Appendix C - TSUNAMI ANALYSIS

Transcription

1 Appendix C - TSUNAMI ANALYSIS

2 Trans Mountain Expansion Project Tsunami Assessment Contractor Revision Date: Contractor Revision No.: A M&N File 9665/55 Page 1 of 73 Trans Mountain Expansion Project Tsunami Assessment KMC Document # TW-WT00-MFN-RPT-0008 Rev No. Prepared by/ Date Reviewed by/ Date Approved by/ Date TMEP Acceptance/ Date Pages Revised Issued Type A C-F Tsai M. Jorgensen R. Byres Issued for Review

3 TRANS MOUNTAIN EXPANSION PROJECT WESTRIDGE TERMINAL, BURRARD INLET, BC TSUNAMI ASSESSMENT Prepared for: Prepared by:

4 TRANS MOUNTAIN EXPANSION PROJECT WESTRIDGE TERMINAL, BURRARD INLET, BC TSUNAMI ASSESSMENT M&N Project No 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

5 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 The current findings point to the fact that landslides of such magnitude tend to be localized by particular geological conditions conducive to formation of

6 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, runup, or overtopping/inundation), is similarly very low.

7 Westridge Marine Terminal Tsunami Assessment 5 TABLE OF CONTENTS 1. INTRODUCTION Site Description Project Background Scope of Work DATA REVIEW Tsunamis From Distant Sources Categorization of Landslides Locally Generated Tsunamis Subaerial Landslide Scenarios Development of Landslide Parameters Assessment with Analytical Approximation DEVELOPMENT OF NUMERICAL MODEL MIKE 21 Hydrodynamic Model Model Bathymetry & Topography Boundary Conditions Modeling Approach Modeling Cases Comparison With Analytical Approximations Analytical/Numerical Model Comparison SUMMARY OF MODEL RESULTS Tsunami Wave Propagation Tsunami Wave Attenuation Results for Modeling Cases EVALUATION OF MOORING IMPACTS Tsunami Induced Water Level Variations Tsunami Induced Flow Velocities Comparison of Tsunami Induced Flow Velocities and Mooring Analysis SUMMARY AND CONCLUSIONS Discussion of Landslide Generated Tsunami Hazard Evidence of Past Tsunami Events Conclusions Landslide Scenarios Tsunami Wave Formation and Propagation Impacts to Berthed Vessels REFERENCES... 71

8 Westridge Marine Terminal Tsunami Assessment 6 LIST OF FIGURES Figure 1 1: Burrard Inlet, Vancouver, BC (Source: Wikipedia)... 9 Figure 1 2: Westridge Marine Terminal Site Location Figure 1 3: Rendering of Proposed Westridge Marine Terminal Expansion Figure 2 1: Tsunami Hazard Categorization, CGEN (2014, Natural Resources Canada, 2009) Figure 2 2: Sketch Showing Tsunami Generation from Submarine and Subaerial Landslide (Nieuwkoop, 2007) Figure 2 3: Landslides Categorized by Material and Movement Type, BGS Figure 2 4: Morphologic Features Identified in Multi beam Swath Bathymetry, GSC OF 7348 (2013) Figure 2 5: Aerial view of Burrard Inlet and Indian Arm, Landslide Locations 1 to 6, and Modeling Domain Figure 2 6: Slide Location 1 Elevation Profile Figure 2 7: Slide Location 2 Elevation Profile Figure 2 8: Slide Location 3 Elevation Profile Figure 2 9: Slide Location 4 Elevation Profile Figure 2 10: Slide Location 5 Elevation Profile Figure 2 11: Slide Location 6 Elevation Profile Figure 2 12: Primary Parameters Defining Impulse Wave Characteristics Figure 2 13: Tsunami wave attenuation as a function of direction and distance Figure 3 1: Model Bathymetry Figure 3 2: Landslide Scenario 1 Example of Time Varying Bed Level Displacement Input into MIKE 21 Model Figure 3 3: Snapshot Showing the Tsunami Wave Generation from MIKE 21 Model and Laboratory Tests of Bore Formation (Fritz, 2002) Figure 3 4: Plan view of initial wave height formation, Scenario 1 (left) and idealized bathymetry (right) Figure 3 5: Comparison of water surface elevation profiles for Slide Scenario 1 and idealized Test Case Figure 3 6: Comparison of MIKE 21 model tsunami wave length with Heller (2007) analytical method Figure 3 7: Comparison of MIKE 21 model tsunami wave height with Heller (2007) analytical method Figure 3 8: Comparison of MIKE 21 model tsunami wave amplitude with Heller (2007) analytical method Figure 3 9: Comparison of MIKE 21 model tsunami wave celerity with Heller (2007) analytical method... 39

9 Westridge Marine Terminal Tsunami Assessment 7 Figure 3 10: Comparison of MIKE 21 model tsunami wave period with Heller (2007) analytical method Figure 4 1: Model output locations Figure 4 2: Tsunami Wave Propagation Landslide Scenario Figure 4 3: Tsunami Wave Propagation Landslide Scenario 1A Figure 4 4: Tsunami Wave Propagation Landslide Scenario Figure 4 5: Tsunami Wave Propagation Landslide Scenario Figure 4 6: Tsunami Wave Propagation Landslide Scenario Figure 4 7: Definition of Model Result Statistics Figure 4 8: Time Series of Surface Elevation at Berth Figure 4 9: Time Series of Current Speed at Berth Figure 4 10: Time Series of Surface Elevation at Berth Figure 4 11: Time Series of Current Speed at Berth Figure 4 12: Time Series of Surface Elevation at Berth Figure 4 13: Time Series of Current Speed at Berth Figure 5 1: General Arrangement Plan for the Proposed Westridge Facilities Figure 5 2: Range of tsunami induced water level variations at Berth Figure 5 3: Range of tsunami induced water level variations at Berth Figure 5 4: Range of tsunami induced water level variations at Berth Figure 5 5: Magnitude and direction of maximum tsunami induced flow velocities Figure 5 6: East Burrard Inlet Mike21 model ebb current snapshot, (M&N, 2012) Figure 5 7: East Burrard Inlet Mike21 model flood current snapshot, (M&N, 2012) Figure 5 8: Comparison of tsunami induced flow velocities and OCIMF cases adopted in Berth 1 mooring analysis Figure 5 9: Comparison of tsunami induced flow velocities and OCIMF cases adopted in Berth 2 mooring analysis Figure 5 10: Comparison of tsunami induced flow velocities and OCIMF cases adopted in Berth 3 mooring analysis Figure 6 1: Comparison of slide scenarios investigated with slides recorded worldwide LIST OF TABLES Table 2 1: Characteristics of Morphological Features Table 2 2: Summary of Landslide Characteristics Table 2 3: Landslide Geometries Table 2 4: Subaerial Landslide Tsunami Wave Characteristics... 29

10 Westridge Marine Terminal Tsunami Assessment 8 Table 3 1: Modeling Cases and Sensitivity Tests Table 4 1: Tsunami Wave Attenuation Table 4 2: Summary of Results at Berth Locations Table 6 1: Tsunamigenic events in British Columbia in Recent History Table 6 2: Earthquake Risk, Recurrence, Peak Ground Acceleration, and Magnitude... 69

11 Westridge Marine Terminal Tsunami Assessment 9 1. INTRODUCTION 1.1 SITE DESCRIPTION Burrard Inlet is approximately 25 km long and extends east from the Strait of Georgia to Port Moody (Figure 1 1). The inlet is composed of the Outer Harbour, the Inner Harbour, the Central Harbour, and the Port Moody Arm. Indian Arm, a 20 km long steep sided glacial fjord, extends north from the main inlet. The waters of Burrard Inlet are sheltered from the open ocean, and the Outer Harbour and English Bay are utilized by vessels transiting to and from Vancouver and as anchorage for vessels waiting to discharge or take on cargoes. Infrastructure along the waterfront is primarily commercial and includes railyards, terminals for container and bulk cargo, grain elevators, and other industry. Much of the shoreline along Burrard Inlet is built out with mixed commercial and residential real estate. Along Indian Arm, the topography is steeper and the area is largely undeveloped. Figure 1 1: Burrard Inlet, Vancouver, BC (Source: Wikipedia)

12 Westridge Marine Terminal Tsunami Assessment 10 As a waterway, Burrard Inlet is connected to the Pacific Ocean via the Strait of Georgia. Water depths within the inlet range from approximately 16 to 44 meters on approach to the Westridge facility. The waters of Indian Arm are deeper ranging from 25 to 210 meters. The general bathymetry of Burrard Inlet and Indian Arm is detailed on the following Canadian Hydrographic Service (CHS) Nautical Charts: 3481 Approaches to Vancouver Harbour (1:25,000) 3311 Port Moody to Howe Sound (1:40,000) 3495 Indian Arm (1:30,000) The hydrodynamics of the inlet are influenced by the constrictions at First and Second Narrows. Both of the narrows are dredged to about m depth for navigation. Currents through the narrows can exceed 5 knots during spring tide flood and ebb phases. The First Narrows runs past Stanley Park between the Outer Harbour and the Inner Harbour. The Second Narrows is located between the Inner Harbour and the Central Harbour where Lynn Creek and the Seymour River meet the inlet. 1.2 PROJECT BACKGROUND The Trans Mountain Pipeline System (TMPL), which has been in operation since 1953 is a 1,150 km pipeline transporting crude oil and refined products to the west coast. The current capacity is approximately 300,000 barrels per day (bpd). The ongoing Trans Mountain Pipeline Expansion (TMX) Project focuses on expanding the capacity of the pipeline to 890,000 bpd. The expansion includes new pipeline, addition of pump stations along the pipeline, addition of storage tanks at existing facilities, and expansion of the Westridge Marine Terminal. The TMPL moves product from Edmonton, Alberta, to terminals and refineries in the central British Columbia region, the Greater Vancouver area and the Puget Sound area in Washington state, as well as to other markets such as California, the U.S. Gulf Coast and overseas through the Westridge Marine Terminal at Burnaby, BC. The location of the terminal is shown in Figure 1 2.

13 Westridge Marine Terminal Tsunami Assessment 11 Indian Arm Burrard Inlet Westridge Marine Terminal Port Moody Figure 1 2: Westridge Marine Terminal Site Location The Westridge marine terminal can accommodate barges, and vessels up to approximately 120,000 deadweight tons. In addition to shipping crude oil, the facility receives jet fuel for the Vancouver International Airport. The terminal facilities include three storage tanks with an overall capacity of 290,000 bbl. Kinder Morgan Canada (KMC) is in the process of expanding marine facilities at the Westridge Terminal, which includes the construction of three (3) new jetty berths capable of accepting vessels ranging from barges to Aframax tankers. Figure 1 3 shows a rendering of the proposed facility. Figure 1 3: Rendering of Proposed Westridge Marine Terminal Expansion

14 Westridge Marine Terminal Tsunami Assessment SCOPE OF WORK The present study provides a screening level assessment of landslide induced tsunami hazards to vessels berthed at the Kinder Morgan facility at Burnaby, BC, within the Eastern Burrard Inlet. 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 or further analysis if the tsunami waves are perceived to be significant enough to result in potential issues to berthed vessels.

15 Westridge Marine Terminal Tsunami Assessment DATA REVIEW This chapter summarizes findings of a literature review of prior tsunami studies for the area along with a categorization of landslides and locally generated tsunamis. Based on input from BGC Engineering, six potential subaerial landslide scenarios are investigated and evaluated by analytical methods. The findings are carried over to the numerical modeling effort detailed in Chapter 3 of the report. 2.1 TSUNAMIS FROM DISTANT SOURCES Canadian shorelines are exposed to tsunamis from a range of far field and near field sources. Distant far field sources include tsunamis generated by seismic events, volcanic activity, and landslides along the Pacific Rim, which includes (in a counter clockwise direction) Alaska, the Aleutian Islands, the Kuril Islands, Japan, the Philippines, New Zealand, South America, and North America. Hawaii, approximately in the center of the Pacific is also a potential source of tsunamis. Along the North American Shelf, the Cascadia Subduction Zone extends to the northern part of Vancouver Island, transitioning into the Queen Charlotte Fault further north. These subduction zones are capable of generating large tsunamis impacting nearshore areas and shores across the Pacific, (Clague et al., 2003). The primary exposure of the Lower British Columbia to tsunami hazards is along the Pacific seaboard of Vancouver Island, see Figure 2 1, excerpt from Natural Resources Canada (2009). In the Strait of Juan de Fuca south of Vancouver Island, and upon passage of the Gulf Islands to the north, tsunami amplitudes are reduced by about one half compared with the outer coast, as indicated by both model results and actual tsunamis observed on tide gauges (Leonard et al., 2012), and attenuate further as they enter the Strait of Georgia. Within the Strait of Georgia, tsunami hazards are low, with a run up potential of less than 2 meters. Figure 2 1 does not cover the eastern part of Burrard Inlet and Indian Arm, but it can be assumed that the primary tsunami hazards in these areas are associated with local landslide activity such as is the case for the other fjords included in the figure. This study therefore focuses on landslide generated tsunamis.

16 Westridge Marine Terminal Tsunami Assessment 14 Figure 2 1: Tsunami Hazard Categorization, CGEN (2014, Natural Resources Canada, 2009) 2.2 CATEGORIZATION OF LANDSLIDES Landslides can be categorized into two broad categories, namely submarine landslides and subaerial landslides. Submarine landslides are initiated beneath the surface of the water, while subaerial landslides are initiated above the water and impact the water body during their progression or fall into the water body. The movement of a large slide mass or the impact of the fall displaces the water in the direction of the movement and can lead to generation of a tsunami wave on the surface of the water body. A classic example occurred in Lituya Bay in Alaska, where an earthquake in 1958 triggered a large rock slide that fell into the bay and produced a runup on the opposite shore up to a height of 525 m above sea level (Clague et al., 2003). Another example occurred in 2007 at Chehalis Lake, located 80 km east of Vancouver. In that event, an estimated three million cubic meters of rock broke away from a mountain and slid into the water. Across from the slide on the opposite shore, the tsunami reached 37.8 meters up the slope. Figure 2 2 presents a sketch showing differences in tsunami generation between a submarine and subaerial landslide (Nieuwkoop, 2007). For a submarine landslide, a depressions of the water surface is generated behind the landslide while a superelevation of the water surface is created ahead of the landslide. For a subaerial landslide, the water surface is only elevated ahead of the impact location. Once the initial wave field is formed, it propagates outward from the source region. Therefore, the first wave front which reaches the adjacent coast is a trough for a submarine landslide and a crest for a subaerial landslide.

17 Westridge Marine Terminal Tsunami Assessment 15 The present report focuses on subaerial landslide scenarios. Figure 2 2: Sketch Showing Tsunami Generation from Submarine and Subaerial Landslide (Nieuwkoop, 2007) There are several types of subaerial landslide mechanisms to consider as summarized in Figure 2 3. The current classification of landslides by the British Geological Survey (BGS) follows the scheme based on Varnes, 1978 and Cruden et al, This scheme terminology is also suggested by the Unesco Working Party on the World Landslide Inventory (WP/WLI 1990, 1993). The cause of such landslides can vary greatly, and triggering mechanisms can include seismic events, hydrostatic pressure or hydrodynamic forcing (e.g. from heavy rainfall), other external loading, and human activities such as construction or blasting. The primary aspects of tsunami formation are discussed in the following. The tsunami wave height is known to increase with the speed of the landslide impact at the water surface. Therefore subaerial landslides generally produce larger tsunami waves than submarine landslides of similar volumetric magnitude. In general, the steeper the slope, the faster the speed of impact. The density and coherence of the landslide affects tsunami wave height generation. Therefore a large block will tend to produce a larger tsunami wave height than a granular mix of material having a more distributed mass and lower bulk density.

18 Westridge Marine Terminal Tsunami Assessment 16 Figure 2 3: Landslides Categorized by Material and Movement Type, BGS

19 Westridge Marine Terminal Tsunami Assessment 17 Regarding the volume of water displaced, formation of a tsunami wave depends greatly on the characteristics of the time history of ground displacement relative to the surrounding mass of water. Therefore seismic uplift, such as during fault rupture in subduction zones, is one of the primary tsunami hazards because of the potentially large, rapid vertical displacements occurring over a large area. Within Burrard Inlet and along the steep sides of the Indian Arm, distanced from primary fault lines, the primary tsunami hazard is due to subaerial landslides. 2.3 LOCALLY GENERATED TSUNAMIS This section summarizes findings about past landslide activity in Burrard Inlet and Indian Arm and the potential subaerial landslide scenarios adopted for the analysis. As a general statement categorizing potential tsunami activity in Indian Arm, Clague et al. (2005) notes that the probability of a landslide triggered tsunami in Indian Arm is very low. This, because no such event has occurred since the time of European settlement more than 150 years ago, and no slopes bordering the fjord are known to be unstable. GSC OF 7348 (2013) evaluates CHS swath multi beam bathymetric survey data and identifies numerous areas within Indian Arm exhibiting indications of past and potential landslide activity, including fan delta formations; translational slides; submarine alluvial fan/composite slides; debris flows and turbidity current channels, gullies and lobes; and undifferentiated slides. Figure 2 4 summarizes submarine slope failure types and morphologic features from GSC OF 7348 (2013) for Burrard Inlet and Indian Arm. Areas of green color indicate debris flows, purple areas are fan deltas, blue areas represent submarine alluvial fans and composite slides, red areas indicate translational slides, and yellow areas represent undifferentiated slides. The classifications can be categorized as follows: Debris flows include turbidity current channels, gullies, and debris flow depositional lobes. Debris flows, often categorized as mudslides, mudflows, or debris avalanches are fluid sediment masses that flow as an unsteady, very poorly sorted sediment slurry. These flows typically do not produce tsunami waves. Fan deltas are characterized by fan shaped deposits often channelized with several types of landslide deposits. The fan deltas consist of sediments derived from an alluvial fan feeder system and deposited mainly or entirely subaqueously at the interface between the active fan and a standing body of water. Fan deltas are constructed by a combination of slope instability processes including debris flows, debris avalanches, turbidity flows and materials settling from suspension. Burrard Inlet has several moderate sized fan deltas and alluvial fans entering from large watersheds. Examples of these are denoted by (A) in Figure 2 4. The formation of fan deltas

20 Westridge Marine Terminal Tsunami Assessment 18 does commonly not produce tsunami wave activity, although the buildup of unstable deposits may have the potential for subsequent failure and submarine slide activity, which may or may not produce a tsunami wave. Submarine alluvial fans/composite slides describe complex slides resulting from several events associated with a submarine channel or channels, but where no single, dominant river sediment source is apparent. Submarine alluvial fan/composite slides are distinguished from fan deltas by the lack of a permanent river source and are interpreted to indicate ongoing slide activity of significant magnitude. Depending on the speed of movement and magnitude of the slide mass, slides of this type may produce tsunami wave activity. Translational slides comprise slides where the landmass moves along an approximately planar surface with little rotation or backward tilting. The moving mass typically consists of a single unit or a few closely related units that have moved downslope as a relatively coherent mass. Examples of pronounced translational slides are indicated with (B and C) in Figure 2 4. Depending on the speed of movement and magnitude of the slide mass, slides of this type may produce tsunami wave activity. Undifferentiated slides cover slides where downslope displacement in a single event is evident, but where the form of the slide plane cannot be unambiguously determined, and the planar or rotational aspect of slides has been difficult to establish from the multi beam data. Table 2 1 summarizes the characteristics of the identified submarine morphological features in terms of their planar extent. It can be seen that debris flows are limited in terms of number and size, while deltaic deposits make up the majority of the identified features (14+8), ranging in size from 2,900 m 2 to 721,000 m 2. The types of slides having the potential to displace water rapidly enough to possibly produce a wave include the translation and undifferentiated slides, which are relatively limited in number (6+3) and extent. Table 2 1: Characteristics of Morphological Features Morphological Feature Count Planar Extent Debris Flows 2 ~ 29,300 m 2 Fan Deltas 14 12,500 to 721,000 m 2 Submarine Alluvial Fans 8 2,900 to 443,000 m 2 Translational Slides 6 13,800 to 70,900 m 2 Undifferentiated Slides 3 10,100 to 59,500 m 2 Slope failure types such as rotational slides; rock avalanches; bedrock creep; and cones have not been identified in Burrard Inlet and Indian Arm.

21 19 Westridge Marine Terminal Tsunami Assessment Figure 2 4: Morphologic Features Identified in Multi beam Swath Bathymetry, GSC OF 7348 (2013) Kinder Morgan Canada Trans Mountain Expansion Project March 26, 2015

22 Westridge Marine Terminal Tsunami Assessment Subaerial Landslide Scenarios BGC Engineering Inc. has developed the landslide scenarios adopted as a basis for the present analysis. Figure 2 5 shows the location of potential landslide scenarios 1 through 6 along Indian Arm and Burrard Inlet. The slide scenarios and slide characteristics are summarized in Table 2 2. The slide scenarios are hypothetical but representative of locations where slope instabilities could occur or have happened in the past. Table 2 2: Summary of Landslide Characteristics Slide Location Planar Extent (m 2 ) Volume (m 3 ) Azimuth ( N) 1 328,408 36,483, ,818 2,678, ,126 24, ,043 12,828, ,287 9,300, , , Figure 2 6 through Figure 2 11 show the elevation profiles at slide locations 1 to 6. Topographic data shown is based on CDEM data, while bathymetric data is based on NOAA data. The vertical datum is Mean Sea Level. The elevation profile at the shoreline is approximate where data has been interpolated between data sets. In the figures, the black line represents the profile of the fjord wall above water, while the blue line represents the (seabed) portion below water. The horizontal and vertical scales on the figures are approximately equal. The slide extents are indicated in red with the failure plane indicated by a dash dot line. The failure planes are for visualization only, and consequently the slide centroid locations are approximate.

23 Westridge Marine Terminal Tsunami Assessment 21 Figure 2 5: Aerial view of Burrard Inlet and Indian Arm, Landslide Locations 1 to 6, and Modeling Domain

24 Westridge Marine Terminal Tsunami Assessment 22 Figure 2 6: Slide Location 1 Elevation Profile Figure 2 7: Slide Location 2 Elevation Profile

25 Westridge Marine Terminal Tsunami Assessment 23 Figure 2 8: Slide Location 3 Elevation Profile Figure 2 9: Slide Location 4 Elevation Profile

26 Westridge Marine Terminal Tsunami Assessment 24 Figure 2 10: Slide Location 5 Elevation Profile Figure 2 11: Slide Location 6 Elevation Profile Table 2 3 summarizes the overall dimensions of the respective landslide geometries. In the table, the distance is the planar runout distance from the center of the slide origin to the water s edge. The elevation is the height of the slide centroid relative to the water level. The slope or declination, taken as the ratio of the elevation to the runout distance, is a measure of

27 Westridge Marine Terminal Tsunami Assessment 25 the tsunami potential in relation to the potential energy attributed to the elevated slide mass. The steeper the slope the greater the component of gravitational acceleration affecting the slide mass, while the longer the distance the greater the frictional retardation of the slide. Table 2 3: Landslide Geometries Slide Scenario Distance Elevation Slope (m) (m) (V:H) Width (m) Length (m) : , : : : , : : It can be seen that the terrain at slide locations 3 and 6 is relatively flat (Figure 2 8 and Figure 2 11). It is anticipated that slides at these two locations would take the form of a slump, rotational slide, debris flow or mud flow (Figure 2 3), but with insufficient momentum to impact the water and produce a tsunami wave. 2.4 DEVELOPMENT OF LANDSLIDE PARAMETERS Heller et al. (2009) have developed analytical relations that describe the overall characteristics of tsunami waves generated upon impact from subaerial landslides. Figure 2 12 defines the primary parameters characterizing the initial wave formed upon impact of the slide mass. Figure 2 12: Primary Parameters Defining Impulse Wave Characteristics.

28 Westridge Marine Terminal Tsunami Assessment 26 Parameters characterizing the tsunami wave formation include the maximum wave height,, the maximum wave amplitude, and wave propagation along the radial distance at planar angle and water depth. Additional parameters characterizing the tsunami wave include the wave period, the wave length, and the speed of propagation (celerity). The parameters defining the characteristics of the subaerial landslide include the width, the slide thickness, the bulk slide density, the porosity, the slide mass, the bulk slide volume V S, and the impact velocity at impact angle. Heller et al. (2009) relate the subaerial landslide impact parameters via the impulse product parameter: 6 7 Where is the slide Froude number, is the relative slide thickness, is the relative slide mass, and is the slide impact angle defined in Figure The dimensionless quantities are defined as follows: The tsunami wave height as a function of distance from the impact and propagation angle is given by:, Where is the impulse product parameter, is the water depth, and is the relative distance of maximum wave amplitude from the impact location. The term: describes wave attenuation as a function of angle, and radial distance as defined in Figure Figure 2 13 provides a view of the tsunami wave attenuation as a function of direction and distance. At the initial wave formation at the back wall, the wave height is 100% at the peak. The figure shows subsequent attenuation with distance to the sides and front. Because of the forward momentum of the landslide at impact, the attenuation is less in the direction of the impact and more pronounced on the sides.

29 Westridge Marine Terminal Tsunami Assessment 27 Figure 2 13: Tsunami wave attenuation as a function of direction and distance The corresponding wave period is given by:, 15 Where is the tsunami wave height, is the water depth, and the gravitational acceleration. Additionally, per (Heller et al., 2009), the tsunami wave height is proportional to the base parameters as follows:.,.,.,.,. This shows that the tsunami wave height is nearly linearly proportional to the slide impact velocity and to a lesser extent the slide thickness and the slide volume. It can also be seen that the tsunami wave height increases proportionally with water depth, and decreases with radial distance from the impact. The governing parameter is the slide impact velocity which is given by (Heller et al., 2009): 2 1 tan cot

30 Westridge Marine Terminal Tsunami Assessment 28 Where is the gravitational acceleration, is the drop height of the center of gravity of the slide, is the dynamic bed friction angle, and is the slide impact angle (Figure 2 12). The first part of the equation describes the free fall velocity determined by equating the kinetic energy of the moving slide to the corresponding energy potential of the slide, i.e. 1 2 Where the mass of the slide,, cancels out and the free fall velocity emerges as 2. The latter term in the impact velocity equation moderates the free fall velocity by accounting for friction. Consequently, as the dynamic bed friction angle approaches that of the overall slope, the impact speed diminishes. If the dynamic bed friction is greater than the slope angle, the weight of the slide mass won t be able to overcome the frictional resistance and the slide doesn t occur. The value of the dynamic bed friction angle can range from 15 35, and a value of 20 may be assumed irrespective of whether the slide mass consists of rock, ice or snow, although the friction angle in reality may have a significant impact on the speed of the slide. 2.5 ASSESSMENT WITH ANALYTICAL APPROXIMATION Based on the work of Heller et al. (2009), a rudimentary assessment of the potential tsunami wave characteristics can be made. Table 2 4 summarizes estimated parameters characterizing the potential tsunami waves for the adopted slide scenarios. The water depth is representative of the approximately deepest depth along the heading of the slide trajectory. The propagation angle represents the planar angle of wave propagation down Indian Arm or along shore in Burrard Inlet toward the project site. The angle is defined in Figure 2 12 with zero degrees being perpendicular to the shoreline.

31 Westridge Marine Terminal Tsunami Assessment 29 Slide Scenario Table 2 4: Subaerial Landslide Tsunami Wave Characteristics Water Depth (m) Propagation ( ) H (m) a (m) T (s) c (m/s) L (m) , , , , The characteristic wave height of the initial tsunami wave is denoted by H in Table 2 4 and is measured as the height from trough to crest as defined in Figure The amplitude of the tsunami wave, measured from the still water level to the crest of the initial wave is denoted by a in Table 2 4. The wave period associated with the tsunami wave is labeled T, and the corresponding wave length, L. The speed of propagation, termed the celerity is given as c = L/T. It can be seen that anticipated wave lengths are typically on the order of 1½ to 2 kilometers, while slide scenarios 3 and 6 would not be expected to produce tsunami waves. The speed of propagation is directly related to water depth and is therefore lower at sites with shallower water depths. In general, the slides exhibit propagation speeds on the order of 40 m/s. The tsunami wave heights and amplitudes are more varied as these are dependent on the multitude of parameters summarized in Table 2 2, Table 2 3, and Table 2 4. It should be noted that the parameters summarized in Table 2 4 represent only one estimate of the characteristic tsunami wave parameters whereas another basis of assumptions would lead to other estimates.

32 Westridge Marine Terminal Tsunami Assessment DEVELOPMENT OF NUMERICAL MODEL 3.1 MIKE 21 HYDRODYNAMIC MODEL M&N had developed a two dimensional (2D) DHI MIKE 21 Hydrodynamic Model as part of the Metocean Study in 2012 (M&N, 2012). The existing modeling domain was extended to include the extent of the Indian Arm for the tsunami assessment. The 2D Hydrodynamic Model solves the depth averaged shallow water equations and simulates water level variations and flows in response to a variety of forcing functions (DHI, 2012). The unstructured mesh consists of nearly 505,000 triangular elements. A uniform, high resolution mesh size (approximately meters in length) was used in order to minimize numerical diffusion and avoid underestimation of wave amplitudes. 3.2 MODEL BATHYMETRY & TOPOGRAPHY Three sources of bathymetry and topography were compiled for the tsunami modeling. Bathymetry (or seabed elevations) for the majority of the modeling domain was extracted from the C Map Software of DHI, incorporating Jeppesen Norway s electronic database of global nautical charts. Bathymetry in close vicinity of the TMEP project site was based on an underwater survey by Golder. Land topography behind and around the site was also included to an elevation of 30 meters above mean sea level (Natural Resources Canada, 2013). Figure 3 1 shows the model bathymetry, referenced to mean sea level (MSL). 3.3 BOUNDARY CONDITIONS The modeling domain contains one water boundary, west of the Ironworkers Memorial Second Narrows Bridge (Figure 3 1). Typically, boundary conditions are required to apply physical forcing into the modeling domain through the water boundaries. However, because the run time of tsunami simulation was expected to be much shorter than a typical tidal circulation simulation, the water boundary was implemented as a closed boundary. After some initial runs, it was found that tsunami waves reach the TMEP site within 30 minutes or less so that the variation of tidal levels and tide induced currents within the simulation runtime are not significant. In addition, wind does not contribute to tsunami propagation. Therefore, these elements are not considered in the simulation.

33 Westridge Marine Terminal Tsunami Assessment 31 Figure 3 1: Model Bathymetry 3.4 MODELING APPROACH The above surface portion of the landslide was based on the work of Heller et al. (2009), as summarized in Section 2.4. As the front of the landslide hits the water surface, the effect of the landslide is simulated by generating a time varying bed level displacement. Subsequently, the below surface portion of the landslide motion follows the work of Watts (1998) and Grilli et al. (2005). Figure 3 2 shows a sequence of time varying bed level displacement file used in the model. Figure 3 3 illustrates snapshots of the profile across Indian Arm at 15, 20, and 25 seconds after initiation of Landslide Scenario 1. A bore of water rises and propagates with the landslide

34 Westridge Marine Terminal Tsunami Assessment 32 movement. The phenomenon is similar to the laboratory results from Fritz, 2002 illustrated in the black and white photos included to the right in Figure 3 3. Figure 3 2: Landslide Scenario 1 Example of Time Varying Bed Level Displacement Input into MIKE 21 Model

35 Westridge Marine Terminal Tsunami Assessment 33 Figure 3 3: Snapshot Showing the Tsunami Wave Generation from MIKE 21 Model and Laboratory Tests of Bore Formation (Fritz, 2002) 3.5 MODELING CASES Table 3 1 lists the modeling cases conducted in this Tsunami Study. Some general assumptions for the simulation were made as follows: A box shape for the above water mass of landslide was assumed. As a result, the corresponding landslide thickness equals the landslide volume divided by the landslide length and width, as listed in Table 2 3.

36 Westridge Marine Terminal Tsunami Assessment 34 The landslide comes down the mountain slope as a block and no landslide transformation occurs in the process. This is a conservative assumption and should be verified with the Project Geologist. Mean sea level (MSL) was selected as the water level. MSL is 3.1 meters above Chart Datum (CD). A dynamic bed friction angle of 20 degrees was assumed. Because Landslide Scenario 1 has the largest volume, it was further investigated for sensitivity tests, including reduction of the landslide thickness by half, at Higher High Water Large Tide (HHWLT, 5.1 m above CD) and at Lower Low Water Large Tide (LLWLT, 0.1 m below CD), and a dynamic bed friction angle of 35 degrees. Generally, the dynamic bed friction angle can range from Table 3 1: Modeling Cases and Sensitivity Tests Landslide Scenario Landslide Thickness (m) Tide Level Bed Friction Angle (degree) Modeling Cases based on General Assumptions 1 69 MSL MSL MSL MSL 20 Sensitivity Tests on Landslide Scenario 1 1A 35 MSL 20 1B 69 HHWLT 20 1C 69 LLWLT 20 1D 69 MSL COMPARISON WITH ANALYTICAL APPROXIMATIONS Based on Landslide Scenario 1, a comparison was made between the analytical solution methods provided in Heller (2007) and the MIKE 21 numerical model runs. Despite the landslide characteristics being the same between the analytical estimates and the MIKE 21 numerical model, initial runs with the MIKE 21 model revealed that the initial tsunami wave formation was highly dependent on the bathymetry at the slide impact location. This is because the volume of the slide is comparable to the volume of the surrounding water body. For a slide of this magnitude, it turns out that the width across Indian Arm (approximately 1.5 km across at the location of slide scenario 1) becomes a limiting factor in the maximum wave height formation, whereas an unrestricted landslide impact would develop more uniformly.

37 Westridge Marine Terminal Tsunami Assessment 35 In order to facilitate comparison between the numerical model and the analytical solution provided in Heller (2007), an idealized slide impact scenario was developed in which the water depth was fixed at 140 m and the water body unrestricted (western shore omitted). Figure 3 4 provides a plan view comparing wave formation for Scenario 1 and the idealized Test Case. Figure 3 4: Plan view of initial wave height formation, Scenario 1 (left) and idealized bathymetry (right). Figure 3 5 illustrates differences between the model with the actual Indian Arm bathymetry and the idealized Test Case with open water and constant water depth of 140 m. The solid and dotted blue lines represent profiles of the water surface elevation at two example time steps five seconds apart. The yellow solid and dotted lines represent the corresponding profiles from the idealized Test Case, elevation profiles five seconds apart. The following differences between the models are apparent. In the case of the idealized bathymetry for the Test Case, the tsunami wave front forms as a distinct wave crest with a wide shallow trough in its wake continuing into a second crest and trough (wave propagation is from

38 Westridge Marine Terminal Tsunami Assessment 36 left to right). The water volume is balanced so that the amount of water in the wave crest (above Mean Sea Level) corresponds to the volume of the trough in its wake. Comparing with Scenario 1, reflecting the actual bathymetry of Indian Arm, the wave fronts occur at differing distances. This is because the wave propagation speed (celerity) is nonuniform in the case of the real bathymetry, which has varying water depth leading to variations in the speed of wave propagation. Also, undulations of the water surface are apparent for Scenario 1 compared to the idealized Test Case. This occurs due to reflection from the shores of Indian Arm, which can be considered to be relatively narrow, 1.1 to 1.8 km, compared to the tsunami wave length, which is on the order of 1.4 to 2.1 km. The most apparent reflection occurs around the initial slide impact location around 0 to 300 m, where reflection from the opposite shore results in an increase of the wave height due to superposition of the wave radiating out from the impact location and the waves reflected back from shore and the surrounding bathymetry. Figure 3 5: Comparison of water surface elevation profiles for Slide Scenario 1 and idealized Test Case Analytical/Numerical Model Comparison In the following, the tsunami wave characteristics predicted by the analytical model, Heller (2007), are compared with output from the MIKE 21 model idealized Test Case. The primary tsunami characteristics considered include the wave length, wave height, wave amplitude, wave celerity, and wave period. The findings are presented in Figure 3 6 to Figure Figure 3 6 shows the analytical/numerical model data for tsunami wave length as a function of propagation distance. The area highlighted in green bounded by the green dotted lines represents the range of wave lengths predicted by the analytical model, Heller (2007). The

39 Westridge Marine Terminal Tsunami Assessment 37 lower bound reflects the wave length of the tsunami wave radiating at angle (refer to Figure 2 12), while the upper bound represents the wave length of the maximum wave propagating at the azimuth of the slide. It can be seen that the numerical model results (yellow circles) are in line with the analytical model predictions and close to the results for the wave propagating at angle, which in this case is down Indian Arm. 3,000 Tsunami Wave Length (m) 2,500 2,000 1,500 1, ,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 Distance (m) Figure 3 6: Comparison of MIKE 21 model tsunami wave length with Heller (2007) analytical method Figure 3 7 compares the tsunami wave height computed with the numerical model with the range of wave heights predicted by the analytical model. Again the lower dotted line reflects results for wave propagation at angle, while the upper dotted line is representative of the maximum wave. Again, it can be concluded that the numerical model (yellow circles) produces results that are in line with the analytical model prediction.

40 Westridge Marine Terminal Tsunami Assessment Tsunami Wave Heigth (m) ,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 Distance (m) Figure 3 7: Comparison of MIKE 21 model tsunami wave height with Heller (2007) analytical method Figure 3 8 compares the tsunami wave amplitude computed with the MIKE 21 model with that of the Heller (2007) analytical model. In the analytical model the wave amplitude is given simply as: 4 5, i.e. 80% of the wave height. The numerical model results confirm this relationship Tsunami Wave Amplitude (m) ,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 Distance (m) Figure 3 8: Comparison of MIKE 21 model tsunami wave amplitude with Heller (2007) analytical method Figure 3 9 compares the speed of tsunami wave propagation (celerity) as computed by the analytical and numerical models. The range of propagation speeds (yellow area) predicted by the analytical model is bounded by the upper and lower dotted lines, representative of the maximum wave and the wave front radiating at angle.

41 Westridge Marine Terminal Tsunami Assessment 39 Tsunami Wave Celerity (m/s) ,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 Distance (m) Figure 3 9: Comparison of MIKE 21 model tsunami wave celerity with Heller (2007) analytical method The numerical model results are indicated by the red circles, and are within the range of predicted by the analytical model. Compared with the previous results, substantial scatter is seen in the results. This is related to uncertainties in developing the wave celerity from numerical model output, which is taken as the distance of propagation of the wave front over a time step, approximately by:. For comparison, the theoretical wave celerity is indicated by the dark grey line. Per Heller (2007), the tsunami wave propagation is governed by the dispersion relation: 2 2 Where is the wave celerity, is the gravitational acceleration, is the water depth, and is the wave length. In the case of a shallow water wave, which is characteristic of tsunami wave propagation, the above equation reduces to: Which expresses that the tsunami wave length is much greater than the water depth, 1 20 (shallow water wave). This is the reason why the speed of tsunami wave propagation is wholly governed by the water depth and bathymetric features of the sea floor. The above equation also expresses that when the tsunami wave amplitude is large, it contributes to the water depth via the term, whereas for a conventional small amplitude shallow water wave, the celerity would be given by.

42 Westridge Marine Terminal Tsunami Assessment 40 Finally, Figure 3 10 shows how the MIKE 21 numerical model output compares with the analytical method in terms of the tsunami wave period. In both cases, the wave period is determined from the relation: Where is the wave length, is the wave period, and is the wave celerity. Heller (2007), based on data for the wave period and wave celerity, utilizes the above relation to determine tsunami wave length Tsunami Wave Period (s) ,200 1,400 1,600 1,800 2,000 2,200 2,400 2,600 Distance (m) Figure 3 10: Comparison of MIKE 21 model tsunami wave period with Heller (2007) analytical method

43 Westridge Marine Terminal Tsunami Assessment SUMMARY OF MODEL RESULTS Findings from the numerical modeling are summarized in the following. Results for the four landslide scenarios that lead to tsunami wave formation are described in terms of tsunami wave formation and wave propagation, and wave attenuation on a regional scale, covering the area of Indian Arm and Burrard Inlet. Additionally, detailed results are provided at the project site in terms of the exposure of the berths to tsunami waves and tsunami induced currents. Three of four sensitivity tests show that there are nearly no differences by varying tidal levels and the dynamic bed friction angle (1B through 1D). Only the case with half of the thickness (1A) shows a significant reduction of tsunami waves at the project site. Therefore, the results for 1B, 1C, and 1D were not considered further in the study. Figure 4 1 shows the model output locations at Berth 1 through Berth 3. Figure 4 1: Model output locations

44 Westridge Marine Terminal Tsunami Assessment TSUNAMI WAVE PROPAGATION Results for tsunami wave propagation are provided in Figure 4 2 to Figure 4 6 for landslide scenarios 1, 1A, 2, 4 and 5. Figure 4 2 summarizes results for Landslide Scenario 1, which is representative of the largest slide volume amongst the cases investigated. Tsunami wave formation and subsequent wave propagation is illustrated across six snapshots at progressive time intervals. A time step shortly after the initial impact is shown in the upper left figure, and select time steps showing tsunami wave propagation are provided in the following images from left to right, ending with a snapshot of the tsunami wave propagation as it enters the vicinity of the project site. Each time step corresponds to a real time, of 5 seconds. In the figures, the light blue color represents the (undisturbed) still water level. Shades of red indicate positive water level displacement (wave crests), while shades of darker blue indicate lowering of the water level (wave troughs). Because the wave height variation from the point of impact to the project site is substantial, the vertical scale is fixed to capture water level variations within 2 meters only in order to emphasize wave crests and troughs. In the top left image of Figure 4 2 it can be seen that the initial slide impact produces a near circular wave front which radiates out from the site of the landslide. The water depth is fairly deep in this part of Indian Arm and wave propagation proceeds swiftly across and down Indian Arm. In the second image, top right, it can be seen that the initial tsunami wave front starts propagating down Indian Arm with two wave fronts also propagation north. It can also be noted that the initial wave front at this time has reached the opposite shore across from the landslide impact site. The proportion of the landslide parameters to the water depth is such that the tsunami wave takes the form of a solitary wave or bore, which can be characterized by having most of the wave front in a crest above the mean sea level and a wide, shallow trough in the wake of the wave crest. Examples of typical wave profiles can be seen in Figure 3 5. The following two images, center left and right, capture progression of the tsunami wave front down Indian Arm. It can be noted that the initial wave front stretches out into a wider wave front. In the wake of the tsunami, the water motion is characterized by sloshing which occurs because tsunami wave components are reflected off the shoreline and back into the fjord. This is in contract to e.g. tsunami wave propagation in the open ocean where a radial pattern of wave propagation would be expected. The bottom left image shows tsunami wave propagation just as the wave front passes Belcarra and Deep Cove. From this point on, the tsunami wave propagation is subject to a considerable slowdown, this because the wave propagation speed (celerity) is solely dependent on the water depth. Water depths around the central portion of Indian Arm reach 100 to 200 meters, as deep as 250 meters in some areas. In contrast, the water depth at Belcarra and

45 Westridge Marine Terminal Tsunami Assessment 43 Deep Cove and into Burrard Inlet is limited to meters. The last figure, bottom right, shows that as the tsunami wave front enters Burrard Inlet, the wave front disperses somewhat with two remnants of the wave front headed east and west, respectively. Figure 4 3 shows the same sequence for Scenario 1A, which reduces the thickness of Landslide Scenario 1 by half. The wave formation and propagation is similar to Scenario 1.

46 Westridge Marine Terminal Tsunami Assessment 44 Figure 4 2: Tsunami Wave Propagation Landslide Scenario 1

47 Westridge Marine Terminal Tsunami Assessment 45 Figure 4 3: Tsunami Wave Propagation Landslide Scenario 1A

48 Westridge Marine Terminal Tsunami Assessment 46 The sequence of tsunami wave formation and propagation for Scenario 2 is shown in Figure 4 4. The landslide volume for this scenario is about an order of magnitude lower than Scenario 1 shown previously. The proportion of the landslide relative to the water body is therefore such that the tsunami wave takes the form of a weakly non linear oscillatory wave. The top left and right images showing initial tsunami wave formation and propagation therefore show a more radial progression of the leading wave front with subsequent troughs and crests in its wake. As described for Scenario 1, as tsunami wave components arrive at the shoreline, reflection occurs, which causes the wave field to become scattered. Because of the limited slide volume, the tsunami attenuates earlier on its path down Indian Arm, and remnants of the tsunami waves are not noticeable in the lower part of Indian Arm past Belcarra and Deep Cove. Diagrams of tsunami wave attenuation can be found in Appendix A. Wave attenuation coefficients for the project site for the cases investigated are summarized in Table 4 1.

49 Westridge Marine Terminal Tsunami Assessment 47 Figure 4 4: Tsunami Wave Propagation Landslide Scenario 2

50 Westridge Marine Terminal Tsunami Assessment 48 Figure 4 5 shows landslide tsunami formation and propagation for Scenario 4. The landslide volume for this scenario is about one third of Scenario 1 and thus comprises a substantial slide mass. The proportion of the landslide relative to the water body means that the tsunami wave has characteristics of a weakly non linear oscillatory wave to intermediate solitarylike wave transition. The sequence of tsunami wave formation and propagation for Scenario 4 is shown in Figure 4 5. As seen for the other cases, the wave field quickly becomes scattered due to wave reflection along the shoreline. Again, the bathymetry at Belcarra and Deep Cove acts as a choke point, and only a limited remnant of the tsunami wave front propagation is noticeable east and west in Burrard Inlet. Likewise, a barely noticeable wave front propagates north along Indian Arm. Figure 4 6 shows tsunami formation and propagation for landslide Scenario 5. The landslide volume for this scenario is about one fourth of Scenario 1 and comparable to that of Scenario 4, representative of a fairly substantial slide mass. The proportion of the landslide relative to the water depth in the fjord places the tsunami wave with characteristics of a transitional solitary wave. The sequence of tsunami wave propagation for Scenario 5 is shown in Figure 4 6. It can be seen that the wave height variation is substantial in the vicinity of the slide impact site due to wave reflection and wave interaction with the complex topography of the area. Due to the long propagation distance (around 17 km), the wave is subject to considerable attenuation on its path down Indian Arm and only a limited portion of the leading wave travels east and west in Burrard Inlet.

51 Westridge Marine Terminal Tsunami Assessment 49 Figure 4 5: Tsunami Wave Propagation Landslide Scenario 4

52 Westridge Marine Terminal Tsunami Assessment 50 Figure 4 6: Tsunami Wave Propagation Landslide Scenario 5

53 Westridge Marine Terminal Tsunami Assessment TSUNAMI WAVE ATTENUATION Tsunami wave attenuation data are summarized in Table 4 1. The attenuation is a measure of the reduction of the tsunami wave height, measured as the ratio of wave height at the project site relative to the initial wave height at the site of each landslide. Figures indicating wave attenuation are provided in Appendix A. Table 4 1: Tsunami Wave Attenuation Landslide Scenario Tsunami Wave Attenuation % 1A 3.5 % % % % The results show that tsunami wave heights at the project site amount to only 1 to 3.5% of the initial wave height at the slide locations. 4.3 RESULTS FOR MODELING CASES Statistics for modeling results during the 30 minute simulation times are provided in Table 4 2, including the maximum and minimum surface elevation, maximum tsunami wave height, approximate tsunami wave period, and maximum current speed. Figure 4 7 presents an example of a time series of surface elevation. Maximum tsunami wave height is determined from the largest difference between a crest and a preceding trough, or vice versa. Because the corresponding tsunami wave period is not easily defined, a simple Fourier filtering (a toolbox in DHI MIKE 21) was performed and the frequency (reverse of period) of the corresponding peak energy was used to identify tsunami wave periods. Time series of surface elevations and current speeds at each of the berth at the project site is provided in Figure 4 8 through Figure 4 13.

54 Westridge Marine Terminal Tsunami Assessment 52 Table 4 2: Summary of Results at Berth Locations Landslide Scenario Berth 1 Berth 2 Berth 3 Maximum Surface Elevation (m, MSL) A Minimum Surface Elevation (m, MSL) A Maximum Wave Height (m) A Approximate Wave Period (s) A > 300 > 300 > 300 Maximum Current Speed (knots) A

55 Westridge Marine Terminal Tsunami Assessment 53 Figure 4 7: Definition of Model Result Statistics

56 Westridge Marine Terminal Tsunami Assessment 54 Figure 4 8: Time Series of Surface Elevation at Berth 1 Figure 4 9: Time Series of Current Speed at Berth 1

57 Westridge Marine Terminal Tsunami Assessment 55 Figure 4 10: Time Series of Surface Elevation at Berth 2 Figure 4 11: Time Series of Current Speed at Berth 2

58 Westridge Marine Terminal Tsunami Assessment 56 Figure 4 12: Time Series of Surface Elevation at Berth 3 Figure 4 13: Time Series of Current Speed at Berth 3

59 Westridge Marine Terminal Tsunami Assessment EVALUATION OF MOORING IMPACTS The planned berths at the project site are numbered from west to east, as shown in Figure 5 1, with Berths 1 and 2 in a back to back configuration, which share three (3) outboard mooring dolphins. The loading platform of Berth 1 is located more outboard than Berth 2, and Berth 1 and 2 do not share aft mooring dolphins as the pipe racks and walkways interfere with such an arrangement. Berth 3 represents the western most berth of the proposed expansion plan and has a mooring arrangement identical to that of Berth 2. Figure 5 1: General Arrangement Plan for the Proposed Westridge Facilities 5.1 TSUNAMI INDUCED WATER LEVEL VARIATIONS Tsunami induced water level variations were output from the numerical model simulations at each of the three berths. The data was extracted at the approximate center of vessels moored at the berth. Figure 5 2 to Figure 5 4 summarize the tsunami induced water level variations output from the investigated landslide scenarios. Positive values on the vertical axis for the solid orange

60 Westridge Marine Terminal Tsunami Assessment 58 bars depict the maximum water surface elevation for scenarios 1, 2, 4, and 5 (no tsunami for cases 3 and 6), while negative values indicate the lowest water level. It can be noted that the maximum water levels are larger than the low water levels. This is because the tsunami waves produced in the landslide scenarios propagate much like a solitary or translation wave, primarily consisting of displacement of water above the mean water level. The transition area depicted for Scenario 1 with a gradient from yellow to white indicates the maximum potential range of water levels for Scenario 1, which places an upper limit on extreme events. As discussed elsewhere, this scenario is at present considered implausible and warrants further input and closure. The reference datum is the Mean Sea Level (MSL) at zero. For comparison, the tide range is illustrated on the left side in the figures. The dark blue bar represents the high water tide range to Higher High Water Mean Tide (HHWMT), while the light blue bar indicates the range of Higher High Water Large Tide (HHWLT). The dark red bar indicates the range of Lower Low Water Mean Tide (LLWMT), while the light red bar denotes the range of Lower Low Water Large Tides (LLWLT). Water Level Variation (m) Tide Range Scenario 1 Scenario 2 Scenario 4 Scenario 5 HHWLT HHWMT LLWMT LLWLT Figure 5 2: Range of tsunami induced water level variations at Berth 1 It can be seen that the Landslide Scenario 2 produces the least variation in water levels at the project site, within a range limited to m. The remaining slide scenarios produce progressively larger water level variations (with increasing landslide volume), but at most a +1.5 m rise of the water level and a decrease in water level by 0.6 m. The results are fairly consistent between the three berths, although small differences in water levels can be noted.

61 Westridge Marine Terminal Tsunami Assessment 59 The tsunami induced water level variations can be noted to be on the same order of magnitude as the tides in the area. While changes in tide levels occur over minutes to hours, the tsunami induced water level variations would occur over a time span of minutes. However, it is likely that the moorings of a vessel at berth would be able to accommodate the change in water level. It should also be noted that while Figure 5 2 to Figure 5 4 show water level variations around MWL for illustration purposes, a landslide event could occur at a higher or lower state of the tide. However, tsunami induced water level variations can be expected to be approximately within the tidal range. Water Level Variation (m) Tide Range Scenario 1 Scenario 2 Scenario 4 Scenario 5 HHWLT HHWMT LLWMT LLWLT Figure 5 3: Range of tsunami induced water level variations at Berth 2

62 Westridge Marine Terminal Tsunami Assessment 60 Water Level Variation (m) Tide Range Scenario 1 Scenario 2 Scenario 4 Scenario 5 HHWLT HHWMT LLWMT LLWLT Figure 5 4: Range of tsunami induced water level variations at Berth TSUNAMI INDUCED FLOW VELOCITIES Figure 5 5 summarizes maximum tsunami induced flow velocities by magnitude and direction for the landslide scenarios investigated. The dark blue curves are representative of Scenario 1, the purple curves reflect Scenario 5, the red curves Scenario 4, and the orange curves Scenario 2. In each set of curves, the solid lines are representative of the flow field at Berth 1, the dashed lines portray results for Berth 2, and the dotted lines are representative of Berth 3. Overall, the results for the three berths are comparable in terms of magnitude and direction, although small differences are evident. The direction of flows are shown relative to true North, with the alignment of the berth indicated by the grey vessel outline.

63 Westridge Marine Terminal Tsunami Assessment m/s 0.6 m/s 0.5 m/s m/s 0.3 m/s 0.2 m/s m/s 0.0 m/s Scenario 1A Scenario 5 Scenario Scenario Figure 5 5: Magnitude and direction of maximum tsunami induced flow velocities The results show that while tidally driven ebb flows are approximately parallel to the berths (Figure 5 6), the tsunami induced flows tend to follow the alongshore direction of the inlet, which is approximately west southwest to east northeast, which is also the case for tidal flood flows (Figure 5 7). A comparison between tsunami induced flow velocities and the magnitude and direction of currents adopted for the mooring analysis, (M&N 2014) is provided in Figure 5 8 to Figure 5 10.

64 Westridge Marine Terminal Tsunami Assessment 62 Figure 5 6: East Burrard Inlet Mike21 model ebb current snapshot, (M&N, 2012) Figure 5 7: East Burrard Inlet Mike21 model flood current snapshot, (M&N, 2012)