Virgin River Restoration in Zion National Park
The riparian forest in Zion Canyon is dying of old age
Cottonwood trees are not reproducing in Zion Canyon because of a levee (aka revetment or rip rap) installed during the late 1930s to prevent flooding. Turns out that cottonwoods reproduce by dropping seed on wet soil from spring floods. So the flood protection project eliminating cottonwood reproduction. The remaining trees are getting old as they all date back to before this project. In 2001 I led a study, under the auspices of Grand Canyon Trust, to anaylyze the problem and develop restoration alternatives.
Here I am in May 2016 shooting video while standing on top of the problematic revetment. The river is on the left and the floodplain is on the right, clearly separated by the revetment.
This video describes the problem with the trees in Zion Canyon:
You may read that study here: The Potential For Restoration Along The Virgin River in Zion National Park