Why Did Joseon Improve Cheonggyecheon? ― How Hanyang (Seoul) Managed Its Flood Problem
Hanyang, the capital of the Joseon Dynasty and present-day Seoul, is often described as an ideal site based on the traditional Korean principle of baesanimsu—a settlement backed by mountains and facing water.
The walled city was surrounded by four major mountains: Bugaksan to the north, Inwangsan to the west, Naksan to the east, and Namsan to the south. Beyond them, the Han River flowed along the southern side of the capital. These geographical features provided favorable conditions for building a capital, offering advantages in defense, feng shui, and transportation.
However, Hanyang’s geography also concealed a serious weakness.
Water.
During periods of heavy rainfall, water rushed down from the surrounding mountains and quickly converged within the walled city. When streams overflowed, low-lying areas of the capital were flooded, damaging houses and roads.
In other words, the very mountains that helped protect Hanyang could also funnel large amounts of rainwater directly into the heart of the city.
To keep Hanyang, the capital of the Joseon Dynasty, functioning safely and effectively, the government had to continuously manage and improve the stream known as Gaecheon (開川), which flowed through the heart of the city and is known today as Cheonggyecheon.
In a sense, the history of Hanyang was a story of taking advantage of the natural benefits of its geography while using human intervention to overcome the vulnerabilities created by that same landscape.
1. Hanyang’s Geographical Weakness — Water Converged in the City Center
Hanyang was built in terrain resembling a basin, surrounded by mountains.
Bugaksan stood to the north, Inwangsan to the west, Naksan to the east, and Namsan to the south.
The problem became apparent whenever heavy rain fell.
Rainwater from the surrounding mountains flowed rapidly downhill, following numerous small waterways and converging in the lower-lying areas of the walled city.
The main drainage channel that carried this accumulated water out of the city was Gaecheon—the stream known today as Cheonggyecheon.
The course of Cheonggyecheon was closely connected to Hanyang’s topography.
Water descending from the mountainous areas to the west and north of the city flowed through the urban center from west to east, eventually entering Jungnangcheon and then draining into the Han River.
Cheonggyecheon, therefore, was much more than a small stream flowing through the walled city.
It served as Hanyang’s main drainage channel, carrying rainwater and wastewater from the urban center out of the city.
2. The Problem Was Cheonggyecheon’s Drainage Capacity
Unlike modern engineered waterways, natural streams do not maintain a constant width and depth.
During heavy rainfall, water rushing down from the surrounding mountains carried not only rainwater but also soil and sand. As this sediment accumulated on the streambed, the channel gradually became shallower.
As Hanyang grew, the problem became even more complicated.
The city’s population increased, and more houses and other structures were built along the stream. Household waste and various forms of refuse also flowed into Gaecheon.
As sediment and waste raised the streambed, the channel could hold less water. This meant that even the same amount of rainfall could increasingly cause the stream to overflow and flood surrounding areas.
During the summer monsoon season or periods of intense rainfall, large amounts of water rushed down from the surrounding mountains and poured into Gaecheon within a short period of time, putting the low-lying areas of the walled city at risk of flooding.
For the Joseon government, therefore, properly managing Gaecheon was not simply a matter of improving the city’s appearance.
It was a major flood-control project directly tied to the safety of the capital, Hanyang.
3. King Taejong’s Gaecheon Project — Transforming a Natural Stream into an Urban Drainage Channel
One of the most important early Joseon projects aimed at addressing Hanyang’s drainage problems was the improvement of Gaecheon during the reign of King Taejong.
In 1411, Taejong established the Gaegeo Dogam, a temporary government office responsible for the project, and began efforts to improve the stream. In 1412, a large-scale construction project was carried out with a massive labor force. According to the Veritable Records of King Taejong, as many as 52,800 soldiers from Gyeongsang, Jeolla, and Chungcheong provinces were mobilized for the dredging of Gaecheon (National Institute of Korean History, 1412).
The main purpose of the project was to improve the network of waterways within the walled city, remove sediment that had accumulated on the streambed, and allow water to drain more efficiently.
Stone embankments were constructed where necessary, and the course of the stream was also improved to facilitate the flow of water.
Through this project, Cheonggyecheon increasingly took on the role of a systematically managed urban drainage channel, rather than simply remaining a natural stream.
However, this does not mean that the entire Cheonggyecheon was newly constructed like a modern artificial canal.
The project was based on an existing natural stream and involved extensive improvements to its waterways, embankments, and streambed. It is therefore more accurate to describe Cheonggyecheon as a natural stream that was artificially improved to serve as an urban drainage channel.
4. Over Time, Cheonggyecheon Became Shallow Again
The problem, however, was not solved by a single construction project.
Whenever it rained, soil and sand continued to wash down from the mountains surrounding Hanyang.
At the same time, as the city’s population grew, sediment, garbage, and other waste continued to accumulate in Cheonggyecheon.
By the late Joseon period, Hanyang had developed into a major city, increasing the amount of rainwater and wastewater that Cheonggyecheon had to handle.
Over the centuries, sediment gradually accumulated on the streambed, making the channel increasingly shallow and reducing its capacity to carry water. As a result, the risk of flooding also increased (Seoul Museum of History, 2017).
By the late Joseon period, Cheonggyecheon had once again become shallow due to the continuous accumulation of sediment and waste.
Eventually, in the 18th century, King Yeongjo launched a major project to address this chronic problem in the capital.
5. King Yeongjo’s Dredging Project — Digging Out the Cheonggyecheon Streambed
In 1760, King Yeongjo carried out a large-scale dredging project known as juncheon (濬川).
Juncheon literally refers to the process of removing accumulated soil and sand from the bottom of a stream in order to deepen its channel.
The project was a major flood-control effort designed to remove the enormous amount of sediment that had accumulated on the bed of Gaecheon over many years, improve the waterway, and restore the stream’s drainage capacity (Seoul Museum of History, 2017).
It is estimated that the project mobilized a cumulative workforce of approximately 200,000 people, including residents of Hanyang, soldiers, and hired laborers.
King Yeongjo did not simply dredge the stream once and consider the problem solved.
He established systems and standards for the continued management of juncheon (dredging) and ensured that the condition of the stream was regularly monitored and maintained.
This marked an important shift in the management of Cheonggyecheon. Rather than being treated as a one-time construction project, maintaining the stream developed into an ongoing form of urban management essential to the functioning and safety of the capital, Hanyang.
6. Why Was Cheonggyecheon So Important to the Joseon Dynasty?
Hanyang was the political, administrative, and economic center of the Joseon Dynasty.
It was home to royal palaces and government offices, while large numbers of officials, merchants, artisans, and ordinary residents lived within the city.
If such a densely populated capital were repeatedly flooded during the summer monsoon season, the functioning of the city itself could be severely disrupted.
Managing Cheonggyecheon, therefore, was about much more than simply maintaining a single stream.
It was a crucial part of urban infrastructure management necessary to keep the great capital of Hanyang functioning.
Interestingly, Hanyang’s geographical strengths and weaknesses came from the very same landscape.
The mountains surrounding the walled city served as natural defensive barriers and also held important symbolic meaning in traditional feng shui.
Yet during the summer monsoon season, rainwater flowing down from those same mountains converged in the city center.
In other words, the mountains surrounding Hanyang were both a shield protecting the capital and a catchment area that increased its vulnerability to flooding.
Conclusion — Even an Ideal Location Required Human Management
Hanyang was never a perfect capital simply because of its location.
Surrounded by Bugaksan, Inwangsan, Naksan, and Namsan and situated near the Han River, the city enjoyed several geographical advantages that made it well suited to serve as a capital.
At the same time, however, its topography created a persistent problem. Rainwater descending from the surrounding mountains converged in the urban center, repeatedly exposing the city to flooding and inundation.
The Joseon Dynasty did not simply accept these environmental limitations.
King Taejong carried out major improvements to Gaecheon, establishing a more effective drainage system for Hanyang. Centuries later, King Yeongjo launched a large-scale dredging project to remove the enormous amount of sediment that had accumulated on the streambed.
Cheonggyecheon, therefore, should not be viewed simply as a stream flowing through the heart of modern Seoul.
For centuries, it served as a crucial urban drainage channel that the Joseon Dynasty continuously managed in order to overcome one of Hanyang’s major geographical vulnerabilities.
Its history also reveals an important lesson.
No matter how favorable a city’s location may be, it cannot survive and prosper without effectively managing its natural environment.
Hanyang has remained the center of Korea for more than six centuries. Behind this remarkable continuity were not only the natural advantages of its location, but also generations of human effort to manage, reshape, and adapt to the landscape.
References
National Institute of Korean History. (1412). Veritable Records of King Taejong, Vol. 23, 12th year of King Taejong, 1st month, 15th day, 2nd entry. Veritable Records of the Joseon Dynasty. Veritable Records of King Taejong (Taejong Sillok, 太宗實錄). https://sillok.history.go.kr/id/kca_11201015_002?
https://museum.seoul.go.kr/www/board/NR_boardView.do?bbsCd=1015&seq=20170824111412692&sso=ok&
Seoul Museum of History. (2017, August 24). How was Cheonggyecheon managed during the Joseon Dynasty? “Juncheon: Connecting King Yeongjo and the People” special exhibition.
https://museum.seoul.go.kr/www/board/NR_boardView.do?bbsCd=1015&seq=20170824111412692&sso=ok&
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