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.
Details:
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.
You can see more photos of Axle Canyon here: http://picasaweb.google.com/conorpro/AxleCanyon#
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