I felt conflicted over this week's lesson on engineering structures for tsunami survival using a scale model. I didn't want students to laugh over or trivialize the enormous trauma our brothers and sisters in Japan are undergoing. I did want to give them a better sense of a giant wave's size, scope and destructive power while teaching about tsunamis being a natural (unpreventable) disaster. Not a single person should think that anyone in Japan bears fault for the earthquake or tsunami. I want to help in some way by contacting a Japanese homeschooling group similar to ours here to find out what we can do. I'll update everyone as that effort comes together.
- Tsunamis travel faster than the beach waves we bob in. Most beach waves are created by wind traveling over the ocean for long distances. Their speed must be less than the speed of the wind. Tsunamis are created by earth movement in the deep sea and are not limited by wind. They can travel up to 500 mph.
- Tsunamis are much higher than beach waves. Because of how shorelines are shaped, a two-foot shift in deep seabed can translate into a thirty foot (or higher) breaking tsunami wave at the coast.
- Engineers can improve building tsunami survival odds by materials design and changing building structure and geometry. Stronger materials are better but more expensive. Minimizing exposed surface area helps too.
Armed with six model houses (two from each material) the students placed their houses on the beach. We generated a scale-model thirty foot wave (video below shows how). Some houses were placed on sand 15 to 20 feet above sea level and were inundated. Toothpicks elevated other structures (some to ludicrous heights) and those fared better. Students observed how housing material and shape related to damage. They thought about the tradeoffs between material strength and cost, and between safe height and a height that occupants could actually reach!
Students did a wonderful job. They collaborated, practiced the design cycle (they were able to rework the buildings and have a second trial) and learned some STEM concepts. I'd say they also gained a better appreciation of the challenges engineers face due to tsunamis.
Additional resources: here's some recent tsunami survival design from a collaboration beteween Harvard and MIT: the Tsunami Design Initiative and SENSEable City.