Seoul, New York and Ann Arbor Expose Watery Havens

OHM is currently designing a low impact development (LID) stormwater management project for the University of Michigan and the City of Ann Arbor, on U of M's Arboretum property. The project includes step-pool dissipater structures, an intermittent watercourse, a "meadow" infiltration basin and restoration with native plantings. We're pleased to see that Michigan's Ann Arbor is in good company with Yonkers and Seoul, all seeking ways to combine environmental pursuits with urban energy.

Excerpted from the New York Times, July 16, 2009:

In New York State, a long-stalled revival effort for Yonkers’s ailing downtown core that could break ground this fall includes a plan to re-expose 1,900 feet of the Saw Mill River, which currently runs through a giant flume that was laid beneath city streets in the 1920s.

Cities from Singapore to San Antonio 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 concrete-lined 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 seven miles 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 Cheonggyecheon (pronounced chung-gye-chun) has been greatly enriched, with the number of fish species increasing to 25 from 4. Bird species have multiplied to 36 from 6, and insect species to 192 from 15.

The recovery project, which removed three miles of elevated highway as well, also substantially cut air pollution from cars along the corridor and reduced air temperatures. Small-particle air pollution along the corridor dropped to 48 micrograms per cubic meter from 74, and summer temperatures are now often five degrees cooler than those of nearby areas, according to data cited by city officials.