Originally posted by Slackkinhard
gauge correction? I've felt like the gauge has been reading higher than it really is lately....today there seems to have been a change? I've seen it do this before, so maybe it's just me.
Ok here is the answer to your quandary. You aren't Slackin as Hard as your moniker implies- you've an
avid pressence on this forum and on the river. But, like a lot of boaters on the scene you are a relative new comer. So the nuances of detail throughout the river escape your attention, no matter how observant you may be. This is natural. Such details are quite subtle. But over time you get so familiar with your environment that you
know what you are observing.
After a few decades of observing rivers and specifically about a dozen trips down the Sky since these last 4.5 floods, I have come to know, with confidence, what I'm observing. I'll share that now...
The river bed as we know it in a general sense has a certain depth to it, as we've grown to be familiar with it in our 'lil geological blink of an eye.
So, when the sky is running 6,000 cfs for example, the picket fence has had the peaks of its rocks visible, but the spaces between them are filled in. i.e Ned's Needle, The Needle Proper, and Paul's Needle all have pretty full channels. Keep in mind that "The Bubble Pool" (proper name) located immediately upstream of the Picket Fence (Also a Proper Name) has been a very very deep pool the whole time we've known the Sky. This deep pool has provided slack water and is the saving grace for raft guides as they try to line up for the needle. This slower water has also helped many a kayaker rescue or self rescue above the Picket Fence. "The Bubble Pool" is likely filled in with some extra gravel now. That is going to effectively
Raise the Level of the River Bed.This is evident by comparing the guage reading with the waterline on boulders, such as those at the Picket Fence.
I feel like my recent runs through the standard raft entrance are kicking me through the bubble pool faster than before the recent floods, but the extent of this could be partially or entirely in my imagination. Repeated runs through at varying water levels will reveal the truth, unless that 32,000 spike last week altered things further, which it probably did. Although, this time, it probably scoured and scrubbed out a *small* amount of these recent gravel deposits.
The "Raised River Bed Due to Fresh Gravel Deposition" Theory is quite evident elsewhere throughout the run, most notably from the Confluence to the bottom of BDrop. Anderson Hole is perhaps the most striking example because there you have a relatively Simple, Flat and Wide river bed with a simple composition of just a few medium sized boulders. Flows between 3-4,000 give Anderson Hole a much more filled in look, with the boulders nearly pouring over. It looks more like 6-7,000 there, loosely speaking.
Again: wide and uniform distribution of gravel across the whole run from top to bottom, from bank to bank. (and that's a slight exageration for conceptual purposes)
My theory: Baseball to bowling ball sized gravel, an amount big enough to fill...20 dump trucks, let's guess. "Baseball to Bowling Ball size". I postulate this because that size range is small enough to easily moved around, yet big enough to stay put unlike sand and finer gravel. So when I say "gravel" I'm talking about "Cobble". You and I could unload a dump truck full in a day and move it somewhere with wheel barrels. Might not be fun, but from a logistics standpoint its doable. It's logistically doable for the river, too, except it probably enjoys moving that sh*t around. I know I would, If I was a Skykomish River
Not My Theory, Just observation: All of this came out of the North Fork. This is obvious paddling down form Index to the confluence, most notably in "Powerline" Rapid. (Not Cable Drop- that's on the S. Fork, and the power lines cross both forks duh) Powerline (I'm hearing people call it "Toothpaste", but I never heard that name before and I been around awhile. Guys, stick with or find out what the original names are- its less confusing) Anyway, Powerline (for lack of a better name) is completely different now much to the consternation of the esteemed Mr. Harms and probably Sam too since that big monster hole that used to form at high water is gone now.
The NorthFork has miles of that kind of gravel. If you've put in at or above Trout Crik you know what I'm sayin. Well now a large share of that gravel is below the confluence but above Aquagasm (Lunch Hole Proper looked consistent with my theory at 1900 cfs. Similarly, Any large amounts of gravel being pumped and rolled down the South Fork won't make it to the confluence because you got Eagle Falls, Canyon Falls and Sunset Falls to cull out those deposits. Big drops have big pools. And Otter Slide and Cable Drop can arrest any gravel that manages to get that far, not to mention the flatwater from there to the bridge.
Having a large pool above and below each rapid is obviously a very common attribute of whitewater anatomy. These pools are perfect for recieving these deposits, leaving less gravel to proceed into the next rapid.
But 32,000 is the low end of "Flooding" according to NOAA/USGS. Its wasn't severe enough or in series like the other events to bring down more gravel. No, last fall the North Fork PUKED HARD. Now the job of a 32,000 cfs event would be, I suspect, to "Tidy Up" or Sweep Away" some of that loose material that rests on top of the more firmly bedded deposition. Because that is Definitely enough water to move the gravel deposits we are talking about. So I'm sure its changed yet again, but not as dramatically.
Hope that sheds light on everyone's questions about why the guage seems off (if you're still reading it means you were interested enough). Keep in mind the gauge is in Gold Bar. While the Cross section it measures may shift and change (gravel bars down there in the glacial valley), it is still just a measurement of volume and time. 6,000 cfs is 6,000 cfs. So the Gauge isn't "Off". The River is "Off". but, The River is The River, so it can't be "Off". That means the only ones left who can be "off" are... Us.