Cheonggyecheon

Cheonggyecheon is a 10.9 km stream and public space in downtown Seoul, South Korea. A natural stream sourced from the Suseongdong Valley in Inwangsan, it was historically maintained as part of Seoul's early sewerage until the mid-20th century, when post-Korean War rapid economic development and deteriorating conditions prompted the filling of the stream with concrete and the construction of an elevated freeway, the Cheonggye Expressway, in its place. In 2003, the city government began an urban renewal project to disassemble the expressway and restore the stream, which was completed in 2005 at a cost of over (approximately US$281 million).

The Cheonggyecheon restoration project initially attracted significant public criticism, but since its opening in 2005 it has become popular among residents and tourists.

Geography
Cheonggyecheon is an 10.84 km stream flowing west to east through downtown Seoul, and then meeting Jungnangcheon, which connects to the Han River and empties into the Yellow Sea.

History
The stream was named as Gaecheon ("open stream") after the first refurbishment project to construct a drainage system during the Joseon period. The work, which included dredging and bolstering the banks of the stream and building bridges, was carried out every 2–3 years during this period from the reign of Taejong, the third king of Joseon. King Yeongjo especially undertook the refurbishment work as a national project.

Gaecheon was renamed to Cheonggyecheon, its current name, when Korea was under Japanese rule. During this time, financial difficulties disrupted and prevented Japanese forces from covering up the stream despite several attempts to do so.

After the Korean War, more people migrated into Seoul to make their living and settled down along the stream in shabby makeshift houses. The accompanying trash, sand, and waste, and deteriorating conditions resulted in an eyesore for the city. The stream was covered up with concrete over 20 years starting in 1958, and a 5.6 km, 16 m elevated highway was completed in 1976. The area became an example of successful industrialization and modernization of South Korea.

Restoration
In July 2003, Mayor of Seoul Lee Myung-bak, initiated a project to remove the elevated highway and restore the stream. It was a major undertaking since the highway had to be removed and years of neglect and development had left the stream nearly dry. 120,000 tons of water were to be pumped in daily from the Han River, its tributaries, and groundwater from subway stations.

To address the consequent traffic problem, the Cheonggyecheon Restoration Project Headquarters established traffic flow measures in the downtown section affected by the restoration work and coordinated changes in the downtown traffic system based on the research of the Cheonggyecheon Restoration Research Corps.

The restoration of two historic bridges, Gwangtonggyo and Supyogyo, was also a contentious issue, as several interest groups voiced opinions on how to restore historical and cultural sites and remains and whether to replace the bridges or not.

The Cheonggyecheon restoration project had the purpose of preserving the unique identity of the natural environment and the historic resources in the CBD of Seoul, and to reinforce the surrounding business area with information technology, international affairs and digital industries.

Achievements
The stream was opened to the public in September 2005 and was lauded as a major success in urban renewal and beautification. However, there was considerable opposition from the previous mayoral administration of Goh Kun, which feared gentrification of the adjacent areas that housed many shops and small businesses in the machine trades.

Creating an environment with clean water and natural habitats was the most significant achievement of the project. Species of fish, birds, and insects have increased significantly as a result of the stream excavation. The stream helps to cool down the temperature on the nearby areas by 3.6 °C on average versus other parts of Seoul. The number of vehicles entering downtown Seoul has decreased by 2.3%, with an increasing number of users of buses (by 1.4%) and subways (by 4.3%: a daily average of 430,000 people) as a result of the demolition of the two heavily used roads.

The project sped up traffic around the city when the motorway was removed. It has been cited as a real-life example of Braess's paradox.

Cost
Budgeted at, the final cost of the project was over (approximately US$281 million).

Some Korean environmental organizations have criticized its high costs and lack of ecological and historical authenticity, calling it purely symbolic and not truly beneficial to the city's eco-environment. Instead of using the restoration as an instrument of urban development the environmental organizations have called for a gradual long-term ecological and historical recovery of the entire Cheonggyecheon stream basin and its ecological system.

The cost of managing Cheonggyecheon has been rising every year. From October 2005 to the end of 2016, maintenance and management cost of Cheonggyecheon totalled, which averaged out to per year.