Section 16.2 RIVER HYDRAULICS AND RIVER MORPHOLOGY STUDY Technical Volume George Massey Tunnel Replacement Project Technical Volume – River Hydraulics and River Morphology Study TABLE OF CONTENTS Abbreviations and Acronyms ................................................................................................. viii Glossary ...................................................................................................................................... ix 1.0 Introduction ..................................................................................................................... 1 1.1 Project Background ............................................................................................... 1 1.2 Study Overview and Objectives ............................................................................ 1 2.0 Methods ........................................................................................................................... 3 2.1 Assessment Area .................................................................................................. 3 2.2 Temporal Scope .................................................................................................... 7 2.3 Study Methods ...................................................................................................... 8 2.3.1 Interpretive Geomorphology ................................................................... 8 2.3.2 Numerical Modelling ............................................................................... 8 2.4 Tunnel Description ................................................................................................ 9 3.0 Existing Tunnel Conditions .......................................................................................... 10 3.1 Proposed Tunnel Decommissioning Alternatives ................................................ 12 3.1.1 Full Tunnel Removal ............................................................................. 12 3.1.2 Partial Tunnel Removal ........................................................................ 12 4.0 Physical Setting ............................................................................................................ 13 4.1 Fraser River Flows and Sediment Loads ............................................................ 13 4.1.1 Flows .................................................................................................... 13 4.1.2 Flow Patterns ........................................................................................ 14 4.1.3 Salt Wedge ........................................................................................... 16 4.1.4 Sediment Loads .................................................................................... 17 4.2 Dunes .................................................................................................................. 18 4.3 Water Levels ....................................................................................................... 18 4.3.1 Water Level Changes ........................................................................... 21 4.4 River Infrastructure .............................................................................................. 23 4.4.1 Water Mains and Pipelines ................................................................... 23 4.4.2 Bridge Crossings .................................................................................. 23 4.4.3 River Training ....................................................................................... 23 4.4.4 Bank Hardening .................................................................................... 24 i George Massey Tunnel Replacement Project Technical Volume – River Hydraulics and River Morphology Study 4.5 Dredging .............................................................................................................. 26 5.0 Fluvial Processes and Morphology ............................................................................. 28 5.1 Long-Term Lateral Changes ............................................................................... 28 5.2 Long-Term Vertical Changes .............................................................................. 31 5.3 Project Considerations ........................................................................................ 40 6.0 Modelling Methodology ................................................................................................ 42 6.1 Far-Field and Near-Field Models ......................................................................... 42 6.2 Modelled Scenarios ............................................................................................. 45 6.3 Model Geometry .................................................................................................. 46 6.3.1 Existing Conditions ............................................................................... 46 6.3.2 Full Tunnel and Partial Tunnel Removal Geometries ........................... 47 6.4 Boundary Conditions ........................................................................................... 52 6.5 Sediment Characteristics .................................................................................... 54 6.6 Calibration and Validation ................................................................................... 54 6.6.1 Hydrodynamics ..................................................................................... 55 6.6.2 Morphodynamics .................................................................................. 56 6.7 Salt Wedge .......................................................................................................... 57 7.0 Model Simulation Results ............................................................................................ 60 7.1 Existing Conditions during Low Flow Period ....................................................... 60 7.1.1 Hydrodynamics ..................................................................................... 60 7.1.2 Morphodynamics .................................................................................. 65 7.2 Existing Conditions during Freshet ...................................................................... 66 7.2.1 Hydrodynamics ..................................................................................... 67 7.2.2 Morphodynamics .................................................................................. 71 7.3 Trench Infilling Scenario ...................................................................................... 74 7.3.1 Hydrodynamics ..................................................................................... 74 7.3.2 Morphodynamics .................................................................................. 80 7.4 Post-Infilling Scenario .......................................................................................... 84 7.4.1 Hydrodynamics ..................................................................................... 84 7.4.2 Morphodynamics .................................................................................. 90 ii George Massey Tunnel Replacement Project Technical Volume – River Hydraulics and River Morphology Study 8.0 Discussion of Potential Changes Due to the Project ................................................. 94 8.1 Construction Phase ............................................................................................. 94 8.1.1 New Bridge Crossing ............................................................................ 94 8.1.2 Tunnel Removal .................................................................................... 94 8.2 Operation Phase ................................................................................................. 96 8.2.1 New Bridge Crossing ............................................................................ 96 8.2.2 Tunnel Removal .................................................................................... 96 9.0 Limitation ....................................................................................................................... 99 10.0 References ................................................................................................................... 100 LIST OF TABLES Table 1-1 River Hydraulics and River Morphology Study Components and Objectives ........ 2 Table 4-1 Hourly Exceedence and Non-exceedence Probabilities for Fraser River Water Levels at Deas Island (WSC 08MH053, 1969 – 1984) ........................................ 21 Table 7-1 Modelled non-freshet water level statistics for August 16, 2012 ......................... 63 Table 7-2 Modelled Flow Splits on August 16, 2012 ........................................................... 65 Table 7-3 Modelled Minimum and Maximum Water Levels under Existing Conditions for June 22 to June 24, 2012 .................................................................................... 70 Table 7-4 Flow splits under existing conditions on June 23, 2012 ...................................... 71 Table 7-5 Modelled Non-freshet Water Level Statistics for August 16, 2012 ...................... 77 Table 7-6 Modelled Flow Splits on August 16, 2012 ........................................................... 77 Table 7-7 Modelled Freshet Water Level Statistics and Differences between Existing Conditions and the Full Tunnel Removal Conditions for June 22 to June 24, 2012 ...........................................................................................................................