GRANTS PASS, Ore. (AP) - Many of Oregon's beaches are eroding faster than in recent decades due to a combination of less sand coming out of rivers, rising sea levels and bigger waves, according to a government report released Monday.
The U.S. Geological Survey study is part of a nationwide assessment of coastal erosion and completes the latest look at coastlines around the lower 48 states.
It found that since the 1960s, 13 of 17 stretches of beach in Oregon have changed. They went from building up sand to eroding, eroding faster than before, or building up less than before.
Lead author Paul Ruggiero, an associate professor at Oregon State University, said the primary reasons are less sediment flowing down coastal rivers, sea levels rising due to climate change, and bigger ocean waves, particularly during winter storms.
Two locations particularly hard-hit are Neskowin in Tillamook County and Beverly Beach near Newport. They have seen a loss of about three feet of beach a year since the 1960s.
In general, Oregon has seen more erosion than southwest Washington, which has seen beaches building up with sand from the Columbia River, Ruggiero said.
While dams serve as roadblocks for sand that would otherwise restore beaches from erosion, the slow water in estuaries at the mouths of rivers is the main impediment, causing sediment to drop out of the water column, he said.
Other studies have shown the landmass on the southern Oregon coast and around Cannon Beach are rising due to shifts in the tectonic plates, offsetting the rising sea levels from climate change, he said. But sea levels are rising on the central coast and in Tillamook County.
Other research also has shown that waves are getting bigger, eating away more of the sand, Ruggiero said.
Rob Thieler, a research geologist for USGS who oversees the national coastal erosion assessment, said Oregon, with abundant rock formations from ancient lava flows, is not seeing as much erosion as other parts of the country, particularly the sandy coastlines of the Gulf of Mexico and the southeastern U.S.
Online: USGS report: http://pubs.usgs.gov/of/2012/1007/pdf/ofr2012-1007.pdf