Due to drought conditions, habitat fragmentation, historic unsustainable grazing and timber harvests, and flooding events, watersheds within the Madrean Archipelago have been severely degraded. Smith Canyon is one such degraded site, located in the Sonoita Creek Watershed and part of the Nogales Ranger District of the Coronado National Forest. In collaboration with entities such as the Arizona Department of Environmental Quality, Arizona Game and Fish Department, United States Fish and Wildlife Service, United States Forest Service, United States Geological Survey, and the University of Arizona Cooperative Extension, Borderlands Restoration Network staff has implemented various watershed restoration techniques across Smith Canyon in an effort to address habitat degradation concerns.
Restoration treatments within Smith Canyon were designed to reduce erosion impacts and nonpoint source pollution downstream, with the overarching goal of improving the overall ecological function of the watershed. Smith Canyon consists of mixed mesquite shrubland and oak grassland across roughly 90 structurally similar sub-basins. The unique, repeated pattern of these ~90 sub-basins presents an exciting opportunity for rigorous, large-scale experimentation when considering each sub-basin as a replicate unit.
In 2018, Roy Petrakis (USGS) developed a model to cluster sub-sets of these sub-basins based on their structural and biophysical traits. BRN staff then assessed each of these clustered sub-basins by level of restoration need (high/medium/low), allowing BRN staff to standardize best management practices across the adjacent Stevens and Little Casa Blanca Canyons for future projects.
Between June 2019 and November 2019, BRN staff installed erosion control structures per the restoration prescription in all of the clustered sub-basins. As an effective and low-cost technique employed around the world for thousands of years, erosion control structures are potent restoration tools in arid regions suffering from ecosystem degradation and the destructive effects of drought, fire and flooding. These structures consist of several parallel rows of self-reinforcing rocks or wood incorporated into the bed of the eroding channel. Often only one-rock high in profile but several rows wide, these structures rest at right angles to the direction of flow but remain passive to overtop flows. This arrangement allows these structures to trap organic-rich sediment upstream, while slowing flows and increasing water infiltration into the channel bottom and banks.
These structures extend the hydro-period for plant establishment without retaining water long term. When placed in a coordinated series according to landforms and observed water flows, each individual erosion control structure is part of a system that decreases erosive forces, increases surface water availability, and aids ecological recovery. Each of the 90 sub-basins received at least five erosion control structures constructed of rock and five erosion control structures constructed of dead and down woody material, depending on local resource ability. After installing the erosion control structures, BRN staff monitored each erosion control structure within the sub-basins for theoretical sediment yield by measuring their basin length, width, and height.
Physical Address: 320-B School Street Patagonia, AZ 85624