Political leaders and land managers are failing to protect Hawaii’s beaches despite policies that call for them to safeguard the natural shoreline.

That’s the conclusion of a new study by University of Hawaii-Manoa researchers who documented the disappearance and narrowing of beaches on a section of Oahu’s windward coast over the last century.

The authors of the paper, “Failure to protect beaches under slowly rising sea level,” say tougher policies and adherence to them are needed to better preserve beaches across the islands. Otherwise, a growing number of Hawaii beaches are going to shrink and vanish as climate change-driven sea level rise accelerates, the scientists warn.

While sea level rise isn’t the problem by itself, it acts to hasten beach loss when property owners protect their eroding shores with sea walls, revetments and other structures that interrupt natural coastal processes such as sand migration, according to the study.

The paper, published in the scientific journal Climatic Change, documents a trend of beaches dwindling in size and, in some cases, disappearing altogether as shoreline development and coastal “hardening,” or man-made structures, proliferated in recent decades.

Regulatory loopholes, ineffective enforcement and a narrow view of the bigger picture are part of the problem for government agencies tasked with protecting the natural shoreline, the study concluded.

“The loss of beaches because of one sea wall after another is a perfect case of agencies failing to track the accumulated impact of armoring the shoreline,” said Chip Fletcher, an associate dean and professor in UH’s School of Ocean and Earth Science and Technology and senior author of the new study.

“If you want beaches in the future, you are going to have to allow the beaches to migrate landward, which means that our homes are now in the wrong place, our roads are now in the wrong place and we need to figure out an exit strategy, a way to get out of the way,” Fletcher said.

Area of study

For the study, the scientists focused on a nearly 5-mile stretch of reef-fronted shoreline from Hauula to Makalii Point. They examined photographs and historical evidence from 1928 to 2015 to document erosion, sea wall construction, coastal development and major wave and weather events.

The evidence indicated that over 87 years:

>> Shoreline hardening increased 63 percent.

>> Shorelines went from amassing sand to eroding along 74 percent of the coast.

>> More than 45 percent of the shift was due to flanking, or erosion triggered by nearby hardening.

>> Nearly 20 percent of beach length has been lost, while 55 percent of beaches have narrowed, with most of the beach erosion occurring in the last 40 years after formal policies were established to protect the natural shoreline.

The section of Oahu coastline is representative of the rest of the state, according to the study, and the data is typical of statewide and nationwide patterns of coastal destruction by shoreline hardening.

This is not a surprise, the researchers said. A 2012 study by Fletcher and colleagues found that more than 13 miles of Hawaii beaches have been lost due to shoreline hardening.

Short-sighted decisions

Congress enacted the U.S. Coastal Zone Management Act in 1972 to “preserve, protect, develop and where possible, to restore or enhance the resources of the nation’s coastal zone.” The Hawaii Coastal Zone Management Program was established five years later as the local entity charged with overseeing the federal law through state and county agencies.

In fiscal year 2016 the National Oceanic and Atmospheric Administration allocated more than $2 million in Hawaii in support of coastal management activities aligned with federal and state program goals.

But rather than achieving the goals of conserving the coastal zone, government agencies have been granting “hardship variances” that allow oceanfront property owners threatened by erosion to build sea walls and other forms of shoreline armoring to protect their property, Fletcher said.

Hardship variances undercut the purpose of federal coastal zone management conservation policies, he said.

According to the study, the construction of initial sea walls destabilizes neighboring shorelines and triggers a domino effect of coastal hardening that condemns entire stretches of sandy beach to narrowing and eventual loss.

Part of the problem, the study said, is that shorelines are too often managed in piecemeal fashion, sea wall to sea wall, which leads to shortsighted decision-making that overlooks accumulated impacts and long-term trends.

What’s more, agency personnel with authority to decide on applications for coastal zone uses are not required to, and traditionally have not had, scientific training in the interpretation of potential impacts.

“In lieu of this, decisions are made on the basis of statements from consultants hired by the applicant — a situation that is ripe for conflict of interest,” the study said.

Despite substantial legal authority to protect beaches, appointed and elected officials have frequently approved hardship variances allowing sea wall construction, expansion of coastal homes and nonconforming buildings, and seaside development without regard to shoreline stability, according to the study.

The ongoing pattern of shoreline hardening and beach degradation seemed to escape notice until the research caught up with the problem in the last couple of decades, said Brad Romine, coastal management specialist with Hawaii Sea Grant and co-author of the study.

“Tracking cumulative impacts, as is required with the current environmental review process, must be a key part of the management doctrine in this case,” Romine said in a statement.

If authorities intend to protect existing beaches for future generations, Fletcher said, they must implement policies that allow beaches to migrate landward with rising seas.

“This is not about being hard on people, being hard on agencies; this is about being hard on the problem,” he said.

The paper’s lead author is Alisha Summers, who was a UH undergraduate student while conducting the work. The study was funded by the H.K.L. Castle Foundation, the state Department of Land and Natural Resources, the Hawaii Coastal Zone Management Program and the Honolulu Office of Climate Change, Sustainability and Resiliency.