Nature amid the concrete

A few days ago in Lakewood, a crowd of 300 gathered on the west bank of the San Gabriel River flood-control channel to take a walk. First, there were a few speeches. Afterward, a park supervisor showed slides of native California shrubs and trees. Then the audience -- awfully patient 6- and 7-year-olds in tow -- started out on the mile-long trail that city officials had just formally dedicated to the enjoyment of nature.

But what nature is that? The answer will determine if a vastly more ambitious plan for nearly 32 miles of the flood-control system in Los Angeles will restore it to something resembling a river. The parks, residential units, offices and bike paths in the restoration plan outlined by city officials and the Army Corps of Engineers earlier this month could take as long as 50 years to complete and cost $2 billion.

It might be said that with enough money and passion, much of the riverside in L.A. could one day look like Lakewood's mile of green and pleasant land. In the process, we would redefine what nature means in Los Angeles.

In Lakewood, both banks of the river's channel have become 80 acres of parkland. The new trail -- on a strip of power-line right of way -- meanders on the west bank. The city's equestrian center and a park with picnic shelters, baseball diamonds and bridle paths fill the east bank. Most of that is under power lines too.

It took 30 years to assemble this green corridor through rows of tract houses, so the riverbanks' landscape has a mixed look. Mature eucalyptus trees tower eastward. Newly established elderberries are clumped along the trail. From there, walkers look down into the man-made void of the San Gabriel River. Water runs in the "low flow" slot in the middle of the flood channel most days; the concrete on either side glares brightly. Two egrets -- white plumes against greater white -- stood motionless at the edge of the slot as the first walkers on the new trail passed. A juvenile pelican skimmed to a perfect water landing nearby. After a moment, it took wing again, and the pelican rose in company with a blue heron that was almost lavender in the winter light.

Is that nature? And if it is (as I think it is), what should the proportion of concrete to heron be?