Judging swell height while at sea

While I was on a recent paddle down the coast several folks were wondering as to the height of the swell. The prediction for the day was 4-5ft at 10 seconds, or there about. Of course everyone attempts to estimate swell and wind wave size while they're out there. Usually, not always but usually, people are wildly off in their estimates.

When I was doing a BCU 3* assessment a couple years ago we were at the further edge of conditions that we could have been assessed in and the coaches asked everyone how big the waves we had just been in were. 2 to 3 foot was the common response. It was actually like 1 to 1.5 feet. On the trip down the coast some folks were throwing out numbers like 8 feet, as big as a house, and stuff like that. There was talk about the swell being influenced by the bottom and so jacking up a bit.

Anyway, despite the fact that there are approximately 1.83 million web pages that talk about wave dynamics, I figured I'd take a few minutes and come at the subject from the perspective of a sea paddler. Fair warning, there is some math ahead.

There's a book called Waves and Beaches by Willard Bascom. Even though it's quite old (mine is from 1964) there is a huge amount of profoundly useful information in it. One subject it discusses is when a wave is influenced by the bottom. Waves that are influenced by the bottom are called shallow water waves. Shallow water waves are defined those that moving through water that has a depth of:

\begin{equation}.5 L\end{equation}

where L is the wavelength of the wave. The wavelength of the wave can be approximated by

\begin{equation}\frac{g}{2\pi}T^2 = 5.12\times T^2\end{equation}

where T is the period of the wave. Note please this formula is for a perfect sine wave. There are far more accurate formulas that take into account the height of the wave and so forth. But I think for this discussion the approximation is sufficiently accurate.
I didn't actually measure it while I was out there, but the prediction was for a period of 10 seconds. If we plug that in to the equation above we get

\begin{equation}5.12\times10^2=5.12\times100=512\end{equation}

From the definition of a shallow wave water above we get

\begin{equation}.5\times512=256\end{equation}

So if we were in less than 256 feet of water then the wave would be influenced by the bottom and, in fact, we were in far less than 256 feet of water. Absent this fact then we would have a deep water wave which could not have real cause, generally, to deviate far from the predicted values. Which get's us to the real heart of the matter.

We now have to calculate what I'll call the jack up factor. The jack up factor is basically the factor one can apply to the predicted swell height so as to arrive at the swell height at a specific location. There are actually 2 components to the jack up factor. The first is the HS component.

The HS component ranges from 0 to 2 with a nominal value of 1. The value for the HS factor is proportional to the degree of surprise one felt when the swell jacked up. Typically, though not always, the value of HS is directly proportional to the volume of the exclamation "holy shit" that frequently accompanies someone turning around and seeing an unexpectedly large wave behind them. Note that it is not the wording of the exclamation (e.g. "oh boy", "oh no", "lookit that" are all acceptable) but the volume that is significant here. One thing that can influence the value of HS is the audience to which the swell height estimate is being presented. For example an audience of well experienced paddlers that one wishes to impress might cause one to reasonably reduce the value of HS substantially.

The next component of the jack up factor is the BS component. The BS component ranges has a range from 1-5 with a nominal value of 5. The specific value of the BS component is influenced by many things. The naïveté of the audience of the estimate has a large influence on the value as can, for male estimators, the maximum attractiveness of the set of females present in the audience of the estimate. It is also the case that the BS component value is inversely proportional to the estimators self esteem.

Given all of this we can see then that given the prediction of 4-5 feet at 10 seconds in the depth of water we were in fact in (47 feet or so) there is basis for a reasonable estimate of swell height outside of the rather boring prediction of expert agencies and their frequently mis-calibrated buoys. Specifically we can say that the swell ranged from

\begin{equation}[4\times HS\times BS, 5\times HS\times BS]
=
[4\times 0 \times 1, 5\times 2 \times 5]
=
[0, 50]
\end{equation}

That is, the swell was from 0 to 50 feet that day at a specific place along the route taken.

Swell estimation, as I think has been made clear, is not easy. One cannot rely on data from buoys that were located, in many cases, miles away from where one actually experienced the swells to be estimated. Rather it is the application of scientific formulas, as above, that provides the basis for understanding and, far more importantly, the describing of the conditions one paddles in.

I hope this brief treatment of such a complex subject proves useful for both those who estimate swell height and for those who must consider the accuracy of swell height descriptions one may be subject to at the bar following a paddle.

Our harsh winter environs

Living in central California has some pretty serious drawbacks. It's incredibly crowded for one. Housing is ridiculously expensive. Road rage is something you at least come to understand if not fight against. One thing that helps make up for some of that is the weather. This past weekend I joined a few fellow club members and braved the elements in an attempt to paddle from Moss Landing down to the beach behind Monterey Bay Kayaks which is aptly located in Monterey.

This paddle is something of a right of passage I guess. The coast along the entire route is pretty much sandy beach backed by dunes so, scenically speaking, it's pretty monotonous. On a direct route it's about a 14 mile paddle, and the point of the thing is to do the thing in a single go. No stopping. Not that you always could. The beach is steep for much of that part of the coast and therefore can be pretty dumpy. So depending on conditions and skills stopping may not be feasible anyway.

I'm not sure it would be possible to even invent better conditions than we had. A hazy day gave us enough sun to keep us smiling and not enough to roast us. Winds were all of 5kts and we had a 5-6 foot WNW swell at about 8 seconds or so. It was...well, it was glorious. One of those I-need-to-do-this-everyday days.

One of the participants arrived about an hour late apparently due to a change of plans and a communication breakdown. As she was getting ready on shore a couple of folks jumped on the water to wait.

You can probably see why they might want to get going as soon as possible, but I decided to wait. We were going to have enough time in the boats today.

Right around the corner from were we put in there's a dock that pretty routinely gets taken over by gobs of California sea lions. If you look closely you can see that there are so many sea lions hauled out on the dock that it's rather sinking.

Some years ago, and I forget when, these guys became a real nuisance in Monterey. Sinking boats, chasing people, stuff like that. Today though it was just a bunch of that noisy sea lion back and forth that sounds something like a holiday dinner when the entire family shows up.

We headed out into Monterey Bay proper and spectacular conditions.

Almost immediately after leaving the entrance to Elkhorn Slough we ran into a bunch of birds clearly excited about something that was almost certainly food. Pictures of a loose group of birds don't really do the groupiness of them justice I think, but there were a whole bunch.

Sadly I'm confident in only identifying a few kind of sea birds, but there were lots of different species represented in this bunch.

After we'd paddled for sometime we ran across another sea bird I can identify, at least in the general sense.

We were a couple of miles or so offshore and, all by himself (or herself, I can't tell) was this guy. I don't know what he was doing although if someone told me he was just enjoying a fine day on the coast I'd totally understand that.

These guys were hanging out just a little further on.

Generally there weren't any other creatures about, at least not that we could see so it was nice to happen upon these guys. It gave the place that sense of life that really makes time on the water quite out of the ordinary, at least for me.

Here's a view of our destination from about the halfway point.

Here's the shore.

And, dead center, here's where we started from.

That's more or less how the rest of the paddle was. Things in front of us got bigger, things behind us got smaller, and things to the left of us went boom with the dumping surf. After about 4 hours and a few minutes some folks get pretty motivated to get off the water. Here's two of our group who rabbited ahead and landed a little while before the rest of us.

And here, finally, is a picture of where we started from a viewed from where we ended at.

Close to the direct center of the far (far, far) shore is were the day started. We ended, as you can see, on a nice beach under a mostly blue sky. We made about 16 miles in 4 hours and 30 minutes. It was a long time to be sitting in the boat and I was, truth be told, pretty happy to get out and stretch my legs.

I don't know if days like this make up entirely for the crowds and cost and noise of California. It helps though. It helps quite a bit.

Fun for me. F**k for you?

A little while ago a trip report came through a mailing list I read. Paraphrasing, it contained this passage:

"One of us returned early having landed midway with shoulder problems. (I hope he got back to his car safely !!)"

I cringed when I read this. Was a paddler with a dodgy shoulder allowed to paddle back by himself? Could no provisions to assure he actually got back to his car be made? A phone call? Radio? In risk assessment land (you do do risk assessments, right?) this guy getting on the water by himself would certainly be a giant clump of yellow. Perhaps red. Now, to be fair, for all I know the injured-shoulder-guy never got back on the water. The place he was paddling is a major metropolitan area and, supposing it was not his throwing arm shoulder, from where they landed him a reasonably well thrown rock in any direction could probably have hit any one of a few thousand people or so. One of them might have given him a ride. Or perhaps his shoulder was absolutely, certainly not really that bad and he could make the couple of mile paddle back on his own with no chance of mishap. Or he caught a cab. I don't know for sure. But the circumstance does raise a question I think.

If we're in a shared experience circumstance, do we have any responsibility to our fellows in such a case as this? Suppose, for the sake of argument, the guy was going to paddle back. Is it ok to just let him go? Do we accept his assurances of capability-despite-disability, his you-go-aheads, I'll-be-fines and continue on our merry way? Or do we recognize them for what they could be; demands of social normalcy, ego maintenance, general being-stubbornisms? Do we therefore actively ensure, as far as we're able, the well being of our fellow?

I am a sucker for good animated movies. I think that The Incredibles is one of the finest movies ever made (no, really, I do). I also get quite a kick out of Lilo and Stitch. I won't spoil it for you, but it's set in Hawaii and it's about a girl, Lilo, who adopts an alien (like from space), Stitch, and hijinks ensue. It's pretty good. And, much like Lilo and Stitch, for the duration of paddles that I'm involved with, I try to ensure that I keep to the principle of Ohana. That is, nobody get's left behind.

If someone is not able to continue a paddle, for most any reason much beyond "I don't feel like it", I go back with them, make sure they are on shore and safe and usually, but not always, head back out. In the event this has proven to be entirely a pain in the ass. I don't get out as much as I want to to begin with and now I have to escort someone back because they didn't self assess well enough? Or move at glacial speeds because they didn't know they didn't have the stamina to keep up for the duration? I've actively avoided paddling with some people because I've more than once had to deal with some significant (to me) inconvenience because of them. And because of this Ohana stuff.

But, despite it all, I think Ohana is the right thing to do. I simply can't, for myself, discern any justification for not accepting a responsibility to ensure, as best as I can, that everyone I leave shore with returns safely. If we're sharing an experience well, then, we're sharing an experience. All of it. Even the awful ass parts like you have to head back early because you suck (heh). It's just not enough, I think, to say "It will be fine". I think you have to know that it's fine. For everyone. And, to be entirely clear, "returns safely" does not mean standing on shore back at the put in. It means returns to ones life in pretty much the same state you were in before you embarked on this little jaunt excepting any awesome you accrued doing cool stuff on the water.

Fun for me. Fun for you. Fun for us. Seems fair.

resolute

Go read this and come back when you're done...

Certainly I appreciate the candor as well as the (I infer) good intentions of the author. It's hard not to get behind the idea that progress in anything need require only diligent application of oneself. Indeed, baring meaningless quibbles over syntax, I would not be surprised to have found myself to have written the first three paragraphs. I find though that I am forced to take issue with much of the remaining commentary, which I have taken as a somewhat broad condemnation of continuing paddle sport education.

The fourth paragraph starts out stating that it is in an instructors best interest to get students to keep taking classes. Let me suggest that this is rather a narrow view of the issue. I would say that, to the contrary, it is in an instructors best interests to get students to stop taking classes as soon as those students are capable, comfortable and happy within the realms the student wishes to paddle. Happy paddlers are more likely to attract new paddlers and it is this that is in the ultimate best interest of instructors. I know some instructors and they, especially the best of  them, are explicitly and unquestionably interested in getting students off the books and safely on the water having the best times of their lives. And telling others about it. And them.

The fifth paragraph I interpret as a something of a broad based condemnation of the value of experience and perspective of others, specifically the experience and perspective of instructors. In particular I find myself in sharp disagreement with the assertion "...it isn't necessary." when speaking of, if I'm interpreting the text correctly, instruction. Following the logic of the position (i.e. "If you know how to do rescues in flat water (properly), then you know how to do rescues in rough water - you just need to practice") then if one can paddle in a lake one can paddle in a rock gardens, you just need to practice. I believe that is, self evidently, not the case. I will make the mistake of extending my argument into speculation by suggesting that if enough people deem kayak instruction as unnecessary it will, sooner or later, become required by those who have to go fish people out of the water.

The sixth paragraph contains actually a very interesting and, I think, valuable point. That is, "...students are expecting that the class will make them a better paddler. It won't." As someone who in fact thought that way for sometime, I quite agree. Classes, I believe, assist one in becoming a better paddler. A salient point to be sure However the following sentence, "Classes just teach you what you need to do when you go paddling" may be strictly accurate it is, I feel, well overstated, somewhat myopic in it's assertion and perhaps even a little specious. Classes can and should of course teach you what you need to do. However they should also teach you what is possible. What is to be avoided. And why. A class should help you to consider things about paddling even when you are not paddling. Provide a basis for arriving at a taste or to form an educated opinion about a circumstance that was not specifically covered in the class. Classes should help give you the tools so you can help yourself to become better.

The final paragraph, as it is clearly an expression of personal position and not an assertion about the larger world, is impossible to argue with. However I would offer one, not slight, change in wording and thus, perhaps, postion. This statement, "...I will do everything I can to make sure you don't need to take another one." might be written as "...I will do everything I can to make sure you don't take anymore than you need."

Like I said, I think the author is quite well intended and I think that I understand his perspective and position. But again, as I read it, it seems to be an overly broad condemnation of continued paddle sports education and could I think be reasonably interpreted as a broad suggestion that paddle sport instructors are cynics seeking students to "keep pumping money into the system. This, generally, has not been my experience. I have taken many classes and have learned something useful in most all of them. I have worked with many instructors and have come to consider most of them competent professionals performing a fair service for a (actually less than) fair wage without any overly mercenary intentions. I am resolute in my belief that what I've learned in those classes has materially aided me in being a better paddler, having more fun on the water and expanded my horizons with respect to understanding the possibilities open to me.

We need a maxim or something

A long time member of the club I'm in announced a trip that sounded like a lot of fun. So I went. We were supposed to meet at such and so time but the place is kind of far away and, as can happen, the organizer was a little late.

Now amongst the waiting participants was one of the most aggressive paddlers that I've met. Very type A personality, gung-ho sort of guy. Like he pulled his 16ish foot plastic boat off his car by himself ("naw, I got it, thanks"), threw it on his shoulder and ran (seriously, he ran) thirty plus yards across the sandy, sandy beach and, gently, deposited his boat at the ready. Gung-ho indeed.

So we are all on the beach organized to go, chatting kayaking chat and waiting for the organizer to catch up, he having arrived a little late as mentioned. Type A guy declares that he's going to head out, by himself mind, but he won't go around the point. It's not at all clear to me which point we're talking about but it doesn't really matter, something I tried to convey in the tone of my "Really?". You know that you-sound-serious-but-I'm-having-a-hard-time-believing-it tone. Not surprisingly  this elicits a "yah" response with not entirely subtle undertones of well-duh  (type A you'll recall) . As a last resort and with little hope I break out an "ok" smothered in this-is-not-a-good-idea. Unfazed, Type A picks up his boat and heads to the water. Sigh.

A few minutes later the trip organizer joins us and we start in on the safety talk.The beach we're on is notoriously dumpy. On this day it's really small, but perfect for a speed launch, which Type A undertakes. The salient point of a speed launch, at least for this story, is that you get your boat into the water and cowboy in as opposed to knuckling down the beach. Type A jumps on the back of his boat in a buncha feet of water, is clearly not centered and, after a brief struggle with gravity, falls in. Happens to all of us. I turn around to pay attention to the signals portion of the safety talk.

I was surprised when I glanced back out to see Type A, still in the water, pushing the bow up to empty his cockpit. The water is cold, dry suit or not, and this would not have been my choice. But, despite it all, there's no doubt Type A is a strong and experienced paddler so, like, whatever. You know? Back to the talk...destination...communication...together...

Hey, Type A, is still in the water. That was unexpected. I figured for sure...hey, he's actually swimming after his boat. His upright in 5ish knot winds boat. Umm, the boat is looking to be the easy winner of this race...oh he stopped swimming and he's on his back. Damn. I've seen this before. In a class, as a staged scenario, but still I grok this is a real situation. Neat!

I say neat because, well, it was and because I figure there's about 10 minutes before Type A is going to be even near anything like trouble. He's being blown towards-ish shore, he's dressed for immersion, he's perhaps 200 yards away, and despite admitted limitations in various other paddling skills, incident management like this is something I've done a lot of training in. Which is to say, quoting Spicoli, I can fix it. Probably needlessly I announce to the group that "he's in trouble" and grab my boat and head down to the small break intending to paddle out and, well, fix it.

In the event I didn't really have to do much. Turns out that a whole bunch of California State rescue employees of some sort were there for training or something and, while I was waiting for an opening, a Zodiac type boat comes from across the bay to help out Type A. Meanwhile one of the rescue employees, a kid, no more than 25, comes jogging over, all blonde hair and, no shit, blue eyes and asks, "do you have a leader?". This kid things we're fools and incompetents. A fair judgement given what he's seen, but I'm embarrassed and manage only a short "what?" before I see my chance and get on the water, leaving the rest of the group to deal with this kids well intentioned questions.

Type A of course was fine. The rescue guys helped him get back in his boat, he pumped it out, etc. Fine. I was a little embarrassed in front of the professionals and the conclusions I can imagine they came to. But mostly I was shaking my head. I mean, and I am not at all a fan of hyperbolic what could have happeneds, the whole thing could've put a serious crimp in my day. Just to get on the water maybe 10 minutes earlier. Which got me to thinking.

There was this really successful and famous (if you're a college sports fan) coach named John Wooden and he had a bunch of maxims. Like "be quick, but don't hurry". Catchy (says I) and actionable sayings. I think we need a catchy maxim or two when it comes to safety stuff. Like, "saving 10 minutes could cost you a lot or otherwise put a crimp in someone else's day which is terrible if they don't get out to paddle enough". You know. Catchy.

Maintenance

Cleaned my boat the other day. Washed and waxed.

I like cleaning my boat. It's just so....certain.

Planning sickness

Planning trips is something of a sickness I have. Sad to say, but the fact is that I plan way, way more trips than I actually do. Whether it's a day trip on the weekend or an overnighter somewhere along the coast it's still the case that finding time to go is always difficult. Still, plan I do.

Over the years the tools I've used for planning have varied. As little as a few years ago getting (real) charts on a computer screen was something of a pain. And getting tide and current information on the same chart was something I had a really hard time finding. These days of course there are all kinds of choices, at least in the U.S., for getting NOAA chart and Google maps mashups. The final frontier was a decent tool (set) for my smart (read "i")Phone. I have I don't know how many tide and weather apps, current apps, ship finders, and so forth. Just a bunch of disparate tools that I can potentially use to plan in quite fine detail some outing that probably won't happen. But nothing cohesive, no "one app to bind them all".

The smart/iPhone situation has changed though. I happened to spend some time with Ben Lawry while he was at the GGSKS. In addition to being a pretty damned fine coach Ben has the (I say) admirable quality of being something of a gadget geek. He has an iPad and a smart (not "i") phone and turned me on to an app from a company called Navionics. For $10.00 it has downloadable charts that auto stitch, has tide and current info on the chart, a community layer (they call it) where it looks like you can add your own icons to the chart and share them, and a entirely livable UI. You can plan and sport routes and it will create exportable tracks using the GPS.

The number of tide and current stations is a bit lacking, the charts are a little jagged edged at large scales and a little cluttered at small scales. I wouldn't want to plan a serious multiday with it and I guess Navionics wouldn't either since it has a big green "Not for Navigation" type warning when the program starts, but for those "hey, what should I do this weekend" questions, or over beer what abouts, it's totally reasonable. Hell, I thought it was worth $10 just to not play Angry Birds or whatever quite so much. Getting something I can plausibly pre-plan a trip with on my ("i")Phone is gravy.