On Sunday 19980222, after a trip up Nth to explore an old power station with J. S. and his girlfriend M., we stopped in the afternoon at Jenny Dixons Beach on the way home, for a swim.
There was a lot of seaweed washed up on the beach, and I had an idea. Composite building materials! You can do all sorts of things with them, even things that you'd expect would be impossible. What was that about building sandcastles in the sea surf?
I noticed the tide was out, and turning in. I gathered up a great heap of seaweed from the beach, and piled it just above the present furthest line of the surf. Then I started building a mound, also just above the present surf line.
I'd pile up a few inches of sand, then lay seaweed fronds radially - with the roots near the center of the mound, and tips facing outwards. Also some fronds fully crossing inside the mound. Then more sand, and so on, building it up in layers. The idea was that the structure would be resistant to erosion by waves, since the seaweed would hold a core of sand in place. It also allowed for a steeper, taller sandpile than plain sand alone would have.
When the pile got to about waist height, the waves were already washing around the mound base. I'd been planning to do a fairly elaborate 'castle' on top, but wasn't too sure the mound would last for long, so switched to a relatively simple, quick 'castle' design. Actually, it's not a castle, but is meant to be a reclusive scientist's remote mountaintop astronomical observatory.
By the time I'd finished it, I was realising that the mound was going to be fine, and I could have taken my time. The waves were still retreating fully from the base, but each new wave was now impacting up to six inches high on the base, solidly enough that the mound would actually shivver slightly with the impact. Yet the sandpile was not significantly eroding! The seaweed reinforcing idea seemed to be working really well.
So well, that when we left later in the afternoon, with the shadows of the hill behind stretching out over the beach, the 'castle in the surf' was still standing strong.
Any ordinary sandcastle would have been jumped on by children many times over by now. But remarkably, with this sandcastle standing strong amid the waves, children would stand and admire, and never touched it.
