Sediment-transport during three controlled-flood experiments on the Colorado River downstream from Glen Canyon Dam, with implications for eddy-sandbar deposition in Grand Canyon National Park

Higher suspended-sand concentrations during controlled floods lead to greater eddy-sandbar deposition rates, but larger amounts of coarser sand on the riverbed can paradoxically reduce these rates. This counterintuitive finding emerges from three large-scale field experiments conducted in 1996, 2004, and 2008 on the Colorado River downstream from Glen Canyon Dam. The studies analyzed sediment transport and bed-sediment data to assess how controlled floods could sustainably rebuild eddy sandbars in Grand Canyon National Park when combined with tributary sand supply. While suspended-sand concentrations peaked during the 2008 experiment, this was likely due to increased bed sand in lower Glen Canyon rather than Grand Canyon. The research highlights the need to balance flood magnitude and grain size in future controlled floods to optimize sandbar deposition, though long-term sustainability remains uncertain.

Topping, D. J., Rubin, D. M., Grams, P. E., Griffiths, R. E., Sabol, T. A., Voichick, N., Tusso, R. B., Vanaman, K. M., & McDonald, R. R. (2010). Sediment-transport during three controlled-flood experiments on the Colorado River downstream from Glen Canyon Dam, with implications for eddy-sandbar deposition in Grand Canyon National Park. Open-File Report. https://doi.org/10.3133/ofr20101128