Handling tide rips and general rough water

[GreggL]

First boat in the sail cruising market and am now practicing the bays and such working up my experience level. My experience is mostly with smaller powered inshore boats for waterskiing, tubing, etc.. Lately been in some rough water and I'm not so sure I'm handling these situations as best I can, very different from what I'm used to. I'm in a hunter 33 and am planning a trip through plum gut and block island sound in August, from what I hear it can get pretty nasty in there.
Advice on how to steer, etc. are greatly appreciated. Thanks!

[Astrid]

Rip currents or rip tides are caused by waves moving inshore across sand bars or reefs. The waves, not having an immediate way to move back out to sea, will tend to form a current that moves parallel to the beach. If there is a channel between the sand bars or a break in the reef, opposing currents moving along will escape through the gap at considerable velocity (sort of a venturi effect) and move back out to sea as a rip current. Your best bet is to study your charts and look for green tinted areas along the shore line or shallow. If you see gaps in the green tinted areas, that will be an indication of the possible presence of potential rip currents.

The rip current itself dissapates quickly as it moves out to sea and into deeper water. If your charts show possible rip current areas, you best bet is to stay out far enough that you avoid the major effects of the rip current itself.

[GreggL]

Thanks Astrid.
What's weird is that the plum gut rip currents I've been hearing about are said to be better when closer to shore. I wonder if that's a trait specific to that area?
Unfortunately that's my route and there will really be no way to avoid any rough water so I'm preparing for the worst.
And advice on handling in these waters would be great. Thanks!

[GordMay]

See “Crossing a Harbor Bar” ~ by John Kretschmer
➥ http://www.cruisersforum.com/forums/...html#post13606

And “Crossing the Bar” ~ by Andy Galwey
➥ Crossing The Bar - How to tackle white water bar crossings

[capn_billl]

I used to live in Oregon, some of my most frightening, (and dangerous), boating moments was trying to cross the Columbia river bar.


The bays on the Texas coast are cakewalks in comparison.

[Andrew Troup]

I think there's a possibility of the term "rip" being used here in two quite different contexts.

One (which Astrid's post refers to) is the sort of rip caused essentially by wave action, which happens at surf beaches, because of a strange thing about breaking waves.
The water in a normal wave doesn't actually go anywhere. It's like tying one end of a rope to a wall and waving the other end up and down: waves travel along the rope but the rope stays put. (Individual bits of rope actually orbit around in circles, looked at side on). Similarly the bits of water in an ordinary wave don't, over time, travel anywhere (unless there's an underlying current from some other cause)

However when waves get steep enough on the fronts for them to break forwards (which incidentally almost NEVER happens offshore) things change, because that water has escaped from the recirculating energy system of the wave, and is now tumbling, under freefall (impelled by gravity) down a steep ramp which itself is moving (not the underlying water, but the 'geometry' of the water) towards the beach.

So at a surf beach all this extra water gets transported inshore, about mean sea level, and as we know, water tends to find its own level, so it has to get back out somehow. It does so in rips.

This sort of rip is not CAUSED by tidal flows, but it does vary in intensity with the state of the tide, because the underwater trenches through which these rips are channelled are sometimes almost the only viable route, depending on how deep the water is around them. And naturally this 'landscape' varies with the state or height of the tide. So, rather confusingly, these rips sometimes get called tide rips, but really they're wave action rips.

Another sort of 'rip' is caused by a tidal current (caused by the difference in the height of tide between different adjacent bodies of water, or parts of a single such body) being intensified locally by channels and other aspects of the underwater landscape. (Such as sudden changes in depth, causing upwellings and suchlike)

This can cause strange phenomena when ocean waves are travelling in the opposite direction. On very special occasions at certain locations it's possible to get standing waves tall enough that any ordinary vessel would simply run out of thrust and momentum trying to get up them.

Standing waves are a cute inversion of what I just said about ocean waves.
In a standing wave, it's the geometry which is going nowhere, whereas the bits of water are very definitely travelling at speed (due to the tidal current). Luckily these are remarkably rare (except in white water rivers), and there's almost always another way around them, or (because they're almost always a tidal phenomenon) you just heave to and wait a few hours.


But I'm sure what's being talked about in your case is something much less daunting. Any narrow passage will have strongish rips within it (local 'streams' of strong flow, sometimes rotary eddies and even turntables - we don't talk about 'whirlpools' because it frightens suggestible children) at certain stages of the tide, and often you can cheat (if you're travelling against the flow) by hugging one shore or other, where there is often a 'back eddy' travelling in the opposite direction. Unless the maximum flow is over six knots or so (or there are tricky rocks which are not easily seen) you don't usually have to be ultra conservative, eg check fuel filters, seal all open hatches etc etc.

I hope I haven't confused the issue, but you have to at least be clear that there are two very different phenomena with the same name.

Occasionally you strike a venue where both sorts of rip are happening, and river or harbour bars are an example. Unless they're very benevolent, I think it's prudent to steer clear of them until you've had lots of experience of each phenomenon in isolation from the other.

[Dockhead]

Right. I also think that the term "rip" is being used in different ways here. What Astrid described is something which happens near the beach, and you should never be anywhere near that close to a beach in a sailboat, certainly not a cruising boat.

The other thing is more properly described as a "race", if I am understanding correctly what people are talking about. Tidal races are formed when tidal currents encounter a sudden decrease in depth, or when they go through a narrow strait -- the velocity of the current in increased, sometimes dramatically. Some of these areas can be extremely dangerous -- e.g. the infamous Portland Bill in the English Channel.

Tidal races run when the tide is running strong; they disappear at slack tide. They become most dangerous when there is an onshore wind, or wind against the tide. Wind against the tide can make the standing waves rise up into veritable walls of water -- terrifying and dangerous.

Even in benign conditions, tidal races can be tough. I crossed the race at Peveril Ledge on a calm, sunny day a couple of years ago, on neaps to boot, not expecting any trouble. Well, the waves there were square -- they had no backs. My boat was fallling off the crests with a terrible crash -- as if dropped out of a travel lift. It was quite frightening. And this was a minor race in benign conditions. That taught me some respect, I'll tell you.

The way to deal with tidal races is to carefully plan your passages, which you should be doing anyway in tidal waters. Your charts and pilot books will explain to you where they are and when they run. Cross them at slack water or sail around them. Often tidal races have a "back door" very close in shore -- Portland Bill is like that -- a cable or even less of calm water. I can tell you it is quite "exciting" to thread the needle between the raging waters of the Portland Race when it's running, and the rocky Bill. I've done it a number of times -- it saves many miles on passage West from Weymouth.

In rough weather, give tidal races a wide berth, especially if there is wind against tide.

Google "Portland Race" if you want to read a lot of real life stories.

[Dockhead]

Originally Posted by Andrew Troup

This can cause strange phenomena when ocean waves are travelling in the opposite direction. On very special occasions at certain locations it's possible to get standing waves tall enough that any ordinary vessel would simply run out of thrust and momentum trying to get up them.

Standing waves are a cute inversion of what I just said about ocean waves.
In a standing wave, it's the geometry which is going nowhere, whereas the bits of water are very definitely travelling at speed (due to the tidal current). Luckily these are remarkably rare (except in white water rivers), and there's almost always another way around them, or (because they're almost always a tidal phenomenon) you just heave to and wait a few hours.

Standing waves are not rare at all. You can see them in any of the tidal races around the English Channel when they're running. Sighting one of these is a good clue to change course.

[capn_billl]

I was once caught in a channel with a large "eddy" that turned me 360, it was exciting to suddenly be stern first until I realised what had happened.

[GreggL]

Thanks!

I'm specifically referring to Plum Gut where the long island sound meets the Atlantic. On a cruise I'm planning, I must steer through there and was told of tide rips, I assume it's the version cause by tidal currents. I was also told that there really isn't much of a slack tide in that region so using a current table will only help me get on the better side of the window.

Does anyone have any specific advice to these waters or likewise? How can I back out if it's too daunting? I certainly don't want to get in over my head.

[Andrew Troup]

Dockhead: you're right on both counts, I reckon

Race does seem to me a better term than reusing "rip" ambiguously, and it's unfortunate it's not widely used outside the UK - even here in NZ where we generally follow UK usage more closely than most former colonies ;-). Maybe because they're so prevalent around your shores, it has come naturally to distinguish them?

And by all accounts standing waves are to be met with routinely at certain specific locations around the UK. Or indeed anywhere else with similarly irregular underwater topology and very strong tidal currents.

Nevertheless that combination is not common, and I don't feel it's too far off the mark to call standing waves a rarity in the broader context of a forum for cruisers around the world.

I wonder how many forum participants have encountered them?

[Curmudgeon]

Plum Gut is one issue, the Race (on the Southern side of Fisher's Island) is another. The Race is worse IMHO. If you want to avoid both on your way to Block Island Sound, go North of Plum Island and go through the pass at Watch Hill.

Otherwise, go at slack water or when the current is with you. Turn on your engine and take the chop head on.

[Andrew Troup]

GreggL

Hard to know what to say. I'm not familiar with Plum Gut, and it sounds like a place where rather than slackening off, the current simply clocks around the compass.

Things to avoid (in the general case) are

a) situations where a tide race in a location open to the sea is running with any strength against a significant swell. Admittedly such places generally look even scarier than they prove to be if you are forced to go through them. Generally in a displacement vessel it's probably preferable to have a 'fair' (ie following) tide direction and a foul (head-on) seaway than the other way around

b) trying to fight your way through against a race whose maximum rate is comparable with yours, unless you've been shown the back-eddies by someone who genuinely knows, or

c) going through with the tidal flow when you either don't know which bits of water are thinner than your draught, or you do know, but you may have reason to doubt you'll be able to maintain control of your position (because of strong 'turntables')

In the more general case, the most cautious option is to time your transit to around the time of slack water, but be aware that this does not necessarily coincide with high water or low water at the same locale.

Boat handling is mainly a state of mind: prepare well, and be assertive and attentive. You'll learn what you need to know by the time you need to know it.

I don't have my copy with me, but if you want to get a book from the library, I image the "New Glenans Sailing Manual" might offer some useful insights, because it's based on a part of France (Brittany) which as the name suggests is like Britain in respect of tide races, if not more so. There's a famous tidal flat where the tide comes in 'faster than a horse can gallop'

[cwyckham]

Originally Posted by GreggL

Thanks!

I'm specifically referring to Plum Gut where the long island sound meets the Atlantic. On a cruise I'm planning, I must steer through there and was told of tide rips, I assume it's the version cause by tidal currents. I was also told that there really isn't much of a slack tide in that region so using a current table will only help me get on the better side of the window.

Does anyone have any specific advice to these waters or likewise? How can I back out if it's too daunting? I certainly don't want to get in over my head.

What does it mean not to have "much of a slack tide?" If the water goes one way, then starts to go the other way, doesn't it have to stop in between?

We have many tidal rapids around here, and some get so bad that I'll only go through near slack. Even if you're going with the tide, you'll get thrown around and be completely out of control in places (skookumchuck being the most famous example, see

video

and

video

and

video

).

Other places run pretty smooth, so I'll shoot through and enjoy the ride over the standing waves if the current's going my way.

[mrohr]

Gregg:both the race and plum gut are humbling.Get a copy of Eldridge and look at the charts for the 12 hour tidal cycle (snapshots for each hour). avoid going thru at max flood and max ebb,but a fair tide is best.If any wind > say 10 kts the chop is increased and things start to get scary.I've been thru all the 3 mentioned in the posts numerous times and agree with Curmudgeon that the Watch hill passage has lesser currents and might be a better way toB.I. but will take you too far East to get you into all the good things behind Plum Gut. The ride thru the race is longer but if you catch the beginning of the ebb you will save any easy hour or more in your run to BI. Plum gut is a shorter ride but the currents seem to run diagonally thru it so I favor the Plum Is side to keep from being swept onto the shoals on the LI side Check your charts carefully ,esp. depths, and catch a fair tide and you will be thu into more open water in less than 30 mins.either direction. Lotsa ferries going thru both of these cuts so they will show you the way before you are flushed thru! I use the concept of "staging area" to await a chance to get thru these difficult areas or for waiting for a favorable weather system before an offshore passage. Duck Is roads is my choice of where to wait for your tide going East thru the gut ;going West ,try Orient Hbr. For the Race ,best is West Hbr on Fishers Is. if going East ;andEast Hbr. if you need to use the Watch Hill Passage. TheWatch Hill passage would be your choice route back to LIS via Fishers Is sound if you miss a fair tide going west from BI.-----------Do your homework and lets us know how it goes----Mike