The importance of tides

The Kimberley coastline is very shallow. In fact, the continental shelf goes out an enormous distance, so as sea levels have changed in the past, this coastline has changed tremendously. And Broome itself is also very flat. Partly as a result, the area has some of the biggest tides in the world. According to the locals, Derby (which is just up the coast) has the second largest tides in the world (after the bay of fundy) and Broome itself has the fourth largest. 

I haven’t heard exactly how big the tides are, but they’re probably somewhere around 15 metres. That doesn’t seem like much, but when it’s combined with a very flat coastline, you get tides that go out over a kilometre around Broome itself, and fifteen kilometres nearby. The entire bay loses all its water. Every month, some unsuspecting person loses their car to the tide. A couple of years ago, ten cars were lost to one tide. There is a phenomenon called the horizontal falls, where the tide is going out from Derby through a very narrow channel, and the inside becomes eight metres higher than the outside. There are islands that rise up eight metres above the ocean although they’re below it at high tide.

Because of the tides, Roebuck Bay (the bay that Broome faces) is the most biodiverse estuary in the world. It’s a RAMSAR wetland, with birds that come from Siberia. The RAMSAR area includes 160 square kilometres of tidal mudflats in Roebuck bay. It’s estimated that 300,000 birds a year use the area, it has all seven species of turtle that are present in Australia (some of which are endangered), and the second largest population of the snubfin dolphin. I went on a tour of the bay

As you go to the water, there are a lot of potholes in the sand. These are where stingrays settled before the last tide.

We also visited Dampier Creek which is full of mangroves and birds.

And then there are all the dinosaur footprints - over 100 kilometres of footprints from at least twenty one species. The most dinosaur footprints anywhere in the world by a long way. There were four types of dinosaur here - theropod, sauropod, ornithopod and thyreoporiean dinosaurs. The largest dinosaur footprint in the world is here, but we didn’t see it. I got to stand in an ornithopod footprint.

There was a long track of them.

You can see from this one how much they compacted the mud they were walking through.

And one of the predators.

And it’s absolutely beautiful.