We live in an era where our critical infrastructure is at risk of failing us.

The below-ground infrastructure that has served us for the last five decades is at risk of failure due to change in climate, challenges with our understanding of how it should have been designed, intensification of the urban landscape and the simple lack of focus in maintenance, funding and knowledge.

Let’s face it, water engineering is not sexy. The lowly civil engineer has the hardest job in the world, working with technologies and theory that have not changed much or significantly in decades, if not 100 years.

But now they have to cope with new and emerging objectives such as climate change resiliency issues, aging infrastructure in the face of cutbacks to infrastructure repairs, a poorly funded utility, and professionals and policymakers who just don’t get it.

To be bluntly honest, the majority of the population thinks about our underground infrastructure exactly twice: when it is going into the ground and years later when it fails.

When our water infrastructure fails, we all pay for it with our tax dollars that fund system repairs. And that cost is not cheap. The cost of repairing water infrastructure with its attendant and consequential damage to buildings and other infrastructure is on the rise in Canada and North America in general.

While we blame it on climate change, that is not fair. We can’t design the weather, but we can design for it. We are the ones tasked with developing resilient infrastructure, not Mother Nature.

One of the most significant climate change impacts we have observed is the extremes in weather patterns — more rain, more snow, more cold and more intense heat. Designing buildings and infrastructure for this takes a different way and a questioning of the methods we applied in the past.

It means new parameters in the codes we use, driven by new objectives, new data and new ways of thinking. It will drive new standards, and being humans, innovative ways of doing things. We are the inventors of our own environments.

While we are doing that, wiping the urban landscape clean to start afresh is impossible. We live on layers of older infrastructure and often depend on these crumbling institutions for our very health and safety.

Respecting the old while building anew is the key to success. This will take some thinking, and it brings us to the topic at hand — stormwater management.

In recent years, we have seen some spectacular flooding of our urban centers as they struggle to cater to near record rainfalls, where the system was overwhelmed enough to almost cause loss of life. Yes — a near miss on lives, not just insurable property, but near misses on people drowning.

So we have begun to look at the whys and hows, and more importantly, what this means to urban stormwater management and urban flood risk. Almost losing lives has a way of escalating the attention of policymakers.

 

Risk evaluation

But what can we do? The first thing is to quantify the risk before we look to enable measures to manage.

One of the critical stormwater management tools seems to be missing from most urban planning systems: just how much water is going into the system in those intense rainstorms? The mathematics would dictate that concreted urban landscape would allow all the storm’s intense rain to the go to the storm sewers, and those sewers would be sized and in a condition to safely receive that water.

Maybe that was true when the neighborhood was originally designed. But where there was once parking lots and parkland is now intensified high-rise developments, often in a space where the sewers are combined sanitary and storm.

The underground infrastructure of our downtown cores was not designed for this sort of use. Let me explain.

When it was 100 people living in a square kilometer, the system was designed with greenspace to sequester that rain. Plus, the low intensity meant less “stuff” that could bung up the sewers was present. In contrast, put 2,000 people in that same geography and space and that means more people flushing the toilets and taking showers, more fats, oils and grease getting into the sewer and now more rain getting to the sewer faster after the precipitation event.

The results are obvious: flooding, sewer backups and more risk of roofs collapsing and overall damage.

This carnage could have been prevented if there was a way to size our sewers based on the expected maximum flows during these times, correlated to the future use of the space vis-a-vis knowledge and thus control of stormwater flow during these events.

Traditional roof drainage systems use gravity and air to get water off the roof. To get more water off the roof faster means bigger pipes. But the actual flow rates out of these roof drains were never a requirement. We always thought we were oversizing the sewers anyway. Originally, we probably were, but we are not talking about then, we are now thinking of future-proofing infrastructure before we get caught.

This is the story of siphonic drainage systems and the ASPE 45 standards. Siphonic roof drainage systems have been around for the last four decades and have been adopted into codes only relatively recently in the U.S., and not yet in Canada.

Normally a relatively new standard, coupled with a slow codes cycle, would not be a problem. But this is now a pressing problem of not knowing the flowrate off the roof to the storm or combined sewer system.

Here is a bit of theory. If you know the flowrate coming down a downspout, or a group of downspouts on a street, in a perfect world you could size the pipe. Now if the “pipe” predated the infrastructure, then we could dictate what we “wanted” the flowrate to be to maintain — and not fail — the system. This is flow control theory at its best.

Siphonic systems do just that. By eliminating the air and promoting laminar flow, you can design the flow rates and velocities desirable to what our storm systems need.

Added to that, urban flood assessors can now more accurately predict just where their hotspots are for more in-depth strategies for storm-water retention, regional sequestering strategies, opportunities for onsite water capture, retention and control to prevent flooding and its attendant carnage.

Building this resiliency into our ways of thinking is new to the codes, urban planning and design engineering.

What are we doing in codes? First of all, what we are doing may not be fast enough. We need definitions developed to manage energy use, climate change, disaster management and infrastructure resilience. Without those, we can’t build objectives that drive codes development for buildings, and policy directives for the policymakers. Only after that can we drive toward building code changes that will make us safer in these changing times.

We can’t engineer the weather, but we can engineer systems to face it. We have done it from the dawn of time. We have just gotten lazy; our caveman days were a lot more innovative.