Document Type


Subject Area(s)

Environmental Sciences; Limnology; Water Resources


The force of flowing water and the resistance of the largest boulder provide a means of evaluation of the stability of rapids in canyon rivers. Field measurements and calculations show that the closure of Flaming Gorge Dam, Utah, has had a significant effect on the stability of rapids in the canyons of the Green River in Dinosaur National Monument 68 km (42 mi) downstream from the dam. The reduction in peak flows by the dam has limited the competence of the river to move boulders deposited in the main channel by tributary processes, landslides, and prehistoric floods. Before the dam was closed, 62% of the rapids were stable, as indicated by the immobility of the largest boulder in each rapid. After the dam was closed, 93% of the rapids were stable as geomorphic/hydraulic features, though small boulders continue to move. A continuing buildup of boulders in the rapids will result from tributary contributions which are not affected by the dam.


© 1980 by American Geophysical Union

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