Gregory Gavin says he's had a lifelong preoccupation with creeks, starting more than five decades ago when he was a young Woodside Elementary School student who sometimes wended his way home from school along Bear Gulch Creek, which runs behind the campus.
"When I was really little, I spent a lot of time in the creek," which ran from the school to near his home on Mountain Home Road, he says.
Now, the 57-year-old with a master's of fine arts degree makes his living playing with water.
Mr. Gavin's Riveropolis business melds his fascination for creeks with other of his interests — art, architecture, teaching, children, carpentry, community and bringing disparate people together to work on joint projects.
For two decades, Riveropolis has been bringing portable water features to museums, street fairs, schools, parks and storefronts. The rivers are art, but not the type viewed from afar. Instead, Mr. Gavin's rivers are completed and modified by audience members, children and adults who build boats and buildings, landscape river banks and even change the course of the river, quite often getting wet in the process.
The collaborate process often brings together people who normally wouldn't interact. It reminds Mr. Gavin, he says, of the "metaphor of water being the universal solvent."
The rivers are also a teaching tool. The rocks that go into them offer geology lessons, while boat-making provides teaching about design and buoyancy. The running water in the rivers offers lessons about the water cycle as well as engineering and hydrology.
It seems somewhat inevitable that Mr. Gavin and one of his rivers would find themselves back where he started, set up in a playground just a few hundred yards from the creek that originally inspired him at Woodside Elementary School.
Mr. Gavin spent nine years at Woodside Elementary; his mother, Carolyn Gavin, taught there for 30 years. His mom still lives in Woodside with his dad, Michael, although they've moved from the house next to the creek.
But Jen Upson, the Woodside Elementary parent who conceived of asking Mr. Gavin to spend a week on the pre-kindergarten to eighth-grade campus, says she had no idea about his connection to the school when she arranged his visit.
Taking a break between classes during his recent visit to Woodside, Mr. Gavin talked about some of his other inspirations for Riveropolis. One was watching a nephew who had been diagnosed with attention deficit hyperactivity disorder spend two hours happily playing in a very cold Sierra Nevada creek.
Another was the first river he built, a 100-foot long structure he made with the residents of San Francisco's Portola neighborhood, in a storefront studio he was about to be forced out of.
He builds the underlying structure of the rivers himself, starting with a model and then building full-sized wood forms and finally the fiberglass structures that are filled with water. He's currently working on an ocean.
Mr. Gavin has set up his rivers in places as diverse as the DeYoung Museum, several makers' fairs, the Bayview Opera House, and Chevron corporate offices in San Ramon. He says he uses gigs that pay full price to subsidize those in less-affluent neighborhoods, such as the North Oakland neighborhood where he now has his studio.
In summers he does more extensive camps where, he says, kids "build whole worlds" on the banks of the rivers.
After Woodside Elementary, Mr. Gavin attended Ravenswood High School, helping to co-author a book about it in the year before it closed. He attended architecture school at the University of California, Berkeley, leaving when he received a fellowship to hitchhike across North America to study the architecture of rural communities.
After spending years visiting communities ranging from an organic farm in Oregon to a Trappist monastery in Massachusetts, he set off on the R.V. Heraclitus, a ship designed to travel up tropical rivers and conduct ethnobotany.
The ship, he says on his website, turned out to be "more a cult than a scientific expedition," and he ended up jumping ship in the Marquesas Islands.
Instead of going back to Berkeley to finish the architecture program, he went to San Francisco State University to study film and video. He later received a master's of fine arts degree from the California College of the Arts.
Before starting Riveropolis, Mr. Gavin did a series of installations, public art projects and artist residencies in San Francisco, Oakland, San Rafael, Boston and Las Vegas.
He often worked with children. Before starting Riveropolis he taught children to use tools and a wide array of materials to build their own full-sized working soap box race cars, in a project he called Will Power Motors.
As part of that project, he made a movie, "Bernaltown," starring some of the soap box race cars and the residents of San Francisco's Bernal Heights neighborhood. In a 1997 story about the movie and Mr. Gavin, the San Francisco Chronicle called the movie "a charming neighborhood fable."
He's brought his river to Woodside Elementary for two years, Ms. Upson says, and will probably be back next year.
" It is a huge hit with the students and the teachers," she says.
• Watch "Bernaltown" on YouTube. (And if you happened to have Carolyn Gavin for a teacher, look for her short speaking part in the movie.)