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"I'm actually speaking to you from a boat now. I live on it. I'm a sailor, I've grown up around water and have a lot of respect for its power, but also for the pleasure of interaction with water."

Peter Anderson, based in Seattle, in the northwestern state of Washington, is half the team with his brother Mark, behind what may be the friendliest approach yet to floodwater control in urban areas. The word "alluvial" refers to sediment -- the sand, stones, and other debris that is usually swept along by water in rivers and on beachfronts, a natural action in bodies of water. 

The Andersons' concern in the aftermath of Hurricane Katrina's strike on New Orleans was twofold: First, the hardened barriers to floodwaters there failed to prevent catastrophic destruction; and second, in non-flooding conditions, the flood walls are inconvenient and restrictive of a society living on the banks of the Mississippi River.

While a hard wall approach simply tries to knock the waters back, the Sponge Comb grows larger and larger as water is trapped inside its absorption materials, swelling into a temporary embankment, or levee as they're known in New Orleans. Once the high waters subside, the Sponge Comb dries into what it was originally, a kind of soft street furniture. 

"We’re looking for a more symbiotic relationship with waterfronts, rather than concrete walls," says Anderson, "allowing people and animals to move back and forth to the waterfront in dry times and then changing with rising water in flood times.

"When there was a focus on this whole issue at the Venice Biennale," Anderson says, "we were invited to put some of the Sponge Comb structures into the courtyard of the American exhibition.

Tourists in Venice enjoyed using the green-on-green cactus-colored fingers of the structures as places to talk, have coffee and rest. "At first, the docents at the pavilion were telling people not to sit there," Anderson says. "And we talked with them and asked them to allow people to sit there, let kids climb on them, enjoy them.

"And cactus is a great example of something in nature made to absorb moisture, hold it for long periods, dry up in a period of drought."

The super-absorbent materials inside the big fingers of the Alluvial Sponge Comb were created by manufacturers to a small extent for cleanup operations but primarily have used them in diapers. In those diapers, the idea is to absorb and wick away water temporarily.  In the use we've projected for the Sponge Comb, we take advantage of the fact that as it dries out in the sun after a flood, it shrinks.

Peter and Mark Anderson are hoping for funding to place live-test installations of the Sponge Comb in waterfront locations. There can be a beach-erosion application, Peter Anderson notes, as well as the more expected urban-flooding uses.

"Part of the idea is that erosion is slowed down because plants and silt build up between the fingers of the Sponge Comb" -- that "alluvial" function of debris-gathering natural to bodies of water. "One concept is to have the things staked into the sand, attract the sand to the beach and then decompose as it becomes buried in the sand and is part of the beach."

In the end, it's an effort to turn around the response to waterfront issues by getting closer to the inclusiveness of a natural response and away from the "us vs. the water" traditions of the past. 

"Society has tried to make our cities' systems separate from flooding," he says, "which disrupts the systems of nature, of course.  We always think, instead, about the connection of the water and the city."

Designed by:
Mark Anderson (AIA); Peter Anderson (FAIA), San Francisco, USA.

www.AndersonAnderson.com 

Written by Porter Anderson