CHANNEL EROSION on the MISSOURI RIVER, MONTANA between FORT PECK DAM and the NORTH DAKOTA BORDER 0 5 F a 10 i lu r F e S S = u 0 r .9 ACE, IN FEET 15 fa 6 c e: F a 20 c to r o f S afe 25 ty = 0.85 30 DEPTH BELOW GROUND SURF 35 40 0105 1520 25 30 3540 45 DISTANCE, IN FEET Prepared By: In Collaboration With: USDA-Agricultural Research Service USDA-Natural Resources Conservation Service National Sedimentation Laboratory Lincoln, NE; Bozeman, MT; Culbertson, MT Oxford, Mississippi Iowa Institute of Hydraulic Research Prepared For: Coordinated Resource Management Group - Lower Missouri River CRM Culbertson, Montana May 1999 CHANNEL EROSION on the MISSOURI RIVER, MONTANA between FORT PECK DAM and the NORTH DAKOTA BORDER By: Andrew Simon1, F. Douglas Shields1, Robert Ettema2, Carlos Alonso1, Marie Marshall-Garsjo3, Andrea Curini1 and Lyle Steffen4 Submitted to: Coordinated Resource Management Group-Lower Missouri River CRM Culbertson, Montana May, 1999 1 USDA/ARS, National Sedimentation Laboratory, Oxford, MS 2 Iowa Institute of Hydraulic Research, Iowa City, IA 3 USDA, NRCS, Bozeman, MT 4 USDA, NRCS, Lincoln, NE LIST OF ILLUSTRATIONS ...........................................................................................7 LIST OF TABLES ..........................................................................................................15 PREFACE........................................................................................................................ 18 SUMMARY...................................................................................................................... 19 INTRODUCTION........................................................................................................... 22 Background ................................................................................................................... 22 Concerns of the Lower Missouri River CRM ............................................................... 22 OBJECTIVES AND SCOPE .........................................................................................23 GENERAL VALLEY CHARACTERISTICS ............................................................. 24 Study Reach................................................................................................................... 24 Bed-Material Characteristics..................................................................................... 26 GEOLOGIC HISTORY .................................................................................................32 Geologic Units............................................................................................................... 32 HYDROLOGIC CONDITIONS.................................................................................... 34 Changes in Flow Regime ..............................................................................................34 Rating-Curve Analysis .................................................................................................. 44 SITE SELECTION AND GENERAL CHARACTERISTICS ...................................52 Soil-Series Descriptions ................................................................................................ 52 Gerdrum Clay Loam.................................................................................................. 54 Harlem Series ............................................................................................................ 54 Harlem Silty Clay..................................................................................................54 Harlem Silty Clay Loam ....................................................................................... 54 Havre Series .............................................................................................................. 54 Havre Silt Loam .................................................................................................... 55 Havre Silty Clay Loam.......................................................................................... 55 Havrelon Series ......................................................................................................... 55 Havrelon Loam...................................................................................................... 55 Havrelon Silt Loam ............................................................................................... 55 Havrelon Silty Clay Loam..................................................................................... 56 Lohler Series ............................................................................................................. 56 Lohler Silty Clay...................................................................................................56 Lohler Silty Clay Loam.........................................................................................56 Riverwash.................................................................................................................. 56 Shambo Series........................................................................................................... 57 Trembles Series......................................................................................................... 57 Trembles Fine Sandy Loam .................................................................................. 57 Typic Fluvaquents, Frequently Flooded.................................................................... 57 2 Ustic Torrifluvents .................................................................................................... 57 TESTING AND SAMPLING OF BANK MATERIAL............................................... 59 Identification of Geomorphic Surfaces ......................................................................... 59 CONTROLS OF CHANNEL EVOLUTION: THEORY............................................60 Bed-Level Adjustments................................................................................................. 61 Mathematical Model of Bed-Level Changes ............................................................ 61 BED ELEVATION DATA: APPLICATION............................................................... 65 Bed-Level Response...................................................................................................... 65 Bed Profiles............................................................................................................... 75 Total Bed-Level Changes Since Dam Closure...................................................... 78 MEANDERS AND LATERAL-MIGRATION PROCESSES: THEORY ................ 83 Governing Variables ..................................................................................................... 83 Flow-Field Models .................................................................................................... 85 RESERVOR EFFECTS ON MIGRATION RATES: APPLICATION.....................86 Methods of Analysis...................................................................................................... 87 Channel Planform...................................................................................................... 87 Measurement of Channel Activity ........................................................................ 89 Neck cutoffs .......................................................................................................... 91 Gross Channel Planform ....................................................................................... 91 Planform Geometry Relations............................................................................... 93 Comparison of Pre- and Post-Dam Channel Activity ............................................... 93 Predictors of Future Activity: Bend-Average Values ........................................... 99 Predictors of Future Activity: Sub-reach-Average Values ................................... 99 Neck Cutoffs ....................................................................................................... 109 Discussion ................................................................................................................... 109 Effects on Flood plains............................................................................................ 113 Summary of Results ................................................................................................115 SHEAR STRENGTH AND CHANNEL-BANK STABILITY: THEORY..............116 Governing Forces and Processes................................................................................. 116 Obtaining Shear-Strength Data................................................................................. 117 Accounting for Both Unsaturated and Saturated Bank Materials........................... 119 GEOTECHNICAL CHARACTERISTICS OF THE BANK MATERIAL ............122 Negative Pore-Water Pressures................................................................................... 122 Bank-toe materials....................................................................................................... 131 BANK STABILITY ANALYSES ................................................................................139 Type I: Culman Wedge-Type Analysis: Theory......................................................... 139 Determination of Weighted-Mean Parameter Values ............................................. 140 Results of Culman Analysis: Application ................................................................... 159 Effects