Buried Wetlands Rise from the Grave

This evening, Hurricane Sandy's storm surge will combine with astronomical high tides to give eastern seaboard cities an exciting preview of sea level rise. Forecasters are predicting storm surges up to 10 feet above the average high water mark — especially in western Long Island Sound and New York Harbor, where the storm is funneling massive volumes of seawater into the right-angled corner formed by New Jersey and Connecticut.

As I wrote last week in Grist, most big cities have buried their wetlands and creeks underground. But big storms and flood events like this one have a way of making those hidden waterways reassert themselves, as underground sewers and stormwater channels fill up beyond their design capacity and overflow into the streets above.

That can happen in unexpected places. Here in Portland it wasn't even particularly stormy today, and there was only light rain. But the astronomical high tide did push water up to the surface of Somerset Street, four blocks away from Back Cove (note the empty tree wells — similar events killed the street trees planted here in 2006 due to salt water in the roots).

Meanwhile, in Philadelphia, heavy rains may once again cause problems in the sewer-bound Mill Creek.

And in New York City's Boerum Hill and Park Slope neighborhoods, the old marshes of the Gowanus Canal may once again take over the streets. This overlay of the Brooklyn section of the 1782 British Headquarters Map shows (roughly) how far the old marshes of the Gowanus used to extend across central Brooklyn:

On Grist.org: "Sewer Discretion is Advised"

I've just published a new film review on the environmental news site grist.org about two new documentaries that profile the new watersheds. Here's an excerpt:

Most urban streams and creeks are hidden from sight — in huge sewer tunnels under streets and expressways, in concrete ditches behind razor-wire fences, and sometimes even in pipes under the manicured lawns and gardens of city parks.

These are hardly the kinds of places you’d see on the cover of an L.L. Bean catalog — although you might find a few L.L. Bean catalogs in these concrete creeks.

But a growing network of urban explorers, who sometimes call themselves “drainers,” are sneaking into the storm sewers and aqueducts to rediscover these long-hidden waterways. They’re finding lush forest groves among the concrete ditches and waterfalls and grand vaulted grottoes in underground sewers. Their photography and field notes remind residents that the rivers and streams that nursed their cities’ early growth still survive below the pavement, and are still worthy of appreciation — maybe even restoration.

Now, not one, but two new documentary films follow this small subculture of urban river enthusiasts, and celebrate the outsized impact of their civilly disobedient urban river expeditions.

Read the rest at grist.org.