Artificial Reefs

CN: These guys are looking in serious detail. If the waves comes to Rincon, how does it break through the area? If it sections, then what happens to cause that? It's fine details they've done to see what's going on. The surf science stuff I think is really impressive because it has an applicability way beyond designing reefs.

If we can better understand why waves break where they are, and how they change when the coastal environment changes, then we can look at beach renourishment projects, map surf spots and monitor change. So in terms of protecting surf spots, the science these guys are pushing is also really great.

I think it's pretty exciting stuff.

CD: So how do they categorize different waves?

CN: They've come up with about five or six categories to describe wave types. There's wedges, platforms and different combinations of these things.

Pipe for example, is a wedge, Trestles is a platform.

We saw a lot of pictures of their computer models. They have done wave tank models, but most is based on computer models. If there's any fault to what they're doing, it's that they do a lot of relying on computers for their models. They do a lot to compare things and see if the models are working right, but they may be a little over-reliant in their modeling.

CD: Why has Narrowneck Reef been successful and others not?

CN: I know the least about Cables. Pratte's was clearly too small. It didn't have a big enough footprint. The coastal processes that are going on in El Segundo are of a magnitude that is so much bigger than Pratte's reef that the reef is basically inconsequential.

CD: How so?

Pratte's Under Construction

CN: The sandbar that forms when the surf picks up is basically so much bigger than the reef -- it basically just buries it. When the surf gets big, it breaks outside the reef.

But we only had a limited amount of money to work on Pratte's, so we built the biggest thing we could, and we built it on the cheap. We got a lot of deals and good will to build that thing, but it's way too small.

Narrowneck reef in Australia -- I don’t know the exact cost, but it's in the millions. Pratte's reef cost five hundred grand and that included permitting and design. The Army Corps of Engineers spends that much in a day.

The thing about Narrowneck -- the primary goal of that reef was not to create surf. It was to stop erosion. They built it offshore. If you build a breakwater offshore, you reduce wave energy and you get what's called a salient -- which is a mound of sand offshore behind it. So the question was -- can we build something that creates surf and has that effect? It looks to me like they're doing some very intensive monitoring on the coastal erosion and processes -- less on the actual wave. In fact, they're actually not doing a very good job of monitoring the surf. We saw a video of the waves breaking on the reef that looks really nice. And we've gotten anecdotal reports of guys getting good waves. So it sounds like it's working, but there's not a rigorous program of monitoring the surf conditions -- only of the erosion control elements. You need to monitor the surf too -- how often it's good, what sort of swells work there -- that sort of thing, to really know if the project has been successful.

Narrowneck Reef is the Dark Spots Underwater
Photo: Australian Surfing Reef Design

CD: How's the reef set up?

CN: Narrowneck's interesting. It's longer than it is wide. It has two parallel bumps and acts more like a detached groin than a breakwater. It's been two years in construction and it's still added to every day. It actually doesn't look very much like the original design because of limitations of the construction techniques.

CD: Has it had an effect on erosion?

CN: I think so. It's changing everyday. But it seems to be reducing it.

CD: What does the wave do when it hits the reef?

Well the reef's huge. Enormous -- hundreds of meters long -- and when a wave passes over the top of this thing, it causes wave focusing, just like Lowers. And then a wave peels off, a left and a right. It's unclear from the video exactly, where along the reef it's breaking. The wave could even in theory break inside the reef. All the reef does is focus the energy. But does it work five times a year, 250 times a year? It's kind of unfortunate that we don’t really know the details of what it's doing.

CD: Down the road it would be interesting to see what sort of an effect these sorts of reefs would have on erosional beaches on the east coast and California. This is something people with threatened property want to build offshore from Solana Beach. They're ready to go ahead with building offshore reefs to deflect the wave energy and create surf spots. But it seems like it's a much more complex equation than just that.

CN: Well, you know down in Encinitas and Solana, there's a ton of offshore reef out there already. I mean look at all the reefs in Cardiff.

CD: What if you build a reef, and it robs the wave energy from a nearby surf spot?