June 18, 2021 | Source: Pacific Business News

Designing for Sea Level Rise

The king tides that are expected to arrive in the Islands next week will bring floods – what Hawaii may see as climate change affecting sea levels along the state’s coasts.

While king tides are not a direct result of climate change — they are caused by the moon being at its closest point to the Earth in its monthly orbit — the change in sea levels in recent years means higher tides and more flooding when they do occur.

The rates of sea level rise vary among the Islands in Hawaii, ranging from 0.6 inches (15.24 millimeters) per decade on Kauai and Oahu to 1.3 inches (33.02 mm) on Hawaii Island, according to the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information.

But the rate of sea level rise is accelerating and will rise across Hawaii by another one to three feet over the next 80 years, according to NOAA.

It’s something officials with the state and the counties are watching, as well as faculty at the University of Hawaii’s School of Architecture, Community Design Center, Sea Grant College, Department of Urban and Regional Planning, and University of Hawaii Economic Research Organization.

And it’s taken on greater frequency and urgency among Hawaii architects, who must peer into the future when designing buildings intended to last 50 years or more to determine whether those structures may be vulnerable to rising levels of saltwater, whether or not they are on the coast, and with it, potentially millions of dollars — or billions of dollars — in economic loss.

Bettina Mehnert, president and CEO of AHL, formally known as Architects Hawaii Ltd., told PBN that sea level rise “is a topic on every one of our projects –on everything we do.

“It is particularly impactful to us as an island state,” said Mehnert, who is also a member of the City and County of Honolulu’s Climate Change Commission. “Architecture is the conduit through which ideas and solutions for the future can flow – but it is a collaborative endeavor that needs the whole design ecosystem to succeed: Our government, our design community, the construction industry, as well as our community have an opportunity to work together.”

According to the state’s 2017 Hawaii Sea Level Rise Vulnerability and Adaptation Report, chronic flooding with sea level rise will increase over the next 30 to 70 years, which will impact homes and businesses near the coast, and in low-lying and infill areas such as parts of Kakaako. The report estimates an increase of one meter, or 3.2 feet, of sea level would affect some 6,500 structures and result in an estimated $19 billion in economic loss from chronic flooding of land and structures in the most vulnerable areas. That includes Waikiki, the industrial areas in Kakaako and around Honolulu Harbor, and the Daniel K. Inouye International Airport.

The state’s Climate Change Mitigation and Adaptation Commission’s data is available online on the state’s Hawaii Sea Level Rise Viewer tool, and shows, down to the tax map key level, how properties would be affected by sea level rises ranging from a half foot to 3.2 feet.

The commission three years ago adopted strategies that include supporting legislation for disclosure about potential sea level rise exposure for private and public properties. The Legislature this year started to take action with the passage of two bills currently sitting on Gov. David Ige’s desk that would require identifying state buildings in areas that could be impacted and notifying homebuyers whether their homes could be impacted by sea level rise.

Sea level rise has also become a major point of conversation within AIA Honolulu, the local chapter of the American Institute of Architects.

Architect Hale Takazawa set up the Design for Risk and Resilience Committee for AIA Honolulu two years ago at the request of group’s then-president, Joe Ferraro, who also asked him to reach out to people beyond the architecture community.

The response was overwhelming, and today, the committee is up to some 70 members, who include architects, engineers, people from the City and County of Honolulu, the state and the University of Hawaii, who conduct online discussions using the Basecamp application.

“It just exploded once we were able to open it up, outside of the architects, because sea level rise issues stem far beyond architecture, to every corner of our economy,” Takazawa said. “It took about a year for us to wrap our heads around what the real problems are and where the real risks are and it’s basically where no one’s looking.”

He noted that as rainfall increases, there is higher flooding potential and the groundwater rises.

“The first thing that groundwater hits is our plumbing,” which is an expensive fix — a potential problem that could dwarf the $12.4 billion cost to build the Honolulu rail project, he said. Oahu’s sewer and wastewater system is also vulnerable and presents a sanitation risk, he said.

“We look at risk and then we try and figure out how do we mitigate or how do we handle these things,” he said. “What solutions can we start to come up with to take care of these things?”

Katie MacNeil, a principal at G70, said architects and engineers are looking at design solutions for mitigating hazards such as water inundation from rain or flooding.

For commercial buildings, that could mean adjustments to the square footage used on higher floors for relocating equipment that is currently on a floor that might be prone to flooding, she said.

“Look at how the function and uses could be changed, taking higher value areas and moving them to higher ground, so to speak, or putting in mitigation elements [such as] flood protection at entryways, so that if there’s going to be king tides or things of that nature, that they could put up barriers, much like a homeowner would put up sandbags,” she said.

Architects at Mason are also looking at the critical infrastructure in buildings they work on, from new construction to historic structures in Downtown Honolulu that may be vulnerable to increased flooding, said Melanie Islam, a principal and the firm’s sustainability director who is also a member of the AIA committee as well as its board of directors.

“When we are talking about work in the downtown area there is opportunity to modernize the building and really rethink its components,” she said. “A lot of the talk about the tides and sea level rise and resiliency is where your critical infrastructure’s located.”

That equipment right now is in a basement or on the ground floor of a building, she noted.

“A lot of the thought that’s going on in many of the coastal cities is bringing them up to the mid-rise level where they can still be functional,” she said, when the ocean level rises. “Those kind of conversations and thinking are where we’re interjecting when they come up.”

The topic can come up even before a design is conceptualized.

Planners and engineers who prepare environmental assessments and environmental impact statements must look at sea level rise, assessments and all available information to “see what the impacts would be on … an existing development or a vacant property and examine where will sea level rise be and to design to that standard,” said Tracy Camuso, an associate principal planner at G70.

“In our disclosure documents that we write for the state and the city to entitle these projects, there’s a section on climate change and sea level rise, and so we are up front, they’re saying, this is where the project is, these are what the impacts are expected to be and these are the mitigation measures we’re proposing,” she said. “It’s a little different from the architecture side because they’re thinking about it more in a built type of way; we’re thinking about it in an overall planning context.”

Architects also need to “be smart in site planning, building orientation, building design, and selection of correct materials for these conditions,” Mehnert said.

“For example, for one of our clients we are currently exploring best design practices to effectively safeguard existing critical infrastructure,” she said. “This includes everything from onsite storm drainage and sewer systems to emergency generator sizes and locations in our hospitals.”

It also includes looking at future resiliency and operations, which includes designing ground floors that are on “columns, plinths, or mounds that are well above anticipated sea level.”

For example, AHL recently designed a new science and math building, currently under construction, at Brigham Young University–Hawaii that was raised three-and-a-half feet off the ground on a plinth, or base, because that part of the campus had already been subject to severe flooding.

Locations of projects are “becoming more and more important” for owners to preserve their assets, Mehnert said.

“Where constraints limit the placement of buildings within possible areas of flooding, we raise habitable spaces to be above anticipated sea level rise elevations,” she said. “We also consider what materials are used that can withstand ocean forces, hold up to climatic conditions, and ones that can be sacrificed during high water and flooding events.”

Managing rainfall, along with high tides, is part of that, MacNeil said.

“Flooding can really be problematic,” she said. “We want to have on our site a robust management system in place for rainwater. That’s what we call low impact development, and it involves a reduction of hard surfaces that we call impermeable surfaces.”

Some of the design features used to address that include using permeable pavement, landscaped areas or water retention built into a storm drainage system. That would also help if a hurricane were to strike Hawaii.

“But if you’re building new, you would try to limit, or avoid, development in the flood-prone areas, that would be step one,” MacNeil said. “Those that would be features of resiliency.

“It becomes a business decision, as well as alignment with mission, and life-cycle costs,” she said. “Looking at a long-term perspective is that it would be an investment now that pays off in the long term.”

One radical solution Takazawa is talking about would be to take buildings off the municipal infrastructure grid, including the sewage system, which could become inoperable in the future if groundwater levels rise.

“The idea is, what if we took the entire city and tried to unplug it,” Takazawa said. “What that would mean is that each building, or small communities of buildings, would be completely unplugged from the existing infrastructure that we have because existing infrastructure will be flooded, and we won’t be able to use it very well, or we’ll be spending so much money it will be almost unaffordable.”

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