“This is going to force us to rethink our strategy,” said Yoshiaki Kawata, a specialist on disaster management at Kansai University in Osaka and the director of a disaster prevention center in Kobe. “This kind of hardware just isn’t effective.”

Mr. Kawata said that antitsunami seawalls were “costly public works projects” that Japan could no longer afford. “The seawalls did reduce the force of the tsunami, but it was so big that it didn’t translate into a reduction in damage,” he said, adding that resources would be better spent on increasing evacuation education and drills.

Gerald Galloway, a research professor of engineering at the University of Maryland, said one problem with physical defenses protecting vulnerable areas was that they could create a sense of complacency. “There are challenges in telling people they are safe” when the risks remain, he said.

Whatever humans build, nature has a way of overcoming it. Mr. Galloway noted that New Orleans is getting a substantial upgrade of its hurricane protection system, but he said, “If all the new levees were in and we had a Katrina times two, a lot of people are going to still get wet.” Similarly, he said, some of the floodwalls in Japan, which can be almost 40 feet high, but vary from place to place, were simply too low for the wave.

“If a little bit dribbles over the top, you get a little wet inside,” he said. “If it’s a massive amount, then you get buildings washed away.”

Some Japanese experts said the seawalls may have played a useful role in this crisis.

“This time, almost everybody tried to flee, but many didn’t succeed in fleeing,” said Shigeo Takahashi, a researcher at the Asia-Pacific Center for Coastal Disaster Research in Yokosuka. “But because of the seawalls, which slowed the arrival of waves even just by a little, a lot of people who would not have otherwise survived probably did. Just one or two minutes makes a difference.”

As of Sunday, the Japanese authorities confirmed 1,300 casualties but expected that the final toll would exceed 10,000, with almost all the deaths resulting directly from the tsunami.