Tidal Waves?
- Thread starter druid
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Oh baby, I was right! How about the memory on that guy?
https://en.wikipedia.org/wiki/Tidal_bore
I witnessed such a thing one time while riding my bicycle along the bike path adjacent to the San Gabriel River down in Long Beach. It blew my mind! I did some research on it when I got home and learned about the phenomenon.
https://en.wikipedia.org/wiki/Tidal_bore
I witnessed such a thing one time while riding my bicycle along the bike path adjacent to the San Gabriel River down in Long Beach. It blew my mind! I did some research on it when I got home and learned about the phenomenon.
Aahhh... that's not exactly what I'm talking about (although it's an interesting phenomenon). I'm talking about the waves created on the ocean (or at least in Georgia Strait!) that are caused by tidal currents colliding, sometimes enhanced by river currents or wind-waves. Have a look in Vancouver Harbour west of Lions Gate Bridge when there's an outgoing tide. If there's anything like a westerly wind (like 5 knots in the harbour), there will be 6-8 ft waves generated. It's even worse at Sandheads, or outside Porlier Pass with a westerly flow and flood tide. There's "tidal waves" of 2-4 ft all along the Sunshine Coast when there's a flood tide, even with no wind at all.
What do you call these things?
druid
What do you call these things?
druid
About ten years ago I was sailing in a light breeze south bound just off Seymour bay, Bowen Island, when I saw a step (change in water height) of about one foot coming towards me with smooth water behind it. My sailboat easily climbed to the higher level with incident. Later talking to an old salt, he said it is not unusual to find a "tidal wave" or "tidal bore" in the channels leading into Howe Sound and the Fraser River during a large swing of a flood tide.
On San Francisco Bay, we'd call them FLEBBS, we made that up or got it from Latitiude 38 or Kimball's Sailing The Bay book, where the flood met the ebb. But there were only 6 feet of normal tidal range. Up your way, druid, you're dealing with 14 foot tidal differences, so when the incoming meets the outgoing there are larger differences. You're also talking about two different things here: ebb meets flood vs. wind again water. The latter can occur in the same place on different tide directions with different wind directions. Of course, your third is when river outflows meet tidal streams, but those are only bores in the river entrances, not out to sea. The Columbia River is infamous for setting up just these conditions on big ebb periods.
Names? Heck, I dunno, but I'm sure some research would turn 'em up.
Names? Heck, I dunno, but I'm sure some research would turn 'em up.
The reason I want to give them a name (actually "standing waves" is pretty close) is that People don't understand me when I talk about bashing through 4-6 ft waves when there isn't any wind. ("make sure you check the forecast and don't go out if the wind is too strong...") Yes, they do get a lot worse when combined with wind-waves and/or river currents, but the concept is the same. Yes, the mouth of the Columbia is a good example (Grand-daddy version of here at Sandheads). But ones that occur because of river currents are easy to predict. The wave action along the Sunshine Coast is pretty much random - it seems to occur when tidal currents meet, but that can be ANYWHERE.
More Research Required...
druid
More Research Required...
druid
Around here we refer to what you are referring to (I think) as "tidal rips". They form frequently in a river where the tide is coming in and the river is opposing the inflow of tide. I don't recall seeing them when the tide and the river current are going in the same direction (ie on an ebb) It is typically a standing wave, often parallel to the general flow of the river at the edges where the river current is not as strong.
Smokey, yeah... kinda. What I refer to as "tide rips" is the change of direction, usually a line where debris collects. In the open Strait, they're not a problem except you have to watch out for the debris: there can be Nasty things in there like plastic bags, fishing line, nets... In places where the current is strong, the rips can throw your boat in a different direction in a hurry, and you have to be aware of them. You can even use them to your advantage: if the current is against you, look for rips which might indicate a favourable shift in current direction.
I guess they can refer to the waves as well...
druid
I guess they can refer to the waves as well...
druid
A standing wave is very specific, result of seich effect in a constricted waterway like a seawall line canal, results from a wave typically from a wake which the wave length and period coincide in sync so that the crests and troughs appear to be stationary.
