When is a hurricane like a tsunami?

A scientific study released this week says hurricanes and tsunamis are alike when they hit land.

From completely different causes, both tsunamis and hurricanes produce enormous amounts of water moving onto land. In hurricanes like Katrina this high water can do more damage than wind or even broken levees. Scientists in America studied Katrina and the 2004 Indian Ocean tsunami.

Here's how tsunamis and hurricanes act alike, causing heavy damage onshore. Most structures are constructed to deal with gravity, rain, or even wind. Almost none have the necessary strength to withstand the force of water rising from underneath or the side. And that rising water often floats large debris into fixed objects. A photo exhibit from this research project has opened at Princeton University. One picture shows a series of cement pillars mowed down by a floating eighteen-wheeler container slamming into them from the side.

As researcher Yin Lu Young of Princeton says, "Eighteen-wheeler containers, free-floating barges and boats can all become projectiles."

Young and the other researchers also found the high water has an unexpected similarity to some earthquakes. The flood water sits over often-sandy soil. Pressure forces water into the earth beneath. When the water finally does recede, sandy soils are especially prone to liquefaction, sometimes opening large potholes as the watery soil flows out with the receding water. This can undermine roads and foundations.

The purpose of the project was to help engineers and architects deal with all the possible stresses on buildings in low coastal areas. Young's hoping to see some differences as areas damaged by Katrina and tsunamis are inevitably rebuilt. "There is a certain stubbornness about not learning from past mistakes," she said. "People like to do what they did before because it's easier than fixing the root of the problem...engineers can learn from this and modify future design codes to minimize damage."

And we all know there'll be more hurricanes and other tsunamis.