A dozen landslides shut down the lone road to the farthest reaches of Kauai’s North Shore during last weekend’s monster rainstorm, and Kuhio Highway remains closed between Waikoko and Wainiha.

On Friday officials set May 7 as the date by which one-lane access for emergency vehicles are expected to be restored along the full length of the road. But it’s hard to say when public road access will be restored.

On the heels of the record-setting storm that dumped 28 inches of rain in 24 hours, more than 446 people have been evacuated by helicopter from the areas hardest hit by flooding, crumbling cliff faces and sinkholes.

Non-emergency evacuations will continue through Saturday.

Meanwhile, disaster recovery crews are working to clear the highway of thousands of pounds of mud and debris.

“It’s quiet here now like it was 30 years ago,” said David Kuraoka, a ceramic artist stranded at his home in Haena, which is less than 10 miles from Hanalei but suddenly seems much farther away. “It’s a small place now because all the strangers are gone.”

On Thursday, Kauai police and county officials toured the portions of Kuhio Highway in Wainiha and Haena that were most severely damaged by landslides.

Courtesy of Kauai County

Ed Sniffen, deputy director of the Hawaii Department of Transportation, said Thursday he could not yet estimate when the road will be usable again.

He did provide some details of what the state plans to do, both in the short term to reopen the devastated highway all the way back to its famous finish line where the road meets the sea at Kee Beach, and in the long term to reroute it away from areas that will be hardest hit by the rising sea level due to global warming.

Rebuild, Then Relocate

As efforts to clear, stabilize and rebuild the road continue, Sniffen said the department will expedite a $33 million plan to reconstruct a series of narrow, low-weight bridges in Wainiha.

Initially slated to begin in 2019, the two-year project will replace Wainiha’s trio of historic one-lane bridges with concrete-based bridges.

The current bridges are actually temporary structures. Located at mile 6 near the mouth of the Wainiha Stream before it feeds into Wainiha Bay, they were erected after one of the previous bridges sustained permanent damage in 2004 and the other two were found structurally deficient in 2007.

Raging flood waters and landslides badly battered the northernmost portions of Kuhio Highway, carving up gravel and washing away entire sections of pavement.

Courtesy of David Kuraoka

Temporary bridges will be built side-by-side or up-and-over the Waiolo, Waikoko and Waipa bridges in order to accommodate heavy construction loads that the existing bridges may not be equipped to handle. These bridges, which will have a 25-ton load capacity, will also help expedite disaster recovery operations. The bridges currently in place are equipped to carry no more than eight tons.

Expediting the bridge rebuild, Sniffen said, is part of DOT’s short-term goal to reopen Kuhio Highway and make it as resilient as possible for the next 20 to 30 years. At that point, he said the road will need to be moved.

With the threat of sea level rise and coastal erosion increasing, the only way to ensure the historic highway’s long-term survival is to relocate it, Sniffen said.

“All options are on the table,” Sniffen said. “Tunneling, relocation to mauka of the slopes, cutting out a portion of the mountain — all of those options are being considered with the understanding that we have to consider the impact to the community and to the environment.”

Relocating the road — about 10 miles of pavement — is expected to cost upwards of a billion dollars, Sniffen said.

As for the immediate highway recovery efforts, Sniffen said DOT workers will use a combination of mesh wiring and concrete facing to stabilize the cliff slopes.

“In areas where we want to try and keep the slope as green as possible, we will put in a mesh on top that will hold the slope face in by not allowing the soil to erode but also allowing plantings to go through it,” Sniffen said.

“In other areas below the road where it’s not going to be as visible, or in areas where we need more strength, we will use concrete as the facing to protect the slope from being eroded. But with either method, we are going to anchor the slope in place.”

Always A Fragile Path

Kuhio Highway is the lone lifeline for Hanalei, Wainiha and Haena, communities nestled in the jungle on Kauai’s North Shore. Paved in the early 20th century, the highway follows the original dirt trail used by Hawaiians and 19th century travelers to access ancient fishing areas, taro patches and dry and wet cave systems.

The road is narrow, particularly where it hugs a series of steep sea cliffs threatened by erosion from heavy rainfall and rising seas. Although a series of century-old lava rock walls protect motorists along the road’s precipitous drop-offs, most of these rock walls are undermined by collapsing soil. For most of its length, the road has no guardrails and no shoulder.

Over the years, the highway has been struck by various natural disasters, prompting repairs, rebuilds and reroutes.

Another landslide on Kuhio Highway west of Hanalei Bay.

DLNR

In 1921, the Wainiha River cut a new channel during a storm, which forced the construction of a new bridge. An April Fool’s Day tsunami inundated the shoreline in 1946, decimating large spans of highway and sinking one side of the Waikoko Bridge. In 1967, the Lumahai Bridge collapsed into the river after being battered repeatedly by three tidal waves and a hurricane.

The road’s allure — hairpin curves and a precarious, cliffside perch — is also what makes it susceptible to environmental ruin.

The steep cliffs skirting the highway are composed of disintegrating lava rock, said geoscientist Chuck Blay. Kauai is the oldest of the main Hawaiian islands, and its rock surfaces are weather-worn and more susceptible to landslides.

“The island is pretty much geologically unstable,” said Blay, who lives on Kauai. “It’s really just one big pile of rotten rock. Most of it you could crumple up in your hand, it’s so soft.”

The sharp angle at which the road cuts into these vulnerable slopes and the North Shore’s wet climate further exacerbate the instability of these cliff sides, Blay said.

“In geology, landslides are called mass wasting,” he said. “That’s really what this is.”

This stretch of Kuhio Highway, particularly the segment along Waikoko Beach, has already been identified as a vulnerable road in the state’s forthcoming $15 billion plan to protect the state’s low-lying coastal highways from the effects of climate change — namely a rising ocean.

“We have roadways like this on every island,” Sniffen said. “On Maui, it’s Honoapiilani Highway that’s under threat of sea level rise in the future and shoreline erosion right now. On Oahu we have our North Shore roads on Kamehameha Highway, and we also have our Leeward coast where there’s only one way in and one way out.”

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