By Monica Nigon
When I first began exploring the idea of using low-tech process-based restoration (LTPBR) structures to assist in restoring a damaged drainage near a popular trailhead in Southwest Colorado where I live, I had no idea how truly beneficial these structures could be. That is, until it started to rain.
My structures of choice were Zeedyk structures, named after the man, Bill Zeedyk, who designed them. In the case of this particular incised channel, I chose Zeedyk structures (usually made predominately of rocks) because the drainage is ephemeral, meaning water only flows through it during high rain or snowmelt events. These structures work like other LTPBR interventions: slow the water down, spread it out, and allow water to reconnect with its historic floodplain.
For my Master of Environmental Management degree, I organized a community-building event in which I led a group of volunteers to build Zeedyk structures to assist in restoring an incised channel near a popular trailhead called Turkey Springs in Pagosa Springs, CO. I chose this site due to the fact that it drains into a reservoir that stores drinking water and that the incising channel was beginning to erode the trail. Likewise, a quick look into the time lapse feature on Google Earth and referencing historic USGS maps showed that the drainage was once a thriving wet meadow. Images from just 15 years ago show a vibrant green expanse; a modern photo shows mostly brown with a deep incision down its middle.
Before installing the Zeedyk structures, I walked the drainage obsessively, learning to “think like water,” as Bill and his collaborators say. I also did my best to identify the plants in the channel and nearby. What I found was concerning: most of the plants I documented, such as the yellow salsify, lewis flax, and musk thistle, are non-native to Southwest Colorado and thrive in dry, heavily-grazed soils.
I hoped that an increase in water storage in the soils at Turkey Springs would encourage the growth of native wet meadow species, such as the corn lily, quaking aspen, and Western blue flag. In my research, I found that the effects of LTPBR on biodiversity are even more broad-ranging. For example, surveyors noted an increase in the population of native cutthroat trout in the Comanche Creek Watershed in northern New Mexico after installing Zeedyk structures. The filtration of sediment and water temperature control offered by the Zeedyk structures allowed the fish to thrive. In Gunnison, habitat for the threatened Gunnison Sage Grouse improved as a result of Zeedyk structures, increasing lek size. Researchers in Colorado, Oregon, and Nevada utilized satellite imagery to monitor vegetative growth across three LTPBR sites in riparian and wet meadow zones, showing a 25% increase in the production of native vegetation which persisted annually.
A recent study out of Utah showed that installing Beaver-Dam-Analogs, another type of LTPBR structure, increased the population of beavers (who took over maintenance and construction of more dams) as well as biodiversity of fish. Deep pools, side channels, and gaps in the dams gave them more space to procreate and allowed more diversity in habitat. One of those pools could accumulate enough organic matter to become fodder for macroinvertebrates, an essential part of the food web of a healthy ecosystem.
Spreading the water in an incised channel out via LTPBR structures turns otherwise dry, degraded channels into wet meadows or wetlands. The water table is subsequently elevated, and riparian zones are restored. The increase in moisture and vegetation provides shade, habitat, and forage for birds, amphibians, insects, and mammals. The increase in moisture in the soil creates a natural haven for wildlife during severe disturbances like droughts and wildfires.
For my project, I recruited friends and strangers to help me, and we ultimately succeeded in building a Zuni Bowl, designed to armor a headcut against further erosion, and a One-Rock-Dam (ORD), a grade control structure, below it. The two structures are usually built in tandem. The enthusiasm of my volunteers was such that the only negative feedback I received about the event was that they would’ve liked to build more structures.
Two weeks after the installation day, on October 11, the remnants of Tropical Storm Priscilla hit Pagosa Springs, turning creeks into torrents and sending the San Juan River over its banks. The river surged to 8,270 cubic-feet-per-second (cfs) overnight. There were two days of reprieve, and then Tropical Storm Raymond visited the area, dropping several more inches of rain in Southwest Colorado, and the river broke another record at 8,560 cfs, becoming the third highest on record and causing more devastating damage due to the already-saturated soils from Priscilla. All told, the two storms dropped 12.5 inches of rain in the region over a span of 5 days, while average precipitation for the entire month of October is normally less than 2 inches.
I anxiously checked on the Zuni Bowl and ORD throughout the flooding, and to my delight, found they were doing exactly what they were supposed to be doing: the water was slowing down, spreading out, and filtering out sediment. I think there could be no better test of a restoration project’s success than a 98-year flood.
The structures had survived and live on to this day. There is momentum to build more Zeedyk structures in the drainage and surrounding area. Last week, I noticed the Zuni Bowl and ORD have filtered out so much sediment that there is vegetation growing in what has been captured. There’s even a Western blue flag.
Monica Nigon is Coordinator with the San Juan Headwaters Forest Health Partnership.
Backyard Biodiversity is a series of educational articles brought to you in partnership with local conservationists, scientists, and biologists and Chama Peak Land Alliance. The series highlights the unique and special nature of our area, in the hope that each of us can and will improve our backyards and communities by ensuring biodiversity.