Atturbury Wash in Lincoln Regional Park is extraordinary because it has a wide floodplain filled with dense riparian vegetation. This vegetation (netleaf hackberry, mesquite, blue palo verde, desert hackberry, graythorn, condalia, etc.) is kept alive exclusively by rainwater and stormwater (groundwater is too deep here for roots to reach it). Stormwater flows occur mostly during heavy summer thundershowers. Historically, they would have spilled out of the shallow wash bed and spread across the floodplain, flowing slowly and infiltrating into the ground. Erosion problems have resulted in deepening of the main wash channel (incision) and capture of much of the stormwater that flowed across the floodplain. Most of the stormwaters now flow fast and deep, leaving the site quickly. This has resulted in die-off of some of the vegetation.
Our grant for Atturbury Wash has allowed us to hire contractors to build one-rock dams and other structures based on the rubric of "natural channel design." Contractors were Dryland Solutions (out of Santa Fe), Natural Channel Design (Flagstaff), Lil' John's Excavating (Tucson), and Ethos Rainwater Harvesting and Erosion Control (Tucson). The structures were placed in the wash and in the wash's floodplain, both in the lower part of the golf course reach and in the Atturbury-Lyman Bird and Animal Sanctuary.
The Natural Channel Design work accomplishes three things. The larger one-rock dams in the main wash act as grade-control structures, raising the wash bed slightly and stabilizing the level of channel incision. Second, they are placed in areas experiencing bank erosion, moving water away from stream banks. Third, they tend to push floodwaters onto the floodplain and prevent it from flowing back into the main wash channel, increasing the infiltration of water into the ground.
A key to this process has been working closely with Tucson Parks and Recreation, which manages Lincoln Park, and the Tucson Golf Program. We also work closely with the Groves-Lincoln Park Neighborhood Association, which for decades has worked to preserve the natural open space in Lincoln Park. We thank them, and of course the funders, the Arizona Water Protection Fund Commission.
Our grant pays for public outreach regarding the importance of riparian habitat and healthy floodplain function. One of our key messages to the public is that natural open space in our city and county parks should not be seen as an "unused" portion of the park; the future site of a ball field or recreation center. That natural open space is a recreation area for bird watchers, hikers, dog walkers and many others. It is habitat for a wide variety of creatures—birds and more—that "wildlife watchers" enjoy seeing. Wildlife watching is a major source of income in Arizona, with an annual $1.5 billion "total economic impact."
Look in Tucson Audubon's calendars for site tours, birding field trips, volunteer work days and other opportunities to visit the project site and learn more.
For information about opportunities to visit restoration sites, call Kendall Kroesen at (520) 629-0510 x7006 or (520) 971-2385 (cell).