HONOLULU (HawaiiNewsNow) -
It is no secret Hawaii is slowly eroding into the ocean, but you may be surprised at just how quickly the sea is closing in.
The University of Hawaii and the United States Geological Survey have published the most comprehensive report ever on coastal erosion in Hawaii. The report documents shoreline erosion on Oahu, Maui, and Kauai and is one in a series of reports on shoreline change in coastal regions of the United States.
Researchers used aerial photographs and maps to measure shoreline change at more than 12,000 locations on the three islands studied. The report concludes 9% of the beaches on those islands have vanished over the past 100 years and 70% of the remaining beaches are eroding. The average rate of erosion is almost half a foot a year.
"The most rapid rate of erosion we found is a Kualoa Beach Park. And the rate of erosion there, the maximum rate of erosion, is on the order of six feet per year," said Dr. Chip Fletcher, UH Geology and Geophysics Professor and lead author of the report.
"This points to the fact that our beaches are not in some sort of equilibrium where roughly half are eroding and half are accreting. Instead there is a net erosion, there is a net retreat of the shoreline towards our developed coastal plane," Fletcher said while referring to the report.
"Over the past century, century and a half these natural erosional processes have been increased because of human being's mismanagement of our shoreline areas, i.e. building too close to the shoreline," said Sam Lemmo, Administrator of the Office of Coastal Lands for the state Department of Land and Natural Resources.
When ocean front homes are threatened, people build sea walls. The sea walls save the homes, but the beach in front of the property almost always disappears forever.
"We need to make some difficult decisions about which beaches we are going to protect and which communities were are going to allow armoring to take place and which communities we might pursue another strategy such as relocation," Lemmo said.
By relocation Lemmo is referring to moving people out of their coastal homes and prohibiting sea walls so the beach can survive as it slowly moves inland.
Fletcher agrees, private home owners may eventually have to be relocated so beaches can be saved.
"I really think that the only way we are going to have some beaches left in the future is if we purchase the land. Because when a house is built, we have yet to say, 'No sea wall,'" Fletcher said.
Fletcher said Kauai County has the smartest law in the state governing ocean front setback (distance from ocean in which structures can be built). Structures on Kauai must be set back the anticipated distance of erosion over 75 years plus another 40-feet.
For example, if a property experiences annual erosion of 1 foot, it must be set back 75-feet plus another 40-feet for a total setback of 115-feet.
Both Fletcher and Lemmo believe lawmakers should adopt a statewide setback law at least as strict as the policy on Kauai.
Of course on Oahu most shoreline property has already been developed further complicating the problem.
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