Title

Rapids in Canyon Rivers

Document Type

Article

Subject Area(s)

Geology

Abstract

Evidence from river surveys, historical photographs, and field investigations show that 410 rapids in 12 canyon rivers of the Colorado Plateau region are distributed randomly or only slightly more regularly than random. Rapids, in their distribution, show little tendency toward equal spacing, are not related to discharge, and are not always colocated with debris sources. Analysis of force of flowing water and resistance of the boulders in rapids of the canyons of the Green River in Dinosaur National Monument, Utah-Colorado, shows that although some particles may have been moved by flood flows within the past 75-100 years, the largest particles were not moved. Under the present climatic/hydrologic regime, these rapids are relict geo-morphic features that are either unchanging or are accumulating debris from tributary sources. Consequently, any theory attempting to explain the distribution and dynamics of rapids in canyon rivers must (1) appeal to the relationship between force and resistance as a measure of stability at particular sites, without reference to operation of the river system as a whole; and (2) account for the effects of climatic/hydrollogic conditions that have recurrence intervals greater than 100 years.

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