Since the 1970s, the Cheonggyecheon River in downtown Seoul, South Korea was covered by a busy, multi-lane roadway and elevated highway. An engineering survey conducted in 2000 revealed structural weaknesses in these roads and indicated a need for a costly renovation project. In lieu of investing in this congested traffic infrastructure, the Seoul City Government opted to demolish the roads and restore flow to the river in order to improve the environmental and aesthetic state of the downtown area. A two-year project costing nearly $1 billion was thus begun in 2003, and the river was re-exposed and made the focal point of a larger urban renewal effort. Traffic was rerouted, bridges were built across the river, public parks and recreational space were created, and sites of historic and cultural importance in the general vicinity were renovated. In the two years since the project’s completion, more than 50 million visitors have flocked to the site, and investment in the downtown area has increased dramatically. Moreover, the reduction in traffic has resulted in a significant improvement in air quality and a decrease in local temperatures during the summer months. These improvements in environmental conditions have been accompanied by the return of several species of birds, fish and insects to the restored Cheonggyecheon. The enthusiasm and excitement engendered by this project have attracted the attention of cities elsewhere and have made it a model for other urban renewal efforts.
Country or Territory:
Freshwater Rivers & Streams
Area being restored:
6 km of river channel
Seoul City Government
Primary Causes of DegradationUrbanization, Transportation & Industry
Degradation of the Cheonggyecheon River began in the fifteenth century with the deepening and widening of the river channel; the construction of a stone and wood embankment; the use of the watercourse as a natural sewer system; and increased sedimentation resulting from the deforestation of surrounding areas. Although regularly dredged and modified into the twentieth century, in the 1950s the river channel was still a seasonal stream where people went to wash clothes and where children went to play.
As Seoul slowly grew from being semi-rural to a vast, smog-bound East Asian metropolis, the Cheonggyecheon – which means “clear valley stream” – became little more than a sewer. By 1970, the riverside was lined with slums, and the water became progressively more polluted, having been first channelized and then topped with concrete. As urbanization and industrialization gained momentum and cars became more ubiquitous, the river bed was converted into a 6-kilometer roadway with a 5.8-kilometer, 6-lane elevated highway running above it. Prior to restoration, more than 168,000 cars traversed this stretch each day, and 62.5% of these were through-traffic.
The consequences of this congested transit system along Cheonggye Street had grown very serious. Air pollution–particularly criteria pollutants–was well above acceptable levels, and nitrogen oxide pollution exceeded the environmental air quality standard for Seoul. Moreover, levels of benzene, a carcinogenic Volatile Organic Compound (VOC), were also high. A health awareness survey of people living or working near Cheonggyecheon suggested that the residents were more than twice as likely to suffer from respiratory diseases compared to people in other areas (SDI, 2003A). In addition to air pollution, noise pollution along this stretch topped established standards for commercial areas and was a serious hindrance to a pleasant living and working environment.
– To improve environmental conditions in the downtown area
– To create a focal point of both historical significance and aesthetic appeal
– To trigger long-term economic growth by attracting tourists and investors
– To aid in making Seoul a financial and commercial hub in the East Asian region
The project does not have a monitoring plan.
Description of Project Activities:
Demolition work began on July 1, 2003, and the Cheonggye elevated highway was completely dismantled by October 5, 2003. The demolition of structures covering the actual stream began on August 18 2003 and were fully dismantled by December 30, 2004. In order to reduce noise and dust created during demolition, the city used diamond wire saws and wheel saws. A total 680,000 tons of waste was generated during the demolition work. Of this, 100% of the scrap iron and steel was to be recycled and 95% of the waste concrete and asphalt reused. The Cheonggyecheon was restored as an urban stream with natural qualities, a human- and environment-friendly space with a waterfront and walks along the banks. Proper flood management was a top priority in designing the stream. In consideration of the increasing incidence of floods and the extraordinarily heavy volume of torrential rainfall during the summer months, the city built embankments that can withstand the worst possible flood expected to occur every 200 years. Furthermore, the minimum number of bridges was planned in order to allow maximum water flow during heavy rainfall, while several covering structures were installed in order to prevent dirty water from flowing into Cheonggyecheon during these heavy rains. Because Cheonggycheon is an intermittent stream (being seasonally dry), it requires additional flow to maintain a maximum 40-cm depth throughout the year. Therefore, more than 120,000 tons of water per day will be introduced into the Cheonggycheon Stream from three sources: groundwater, the Han River, and water processed at the Jungnang Sewage Treatment Plant. The targeted level of water quality is the 2nd class, BOD 3mg/l. The Jungnang facility will be expanded to treat a total of 1.95 million tons of sewage per day, but until the expansion takes place, most of the water will come from the Han River. Project planners took several measures aimed at minimizing traffic congestion in this downtown area and ensuring adequate transit infrastructure in the absence of the Cheonggye motorway. On either side of the stream, 13.5m were allocated to accommodate sidewalks; two-lane, unidirectional roads; and loading/unloading zones. The newly designed traffic system limits left turns and U-turns in an effort to prevent traffic delays and protect the environment from car emissions. A total of 22 new bridges were constructed over the Cheonggyecheon, 5 of which are pedestrian bridges and 17 of which are motor vehicle bridges. Besides traffic and flood control, public access to the new river was also an important consideration in the planning process. The restored stream will be accessible at 17 locations. Terraces and lower-lever sidewalks were built along the upper and lower reaches of the stream, and the mid-stream section was designed as a water-friendly space. River parks and public art were incorporated in several locations in order to provide a venue for performances and cultural events and to enhance the overall potential for public enjoyment of the new space. Historic and cultural restoration of the downtown area was another important aspect of the project. Historic streets and buildings were slated for beautification, and the Gwangtonggyo Bridge, a bridge built over the Cheonggyecheon Stream in 1410, was restored to its original state at a cost of over $5.9 million. Gwangtonggyo had been buried 95 years ago when the construction for tram rails between Jongno and Namdaemun was begun in 1910. It was the biggest bridge in Hanseong (the old name of Seoul) during the Joseon Dynasty (1392~1910), and it is now functioning once more for the people's enjoyment.
Ecological Outcomes Achieved
Eliminate existing threats to the ecosystem:
In spite of uncertainty about the ramifications this project would have for traffic patterns in the area, officials have been pleased with outcomes thus far. With the demolition of the old motorway, drivers were forced to find alternate routes, rely less heavily upon their automobiles for transportation, and/or begin using mass transit. The relative absence of infrastructure supporting large volumes of traffic, in combination with a redesigned bus system aimed at providing a viable alternative to car travel, has resulted in a dramatic decrease in traffic along this stretch of downtown. Consequently, air quality has improved considerably, and according to the Seoul Development Institute, the amount of suspended particulate matter (SPM) in the area around the river has dropped by 19 percent. Moreover, the decrease in traffic and the creation of open space has lowered summer surface temperatures and curbed the heat island effect somewhat. In a recent study, researchers found that temperatures in the immediate vicinity of the river were on average 3.6ÂºC lower than places 400 meters away. A different study found that in 2003 (before restoration), a square meter of land received 300 to 500 watts of heat, whereas after the project's completion the amount of heat decreased to 100-150 watts. Aiding this cooling effect is an increase in wind speed and ventilation since the removal of the motorway. Researchers found that average wind speeds after the restoration were 50% higher than they had been in the same period before the project. Besides having a mitigating effect on traffic, air pollution and the heat island phenomenon, the restoration of flow to the Cheonggyecheon has created environmental conditions more conducive to wildlife. According to a survey on the ecology of the stream conducted between March and April 2005 by the Seoul Metropolitan Facilities Management Corporation, 30 species of birds and 13 species of fish were present in the stream, an increase of 6 and 5 species, respectively, over the same period in the year prior to restoration. The return of marsh plants and clean water to the Cheonggyecheon has resulted in an increase in benthos and plankton, and these have, in turn, attracted several species of fish (e.g. carp, minnows, and fry) from the Jungnangcheon, another nearby stream. These improved conditions have brought several notable bird species, including: mandarin ducks, sparrow hawks, and Korean buzzards (a species listed as endangered by the Korean Ministry of the Environment), all of which were newly discovered in the area.
Factors limiting recovery of the ecosystem:
The restoration project only covers a portion of the Cheonggyecheon watercourse--the area from the Donga building in the CBD to the ending point of the covered road. Some ecologists argued that the restoration work should be extended to the upper reaches of the Cheonggyecheon, but due to traffic problems and costs, it was decided to exclude this stretch for the time being. Instead, pipes were installed between Cheonggyecheon and its origins, Inwangsan (Mt.) and Bugaksan (Mt.), to continuously provide clean water to the stream.
Socio-Economic & Community Outcomes Achieved
Economic vitality and local livelihoods:
When the public first learned of the idea to demolish the motorway and restore flow to the river, there was fierce opposition and protests from nearby vendors and business owners who depended on the area (and its heavy traffic) for their livelihoods. In the two years since restoration, however, the number of visitors to Cheonggyecheon River has surpassed 50 million, and community members have been happy about all the improvements they are witnessing. The area has begun to attract a growing number of tourists and investors, and property values and commercial activity are rapidly increasing. While the economic gain and renewed interest in development have been promising for many, there are some who fear that the renewal project poses a danger of gentrification and that local people will soon be unable to afford the rising costs of living and working in this area.
Key Lessons Learned
The successful implementation of this project, and the excitement it has created for residents of Seoul and members of the international community, has provided incentive for similar projects in Korea and elsewhere in the world. The new mayor of Seoul is considering a project along the Han River that would decrease space for cars and replace it with pedestrian walkways. Shanghai is also thought to be considering a similar, though smaller, scheme; and Tokyo has expressed interest in removing an elevated roadway above an ancient bridge. In 2006, the mayor of Los Angeles traveled to Seoul to see the project firsthand and discuss the possibilities for conducting a similar restoration of the Los Angeles River. The Cheonggyecheon River Project has become a showpiece for environmentalists and urban planners alike.
To keep the river flowing, water must be pumped from the Han River and underground water reserves at a cost of more than 200 million yen a year.
Sources and Amounts of Funding
960 million USD The project is estimated to have cost the government of Seoul over 900 billion won (approximately 960 million USD).
City of Seoul Project Page