Watching Daryl Hannah pack up climbing equipment -- including funnels that enable tree-sitters to pee into bottles when aloft -- is not the way that most men fantasize about meeting the star of Splash. Yet on the night of Jan. 11, 2011, sitting in his living room, Stone was doing just that. "It was surreal," he said. He was sleepless. Desolation vied with panic. Emails from the campaigners he'd roused flashed across his computer. Every legal option to save the oaks had run out. Then Hannah came to Arcadia to support Stone's cause, along with California's most famous tree-sitter, John Quigley.

Hannah and Quigley were experienced tree-sitters. In 2004, it took officials two and a half months to pry Quigley out of a 400-year-old oak targeted by a road-widening project in north Los Angeles County. Both activists made headlines in 2006, occupying an old almond tree in a South Los Angeles community garden that had been condemned. Climbing with Quigley would be three recruits, Julia Jaye Posin, Travis Jochimsen and Andrea Bowers. Hannah would protest from the gate.

They slipped onto the Flood Control site under cover of darkness. Months later, recounting the events of Jan. 12, Bowers described the depth and softness of the leaf litter beneath her feet as she hoisted herself into an oak. "I had thought of a lot of scenarios of what might happen," she continued, "but them leaving us in those trees and tearing down the trees all around us with big quad bulldozers wasn't one of them." That is exactly what happened, however, when Flood Control workers moved in at daybreak. "The guy operating the machine took the wrong angle on a sycamore tree," said Quigley. "As the tree started to buckle, it was buckling into us." Yelling, he scrambled to the top of their oak to signal hovering news choppers. "Finally, the guy suddenly understood that he was about to kill us, so he backed off."

The woodland's wildlife received no such reprieve. While Flood Control made good on a promise to have a biologist present for the razing, none of the elaborate plans in the environmental impact report to conduct preliminary wildlife evacuation or fencing had been carried out. "There was tons of stuff running up and down the tree," Bowers said. Squirrels leapt from boughs. Clouds of chittering bushtits moved from tree to tree. Sun-blinded bats circled among crashing boughs. By dusk, their roosts were gone. A Search and Rescue team in a cherry-picker removed the tree sitters, who were promptly arrested. As the felled oaks began disappearing into chippers, the tree-sitters were hauled off to jail.

After being charged with criminal trespassing, the "Arcadia Four" were released on bail. Two weeks later, Public Works sent a letter to the county sheriff's office demanding $2,639.69 from the tree-sitters to cover the cost of staff needed to "ensure safety for tree activists and possibly other activists who may have been hiding in the bushes."

Camron Stone didn't hide in the bushes. He didn't go down to the wash at all that day. "I couldn't stand it," he said. Only that evening did he venture out to the locked gate near Highland Oaks Drive. There, he took part in a candlelight vigil.

Where, you might ask at this juncture, were the firebrands whose activism supposedly put California at the vanguard of environmentalism? The short answer is: ignored, unaware, dead or co-opted by Flood Control's parent agency, the Los Angeles County Department of Public Works. The region's leading watershed warrior, Dorothy Green, had lost a long battle with cancer in 2008. While the U.S. Geological Survey warned of the potential for catastrophic mudslides after a massive wildfire swept through the Angeles National Forest in 2009, exceptionally mild rains that winter failed to produce them. Complacency had set in. The more Flood Control actually controlled floods, the less people thought about it.

As for the threat posed by Flood Control's tendency to see woodlands as a dumping grounds for sediment, a local pillar of the Audubon Society, Mike San Miguel, had begun to take on the Santa Anita oaks battle when he died in an accident in the summer of 2010. His colleagues didn't learn about the proposed dumping until it was too late, said Pasadena Audubon's Laura Garrett.

If the coalition of county-funded arborists then at work on the first Oak Woodlands Conservation Management Plan knew about the dumping plans, it was largely mute until a few members eventually joined Camron Stone's ranks. The single organization whose purview most squarely included dams and rivers was the Los Angeles & San Gabriel Rivers Watershed Council, recently re-branded as the Council for Watershed Health. It had been aware of the backlog of debris and the quandary about where to put it, confirmed its executive director, Nancy Steele, in early January 2011. But her hands were tied when it came to protesting. The watershed council's mission was "strictly scientific," she said. Critics also noted that its board of directors included some representatives of local water companies and the county Department of Public Works, all of whom were pressing for fast dam cleanouts.

So it took building contractor Camron Stone to sound the alarm for what sediment dumping was doing to the Los Angeles foothills. To stop more bulldozers, Stone and his allies created the "Urbanwild Network." Their strategy was simple: Everywhere Flood Control went, they would go, too. "They took something away from me that was very precious," Stone said. "That got me really angry. My goal is to change the culture at the Department of Public Works."

In one early victory, in February 2011, Urbanwilders forced Flood Control engineers into a new two-year environmental review for one dam cleanout, on the grounds that willows sprouting from the sediment choking Pasadena's Devil's Gate Dam provided waterfowl habitat.

By April, freshly radicalized and newly media-savvy, Stone was giving an interview to the Pasadena Star News with Quigley, Hannah and actor-activist Ed Begley Jr., arguing that "local people do care about the wildlands in their back yards that are disappearing at an incredible rate." The next oak woodland in the path of Flood Control's bulldozers lay west of Arcadia in La Tuna Canyon, west of where the San Gabriel Valley gives way to the San Fernando Valley.

Asked for an impartial assessment of what was at risk, Bart O'Brien, a Southern California native plant expert, led a tour through La Tuna Canyon in June 2011. Just 500 yards into the sheltered lowlands, in the midst of reeling off plant names, O'Brien nearly shrieked. "A Humboldt lily! We've gone hardly anywhere, and we're finding this plant that many people take ages to find." As O'Brien sees it, it's essential to preserve these riparian, low-lying oak woodlands, not only for their biodiversity and value as wildlife habitat, but because of the unique adaptations made by the plants that live in them. "When you think about gene pools, if you take out all the plants on flat lands, what do you think you've done?" he asked.

Throughout 2011, faced with a groundswell of protest driven by Stone, the Los Angeles County Supervisors organized yet more outreach from Flood Control. Anyone interested was invited to come to its headquarters south of Pasadena for meetings of the Sediment Management Strategic Plan Task Force. The agency had already had sediment-control plans under way, said Flood Control spokesman Bob Spencer, but for the engineers involved, these politically mandated open sessions were as welcome as the prospect of finding women at the urinal in a Suffragette-era saloon. Outrage over the loss of the Arcadia woodland ran so high at the first meeting in January that by the second one in April, chastened Flood Control officials announced that they had taken La Tuna Canyon's oaks off the list for immediate demolition.

Yet as the meetings progressed, even oak lovers began to understand the problems involved in disposing of the sediment stacked up in Flood Control's network of dams and debris basins. Most had read John McPhee's writings about Southern California's fire and mudslide cycle. The new wrinkle was that until Aug. 26, 2009, when an arsonist in the San Gabriel foothills started what became the biggest wildfire in Los Angeles history, nobody had thought of mud in quite such vast and dangerous quantities. After the Station Fire left more than 160,000 acres charred, Flood Control Engineer Christopher Stone (no relation to Camron) reckoned that rains would send 20 million cubic yards of sediment downhill. As Flood Control translates it for laymen, that's the amount of space it would take to stack 20 million washing machines. McPhee never put the sheer load of mountain debris building up around the basin in terms quite so comprehensible to the average homeowner. Yet citizens at the Flood Control sediment management meetings were full of ideas. Truck it to the beach! Use it as landfill cover! Dump it in retired mining pits! Sell it as decomposed granite to landscaping companies!