Infrastructure Costs of Local Downpours, Floods and Washouts

In an ongoing effort to bring together some local examples of what residents of the Ottawa region have already experienced attributable to climate change I’ve looked into heavy rain events. They are costly and data shows they are becoming more frequent.

2011 was a particularly bad year for damage to our local infrastructure due to intense downpours:

Climate experts have predicted that climate change will increase the frequency and severity of storms. Storms such as these not only do damage directly, they also tend to exacerbate things like the repeated flooding seen in Kanata and sewage spills into the Ottawa River. The combined costs of these infrastructure needs and repairs run into the tens of millions of dollars; hundreds of millions if one counts the full cost of things like the Ottawa River Action Plan.

And the evidence is already coming in that those theoretical predictions have begun to come true. The types of damage and infrastructure demands listed above are just what we should be expecting more of.

The Environment Canada graph below shows that nationally since the early 1970s the majority of springs have generally been wetter than normal.

Ottawa is on the border of what Environment Canada considers the “Great Lakes / St. Lawrence” and the “Northeastern Forest” climate regions, as seen in the image below.

In the Great Lakes / St. Lawrence region 2011 was a record spring for what climate scientists call “departures” with rain reaching 54% above expected levels based on 64 years’ worth of data.  The Northeastern Forest region was a measly 12% above expected levels.

This is shown geographically on this Environment Canada map.

These single season numbers are in line with overall local trends.

Here’s a graph showing percentage departures over those 64 years first for the Great Lakes / St. Lawrence. The spikey blue lines are hard to interpret, but the 10 year rolling average in red shows clearly that “departures” are trending to heavier rain rather than to lighter.

Great Lakes / St. Lawrence region Spring precip departures in % as at 2011

And here’s the same graph the Northeastern Forest region.

Northeast Forest region spring precip departures in % as at 2011

The above 2 graphs from data from Environment Canada.

All this Canadian data is consistent with US data for their North East region.

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One Response to Infrastructure Costs of Local Downpours, Floods and Washouts

  1. Dave Wilson says:

    Note that the scale for the Northwest Forest region graph is half that of the St. Lawrence region (10% per division instead of 20%) so the apparently similar variability is actually much more in the St. Lawrence region, another aspect of climate change.


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