FLOOD10354

• Document ID: pr1202
• County: Delta
• Community: Paonia, Hotchkiss
• Stream Name: North Fork Gunnison River
• Basin: Gunnison
• Sub-Basin: North Fork Gunnison
• Water Division: 4
• Title: North Fork Gunnison River Project Executive Summary
• Date: 12/1/2002
• Prepared By: Colorado State University
• Watershed Pro - Doc Type: Project Report

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larger-sized sediment that forms on the bed of streams. This coarser surface layer helps to
stabilize the streambed and limit bed erosion. Natural riverside vegetation helps to
stabilize stream banks both through the presence of tree roots, which increase bank
cohesion, and the presence of above-ground parts of the plant that increase the boundary
roughness of the river, thus slowing the velocity and erosive ability of overbank flows.

We also recommend that river rehabilitation efforts be designed with the understanding
that the North Fork Gunnison River is predominantly a braided rather than a single-thread
channel. River rehabilitation that attempts to increase the erosional resistance of the
streambanks, re-establish riparian vegetation, and provide a sufficiently wide river
corridor for some lateral channel movement can be useful in improving aquatic habitat
and reducing hazards along the river, but the goal of creating a sinuous, single-thread
channel is probably not realistic.

IV What is role of Paonia Reservoir in controlling channel planform and stability?
As discussed above, the role of the reservoir in controlling channel characteristics
along the North Fork Gunnison River remains uncertain. The reservoir traps some fine-
grained sediment, and this might be expected to increase downstream channel instability,
because fine sediment increases bank cohesion and enhances establishment of riparian
vegetation. However, there are abundant sources of fine sediment downstream from the
reservoir, so that the reservoir's trapping effect may not be particularly important in
reducing the downstream supply of fine sediment. Resolution of these uncertainties
requires development of a detailed sediment budget for suspended sediment along the
river both upstream and downstream from the reservoir.

V What are the implications of this study for other rivers in Colorado?
The results of this study may be useful in understanding other rivers in Colorado,
but these results cannot be "blindly" applied to other rivers. There are at least three
important factors that may cause other rivers in Colorado to behave differently than the
North Fork Gunnison; geology, climate, and topography. Geology, in combination with
climate, determines the volume and grain-size of sediment supplied to a river. The North

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