Windlass and SMS: My Personal Tsunami Survival Kit

[grainedetoile]

With Graine d'étoile we experienced several Tsunami alerts during the last two years in western pacific. One was reasonably serious, and it was a matter of seconds for saving the boat.

Here is our experience and how we are now dealing with this threat.

30th of September 2009, we were in tongas, in a delightfull anchorage close of the beach of a small island, separated from the main island by a reef with only two feet of water on several square kilometers. At 8h00, a moderate tsunami wave (<2m) generated by an earthquake in Samoa arrived on our anchorage. We hear a loud underwater noise. jumping on the deck we saw all the reef emptying, with tons of waters going out through the anchorage (the current was more than 7 knots, maybe 10 or 15kt, the noise was broken coral rolling on sea floor). I just ran to the windlass, hurrying my wife to start the engine. Time to get all the 20m of chain on board, the landscape had completely changed. The current began to invert, and with the engine we slowly extract from this trap. Less than 100 meters bellow the anchorage the sounder indicate 80 m depth, and all is calm again.

Friend of us who started to get their chain up only 15 seconds after us were aspirated to the reef, and banged in several coral heads during the three next waves . They finally cut their chain and leave this dangerous place, with structural damage to their catamaran.

Lessons learned :
1- Tsunami effects at the anchorage are mainly due to strong current when water go in and out flat places. The “wave” itself was not visible

2- An operational electric windlass is a safety piece of equipment on board. Giving us the ability to leave the place in a matter of a minute it saved our boat from going aground. Being able also to drop the mooring line in emergency (with a buoy), is also a plus.

3- Early warning can make the difference. The earthquake in Samoa happened one hour before the wave arrived in Tongas. We now subscribe to a website that send us automatic alerts on SMS for tsunami about 12 minutes after any big earthquake. That's free. If you are, like us, living close to the seashore that can help you to prepare your boat and yourself for a tsunami.
The website is GDACS www.gdacs.org

And now?

We are living in a small marina in loyalty islands, close of new caledonia. The shore is flat for hundreds of meters before the first hills. For the big Japanese tsunami this year, we got an early warning, and we spend the night out at sea.

Last Tuesday we got also a big earthquake (level 7) less than 70 miles from the port. We didn't consider leaving the port, because it is more than 5 minutes of tricky navigation through the reef to get in hundred meter of water. As the family was on board we stayed on board, lines ready to be freed, engine running, swinging keels up. The fact that our hull is a robust alloy construction allow us to expect that in case of a big one our chances are better inside the boat, than running up in the countryside. The first wave arrived in 4 minutes, but was only 40 cm of amplitude, generating finally no troubles for us this time.

Graine d'étoile
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