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Rising seas impacting shores – and it will only get worse

6-foot rise possible by 2100; repercussions for the properties and beaches in the balance

University of Hawaii Sea Grant Program Coastal Geologist Tara Owens stands on a toppled kiawe tree as a set of waves hits the Olowalu  shoreline during high tide Wednesday. The wash of this wave reached the edge of nearby Honoapiilani Highway. — The Maui News / MATTHEW THAYER photo

Try picturing Maui if sea levels rise 3.2 feet.

Which roads, hotels, neighborhoods and critical infrastructure will be wiped from the map? How much worse will it be if king tides become a nearly everyday occurrence and major storms are not only more common, but more fierce?

According to Hawaii scientists, the bleak scenarios are not only possible, they are likely. To help landowners, policymakers and civil engineers envision the coastal impacts of rising seas, the State of Hawaii Sea Level Rise Viewer was developed.

With the online viewer, a person can pick an area of interest, be it the entire state, Maui or just a short stretch of coastline, to see how it will fare if sea level rises a modest half-foot, or all the way up to a catastrophic 3.2 feet. The viewer displays the impacts in a variety of ways, including sea level rise exposure area, high tide flooding, high wave flooding and potential economic loss.

Its projections are as sobering as they are educational. Long stretches of roadway will need to be elevated or realigned as seas rise. Millions of dollars of property damage will occur. The Kahului wastewater treatment plant, Kahului Airport’s runways and long swaths of developed coastline are among the areas in the ocean’s crosshairs, as are Waikiki and Kakaako on Oahu.

Waves splash onto an Olowalu stretch of Honoapiilani Highway on Wednesday. — The Maui News / MATTHEW THAYER photo

Dr. Chip Fletcher, University of Hawaii at Manoa associate dean and professor at the School of Ocean and Earth Science and Technology, says sea levels have been going up slowly for the past 100 years. Fueled by melting glaciers and the tripling of the Antarctic melt in the past five years, the rise and its impacts are gradually starting to accelerate. In the second half of this century, they are expected to take a big jump.

Fletcher says levels are expected to rise 3 to 8 inches by 2030. The National Oceanic and Atmospheric Administration predicts a 10 percent chance of 6 feet of rise by 2100. The UH professor says, on the current trajectory, Earth will see 22 feet of rise by 2200 and 30 feet by 2300.

“To sum it all up, we’re in a world of hurt,” Fletcher said by phone from Oahu last month. “By the end of this century we’re looking at 3 feet of sea level rise at a minimum and 4 to 5 feet most likely.”

He says the threats extend inland by way of groundwater inundation. As sea levels rise, so does the water table. Low-lying areas in Kihei, Wailuku and Kahului will become wetlands that flood even higher during king tides and big wave events.

Fletcher shares a story about how large waves hitting Maui’s north shores cause the level of a well in Kihei to rise and fall. He says this “pressure connection” of the island’s water table demonstrates how hardening a shoreline can “shoot you in the back.” Passive flooding will occur behind and under revetments. Seawalls designed to keep water out could end up being undermined or stopping floodwaters from draining.

Sand bags armor the shoreline in Kahana during an afternoon high tide earlier this month. In the background is the Hololani Resort, one of many West Maui shoreline condominiums that were built overlooking wide sandy beaches that have since dwindled and, in some cases, entirely disappeared. — The Maui News / MATTHEW THAYER photo

Warmer seas cause hurricanes to be bigger, wetter and slower. They also allow big storms to track farther north, thus making it more likely one will hit Maui. Warm water expands, causing locally higher sea levels and fueling king tides. He says the frequency of flooding is expected to quadruple to 200 days a year in the 2030s and ’40s.

If that wasn’t bad enough, the weight of Maui’s two shield volcanoes exacerbates sea level rise problems by bending the seafloor down. Fletcher calls it land subsidence. It means Maui may see greater impacts than other islands. It is already negatively impacting West Maui.

Amid the doom and gloom, there is some hope. The Sea Level Rise Viewer’s information serves as a tangible wake-up call, one that Maui County officials and departments have taken to heart. Departments across the board are currently doing vulnerability assessments to determine what facilities and infrastructure will be impacted and what can be done to mitigate or retreat from the threat.

On Monday, Maui County filed suit against 20 fossil fuel companies for the rising cost and impacts of climate change.

“Maui County taxpayers should not be left to bear the staggering costs of climate change impacts,” Maui County Mayor Michael Victorino said in a news release detailing the lawsuit. “We are seeking relief in state court to hold Big Oil companies accountable for their decadeslong disinformation campaign to keep the public in the dark over the climate crisis.”

DR. CHIP FLETCHER, ‘We’re in a world of hurt’

For the past 11 years, University of Hawaii Sea Grant Program Coastal Geologist Tara Owens has served as a liaison to Maui County. She not only works with individual departments as they develop policies and strategies, but also with coastal communities as they wrestle with the inevitable.

“There is a lot being done right now, including research projects, new policies being developed and considered and mitigation efforts,” Owens said.  “It’s important for the community to know that things are progressing. There has been a lot of progress in the past 10 years. The community sees the impacts, and they want to look ahead and see that things are different.”

Owens has been working with condominium associations in Honokowai and Kahana as they develop mitigation efforts, like beach nourishment and temporary sand bagging.

“Everybody is wrestling with the problem,” Owens said. “It’s very difficult for these property owners, and it’s very difficult for the county. The county planners are the ones holding the bag when it comes to making decisions and working with the state.

“We’re really in the first phases of seeing how sea level rise will affect our built environment. In Honokowai, you have a mile or more of coastline where properties are built right on the shoreline, and they have armored the shoreline. We now know that has significant consequences, including impact on neighboring properties and, eventually, compete loss of beach. Now, with rising seas, we’re starting to see those walls are failing. They are not a long-term solution.”

Pat Lindquist, president of Napili Bay and Beach Foundation, says the nonprofit organization hopes to restore the beach to stave off high tide and wave events that have torn away beach access stairs and reached buildings.

“It’s knocking at the door,” Lindquist said. “What we hope to do, and are working to do, is restore the beach. We have plenty of beach sand sitting right in our bay. We had the amount calculated and it matched what we lost. We definitely don’t want to encourage people building more seawalls or revetments.”

Down the coast, Kahana resident John Seebart has been volunteering for years to help neighbors understand their options and formulate plans to respond to coastal erosion and sea level rise. Beach nourishment and a series of seven groins have been proposed for Kahana. The groins are being evaluated through the environmental impact statement process.

“You’ve got people here who bought with no malintent whatsoever,” Seebart said. “They bought in good faith and now, essentially, they need to do something to save their property. These people are willing to pay. They would like any assistance they could get, but they’re willing to pay. It’s like they are groping in the dark. If the county says one thing and the state doesn’t like it, it doesn’t happen. It can be very frustrating.”

Seebart says coastal residents need hope.

“If you don’t help these people help themselves other properties are going to suffer in terms of value. If those properties did go into the water, that is the end of the revenue stream of those properties forever. On top of which, if the county and state would allow that to happen, the value of every shoreline property in Hawaii would fall apart.”

Seebart lives on the mauka side of narrow Lower Honoapiilani Road. A section of road collapsed near his house a while back and engineers shored up the stretch of coastline with a wall of massive sandbags. He says he is concerned about the bags’ impacts down the coast and would rather have seen stacked loose rocks as has been utilized nearby.

“They use these sandbags as though they are temporary, and that is probably true, but in the meantime it is a very hard structure. Loose rocks are actually softer.”

Fletcher and Owens are also against hardening shorelines. Saying it will be a losing battle if man tries to wage war against water, they envision a managed retreat.

“Beach nourishment, artificial reefs, groins and additional forms of engineering are being evaluated, but there are lots of concerns about their impacts and their costs,” Owens said. “People in the community are asking if that is the right thing to do.

“These are interim solutions that can help, but in the long run there is going to be no other choice but to figure out how to get out of the way,” Owens said. “How do we even begin as a community and a society to move out of the way? What is the exit strategy?”

The legal battles and financial ramifications are sure to be colossal when it comes to declaring buildings or neighborhoods unlivable. Who will pay to tear them down or provide land to relocate?

Both experts say shore hardening could spell the end of Hawaii’s beaches. They also say if the shifting sand is preserved and allowed to act as a natural buffer, it will absorb and adapt to the rising seas.

“Imagine if we really did get out of the way,” Owens said. “If you pulled up all the seawalls and moved all the infrastructure, beaches can recover.”

Fletcher says it comes down to what sort of world we want to leave for the generations to come.

“Courageous decisions will have to be made, ones that have severe impacts, but are made in the favor of the public trust,” Fletcher said. “I think beaches belong to our children. They belong to the babies. If we want those beaches in the future, we need to figure out a way to transition neighborhoods out of the way of sea level rise.”

* Matthew Thayer can be reached at thayer@maui.net. 

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Sea Level Rise

Resources and Happenings

• State of Hawaii Sea Level Rise Report / Hawaii Sea Level Rise Viewer. The peer-reviewed report was developed by Tetra Tech Inc. and the state Department of Land and Natural Resources, Office of Conservation and Coastal Lands. The viewer was developed by PacIOOS at the University of Hawaii School of Ocean and Earth Science and Technology through a collaborative project led by the University of Hawaii Sea Grant College Program in partnership with DLNR and the state Office of Planning. https://www.pacioos.hawaii.edu/shoreline/slr-hawaii/

• Beach fundraiser. A virtual 5K, Walk, Run, Paddle Fundraiser benefiting the Napili Bay and Beach Foundation’s Beach Restoration Fund is scheduled to be held Oct. 25. Walkers, runners and paddlers around the world are invited to participate in the foundation’s first virtual event. https://www.napilibayfoundation.org/walk-2-4-napili-beach.html

• Sea level rise presentation. West Maui Kumuwai is scheduled to host University of Hawaii Sea Grant Program Coastal Geologist Tara Owens for week three of its all-virtual Ridge to Reef Rendez-View October Science Speaker Series. Owens will be presenting, “The Climate Crisis is at Our Shores: How Rising Seas are Compelling Action in West Maui” in the Zoom event set for 5 to 6 p.m., Wednesday. https://www.westmauikumuwai.org/r2rr2020.html 

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