By ANDREW C. REVKIN SEOUL,


South Korea - For half a century, a dark tunnel of crumbling concrete encased some five kilometers of a placid stream bisecting this bustling city.

The waterway had been a centerpiece of Seoul since a Choson Dynasty king selected the new capital 600 years ago, enticed by the graceful meandering of the stream and its 23 tributaries. But in the industrial era after the Korean War, the stream, by then a rank open sewer, was entombed by pavement and forgotten beneath a lacework of elevated expressways as the city’s population swelled toward 10 million.

Today, after a $384 million recovery project, the stream, called Cheonggye cheon, burbles between reedy banks, liberated from its dank sheath. Picnickers cool their bare feet in its filtered water, and carp swim in its tranquil pools. The restoration in Seoul is part of an expanding environmental effort in cities around the world to “daylight” rivers and streams by peeling back pavement that was built to bolster commerce and serve automobile traffic decades ago.

Cities from Singapore to San Antonio, Texas, have been resuscitating rivers and turning storm drains into streams. In Los Angeles, residents’ groups and some elected officials are looking anew at buried or concretelined creeks as assets instead of inconveniences, inspired partly by Seoul’s example.

By building green corridors around the exposed waters, cities hope to attract affluent and educated workers and residents who appreciate the feel of a natural environment in an urban setting.

Environmentalists point out other benefits. Open watercourses handle flooding rains better than buried sewers do, a big consideration as global warming leads to heavier downpours. The streams also tend to cool areas overheated by sun-baked asphalt and to nourish greenery that lures wildlife as well as pedestrians.

Some political opponents have derided Seoul’s remade stream as a costly folly, given that nearly all of the water flowing between its banks on a typical day is pumped there artificially from the Han River through 11 kilometers of pipe.

But four years after the stream was uncovered, city officials say, the environmental benefits can now be quantified. Data show that the ecosystem along the Cheong gye cheon (pronounced chung-gye-chun) has been greatly enriched. The number of fish species has increased to 25 from 4, bird species to 36 from 6, and insect species to 192 from 15.

The recovery project, which removed almost five kilometers of elevated highway as well, also substantially cut air pollution from cars along the corridor and reduced air temperatures. And even with the loss of some vehicle lanes, traffic speeds have picked up because of related transportation changes like expanded bus service, restrictions on cars and higher parking fees.

“We’ve basically gone from a caroriented city to a human-oriented city,” said Lee In-keun, Seoul’s assistant mayor for infrastructure, who has been invited to places as distant as Los Angeles to describe the project to other urban planners.

Efforts to recover urban waterways are nonetheless fraught with challenges, like convincing local business owners wedded to existing streetscapes that economic benefits can come from a green makeover.

Yet today the 90,000 daily visitors to the Cheong gye cheon’s banks include merchants from some of the nearby shops who were among the project’s biggest opponents early on. On a recent evening, picnickers along the waterway included Yeon Yeong-san, 63, who runs a sporting apparel shop with his wife, Lee Geum-hwa, 56, in the adjacent Pyeong hwa Market.

Mr. Yeon said his family moved to downtown Seoul in the late 1940s, and he has been running the business for four decades. He said parking was now harder for his customers. But, he said, “because of less traffic, we have better air and nature.”

He and his wife walk along the stream every day, he added. “We did not think about exercising here when the stream was buried underground,” he said.





A stream in Seoul, paved over for decades, is now uncovered and the center of an urban park. Other cities are considering similar projects.