Buried in Wildfire Ash, a N.M. Monument Awakens to New Threat: Flash Floods

Buried in Wildfire Ash, a N.M. Monument Awakens to New Threat: Flash Floods

05 August 2011

published by www.nytimes.com

USA — Thousands of years ago, however, it was mighty enough to carve a canyon through 400 feet of compressed volcanic ash, and its clear waters enticed a good-sized Ancient Puebloan community to settle along its banks about 850 years ago.

But on a blazing summer morning this week, Frijoles Creek merely trickled past the village ruins and the Bandelier National Monument Visitor Center, slowly making its way to the Rio Grande.

Yet if the annual summer rains finally arrive in force, said Rod Torrez, chief of interpretation for the monument, the creek will become a raging torrent of water, ash and debris, swelled by runoff from denuded forest slopes upstream that were scorched by the recent Las Conchas fire, the biggest blaze in New Mexico’s history.

Yesterday morning, the creek was already opaque with bits of ash washed away by sporadic light rains.

“I’m pretty sure we’ll get a flood; it’s just a matter of when,” Torrez said, walking along the main path on the canyon bottom, which remains closed to the public.

The visitor center, built by the Civilian Conservation Corps in the 1930s and renovated just last year, stood at the ready. Buttressed by more than 10,000 sandbags, the stone building looks more like a fortress than a place of welcome.

Behind its sealed entrance, the visitor center and museum was virtually empty, its native artifacts and rare artwork shipped off to a Park Service storage facility in Arizona back in late June, when the fire first began a few miles northwest of here.

Within hours, Torrez’s prediction had come true. Rain and hail pummeled the Jemez Mountains, and snakes of black, viscous water quickly formed rivulets across the forest floor and clogged streams and roadways south of Los Alamos with rock and woody debris. It was one of the biggest rainstorms to hit the area so far this summer.

The Las Conchas blaze, which reached almost 157,00 acres and toasted parts of Bandelier and the Valles Caldera National Preserve but only skirted the edge of nearby Los Alamos, scorched about 20,800 acres — 62 percent — of the monument.

About 10,000 acres burned severely enough to blacken or consume almost all vegetation and sear the soil enough to hinder its ability to absorb rainfall.

About 1,200 of the monument’s 3,000 archaeological sites also burned, likely damaging masonry and pottery in some areas, and one ranger cabin was lost to the blaze, said Jason Lott, the park’s superintendent.

The fire spared the visitor center and the ancient village thanks to a successful fire line cut by firefighters about 2 miles up the canyon. But high waters could cause severe erosion and flooding, potentially waterlogging the visitor center and wiping out trails. The sandbags are stacked high and deep enough to protect the building against a 5,000- to 6,000-cubic-feet-per-second flood, but no one knows for sure if the reinforcements will work, Torrez said.

“We have no idea how much water there will be, and things like that are hard to control,” Torrez said, standing on the edge of the creek where park officials have removed a concrete vehicle bridge out of concern that it could be ripped from its moors and jam up the creek bed, acting as a dam.

The ruins, however, are at little risk of flooding. That’s because the Ancient Puebloans who built them were careful to site their village just above the flood plain, Torrez said.

“They knew exactly where to build, unlike us,” he said yesterday morning, standing next to a large kiva, a round, partially underground ceremonial chamber that sits several hundred feet upslope from the creek, near the village’s 200 or so rooms.

Regardless of how much rain the area receives this monsoon season, the canyon bottom — the monument’s most popular area — cannot fully reopen for at least a year, Lott said. But he is determined to let visitors back in as soon as possible, most likely through small, guided tours, he said. The visitor center will remain shuttered until it’s safe to bring back the museum’s artifacts, Lott said.

But reopening the area on a limited basis will also provide a good opportunity to educate visitors about the role of fire in the ecosystem, as well as the importance of using prescribed burns to clear out brush and small trees and help keep wildfires from growing into large, super-hot blazes like the Las Conchas conflagration, he said. Thick growth from many decades of snuffing out natural fires provided ample fuel for the Las Conchas blaze, he added. But a prescribed fire in the monument that burned out of control sparked the Cerro Grande fire.

New life emerges

The rains that threaten to erode stream banks and flood the narrow canyons of the Pajarito Plateau are, at the same time, crucial to support the regrowth that is already taking root in the burned soil. That new vegetation, in turn, will help reduce erosion by keeping the soil in place.

“It’s this a Catch-22 — if you don’t get the rain you need, you can’t stabilize the ground, and if you get too much, you get a flood,” Torrez said.

Just a little moisture can go a long way in bringing back vegetation in the dry ponderosa pine forests of the Southwest. On Burnt Mesa, named for the effects of a previous fire in the area, fresh shoots of grass, newly sprouted lupine and 5-inch-high scrub oak saplings have already begun to green up the forest floor.

It remains unclear what effects the fire has had on the monument’s wildlife, but most species should fare fairly well, given that they have evolved with fire, which historically burned through the forest every seven years or so, monument officials say.

On this day, a family of raccoons scurried along Frijoles Creek, and a few miles away on Burnt Mesa, a squirrel rested on a branch in a blackened ponderosa pine. Large ungulates such as deer and elk probably moved outside of the fire zone, and some rodents likely took refuge underground, Lott said.

“I suspect most animals know how to respond to these types of fires,” he said. “They understand the ecosystem probably better than we do.”

But some of the park’s species, like the Mexican spotted owl, may see their habitat completely transformed by the fire and will have to seek out suitable habitat elsewhere, he added.

“When a hot fire comes through and burns all those trees, the ecology changes,” he said. “A new type of growth will come in. So where it might have been a Mexican spotted owl habitat before, it may no longer be suited for them.”

Park officials are completing assessments of the damage to wildlife habitat, archaeological sites and the watershed, he said, adding that the next step is to craft a treatment plan to help heal the damage.

“Bandelier is going to be OK,” Lott said. “In the end, this landscape will recover.”

Valles Caldera recovery

About 10 miles up the road, the Valles Caldera National Preserve, which is mostly composed of grasslands, is already showing signs of a vigorous recovery, said Bob Parmenter, the preserve’s chief scientist.

The Las Conchas fire burned about one-third of the preserve, much of it at low or moderate severity, he said. The new plants growing from the scorched soil are actually higher in nutrients, which in turn will benefit wildlife, he added. “It looks like a golf course,” he said. “Elk, rodents, even grasshoppers are going to love it.”

On the preserve’s forested hills, the situation is more complex. Where the fire burned at moderate intensity, the fire thinned out ponderosa pine stands and left intact a good understory, he said. In high-severity burn areas, however, consisting mostly of mixed conifer and aspen stands, many plants probably did not survive because the heat penetrated deep into the soil, cooking the roots, he added.

The hardy aspen are already showing signs of a comeback, though, Parmenter said. While the above-ground biomass of an aspen tree might have been incinerated, the tree’s extensive underground root system remained alive, shooting up new clones to compensate for the loss. “They thrive on fire,” he said. “They’re growing right back.”

The preserve shares Bandelier National Monument’s concerns about flash flooding. Black water has begun flowing through the preserve’s creeks as well, and the oxygen-depriving muck was responsible for at least one fish kill, in San Antonio Creek, Parmenter said.

But overall, “we fared much better” than Bandelier and the surrounding Santa Fe National Forest, he said.

While the federal preserve was fortunate in that only some areas burned at high intensity — due in large part to cooperative winds — thinning work remains to be done to whittle down forest stands that contain as many as 2,000 trees per acre, he noted. “Our goal in ponderosa pine is to get it back to old growth, with about 40 to 60 trees per acre,” he said.

Under the Jemez Mountains Restoration Project, part of the Forest Service’s Collaborative Forest Landscape Restoration Program, contractors continue restoration work (Land Letter, July 7). Eventually, the preserve hopes to open up the forest enough to allow naturally ignited wildfires to burn, restoring their historic ecological role, Parmenter said.

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