Grand Canyon experiment - big changes were short-lived

The USGS flood  ("High Flow Experiment") in the Grand Canyon in 2008 demonstrated significant sandbar development but the results were fairly rapidly eroded away once the Colorado River flow was again constrained by its use for power generation. 

The USGS report concluded:

Although sandbar building was widespread in response to the 2008 HFE, which occurred under highly sand-enriched conditions, these gains were short lived owing to erosion that occurred once releases from the dam resumed normal fluctuating-flow operations.

[right, matched photographs taken by a remote camera of a sandbar (Willie Taylor Camp) on the Colorado River about 45 miles downstream from Lees Ferry, Arizona. The series of photographs shows how the sandbar and its accompanying backwater (the area of water behind the sandbar thought to provide habitat for native fish) were affected by the 2008 high-flow experiment (HFE) and subsequent erosion in the 8 months following the HFE. All of the photographs were taken at about 4 P.M. at a water level associated with a flow rate of about 8,500 cubic feet per second from Glen Canyon Dam.  Photo and caption, credit USGS]

Ref: Melis, T.S., Topping, D.J., Grams, P.E., Rubin, D.M., Wright, S.A., Draut, A.E., Hazel, J.E., Jr., Ralston, B.E., Kennedy, T.A., Rosi-Marshall, Emma, Korman, Josh, Hilwig, K.D., and Schmit, Lara M., 2010, 2008 High-flow experiment at Glen Canyon Dam benefits colorado river resources in Grand Canyon National Park: U.S. Geological Survey Fact Sheet 2010-3009, 4 p.