Saturday, June 29, 2013

Misunderstanding Flood Frequency and Climate Change

Apparently, some people still have problems understanding what the difference is between "climate" and "weather" - or in this case the impact of a changing climate on flooding (which is an outcome of severe weather). The high rains that hit the Calgary, Alberta region of Canada were caused by what The Weather Network described as an "atmospheric river"caused by a major meander in the Jet Stream. This sort of major meander in the Jet Stream is what caused Alaska to shatter high-temperature records, and could be linked to what is now causing a massive heat wave in much of the western US. This meandering of the Jet Stream is the reason why the UK is having such a soggy summer. And why, exactly, is the Jet Stream meandering so much? If only we had an explanation for it that makes sense of it in scientific terms. Oh, wait, we do, and it's called climate change (aka global warming).

See? Climate change is causing increased warming in higher latitudes. Warmer air in the higher latitudes means that the energy gradient compared to lower latitudes diminishes, which means that the Jet Stream meanders more. This is what the theory predicts, and this is what we actually see.

But - apparently - many people don't understand this. Many in the initial piece really wanted to bludgeon others with the contention that - since the Bow River had flooded in the past to the same magnitude (and even greater amount) - the current flooding has absolutely nothing to do with climate change. This is problematic on two fronts. The first is that the evidence of why the Bow River flooded (the "atmospheric river" caused by a major meander in the Jet Stream, which is exactly in line with what our models of climate change would predict to become more common). The second is that the justification for the argument (that we can use historic data and historic probabilities of flooding to predict the likelihood of future flooding) fly out the window when we recognize that global warming will alter the underlying processes governing flooding.

There was one particular commentator - Luke - who was more than a bit of an arrogant twit. Unfortunately, it looks like he deleted all of his comments from the page. (I'm making the assumption that he did it himself, because none of the other obviously-wrong-and-just-as-arrogant statements have not been removed.) Still, Luke's comments showed an obvious misunderstanding of flood frequency and the link between floods and global warming (outlined above). The basic contention by Luke was that the recent flooding in Calgary was nothing strange, and that - in fact - the name of the river indicates that flooding is a normal part of the river's course, citing this story, and specifically this passage:
The Bow River gets its name from the Peigan name “Makhabn” which means the “river where the bow reeds grow.” And a good place for reeds to grow is a flood plain.
To Luke, the fact that bow reeds grow on flood plains (and - apparently - that the term "flood plain" has the word "flood" in it) must have meant that the recent massive flooding wasn't really that big of a deal. To that contention, I wrote:
Perhaps you ought to look up what a floodplain is, and what the flooding frequency of a floodplain.

Or you can just keep believing that you aren't seeing the truth of your constructed reality being washed away. But that's your choice.

I prefer to side with reality. Call me biased in that way.
His response was to point me to another comment that he made about the size of the ten biggest floods recorded on the Bow River in Calgary. However, if you knew what a flood plain is, you would know that flood plains are not flooded only when there are historically huge floods. Indeed, flood plains are flooded far more frequently than once every 100 years or so. It's why they're called "flood plains", instead of just "plains." Indeed, I decided to even give Luke a link to an easy-to-read explanation from the USGS (yeah, I know, Calgary is in Canada, and the USGS is a US governmental agency, but the hydrology of rivers doesn't change at the border). (The portion in Courier is a blockquote from his comment, to which I was responding.)
Had you bothered to look at the table I posted below, you'd know exactly what the frequency is. But, evidently, all you've got is a big mouth.
Umm... Actually, all you're doing is showing the extent of your naivete about these issues. What you provided is the historical maximum floods. I actually did see that table. However, these incredibly large floods are not the only ones that inundate floodplains, and pointing to only this table indicates to me that you don't actually know what a flood plain is.

(To recap: Your original contention is that the name of the place - river where the bow reads grow - indicates that this is a flood plain, and that flood plains are known for ... flooding, and so what we just saw in Calgary ain't that big a deal. And then when I asked you if you actually know what the flooding rate of a flood plain is, you pointed me to a table that shows only the largest floods, which - if you know anything about flood plains - doesn't even come close to the numbers of floods that inundate a flood plain, which indicates your ignorace of what a flood plain actually is.)

Here is some reading material about what a flood plain actually is, and what the flooding frequency of a floodplain is. (I'll give you a big hint about where to find the answer: paragraph three, which begins with the words "Bank-full discharge..."

Of course, these floods are several magnitudes smaller than the one that hit the city, but the point is that you can have flood plain inundation - and therefore have a great place to grow bow reeds - with river discharge rates far below the one that you're trying to show as being no big deal.

Still, I applaud your efforts to try and understand something that either beyond your comprehension or actually operates in a way that runs counter to your presuppositions. My advice to you is to keep working at it, eventually you might come to recognize that you're wrong, which might then allow you to actually learn something correct.

Good luck!
After this point, Luke decided to cut his losses and say that I won... but without actually recognizing why his position was wrong. I really wish that I had his wording, since it's patently clear that Luke was just trying to find a way to get out of having to argue against someone who slung his arrogance back in his face, along with a ready understanding of the very facts that he was trying to use to bludgeon his opponents. Of course, his weasel-worded "concession" comment tried to have it both ways; saying that I won the debate but that he was right on the facts. However, there was a problem... A: there was no "debate", and B: the whole point of my comments were that he was wrong on the facts. (Did I mention that he was an arrogant-twit?) So, since he crowned me the victor, I felt that it was important to explain to him why his concession was actually just annoying:
Wow. Apparently you don't understand simple hydrology (or you are incapable of taking 10 minutes to read some easy-to-digest science from people who do and written for people who don't).

I'm not going to waste time even trying to explain more to you, since you have twice shown an unwillingness to actually make the slightest modicum of effort to understand why your statements are just grossly and laughably wrong.
To this, he gave the completely bizarre (and equally weasel-worded) response that amounted to, "But I said you won. Why don't you just accept that you won and move on?" And I decided not to respond further, since - as I wrote - he wasn't worth my time.

Things were left there for a day, and now, another commentator felt that I was too harsh on Luke, and insinuated that some of the positions I outlined were wrong:
Your arrogance overshadows everything you've said. The point is that the big floods in Calgary were 125 years ago when 1/100th as many buildings were on the Bow River's flood plains. So this flood was both normal, and predictable. That may not follow the climate alarm industry's script, but it is observed fact. BTW, the Bow River's floodplains mostly grow cottonwoods.
I do recognize that I'm acerbic. And I also recognize when others are being acerbic. If someone wishes to be acerbic, I'm more than happy to oblige them, but what am I supposed to do with this comment? I mean, there is nothing there that actually is written to confront or try to refute any factual piece that I wrote (other than the observation about the current plant ecology, which I didn't introduce in the first place) while simultaneously implying that none of it is valid because I wrote arrogantly to an arrogant person or to bring up points that are only tangentially related to things that I wrote and to point out that the reference to the plant ecology of the Bow River (which I didn't introduce, but was actually responding to) was incorrect. Well, I decided to spend about 30 minutes to write the following exhaustive reply to each of the points that this commentator raised (many of which I didn't discuss at all in the first place, but whatevs):
As with kindness, respect, or sincerity, I return arrogance, like for like, pound for pound, and Luke was dishing his arrogance out like there was no tomorrow. From the above, though, you'll note that neither Luke nor I really minded (or at least commented that we minded) on the heights of arrogance that we were using to talk with each other. I enter each interaction with the understanding of how - based on the evidence - the other person/people are already conducting themselves in the forum, and apply the Golden Rule: they are treating others with arrogance, which means that it is apparently how they wish to be treated. (After all, if they didn't wish to be responded to with arrogance and derision, they shouldn't have done it in the first place, right?) However, those are issues of interactive game theory and socialization, which (although an interesting topic) isn't the one covered by this article, nor by Luke.

To the substantive points you make, you are right: there are more buildings in Calgary now than there were 125 years ago, but this has nothing to do with regional flood frequency. But if I am missing some connection between flood frequency and the different number of buildings in Calgary, I would be happy for you to explain that link to me. The only major impact of building construction to flood frequency is the extent to which the land-cover changed, although landcover change creates local impacts, and the flooding wasn't only occurring within Calgary, which means that land-cover change wasn't the significant driver of this flooding event. But again, if I'm wrong on the facts here, please let me know.

As for the growth of cottonwoods vs. bow reeds, I was not making any claim about the actual biodiversity in the region, only responding to the claim by Luke that the large floods are somehow normal, because the name cites bow reeds, and bow reeds grow in floodplains, and - as evidence of flooding - Luke points only to extreme flooding events instead of a natural frequency of flood-plain inundation. Still, this doesn't change the general point of linking the comment to the flood-plain inundation rate and not the historical maximum flood rates, because although I am not a plant ecologist, the species of cottonwood I am familiar with tend to grow in/near floodplains and (especially in more arid regions) rely heavily on the periodicity of flood-plain inundation. Therefore, whether it's bow reeds of cottonwoods, it's the flood-plain inundation frequency (and not the historical maximum flood volumes and rates of flooding) that are more important in understanding those local ecosystem dynamics. (Although, to be fair, extreme floods do have a significant effect in shaping certain constraints to ecosystem structure, but the temporal scale of their impacts are at a completely different scale than the flood-plain inundation rates, which are far more important for year-to-year survival and propagation. This is the case for most flood-plain ecosystems, and I'm assuming that those in Alberta are no different in these broad-brushstrokes.)

Also, I agree with your point that the flood was predictable, and - in that sense - as normal as any large and predictable flood would be in the course of the history of a location. I am hesitant, though, to say that it's "normal," since the idea of "normal" is different when speaking about flood frequency and speaking in a day-to-day context. To most people, the idea of "normal" tends to be in the "happens regularly within a time frame that I happen to expect it to occur within (which usually extends to a maximum of "my life so far")". Therefore, while a 100-year flood, 500-year flood, or 1000-year flood occurring at some time in the history of a river system is "normal" in the grand-scheme of things, to most people, that particular event wouldn't be seen as "normal", since it didn't happen in their lifetimes (and if it did, then it wouldn't be "normal" since multi-century events "shouldn't" happen more than once in their lifetimes, even though - statistically - they could, and would be perfectly "normal" from a flood-frequency perspective).

Finally, to shift the discussion to where I infer that you're implying that I'm "follow[ing] the climate alarm industry's script", let's step away from the label-placing and automatic assumptions and speak about how climate change will affect the reliability of current flood frequency statistics. Flood frequency is based on a statistical probability based on past events, and this is fine, so long as current climate is adequately described by past climate. In general, though, climate change is expected to significantly alter flood frequencies in many places. Therefore, methodologically speaking, a future with altered climate makes using flood frequencies that were established on historic data methodologically troubling at best (and - if a region's climate has changed dramatically - it makes them completely useless).

Again, if I get anything wrong here, please do let me know. I'd be happy to have a discussion with you about them and to correct my knowledge and expectations.
I won't hold my breath to see if there's a response.

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