the impact of cubic feet per second on the river's velocity will be dependent on the cross sectional area of the particular river. 2500 cu ft per second in the Mississippi isn't very fast compared to 2500 cu ft per second going through a small stream that might have a 1 sq ft cross sectional area.

example, if river A has a rectangular cross section of 250 ft wide by 10 ft deep, that means the water will flow at an average velocity of 1 ft per second at 2500 cu ft per sec

If the river is 25 feet wide by 4 feet deep, the velocity will be 25 feet per s.

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Got it, so in other words, without knowing the specifics of the river's width and depth, CFS is kind of a worthless metric on it's own? I sort of figured as much. I'm used to seeing knots as a metric, which I sort of have a feel for. This CFS was new to me.

From Google maps, looks like this one is about 40-50m wide (so call it 140 feet) and apparently is only 4-7 feet deep (so maybe we call it 5.5 ft), so that's a cross sectional area of 770. So if it's 500 CFS that's flowing at ~1.5 fps. So if I normally swim at ~300 feet in 90 sec (1:30/100), call it 3.3 ft per sec. I'm sure some advanced hydrodynamics come into play from here, but sounds like 1.5 fps will be a pretty strong current, slowing me to 1.8 fps or ~2:45/100m but speed me up to just above 1:00/100m downstream?

Do I swim hard like a beast upstream (maybe 9/10 effort, pace it like a 750m sprint) and then just cruise maybe 6/10 effort downstream to recovery for the bike? Will my efforts be rewarded swimming hard downstream?

There is talk of even cutting the swim in half to be down steam only, at which point I wonder if there is any sense wearing a wetsuit for a ~8 min 65 degree swim.

Is this Monte Rio? Sounds like it.

The Russian River is fairly wide, especially where this race is held. I've raced the past 4 years and the current has been a little different each time. I'm anxious that they'll modify the swim, I really hope they don't. We're about the same speed in the water and I plan to push my pace the whole swim (in the sprint), not changing depending on the direction of current.

In my experience in this venue, you don't 'gain back' the time lost in the 'uphill' during the 'downhill' - but maybe that's just me.

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KJ
Swim and Triathlon Coach
AllTerrainEndurance.com
KJ@allterrainendurance.com

Based on your estimated numbers, it's actually 0.65 f/s. [500 fff/s / 770 ff]

I think your approach to swim strong into the current and cruise down-current sounds reasonable since it gives you built-in recovery. Body position and technique will be far more important into a current too, and it will be when you're fresh.

Ripple: Nice "catch" on my math. As you can see, I'd make a poor physicist. A 0.65 f/s (~20%) difference sounds much less problematic and more in line with other river races I've done like Chatty, Louisville, etc. where the upstream bit was just a vigorous warm-up.

Swim13: Yes, I'm talking about Monte Rio! I also hope they don't shorten (let alone cancel!) the swim. The longer the swim the better in my mind. Helps spread things out along the bike course. Good luck this weekend!

Nice - agreed that the longer the better on the swim! Good luck to you, too!

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KJ
Swim and Triathlon Coach
AllTerrainEndurance.com
KJ@allterrainendurance.com

I am a pretty slow swimmer, so this might not be a big deal for the faster people.

I have a little experience in a river with a noticeable flow. The biggest hurdle I always found, was the mental issue of feeling like you aren’t moving while going up river. If you can get a practice swim in there ahead of time that might be a good idea to feel that if you never have. There were times where I feel like I was seeing the same dam tree out of the corner of my eye for like 5 minutes.

One of the higher flow days at our local river swim took me 18 minutes for the upriver stretch, then only 5 to get back down. It was about 500meters each way.

Several weird things you do different in an up/down river swim. Yes, you should swim harder going out, but it is imperative that you swim on someones feet. The draft affect is huge going up river, think about on the bike, headwind vs tailwind, and how much easier it is behind someone in a headwind. You can draft guys you never would be near otherwise, so take advantage. Remember Norman at his first Kona win, the only time he ever swam in the lead group, because of a side/head current most the way. It shut down all the great swimmers, and created this huge, round pack, one that a woman eventually lead because no one could get away..

So with that in mind, swim as close to shore as you can on the way out, and closest to the center on the way back. It is ok to bury yourself to stay on someones feet, think of it as the whole swim, because when you turn around, it will be like soft peddling. You will be able to swim with swimmers a lot better than you, so make sure you are with guys like that at the turn.

AWESOME! This is great Monty. Really appreciate this advice! I'm going to be Facebook stalking the guys who had the fastest swim times last year (and hang on for dear life). I know I could keep up with them if I completely buried myself for 750m, but with the draft effect you described and a chance to take a breather on the way back downriver, maybe it will work.

One follow-up though, is the draft effect equally important at higher "speeds" on the way back downriver (water resistance increases at speed?), or is it less important, since it's like a tailwind (to use your cycling analogy)? Just trying to figure out if I can let the fast feet go ahead after the turnaround....

Will be a fun new challenge as long as they don't shorten the course!

Yes, you can let the feet go after turning around. I was astonished at how little time difference there is from an off the front swimmer to like a 3rd pack one. There is little draft affect in a good current, like running on a flat escalator. One swim I did in Germany was all downstream, I came out just a couple seconds behind a guy that would beat me by over a minute in a 1k swim, and guys that I would beat by over a minute were right behind me. Wouldn't have believed it if I hadn't actually been in it and seen it for myself..

Well -- just wanted to follow-up and close the loop on my post, in the event others find themselves in a similar position. I majorly sucked ass in my swim yesterday, but there were some good lessons for next time. I was pissed at the start, but in retrospect, it's the first time ever I was glad they shortened the Olympic course to 750m.

1) Monty's advice to stay near the shore was spot on. I was running late and rush, so ended up lined up in the middle of the river right when the gun went off, and the current was ridiculous. Talking to some folks after the race, the guys near the short were just treading water at the start. I was literally doing a moderately paced breaststroke to stay in place. FAIL!
2) Monty's advice about the importance of drafting is also spot on. The drafting effect swimming up a strongish current is dramatically magnified.
3) If you're planning to sprint hard to stay on the feet of the top swimmers, do a VERY thorough warm-up with some sprint accelerations. I was late getting out of the house and didn't have time to do my normal warm-up (and just did a mere 1-2 min of light swimming). I gunned it hard, and imploded. More on that below.
4) Do NOT line up at the front. Line up a couple swimmers deep. Being a strongish swimmer (~22min 1500m), I lined up at the front hoping to find with a plan of looking around after a few strong strokes, swimmer over to faster feet and hanging on for dear life. This plan massively failed for two reasons
4a) You need to line up directly behind whomever you plan to be drafting. In a strong current, you are NOT going to be able to swim diagonally and close the gap to catch up to a swimmer who is stronger than you. It's just impossible. I tried, and completely red-lined, making no progress. And instead, I was the guy basically "soloing" off the front like a schmuck.
4b) You will get TRAMPLED as soon as you slow down if you line up at the front. Once I realized I was not going to catch up to the lead guy and was going at an unsustainable pace, I backed off to my usual race effort. But as soon as I did that, the swimmers behind me (who were benefiting from a massive draft) all caught up to me and started swimming over top of me.

My panic attack story: I'm a bit ashamed to admit, at this point I had my first ever panic attack in the water and it was among the scariest moments I've ever had in sports. I had been swimming MAX effort on no warm up, was starting to feel short of breath, took a hard hit to the face and swallowed a bunch of water. Starting to panic, a I started to breast stroke to the closest buoy, but 1) was getting pushed basically in reverse, and 2) started getting even more trampled. That's when I panicked. Short of breath, going in reverse, no safety crew nearby, wet-suit suddenly feeling like it was suffocating me.... I've been reading all these SlowTwitch threads about people dying in swims. Am I going to die I suddenly wondered? I don't know how, but I pulled myself mentally together (edit: I remember now, I pictured my son smiling and laughing and it gave me a second wind), and dug deep to swim diagonally across the field to get to a buoy and hung on for a minute or so to rest, catch my breath, and get my head on right. Look at my HR data, my HR was 172. Nuts. A life guard called out to make sure I was ok. I said yes. I waited until my heart rate and breathing felt normal, and found a nice little pack I though I could draft. I hopped in behind them and swam at a steady pace (it was NIGHT AND DAY behind them vs at the front). I moved a bit too far back to the center of the river taking full advantage of the current (the way back felt like I was surfing) and overshot the exit, but was grateful to finish the swim.

Rest of the day went okay. Biked very conservatively a little shaken. Run was solid at least. Gave my son a big hug when I got home. Lots learned for next time.

At IMLOU (2016) I was close to shore against the current (not really a choice as that part was narrow). But when with the current I swam out towards the middle of the river where the current is slightly higher. I looked at the Strava "Fly by" and it shows I passed a ton of people when swimming with the current.