Trump's Border Wall Would Be the World's Longest Concrete Dam

California's border with Baja California is a complex region with unique environmental issues. Our Borderlands series takes a deeper look at this region unified by shared landscapes and friendship, and divided by international politics.

As it becomes seemingly inevitable that Donald Trump will be the Republican Party’s candidate in the 2016 Presidential race, it’s a fitting time to take a look at he environmental effects of his signature campaign proposal — building a massive wall to seal off the U.S. border with Mexico.

As we saw in the first article in this series, building a concrete wall to Trump’s vague, hand-wavy specifications would dump a massive amount of greenhouse gases into the atmosphere. But that’s not the only way Trump’s border wall would wreak weather-related havoc. Building the wall would also heighten the danger from existing weather. Simply put, a solid concrete wall would cause catastrophic flooding in the desert. And to explain how, there’s no better place to start than the border community of Lukeville, Arizona.

Lukeville isn’t much more than a wide spot in the road at the south end of Arizona State Route 85, best known to Arizonans as the road between Gila Bend and the Sonoran beach town of Puerto Peñasco. Lukeville’s population tops out at about 30 year-round residents. That can more than quadruple during the tourist season when Gringo Pass’s trailer campground fills up with tourists visiting Organ Pipe Cactus National Monument, which surrounds Lukeville on three sides.

On the fourth side, southwest across the border, lies the town of Sonoyta, Sonora, home to about 18,000 people. East of Organ Pipe is the Tohono O’odham nation’s 4,400-square-mile reservation, and westward lies the Cabeza Prieta National Wildlife Refuge, 1,344 square miles of some of the most rugged desert to be found in the Lower 48.

The Southwest’s deserts are home to some of the most unpredictable flooding on the planet, and Arizona’s borderlands are no exception. Some floods happen during the days-long winter storms that soak the desert in El Niño years. But the most violent floods come in the summer monsoon season, when superheated air rises from the desert, drawing in moisture from the nearby Sea of Cortez.

The monsoon storms that result can be highly localized and hard to anticipate. On one triple-digit temperature day in July, 2006 I was walking the long, cactus-studded Sonoyta Plain south of Organ Pipe’s Kris Eggle Visitor Center, trying for some good photos of the Monument’s eponymous column cacti. Off toward the border, I watched a storm cell develop and darken, the ground beneath it suddenly obscured by a column of heavy rain. Within four minutes the storm front had reached me. I was startled by its violence, rain and hail pelting my exposed skin painfully. Then the lightning started to strike, several bolts in a few seconds a few hundred feet away from me, and I sprinted the mile back to my pickup truck. By the time I caught my breath, the storm had passed.

Such storms can dump an inch of rain in just a few minutes. Two- or three-inch rainstorms spanning just an hour and fifteen minutes aren’t at all uncommon in monsoon season.  They fall on land that may not have seen a drop of rain in months or years. The desert’s mineral soils can only absorb so much water at a time. The rest runs off, one tributary after another filling the main washes, filling them. The resulting flash floods can scour trees out of the earth. They gather up three, four years’ worth of accumulated leaves and branches; the skeletons of cholla cacti and coyotes, plastic bags and beer cans, driftwood the size of fireplace logs, driftwood the size of railroad ties. All of it goes downstream in an advancing front that is as much debris flow as watercourse.

Whether such a flood constitutes a disaster or a boon depends on how you work with the desert landscape. Farmers of the Tohono O’odham traditionally follow the floods, choosing recently flooded washes and arroyos as that season’s field. They plant crops in the newly fertilized soil, often tepary beans, a drought-tolerant native legume. O’odham farmers using this method don’t force the water to come to them: they see where the water chooses to go and follow it. I write in the present tense, not the past: there are still O’odham farmers who plant this way, though it’s harder nowadays to find access to appropriate washes. There’s a wisdom in yielding to the demands of nature rather than demanding nature bend to human whims. And beans grown this way seem to be more nutritious than those grown on conventional farms. 

But the same floods that offer deep watering and organic matter to traditional O'odham fields can serve as battering rams if anyone is lacking enough in that traditional wisdom that they try to put rigid structures in the course of the flood.

The best defense isn’t always a fence

There hasn’t always been a lot of development near Lukeville, at least on the U.S. side of the line. Until the 1990s, the whole area north of the border — especially the Cabeza Prieta — was considered a desert naturalist’s paradise, a beautiful and dangerous landscape that could kill you as easily as it could inspire you. Author Ed Abbey referred to Cabeza Prieta in particular as the “best desert wilderness left in the United States." Outside of Sonoyta and its outlying communities, the desert south of the border was even wilder, with the Pinacate Mountains usually considered the wilderness crown jewel of North American deserts.

But when the U.S. government launched Operation Hold the Line in El Paso in 1993, and Operation Gatekeeper in San Diego in 1994, the landscape on both sides of the border changed quickly. The easiest border crossings at San Diego and El Paso were fortified, while the vast desert interior of Sonora and Arizona were left essentially unguarded.

Before 1994, an open border in the Arizona desert was widely considered a feature rather than a bug. The Tohono O’odham people’s traditional lands straddled both sides of the border, which had only been delineated in 1853. O’odham farmers would sleep in houses north of the border, then wake up in the morning and head out to tend floodwater-irrigated fields of tepary beans across the line in Mexico. Or the other way around. For the O’odham, the border is a recent intrusion on a landscape they’ve inhabited for millennia.

In 1992 I visited the oasis of Quitobaquito, a wildlife-rich spring perhaps 150 feet from the Mexican border in the western edges of Organ Pipe. There was a border fence back then; two strands of barbed wire primarily intended to keep Mexican cattle from muddying up the oasis. Kids from the Mexican hamlet of Papalote a half mile down the road had put old carpet over the lower strand for easier access to their local swimming hole.

But when Operation Gatekeeper and its kin started deterring would-be migrants away from crossing at border cities, the Arizona desert’s relatively undefended border beckoned. Within a few years, illegal vehicle traffic started carving hundreds of miles of unauthorized roads through Ed Abbey’s last best desert wilderness. Some of those vehicles carried contraband to feed America’s insatiable appetite for drugs. Some carried migrants, hidden away in cramped and dangerous secret compartments like so many bales of weed.

People crossed on foot, too, to their own immense peril. It’s one thing to hop a barbed wire fence during a 118°F summer afternoon to grab an unauthorized swim in a protected wildlife area. It’s another to pass that oasis and keep going across 60 miles of forbidding, fatal desert.

Within a few months after Operation Gatekeeper went into effect, the daily life of law enforcement rangers at Organ Pipe changed a great deal. Before, the job had usually consisted of a fair amount of search and rescue of befuddled tourists, ticketing speeders on AZ 85, and occasional paramedic work and firefighting. Suddenly, Organ Pipe’s rangers were up against the cartels and the coyotes, who thought nothing of driving at high speeds through wilderness areas with illegal cargoes, armed with automatic weapons.

In August 2002, a pair of alleged cartel gunmen drove off-road across the border into Organ Pipe after escaping from Mexican authorities in Sonoyta. Mexican authorities alerted the Border Patrol, which called on National Park Service law enforcement rangers for aid. The pair were apprehended, and one gave himself up without a struggle, but the other grabbed an AK-47 and opened fire, then headed back across the border. A round from the AK-47 hit Organ Pipe’s law enforcement ranger Kris Eggle beneath his vest. Eggle died of blood loss before a medevac helicopter was able to arrive.

Within months — a lightning-fast response for a federal agency — the National Park Service began planning a vehicle barrier along the National Monument’s southern boundary to help prevent similar incursions. Construction started in 2004. The barrier was finished by July 2006, the month I dodged thunderbolts on the Sonoyta Plain. (I was in Organ Pipe to do research for an article I was writing on the environmental impacts of border crossing.) While the vehicle barrier itself was fairly minimal as an international border fence — vertical steel posts set about five feet apart, with a heavy horizontal crossbar three feet off the ground, with plenty of room for pedestrians (and, importantly, wildlife) to slip past without much inconvenience — a new environmental threat caused by the barrier was making itself evident.

Not so much a fence as a dam

What was that threat? Kathy Billings, who served as Superintendent of Organ Pipe National Monument in 1996, told me that summer that she was worried about the barrier’s effects on local watersheds, and even more worried about plans for a wall already being floated at the time.

"It's not that the vehicle barrier doesn't have its environmental effects," Billings told me.

“Diverting water flow” is a bit of an understatement. If the sparse obstruction of the Monument’s new vehicle barrier was likely to create problems when the washes the barrier crossed were in flood, it’s hard to escape the conclusion that a fence or a solid wall would prove disastrous.

That may seem counterintuitive. Aim a garden hose at the kind of fence Homeland Security was talking about and most of the water would get through, though there’d be a lot of splatter. A slow trickle of water, even a few gallons per minute, might seep through a fence without any trouble at all.

But desert flash floods can be far more than trickles. Floods carrying up to 1,000 cubic feet of water per second happen at regular intervals, and they carry enough muddy debris in their fronts that a regular chain link fence in the flood’s path will soon become something closer to a stucco wall.

As it turns out, Billings’ concerns were prescient. In September 2006 — two months after my visit to Organ Pipe — first the House of Representatives and then the Senate passed Representative Peter King’s Secure Fence Act of 2006, which required 700 miles of pedestrian exclusion fencing be built along the border. President George W. Bush signed the bill into law the following month. Two years later, the Consolidated Appropriations Act of 2008 required the Department of Homeland Security to finish 300 miles of that fencing by the end of that year.

By early 2008, Homeland Security had installed just under six miles of pedestrian fencing along the border near Lukeville, to ensure that migrants seeking to enter the U.S. from Sonoyta without permission had to traverse miles of unforgiving desert rather than skirting AZ 85 toward Ajo and civilization. Mindful of the threat from flash flooding, the fence was designed with wide-meshed iron grates along its bottom where it crossed washes, with 6- by-24-inch slots designed to allow water to pass more readily than the tight mesh making up the rest of the fence. During the project’s cursory environmental review, National Park Service scientists expressed concern that the grating wasn’t sufficient to prevent flooding problems. The Department of Homeland Security decided otherwise and built the fence.

On July 12 of that year, in a week in which nighttime low temperatures in Lukeville never dropped below 85°F, a series of powerful afternoon storm cells dumped two inches of rain in an hour and a half on Headquarters Wash right about where I’d dodged lightning bolts two years prior. All that two inches ran off downhill, across the Sonoyta Plain toward the border, filling Headquarters Wash and its tributaries.

When the flood reached the Homeland Security fence near Lukeville, that flood grating quickly proved not to work as well as its designers intended. Flood-borne debris instead plastered itself up against the base of the fence, forcing floodwaters up and over the inadvertent plug. On the downstream side of the fence, a cascade of water flowed over the debris, washing away the soil at fence’s base. Locals said the fence “acted like a dam,” backing up water as much as seven feet in some places along the fence near Lukeville.

The flood did significant damage to the Gringo Pass store, filling the entire building with water and debris. The owners eventually sued the federal government for $6 million to cover damages. The Lukeville Port of Entry on the border, and its Mexican counterpart in Sonoyta, also sustained heavy damage.

The Lukeville flood wasn’t the worst to hit Arizona that day. A storm from the same system dumped a similar amount of water on the border city of Nogales, Sonora, about 150 miles east of Lukeville. That city had been protected from flooding by a 20-foot wide drainage tunnel built in the 1930s. In February 2008, acting on reports that the tunnel was being used by migrants crossing into the U.S., the Border Patrol had built a barrier in the tunnel. Later analysis found that the barrier cut the capacity of the drainage tunnel by 40 percent; when the flood hit the barrier, it backed up, collapsing the tunnel and directing floodwaters into downtown Nogales. Two drowning victims were later found in Nogales Wash: it’s thought they may have been would-be migrants caught in the tunnel by the floodwaters. The Border Patrol didn’t consult with international environmental and public works agencies before installing the barrier, and in fact notified no one of the addition to the tunnel.

After the July 2008 floods in southern Arizona, the Army Corps of Engineers hired the contracting firm Michael Baker Jr., Inc. to assess possible threat from desert washes crossing the 600-odd miles of both border pedestrian fencing and vehicle barrier built under the Secure Fence Act and related programs. Baker’s report, provided in May 2009, was sobering.

In the area surveyed between San Diego and El Paso, Baker counted 27 washes that were capable of carrying flash floods like Lukeville 2008 or larger, which required radical redesign of the border barriers that crossed them. Another 135 washes were almost as threatening, but Baker assessed them as posing a manageable flood risk if the Border Patrol was diligent in clearing brush and debris away from the fence. (If you're wondering who the Border Patrol would hire to do that brush hauling, you're probably not alone.)

What redesigns did Baker suggest? Mainly that the sections of fence crossing washes prone to flood be replaced with gates that would be lifted or removed during monsoon season, or in advance of storms. In other words, make the fence less of a fence; make it more porous and permeable — and not coincidentally, less effective at keeping people from crossing the border.

In 2010 the Army Corps of Engineers installed 10 such liftable gates near Lukeville as a pilot project. When monsoon season came along in 2011, someone apparently forgot to lift them. On August 7, a monsoonal storm dumped up to two inches of rain in the Ajo Mountains just northeast of Lukeville. The resulting flash flood tore out 40 feet of fence.

Problems with flooding caused by the border fence obstructing flash flood flows aren’t limited to southern Arizona and northern Sonora. Flooding is a threat anywhere the border crosses a wash or river prone to fluctuation, from the Tijuana River to the Rio Grande.

And that’s the fence that Donald Trump would replace with a solid wall, taking the few slight advantages of a metal fence — limited porousness to small flows of water, flexibility if equipped with movable gates — and replacing them with a 1,954-mile-long concrete dam.

Mesh fences, even those plastered with muddy debris, still allow some water to leak through, and to spill over the top of the debris wall. Imagine a 20-foot, or 30- or 50-foot solid concrete wall in the path of the floods of 2008 or 2011. In Nogales, Sonora, water reached the tops of doorframes near the border while only a few inches ran in the streets in Nogales, Arizona. And that was with 60 percent of that old tunnel’s capacity still working. Put a 30-foot concrete wall along the border, and that water would have risen a lot higher in Nogales, Sonora. It’s likely the death toll would have been far higher.

And with such a wall in place in Lukeville, that settlement would likely have been wiped off the map altogether in 2008 and 2011.

It’s small consolation that such a wall would likely start to fall to erosion and undermining by those very flash floods within a decade or two. If the Tohono O’odham farmers display a distinct wisdom in let the floods flow where they may, and whose habit has been to grow their crops on one side of the border or the other depending on which spot best suited their needs that season, the border wall betrays a distinct lack of that wisdom. Trump’s wall won’t stop migration of people, and in the long run it won’t stop the desert’s floods from flowing.

It’s just a matter of how much damage we’ll cause the desert and ourselves before we realize that.