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NIWA – Technical Report on Coastal Hydrodynamics and Sediment Processes in Lyall Bay

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NIWA – Technical Report on Coastal Hydrodynamics and Sediment Processes in Lyall Bay Technical Report 17 NIWA – Technical Report on Coastal Hydrodynamics and Sediment Processes in Lyall Bay Wellington Airport Runway Extension Technical Report on Coastal Hydrodynamics and Sediment Processes in Lyall Bay Prepared for Wellington International Airport Ltd March 2015 (updated March 2016) Prepared by: Mark Pritchard Glen Reeve Richard Gorman Iain MacDonald Rob Bell For any information regarding this report please contact: Rob Bell Programme Leader: Hazards & Risk Coastal & Estuarine Processes +64-7-856 1742 [email protected] National Institute of Water & Atmospheric Research Ltd PO Box 11115 Hamilton 3251 Phone +64 7 856 7026 NIWA CLIENT REPORT No: HAM2015-003 Report date: March 2015 (updated March 2016) NIWA Project: WIA15301 Quality Assurance Statement Reviewed by: Dr S. Stephens Formatting checked by: A. Bartley Approved for release by: Dr A. Laing Front page photo: Lyall Bay aerial photograph (2013-14 LINZ aerial photography series). © All rights reserved. This publication may not be reproduced or copied in any form without the permission of the copyright owner(s). Such permission is only to be given in accordance with the terms of the client’s contract with NIWA. This copyright extends to all forms of copying and any storage of material in any kind of information retrieval system. Whilst NIWA has used all reasonable endeavours to ensure that the information contained in this document is accurate, NIWA does not give any express or implied warranty as to the completeness of the information contained herein, or that it will be suitable for any purpose(s) other than those specifically contemplated during the Project or agreed by NIWA and the Client. Contents Executive summary ........................................................................................................... 11 1 Introduction and Background ................................................................................... 17 2 Hydrodynamic field programme: methods and results (Lyall Bay).............................. 18 2.1 Instrumentation ...................................................................................................... 18 2.2 Results ..................................................................................................................... 19 3 Hydrodynamic flow and sediment-transport modelling (Delft2D) .............................. 33 3.1 The approach to hydrodynamic and sediment-transport modelling ..................... 33 3.2 Delft3D modelling Suite .......................................................................................... 35 3.3 Model Development and Setup .............................................................................. 36 3.4 Modelled hydrodynamic scenario results .............................................................. 46 3.5 Sediment-transport modelling ............................................................................... 52 3.6 Discussion and summary ........................................................................................ 58 4 Wave climate: Spectral wave modelling (SWAN) ....................................................... 60 4.1 South Wellington coast wave modelling (SWAN) ................................................... 60 4.2 External forcing ....................................................................................................... 61 4.3 Model verification ................................................................................................... 62 4.4 Lyall Bay wave conditions ....................................................................................... 64 4.5 Wave statistics at selected output locations .......................................................... 70 4.6 Extreme wave climate ............................................................................................ 77 5 Phase-resolving wave model results (ARTEMIS) ........................................................ 79 5.1 ARTEMIS wave model ............................................................................................. 80 5.2 ARTEMIS mesh development.................................................................................. 80 5.3 ARTEMIS model set-up (physical and numerical parameters). .............................. 83 5.4 Boundary reflection ................................................................................................ 84 5.5 Validation ................................................................................................................ 84 5.6 Results showing wave changes due to the proposed runway extension ............... 85 5.7 Discussion/Summary ............................................................................................ 120 6 Suspended-sediment plume modelling (Delft3D-SED) ............................................. 122 6.1 Rationale and scenario modelling approach ........................................................ 122 6.2 Delft3D-SED (Cohesive) ......................................................................................... 124 Wellington Airport Runway Extension 6.3 Suspended-sediment plume results ..................................................................... 126 6.4 Discussion/summary ............................................................................................. 139 7 Acknowledgements ............................................................................................... 140 8 Glossary of abbreviations and terms ...................................................................... 141 9 References ............................................................................................................. 143 Tables Table 2-1: Locations (WGS-84) and 2014 deployment information for the Lyall Bay instruments. 19 Table 2-2: Additional deployment information. 20 Table 2-3: Summary of principal component analysis for currents at Site 1. 26 Table 2-4: Summary of the overall current drift at Site 1 over the deployment period. 29 Table 3-1: RMSE and model Skill for observed and modelled M2, S2 and N2 semi- diurnal tidal amplitude at three sites in the model domain. 42 Table 3-2: Observed and modelled (parentheses) M2, S2 and N2 semi-diurnal tidal current major-axis amplitude at three sites in the model domain. 44 Table 4-1: Locations of wave measurements used to validate the SWAN simulations. 62 Table 5-1: Physical and numerical parameters used in the set-up of ARTEMIS. 83 Table 5-2: Model predicted changes in wave height (m) at site P1 that result from a change in model boundary conditions (ranging from 1–5 m). Note: that the Table values represent the change in significant wave height locally. 88 Table 5-3: Change in predicted wave heights at data extraction site P2. 89 Table 5-4: Change in predicted wave heights at data extraction site P3. 89 Table 5-5: Change in predicted wave heights at data extraction site P4. 90 Table 5-6: Change in predicted wave heights at data extraction site P5. 90 Table 5-7: Change in predicted wave heights at data extraction site P6. 91 Table 5-8: Change in predicted wave heights at data extraction site P7. 92 Table 5-9: Change in predicted wave heights at data extraction site P8. 92 Table 5-10: Percent change in predicted wave heights at data extraction site P1. 93 Table 5-11: Percent change in predicted wave heights at data extraction site P2. 93 Table 5-12: Percent change in predicted wave heights at data extraction site P3. 94 Table 5-13: Percent change in predicted wave heights at data extraction site P4. 94 Table 5-14: Percent change in predicted wave heights at data extraction site P5. 95 Table 5-15: Percent change in predicted wave heights at data extraction site P6. 95 Table 5-16: Percent change in predicted wave heights at data extraction site P7. 96 Table 5-17: Percent change in predicted wave heights at data extraction site P8. 96 Table 6-1: Maximum predicted SSC above background levels after reasonable mixing at ~150 m for discharges at D1–D3 and sediment-discharge rates of 1 and 2 kg/s. 128 4 Wellington Airport Runway Extension Figures Figure 1-1: Aerial image of Wellington International Airport and runway. 17 Figure 2-1: Site map showing oceanographic instrument locations overlying the seabed bathymetry to WVD-53. 21 Figure 2-2: Wind rose for winds measured at Wellington Aero over a period of 28-years (January 1985 to December 2012). 22 Figure 2-3: Wind rose for winds over the deployment period (18-Aug to 09-Oct 2014). 23 Figure 2-4: Current and wind time series for deployment at Site 1. 24 Figure 2-5: Scatter plots of currents at three elevations above the bed at Site 1. 26 Figure 2-6: Progressive current drift at Site 1 at three elevations above the sea bed (bottom-left panel for near the surface) and the depth-average (bottom- right panel). 28 Figure 2-7: Wave parameters measured at Site 1. 30 Figure 2-8: Wave rose for measurements at Site 1. 31 Figure 2-9: Wave parameters measured at Site 2 in outer Lyall Bay. 32 Figure 3-1: Delft3D-WAVE model grid (red) of south Wellington coast superimposed on top of the Delft3D-FLOW model grid (black) that also includes Wellington Harbour. 37 Figure 3-2: Areal extent of the hydrodynamic model bathymetry. 38 Figure 3-3: Close-up of the hydrodynamic model bathymetry in Lyall Bay. 39 Figure 3-4: Winds over the deployment period (18-Aug to 09-Oct 2014). 40 Figure 3-5: Idealised 1-month simulation of a sequence of two southerly (180) and one northerly (0) wind events. 41 Figure 3-6: Comparison of observed (blue) and modelled
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