NHC Technical Report

Chesterman Beach Tsunami Vertical Evacuation Scoping Study

Final Report Date: 30 September 2019

Photos from Northwest Hydraulic Consultants

Prepared for: Prepared by: District of Tofino Northwest Hydraulic Consultants

Address: 121 Third Street / PO Box 9 Address: 30 Gostick Place Tofino, BC V0R 2Z0 North Vancouver, BC, V7M 3G3 Attention: Keith Orchiston Attention: Philippe St‐Germain, P.Eng. Emergency Program Coordinator Coastal Engineer E: [email protected] E: [email protected] P: (250) 725‐3229, ext. 708 P: 604.969.3017

NHC Ref: 3004264

ACKNOWLEDGEMENTS

Northwest Hydraulic Consultants wish to acknowledge the valuable contributions of Lanarc Consultants and Gygax Engineering Associates as its partners in the undertaking of this Scoping Study.

Northwest Hydraulic Consultants is also thankful for the support of Mr. Keith Orchiston, Emergency Program Coordinator at the District of Tofino, who provided guidance and local knowledge throughout the project.

By providing numerical modelling results of tsunami inundation, the support and guidance by Dr. Ioan Nistor from the University of Ottawa and Dr. Tomoyuki Takabatake from Waseda University, Japan was much appreciated.

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EXECUTIVE SUMMARY

The community of Tofino is particularly vulnerable to tsunami risk because of its elongated low-lying areas and direct exposure to nearfield tsunamis from the Cascadia Subduction Zone (CSZ). The risks are exacerbated by the fact that the area is visited by many tourists during the peak tourist season and the relative remoteness of the area in terms of accessibility.

With the objective of mitigating such risk, the District of Tofino (DoT) has entered into a public/private agreement to evaluate the need for a single-purpose Tsunami Vertical Evacuation (TVE) structure for residents and visitors to the Chesterman Beach area, and to develop a high-level concept for such infrastructure to be considered for potential inclusion as part of the DoT’s overall tsunami risk mitigation planning.

This Scoping Study is based on the results of the numerical tsunami inundation modelling performed by the University of Ottawa (UoO, 2019). These results are summarized in this report and are contextualized within Tofino’s exposure to tsunamis and work and research by others. The model results considered an earthquake scenario with a moment magnitude (Mw) of 9.0. The rational for the selection

of this scenario, compared to other earthquake magnitudes, is that a Mw 9.0 is believed more likely to occur in the event of a full-length rupture CSZ earthquake.

The need for a TVE structure for the Chesterman Beach Area was evaluated through a high-level Geographic Information System (GIS) based evacuation assessment, which estimated how many individuals in the Chesterman Beach Area, who could not evacuate to any other high ground location, could potentially be saved by a TVE structure. This assessment took into account several parameters specific to the local context of Tofino including existing mitigation measures, closest natural high ground areas, evacuation pathways, location of buildings and houses, and population distribution for varying times of day during the summer peak season. Results suggest that at least 800 individuals would be saved by a TVE structure in the event of a tsunami occurring during summer daytime, which corresponds to approximately 50% of the people located in the Chesterman Beach during summer daytime. This estimate assumes that all individuals within distance of natural high ground areas would evacuate to such naturally high areas and not try to reach the TVE structure. This number should be considered as a lower-bound as in reality it is unlikely that all individuals within distance of natural high ground areas, especially tourists, would know how to access these areas.

Chesterman Beach Tsunami Vertical Evacuation Scoping Study I Final Report

The occupancy requirement for the TVE structure was established by evaluating the maximum number of people who could technically reach a TVE structure located as shown in the image below. This location was identified by the DoT based on land ownership. Results of the assessment suggest that 1,200 people could theoretically reach a TVE structure at the location identified. However, to account for uncertainties in the population estimates available at the time of this study, which the DoT suspects to be low, the maximum occupancy requirement for the TVE structure was doubled to ensure that the concept developed is scalable and does not have to change significantly following a better assessment of Tofino’s population. Furthermore, given the considerable uncertainty in population growth specific to the Chesterman Beach area, it was discussed with the DoT that future requirements for occupancy would potentially be handled by developing additional TVE structures.

Identified location for TVE structure in Chesterman Beach Area

Concept options for a TVE structure can vary greatly in terms of purpose, services, size, and character. An important step in the development of a TVE structure is the establishment of requirements for the structure’s functionality. For this Scoping Study, such requirements have been selected considering simplicity and safety as the main philosophies for design. Several conceptual alternatives were developed for a short-term tsunami refuge for occupants to survive tsunami flooding. Accordingly, no enclosure (i.e., walls) is considered for the TVE structure at this stage. It is important to understand that there is a possibility that a tsunami occurs during winter months, and given that a tsunami can result in several waves lasting over several hours and make affected areas difficult to access, the subsequent

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survival and well-being of the structure’s occupants may become a concern. Therefore, the requirement for wall enclosure is an aspect that should be carefully addressed in any further stages of design.

Based on a short-term refuge functionality, a minimum square footage per occupant of 0.93 square metres (10 square feet)per person was considered for sizing the TVE structure alternatives. A total of five alternatives were developed at a conceptual level according to the three main categories listed below.

The TVE structure alternatives and landforms illustrated in this Scoping Study are preliminary and intended to communicate conceptual massing and visual impacts in the context of the TVE structure location and its surrounding landscape. The structures are interpretations of general functional requirements and design criteria as expressed in this report. The alternatives as presented graphically herein are conceptual in nature and their visual appearance is expected to change following any further design development and consultation with the public.

TVE alternatives were reviewed by the Project Team and the consensus was that a life-saving tower with a square footprint was the preferred alternative to be further considered for the development of an order of magnitude cost estimate. Overall, this alternative was preferred for its symmetrical geometry which provides relatively better structural performance as well as for its simplicity of design and construction, which is expected to result in lower costs. Because of the critical function that the TVE structure needs to fulfill, architectural and aesthetical aspects had little influence in the selection of the of the preferred option at this stage.

A preliminary rendering of the preferred TVE structure alternative is shown below. Each level including the roof deck has the capacity for 640 evacuees resulting in a total of 2,560.

It should be noted that the graphical renderings presented in this report do not reflect all aspects of high-level structural design elaborated as part of this Scoping Study. Because consideration of such aspects is anticipated to result in a structure with more apparent robustness, which would result in a stronger visual impact, it is recommended that any alternatives selected for further consideration be updated to include these details prior to their use for public consultation.

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Rendering of square life-saving tower alternative. Central concrete core and support for access ramp not shown, location of stairs subject to change. To develop an order-of-magnitude cost estimate for the square footprint life-saving tower, a high-level structural design was completed based solely on professional judgement and experience, and no specific design calculations were performed given the conceptual nature of this Scoping Study.

Including contingencies, it is estimated that the construction cost of the life-saving tower with a square footprint is approximately $4.6M. If a phased construction approach is taken, the cost of constructing the first level is estimated at $2.9M, with the cost of additional levels estimated at $0.7M. This order-of- magnitude capital costs estimate does not include further engineering, geotechnical, and architectural design and services, nor operational and maintenance costs.

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TABLE OF CONTENTS

1 INTRODUCTION ...... 1 2 REVIEW OF TSUNAMI HAZARD...... 2 2.1 Exposure ...... 2 2.2 Inundation Modelling by UoO ...... 4 2.3 Earthquake Scenario for TVE Development ...... 15 3 NEED FOR VERTICAL EVACUATION AT CHESTERMAN BEACH ...... 16 3.1 Existing Tsunami Mitigation Measures ...... 16 3.2 Description of Potential Site for TVE Structure ...... 19 3.3 Evacuation Assessment ...... 23 3.4 Occupancy Requirements for TVE Structure ...... 32 4 CONCEPTUAL DEVELOPMENT OF TVE STRUCTURE ...... 34 4.1 Functional Requirements ...... 34 4.2 Design Criteria and Design Considerations ...... 37 4.3 TVE Structure Alternatives ...... 44 4.4 Preferred Alternative ...... 61 4.5 Cursory Assessment of Visual Impact ...... 61 5 ORDER-OF-MAGNITUDE CAPITAL COST ESTIMATE ...... 63 5.1 High-level Conceptual Structural Design ...... 63 5.2 Cost Estimating ...... 65 6 SUMMARY ...... 67 6.1 Recommendations for Future Assessment ...... 68 7 CLOSURE ...... 71 8 REFERENCES ...... 71

Appendix A Breakdown of Order-of-Magnitude Capital Cost Estimate

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LIST OF TABLES

Table 1. Full-rupture CSZ earthquake scenarios considered for modelling by UoO (2019) according to Wiebe and Cox (2014)...... 5 Table 2. Moving speed of evacuees based on age...... 24 Table 3. Expected population and growth rates for entire district as provided by DoT ...... 29 Table 4. General dimensions of soil berm alternatives...... 56 Table 5. Unit rates considered for cost estimating ...... 66

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LIST OF FIGURES

Figure 1. Subduction zones around the Pacific Ocean and locations of several great tsunamigenic earthquakes (adapted from Atwater et al., 2005)...... 3 Figure 2. Seaward edge (dotted red line) of Cascadia subduction zone (UoO, 2019)...... 3 Figure 3. Relative probability of rupture scenarios for a 500-year CSZ earthquake according to AECOM (2013)...... 5

Figure 4. Extent of flooding associated to the Mw 9.0 earthquake scenario as per UoO model results. Grey dash lines DoT Official Community Plan areas...... 8

Figure 5. Maximum inundation depth associated to the Mw 9.0 earthquake scenario within the DoT jurisdiction as per UoO model results...... 9

Figure 6. Maximum overland flow velocity associated to the Mw 9.0 earthquake scenario within the DoT jurisdiction as per UoO model results...... 10

Figure 7. Extent of flooding associated to the Mw 9.3 earthquake scenario as per UoO model results. Grey dash lines DoT Official Community Plan areas...... 12

Figure 8. Maximum inundation depth associated to the Mw 9.3 earthquake scenario within the DoT jurisdiction as per UoO model results...... 13

Figure 9. Maximum overland flow velocity associated to the Mw 9.3 earthquake scenario within the DoT jurisdiction as per UoO model results...... 14 Figure 10. DoT’s current official tsunami evacuation map ...... 17 Figure 11. Identified location for proposed TVE structure...... 20 Figure 12. 2015 aerial photograph of identified location for proposed TVE...... 20 Figure 13. Area of lot considered for conceptual development of TVE structure...... 21 Figure 14. Existing vegetation at identified location of TVE structure (looking northeast)...... 21 Figure 15. Existing entrance to identified location of TVE structure (looking east)...... 22 Figure 16. Appearance of roadside near identified location of TVE structure (looking northeast)...... 22

Figure 17. Inundation area for the Mw 9.0 earthquake scenario...... 25 Figure 18. Summer daytime population estimates for various FCL zones as provided by the DoT...... 27 Figure 19. Summer nighttime population estimates for various FCL zones as provided by the DoT. ... 28 Figure 20. Areas (red) from which loss of life could be prevented by a TVE structure at the proposed location. Green shows areas where evacuees could technically reach the proposed TVE structure but are also within reach of nearest natural high ground refuge areas...... 31 Figure 21. Evacuation pathway of individuals within Chesterman Beach Area who could technically reach the TVE structure. Orange indicate the survivable pathway of individuals under 65 and overlaying yellow the survivable pathway of individuals over 65...... 33 Figure 22. Storage box containing supplies at TVE structure near Kamakura, Japan (Photo: Philippe St- Germain, 2018)...... 36 Figure 23. Definition of Minimum Refuge Level Elevation (Adapted from ASCE7-16). Elevations with respect to CGVD2013 Access stairs and central core not shown for representation purposes...... 41 Figure 24. Schematic diagram showing relationships among soils and surficial deposits in relation to points indicated on upper image (Baker, 1969)...... 43

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Figure 25. Tsunami vertical evacuation tower recently constructed near Kamakura, Japan (Photo: Philippe St-Germain, 2018) ...... 45 Figure 26. Rendering of square life-saving tower alternative. Central core and support for access ramp not shown, location of stairs subject to change...... 47 Figure 27. Bird’s-eye view rendering of square life-saving tower alternative. Central core and support for access ramp not shown, location of stairs subject to change...... 48 Figure 28. Preliminary floor and column layout for square life-saving tower alternative (dimensions in metres). Access stairs and central core not shown for representation purposes...... 48 Figure 29. Rendering of rectangular life-saving tower alternative. Central core and access ramp not shown, location of stairs subject to change...... 50 Figure 30. Bird’s-eye view rendering of rectangular life-saving tower alternative . Central core and access ramp not shown, location of stairs subject to change...... 50 Figure 31. Preliminary floor and column layout for rectangular life-saving tower alternative (dimensions in metres). Access stairs and central core not shown for representation purposes...... 51 Figure 32. Preliminary floor and column layout for circular life-saving tower alternative (dimensions in metres). Access stairs and central core not shown for representation purposes...... 52 Figure 33. Rendering of soil berm alternative ...... 54 Figure 34. Plan view of soil berm alternative showing access ramp and stairs...... 54 Figure 35. Plan view schematic of potential soil berm alternative using retaining walls and 3H:1V access slope...... 55 Figure 36. Rendering of hybrid soil berm with platforms alternative. Central core not shown and location of stairs subject to change...... 59 Figure 37. Bird’s-eye view rendering of hybrid soil berm with platforms alternative. Central core not shown and location of stairs subject to change...... 59 Figure 38. Plan view of hybrid soil berm with platforms alternative showing access ramp. Location of stairs subject to change...... 60 Figure 39. Preliminary floor and column layout for platforms on top of soil berm (dimensions in metres). Access stairs and central core not shown for representation purposes...... 60 Figure 40. Visual impacts of a life-saving tower as seen from the beach. Result may vary depending on assessment of vegetation...... 62 Figure 41. Plan view of conceptual level details of TVE structure beam, column, and central core systems. (Sketch based on inputs from GEA)...... 64 Figure 42. Section view of conceptual level details of TVE structure column connections with slab and beams. (Sketch based on inputs from GEA) ...... 64

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1 INTRODUCTION

With the objective of mitigating such risk, the District of Tofino (DoT) has entered into a public/private agreement to evaluate the need for a single-purpose Tsunami Vertical Evacuation (TVE) structure for residents and visitors to the Chesterman Beach area, and to develop a preliminary concept for such infrastructure which will be considered for potential inclusion as part of the DoT’s overall tsunami risk mitigation planning.

As part of this Scoping Study, Northwest Hydraulic Consultants Ltd. (NHC) reviewed tsunami hazards in the Chesterman Beach Area, evaluated the need for a TVE structure and its occupancy requirement through a high-level Geographic Information System (GIS) based evacuation assessment, and developed several concept alternatives for a TVE structure, including the preparation of an order-of-magnitude capital cost estimate for the preferred alternative.

General design criteria for the TVE structure alternatives were based on tsunami inundation modelling by the University of Ottawa (UoO, 2019).Conceptual development was supported by Lanarc Consultants (Lanarc), who generated renderings that allowed for the investigation of structure types, structure dimensions, and access options within the site-specific context of Chesterman Beach. High-level structural design and the development of the order-of-magnitude cost estimate for the preferred alternative was supported by inputs from Gygax Engineering Associates (GEA).

Recommendations and considerations for future assessment identified during this Scoping Study are mentioned in the main body of the report, but are also recorded and organized at the end for ease of reference.

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2 REVIEW OF TSUNAMI HAZARD

To develop a TVE structure, the tsunami hazard must be defined to evaluate the need for the structure, define the structure’s occupancy requirements, and establish general criteria for design.

The results of the numerical inundation modelling by the UoO (2019) are used as the basis for the Scoping Study. These results are presented below and are contextualized with Tofino’s exposure to tsunamis and other research.

2.1 Exposure

As with many other communities along the BC coast, the DoT is exposed to tsunamis originating along the Pacific Oceans’ Ring of Fire. The Ring of Fire consists of a nearly continuous series of tsunamigenic subduction zones surrounding the ocean (Figure 1). Several great (i.e., magnitude 8 or higher) subduction earthquakes have occurred in recent history, exemplifying the tremendous impacts tsunamis can have on communities, even ones located away form their sources. A geologically recent and well known Canadian example is the tsunami that partially destroyed the town of Port Alberni, BC, during the night of March 28, 1964. This tsunami, which was generated by a moment magnitude (Mw) 9.2 (USGS, 2011) subduction earthquake south of the Alaskan coast, reached Vancouver Island within approximately 4 hours after the earthquake event. Its waves were smaller along the open coast of the island but were significantly amplified at Port Alberni as the town is located at the head of a fjord valley.

What makes Tofino particularly susceptible to potentially large tsunami waves is the close proximity of the CSZ, the northern limit of which is located a few hundred kilometres offshore of Vancouver Island (Figure 2). The close proximity of the CSZ means there will be a short warning time between an earthquake event and the arrival of a tsunami. Such warning time is further discussed in Section 3.3.1. The CSZ is approximately 1,000 km in length and extends south down to northern California. Tofino has been identified as a community particularly vulnerable to the impact of a CSZ tsunami given the short warning time and the community’s elongated low-lying area (Cheff et al., 2016). Geological and historical studies show that a great subduction earthquake, followed by the generation of a large tsunami, occurred during the year of 1700 (Atwater et al., 2005). The event, which consisted of a full-length rupture of the CSZ, is estimated to have had a Mw between 8.7 and 9.2 (Wiebe and Cox, 2014) and a slip distance of 19 m (Satake et al., 2003). The average reoccurrence of a full-length CSZ event similar to the one of 1700 is 500 years, and the next event is estimated to have a 7-12 % probability of occurrence by 2060 (Goldfinger et al., 2012).

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1700

Figure 1. Subduction zones around the Pacific Ocean and locations of several great tsunamigenic earthquakes (adapted from Atwater et al., 2005).

Figure 2. Seaward edge (dotted red line) of Cascadia subduction zone (UoO, 2019).

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According to the Federal Emergency Management Agency (FEMA, 2012), tsunamis can be generally categorized by the distance to the location of the triggering event and the time it takes to waves to reach a given site. A far-source generated tsunami is one that originates from a source that is far away from the site of interest and takes 2 hours or longer to arrive, and the originating earthquake will likely not be felt before the first waves arrive. A mid-source generated tsunami is one in which the source is somewhat closer to the site of interest, but not close enough for the effects of the triggering event to be felt at the site. Mid-source generated tsunamis would be expected to arrive between 30 minutes and 2 hours after the triggering event. A near-source generated tsunami is one that originates from a source that is close to the site of interest, and can arrive within 30 minutes or less.

This assignment focuses on near-source generated tsunamis, such as a CSZ event for the DoT. However, consideration needs to be given as per the use of a TVE structure and its incorporation into evacuation plans for events generated further away which provides longer evacuation time.

2.2 Inundation Modelling by UoO

As results of tsunami inundation modelling depend on a various parameters, such as the earthquake scenario and characteristics specific to a numerical model, the numerical inundation model developed by the UoO (2019) is presented below in the context of other information available for the British Colombia Coast.

In the context of this assignment, the earthquake scenarios, or tsunami sources are not only described as the earthquake moment magnitude but also as the geological parameters associated to the fault rupture. These parameters include, but are not limited to, rupture length and width, slip distance, rupture mechanism, and subsidence at Tofino.

As part of their agreement with the DoT, the UoO conducted numerical simulations to estimate characteristics of tsunami inundation as a result of various full-length CSZ rupture earthquake scenarios.

These scenarios, which are based on the work of Wiebe and Cox (2014), have Mw varying from 8.7 to 9.3 with associated slip distances varying from approximately 3 m to 25 m (Table 1). Rupture length and width were kept constant to 1,000 km and 100 m, respectively. The initial water surface perturbation was defined based on the Okada (1985) seafloor deformation model. These scenarios are considered hypothetical and were used by Wiebe and Cox (2014) to illustrate the sensitivity of slip distance to tsunami severity and provide an envelope of likely impacts to communities.

For full-length CSZ ruptures, the displaced area remains relatively constant (Goldfinger et al., 2012), so the increased moment magnitude acts to increase the slip distance. For subduction zone earthquakes, slip is a main mechanism in determining the magnitude of a tsunami (Wiebe and Cox, 2014).

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Table 1. Full-rupture CSZ earthquake scenarios considered for modelling by UoO (2019) according to Wiebe and Cox (2014). Earthquake Magnitude Slip Distance (Mw) (m) 8.7 3 9.0 9 9.3 25

Others have also modelled CSZ tsunamis considering several varying earthquake scenarios. Such scenarios are presented below at a high-level for comparison purposes, but also to guide any further assessment of earthquake scenarios as required.

In their assessment of potential tsunami inundation limits for the Capital Regional District (CRD), AECOM (2013) selected one among twelve CSZ rupture scenarios based on US National Seismic Hazard Maps (USGS, 2008). Each of the scenarios has a recurrence interval of 500 years, but are assigned different joint probability of occurrence in comparison with each other, according to both rupture configuration and earthquake magnitude (Figure 3). As per AECOM (2013), “each of the configurations includes the entire locked zone (LZ), but may extent to the midpoint (MT) or the base (BT) of a plastic transition zone. In addition, global analogs (GA) of shallow-dipping subduction zones place the eastern boundary of the rupture at 123.8°W near the Pacific coastline of Washington and Oregon states around a depth of 30 km below the earth surface.” For their analysis, AECOM (2013) selected the scenario with the highest joint probability of occurrence, not necessarily the most severe event, which consisted of a Mw 9.0 event of a GA configuration with an associated slip of approximately 15 m.

Figure 3. Relative probability of rupture scenarios for a 500-year CSZ earthquake according to AECOM (2013). Wang and Tréthu (2016) presents potential rupture mechanisms, or slip behaviour at the deformation front of the CSZ and their influence on the deformation (slip and uplift) of the seafloor. Two of these slip behaviours (buried rupture and splay faulting) were modelled by Fisheries and Oceans Canada (DFO, 2018) for the assessment of the impacts of a CSZ tsunami at the Canadian Coast Guard Base in Prince Rupert. Their numerical tsunami simulations revealed that the choice of slip behaviour had an influence

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 5 Final Report on tsunami wave height, with the splay faulting behaviour having a stronger impact on coastal areas of

Vancouver Island. The Mw 8.9 CSZ event considered by DFO (2018) had a length and a width of 1,000 km and 83 m, and a maximum and average slip of 18 m and 9 m, respectively.

As part of the recent DoT coastal flood mapping efforts, Cascadia Coast Research Ltd. (2018) simulated the 1700 CSZ event according to the fault deformation of Wang et al. (2003). This fault deformation was also considered by Cherniawsky et al. (2007) in their numerical assessment of tsunami heights and currents in several bays and harbours on southern Vancouver Island including Ucluelet, Victoria and Esquimalt.

Furthermore, Witter et al. (2013) simulated CSZ tsunamis to characterize the associated hazard on the Oregon Coast according to a total of 15 megathrust earthquake scenarios developed based on onshore and offshore paleoseismological evidence. Relative probabilities of occurrence between earthquake scenarios in comparison with each other are also discussed. Maximum modelled tsunami wave elevations at the shoreline varied from approximately 4 m to 25 m for earthquakes with slip distance and moment magnitude varying from 9 m to 44 m and Mw 8.7 to Mw 9.2, respectively.

In their assessment of tsunami inundation, the UoO (2019) used a numerical tsunami propagation and inundation model developed at Waseda University, Tokyo, Japan, which is based on the non-linear shallow water equations and which considers Manning’s friction law and the effect of the Coriolis force. This model, referred to as the Waseda model here after, has been applied to assess tsunami hazards for various coastal areas in Japan and has been validated based on field observations following the 2011 Japan Tohoku Tsunami (Kukita and Shibayama 2012). This comprehensive validation considered records of inundation depth and extent, as well as flow velocities. The UoO also compared their results with ones obtained using the ComMIT/MOST model maintained by the National Oceanic and Atmospheric Administration (NOAA).

The digital representation of the seafloor and ground surface, commonly referred to as the Digital Elevation Model (DEM) of the tsunami model was developed using the following data sources:

§ LiDAR topographic data collected by the DoT § Bathymetric survey data collected by the DoT § Navigation chart data from the Canadian Hydrographic Service (CHS) § Canadian Digital Elevation Model (CDEM) § NOAA’s Costal Elevation Model § General Bathymetric Chart of the Oceans (GEBCO) A nested approach was employed to propagate the tsunami from its offshore source to the coast and the computational grid size used to simulate overland tsunami inundation in Tofino is approximately

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20 m. For additional details regarding the tsunami model considered to support this Scoping Study, the reader is referred to the UoO (2019) report.

Model results of tsunami inundation within the DoT jurisdiction are presented below for the Mw 9.0 and

Mw 9.3 earthquake scenarios, with particular focus on the Chesterman Beach Area. For development of a TVE structure, tsunami inundation simulation were performed for a still water level corresponding to Higher High Water Large Tide (HHWLT) with an additional allowance of 1 m for sea level rise (total of 3 m above mean sea level). Inherently, land subsidence occurring immediately with the earthquake ultimately acts as an increase to the still water level at Tofino with respect to the ground elevation. Based on the fault deformation considered by the UoO, such subsidence is approximately 2 m and 4 m for the Mw 9.0 and Mw 9.3 earthquake scenarios, respectively.

Numerical results of flooding extent, maximum inundation depth and maximum overland flow velocity associated to the simulation of a tsunami generated by the Mw 9.0 earthquake scenario are presented in Figure 4, Figure 5, and Figure 6, respectively.

Results show flooding of Chesterman Beach Area to be extensive across the Esowista Peninsula at this location (Figure 4). Relatively nearby areas that remains above water include Rosie Bay just south of Chesterman Beach, the residential Ocean Park Drive neighbourhood located east of Highway 4 and north of Sharp Road, and part of the headland directly north of Chesterman Beach.

For this earthquake scenario, the inundation depth in the upland areas at Chesterman Beach are estimated to be between 4 m and 6 m (Figure 5) and overland flow velocities vary between 2 m/s to 6 m/s depending on the location (Figure 6).

According to model results by the UoO (2019), the main brunt of the tsunami will reach Tofino in approximately 30 minutes following a CSZ earthquake. Model results suggest that this arrival time is relatively independent of earthquake magnitude. Results also suggest however that the offshore water level will gradually increase to approximately 4 m above mean sea level at around 15 minutes following the earthquake. The time-history of the water level change from mean sea level reported by the UoO (2019) shows tsunami effects just offshore of Chesterman Beach lasting at least 3 hours following the earthquake.

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Figure 4. Extent of flooding associated to the Mw 9.0 earthquake scenario as per UoO model results. Grey dash lines DoT Official Community Plan areas.

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Figure 5. Maximum inundation depth associated to the Mw 9.0 earthquake scenario within the DoT jurisdiction as per UoO model results.

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Figure 6. Maximum overland flow velocity associated to the Mw 9.0 earthquake scenario within the DoT jurisdiction as per UoO model results.

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Numerical results of flooding extent, maximum inundation depth and maximum overland flow velocity associated to the simulation of a tsunami generated by the Mw 9.3 earthquake scenario are presented in Figure 7, Figure 8, and Figure 9, respectively.

Compared to the Mw 9.0 scenario, the inundation associated with the Mw 9.3 scenario is more devastating, inundating a vast majority of the peninsula (Figure 7). Relatively nearby high ground areas that remained above water in the case of the Mw 9.0 scenario are either fully submerged or very restrained in terms of surface area that remains dry.

The inundation depth in the upland areas at Chesterman Beach are estimated to be between 8 m and 10 m (Figure 8) and overland flow velocities vary spatially between 6 m/s to 8 m/s depending on the location (Figure 9).

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Figure 7. Extent of flooding associated to the Mw 9.3 earthquake scenario as per UoO model results. Grey dash lines DoT Official Community Plan areas.

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Figure 8. Maximum inundation depth associated to the Mw 9.3 earthquake scenario within the DoT jurisdiction as per UoO model results.

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Figure 9. Maximum overland flow velocity associated to the Mw 9.3 earthquake scenario within the DoT jurisdiction as per UoO model results.

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2.3 Earthquake Scenario for TVE Development

The choice of earthquake scenario is a crucial step in any planning of tsunami risk mitigation. For the development of a TVE structure more specifically, it can have considerable implications on its structural design. The choice of earthquake scenario is also an important parameter in the elaboration of evacuation zones and evacuation plans, which in turn can affect the occupancy requirements of a TVE structure.

Reflecting back to the 2011 Tohoku tsunami experience in Japan, and according to the Earthquake Engineering Research Institute (EERI, 2011), failure to evacuate was the primary cause of the high number of casualties associated to the tsunami (reaching nearly 20,000 causalities). Such a conclusion is a result of several factors which include hazard assessments that underestimated the magnitude of the design earthquake and tsunami. These hazard assessments were mainly based upon recent historic events rather than potentially larger events that had been recognized by paleo-seismologists in geological records. This subsequently raised fundamental questions about hazard assessment and planning for rare but potentially catastrophic events.

However, in consultation with the DoT (personal communication with Keith Orchiston March 26, 2019), it was decided that this Scoping Study should consider the model results associated to the Mw 9.0 earthquake scenario modelled by the UoO (2019). The rational for this decision is that, compared to other earthquake magnitudes, a magnitude of Mw 9.0 is believed more likely to occur in the event of a full-length rupture CSZ earthquake. This is mainly supported by the information presented in USGS (2008). Furthermore, there is currently some uncertainty associated to the actual potential for the CSZ to produce an earthquake of similar characteristics as the Mw 9.3 earthquake scenario considered for modelling by the UoO, and its probability of occurrence is smaller.

Nevertheless, further consideration should be given to the assessment, by a geologist and/or seismologist, of the most adverse CSZ earthquake physically possible both in terms of probability of occurrence and tsunami generation characteristics. To allow the DoT to make informed planning decisions according to risk tolerance, such worst case probability and tsunami characteristics should be compared to the ones of a milder but more probable scenario.

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3 NEED FOR VERTICAL EVACUATION AT CHESTERMAN BEACH

To evaluate the need for TVE structure(s) in the Chesterman Beach area a high-level evacuation assessment is performed using GIS. The assessment is only examining the need of a TVE structure in the Chesterman beach area and not for other locations within Tofino. The assessment includes two parts, the first estimating loss of life potentially avoided with a TVE structure and the second considering the maximum number of people who could reach a TVE structure. The location of the TVE structure considered for this assessment has been identified by the DoT based on land ownership (Keith Orchiston, personal communication, March 26, 2019) and is presented in Section 3.2.

The assessment to predict the loss of life avoided (LoLA) identifies the need for vertical evacuation by estimating the number of people who cannot reach another potential evacuation area and would presumably become casualties without a TVE structure. The estimation of the number of people who could technically reach the TVE estimates the maximum occupancy requirement for a TVE structure. These two assessments provide an upper and lower bound for TVE occupancy requirements, however TVE occupancy should be confirmed with a revised evacuation plan prior to further development, as conservative assumptions are made regarding the choice of evacuation routes by evacuees.

The outcomes of this assessment are expected to support the DoT’s decision-making process as to whether or not a TVE structure should be considered further in its planning for tsunami risk mitigation, and if so, what occupancy it should be design for. The outcomes may also serve to evaluate if more than one structure is needed in the case that the required occupancy cannot be achieved at one location only.

3.1 Existing Tsunami Mitigation Measures

The consequences of a tsunami depend on the effectiveness of existing mitigation measures and the preparedness of the community at risk. These factors and associated assumptions have been reviewed and discussed with the DoT to ensure they are incorporated realistically in the evacuation assessment.

The DoT has taken steps to minimize the risk from tsunamis including mapping potential tsunami hazard areas (Emergex, 2006). Refuge areas were identified considering an evacuation elevation of 20 m as per the provincial standard at the time. To date, this elevation is still considered for defining the single, district-wide tsunami evacuation zone as indicated on the DoT’s current official tsunami evacuation map (Figure 10).

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Figure 10. DoT’s current official tsunami evacuation map

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Near the Chesterman Beach Area are two naturally occurring areas of high ground (> 20 m) based on the current evacuation map. One area is just south of Chesterman Beach south and is commonly referred to as Rosie Bay, and the other is in the woods east of Ocean Park Drive neighbourhood. The latter is accessible through Sharp Road although involves traveling through dense vegetation. Such areas are not official refuge areas, although there is an informal consensus amongst some residents to evacuate to Rosie Bay in the event of a Tsunami.

As per the DoT’s website, local emergency preparedness plans distinguish between two types of tsunamis – local and distant tsunamis – and prescribes distinctive evacuation procedures for each one of them.

Local Tsunamis

Local tsunamis are considered to be generated from a source within 1,000 km or less than 1 hour tsunami travel time from its source to the area impacted. This would comprise near-source and mid- source tsunamis according to FEMA’s (2012) classification. For such an event, ground shaking is indicated as the official warning for evacuation towards high ground to occur on foot or by bicycle. Such warning is generally referred to as a natural warning.

Distant Tsunamis

Distant tsunamis are generated from more than 1,000 km away or more than 3 hours travel time from the tsunami sources to the area impacted. This is similar to FEMA’s (2012) far-source tsunami classification. In such an event the DoT receives notification via Emergency Management BC (EMBC)and NOAA’s National Tsunami Warning Center (NTWC). The DoT then conveys the warning to the population through several different notification systems, including outdoor tsunami sirens located at Chesterman Man Beach and in Cox Bay. Such warning is generally referred to as official warning. The same as for a local tsunami, the population is indicated to leave the designated evacuation zone, however since more time is available to evacuate, the population is directed to reach the Community Hall, or a friend or relative’s house outside of the evacuation zone.

This Scoping Study focuses on local tsunami threats, however it is clear that a TVE structure will have to be carefully incorporated in the DoT’s overall tsunami evacuation plans, which should be updated accordingly.

Although the scope of this Scoping Study does not include evacuation planning, it is noted that the DoT may want to review having a single evacuation zone. The designation of a single tsunami evacuation zone can have some advantages for simplicity in evacuation planning, and for public awareness and understanding. However, because a single zone would have to accommodate for a larger range of

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 18 Final Report tsunami scenarios, it can result in relatively frequent “over-evacuation” of a larger area than necessary for more frequent, smaller scale events. Over time, this may create inconvenience for the public. As such, repeated “over-evacuation” could result in decreasing levels of community trust in, and compliance with, emergency response arrangements. On the other hand, differentiation of evacuation zones requires greater mapping resources and greater levels of coordination in planning and managing responses for each threat or event. This greater complexity also creates more scope for public misunderstanding about what they need to know and do in each instance.

3.2 Description of Potential Site for TVE Structure

The location of the TVE structure considered for this assessment has been identified by the DoT based on land ownership (Keith Orchiston, personal communication, March 26, 2019) and is shown in Figure 11. The site is centrally located to Chesterman Beach, situated behind existing residential development. This site has access from the beachfront, across Lynn Road and between existing residential parcels. The right of way from Lynn Road is approximately 10 m wide (Figure 12). The portion of the lot considered available for the development of a TVE structure is shown in Figure 13 and covers a surface area of approximately 8,400 m2. The ground elevation near the center of the lot is approximately 6.9 m with respect to the Canadian Geodetic Vertical Datum of 2013 (CGVD2013). Datum which approximately corresponds to mean sea level.

According to the aerial photograph collected as part of DoT’s 2015 LiDAR collection in conjunction with field observations made by NHC as part of an opportunistic site visit, approximately one third of the site appears to be covered by coniferous trees (west) and the rest of deciduous trees of relatively shorter height (Figure 14).

The appearance of the entrance and roadside of the identified site are shown in Figure 15 and Figure 16, respectively.

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Figure 11. Identified location for proposed TVE structure.

Figure 12. 2015 aerial photograph of identified location for proposed TVE.

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Figure 13. Area of lot considered for conceptual development of TVE structure.

Figure 14. Existing vegetation at identified location of TVE structure (looking northeast).

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Figure 15. Existing entrance to identified location of TVE structure (looking east).

Figure 16. Appearance of roadside near identified location of TVE structure (looking northeast).

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3.3 Evacuation Assessment

The GIS-based evacuation assessment performed as part of this Scoping Study has objectives to:

1) Estimate the loss of life in the Chesterman Beach Area that would be avoided by having a TVE structure in this area, and 2) Estimate the occupancy requirement of the structure.

Several assumptions are required for the assessment and these are presented below.

The number of individuals who can reach refuge areas before the arrival of the tsunami is assessed based on assumptions and methodology as outlined below. Assumptions are made about the time of day and season at which the tsunami occurs, warning time, speed of travel, inundated area, population spatial distribution, and population growth.

Time of Day and Season

The time of day and season affect the number of people in the area and their travel speeds. For this assessment, the summer season is considered as there are more people in the Chesterman Beach area than during the winter season. Both a daytime and a nighttime scenario are considered.

Tsunami Warning Time

According to model results by the UoO (2019), the main brunt of the tsunami will reach Tofino in approximately 30 minutes following a CSZ earthquake. Model results suggest that this arrival time is independent of earthquake magnitude. Based on the duration of shaking and the population’s reaction time, it is assumed that evacuees will start evacuating 5 minutes after the earthquake during daytime, and 15 minutes after the earthquake during nighttime. With a 30 minute warning time before the main tsunami wave and a 5 or 15 minute assumed evacuation start time, there are 25 minutes of active evacuation time left for travel during the day, and 15 minutes of active evacuation time for travel during the night. While inundation may begin before the main brunt of the tsunami, as suggested by model results, the assumption is made that the evacuating population will be able to remain ahead of the rising waters until the main tsunami wave arrives. While some evacuees may not stay ahead of the rising water, this assumption provides a conservative estimate for the required occupancy of the TVE structure.

Speed of Travel

It is assumed that all evacuees evacuate by foot (i.e., walking or running). While in reality some people may attempt to evacuate by car, it is assumed that most people will know to evacuate by foot as vehicular evacuation is likely to lead to traffic jams and have limited success. Any evacuees which begin to evacuate in vehicles are expected to abandon their vehicles and evacuate primarily by foot.

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The moving speed of evacuees varies depending on factors including their age, fitness level, physical ability, terrain, level of preparedness, and time of day. There is limited understanding of the impact of all of these factors on average moving speed in an evacuation specific to Tofino. The moving speeds of people of different ages and times of day have been estimated by Japanese research. Daytime moving speeds were assumed according to Kamino (1980) and are presented in are presented in Table 2. Based on discussions with DoT and UoO, these speeds were reduced by 50% for nighttime travel to account for more challenging travelling conditions.

Table 2. Moving speed of evacuees based on age. Daytime Speed Nighttime Age (m/s) Speed (m/s) Under 65 1.19 0.56 Over 65 0.96 0.48

FEMA (2012) indicates that the average healthy person can walk approximately 4 mph (1.8 m/s) and the travel speed of mobility-impaired population can be assumed to be about 2 mph (0.9 m/s). Without any further assessment for understanding the factors that affect travel speed and how such factors applies to Tofino, travel speed presented in Table 2 are considered for this Scoping study.

Inundation Area

The inundation area is based on tsunami modelling results obtained by the UoO considering the Mw 9.0 earthquake scenario. The modelled tsunami inundation in the vicinity of the Chesterman Beach Area is shown in Figure 17, in addition to building footprints, and official trails and roads. The closest and accessible areas of natural high ground not inundated under such scenario include the Ocean Park Drive neighbourhood and the Rosie Bay area. These areas have been identified as potential refuge areas in the Emergex (2006) report. High ground also exists on the headland close to Wickaninnish Inn. As the accessibility of this area is unknown, it was not included in analysis.

It is assumed that once individuals reach a refuge area, whether the TVE structure or natural high ground, they are safe. No considerations of travel time related to congestion at or accessing refuge areas were given. Furthermore, to provide a lower bound estimate to the loss of life that would be avoided by a TVE structure at the identified location in the Chesterman Beach Area, the occupancy of the Ocean Park Drive and Rosie Bay potential refuge areas is assumed to be unlimited. In reality however, especially for Rosie Bay area, the occupancy of the refuge areas may be exceeded by the number of evacuees reaching them which would lead to a higher number of causalities.

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Ocean Park Dr. Neighbourhood

Identified TVE Location

Rosie Bay Area

Figure 17. Inundation area for the Mw 9.0 earthquake scenario.

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Population Distribution

To estimate the number of evacuees, a summer scenario was examined as more people are in the Chesterman Beach Area during the summer than at any other time. As part of the coastal flood mapping assessment undertaken by Ebbwater Consulting Ltd. (2019), four FCL zones have been defined for the DoT (Figure 18 and Figure 19), with the Chesterman Beach area within the zone referred to as “Zone 1”. The DoT estimated the number of people in each FCL zone for different temporal situations. The summer daytime and nighttime population estimates for Zone 1 were used as the basis for the number of people in the area for this assessment. This population estimate includes an age distribution for Zone 1 which indicates that 88.5% of the population are under 65, and 11.5% of the population are over 65. This population age distribution is based on census data which describes the age breakdown of residents. A report on tourism in the area identifies an age breakdown of the visiting population with 8.4% of the visiting population over 65 (InterVISTAS, 2019). For this project, the census-based age breakdown was applied to the resident and transient population portions, and the visitor-survey based age breakdown was applied to the multi-day and day-tripper population portions. Through a weighted average of the age breakdowns for visitor and resident populations, an overall age breakdown of 90% of the population under 65 and 10% of the population over 65 was estimated and used in calculations.

To analyze the impact of the inundation on human life, the population in Zone 1 must be distributed to buildings and beaches for both the daytime and nighttime summer scenarios. The following distribution of population is based on resort occupancy information collected by the DoT and assumptions made by the UoO (2019) for their evacuation simulation in consultation with the DoT.

It is assumed that 1080 people are on Chesterman beach (north and south) during the day in the summer, and no one is on the beach at nighttime in the summer. The population assumed to be on the Chesterman beaches was assumed to be distributed with a uniform density. During the daytime, resort occupancy is estimated to be 75, and occupancy per building is estimated to be 2. During the nighttime, occupancy of both resorts and buildings is expected to double to 150 and 4 respectively. These estimates should be refined by building-specific information about summer daytime and nighttime occupancy to improve estimation of the capacity.

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Figure 18. Summer daytime population estimates for various FCL zones as provided by the DoT.

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Figure 19. Summer nighttime population estimates for various FCL zones as provided by the DoT.

Population Growth

For the purpose of estimating what could be the required occupancy of the TVE structure considering a 50-year horizon, population growth rates needed to be defined. The DoT’s population distribution estimate (e.g., Figure 18 and Figure 19) also includes a breakdown of the population by type which was used to estimate population growth. The four population types identified by the DoT include: resident (R) – people who live in the area; multi-day visitor (V) – people who visit the area for multiple days; day- tripper (DT) – people who are only in the area for the day; and transient (T) – hospitality staff and non- paying campers.

Based on limited information in which outcomes of three reports on population growth for the entire district are included, estimates of population annual growth rate per population type were established and are presented in Table 3, as provided by the DoT. For the estimation of a potential future occupancy requirements for the TVE structure, it is assumed that the average growth rates calculated for the entire

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DoT also applies to the population within FCL Zone 1. As the spatial distribution of the population increase is not known, the percentage increase was applied without refined spatial distribution. The estimate of increase to the visitor population was applied to both multi-day visitors and day-trippers. The number of people per building and per resort were also increased through the same proportions.

Any future occupancy requirements of the TVE structure is a function of DoT planning and future developments. Such plans have not been reviewed in detail for this preliminary assessment of population growth specific to the Chesterman Beach Area. A more detailed assessment of population growth should be considered to ensure that the structure provides the expected level of functionality at the end of its service life, is not potentially oversized, or to determine whether more TVE structures need to be considered at other locations.

Table 3. Expected population and growth rates for entire district as provided by DoT

Predicted DoT Overall Yearly Average Type of Report DoT Population Increase Increase Growth Population Author Population in 2016 (%) (%) Rate (%) in 2070

Opus 1,932 3,520 82 2.5 Resident Ekonics 2,000 3,000 50 1.7 2.4 DoT 1,967 4,106 109 3.1 Opus 1,742 2,782 60 2.0 Visitor1 Ekonics 2,000 3,000 50 1.7 1.9 DoT (Opus) 1,742 2,782 60 2.0 Opus 2,102 2,558 22 0.8 Transient Ekonics n/a n/a n/a n/a 0.8 DoT 1,000 >1,000 n/a n/a

Notes: 1. Assumed to Include both multi-day visitors and day-trippers population types. Evacuation Pathways

Based on the tsunami warning time and speed of travel outlined above in Table 2, the distances that a person under and over 65 can travel within the available travel time are estimated. During the day, people under 65 can travel approximately 1,785 m within the available travel time, and people over 65 can travel approximately 1,440 m within the available travel time. During the nighttime, people under 65 can travel approximately 535 m within the available travel time, and people over 65 can travel approximately 430 m within the available travel time. The reduced distances are due to lower travelling speeds at night time as a result of more difficult travelling conditions.

The evacuation pathways from buildings are delineated along passable roads and pathways from the buildings to areas of refuge. Beach evacuation pathways were based the combined linear distance along

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 29 Final Report the beach access trails and roads to areas of refuge, and radial distance on the beach. The radial distances on the beaches were evaluated separately for both people under 65 and people over 65.

While additional buildings and populations may be within the maximum travel distances when measured directly from areas of refuge (i.e., in a straight line), for this assessment, travel is assumed to be along existing official trails and roads. As new pathways are established in the future, the occupancy requirement of the TVE structure should be reassessed.

The purpose of this calculation is to estimate how many individuals in the Chesterman Beach Area, who could not evacuate to any other high ground location, could potentially be saved by having a TVE structure at the identified location. This is estimated by assessing the number of people who could reach the TVE and no other high ground areas. This assumes all evacuees including tourists learn appropriate evacuation routes and follow this learned behaviour. This calculation was done by removing from consideration the buildings and beach areas where people can evacuate to other locations, and estimating the number of people who remain in the Chesterman Beach evacuation zone.

This provides a lower-bound estimate of the capacity, or the loss of life avoided (LoLA) by installation of the structure based on the number of people who could reach the TVE but are not able to reach any other evacuation location. It should be noted that the actual occupancy requirement for the TVE structure may be higher than the LoLA as people who could technically reach natural high ground may evacuate to the TVE structure instead. An estimate of the maximum number of people who could reach the TVE structure are presented in Section 3.4.

Figure 20 shows the areas from which, and individual pathways along which, people in the Chesterman Beach area could reach potential refuge areas on natural high ground (green), and the location from which they could not (red). This highlights the region from which it is not possible to reach higher ground and from which individuals would require a TVE structure to survive the tsunami. Based on the population spatial distribution presented above, this suggests that, approximately 795 individuals would become causalities without access to a TVE during the daytime, and 95 people would become casualties without access to a TVE during the nighttime in a present day scenario. When adjusting for expected population growth by the year 2070, approximately 1,780 people would become casualties without the TVE structure in the daytime, and approximately 240 people would become casualties during the nighttime. The LoLA is lower at nighttime as most people in the Chesterman Beach area cannot reach the TVE or any other high ground based on the longer evacuation start time and slower travel speeds at night in comparison to during the day. It should be noted that a lower LoLA at night does not signify a lower number of causalities, but a lower number of individuals for which it is possible to reach the TVE structure in time.

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Figure 20. Areas (red) from which loss of life could be prevented by a TVE structure at the proposed location. Green shows areas where evacuees could technically reach the proposed TVE structure but are also within reach of nearest natural high ground refuge areas.

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3.4 Occupancy Requirements for TVE Structure

As per Evacuation Assessment

Based on the inputs and assumptions outlined in Section 3.3.1, the maximum number of people who could technically reach the TVE structure is estimated. Figure 21 shows the pathways of individuals who could reach the TVE structure based on the evacuation paths determined, the speed of travel and corresponding maximum evacuation distance. For the Chesterman Beach Area, there are 131 buildings which could be evacuated by the TVE structure during the day by people under 65, and 106 buildings which could be evacuated by the TVE during the day by people over 65. At nighttime, there are 25 buildings which could be evacuated by the TVE during the night by people under 65, and 17 buildings which could be evacuated by the TVE during the night by people over 65. Approximately 90% and 80% of Chesterman Beach north can be evacuated by the TVE during the daytime for individuals under and over 65, respectively. Approximately 80% and 60% of Chesterman Beach south can be evacuated by the TVE during the daytime for individuals under and over 65, respectively.

Based on assumptions outlined above, 1,175 people could theoretically reach the TVE structure during the daytime, and 95 people could be expected to reach the structure during the nighttime based on current population. Based on predicted 2070 populations, 3,025 people could theoretically reach the structure during the daytime, and 240 people could theoretically reach the structure during the nighttime.

It should be noted that the maximum occupancy requirements for the TVE structure, which is governed by the daytime evacuation scenario, could be reduced by developing other potential refuge areas and by clearly indicating to the public which designated refuge area is closer to where they are located.

Based on the assumptions considered for the assessment, it should also be noted that the occupancy requirements of the structure is not affected by the selection of a more severe earthquake scenario. This is because the area from which is technically possible to reach the TVE structure in time is completely inundated under the Mw 9.0 earthquake scenario.

Adjusted for Conceptual Development

To account for the uncertainties of the evacuation assessment, notably in population distribution which are suspected to be low (personal communication with Keith Orchiston April 28, 2019), it is recommended for the purpose of concept development that the maximum occupancy requirement for the TVE structure be doubled to 2,400. This is to help ensure that the actual concept selected as part of this Scoping Study is scalable, either upwards of downwards, and doesn’t have to change significantly following a better assessment of population distribution.

It was also discussed with the DoT that, given the considerable uncertainty in population growth specific to the Chesterman Beach area, future requirements for occupancy would potentially be handled by developing additional TVE structures.

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Figure 21. Evacuation pathway of individuals within Chesterman Beach Area who could technically reach the TVE structure. Orange indicate the survivable pathway of individuals under 65 and overlaying yellow the survivable pathway of individuals over 65.

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4 CONCEPTUAL DEVELOPMENT OF TVE STRUCTURE

4.1 Functional Requirements

Several options are possible for a TVE structure which may vary greatly in terms of purpose, services, size, character, etc., and an important step in the development of a TVE structure is the establishment of requirements for the structure’s functionality.

For this Scoping Study, functional requirements have been selected considering simplicity and safety as the main philosophies for design. Functional requirements however are meant to evolve as the preferred concept is refined in consultation with the DoT and public consultation if the TVE structure is further considered as part of the District’s overall tsunami risk mitigation planning.

The TVE structure at Chesterman Beach is meant to serve as a short-term tsunami refuge for occupants to survive tsunami flooding, in contrast to a shelter which would house occupants for a longer stay. Accordingly, no enclosure (i.e., walls) is considered for the TVE structure at this stage.

It is important to understand that there is a possibility that a tsunami occurs during winter months, and given that a tsunami can result in several waves lasting over several hours and make affected areas difficult to access, the subsequent survival and well-being of the structure’s occupants may become a concern. This may be affected also by the preparedness and capacity of local and external emergency responders.

As requested by the DoT at this stage, the TVE structure Chesterman Beach is meant to be a single- purpose facility. In comparison with a multi-purpose facility, a single-purpose facility may have the following advantages (FEMA, 2012):

§ Single-purpose, stand-alone structures will likely be simpler to design, permit, and construct because they will not be required to provide normal daily accommodations for people. § They will always be ready for occupants and will not be cluttered with furnishings or storage items for other uses. § They do not need to be compromised by design considerations for potentially conflicting usages. A single-purpose facility may also have lesser maintenance and surveillance requirements as it is generally composed of less components and systems. It may also provide opportunities for “companion” uses, which may include, for instance, open community space, an elevated viewing area, roof garden, etc.

Although not considered at this stage, a multi-purpose TVE structure can also have advantages. Example of such purposes are community public spaces, recreation facility, exhibition, parking, etc. An advantage

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 34 Final Report of a multi-purpose TVE structure is the possibility for a return on investment through daily business or commercial use when the structure is not needed as a refuge. A CSZ tsunami is an extremely rare event and a TVE structure will be rarely, if ever, used over its service life as a refuge. As such, a multi-purpose facility has the co-benefit of being able to utilize the community space and provide alternative benefits to the community.

While tsunamis are generally considered to be short-duration events, tsunamis include several cycles of waves. According to FEMA (2012) The potential for abnormally high water levels and coastal flooding can last as long as 24 hours. Site-specific model results by the UoO (2019) suggest that tsunami effects just offshore of Chesterman Beach would last at least 3 hours following the earthquake. Further analysis of model results is required to fully understand how long the flooding hazard will last and when it would be safe for emergency responder to rescue evacuees from the TVE structure.

Following the 2011 Tohoku Japan tsunami, several evacuees were stranded for many days at evacuation sites that were not equipped to serve survival needs (EERI, 2011). Neither food nor water was stored on the premises, nor were blankets or bedding; there were no sanitary facilities and no access to first aid or emergency medical care. Winter temperatures were close to 0° C in much of the Tohoku region. Some elderly and injured tsunami survivors succumbed to the difficult conditions after extended time at such evacuation sites.

At this stage, services and supplies available to occupants have not been addressed. However consideration should be given to aspects such as basic sanitation, food and water, blankets, medical care, etc. NHC visited a TVE structure near Kamakura, Japan, in which supplies were made available for the structure’s occupants (Figure 22) and contained in a unlocked box.

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Figure 22. Storage box containing supplies at TVE structure near Kamakura, Japan (Photo: Philippe St-Germain, 2018).

Sizing of a TVE structure depends on the intended number of occupants, the type of occupancy, and the duration of occupancy. FEMA (2012) recommends a minimum square footage per occupant of 0.93 m2 (10 square feet) per person based on the recommendations employed in the design of shelters for other hazards. It is anticipated that this density will allow evacuees room to sit down without feeling overly crowded for a relatively short period of time, but would not be considered appropriate for longer stays that included sleeping arrangements. Space for other potential functional needs, such as sanitation, supplies, communications, and emergency power, should be added to the overall size of the structure as required.

As per the results of the evacuation assessment presented in Section 3.3, an occupancy requirement of 2,400 individuals is being considered below. According to FEMA guidelines, a total surface area of 2,232 m2 is required above the Minimum Refuge Elevation. The latter is defined in Section 4.2.3.

A staged approach, in which additional levels may be added subsequently after initial construction, could be considered to address financial constraints and the uncertainties associated with the population data used for the determination of the structure’s occupancy requirement.

A TVE structure recently built at the Gordon Spratt Reserve in Tauranga City, New Zealand, considered an area of 1 m2 per person (Tauranga City, date of publication unknown). The structure itself consisted of a soil berm and was designed for 3,800 occupants.

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To provide refuge from tsunami inundation, TVE structures must have the ability to receive a large number of people in a short time frame and efficiently transport them to areas of refuge at higher elevations. This access should be open to pedestrian at any time of the day or night.

While stairs are a traditional method of ingress and vertical circulation in buildings, ramps are more effective for moving large numbers of people into and up to refuge areas in a structure (FEMA, 2012). They also facilitate access for individuals with reduced mobility. Accordingly, the access to the Minimum Refuge Elevation should ideally be provided by a ramp (or ramps) in addition to stairs.

For the TVE structure alternatives developed conceptually for this Scoping Study the widths considered for access paths, walkways, and ramps varies from 2.5 m to 3 m have been considered while a width of 2 m has been considered for internal staircases. Ideally, a ramp should be at an average gradient of less than 5% to be easily traversed by a broad range of user ability and avoid the need for level landings/rest areas and handrails. However, building code requirements for access/egress for such a large group of people require more research and investigation. Furthermore, the time required for people to reach the minimum refuge elevation should be accounted for in the travel time required for evacuation. Access and egress components will be significant visual elements with associated costs.

4.2 Design Criteria and Design Considerations

This section of the report presents the design criteria as well as codes and standards considered for conceptual design of the TVE structure. This information is considered incomplete and should be updated as the design of the structure progresses.

Definitions, parameters and associated symbology presented in this report follows as much as possible the ones used in the American Society of Civil Engineers (ASCE) Tsunami Loads and Effects design standard (ASCE, 2016). Some aspects of the standard are presented and summarized herein to provide some context to the design criteria established, although this report does not constitute a substitute to the ASCE 7-16 standard, or any other code/standard mentioned below, and such should be strictly referred to for design.

Structural engineering aspects presented below were provided by Gygax Engineering Associates.

The TVE structure is expected to remain in service for 50 years.

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To provide safe occupancy, the TVE structure must withstand a major earthquake, any aftershocks, potential liquefaction and several tsunami waves which can result in impacts with floating debris and scouring of nearby soils. Consequently, the TVE structure and its systems must be extremely robust.

The TVE structure shall be designed in accordance with the BC Building Code 2018 (BCBC), supplemented by guides and annexes to the National Building Code of Canada 2015, as applicable. Tsunami loads and effects are recommended to be established as per Chapter 6 of ASCE 7-16. Foundation design shall satisfy requirements of BCBC and ASCE 7-16 with regard to scour.

The design of buildings in British Columbia generally follows a performance level approach which takes into account the degree of acceptable structural damage as a result of exposure to a natural hazard. Following an earthquake, typical buildings are generally designed such to provide “life safety” performance, i.e. they allow the safe evacuation of their occupants but will likely require extensive repair (or reconstruction) prior to reuse. As a post-disaster facility, the TVE structure shall fulfill a higher structural performance level. It must remain fully operational after an earthquake and associated tsunami. Such an “immediate operation” performance level corresponds to the Risk Category IV according to the ASCE7-16 standard. The design of structures with an immediate operation performance level can be achieved by considering an earthquake with a return period of 2,475 years with an importance factor of 1.5. Such factor is to increase the design seismic forces in order to provide assembly structures with additional seismic resistance. An alternative approach is to consider a lower- frequency design earthquake, such a 10,000 event. Some level of dynamic analysis, as stipulated by BCBC, should be used for determining seismic demand.

There is relatively little understanding of the relationship between a CSZ earthquake of such severity and the characteristics of the resulting tsunami on the BC coast. This is mainly because the probability of occurrence of tsunamis on the BC coast remains to be officially established, in comparison to the extensive geological assessments that have been completed in the Unites States. Prior to preliminary design of the TVE structure, it would advisable to define tsunami loading and effects that would corresponds to an CSZ earthquake of the same return period as considered for seismic design.

The design for an immediate operation performance level involves additional design requirements in comparison to buildings with life safety performance level. For the TVE structure, these requirements include resilience to resist multiple load cycles without loss in strength, the ability to withstand a tsunami immediately after a significant earthquake (recognizing that the load demands due to these two events are quite different) and limitations on permanent drift after a seismic or tsunami event.

The choice of structural system and the arrangement of lateral load resisting elements, are key to providing a robust and resilient facility. High-level conceptual deliberations suggest that a concrete structural system offers advantages over a steel one for the TVE structure as the required robustness is easier to detail and less costly. Hence, a concrete construction is recommended and is considered for conceptual design of the TVE structure as part of this assignment.

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A simple, symmetrical arrangement of lateral load resisting elements (LLREs) reduces additional demand due to torsional effects and the TVE should include either a centrally located concrete core, or a balanced arrangement of shear walls to resist the large lateral forces. The effective length of columns should be determined considering scour and liquefaction effects. Soffit drop panels, slab-bands or beams will likely be required to connect the slabs to the LLREs in a manner that can withstand multiple load cycles without loss of strength.

The hydrodynamic design criteria considered for conceptual design of the TVE structure is established according to the numerical inundation modelling undertaken by the University of Ottawa (UoO, 2019). Hydrodynamic design criteria is defined at an approximate location near the center of the lot available for the TVE Structure as designated by the DoT. General characteristics of the lot are presented in Section 3.2.

It should be noted that at this stage no preliminary design has been undertaken for the preferred TVE structure alternative, and that the only hydrodynamic design criteria considered thus far in conceptual design is the Maximum Modelled Inundation Depth. It was used for defining the Minimum Refuge Elevation as described below.

As it is recommended that TVE structures be located away from the tsunami wave breaking zone and not too close to shore, a more detailed evaluation of the model results should be performed to determine if, according to the current potential site, tsunami wave breaking forces need to be accounted for in design.

ASCE 7-16 prescribes the evaluation of three Inundation Load Cases under which a structure should resist a tsunami:

§ Load Case 1: Most adverse combination of hydrodynamic force with buoyant force. Need not to be applied to Open Structures nor to structures where the soil properties or foundation and structural design prevent detrimental hydrostatic pressurization of the underside of the foundation and lowest structural slab. § Load Case 2: Depth at two-thirds of maximum inundation depth when the maximum velocity and maximum specific momentum flux shall be assumed to occur in either incoming or receding directions. § Load Case 3: Maximum inundation depth when velocity shall be assumed at one-third of maximum in either incoming or receiving directions. ASCE 7-16 provides normalized design curves for the relative time evolution of inundation depth and flow velocity for the determination of Load Cases 2 and 3. Such curves, which requires the maximum inundation depth and maximum flow velocity to be known, can be considered for preliminary design purposes. For detailed design, it is recommended to evaluate Load Cases 2 and 3 based on site-specific

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 39 Final Report tsunami analysis (e.g., model results of time evolution of inundation depth and flow velocity at the structure location).

Maximum Modelled Inundation Depth

The maximum inundation depth (i.e., depth of water above existing ground level) of hmax = 4.6 m is predicted near the center of the TVE structure location.

Maximum Modelled Flow Velocity

A maximum depth-averaged flow velocity of umax = 3.3 m/s is predicted near the center of the TVE structure location. This incoming velocity is expected to occur in the landward direction perpendicular to the shoreline at North Chesterman Beach. However, preliminary and detailed design should account for the influence of the combined flow coming from potentially varying direction (i.e., from Chesterman Beach North and South) and as the water is receding.

Minimum Refuge Elevation

According to ASCE 7-16, tsunami refuge floors shall be located not less than the greater of 3.1 m (10 ft) or one-story height above 1.3 times of the maximum considered tsunami inundation elevation at the site as determined by a site-specific inundation analysis. It should be noted that the tsunami “inundation elevation” is different then the tsunami “inundation depth”, the former being with respect to a vertical datum and the latter with respect the elevation of the ground at the site.

For a ground elevation of 6.9 m (CGVD2013) near the center of the lot and a maximum inundation depth of 4.6 m, the maximum inundation elevation is 11.5 m (CGVD2013). Applying the factor of safety described above, the minimum elevation of the lowest occupiable refuge level is:

1.3 × 11.5 m +3.1 m = 18.1 m (CGVD2013)

This calculation is described graphically in Figure 23, which shows as example a TVE structure consisting of a life-saving tower with several floors.

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Figure 23. Definition of Minimum Refuge Level Elevation (Adapted from ASCE7-16). Elevations with respect to CGVD2013 Access stairs and central core not shown for representation purposes.

During a tsunami event, structures can be subject to impact loads as a result of debris such as poles, logs, vehicles, boats, tumbling boulders, concrete pieces, and shipping containers becoming entrained in the tsunami and striking the structure.

At Chesterman Beach, the main debris which can be expected to affect the TVE structure are vehicles, uprooted trees, and potentially large rocks used as shoreline protection along the beach. With no container terminal in Tofino, impact with shipping containers is not expected, although some residents use them as housing units or storage purposes and a few may be present in the Chesterman Beach Area.

Tofino Harbour is located relatively far away from Chesterman Beach, suggesting that impact with boats is also unlikely. However it may be possible that as the first tsunami wave recedes, boats may be carried offshore where they could be swept onshore at Chesterman Beach by a subsequent tsunami wave. It is also possible for boats navigating close to Chesterman Beach to become floating debris. Further assessment would be required to confirm such eventualities.

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Because of density of trees in the area, the potential for debris “damming” should also be assessed carefully as such process can significantly increase hydrodynamic loads. Debris damming consists in the accumulation of debris in front of a structure due to the incoming flow, and which results in a significant increase in forces to the larger flow obstruction it creates. The layout of the TVE structure should be such that the potential for debris damming is minimized.

There is very limited geotechnical information specific to the Chesterman Beach area. Available information in the Tofino area includes:

§ Soil cover down to a depth of approximately a metre (e.g., Baker, 1969) § General geology of the Pacific Rim National Park (Lang and Muller, 1975) § Geotechnical assessment report related to the design of the wastewater treatment plant in Tofino’s industrial area (Exp Services Inc., 2018) For the Chesterman Beach area, Baker (1969) suggests the presence of a layer of marine clay on top of bedrock (Figure 24). This clay layer either extends to the ground surface or is under a sand layer of unknown thickness. Depth of the bedrock, geotechnical soil properties, and the location of the water table are not defined by the report.

The geotechnical information found in Exp Services Inc. (2018) is considered not relevant to the project site because of distance and potential variations in ground conditions between the industrial area and the proposed location of the TVE structure. For this reason specific geotechnical investigations are required. Because of the considerable size of the TVE structure and significant seismic and tsunami forces it needs to withstands, soil conditions are expected to have important implications on the design of foundations and subsequently a large portion of the project’s cost.

Liquefaction is a phenomenon in which the strength and stiffness of a water-saturated soil is reduced by earthquake shaking or other rapid loading. In this process, the water within the soil particles exerts a pressure that influences how tightly the particles themselves are pressed together, hence reducing the load bearing capacity of the soil. Soils composed of silt, sand, and gravel are generally more prone to liquefaction, although to which degree depends on an array of parameters such as soil gradation, composition, and grain angularity. Clayey soils and soft clays may exhibit strain-softening behavior similar to that of liquefied soil, but do not liquefy in the same manner as sandy soils.

The TVE structure’s foundation should be designed to account for effects of soil liquefaction, settlement, and scour, as required depending on site conditions and foundation type. In conjunction with site- specific geotechnical data, the potential for the former two shall be assessed by a geotechnical engineer and potential for scour by a hydrotechnical or coastal engineer.

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Figure 24. Schematic diagram showing relationships among soils and surficial deposits in relation to points indicated on upper image (Baker, 1969).

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Architectural requirements of the TVE structure shall be established in accordance to applicable codes in the province of British Columbia. Particular attention is required to the structure’s access to ensure that quick travel to the minimum refuge level is not restricted.

It is likely that, as a structure intended for public assembly, the structure will require the seal of a registered architect in the Province of British Columbia. In the design development stages of the project, a qualified architect and building code consultant should be engaged early in the process to explore and confirm occupancy, access/egress requirements and other code requirements.

Because of the required structural performance level of the TVE structure as described in Section 4.2.2, it is recommended that architectural design take place in close collaboration with preliminary structural design.

4.3 TVE Structure Alternatives

Based on the functional requirements set forth above, various alternatives for tsunami refuges were developed for this study at a conceptual level. The alternative are classified in three main categories (listed below), and are presented in the sub-sections below along with the key considerations for their development. Because of the single-purpose functional requirement, buildings were not considered as a category for a TVE structure at Chesterman Beach as they would fulfill multiple purposes in addition to a tsunami refuge.

§ Tower – Stand-alone structures with platforms at the top for people to gather which have been built in several locations in Japan. § Soil Berm – Artificial, engineered hills that provide high ground which have been built in Japan and New Zealand. § Hybrid – A soil berm with platforms on top which has been considered as part of the conceptual options developed for the Project Safe Haven in the state of Washington. The alternatives were developed for simplicity of understanding scale and mass with no adornment or architectural enhancement. Rendering of the alternatives by the study team allowed for the investigation of structure types, structure footprints, and access options within the site-specific context of Chesterman Beach. Alternatives were explored that minimize height and visibility from important vantage points, especially from the beach area, to minimize visual impacts and potentially encourage public support for the project. On the other hand, it could be advantageous to make the TVE structure more visible as this would make its location more obvious during evacuation.

With the exception of the soil berm alternative, the gross floor areas for each structure exceed the target total area for refuge. However, the net areas are expected be closer to target due to stair, access requirements, storage, emergency provisions, and other such necessary details not included in the design at this stage. Precise refuge areas would be calculated during design development stage.

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It should be noted that the renderings presented below do not reflect all aspects of structural design discussed in Section 4.2.2. Because consideration of such aspects is anticipated to result in concepts with more apparent robustness, which would result in a stronger visual impact, it is recommended that any alternatives presented to the public be updated for correctness.

A tsunami evacuation tower can take the form of a simple elevated platform(s) above the predicted tsunami inundation level. Such platforms would be accessed by a specifically designed ramp and/or stairs. An example of this type of TVE structure near Kamakura, Japan was visited by NHC and is shown in Figure 25.

Being stand-alone structures intended to provide temporary high elevation refuge for evacuees to survive tsunami inundation, “life-saving” towers tend to be simpler in design and more economical than multi-purpose buildings. They also generally require a smaller footprint compared to other TVE structure options, allowing for other uses of the property they are on.

Figure 25. Tsunami vertical evacuation tower recently constructed near Kamakura, Japan (Photo: Philippe St-Germain, 2018)

For this Scoping Study, towers of varying footprint geometry and surface area were rendered for comparison. Three footprint geometries were considered for this assessment: square, rectangular, and circular.

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To fulfill the occupancy requirement, the structure must have either an approximate footprint of 600 m2 with three stories of refuge structure and an occupiable roof deck, or an approximate footprint of 900 m2 per floor with two stories of refuge structure and an occupiable roof deck. With the current uncertainty in both the current and future population estimates considered as inputs to the evacuation assessment, these two footprint areas were considered by the consultant as a suitable balance to provide safe refuge and overhead cover for the majority of the target population, while minimizing the number of storeys to mitigate costs and reduce visual impacts.

Stairs, which would account for the primary mean of access the tower, would be ideally located and protected inside a centrally located concrete core that functions to provide structural resistance to seismic loading. Such detail is not shown in the rendering presented in this report.

Access to the tower should also be provided by ramps to accommodate evacuees with impaired mobility. Conceptually, the ramp components are located outside of the columns due to head room requirements and loss of floor space if internally located. The illustration below does not show the support components of the ramp and the ramp design needs to be investigated further should this option be selected for further study. It is important that any ramps be designed to withstand forces they may be subjected to. For illustration purposes, an access ramp is only shown with the square footprint, but it should be considered for other footprint geometries as well.

The space at grade below the first floor may become a security and neighbourhood issue, representing a long term operational and enforcement problem. There will be a “forest” of concrete columns with a hard surface or gravel floor. The space could attract unwanted behavior such as free camping, vandalism, and social gathering due to the weather protection the structure will offer. The facility will require operations and enforcement commitments to balance the behavior and security issues while keeping the facility open and available for an emergency. Security fencing at the ground level to prevent unauthorized access would be at cross purposes to facilitating rapid evacuation to upper levels in the event of a tsunami.

General Description

Renderings of a life-saving tower with a square footprint are shown in Figure 26 and Figure 27. The corners of the structure are in the incoming and receding flow directions to reduce the potential for debris jamming and deflect floating debris away from the structure. The columns around the perimeter of the structure may have to be of stronger design depending on expected debris impact loads.

General Dimensions

§ Gross footprint area of 650 m2 § Three stories with an occupiable roof deck (i.e., 4 levels) § 2,600 m2 total refuge area (gross)

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Preliminary floor and column layout for the square tower alternative is shown in Figure 28.

Occupancy

Considering the surface area occupied by the central concrete core (approx. 56 m2), the occupancy of the square tower alternative is approximately 640 individuals per level resulting in a total of 2,560 evacuees.

Figure 26. Rendering of square life-saving tower alternative. Central core and support for access ramp not shown, location of stairs subject to change.

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Figure 27. Bird’s-eye view rendering of square life-saving tower alternative. Central core and support for access ramp not shown, location of stairs subject to change.

Figure 28. Preliminary floor and column layout for square life-saving tower alternative (dimensions in metres). Access stairs and central core not shown for representation purposes.

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General Description

Renderings of a life-saving tower with a rectangular footprint are shown in Figure 29 and Figure 30. The structure’s longest dimension is aligned in the predominant incoming and receding flow directions to minimize the potential for debris jamming. A series of protective columns in a “V” formation are positioned into incoming and receding flow directions to protect the inner columns against debris impact. From an aesthetic point of view, to mitigate visual impacts on adjacent resident, the outside of these columns may be of architectural and/or artistic character.

General Dimensions

§ Gross footprint area of 670 m2 § Three stories with an occupiable roof deck (i.e., 4 levels) § 2,680 m2 total refuge area (gross) Preliminary floor and column layout for the square tower alternative is shown in Figure 31.

Occupancy

Considering the surface area occupied by a central concrete core (approx. 56 m2), the occupancy of the rectangular tower alternative is approximately 660 individuals per level resulting in a total of 2,640 evacuees.

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Figure 29. Rendering of rectangular life-saving tower alternative. Central core and access ramp not shown, location of stairs subject to change.

Figure 30. Bird’s-eye view rendering of rectangular life-saving tower alternative . Central core and access ramp not shown, location of stairs subject to change.

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Figure 31. Preliminary floor and column layout for rectangular life-saving tower alternative (dimensions in metres). Access stairs and central core not shown for representation purposes.

General Description

A circular geometry was also considered for the life-saving alternative, although no rendering has been produced at this stage. Advantage of this geometry is that it can for any flow direction deflect floating debris reasonably well, potentially avoiding the need for stand-alone protective columns and offers relatively lower flow resistance. It may be considered more aesthetically appealing since there are no sharp corners.

General Dimensions

§ Gross footprint area of 910 m2 § Two stories with an occupiable roof deck (i.e., 3 levels) § 2,730 m2 total refuge area (gross) Preliminary floor and column layout for the square tower alternative is shown in Figure 32.

Occupancy

Considering the surface area occupied by a central concrete core (approx. 56 m2), the occupancy of the circular tower alternative is approximately 920 individuals per level resulting in a total of 2,760 evacuees.

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Figure 32. Preliminary floor and column layout for circular life-saving tower alternative (dimensions in metres). Access stairs and central core not shown for representation purposes.

General advantages of a life-saving tower alternative include:

§ Generally more economical than other alternatives due to their simplicity. § Standards are available for design reducing efforts for design and engineering assessments. § Floors can be added in phases to address uncertainty in population estimates and fund availability. § Relatively small footprint, potentially allowing for other use of the remaining property area. § Provides architectural opportunities.

General disadvantages of a life-saving tower alternative include:

§ May be considered to have greater visual impacts. § Cost depends on soil conditions as they will affect the choice and design of foundations. § Access and egress to structure must be assessed carefully by qualified professionals.

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§ Must adhere to architectural and building code and standards which require additional assessment. § Sheltering at ground level may attract unwanted behaviour such as un authorized camping and potential for vandalism. This will require operational maintenance and enforcement commitments.

General Description

Earth mounding on the candidate site was explored using digital terrain modelling, and the elevation and area of the plateau were established for planning and illustration purposes. A three-metre offset from the property line was delineated as a zone to contain/control site runoff and to establish a line of grading limits. Side slopes are estimated at a range of 3H:1V to 2.5H:1V, which limits the height of the plateau, set to 14.5 m with respect to CGVD2013, and resulting in a refuge area of 900 m2. A rendering of the alternative is shown in Figure 33.

Raising the grade to an elevation of 14.5 m requires a pedestrian ramp and perhaps stair structures to access the refuge area. The ramp, as illustrated in Figure 34, is 2.5m wide with an average gradient less than 5% from the south east corner of the site to the top of the berm (9.3 m elevation gain over 188 linear metre). It is possible to also add staircases from several points along the ramp directly to the top elevation.

The elevation of 14.5 m is below the 18.1 m minimum refuge elevation as prescribed by ASCE 7-16, but 3.0m above the maximum considered tsunami inundation level as predicted by numerical modelling (UoO, 2019). The achieved area of 900 m2 is less than half the 2,232 m2 required according to the outcomes of the evacuation assessment. We would expect that evacuees reaching the plateau in an emergency would be provided with some level of safety, however the safety performance of such alternative would need to be taken into careful consideration if it is to be pursued further.

Accordingly, a concept considering the use of retaining walls to increase the elevation of the of the refuge area as well as increase the achieve refuge area itself is presented further below.

Furthermore, this option could be considered as part of a phased construction where a one (or more) storey structure could be built on top of the berm when warranted. The combination of a structure on the berm is considered as a hybrid alternative and is presented in Section 4.3.3.

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Figure 33. Rendering of soil berm alternative

Figure 34. Plan view of soil berm alternative showing access ramp and stairs.

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Unless additional land surface is acquired adjacent to the available lot, earth retaining walls are required in order to increase the elevation of the refuge area to ASCE 7-16 requirements and to increase the achieve refuge area itself. A schematic of such concept of an example of such concept is presented in Figure 35. It should be noted many other variations of such concept may be feasible and were not explored as part of this study.

The access slope shown considers a gradient of 3H:1V. A combination of an access ramp with switchbacks in combination of with stairs going straight up the slope could be elaborated to further improve ease of access.

Figure 35. Plan view schematic of potential soil berm alternative using retaining walls and 3H:1V access slope.

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Earth materials for construction of soil berm alternatives will have to fulfil certain engineering requirements and its revetment, whether exposed or covered by soil for landscaping purposes, will need to withstand erosive forces from tsunami and debris flow (advancing and receding). Any retaining walls will need to be designed to withstand seismic forces as well as hydrodynamic and debris impact forces induced by the tsunami. In addition to the evaluation of the berm stability, geotechnical investigations will be required to assess potential for vertical or lateral earth movement impacts to adjacent properties.

General Dimensions

Table 4. General dimensions of soil berm alternatives. Berm with Slopes on Berm with Retaining Parameter All Sides Walls Top elevation (CGVD2013) 14.5 m 18.1 m Slopes 3H:1V to 2.5H:1V 3H:1V Volume of fill material 25,000 m3 34,400 Refuge area 900 m2 2,232 m2

Occupancy

Unless steeper side slopes are considered, the occupancy of the soil berm alternative with slopes on all sides is limited to approximately 970 individuals, which is less than the 2,400 individuals required according to the outcomes of the evacuation assessment. However, this occupancy requirement may be achieved considering the use of retaining walls.

Advantages

§ Relative simplicity of construction. § Allow people to follow their natural instinct to evacuate to high ground. § Large open areas offer easy access by a reasonably large numbers of evacuees with the added advantage of avoiding the possible apprehension about entering a building following an earthquake. § Soil berms have the added benefit that they are generally immune to damage from debris strikes. § Construction could potentially be cost-effective in comparison to building a stand-alone structure, although this needs to be further evaluated based on site-specific geotechnical investigations, fill material availability, and further engineering assessments. § Alternative can also be used to provide additional community amenities on the top level (e.g., parks, sports courts, etc.).

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§ Does not provide covered area which may attract unwanted behaviour such as camping or vandalism. Disadvantages

§ Given the space on the available lot, requires the use of retaining walls in achieve the minimum refuge elevation as prescribed by ASCE 7-16 and to provide the required refuge area as determined by the evacuation assessment. § Cost of soil berm highly dependant on soil conditions and availability of fill material. Aspects which are unknown without further investigations. § Requires specific engineering assessments as no standard or code exist for their design with respect to tsunami loading and effects. Such assessments include stability of the berm and any retaining walls to resist the erosive of the tsunami and debris flow as well as the wave effects (e.g., runup).

General Description

This alternative consists of platforms constructed onto of the soil berm alternative presented in Section 4.3.2. Renderings of this hybrid alternative are shown in Figure 36, Figure 37, and Figure 38. An ellipsoidal footprint was considered for the platforms following the geometry of the soil berm. A varying footprint shape may be considered depending on the soil berm geometry as well.

A particularly attractive aspect of this alternative is the ease of access provided by the berm. Furthermore, this alternative may be considered to have lesser visual impacts as fewer structural columns are visible at the ground level. This design could also be phased by adding additional decks to account for uncertainty in population estimates and fund availability.

An important aspect of this alternative which would require careful consideration is the functionality of the soil berm. Although it may provide better access, minimize visual impacts and help deflect debris, it does not have considerable structural benefits to the foundations of the structure.

General Dimensions

§ Gross footprint area of 900 m2 § Two stories with an occupiable roof deck (i.e., 3 levels) § 2,700 m2 total refuge area (gross) Preliminary floor and column layout for the square tower alternative is shown in Figure 39.

Occupancy

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Considering the surface area occupied by a central concrete core (approx. 56 m2), the occupancy of the hybrid soil berm with platforms alternative is approximately 910 individuals per level resulting in a total of 2,730 evacuees.

Advantages

§ Allow people to follow their natural instinct to evacuate to high ground. § Large open areas offer easy access for large numbers of evacuees as long as ease of access to upper platforms is ensured. § Soil berms have the added benefit that they are generally immune to damage from debris strikes, if it is designed to withstand the erosive forces of a tsunami. § Reduced visual impact compared to life-saving tower. § Floors can be added in phases to address uncertainty in population estimates and fund availability. Disadvantages

§ Feasibility of alternative highly dependant on soil conditions which remain relatively unknown at time of this scoping study. § Cost of a soil berm is highly dependant on soil conditions and availability of fill material (unknown without further investigations). § A soil berm requires specific engineering assessments as no standard or code exists for design of a soil berm to withstand tsunami action. Such assessments include stability of the berm to resist the erosive of the tsunami and debris flow as well as the wave effects (e.g., runup). § The presence of the soil berm is not expected to provide any benefits for the structural design of the structure’s foundations.

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Figure 36. Rendering of hybrid soil berm with platforms alternative. Central core not shown and location of stairs subject to change.

Figure 37. Bird’s-eye view rendering of hybrid soil berm with platforms alternative. Central core not shown and location of stairs subject to change.

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Figure 38. Plan view of hybrid soil berm with platforms alternative showing access ramp. Location of stairs subject to change.

Figure 39. Preliminary floor and column layout for platforms on top of soil berm (dimensions in metres). Access stairs and central core not shown for representation purposes.

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4.4 Preferred Alternative

TVE alternatives were reviewed by the Project Team and the consensus was that the life-saving tower with a square footprint and without any soil berm was the preferred alternative to be further considered for the development of an order of magnitude cost estimate. The reasons for this outcome are as follows:

§ Compared to the rectangular and ellipsoidal shapes, the square footprint inherently provides better structural performance due to its symmetry. § The formwork required to construct round edges of floors is more complex to undertake, which increases construction costs. For this reason, a life-tower with a circular footprint was not preferred. § Although providing some level of safety at an elevation of 14.5 m (CGVD2013), the soil berm alternative does not fulfill the minimum refuge elevation requirement of 18.1 m (CGVD2013) prescribed by the ASCE 7-16 standard. § Aside from potentially providing better access and providing better landscaping opportunities, a hybrid soil berm with platforms does not have considerable structural benefits to the foundations of the structure. The hybrid soil berm with platforms option is thus not preferred for simplicity and cost considerations. § Aside from potentially providing better access and providing better landscaping opportunities, a hybrid soil berm with platforms does not bring any significant structural benefits since the foundation level of the structure remains the same and the effective column length would be determined by potential scour of the berm materials. Overall, the life-saving tower with a square footprint was preferred for its symmetrical geometry which provides relatively better structural performance as well as for its simplicity of design and construction, which is expected to result in lower costs. Because of the critical function that the TVE structure needs to fulfill, architectural and aesthetical aspects were not considered in the selection of the of the preferred option at this stage.

4.5 Cursory Assessment of Visual Impact

A sample visual impact assessment of the alternatives was analyzed from various vantage points (e.g., Lynn Road, beach, etc.). The assessment depends on assumptions made about the area’s vegetation including tree density, canopy height, and the inclusion of existing land features and houses. Figure 40 shows an example of such visual assessment. The images shown in the figure represent views from the beach, with and without existing vegetation, to provide a sense of scale and relative heights. The bottom image illustrates the effects of the existing vegetation as a screen to the facility. It is anticipated that the existing vegetation would remain as-is.

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Although lesser visual impacts may increase public acceptance of the TVE structure, having less visibility may make it more difficult to find in the event of a tsunami. Accordingly, if the structure’s visibility is minimized more signage may be required to make sure it can be easily found by the tourist population.

Figure 40. Visual impacts of a life-saving tower as seen from the beach. Result may vary depending on assessment of vegetation.

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5 ORDER-OF-MAGNITUDE CAPITAL COST ESTIMATE

To develop an order-of-magnitude cost estimate for the square life-saving tower alternative, some high- level structural design was supported by inputs from Gygax Engineering Associates (GEA). These inputs are based solely on professional judgement and experience, and no specific design calculations were performed given the conceptual nature of this Scoping Study. Calculations are generally undertaken at the preliminary design stage which is outside the scope of this assignment given the relative efforts preliminary design requires and the need for better geotechnical information.

5.1 High-level Conceptual Structural Design

Conceptual structural design of the concrete TVE structure is shown graphically in Figure 41 and Figure 42, with dimensional details of the conceptual design elements summarized below:

Slab Floors

The floors and occupiable roof deck consist of 250 mm thick slab resting on a 400 mm wide and 500 mm deep beam system. Viewed from the side, the apparent thickness of the floors is then 750 mm.

At the location of columns, the slabs rest on the columns through 600 mm thick and 1200 mm by 1200 mm capitals.

Columns

Square columns in-between floors have a side dimension of 600 mm and a height of 2,200 mm from floor level to bottom edge of capitals.

Columns at the ground level have a diameter of 1,200 mm and an approximate height of 10,425 mm.

Taking into consideration the thickness of the floor slabs and the depth of the beams, the head clearance is 3,050 mm - 250 mm (slab thickness) - 500 mm (beam depth) = 2,300 mm, which is greater than requirement of 2,050 mm as per the BC Building Code.

Central Core

The walls of the concrete core have a thickness of 500 mm and a 2,5000 mm thick flat footing just below the ground level. The core footing is support by 4 foundation piles.

Foundations

Based on the limited site-specific geotechnical available at this stage, deep steel pile foundations are believed to be the most appropriate foundation system for the TVE structure. For the purpose of conceptual design, such piles are considered to be driven down to a depth of 30 m below the existing ground surface. Each column of the TVE structure is supported by a pile.

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Figure 41. Plan view of conceptual level details of TVE structure beam, column, and central core systems. (Sketch based on inputs from GEA)

Figure 42. Section view of conceptual level details of TVE structure column connections with slab and beams. (Sketch based on inputs from GEA)

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5.2 Cost Estimating

A detailed breakdown of the of the capital cost estimate prepared for the square life-saving tower alternative is provided in Appendix A. General assumptions and sources for material unit costs are presented in the subsections below. It is anticipated that the cost estimates will be updated as and if the design of the TVE structure is further developed.

Because of insufficient design details for the access ramp at this stage, this item has been neglected in the development of the order-of-magnitude capital cost estimate for the preferred TVE structure alternative.

Including contingencies indicated below, it is estimated that the construction cost of the life-saving tower with a square footprint, as presented in Section 4.3.1.2, is approximately $4.6M.

If a phased construction approach is taken, the cost of constructing the first level is estimated at $2.9M, with the cost of additional levels estimated at $0.7M. If all four levels are eventually constructed, a phased approached is more expensive to ensure structural continuity between each floor, as well as repeated contractor mobilization/demobilization costs. Structural continuity could be implemented by waiting rebar cast into temporary upstand column stubs (concrete to be chipped away subsequently), or through mechanical rebar couplers.

The order-of-magnitude capital cost estimate presented above does not include further engineering, geotechnical, and architectural design and services, nor operational and maintenance costs.

§ 50% contingency allowance for above ground structural components. § 100% contingency for foundations due to uncertainties in site-specific soil conditions. § Lump sum contractor mobilization/demobilization costs of $20,000. § Lump sum cost of $50,000 for installation of lights and associated electrical systems. § Lump sum cost of $20,000 for tree clearing and ground levelling of the site. § Ready-mix concrete available from Tofino or Ucluelet area. § 20% increase in structural costs for additional floors if constructed in phases.

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The material costs considered in the development of capital costs estimates are presented in Table 5. This information should be updated through consultation with contractors in subsequent stages of design.

Table 5. Unit rates considered for cost estimating

Item Units Rate Source of information

Site Preparation Growing medium for grass m3 $75 Lanarc Consulting Hydro seed m2 $5 Lanarc Consulting Concrete paved level area under structure m2 $90 Lanarc Consulting Access Path Asphalt with concrete edge m2 $80 Lanarc Consulting Components Above Ground Re-enforced concrete m3 $1,500 Gygax Engineering Associates Stairs flight $2,500 Gygax Engineering Associates Guardrails m $150 Gygax Engineering Associates Foundations Pile foundation pile $30,000 Gygax Engineering Associates

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6 SUMMARY

Based on a Mw 9.0 CSZ earthquake scenario results of tsunami modeling indicate an extreme level of risk for the Chesterman Beach area which is low lying and will be subject to a high depth of inundation and high velocity of the tsunami wave across a wide area. Evacuation assessments indicate that there would be insufficient time for most people in this area to reach existing high ground before a CSZ earthquake generated tsunami strikes the area. This outcome highlights the need for a TVE structure in the vulnerable Chesterman Beach Area. The evacuation assessment also showed that, given the existing official trail and road network, no one located on the east side of Highway 4 would be able to reach the TVE structure at the identified location unless additional trails are developed.

The evacuation assessment indicates that the maximum number of individuals than can theoretically reach a TVE structure located at the identified location is approximately 1,200. However, because of uncertainty in population data, occupancy requirement is doubled to 2, 400 for the purpose of conceptual development promoting concept scalability. Also, given further uncertainty in population growth specific to the Chesterman Beach area along with uncertainty around seasonal tourist numbers on the beaches in this area, it is anticipated that future requirements for occupancy will be handled by potentially developing additional TVE structures.

Because the evacuation assessment performed as part of this Scoping Study assumes all evacuees of the Chesterman Beach Area attempt to reach the TVE structure rather than naturally occurring high ground, this maximum occupancy requirement for the TVE structure (once refined), may be reduced by developing better access routes to other potential refuge areas. Accordingly, the maximum occupancy requirement for the TVE structure should be confirmed as official tsunami evacuation plans are updated in the future.

For this Scoping Study functional requirements for the TVE structure have been selected considering for simplicity and safety as the main philosophies of design. Several conceptual alternatives were developed for a short-term tsunami refuge for occupants to survive tsunami flooding. Based on such functional requirements, a minimum square footage per occupant of 0.93 m2 per person (10 square feet) was considered for sizing the five TVE structure alternatives that were developed at a conceptual level.

The life-saving tower with a square footprint was identified as the preferred alternative to be further considered for further development. Overall, this alternative was preferred for its symmetrical geometry which provides relatively better structural performance as well as for its simplicity of design and construction, which is expected to result in lower costs. Each level of the TVE structure, including the roof deck, has the capacity for 640 evacuees resulting in a total of 2,560.

To develop an order-of-magnitude cost estimate for the preferred TVE structure alternative a high-level structural design was completed based solely on professional judgement and experience, and no specific design calculations were performed given the conceptual nature of this Scoping Study. Including contingencies, it is estimated that the construction cost of the life-saving tower with a square footprint is approximately $4.6M. If a phased construction approach is planned, the cost of constructing the first level is estimated at $2.9M, with the cost of additional levels estimated at $0.7M. This order-of-

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 67 Final Report magnitude capital costs estimate does not include further engineering, geotechnical, and architectural design and services, nor operational and maintenance costs.

6.1 Recommendations for Future Assessment

This study is limited by the availability of information and the accuracy of assumptions and input data. Results of the evacuation assessment provide an estimate of the TVE structure occupancy for scoping purposes. Assumptions and input data, particularly on population distribution, should be reviewed prior to further design or before important decisions are made.

Below are several aspects for which further consideration is recommended for any development of the TVE structure in general:

Definition of Tsunami Hazard

1. For this Scoping Study, numerical model results of tsunami hazard for an earthquake scenario

with a magnitude of Mw 9.0 were considered rather than the most adverse scenario modelled

(Mw 9.3) by the UoO (2019). However, consideration should be given to the assessment by a qualified seismic geologist of the most probable and most adverse CSZ earthquakes, both in terms of tsunami generation characteristics and likelihood of occurrence.

2. Results of the evacuation assessment presented herein are likely sensitive to the tsunami arrival time as this time is short for a CSZ event. Furthermore, the flooding that may occur prior to the arrival of the main brunt of the first tsunami wave is not accounted for in this assessment. Accordingly, an “effective” tsunami arrival time should be assessed by close examination of the time history of the associated flooding and how it impacts the evacuation process.

3. The length of time evacuees will need to remain on the TVE structure requires further assessment and this may influence the functional requirements of the structure. Such occupancy will depend on the spatiotemporal characteristics of the tsunami flooding as well as the emergency response plans.

Population Data

4. Due to limited information, considerable assumptions were made with respect to population distribution, especially in buildings. Accordingly, the maximum occupancy of the TVE structure was doubled to help ensure scalability of the selected concept for the structure. Nevertheless, it is recommended that this input data be refined and results of this study revised prior to final design of the TVE structure. Refinement strategies could include: occupancy surveys of buildings during different times of day and year; aerial photos and analysis of beach population distribution; analysis of cell phone usage; use of automated or operated counters, and partnership with utility providers for analysis of utility loading.

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 68 Final Report

5. A staged approach, in which additional levels may be added subsequently after initial construction, could be considered to address financial constraints and the uncertainties associated with the population data used for the determination of the structure’s occupancy requirement.

Evacuation Assessment

6. The time at which people would start to evacuate, which have been established in collaboration with the DoT and UoO, have relatively little basis specific to Tofino’s conditions. As results of the evacuation assessment are likely sensitive to this input, it is recommended that its basis be reviewed and better defined.

7. The moving speed of evacuees varies depends on many factors including their age, fitness level, physical ability, terrain, level of preparedness, and time of day. Several studies are available providing a basis on travel speed although there is some uncertainty as to how this information applies to conditions in Tofino (walking on beaches, natural trails) and how sensitive to this parameter are assessment tools.

8. Additional evacuation scenarios could be evaluated to estimate the number of individuals who could reach the TVE structure during other times of the year. Depending on whether the DoT would like to build the structure based on a the worst-case capacity scenario, one of these other scenarios could be chosen, or scenarios could be weighted by the proportion of the year they apply to determine a temporally-weighted occupancy estimation.

Functional Requirements and Design Criteria

9. The purpose of the TVE in the Chesterman Beach area is to provide short-term refuge in the event of a near-field CSZ tsunami. Consideration should be given as per the use of TVE structure(s) and its incorporation into evacuation plans for events generated further away which provides longer evacuation time. As the TVE structure concept developed as part of this assignment does not have enclosure walls, it would likely not satisfy requirements for being considered as a longer-term shelter in case of extended stay or gathering place for far-field, or distant tsunamis.

10. It is crucial that any TVE structure be incorporated in the DoT evacuation and response plans, which in turn may affect the required occupancy for the structure, which should be confirmed as an iterative process.

11. Building code requirements for access/egress of a large group of people requires more research and investigation. Also, the time required for people to reach the minimum refuge elevation should be accounted for in the travel time required for evacuation. The evacuation assessment performed as part of this study assumed that evacuees were safe if they reached the location of the TVE structure, while in reality they are only safe once they reach the minimum refuge elevation.

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 69 Final Report

12. The structure’s future occupancy requirements estimated herein should be interpreted carefully given the relatively large uncertainty associated to the population growth assumed for the Chesterman Beach Area. Population growth was assumed as the average one for the entire district and may not take into consideration planning specific to the Chesterman Beach Area.

13. Given the existing official trail and road network, no one located on the east side of Highway 4 would be able to reach the TVE structure unless direct trails are developed. Hence the TVE structure could save a greater number of individuals if additional trails were developed, although this development may require reassessment of the occupancy requirement of the TVE structure.

14. Following the 2011 Tohoku Japan tsunami, several evacuees were stranded for many days at evacuation sites that were not equipped to serve survival needs which resulted in the death of elderly and injured people (EERI, 2011). Accordingly, consideration should be given to aspects such as basic sanitation, food and water, blankets, medical care, and other requirements for health and sanitation to ensure survival.

15. Tofino Harbour is located relatively far away from Chesterman Beach, suggesting that impact with boats is unlikely. However it may be possible that as the first tsunami wave recedes, boats may be carried offshore where they could be swept onshore at Chesterman Beach by a subsequent tsunami wave. Further assessment would be required to confirm such eventuality.

Conceptual Development 16. Site-specific geotechnical data on soil conditions is an important information gap that has implications on the design of the TVE structure, and accordingly a contingency of 100% was applied to the costs of the foundations for the purpose of this scoping study. It is crucial that geotechnical field investigations and associated assessment by a qualified geotechnical engineer be carried out in the early stages of design to address potential concerns with soil liquefaction, settlement, and scour in relation to foundation design.

17. The graphical representations of the TVE structure alternatives presented in this report do not reflect all structural aspects discussed. Because consideration of such aspects is anticipated to result in concepts with more apparent robustness, which would result in a stronger visual impact, it is recommended that any alternatives selected for further consideration be updated to include these details prior to their use for public consultation.

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 70 Final Report

7 CLOSURE

We believe this document meets your immediate needs. If you have any questions do not hesitate to contact us by phone (604-980-6011) or email ([email protected] | [email protected]).

Sincerely,

Northwest Hydraulic Consultants Ltd.

8 REFERENCES

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Atwater, B.F., Satoko, M.-R., Kenji, S., Yoshinobu, T., Kazue, U. and Yamaguchi, D.K. (2005). “The orphan tsunami of 1700 – Japanese clues to a parent earthquake in North America”, United States Geological Survey (USGS), Professional Paper No. 1707, 144 pp.

Baker, T.E. (1969). “The major soils of the Tofino Area of Vancouver Island and implications for land use planning and management”, thesis, University of Alberta, Edmonton.

Cascadia Coast Research LTD. (2018). “Coastal Flood Hazard Analysis: The Regional District of Tofino, BC.”, Dated December 17, 2018.

Cheff, M., Nistor, I., and Palermo, D. (2016). “Tsunami vulnerability assessment of Canadian West Coast communities based on evacuation capability”, Canadian Society of Civil Engineers (CSCE) Annual conference, London, Ontario, June 1-4.

Cherniawsky, J.Y., Titov, Wang, K., V.V., and Li, J.-Y. (2007). “Numerical simulations of tsunami waves and currents for southern Vancouver Island from a Cascadia megathrust earthquake”, Pure and Applied Geophysics, 164, 465–492.

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Exp Services Inc. (2018). “Geotechnical Assessment Report: District of Tofino – Wastewater Treatment Plant, Conveyance and Residuals Solids Management System Project”, Reference No. VAN- 00242444-A0, dated October 18, 2018.

Federal Emergency Management Agency (FEMA) (2012). “Guidelines for design of structures for vertical evacuation from tsunamis”, Report No. P-646, Second Edition.

Fisheries and Oceans Canada (DFO) (2018). “Numerical modelling of a Cascadia Subduction Zone tsunami the Canadian Coast Guard base in Seal Cove, Prince Rupert, British Columbia”, Canadian Technical Report of Hydrography and Ocean Sciences 322.

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Kukita S, Shibayama T (2012) Simulation and Video Analysis of the 2011 Tohoku Tsunami in Kesennuma. Journal of Japan Society of Civil Engineers Ser. B3 (Ocean Engineering), 68(2): I_49–I_54. (in Japanese with English abstract) https://doi.org/10.2208/jscejoe.68.I_49.

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University of Ottawa (UoO) (2019). “Tsunami Evacuation Simulation for the District of Tofino, BC”, by Takabatake T., Nistor, I., and St-Germain, P., June 28 2019.

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APPENDIX A

BREAKDOWN OF ORDER-OF-MAGNITUDE CAPITAL COST ESTIMATE

Chesterman Beach Tsunami Vertical Evacuation Scoping Study 1 Final Report Client: Distric of Tofino COST ESTIMATING Project: No. 3004264 Chesterman Beach Scoping Study Subject: Rev.: Prepared by: PSG Date: 21‐Aug‐19 Capital cost estimate for TVE Structure according to Square Life-saving Tower Concept 02 Checked by: RAS Date: 15‐Aug‐19

Cost Estimate Item Description of Item/Comments Qty Units Unit Rate Component Total Total 1 MOBILIZATION / DEMOBILIZATION $ 20,000 1 Contractor Mob/demob Assumed 1 LS$ 20,000 $ 20,000 2 SITE PREPARATION $ 177,625 1 Tree Clearing and ground leveling 1 LS$ 20,000 $ 20,000 2 Growing medium for grass Assuming entire lot is to be grass area except under TVE structure. 915 m3 $ 75 $ 68,625 3 Hydro seed 6,100 m2 $ 5 $ 30,500 4 Paved level area under structure Cast in place concrete 650 m2 $ 90 $ 58,500 3 ACCESS PATH $ 35,000 1 Asphalt with concrete edge Includes base course. 250 m2 $ 80 $ 20,000 2 Emergency Signage 1 LS$ 15,000 $ 15,000 4 STRUCTURE ABOVE GROUND $ 1,769,728 1 Square floor columns Height measured from floor level to bottom edge of column capital 29 m3 $ 1,500 $ 42,768 2 Circular columns on ground 141 m3 $ 1,500 $ 212,227 3 Slab and beam system Including column capitals 732 m3 $ 1,500 $ 1,098,408 4 Central core 278 m3 $ 1,500 $ 416,325 5 FOUNDATIONS $ 691,500 1 Steel Piles 30m embedment depth. 16 per pile$ 30,000 $ 480,000 2 Central core concret footing 7,500mm x 7,500mm and 2,500mm thick 141 m3 $ 1,500 $ 211,500 6 STAIRS AND GUARDRAILS $ 83,700 1 Stairs 9 flight$ 2,500 $ 22,500 2 Steel guardrails 408 m$ 150 $ 61,200 7 LIGHTING $ 50,000 1 Lights and electrical 1 LS$ 50,000 $ 50,000 A PROJECT COST ESTIMATE (BEFORE CONTINGENCY) $ 2,827,553 1 Cost Contingency Factor excluding foundations 50% contingency allowance $ 1,068,027 2 Cost Contingency Factor for Foundations 100% contingency allowance $ 691,500 TOTAL COST ESTIMATE (inc. CONTINGENCY) $ 4,587,080

NHC - 3004264 - Order of Magnitude Cost Estimate - R2.xlsx 1 Cost Estimate