The upper Colorado River is a highly regulated system that provides habitat for federally listed species, disproportionate number of flora and fauna and is the water supply for the western United States. River regulation has led to wide scale channel narrowing. Over the last three decades dams have been operated with a more natural hydrograph for environmental reasons. We sought to use remote imagery from 1940-2022 to examine rates of channel narrowing in the pre-dam, post-dam, and environmental flows eras along three river reaches in Canyonlands National Park. We found an increase in the vegetated area along the Colorado River (above the confluence with the Green River) and the Green River since 1940. We documented a 6.12% and 4.00% narrowing in the post-dam period and a 19.51% and 6.49% narrowing in the environmental flows period on the Colorado and Green Rivers, respectively. The Cataract Canyon reach (Colorado River below the confluence) has been stable since 1966. All three river reaches showed the slowest period of narrowing in the last 16 years of environmental flows that coincided with a large peakflow in 2011. All three reaches showed a decrease in vegetated area after the 2011 flood, followed by an increase in vegetated area to similar levels to before the 2011 flood. Environmental flows that mimic the natural hydrograph may have slowed channel narrowing, but it is clear that periodic large peaks are also necessary. Managers must be careful that any environmental flows that take from the spring peak are carefully considered.