Mud Fight: What We Need to Think About Before We Dig Out Devil's Gate Dam

300 to 400 dump trucks a day. Five days a week. For three years. Assuming a 50-week year, that amounts to 75,000 truckloads. Why are all those diesel-powered vehicles needed over such an extended period of time? That's the amount of machinery and labor, according to a recent LA County's Department of Public Works (DPW) report, that will be required to haul away the 1.5 million cubic yards of debris that has built up behind Devil's Gate Dam, just north of downtown Pasadena.

Much of this astonishing load is a result of post-Station Fire flooding during the winter of 2009-2010, when an estimated 1.5 million cubic yards crashed, banged, and caromed downhill into the sealed-off canyon. Now is the time to dig it out, DPW asserts, an assertion that LA County supervisors have not yet accepted.

Neither have some nearby residents, who are protesting against the noxious fumes and swirling dust that will be kicked up by the massive earth-moving equipment and an endless stream of trucks; they are equally opposed to the destruction of wildlife habitat and recreational space that has built up on that gravely spoil.

Others have challenged the right of DPW to act without assessing the short-and long-term consequences of its actions. As Tim Brick, who directs the Arroyo Seco Foundation, pointed out to the LA Times: "Everybody else has to do environmental impact reports, why shouldn't the county?"

He has a point. So does the Times' editorial rebuttal, which called out the supervisors: "They have received clear warning from the experts in this matter that the current interim measures won't do the job if there is catastrophic runoff. Delay is dangerous, and protecting the communities downstream from the dam must take priority."

Fair enough: the fact of the dam's presence and its centrality to modern life--indeed to the ability to live in this region--cannot be gainsaid. Something has to be done. The central question, however, is not what must be done and when, but on what basis.

I'm not trying to pick nits. But it seems essential--epistemically and ethically--to recognize that the argument that the DPW and the Times have deployed in support of their position depends on a couple of unexamined suppositions.

Begin with that tantalizing "if" in the Times' editorial, as in "if there is catastrophic runoff." Did the newspaper hope we'd miss the huge qualification that it hung on that single word's two slender letters? Did it, and the department for which it is flacking, expect us not to recall that this is the strategy they have always pursued when trying to manipulate flood-control policy and politics? The agency that constructs and manages debris basins and the communal cheerleader of all things constructed--they routinely insist that nature can and must be defied. That human ingenuity and technology can harness the millennia-old processes by which the San Gabriel Mountains have flushed billions of cubic yards of rocky debris into the valley below, forming alluvial fans that are miles wide and upwards of 900 feet deep. We can move mountains.

This very same ambition explains the existence of Devils Gate Dam. Built in 1920, it was designed to defend Pasadena and other communities from thunderous flows of mud, boulders, rocks, and plant material that periodically sluice down the Arroyo Seco. Selecting the structure's site was determined in part by the infamous 1914 flood.

Late that February, after a furious storm, a massive debris slug surged down the high-country watershed, roared through the canyon's narrow "gate," before slamming into Pasadena. It inundated flanking neighborhoods, gouged out chunks of the streetscape, carried away homes, bridges, and buildings, and killed 43 people.

Right then, Pasadena and the county had an opportunity to ask themselves a searching question about how best to live in this place. They might have drawn on the experience of the Tongva and Spanish peoples, who deliberately had not occupied the flood zone, and pulled back. They could have shrugged, accepting that deadly debris flows were part of the price incurred for inhabiting the Arroyo Seco watershed. Instead, they decided to try to minimize those costs by erecting the Devil's Gate Dam. A subsequent flood in 1916 sealed this Devil's Bargain: Pasadena granted the county an easement to build a dam at the gate, and a year later voters passed a controversial bond measure to fund the project; the dam was completed in three years for $483,000 (about $5.3 million in today's dollars).

Once completed, two things happened. The dam did its job and the fact of its success encouraged Pasadena, like a lot of other SoCal towns that in time would clamor for and receive dams, basins, and cribs, to push development into once-unbuildable floodways. The iconic Rose Bowl (1922) could not have been conceived without Devil's Gate, for instance. And the DPW and the Times, with unintended irony, have used its precarious position to press their case for the immediate clearing of debris from behind the dam: within ten minutes of a calamitous flood overtopping the dam, we are assured, the stadium would be awash.

Other post-1920 infrastructure is also identified in the DPW warnings about the consequences of not acting immediately: "many areas near the Arroyo Seco, including homes, horse stables and the 110 Freeway in northeast Los Angeles, South Pasadena and Pasadena are at risk of flooding..."

Nothing about this problematic situation is unique to LA. The earthen and concrete levees systems that line the Mississippi River have allowed developers to build commercial, industrial, and residential nodes in the low-lying sections of Memphis, Vicksburg, and New Orleans--all of which have, or will soon, go under water in the Great Flood of 2011. At roughly the same time that Devil's Gate was constructed, imperiled Gulf Coast cities began throwing up barriers to hurricane-driven storm surges, and then they built right up against these hardened structures on the cheerful assumption that they were now out of harm's way. The same thing happened in flood-prone Phoenix and San Antonio; their respective dams--the Roosevelt and Olmos--encouraged the urbanization of once-dangerous floodbasins.

The result was predictably calamitous. Not all of these structures could withstand nature's fury at every moment, and so each community has felt compelled to add redundant lines of defense to protect its original investment: they thickened and raised levees; boosted the size and strength of seawalls; reconfigured and extended the grid of dams, channels, and diversion ditches. Yet many of these fixes subsequently accelerated the environmental damage and increased costs in a never-ending cycle. Most notorious is below-sea-level New Orleans: it had absorbed billions of dollars before Katrina to shield it from disaster; and exponentially more after it sank beneath the Cat-3 storm's churning fury.

This national pattern of throwing good money after bad raises questions about the second supposition undergirding the argument that DPW and the LA Times are pressing on the county supervisors and the pubic. The newspaper is convinced that the agency alone embodies the requisite expertise to resolve this issue. Any compromise that is not guided by their technocratic insights, the Times warns, will leave the county supervisors "playing roulette with nature." Surely that genuflection to its authority must have cheered DPW, but it ought to leave the rest of us a bit rattled.

After all, many years ago John McPhee warned us about the peculiar consequences that come from accepting at face value the knowledge that experts are said to embody. In The Control of Nature (1989), and particularly its final chapter, "Los Angeles Against the Mountains," he offers a troubling take on the Sisyphusian labor (and endless taxpayer funding) required for Angelenos to reside within the creases and folds of the San Gabriels. No sooner had dams like Devil's Gate been built across canyon mouths, then the county began emplacing other flood- and debris-retention structures into the upper reaches of narrow watersheds. To reach them, they built roads that cut sharply into the loose soil, and behind them came housing developers who paved streets, graded and sliced off hilltops, stair-stepping ever higher into the foothills and canyonlands. This invasive infrastructure has only magnified the volume and rocky rush of debris that, following such conflagrations as the Station Fire, have piled up behind Devil's Gate.

Before firing up the bulldozers, clamshell cranes, and the 10-wheeler dump trucks to dig out and haul off that mass of material, we first must take a step back and admit that the dilemma we face is a dilemma of our own making. It is framed by our touching faith in scientific experts, our heartfelt conviction that an ever-more engineered terrain will solve our environmental conundrums. It has not, and will not.

So confirmed John Tettemer, then acting Chief Deputy Engineer at DPW, in a speech more than twenty years ago. His arresting conclusion could not have been more relevant to our contemporary debate over Devil's Gate: "We should stop building things where they do not belong, and leave a little room for nature."

Char Miller is the Director and W.M. Keck Professor of Environmental Analysis at Pomona College, and editor of the just-published "Cities and Nature in the American West." He comments every Wednesday at 2 p.m. on environmental issues.

The photo of Devil's Gate Dam on this post is by Flickr user T Hoffarth. It was used under a Creative Commons License.