100-Year Floods aren’t the way to think about flood plains anymore. The experts now rate them on their probability of occurring in any given year: “100-Year” is now “1%”. And really, if you look at statistics, those floods happen every decade or two instead of every century anyway. But as we all know, climate change is blowing up our old statistics, so maybe even these classifications aren’t that dependable.
Today, Kendra Smith, a Certified Floodplain Manager and director of our Willamette project, taught any staff who wanted to attend the Rivers and Floodplains Lunch ‘n Learn. We learned lots of terms like thalweg (the deepest part) and tail out (where ponds transition to riffles and salmon want to spawn.) Streams are classified by letters and numbers in the Rosgen Stream Classification, much like the Periodic Table of Elements or botany.
We also learned why the “floodway” and “flood fringe” are regulated – to protect everyone and everything all along the waterway from damaging high water. And vegetative buffer zones blunt some high water damage along the edges, protecting land further in.
The biggest takeaways for most of us were where not to buy land (within the meanders or the bankfull) and where to fish (in the deep pools above the riffles.) Kendra said she used Google maps to check out some property a relative was thinking about buying and responded immediately “No way!” Clearly, it’s handy to have someone who knows rivers advise you on real estate decisions.
