there was absolutely no way to remove it. When they covered it with soil, methane gas built up and the mountains started catching fire in various places. So, what Seoul City chose wasn't to get rid of it, but to contain it and extract from it. They built containment walls around it and installed 106 gas pipes to extract methane, and that gas is now being used to heat the World Cup Stadium. They even planted silver grass because its shallow roots wouldn't pierce the waterproof layer, so even the landscape was calculated.

The stone courtyard in front of Gyeongbokgung Palace's Geunjeongjeon Hall doesn't easily flood, even during heavy downpours. This is despite the water flowing directly from Baegaksan Mountain behind the palace. If they built walls to contain it, the water would pool and turn the entire palace into a basin, and if they tried to channel it all out in one stream, the current would erode the foundation stones. So, Joseon chose to divide the water into smaller streams and let it flow slowly. They created separate drainage systems for each section, where reservoirs called 'jipsujeong' would settle dirt and fallen leaves, allowing only the clear water to pass into underground stone channels. What's most surprising is that they didn't excavate the land but instead utilized the original slope to guide the water's path.

Water springs up daily beneath Seoul's subway lines. Over 180,000 tons of groundwater flow out across Seoul each day, and about seven-tenths of that comes from the subway system. If they don't pump it out, the tracks flood, but if they keep pumping, the soil between particles empties, causing the ground to subside – a true dilemma. What's even more regrettable is that this water, which is generally quite clean, was being dumped into the sewer system, incurring costs. According to Seoul City's calculations, this amounts to 35 billion won annually. So now, they're first diverting this water to maintain Cheonggyecheon Stream, and then reusing it for road cleaning, landscaping, firefighting, and even heating/cooling systems. It's like having an extra water pipe right under your feet.

There's a city that demolished a perfectly fine overpass to bring back a stream that flowed beneath it. Covering the overflowing and smelly waterway with concrete was once considered the right answer, but as time passed, the structure itself began to decay. When the lid was removed, a pathway for wind opened up along with the water, causing the surrounding temperature to drop by over 3 degrees Celsius. However, because there's no natural flow and water from the Han River has to be pumped in daily, it faces criticism for being an artificial stream.

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.

There are trees planted to block the wind, but they actually create a forest that invites it. Instead of planting them in a wide cluster, they are planted in a long line to create a pathway for the cold air generated in the mountains to flow into the city. This air, descending the hillsides overnight, is weak and gets blocked even by a single building. Therefore, they calculate the actual paths of wind flow and plant the trees only in pre-existing openings, like along riverbanks.

There's a construction project digging 40 meters underground to prevent flooding. Instead of quickly draining rainwater, the idea is to temporarily store it deep underground where it's currently empty. Beneath Gangnam, the ground is already packed with subways and utility lines, so they have to dig down to depths no one uses to create tunnels. The 'water bowl' in Yangcheon-gu, built earlier, managed to protect the neighborhood even during heavy rains that flooded many parts of Seoul.

Stone walls with numerous holes withstand typhoons. The principle is not to block the wind but to let it pass through the holes, thus dissipating its force. It's just like a screen door in front of a fan remaining intact. Furthermore, these walls absorb shock by swaying. The total length of these walls is 22,000 kilometers, half the circumference of the Earth. The nickname 'Heukryong Manri' (Black Dragon Ten Thousand Ri) isn't just for show.