Marine biology and surf Science

[doclach]

Thanks Ralphy - a much more balanced perspective than what I had heard... man, why don;t they ask cats like you that know the local wave forms so well??!! must be sooo frustrating for ya.... hope they give ya one up your way..

[captain6230]

ralphy quick question! what would happen if say me and my mates slapped together some ply wood or something and anchored to a shitload of scrap metal and plonkled at our local beach? would it affect the beach much? iv been tempted to try this many times under the influence of alchohol.

[matt]

haha Nice Q Captain ... homemade reef perhaps!!

What about the other one i've heard where at a beach with a river outlet you dig a big trench from the outlet to the beach break to let the water flow out though there to sea. Apartentaly you can get a free standing wave forming? ... So i've been told would that happen has anyone done it?

[doclach]

Ah yes lads - or there is a totally 'natural' way to get waves when it is otherwise flat..haha - (please excuse the stand-up)..

[youtube]http://www.youtube.com/watch?v=mKRR9RMmcIQ&feature=related[/youtube]

[ralphy]

Ahaha Cap, well i have contemplated doing something similar.
In all honesty the best thing to do would be to grab some old cement blocks/rocks etc and place them when the ocean is flat.
Dont do it though

One of the major reasons some of the ASR reefs dont work is that they are not big enough to help shoal the waves onto the reef. If you have a look at some of the better surf reefs (there have been studies done) around they have a pretty big shelf that comes out of the deep and meets the highest point of the reef. This acts to help shoal the swell into a peak onto the reef, where it can then peel off along the slanted sides of the reef. Yes most of these reefs are deepwater ones, but they all still have some sort of shelf off the back that helps to move and shoal the swell lines onto the reef.

[doclach]

Damn Speed hump at my local this morning!!! haha

- thanks to Mal for the shot:

[doclach]

FETCH

lots know what it is, a few probaly don;t, so thought i would quickly throw it up here for reading surf forecasts.
In good forecasts and reports you will see the term 'Fetch' in reference to wind. it's one of those words you can notice, but not necessarily know what it means.
"Fetch" is refers to wind - it is essentially the distance wind travels over the ocean. it is thought that the longer the "Fetch" length for wave formation the more waves you are likely to get in a set. This is termed "length of fetch". Fetch also has 'breadth' - this is how wide the wind front is. A 'wide' fetch combined with a 'long' fetch will usually give rise to a good groundswell. think of it like a bulldozer - the width of fetch is like a wide blade on a bulldozer and the length of fetch is like the size of the engine in the bulldozer and the lump of dirt being pushed at teh front is equivalent to the groundswell. not a perfect analogy , but hopefully Ok to get things understood.
oh yer - if you see a term "the head of the fetch" that just means where it starts from - usually a deep ocean storm event.
cheers

[steve wall]

Japanese Sub doc!!

[doclach]

Japanese Sub doc!!

the green icon thingy - yer i was wanting to use it ,,, and seemed like as good a spot as any..haha.. pretty kooky aye

[brad]

FETCH

lots know what it is, a few probaly don;t, so thought i would quickly throw it up here for reading surf forecasts.
In good forecasts and reports you will see the term 'Fetch' in reference to wind. it's one of those words you can notice, but not necessarily know what it means.
"Fetch" is refers to wind - it is essentially the distance wind travels over the ocean. it is thought that the longer the "Fetch" length for wave formation the more waves you are likely to get in a set. This is termed "length of fetch". Fetch also has 'breadth' - this is how wide the wind front is. A 'wide' fetch combined with a 'long' fetch will usually give rise to a good groundswell. think of it like a bulldozer - the width of fetch is like a wide blade on a bulldozer and the length of fetch is like the size of the engine in the bulldozer and the lump of dirt being pushed at teh front is equivalent to the groundswell. not a perfect analogy , but hopefully Ok to get things understood.
oh yer - if you see a term "the head of the fetch" that just means where it starts from - usually a deep ocean storm event.
cheers

Such an important theory when it comes to forcasting waves. You can read a surf report that says 4-8ft swell with light offshore winds rock up to the beach and find that yeah the swell's big and there's back spray coming off the waves but the waves are coming in randomly with wonky lips and no real shape this is usually the case with storm swell's that are generated close to the coast winds are powerful enough to push the swell into your reef/beach but they are un-organised with shit shape. Sometimes these big swells can just be a pain in the ass and not even fun to surf, I always check the swell period when it gets above say 7 or 8 seconds things are getting better 10-12seconds plus and things are shaping up real well.

[JONNO313]

That was worded perfectly. Great stuff guys.Im sure users are really going to benefit from that.

[bullinachinashop]

been meaning to ask for a while:

part 1 - Ive never really understood how ocean tides affect the temperature of the sea. especially around Sydney. Can anyone explain or post a good link?

part 2 - why do they close beaches? again, im looking for a sydney centric answer if you please

thanks!!

[doclach]

been meaning to ask for a while:

part 1 - Ive never really understood how ocean tides affect the temperature of the sea. especially around Sydney. Can anyone explain or post a good link?

part 2 - why do they close beaches? again, im looking for a sydney centric answer if you please

thanks!!

hey Bull...
1. ralphy will be able to give a better answer about the tides, but essentially it is about the disturbance and distribution of different temperatures of water 'layers'. Have you done SCUBA diving? Off South Head is a classic for some reason - when you are going down to depth or coming up particularly (cos is slower) you can see through your dive mask certain 'wavy' layers in front of you. these are where water layers of quite different temperatures are laying on top of each other. These are called "Thermoclines". We dive with temperature measuring gear and it shows the immediate changes. Tides bring in these different layers of water as one body.
Further to this, you will likely be well aware that as you go deeper, the water usually gets colder. When the tide brings water in , it doesnt descriminate between cold and comparatively warmer water.
Thirdly you are looking at the tides affecting currents. How many times have you paddled out on your boog and felt yourself go through 'cold' or 'warm' patches (apart from where your mate just peed in the water..haha). a tide can push in or pull out a current of a particular temperature.

2. Closing beaches... this is up to the discrimination of the life guards on duty. Essentially it is about currents along the beaches, especially rips, which I'm sure you have heard of. Rips and gutters can contain powerful currents which can drag swimmers out of their comfort zone ... which usually means trouble.
Sydney - wise i dont know where you are, so I'll give some quick examples.
1. tamarama - where my boog club is. to look at pretty tame, but it is supposedly one of the most dangerous patrolled swimming beaches on the east coast (statistically). This is because it gets a massive cross current which at one end drags swimmers into a cliff with recesses under it (like small caves sort of) and the current swirls there and traps them, on the other end it will drag them out and around the reef and leave the waves to smash them into the front o the reef. Also for a beach break I have had some massive hold-downs for no particular reason. Not long ago there
was some decent swell around - not massive and I thought it was a fair paddle out - and one of my mates, who takes big stuff on said it was one of the hardest paddles of his life... just weird there.

2. South Curl Curl. Now there is a freaky spot... the NB guys here will know it. If the swell/current combination runs a certain way, it will take someone out along the rocks like a rocket - or bale them up in the corner - I have been there in storms and it gets crazy.

So there are a couple of examples from a sydney perspective - the idea of 'closing' a beach is to protect the public from themselves. Bronte gets some hell strong currents and it isn;t rare to bring folk in on my booger when the beaches are unpatrolled (I'm often out after the flags are down - and always when the beach is closed - cos is usually storm - yew!) , one chick was trying hard to drown me at the end of last season panicking.... had to organise her and her boyfriend at the same time...

Hope that helps a bit mate.. ask more if you want more specifics and I'll see what i can pull out of the bag.

[ralphy]

Spot on Doc. Warm water is less dense than Cold water, hence will rise up and sit on top of cold water. Tides, as Doc has said dont care what temp the water is at, it just brings it in, generally causing them to mix etc.
Winds and currents have the most affect on water temp

[bullinachinashop]

doc,

tamarrama. i tried to surf there a few times as a young kid and got wasted. yet now im near 30 and a much stronger swimmer, you have a club there?

its not gay is it? ha!