Floodwaters and erosion have long had their way with the Arroyo Chamiso, carving steep, unstable banks along stretches of the usually dry streambed.
Still, the sandy arroyo, running from the foothills near St. John’s College through south Santa Fe, has remained a popular respite from urban environs for joggers, dog-walkers and the occasional yogi.
But over the past several months, the Arroyo Chamiso has taken on the appearance of a construction site, the streambed compacted under the weight of truck tires and orange fencing stretched across sections where men in hard hats dug trenches, implanted 8-foot juniper posts and stacked gabions of crumbled stone.
Soon, the arroyo will recover its natural appearance — still untamed but a bit more under control.
Work is near completion on a $1.6 million city project to mitigate erosion in the Arroyo Chamiso. City officials and engineers said continued erosion could imperil the paved trail, private property and other structures that abut the arroyo.
Structures installed to slow and redirect floodwaters away from the vulnerable banks incorporated as much natural material as possible to maintain the look and feel of the arroyo, said Melissa McDonald, the city’s river and watershed coordinator. In other words, no concrete was used.
And soon the compacted stretches where work has taken place will be reseeded with riparian grasses and native shrubs to hold the more gently sloping banks. Sediment will cover some parts of the stony gabions after a few rains.
“It’s going to be more park-like than heavily engineered,” McDonald said.
“We are trying to make it a more hospitable place,” she added. “We want the community to use this arroyo and feel like they own this arroyo. Because they do own it.”
In much of the Arroyo Chamiso, the steeply carved banks are almost vertical. Shrubs grow from the side; in some places their roots are visible, exposed as the soft brown sand has fallen or washed away.
To halt those effects and stabilize the arroyo, engineers employed induced meandering, a technique that, in practice, will use structures to coax the rushing water into the middle of the channel, lessening the impact on vulnerable sections of bank, said Eric Cornelius of Santa Fe Engineering Consultants, the project engineer.
The five high-priority Arroyo Chamiso sites selected by the city for the current phase of the erosion-control project called for different induced-meandering measures; in one particularly narrow section, behind the Santa Fe High School campus, a substantial gabion structure was installed to dissipate fast-moving floodwaters.
In the case of a flash flood, Cornelius said, rushing water would now crash into the basin created by the gabion, churning and losing some of its velocity before spilling back over and down the arroyo.
A short distance from the gabion structure, a series of mostly buried 8-foot juniper posts will divert water around soft banks.
Neil Williams, a senior engineer with Biohabitats who with colleague and fluvial geomorphologist Vince Sortman contributed to the project, said this approach is more subtle than typical urban flood engineering.
“You’re not trying to make a perfectly straight channel,” Williams said. “You’re trying to induce a curve on one bank and when you succeed, this big erosive flow of water is deflected back towards the center.”
Another series of posts, or vanes, on the opposite side of the stream would then curve the flow back, Williams said, strategically encouraging a natural, meandering pattern to the water while keeping floods from encroaching on trails.
“It protects [nearby property] while leaving a more natural-appearing channel, which people enjoy,” Williams said.
Although outdoor exercisers and dog-owners frequent the arroyo, recreation in these spaces is generally not recommended, McDonald said, pointing out that nearby paved trails are there for a reason and citing the risk of flash floods at certain times of year.
But “arroyos have historically been corridors for wildlife and people,” said Andy Otto, executive director of the Santa Fe Watershed Association. Otto hopes the improved condition of the arroyos will encourage folks to join the association’s Adopt An Arroyo program and further assist in the upkeep of the popular spaces.
“We’re not trying to pave the arroyos or anything like that,” Otto said. “Instead, we’re trying to improve the experience people have in the arroyos, whatever that might be.”
And McDonald said that while she did not think the city would encourage recreation in the arroyos, the Arroyo Chamiso would still be walkable.
“It’s improved and safer for people, in my opinion,” she said.
Paul Stapleton, a Santa Fe resident, brought his dog Lacey to the Arroyo Chamiso for a fetch Monday.
“This is our dog park, man,” he said. “It’s better than the actual dog park.”
Stapleton said the arroyo-users form a sort of community — passers-by who say hello and come to know each other on the streambed.
Erosion threatens to take away what makes the communal space worth visiting, he said.
“If anything, it helps make it more beautiful,” Stapleton said of the city erosion-control project. “We need that.”
Contact Tripp Stelnicki at 505-428-7626 or firstname.lastname@example.org.