In megacity Seoul, Korea, the restoration of a culturally important river teaches key lessons. A river can be recovered and restored even in a large and dense central business district, with multiple positive effects. These include providing habitat for nature, preserving cultural heritage, providing access to nature for the public, flood control, and microclimate regulation. The river restoration also promoted more sustainable transport forms over roads and cars removed to make space for the river and its surrounding parks.

Clearing the transportation hurdle

Seoul is classified a megacity with a population of circa 23 million in the greater metropolitan region. The Cheonggyecheon river (pronounced “chung-gye-chun”) was a highly appreciated and used seasonal river that dissects the city. After increasing pollution and canalisation, it was concreted over and a six-lane highway was built over it during the 1970s.

But a politician, Lee Myung-bak, led a campaign as Seoul’s mayor to restore the river – and was elected South Korea’s president a few years after. The success of the Cheonggyecheon river restoration has had massive ripple effects: in East Asia and North America, cities are studying the project to gain its benefits for ecology, environmental quality, and urban sustainability. Within South Korea, nearly 100 other elevated roads have been scheduled for removal.

Green mobility replaced cars

The strongest objection to the project was that the highway, carrying 160,000 cars per day, was vital to the city’s transportation and economy, even though perpetually congested. In fact the project provided transportation improvements of many kinds. With reduced road capacity in the centre, Seoul radically expanded its bus rapid transit (BRT) service, and better integrated it into other public transport, e.g. underground rail, buses, as well as improved infrastructure for non-motorised transport. Cars disappeared, buses ran faster and were better utilised, subway use increased. Walking was also facilitated.

Many benefits to environment

The environmental benefits of the restored river are multiple. Air quality improved: one report cites small-particle air pollution decreasing from 74 micrograms per cubic metre to 48 in the vicinity of the river.

Microclimate benefits come from the river acting as a natural air-conditioner: temperatures in the river corridor are 3-4 degrees C lower than areas only 400 metres away, and wind speeds are on average 50% higher than before the river was recovered. These are important benefits for climate adaptation, in addition to the increased resilience against flooding when a city has open watercourses.

The natural ecology has benefited, e.g. birds, fish, insects, and plants. According to a 2009 report, the number of bird species in the river corridor increased from 6 to 36, fish species from 4 to 25, and insect species from 15 to 192. The green corridor is eight km long and 730 metres wide, with a 400 ha park, and features waterfalls, bridges, and running tracks. There are remaining critical questions about the sustainability tradeoffs when pumping water artificially to a newly restored river. Critics of the river restoration question the overall benefits to citizens quality of life and whether the process had sufficient input from civil society and environmental actors.

John Vidal, 2007, “U-TURN”, Resurgence Magazine, http://www.resurgence.org/magazine/article204-u-turn.html

Preston L. Schiller, Eric C. Bruun, Jeffrey R. Kenworthy, 2010, An introduction to sustainable transportation: policy, planning and implementation, London: Earthscan

Key data are retrieved from the UN World Urbanization Prospects: The 2011 Revision, http://esa.un.org/unup/unup/index_panel2.html