Laserfiche WebLink
North Fark, Gunnison River Ecosystem Restoration <br />Appendix B: Engineering Appendix March 2005 <br />6.0 .-ALTERNATIVES ANALYSIS <br />Within the 15-mile project reach of the North Fork there are nine individual sites. Aside from the <br />no-action alternative two additional levels or scales of restoration are evaluated for each site. In <br />general the two scales differ by extent of improvements (project foot print), types and extent of <br />revegetation, and extent and/or density of improvement elements. <br />6.1 RESTORATION ELEMENTS <br />Project objectives and scales of proposed restoration vary at each individual site. However, many <br />techniques and procedures are common among all sites. The following sections are general <br />descriptions of restoration elements, and design considerations of these elements, used through <br />out [he project reach. <br />6.1.1 Channel Reconstruction <br />Channel reconstruction is proposed primazily in areas of the river that have been extensively <br />disturbed from gravel mining. Typical channel cross section dimensions have been calculated <br />from actual field measurements at stable sections elsewhere on [he North Fork and designed for <br />typical bankfull flows of approximately 3,000 cfs. Bankfull flow based on the calculated 1.5-yeaz <br />return flows. The typical channel cross sections may be modified slightly at individual sites <br />following hydraulic calculations [o account for changes in bed slope and specific site objectives. <br />In 1998, prior to the first demonstration project in Hotchkiss, NFRIA measured [he meander <br />lengths, beltwidths, radius of curvature, sinuosity, substrate composition, pool slopes, riffle <br />slopes, riffle/pool ratios and several other morphological variables in stable reaches of [he North <br />Fork in order to develop design criteria for channel and floodplain restoration projects. Following <br />the development of construction plans for the demonstration project, the data, design criteria, and <br />plans were reviewed by Dr. Craig Fischenich at the Army Corps Waterways Experiment Station <br />in Vicksburg, Mississippi prior to construction. Craig was instrumental in verifying design <br />techniques and making several recommendations for rock placement and design within [he <br />channel. Since then six miles of channel rehabilitation and four irrigation diversions on the North <br />Fork has been successfully rehabilitated with minor changes in adaptive management. The design <br />criteria developed specifically for the 1998 North Fork Demonstration Projects will also be used <br />for this 206 Restoration project. <br />6. /.2 Bank Stabilization <br />Bank stabilization will be common to all sites within the project but will vary with type of <br />techniques and quantities based upon individual objectives. <br />Every recent project completed by NFRIA on the North Fork has a willow installation component <br />associated with it. Several techniques have been used with varying degrees of success. Overall; ~ . <br />[he most successful and cost effective technique has been brushmattressing along the banks: <br />Another successful technique has been live willow silt fences installed above the bankfull water ~~ <br />surface elevation perpendicular to the flow of the river. This technique catches debris and <br />sediment and traps it along the newly graded floodplain for natural regeneration of native <br />vegetation. <br />B-29 <br />