Sunday, March 22, 2009

Tres Aliances Axle Canyon Restoration

From Axel Canyon

From Axel Canyon

From Axel Canyon

From Axel Canyon

From Axel Canyon
They may look like a booby-trap... but those are "vanes", a standard restoration technique by the "induced meandering" school of restorationists. Some restorationists hold to the line that we should just "plant the heck out of denuded riparian areas" and let the stream do as it will, whereas the induced meandering school tries to engineer a solution that takes into account and is inspired by natural processes, and then let natural recruitment restore riparian vegetation. Both schools have something to offer, and both have their drawbacks.

Yes, the vanes are built in the stream bed. The pits were dug with a backhoe and the juniper posts are a by-product of local thinning work. The line of posts are positioned at a 20 degree angle from the banks, jutting upstream. Previous projects have placed them at a 30 degree angle from the bank (ie jutting further out) and positioned further apart, with sometimes disastrous results. The inspiration for the sometimes counter-intuitional placing is that natural downed logs or rock slides tend to persist when they are at that angle, because they can withstand the impact of water flow, while still slowing it and protecting the banks. As water slows down, it deposits sediment, creating natural sand bars. Eventually the posts will disappear and disintegrate, having done their job. The danger is that the water can cut behind the vanes, as happened last summer on our Santa Fe river project. The problem with simply armoring the banks is that boulders or poles can set up "secondary cell vortexes" in the water's flow which can cause the stream to erode its banks.

From Axel Canyon

You can see more photos of Axle Canyon here:

Tuesday, March 10, 2009

Sonoran Desert Maps

Goat Springs: Dry

Browsed mormon tea (ephedra sp) and yucca... we followed cattle and game trails (deer, elk, cow, rabbit feces) through the sandy soils, along washes in the hills, clambered over the spine, up many false leads, looking for the springs.

Bug skewered on cholla. There is one species of cholla, one of prickly pear, and one Echinocereus present in the uplands.
The yucca in this area is heavily browsed. I initially suspected overgrazing pressure from cows or game, but later found yucca leaves in a packrat midden. As Alexandra says, "there are rodents, everywhere." Yucca grows thickly in other nearby pastures, possibly as a result of previous grazing management, because in still other pastures there is thick cholla, or thick juniper.

The grama grass grows in "islands" rather than "networks" over much of this range. There are deep furrows/headcuts leading up from the washes, indicating extensive erosion. While Goat Springs is in a natural hard-rock canyon, there are numerous abnormal, unnatural looking trench arroyos in the area. Rocky soils dominate in the uplands, while a large amount of eolian deposits have accumulated at the base of these hills.

As we approached the true springs we knew we were on the right track, first by the abundant PVC detritus, then by a few dying cottonwood, then a thicket, and, finally, a fenced-off area. The "springs" were marked by extensive rock work, both loose and concreted. The PVC piping led to a stock tank. The "springs" themselves were ineffectually fenced. The only interesting species was some Setaria, probably leucopila, growing in the rocks.

While exploring the headwaters above Goat Springs, we discovered an ancient, destroyed, forest. There is nothing like these trees, which may have been old-growth Pinon or Ponderosa, in the area. Above the springs the shrubs are Mountain Mahogony, whereas below the springs the shrubs are all Apache Plume.