Not A Lot Of People Know That:
Whilst the likelihood of a major flood at any single location may be once every fifty years or so, if there are, say, ten potential locations, one of these would flood on average every five years. […] Remember this when you so often read about claims of “100 Year Events”.
Math is hard. Let’s go protesting!
An engineer friend who worked building offshore drilling rigs once told me that they designed them to be able to withstand a “100-year wave.” Then, he said, we tow them out into the Atlantic, and they get hit by six such waves the first week!
That is some pretty spurious logic. If ten sites along the same floodplain or river all have a 50 yr flood level it is essentially impossible that one could flood every five years and now of the others would not flood for fifty. A rising tide lifts all boats…
That said, the fifty year estimate is an average. So it is entirely possible that there could be flooding 2 or three times in fifty and then go a hundred years with no flooding.
And that said all of these estimates – particularly in western North America have almost no historical record to work with – it is really just an educated guess.
Winning the lottery is a one in a million probability.
Someone won the lottery last week.
That’s because of climate change, fracking and infringement of gay rights.
Calgary again has some flood water, so it should be time for Alison Redford to send in the RCMP and confiscate citizen’s private property for “safe keeping”. Well some “private property” not everything of course.
http://www.cbc.ca/news/canada/calgary/flooded-roads-reported-as-big-melt-hits-calgary-1.2565919
Yeah well, it seems, we now take fer granted thet Redford was behind the barnburners’ door-kickin’…..but like 100 year events estimates, such as flooding….jus’ “educated guess”…. we’re probably correct.
Yes, and I hear they are releasing the film “NOAH” this year as well.
Sounds very apocalyptic and all…
http://www.noahmovie.com/videos
And that calls for a song:
http://www.youtube.com/watch?v=PSZxmZmBfnU
Somewhere Over the Rainbow
Cheers
Hans Rupprecht, Commander in Chief
1st Saint Nicolaas Army
Army Group “True North”
When we (civil engineers and hydrologists) speak of a “100 year X, or a 1 in 100 year event, what we’re talking about is the return period.
Take the floods on the Bow, Highwood and Kananaskis River Systems in 2013 for example. The amount of rainfall in catchments of Exshaw, Cougar and Carrot Creek were 1:100 year storms, which resulted in a 1:100 year flood as the even happened at typical flood time, with typical upstream snowpack contributing to flowrate.
The same storm held above Highwood Pass for longer than it did the Bow Valley. As a result of the lingering of the storm, as well as the above average snow pack contributed to the same “100 Year Storm” delivering a 1:460 year flood.
The upper Kananaskis Valley (at the Lakes) got very little precipitation (like “Storm of the Year” precip) but downstream the River flooded badly.
Every point in every watershed can have a return period flood forecasted. Using Water Survey of Canada data, flow measurements, geology, geometry and statistics we can create a Synthetic Hydrograph; and like anything statistics based, the model is only as good as the data.
The key is to understand that each watershed (and each point within each watershed) has its own 1:100 year flow rate. The same way that a 1:100 year snow event would be different in Revelstoke and Miami.
Hans >
Heck if Alison Redfraud was around in the time of Noah, she’d have tried to silently slip onto the boat and strangle the little baby animals with her bare hands.
May she did try?
I’m just a naïve math major, I though the discussion was about statistics.
Thanks jon, that’s an excellent summary which dispels a lot of the media generated misinformation propaganda.
ZEP!
When the levee breaks we’ll have no place to go
Imagine if you lived in a place called Delta. And you just sort of wondered how all the dirt and gravel go there
FEDERAL FORCE is the RCMP Knight, the incessant ranting about your wet dream is pointless. See what happened today, or are you blinded by such hatred to see the news. Who payed for your girl Slow White to go and speak at the last blowfest she squalled at, and did she take any of her dwarfs that are all named Dopey.
That just blew any shred of credibility you might have retained. Stop cowardly hiding behind your keyboard and go insult someone like that at your local pub and get a much needed lesson in civility.
Such ad hominem attacks are a trademark of those who can’t grasp the subject at hand.