ROBERTS BANK CONTAINER EXPANSION COASTAL GEOMORPHOLOGY STUDY Appendix B Prepared for: Vancouver Port Authority Prepared by: northwest hydraulic consultants 30 Gostick Place North Vancouver, B. C. V7M 3G2 In association with: Triton Consultants Ltd. 3530 West 43rd St. Vancouver, B. C. V6N 3J9 November 2004 33863 Vancouver Port Authority Northwest Hydraulic Consultants Ltd/Triton Consultants Ltd. Roberts Bank Container Expansion File: 33863 Coastal Geomorphology Study – Appendix B - i - November 2004 EXECUTIVE SUMMARY This appendix summarizes the development, calibration, testing and verification of a suite of two-dimensional hydrodynamic models for assessing project impacts associated with the Deltaport Third Berth Project. The terms of reference for the study identified the area of interest to be modelled as follows: “Extending north to the mouth of the main arm near Steveston, south to Point Roberts, west to the 100 m depth contour and east to the highwater mark”. The model development was carried out in three phases. The first phase involved tidal modelling studies in the Strait of Georgia, Juan de Fuca Strait and around Vancouver Island using Tide2D. This “Wide Area Model” was used to provide tidal height and tidal current boundary conditions along a line in the deeper waters of Strait of Georgia parallel to Roberts Bank extending from just north of Sandheads at the mouth of the Fraser River to the southern tip of Point Roberts. These boundary conditions were used primarily to drive other detailed tidal models of the Roberts Bank inter-causeway area. The second phase involved developing a Base Model to simulate hydrodynamic conditions in the Fraser estuary, Roberts Bank tidal flats and adjacent portions of the Strait of Georgia. This Base Model was used to assess general flow patterns in the area of interest and to identify the potential extent of impacts from various alternative project developments. Finally, a Detailed Model was developed specifically for the Deltaport Third Berth Project to assess local flow conditions in the Inter-causeway area between the Tsawwassen Ferry Terminal and Roberts Bank Causeway. This Detailed Model was particularly useful for assessing shallow flows on the tidal flats and in eelgrass covered areas as well as for assessing flow effects induced by structures such as the proposed wharf extension at Deltaport Third Berth and the existing crest protection weir on the tidal flats. The computational mesh for the Detailed Model has a resolution of between 5-10 m in critical areas near the proposed developments in order to adequately represent project impacts and complex flows in adjacent tidal drainage channels. The model was verified with a series of ADCP current velocity measurements in April and May 2004. Comparisons between predicted and measured velocities showed excellent agreement. The results from the Detailed Model show that impacts of the proposed Deltaport Third Berth Project on tidal currents would be very small. Local velocities are increased over an area Vancouver Port Authority Northwest Hydraulic Consultants Ltd/Triton Consultants Ltd. Roberts Bank Container Expansion File: 33863 Coastal Geomorphology Study – Appendix B - ii - November 2004 primarily in the immediate vicinity of the wharf extension. Local velocities will be decreased over an area primarily behind the wharf extension. The magnitude of the velocities in the impact zone is well below the threshold for any significant sediment transport. Therefore, we do not expect significant morphological impacts to develop in response to changes in tidal flow magnitude or direction. Preliminary runs were made with the Base Model to assess the cumulative effects from other proposed developments on the west side of the Roberts Bank Causeway (Terminal 2 Project) on the Deltaport Third Berth Project. This analysis showed that preliminary configurations for Terminal 2 could produce significant changes to the magnitude of tidal currents draining on the west side of the causeway. However, the impacts did not extend into the inter-causeway area and did not affect hydrodynamic conditions in the vicinity of the Deltaport Third Berth Project. Therefore, in terms of representing hydrodynamic impacts, the two developments can be assessed independently. More detailed modelling will be required to finalize the assessment of local impacts from Terminal 2 project. Vancouver Port Authority Northwest Hydraulic Consultants Ltd/Triton Consultants Ltd. Roberts Bank Container Expansion File: 33863 Coastal Geomorphology Study – Appendix B - iii - November 2004 TABLE OF CONTENTS 1.0 INTRODUCTION............................................................................................................. 1 1.1 SCOPE OF WORK ...................................................................................................... 1 1.2 DELTAPORT THIRD BERTH PROJECT DESCRIPTION .................................................. 2 1.3 TERMINAL 2 PROJECT .............................................................................................. 3 1.4 METHOD OF APPROACH ........................................................................................... 3 1.5 ASSUMPTIONS AND LIMITATIONS ............................................................................ 4 2.0 WIDE AREA MODEL..................................................................................................... 6 2.1 MODEL DESCRIPTION............................................................................................... 6 2.2 MODEL DEVELOPMENT............................................................................................ 6 2.3 MODEL CALIBRATION.............................................................................................. 8 2.4 MODEL RESULTS ................................................................................................... 10 3.0 BASE MODEL................................................................................................................ 12 3.1 MODEL DESCRIPTION............................................................................................. 12 3.2 BASE MODEL DEVELOPMENT ................................................................................ 13 3.2.1 Work Carried Out ..................................................................................... 13 3.2.2 Boundary Conditions................................................................................ 13 3.2.3 Roberts Bank and Project Geometry......................................................... 14 3.2.4 Model Verification.................................................................................... 16 3.2.5 Representative Tide Conditions................................................................ 18 3.2.6 Sensitivity Analysis.................................................................................. 19 3.3 MODEL RESULTS ................................................................................................... 19 3.3.1 Present Conditions .................................................................................... 19 3.3.2 Third Berth Project................................................................................... 24 3.3.3 Terminal 2 Project..................................................................................... 24 4.0 DETAILED MODEL DEVELOPMENT ..................................................................... 27 4.1 MODEL DESCRIPTION............................................................................................. 27 4.2 MODEL DEVELOPMENT.......................................................................................... 27 4.2.1 Work Carried Out ..................................................................................... 27 4.2.2 Model Extent and Boundary Conditions................................................... 28 Vancouver Port Authority Northwest Hydraulic Consultants Ltd/Triton Consultants Ltd. Roberts Bank Container Expansion File: 33863 Coastal Geomorphology Study – Appendix B - iv - November 2004 4.2.3 Topography and Project Geometry........................................................... 29 4.2.4 Vegetation................................................................................................. 29 4.3 MODEL VERIFICATION ........................................................................................... 31 4.3.1 Field Program............................................................................................31 4.3.2 Comparisons with Model Predictions....................................................... 32 4.4 MODEL RESULTS – PRESENT CONDITIONS ............................................................. 36 4.4.1 Flow Conditions Near Deltaport............................................................... 36 4.4.2 Drainage Channels.................................................................................... 49 4.5 MODEL RESULTS – DELTAPORT THIRD BERTH PROJECT IMPACTS......................... 52 5.0 CONCLUSIONS ............................................................................................................. 56 6.0 REFERENCES................................................................................................................ 57 Vancouver Port Authority Northwest Hydraulic Consultants Ltd/Triton Consultants Ltd. Roberts Bank Container Expansion File: 33863 Coastal Geomorphology Study – Appendix B - v - November 2004 List of Tables Table B2-1: Results of Calibration – Comparison.........................................................................