Tuesday, May 21, 2013

Jetty Jacks

I went to the Rio Grande Nature Center State Park in Albuquerque awhile back.

There are jetty jacks there. I like the name. Jetty jacks.

Jetty jacks, Rio Grande Valley State Park, New Mexico

Jetty jacks were big in the 50s and 60s, installed along rivers to:
  1. Prevent floods from deepening a river channel when it scoured the river bed of sedimentation, which over time, resulted in a longer gap between new-normal river levels and the rootline of riverine vegetation, resulting in more difficulty in said vegetation's access to water
  2. Prevent "scouring" of levees or banks, in which flood waters scooped out the bottoms of the banks as they rushed by, resulting in unstable levees or banks
  3. Allow the capture and retention of sediment and flood debris, resulting in the build-up and maintenance of strong banks, resulting in safe environments for trees - bosques - to grow along the river, and preventing the flooding beyond the stronger banks

 Thousands of jetty jacks were installed along the Rio Grande. And, for the most part, they performed as designed. 

Jetty jacks, Rio Grande Valley State Park, New Mexico

But then the dams (e.g. Jemez Canyon, Abiquiu, Galisteo, and Cochiti) were built, which changed the dynamics of river flooding that made the jetty jacks effective. For example, jetty jacks collected fine sediment from river flooding to build and maintain banks, but the dams sharply curtailed the flow of fine sediment.

Jetty jacks, Rio Grande Valley State Park, New Mexico

Over time, the jetty jacks became a hindrance rather than a benefit.

Jetty jacks, Rio Grande Valley State Park, New Mexico

A detailed discussion of the jetty jack history - as of 2002 - here:  Taking Out the Jetty Jacks: Issues of Jetty Jack Removal in Bosque and River Restoration Planning, by Kathy Grassel, 2002.

In the above article, Ms. Grassel refers to the plans to remove the jacks from the river portion managed by the Santa Ana Pueblo.

Here is that story: Bringing Back the Bosque - Santa Ana Pueblo story.  Published in 2001.

Sidebar: Hmm. This article, published in High Country News, was funded by the McCune Foundation. Ahhh, I thought that sounded familiar.

Jetty jacks, Rio Grande Valley State Park, New Mexico

What interests me is now that a decade has passed, how'd the removal work out? Expectations met?

Per this article, published in 2008, it appears there have, indeed, been positive results. An excerpt:
Along one bank, the Pueblo has removed all "jetty jacks," large metal structures that were installed in the 1950s and 1960s to straighten the river. Removing the jetty jacks allowed the Pueblo to recontour sections of the riverbank, which creates a lower floodplain that helps to reduce channel incision. The recontoured sections have experienced natural revegetation. In addition, the Pueblo has created backwater areas and swales that are planted with native vegetation. The backwater areas increase potential habitat for the Rio Grande silvery minnow, which requires slow-moving currents for spawning. Preliminary surveys (2005-2006) for the minnow on the Pueblo have shown an increase from earlier captures (1995-2000).

Like the Rio Grande silvery minnow, the southwestern willow flycatcher has benefited from habitat changes on the Pueblo. Exploratory surveys in 2001 detected only migratory willow flycatchers. During the summer of 2005, the Santa Ana Pueblo started surveying all suitable riparian habitats within its boundaries for willow flycatchers. After three years of baseline standardized surveys, detections of migratory willow flycatchers have significantly increased from original 2001 estimates. More importantly, southwestern willow flycatchers started residing on the Pueblo in 2006. These new resident flycatchers are defending territories within naturally regenerating riparian vegetation at the confluence of the Rio Jemez and the Rio Grande. This confluence supported very little vegetation in 2001 but is now densely vegetated. The Pueblo used this riparian regeneration as an example to grade the riverbank in an adjacent area to increase sediment deposition. This will create the same type of natural regeneration and expand the available riparian area in hopes that more southwestern willow flycatchers will take residence.

As with so many superficially-simple "problems," the decision to remove or leave in place jetty jacks isn't so simple. The "right" decision depends on: 
  • Who you are - what is your interest in the river and the adjoining land
  • Where the jacks are in relation to the river and to upstream dams
  • What problems - if any - particular jacks are causing
  • The return on the investment in the short, medium, and long-term of leaving the jetty jacks in place or removing them


Anonymous said...

this was very good information

Mzuri said...

Glad you liked it!