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<br />May 7, /999
<br />
<br />Fluvial Geomorphological Assessment
<br />Upper Arkansas River
<br />
<br />Page 6
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<br />the achievement of improved fluvial function will necessarily benefit aquatic and riparian
<br />ecosystems, specific objectives of biological enhancement are not directly addressed
<br />herein, The conceptual strategies represent basic restoration approaches that are
<br />specifically applicable to identified geomorphic processes, This approach is intended to
<br />assist in the future development of a detailed restoration plan that will include treatment
<br />prioritizations and modifications based on issues such as relative toxicity of individual
<br />deposits, feasibility ofin-situ treatments, specific biological objectives, land use, and
<br />water rights,
<br />
<br />The approach adopted in this investigation focuses on the achievement of geomorphic
<br />stability and reduction of tailings entrainment potential rather than the redevelopment of a
<br />historic channel state; consequently, the term channel rehabilitation will be utilized to
<br />describe treatment options rather than the commonly utilized term of channel restoration.
<br />
<br />2.3. Procedure
<br />
<br />The data presented in this report represent a compilation of original material as well as
<br />information obtained from various published and unpublished documents,
<br />
<br />2,3,1, Existing Data
<br />
<br />Photogrammetric base maps of the project reach at a 2-ft contour interval and a
<br />companion hydraulic model were utilized extensively in this study for field mapping,
<br />topographic characterization of subreaches, and hydraulic and sediment transport
<br />analyses, The mapped delineation of previously identified tailings deposits CURS, 1997;
<br />1998) was used to identifY those deposits most prone to entrainment CURS, 1998),
<br />Hydrology was characterized based on USGS gage data, information provided by the
<br />USBR, and existing reports (URS, 1998, O'Neill, et ai, 1997; Studzinski, 1996), Aerial
<br />photographs dated 1939, 1956, 1996, and 1997 were evaluated to determine historic
<br />changes in channel pattern and migration rates,
<br />
<br />2,3,2, Field Investigation
<br />
<br />In spring of 1998, several suites of bedload sediment data were collected within the
<br />project reach, This information was subsequently utilized to calibrate the sediment
<br />transport analysis, A reconnaissance field investigation of the study area was conducted
<br />in July of 1998, The 2-ft photogrammetric map supplied by URS was utilized as a base
<br />map, Geomorphic, sedimentologic and man-made features of interest were mapped onto
<br />the base sheets, The II-mile project reach was segmented into 6 project subreaches (a
<br />seventh subreach is located upstream of the project reach). Representative channel
<br />segments were identified for sediment transport evaluations, Photographic
<br />documentation was extensive, In September of 1998, a total of 6 representative channel
<br />segments were surveyed in detail for the hydraulic/sediment transport evaluation, and are
<br />referred to herein as Incipient Motion (1M) Sites (Figure 2.2), This involved surveying
<br />several cross-sections for development of local hydraulic models at each site,
<br />
<br />2,3,3, Human Impacts on River Geomorphology
<br />The historic impacts of mining, flow augmentations, and land use on fluvial processes
<br />within the project reach were assessed based on an integration of information derived
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