How long would it take for an auto-based evacuation of the Halifax peninsula in the case of an emergency or disaster?

This isn’t something that’s top of mind for the average person, but Ahsan Habib has wondered about it since he first moved to Halifax in 2010. The Dalhousie University transportation professor has been actively researching evacuating the Halifax peninsula using traffic microsimulation modelling.

“When I moved to the coastal city of Halifax, I thought this is probably one thing that we should start thinking about just as an idea, but it became a project later on when we saw these extreme events happening south of the border,” Habib recalled in an interview.

“We saw hurricanes Irma, we saw Harvey, we saw Florence, the Sandy storm in New York with four-metre floods. I thought maybe this will be a good focus and we should start seeking some sort of research support and collaborating with other folks. That was in 2014.”

Working with Kevin Quigley, a professor in Dalhousie University’s school of public administration, Habib said they received funding from the Marine Environmental Observation Prediction and Response Network (MEOPAR). That was swiftly followed by federal funding from Defence Research and Development Canada to dig deeper and understand more about the intricacies around how to evacuate the Halifax peninsula.

On Sept. 25, Habib was one of several panellists who participated in a discussion that coincided with the 15th anniversary of Hurricane Juan. Titled “Sink or Swim: Decisions in Emergency Management,” it was hosted by the MacEachen Institute for Public Policy and Governance in partnership with MEOPAR.

Experts in emergency management, flood modelling and prediction, and evacuation traffic modelling took the opportunity to discuss emergency preparedness for future coastal risks and evacuation scenarios.

“There is a need of understanding the system because we are on the hurricane path no matter what. All the hurricanes that we saw in North Carolina, South Carolina that could hit us. Juan came to us,” Habib said.

“There are also other types of risk, like an explosion, for example. I know the mass evacuation scenario is a rare event, but we can learn about it not just by observing when it happens, but with these type of simulations and these hypothetical scenarios.”

A collaborator from the Nova Scotia Community College created a flood risk model to determine which Halifax roads could become flooded in a variety of scenarios. They came up with a 2.9-metre flood level scenario first, comparable to what occurred during Hurricane Juan. That was followed by 3.9-metre and 7.9-metre flooding scenarios and then the most extreme cases of 15 and then 30 metres.

“In those last most extreme cases, the Halifax peninsula becomes an island, and I have no job to do because that’s probably the navy’s job at that point,” Habib said.

The traffic model was generated using the 2.9-, 3.9- and 7.9-metre flooding scenarios. They set an assumption that the event would occur on a weekday at 10 a.m., when the Halifax peninsula has the most people residing and working in the core. The model was also based solely on an auto-evacuation of 57,000 vehicles.

The results showed that with no flooding, full public compliance and no unexpected incidents, it would take almost 11 hours to evacuate the peninsula. Add a 2.9-metre water surge and that jumps to 13 hours. With 3.9 metres of flooding, it becomes a 15-hour evacuation.

The most flood-prone roadway in Halifax, according to their data, is the Armdale roundabout. Using the 2.9-metre flooding scenario, almost 18 per cent of the roundabout becomes flooded. At 3.9 metres, that jumps to 43.5 per cent, while at 7.9 metres, it becomes 88.7 per cent flooded.

The Bedford Highway is the second-most flood-prone stretch, according to the modelling. Under the 7.9-metre scenario, 47.8 per cent of that roadway becomes flooded.

Habib said anyone who’s ever been stuck in snarled Halifax traffic knows how quickly things can bottleneck, and that’s without a flooding situation.

“We are now thinking about what could be our countermeasures? We have the traffic model and now we are using that traffic model to run alternative scenarios,” he said.

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Those alternatives include how much they can rely on transit (bus) to reduce road traffic and get more people off the peninsula during an auto-based evacuation.

“We are also trying to identify what should be the pick-up locations if we are using the buses, and how we use those bus scenarios to see how much improvement that we can do in terms of total clearance time,” Habib said.

One of his graduate students is also examining the best potential evacuation routes. Habib said that might include using Robie St. or opening up roadways to have all traffic going out of the city in both the outbound and inbound lanes.

“We are looking at whether all that actually reduces not only just the total time, but also other aspects because some areas got really, really gridlocked,” he said of the simulations.

“We can’t do much (there), so we are trying to see what intersections get more problematic … So this traffic operational kind of improvement is what another student is looking at.”

He and his students are also considering where evacuees would go in the event of a mass exodus of the Halifax peninsula.

“Where are the shelters? In our model assumption, we only have two locations, NSCC in Dartmouth and CP Allen High School in Bedford,” he said.

Habib said they’ve reached out to emergency management officials and others to get input about different potential shelter locations to include in future modelling.

“We’ll probably gain more understanding of how we can efficiently, effectively plan to evacuate,” he said.

Rather than simply being an academic curiosity, Habib said his research has the very practical application of informing potential future risk management should there ever be a scenario that requires a mass evacuation of the peninsula.

“We’ll explore how much we can actually achieve through these countermeasures … to get around the challenges with these limited number of exits (off the peninsula),” Habib said.

“It’s not to optimize how fast we can evacuate, it’s more to find some sort of a solution so we can make evacuation efficient and ensure we do not see the unforeseen problems when we have to do these things in real life.”

Yvette d’Entremont is a Halifax-based reporter focusing on health and environment. Follow her on Twitter: @ydentremont

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