Debris from the Japanese tsunami is starting to wash ashore on the U.S. West Coast in a big way.

Beachcombers from Northern California to Alaska are finding fishing floats, soccer balls and ships that have drifted thousands of miles across the Pacific Ocean after being dragged to sea by the March 2011 tsunami -- even a Harley-Davidson motorcycle that was traced back to a tsunami survivor.

Authorities this week confirmed the largest arrival yet: A 66-foot dock that floated onto a beach near Newport, Ore.

Still, marine scientists say a far bigger problem is the untold amount of everyday garbage swirling in a vast, slow-moving vortex known as the Great Pacific Garbage Patch. That's the popular name for the vast concentration of debris -- most of it confetti-sized flecks of discarded plastic -- circling endlessly about 1,000 miles off the California coast.

A study released last month found a 100-fold increase in plastic debris in the garbage patch over the past 40 years.

"I'm more concerned about our constant input of trash than I am about these one-time disasters," lead author Miriam Goldstein, a graduate student at the Scripps Institution of Oceanography at UC San Diego, told the Los Angeles Times.

"We can’t prevent terrible events like the tsunami, but dumping plastic into the ocean is something we can control and don’t do very well," Goldstein said.