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<br />C:.178"6
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<br />Table of Contents
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<br />1, Introduction..... ,..,.,.................. ......... ..... .......... ,............... ......... ....... .................... .........1
<br />1.1. Project Location ........................,............................,.........................,............,......... 1
<br />1.2. Report Organization... .... ..... ,.......................... .... ,.. ,.................. .................. ............. 1
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<br />2. Background....... ,..... ,.. ,...... ........,................... ......... ,.. ........ .......... ,.... ,;. ,................... .....5
<br />2.1. The Upper Arkansas River Restoration Project...................................................... 5
<br />2.2. Project Goals and Objectives .....,......................,..................................................... 5
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<br />2.3. Procedure.................... .......................... ,..... ......... ....... ......... ..... ....... ,....... ......... ....., 6
<br />2.3.1. Existing Data.................................................,....,..................,..,..................,...6
<br />2.3.2. Field Investigation ............,....,......................,.............,............................,......6
<br />2.3.3, Human Impacts on River Geomorphology.............................,....................... 6
<br />2.3.4. Channel Stability ..................................,.......................,....,.....................,....... 7
<br />2.3.5. Tailings Entrainment Potential...........................................,........................... 7
<br />2.3.6. Conceptual Rehabilitation Alternatives ....,....,...........................,................,...7
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<br />3. Historic Impacts: Mining, Flow Augmentations, and Project Reach Land Use.........8
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<br />3,1. Mining Impacts ...,......................................................................,............................. 8
<br />3.2, Flow Diversions and Augmentations....................................................................., 9
<br />3.2.1, The Diversion/Augmentation System............................................................. 9
<br />3.2.2. Hydrologic Effects,...................,..,................,................................,........,.......9
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<br />3.3. Land Use ........,..,.....,..............,...........................,..................................................13
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<br />4. Physical Characteristics of the Upper Arkansas River Basin....................................22
<br />4,1, Geologic Setting....................,..............,..............................................,.................22
<br />4,2. General Geomorphic Characteristics of Study Reach .......................................,.. 22
<br />4.2.1. Subreach 1: Upstream of California Gulch (RM 10.9-12) ..........................22
<br />4.2.2. Subreach 2: California Gulch to Lake Fork (RM 9.2-10.9)......................... 24
<br />4.2.3. Subreach 3: Lake Fork to Railroad Bridge (RM 7.0-9.2)............................. 27
<br />4.2.4. Subreach 4: Railroad Bridge to Hwy 24 Bridge (RM 5.5-7.0).................... 27
<br />4.2.5. Subreach 5: Hwy 24 Bridge to Big Union Creek (RM 3.3-5,5).................. 30
<br />4.2.6. Subreach 6: Big Union Creek to Hwy 55 Bridge (RM 2.1-3.3).................. 30
<br />4.2.7, Subreach 7: Hwy 55 Bridge to Bedrock Constriction (RM 0-2.1).............. 30
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<br />5. Sedimentology of Upper Arkansas River ..................................................................33
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<br />6. Geomorphic Evolution of Project Reach ....,........,.......................,.............................35
<br />6.1. The Stable Channel Balance .................................................................................35
<br />6.2. Influence of Flow Augmentations on Channel Dynamics......,................,............ 36
<br />6.3. Historic Changes in Upper Arkansas River Morphology.......................,......,...... 37
<br />6.3.1. Sinuosity and Split Flow............................................................................... 37
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<br />6.3 .2. Cross-section.,........................,...................,.,.............................................,.. 40
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<br />May 7, 1999
<br />
<br />Fluvial Geomorphological Assessment
<br />Upper Arkansas River
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