In recent years, earthquakes have resulted in millions of casualties around the world (Clague, 2002). Many of these losses may have been prevented if efficient evacuation routes from dangerous zones had been identified. In Canada, the areas of highest risk to earthquakes are situated along the Pacific Ring of Fire on the west coast of British Columbia, specifically the Greater Vancouver Regional District (GVRD) in southwestern British Columbia.
The risks associated with a major earthquake near the GVRD are a combination of both physical geographic hazards and societal vulnerability (Wisner et al., 2004). Physical geographic hazards are the physically damaging events which directly result from the natural disaster and are capable of amplifying the damage ensued (Burton et al., 1972). As the definition of vulnerability varies throughout literature, this study will define the term “vulnerability” as the level of exposure to hazards produced by a catastrophic earthquake that society is susceptible to (Wisner et al., 2004). As such, these associated risks are expected to intensify within the highly hazard-prone areas as the human population continues to grow in the GVRD (Office of the Auditor General of British Columbia [OAGBC], 2014).
As several studies have suggested, a Cascadian earthquake of significant magnitude off the coast of BC is due and its occurrence would result in tremendous loss as a result of primary and secondary effects (Roger, 1998; Clague, 2002). Primary earthquake effects occur as a direct result of the ground shaking, such as building collapse, whereas secondary earthquake effects occur as a direct result of primary earthquake effects, such as soil liquefaction, landslides, tsunamis and land level change (Roger, 1992; Clague, 2002; Rabinovich & Stephenson, 2004; Adams et al., 2010). These numerous post-earthquake effects must be considered when determining vulnerability potential and risk ensued. Furthermore, the estimated economic losses from physical damage and more importantly, the potential value of lost lives, accentuates the need to prioritize evacuation route planning in emergency management to ensure the safety of as many people as possible.
The auditor general of BC (2014) concluded that “Emergency Management BC (EMBC) cannot demonstrate that it is adequately prepared to manage the effects of a catastrophic earthquake”. This highlights the province’s insufficient emergency plans for a future high-magnitude earthquake. With historical evidence demonstrating that ten 6-7 magnitude earthquakes occurred within 250 km of Vancouver during the last 130 years, and that a record breaking magnitude 9 earthquake is due, the statistics alone should prompt concern about public safety and emergency preparedness for earthquake risk in the region through early mitigation and prevention (Clague, 2002). Government officials have stated that catastrophic earthquake preparedness is a priority in the EMBC, yet they have not clearly identified the temporal scale and have failed to define the level of preparedness they are committed to (OAGBC, 2014). This gap in long-term emergency planning demonstrates the need for management tools that can improve BC’s ability to manage future large-scale disasters.
A Geographic Information System (GIS) is a tool that can be used to spatially overlay and evaluate location-based information. For the purpose of this study, GIS will aid in the determination and spatial display of natural hazard risk zones, populations at risk, and the resulting potential evacuation routes, to better direct emergency management planning efforts. In an emergency situation such as this pending Cascadian earthquake, evacuation is limited by the capacity and accessibility of the existing road network, which determines evacuation potential (Pal et al., 2003). GIS techniques can be applied to evaluate current options overlaid with calculated risk to model optimal evacuation routes. This necessitates the need for GIS models to be developed and maintained in advance of a natural disaster to determine optimal evacuation routes, given physical hazard predictions, to best evacuate at-risk populations within a user defined spatial boundary.
Carpino et al. (2015) developed a GIS model illustrating the spatial extent of the physical and socioeconomic risks of earthquakes and tsunamis, and the consequential impacts in downtown Vancouver, British Columbia. The model was based on predictions of a magnitude 8-9 earthquake in the Pacific Northwest by Clague (2002) and other studies. Carpino et al. identified areas at highest risk to earthquake and tsunami hazard by considering physical factors such as surficial geology, elevation, slope and land-use/land-cover. They identified the consequence of infrastructure damage by considering socioeconomic factors such as land-use/land-cover and population statistics. Environmental hazards and socio-economic vulnerability were then combined using a Multi-Criteria Evaluation (MCE) technique to produce a spatial output identifying zones of low to high vulnerability within Vancouver.
While the approach of Carpino et al. resulted in a model identifying areas of risk displayed spatially, its applications beyond use as a reference tool are limited. This study, on the other hand, aims to partially build on the previous model by using MCE to produce physical hazard and population vulnerability models, and then overlaying these to determine the areas at highest risk of the secondary effects of a catastrophic earthquake. The model output is cost-weighted, in combination with road network data, and using Least-Cost Pathway Analysis (LCPA) a model identifying the safest/most efficient routes away from the aforementioned high-risk zones is produced.
This analysis and resulting model is more useful in its application as it not only identifies the areas at highest risk, but also where and how best to evacuate out of the determined high-risk zones. In addition, for comparisons sake, our study is based on the scenario of an earthquake occurring at 2 p.m. in January, following the scenario described in the BC Earthquake Immediate Response Plan (2015). This allows for better comparison and application of our model with that of the work done by Emergency Management BC (EMBC).
Purpose of Research
The purpose of this research is to identify safe and efficient earthquake evacuation routes away from high-risk zones within the GVRD using a geographic information system.
1. To define the physical geographic and vulnerability risk factors associated with secondary effects of a high-magnitude earthquake in the GVRD. Then, to define the variables incorporated in the cost surface and LCPA to identify optimal evacuation routes.
2. To identify zones of extreme to low physical geographic and vulnerability risk by creating two separate MCE risk models.
3. To run multiple LCPAs and identify optimal evacuation routes from determined high-risk areas following major roads leading out of the GVRD.
4. To apply the evacuation model to a scenario outlined by the BC emergency response plan and evaluate its strengths and weaknesses.