It took months to get the besieged Christopher Stone out to the Arcadia dam and sediment site. But in late May 2011, he agreed to tour the newly razed landscape. Up close and in person, the man so vilified that many Urbanwilders spit his name -- "Ssssstone" -- was more like Grandpa Walton than Lord Voldemort, right down to the twinkling blue eyes. After viewing the conveyor belt leading two miles up to the dam, and a number of the dream homes backing onto the site, he dealt with the million-dollar question: Why didn't Flood Control leave room for rivers to carry the sediment where gravity wanted it to go, which was of course, down, across the Los Angeles basin to the Pacific Ocean, where it once fed madly fecund wetlands and beaches?

"We aren't involved in zoning," said the man from the department created precisely to ensure that developers never had to encounter any zoning impediments.

Later on, paused at a turnout in the narrow road tracing the nauseatingly steep slope near the top of the Santa Anita Dam, looking down over the Los Angeles Basin, a floodplain formed by sediment from these very mountains, an awful realization dawned. Ralph Bicker battled to save Arcadia Highlands from truck traffic, but the felling of the Arcadia oaks created space not just for Santa Anita Dam's current load of sediment, but for half a million cubic yards more. The need is so great, Christopher Stone said, that while Flood Control won't be trucking sediment out of Arcadia, it may well end up trucking it in.

Irony, you're a bitch.

In March 2012, after a $125,000 price reduction, 1674 Highland Oaks Drive sold for a million dollars, in spite of the dam cleanout taking place behind it. In April, the 15-month listening marathon forced by Urbanwild's campaign ended. The doors of Public Works were flung open yet again for public review of a 524-page summary of L.A.'s sediment-disposal options. The document reveals that Los Angeles County will need space for up to 67.5 million cubic yards in the next 20 years alone.

Existing facilities have capacity for only 48 million. Some seemingly clever ideas -- trucking sediments to replenish beaches, for example -- were thrown out on the grounds that the 40-mile trip from mountain to shoreline was expensive and profoundly polluting. To judge by the endless pages of decision-making matrices laid out for the many dams and debris basins in need of cleaning, the notion of trucking sediment to retired mining pits has gained credibility. The idea of removing some of the misplaced suburbs and letting sediment flow downhill to its old floodplain did not make any of the short lists.

Lovely La Tuna Canyon is still listed as offering some of the largest potential sediment storage capacity among the foothill sites. Other grounds listed as open for dumping are 11 places in the Angeles National Forest, most near dams built in the 1920s and '30s. Once they fill these, Flood Control may look for more forest canyon sites. T.J. Moon, a fresh-faced engineer available to help members of the public interpret the massive report, seemed genuinely excited that another solution might be found, though. "The system was built 100 years ago and we didn't really think about the environmental end," he said, "but now we are. This was due to public outcry."

Jared Orsi hasn't followed the recent sediment debacle. While dams were no doubt steadily silting up when he published Hazardous Metropolis in 2004, that book ended on a bright note, hinting that portions of the Los Angeles River might be unchannelized enough to sustain parks and wetlands, revitalizing urban corridors. To Orsi, who was interviewed by phone at his office at Colorado State University, the sediment dilemma upriver signals a new era. Popular conviction that engineers can fix anything is clearly on the wane. "What policy-makers need to learn from this episode," he said, "is, it's not just the mountains that are dynamic; society is dynamic too, so we need policy that responds to that variability."

With 10 million people next to a tremendously flammable forest, climate change likely to exacerbate the fire-flood cycle, and a mighty backlog of existing sediment, the 15 months of public meetings have produced no answers, only more questions. Los Angeles has built itself into a corner. "The next step is to look at impacts," said Public Works spokesman Dan Sharp. "It's always a matter of trade-offs."

Camron Stone is no longer optimistic. He has given up on the dream that he can change Flood Control or save further woodlands from being razed for sediment dumps. "There's nothing you can do," he said. "It's a freight train."

Emily Green is an environmental writer based in Los Angeles. She has written for the
Los Angeles Times, The New York Times, the Guardian and UK Independent, and is a former columnist for the New Statesman magazine. Her five-part series on a proposed Las Vegas pipeline from the Great Basin Desert won a 2009 Associated Press Managing Editors Award. She blogs about Western water at chanceofrain.com.

This story was made possible with support from the Kenney Brothers Foundation.