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Construction Corner: Engineers need to include climate change into design standards

Korky Koroluk
Construction Corner: Engineers need to include climate change into design standards

When the Organisation for Economic Co-operation and Development (OECD) issued its environmental performance report for Canada recently, it devoted an entire chapter to urban wastewater management.

Included in the chapter was a section on how that management is affected by a warming climate.

It mentioned the frequency and severity of storms was increasing all across the country, and cited Newfoundland and Labrador, which, from 1900 to 1990 was hit by about six hurricanes and tropical storms per decade. But between 1990 and 2015, the ratio has more than doubled and the storm season has been extended from July and August to as late as October.

The report notes extreme storms with storm surges, overland and coastal flooding, affect many things, including infrastructure planning and water management.

Precipitation is projected to increase in most parts of Canada with the biggest increase, up to 40 to 50 per cent, in the north.

The report says adaptation to climate change has been slow across the country and adds only 16 per cent of municipalities have formally factored climate change adaptation into decision-making practices for wastewater.

The Ontario Infrastructure Plan came along too late to be included in the OECD report. But when it arrived late last year, it too included a section about climate change and the strain it is putting on the province’s infrastructure. It also included a commitment to transform the province into a low-carbon economy.

That set me to digging through my files and I unearthed an article from Carnegie Mellon University in Pittsburgh. It was about how to make climate models simple when planning infrastructure projects.

For many years, it says, climate change has been a looming threat on the minds of infrastructure engineers. But recently, with hurricanes, tornadoes, floods and wildfires in the news week after week, the threat of a changing climate has become much more apparent to the general public.

For example, we’ve just learned that the U.S. set a new record last year, suffering losses from weather disasters of US$306 billion. The previous record was US$215 billion, set in 2005.

As the world warms, the number of climate disasters will continue to rise, the article says, and our civil infrastructure will become more and more overloaded. There is an urgent need for engineers to incorporate climate change information into their design standards. But that’s easier said than done.

There are climate models, of course, but there are many. The problem, says Costa Samaras, of Carnegie Mellon, “lies in how to use the output from many different climate models.”

“Most agree on the direction of temperature change, but trend and magnitude of precipitation varies by location, leading to uncertainty on exactly how much rain to expect. This makes models and data on climate change hard to apply to infrastructure design, which requires very specific and concrete instructions,” says Samaras.

Climate models can provide information about a broad area, but not about specific locations. That’s why they can project changes across the Prairie provinces and adjacent American states, for example, but not about specific cities or districts.

So, the answer Samaras and his team came up is called “precipitation frequency curves.”

It’s a five-step framework to guide the revision of design standards through the use of publically available climate model outputs of future precipitation. That will help engineers define the relevant aspects of existing standards that need to be updated, then select the relevant climate data to make appropriate updates to the standards.

So far, the team has tested the new model by applying it to a common input of stormwater infrastructure design, what they call depth-duration-frequency curves. The curves and their application will be able to determine the performance and resilience of stormwater infrastructure during future extreme events.

Their paper has been published in the Journal of Infrastructure Systems (2017).

It can be downloaded for US$30 here.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com.

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