Surrounded by waterfall-drenched mountains, private homes standing on the soft sands of Hanalei’s shimmering half-moon bay represent wealth — and risk.

In mid-April, risk became reality when an overnight storm produced the most rainfall recorded during a 24-hour period in U.S. history. All that water unleashed landslides, dissolved roads into massive sinkholes and damaged nearly 350 homes on Kauai.

On the makai side of Weke Road, several multimillion-dollar homes overlooking Hanalei Bay were reduced to buckled wrecks. Highly visible, they are symbols of the area’s always significant flood danger — and focal points of the debate over allowing development in hazardous areas.

Last week, Gov. David Ige requested a federal disaster declaration, saying the destruction required a level of response beyond the capabilities of the state and local governments.

“There are two camps at the county,” said Andrew Hood, a Honolulu-based groundwater hydrologist with extensive knowledge of the Hanalei floodplain. “One is, ‘Let’s rebuild and get stuff going as fast as we can,’ and the other is, ‘Let’s slow down and take the steps to figure out how we can look at the information about this event and better use it for wise use planning.’ I really can’t say what’s going to happen.”

Past Practices

Kauai has historically allowed development in areas next to coastlines and rivers vulnerable to flooding. But in recent years this laissez-faire approach has become more stringent as scientific research related to climate change has prompted the adoption of new building and zoning requirements.

Those who wish to rebuild homes destroyed by the flood will have to comply with newer standards.

Owners of homes located within the floodway of the Hanalei River, for example, will not be allowed to rebuild in place, said Kaaina Hull, deputy planning director for Kauai County. Homes located within the wider floodplain may have to build up higher than before.

“I think it’s up to policymakers to make rules and laws that protect us from ourselves.” — Makaala Kaaumoana

Some of the flood-ravaged houses on Weke Road were built prior to the adoption of a county shoreline ordinance in 2005 that requires structures to be set back 60 feet from the highest wash of the waves.

“Some of those houses on Weke Road, they can’t rebuild where they are right now,” Hull said. “New regulations recognize that some of these homes are in hazard areas and now impose requirements that ensure that these structures are not completely destroyed in the future.”

County planners have also been discussing whether the flood risk in some coastal neighborhoods needs to be reassessed.

Hull said Friday he does not know if any of the Weke Road homeowners are seeking to rebuild. None of them could be reached for comment.

It’s still unclear which homes would be allowed to rebuild in place under the county’s newer standards. Even if some homes meet the current requirements, some experts and officials are wary of allowing residents to rebuild.

“We just witnessed the power of the Hanalei River and other streams in the watershed,” said Ruby Pap, coastal land use extension agent for the University of Hawaii Sea Grant Program. “I believe this is reason enough to think twice before rebuilding in place.”

“Some homeowners may be willing to take the risk because they have the means to do so and they love where they are,” Pap said. “A couple of those homes along Weke not only lost homes, but lost property — there are giant holes where their properties used to be that are now filled with ocean water. So if they were to rebuild in place they would have to restore the land, then rebuild.”

Kauai County Council members Mason Chock and JoAnn Yukimura said they are exploring new policies to better protect homeowners.

“I would love it if the homeowners there on Weke Road were interested in selling the property to the county,” said Yukimura, who is campaigning for mayor. “Even if they have unlimited money, it doesn’t make sense to rebuild there.”

Makaala Kaaumoana, executive director of the nonprofit Hanalei Watershed Hui, said she hopes the flood has engendered the political will necessary to reduce the number of structures in hazardous locations.

“My concern is when one homeowner’s behavior is putting others at risk,” Kaaumoana said. “But we all know that in Poipu, after hurricanes Iwa and Iniki, they wanted to build right back where they were. That’s what humans do. I think it’s up to policymakers to make rules and laws that protect us from ourselves.”

Epic Rainfall

In ancient Hawaii, the soaking rains of Hanalei were revered for their duration, intricate falling patterns and variations in intensity. On the night of April 14 and the morning of April 15, their modern-day power was on full display in an extraordinary storm that weather forecasters did not see coming.

The soil in Hanalei was saturated even before 4 feet of rain began falling. Heavy rainstorms in previous days had undermined the soil’s ability to absorb the new rainfall.

At one point in the night, Hanalei received 5.5 inches of water in an hour, according to Hood, the hydrologist who is working on a forensic analysis of the flood.

“As a hydrologist, I will tell you I never thought I would live to see this much rainfall falling across one place in such a short period of time,” Hood said.

Surprisingly, rainfall totals were higher near the coast than inland where average rainfall tends to be greater.

A rain gauge at Waipa measured 49.7 inches of rainfall — a new national record — in 24 hours. On Mount Waialeale, the wettest place in the country on average, a U.S. Geological Survey rain gauge located at 5,150 feet above sea level measured 9 inches of rain for the same period.

Historically, the primary source of flooding in Hanalei is the Hanalei River. It drains Mount Waialeale, which has an astonishing average annual rainfall total of 394 inches.

But the primary source of the April flood was rain that fell directly on Hanalei town. That, combined with the swelling river, produced fast-moving rapids that ripped several North Shore homes off their foundations.

“The question of where we build and whether it’s wise to build in a certain place is all premised on a constant climate, and we don’t have a constant climate anymore.” — UH geology professor Thomas Giambelluca

“It’s a nice flat place to build everything and put in your crops, but that whole valley was formed by periodic flooding,” said Chuck Blay, a geoscientist on Kauai. “The whole town is in the floodplain. So it shouldn’t be totally surprising that the flood plain would flood. You might see that level of flooding once or twice in your lifetime, but on a larger scale that level of flooding in Hanalei Valley is pretty frequent.”

It’s impossible to definitively determine whether climate change contributed to the storm.

In Hawaii, the influence of climate change on rainfall is still being studied. But research suggests that the islands could start to experience fewer but more intense storms, said Thomas Giambelluca, a professor of geography at the University of Hawaii Manoa.

One thing is certain, though. The historical climate information that is the basis for determining flood risk and building requirements is no longer valid, Giambelluca said.

“The question of where we build and whether it’s wise to build in a certain place is all premised on a constant climate, and we don’t have a constant climate anymore,” Giambelluca said. “It is not relevant to look to the past to predict the future because we can’t assume that the future will be anything like the past. We need to add a much bigger margin of safety because the game has changed completely.”

‘We Should Not Build In Harm’s Way’

When disaster strikes, the desire to return to normalcy can make it difficult to think beyond the status quo.

“If there’s no structure there, that’s sometimes the best defense” of setting new restrictions, said Eric Simmons, an engineer for the Federal Emergency Management Agency. “Now we’re also talking the issues of property rights and cost, so while it may be the best defense, it may not be the easiest solution.”

Governments tasked with regulating post-disaster construction often face criticism, especially if the public perceives that regulations are infringing on individual property rights. On the other hand, the burden of funding a residential rebuild in a danger zone often falls to taxpayers, and taxpayer-subsidized flood insurance may cover the risk of future disaster.

Gregor Blackburn, a branch chief focused on floodplain management and insurance at FEMA’s regional office in Oakland, California, said residents facing a massive rebuilding project on the heels of disaster should think hard about what they want their community to look like.

“National disasters ruin a lot of things and economies can be one of them,” Blackburn said. “We at FEMA encourage in all communities that when coming up from the depths of a disaster like this, rebuild with an eye toward future resiliency and with an eye toward future avoidance of harm. These are locally driven decisions. Some may be harder than others, especially if you’re going to restrict somebody’s ability to build on their land that is maybe too close to a flooding source.”

Bradley Romine, a coastal geologist with the UH Sea Grant College Program, is heading up a team that’s drafting post-disaster reconstruction guidelines for the state’s counties to follow after future destructive storms.

“I understand there’s a need to get communities back up and running as soon as possible, get people back in their homes, back on their feet and get the economy working again,” Romine said. “But we’re hoping people will take a step back and consider how we can use disaster as an opportunity to redevelop smarter development that will be more resilient for future disasters.”

The study, focused mainly on sea level rise, is funded by the National Oceanic and Atmospheric Administration’s Coastal Resilience Grants program and is due out in April 2019.

Romine noted a series of guidelines and protocols for coastal storm reconstruction developed in 2016 by Sea Grant in cooperation with Maui County.

The first of its kind in Hawaii, the Maui report includes 70 recommendations for the county to consider when addressing the reconstruction and repair of buildings and homes damaged by a hurricane or major coastal storm.

Jim Buika, the Maui County shoreline planner and a former FEMA earthquake specialist, is working to incorporate the work into a draft county ordinance. 

“We should not build in harm’s way and we should move out of harm’s way when the things we already built in harm’s way get damaged,” Buika said. “But there’s politics in place and there’s economics involved. If these kind of policies aren’t on the books as law, it can be hard to implement them on the spot after a disaster occurs.”

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