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I I I I I I I I I I I I I I I I I I I North Fork Gunnison River Project Executive Summary Ellen Wohl, Christopher Jaquette and David Cooper, Department of Earth Resources, Colorado State University, Ft. Collins, Colorado 80523 The executive summary presented here is based on three items: thesis research conducted by Christopher Jaquette during 2000-2002 as part of his Master of Science degree at Colorado State University; a field study of cottonwood ages in relation to valley-bottom topography and stratigraphy along the North Fork Gunnison River between Paonia and Hotchkiss; and discussions of the two studies with Jeff Crane of the North Fork River Improvement Association and Brian Hyde of the Colorado Water Conservation Board. The thesis research and cottonwood study were designed to address questions related to ongoing river rehabilitation and management along the North Fork Gunnison River. Specifically, we (1) investigated historical channel change along the North Fork Gunnison River, using historical documents, aerial photographs from the period 1939- 1997, and the ages and geographic distribution of cottonwood trees along the river, and (2) developed a sediment budget for coarse-sized sediment (gravel and larger) along the river that quantified volumes and grain-size distributions of potential sediment sources such as tributary channel fans and landslides, as well as sediment characteristics within the main channel. These two primary tasks were undertaken to evaluate the impacts of Paonia Dam on sediment dynamics along the North Fork Gunnison River, and to determine the most likely planform for the river (meandering vs braided), as well as the impacts of various human activities on river stability and planform. The terms "braided" and "meandering" river are used throughout this summary. A braided river has multiple flow paths, rather than a single channel. The multiple channels are highly unstable, and the river constantly changes the location of most flow. Braided rivers are characterized by abundant coarse sediment (sand- to cobble-sized), steeper downstream slopes, fluctuating flow levels, and erodible banks that are not stabilized by vegetation. In contrast, meandering rivers have a well-defined single channel that is very sinuous. These rivers move laterally by eroding the outside of each meander bend and depositing sediment on the inside of each bend, as well as by periodically cutting off meander bends. However, the rates of bank moyement along meandering rivers are likely 1