Appendix C - TSUNAMI ANALYSIS Contractor 2015-03-26 Trans Mountain Expansion Project Revision Date: Contractor Tsunami Assessment A Revision No.: Page 1 of 73 M&N File 9665/55 Trans Mountain Expansion Project Tsunami Assessment KMC Document # 01-13283-TW-WT00-MFN-RPT-0008 Rev Prepared by/ Reviewed by/ Approved by/ TMEP Pages Issued Type No. Date Date Date Acceptance/ Revised Date C-F Tsai M. Jorgensen R. Byres A Issued for Review 2015-03-26 2015-03-26 2015-03-26 TRANS MOUNTAIN EXPANSION PROJECT WESTRIDGE TERMINAL, BURRARD INLET, BC TSUNAMI ASSESSMENT Prepared for: Prepared by: TRANS MOUNTAIN EXPANSION PROJECT WESTRIDGE TERMINAL, BURRARD INLET, BC TSUNAMI ASSESSMENT M&N Project No. 7773‐03 Revision Description Issued Date Author Reviewed Approved B Issued For Review Mar. 26, 2015 C‐F Tsai MJ/RB RB A Progress Draft Feb. 11, 2015 C‐F Tsai MJ/RB RB Westridge Marine Terminal Tsunami Assessment 3 EXECUTIVE SUMMARY Kinder Morgan Canada is currently considering expansion of marine facilities at the Westridge Terminal at Burnaby, BC as part of the Trans Mountain Expansion Project (TMEP). The terminal expansion includes the construction of three (3) new jetty berths capable of accepting vessels of varying size and cargo type. The present study provides a screening level assessment of landslide‐induced tsunami hazards to the proposed Westridge Terminal and vessels berthed at the facility. The overall scope of work includes: 1. Assessment of the characteristics of tsunami waves (amplitude, period, and wave induced currents) generated by potential landslides within the Indian Arm and Burrard Inlets; 2. Evaluation of the plausible threat of potential impacts to berthed vessels; 3. Recommendations for design if the tsunami waves are perceived to be significant enough to result in potential issues to berthed vessels. CONCLUSIONS Based on the scenarios investigated, the following conclusions can be made. Landslide Scenarios A number of potential landslide scenarios (i.e. location and slide volume) were provided to M&N by BGC Engineering Ltd. These landslide scenarios cover a large range of hazard exposure from no tsunami generation, to an extreme event comparable with some of the largest known historical landslide‐generated tsunamis on record. This large range of scenarios was included to cover the maximum plausible range of outcomes, initially without considering the very low (and as yet unquantified) probability of such events. Since there are no records of past landslides or tsunamis occurring in Burrard Inlet or Indian Arm, there is currently no means to quantify the probability or return period of the scenarios examined. Nonetheless, it is believed that the risk of such extreme events is very low. A more detailed geological or geotechnical assessment is needed to establish to what extent the investigated landslide scenarios are credible. At present, the extreme condition of landslide scenario 1 is comparable (actually slightly greater) than the mega‐landslide evidenced in Lituya Bay, Alaska which occurred in 1958. The current findings point to the fact that landslides of such magnitude tend to be localized by particular geological conditions conducive to formation of Kinder Morgan Canada – Trans Mountain Expansion Project March 26, 2015 Westridge Marine Terminal Tsunami Assessment 4 large deposits of unstable rock. It is recommended that a geologist be consulted to establish whether that is the case in Indian Arm. Because no present findings point to large landslides in Indian Arm and Burrard Inlet in the past, and because the area has had (geologically) recent exposure to the 1700 Cascadia fault rupture, which was approximately magnitude 9.0, landslide scenario 1 is at present deemed implausible, subject to further geological investigation. This study can therefore be considered to represent “worst case” conditions. If landslide parameters are revisited and revised downwards, the result would be a substantial reduction in the magnitude of tsunami wave height, and corresponding flow velocities. Tsunami Wave Formation and Propagation Regarding the formation of tsunami waves as a result of landslide activity, it can be noted that while the initial wave height produced at the point of landslide impact can be substantial, features of Indian Arm tend to limit the maximum wave heights affecting the project site. Factors affecting initial tsunami wave heights include the water depth and bathymetry, and the fact that the fjord is quite narrow, with the primary landslide momentum directed across the fjord rather than along its length. Aspects of the bathymetry, such as the change from deep water in the central portion of Indian Arm to quite shallow water at the southern end down in Burrard Inlet work to impede tsunami wave front propagation. The narrow opening of the inlet at the southern end of Indian Arm further works to disperse tsunami wave energy. Impacts to Berthed Vessels The record of simulated water level variations and tsunami‐induced currents at the project site shows that tsunami‐induced water level variations are within the range of typical tides occurring in Burrard Inlet. While tsunami wave propagation would unfold over a matter of minutes as opposed to hours for tidal variations, the water level changes are believed to be slow enough that vessel moorings would be able to accommodate the change. Likewise, it is found that tsunami‐induced currents are within the range of the OCIMF cases investigated in the mooring analysis (M&N, 2014), and moored vessels would therefore not be particularly prone to tsunami‐related impacts. We therefore conclude that the risk of a vessel being damaged or experiencing a breakaway event from parted mooring lines is very low. We further infer from the results that damage to the facility itself (such as wave impact damage, run‐ up, or overtopping/inundation), is similarly very low. Kinder Morgan Canada – Trans Mountain Expansion Project March 26, 2015 Westridge Marine Terminal Tsunami Assessment 5 TABLE OF CONTENTS 1. INTRODUCTION ......................................................................................................................... 9 1.1 Site Description ................................................................................................................... 9 1.2 Project Background ........................................................................................................... 10 1.3 Scope of Work ................................................................................................................... 12 2. DATA REVIEW .......................................................................................................................... 13 2.1 Tsunamis From Distant Sources ........................................................................................ 13 2.2 Categorization of Landslides ............................................................................................. 14 2.3 Locally Generated Tsunamis ............................................................................................. 17 2.3.1 Subaerial Landslide Scenarios .................................................................................... 20 2.4 Development of Landslide Parameters ............................................................................. 25 2.5 Assessment with Analytical Approximation ...................................................................... 28 3. DEVELOPMENT OF NUMERICAL MODEL ................................................................................ 30 3.1 MIKE‐21 Hydrodynamic Model ......................................................................................... 30 3.2 Model Bathymetry & Topography .................................................................................... 30 3.3 Boundary Conditions ......................................................................................................... 30 3.4 Modeling Approach ........................................................................................................... 31 3.5 Modeling Cases ................................................................................................................. 33 3.6 Comparison With Analytical Approximations ................................................................... 34 3.6.1 Analytical/Numerical Model Comparison .................................................................. 36 4. SUMMARY OF MODEL RESULTS ............................................................................................. 41 4.1 Tsunami Wave Propagation .............................................................................................. 42 4.2 Tsunami Wave Attenuation ............................................................................................... 51 4.3 Results for Modeling Cases ............................................................................................... 51 5. EVALUATION OF MOORING IMPACTS .................................................................................... 57 5.1 Tsunami‐Induced Water Level Variations ......................................................................... 57 5.2 Tsunami‐Induced Flow Velocities ...................................................................................... 60 5.2.1 Comparison of Tsunami‐Induced Flow Velocities and Mooring Analysis .................. 63 6. SUMMARY AND CONCLUSIONS .............................................................................................. 66 6.1 Discussion of