Rivermouths: How, why and when they fire.
What about big arse rivermouth that have waves like this on Google maps? I'm sure there's downsides because that ruler edged right looks very surfable.
BTW not here or I'd go and check it out, just an example.
I can't recall any reading material, everything I know about rivermouths comes from experience, however the most basic appreciation of why they often offer quality set ups is:
1) There's usually an abundance of sediment - i.e sand - coming down the river with which to create banks, sometimes very long banks, that may jut out on otherwise straight sections of coast.
2) The interplay of currents - water running out, and waves running in, plus the tides - sculpts that sand into forms that run at an angle to each current (think: the path of least resistance). Often that path is a good peel rate for breaking waves.
BTW that right you linked to has a terrible peel rate, at least for shortboards, though maybe OK for longboards or SUPS. This rivermouth, also located in Central America has a steeper peel rate, and it has it on both sides:
Other things:
They need to be open to be any good. The sand/sediment has to push into the ocean. If a rivermouth isn't open it's a beach.
If it's a big enough river to be tidal then the phases play a part in quality - generally the run out is better.
The type of sediment plays a big part. Sand will move quickly, both into place and out of place if the river slows and wave action dominates. Coarse sediment and rock, such as rivers in Japan and NZ that open on the spring thaw take longer to form but will also hold shape after the current slows.
When surfing rivermouths you need to look out for debris (logs, branches), garbage if near urban areas, plus the biteys that congregate to feed on lesser species. Rivermouths near farmland may also be home to all manner of chemicals, and very often rivermouths break open after rain which brings the complications of sewage into the equation.
I remember once about 25 years ago the Murray mouth formed an incredible long righthand bank, after paddling across from Hindmarsh Island and rounding the corner you could see waves peeling along quite close to shore for hundreds of meters. Everyone was on to it but the sea life was a bit of a worry. It lasted a month or so and then it was gone. Never seen it anything like that since. I'm wondering if this current flood might do it again. Also, everyone remembers that bank at the Onkaparinga mouth in the early 80's? which coincided with a clean 3' swell. It tried to do it again about 5 years ago but before a decent swell arrived all the sand moved down to the hump which had a good long left all summer and was fun even on 1' swell at low tide. Cheers.
a certain consistent beachbreak in Geralton has excellent rivermouth banks after a lot of rain but is sharky and full of fish as anywhere iver ever surfed.
Old-dog, looks like the flooding has been too gradual to bust out the bank. Here's the current imagery..
old-dog wrote:Also, everyone remembers that bank at the Onkaparinga mouth in the early 80's? which coincided with a clean 3' swell. It tried to do it again about 5 years ago but before a decent swell arrived all the sand moved down to the hump which had a good long left all summer and was fun even on 1' swell at low tide. Cheers.
October 9th, 2016. Images from our South Port surfcam.
The arguably most popular wave in Taiwan is a classic rivermouth setup:
(Not my pics btw, just random ones from the net.)
It gets really good and I had it to myself for a few months on end a couple decades ago, in the early days of surfing in Taiwan. It's pretty crowded nowadays, very well known by Japanese surfers.
Yes Groundy it's been alright, certainly on the better side of all the times I've checked it over the years.
Thanks for the current photo of The Mouth Craigo.
I've been wondering if we might get a bank there.
The flood still hasn't reached it yet.
Love them, best ones seem to be ones that sit alongside a point or in a bay then outgoing to low tide is bliss.
@ thermalben, yeah, I reckon I surfed it that day in2016, Danny Higgins was also there. The bank had really good shape but a bit too small and soft, lucky shot I reckon. The day back in the 80's? was really pumping, Gary Weed and all the Roaders crew dominated and it was hard to get a look in if my memory serves me correctly. The only consistent thing about the mid is its inconsistency.
@Craig, I'm not sure if the flood has reached the Murray mouth yet, when it was good the whole shape of the coast changed into a sand spit jutting right out. Looked like a real point break.
Here's a pic of the Murray Mouth from '93 (towards the back end of that magical run, apparently) from our forums (posted almost ten years ago!).
TBH I reckon that particular setup was a fluke; a suggestion that's reinforced by the fact that it hasn't really been seen in the following three decades.
The angle of the bank back then - let alone its position (on the western shore of the mouth) is not consistent with sand flows associated with a typical flooding rivermouth scenario (an alluvial fan). So I'd be very hesitant to expect anything amazing in the surf department over the next 12 months.
stunet wrote:If it's a big enough river to be tidal then the phases play a part in quality - generally the run out is better.
Most rivermouths I've surfed are nigh on unsurfable on the outgoing. Rippy, choppy, with bad currents and standing waves. Unless the bank is detached from the flow, that is.
Some like the run out, but in my observations most don't. I've generally found that you want the tide to be at its lowest, and just starting to run in. This is usually around an hour or even 2 after when the low tide estimate is given for the particular location. Then it's time to get busy before the tide floods the bank.
Depends on the tidal amplitude- I like the last of the run out as the flow slows- helps get that standing wave/suck out effect.
Yeah, guess it may change a bit, but the two rivermouths I've surfed most in my life - one admittedly not a classic rivermouth but still a river breaking into a wide-ish bay, and the other a north coast bar entrance - both preferred a run out, or at worst a slack tide.
Another one located south of where I live also prefers a run out, though it can get hectic if the bank is closer in.
River bars can have very different requirements to breakwall set ups inside of the river bars.
Main issue with either set up is that you want to be fit and confident in your abilities. There will be a constant paddle against the tide and the river bars are typically very exposed and a long way from shore. Inside the river bar can also have a strange area of bumpy disturbed water that is difficult to paddle in when the swell is up. Let alone the Noah’s.
Can anyone link me any reading material about how, when and why rivermouths get good? Or any lurking rivermouth surfing enthusiasts want to share their wisdom? They're a total mystery to me and I'm in a country where I suspect there's some good ones around, totally empty. Once I get a car I'm keen to start exploring!
What about ones that are always open to the ocean, ones that are closed and only open after rain? Does the size of the river have an affect? The altitude at the start of the river? The makeup of the river bottom (sandy/rocky)? Speed of the outflow? Best tide (incoming low I think but I don't know)? Size of the rivermouth? Are the beachies better to one side of the rivermouth i.e other side of the dominant swell direction?
So many variables! Any help would be greatly appreciated.