Using future, not just historical data projections could make state, local infrastructure designs more resilient

Coastal communities may be underwater sooner than we think. Research released earlier this year warns that the Petermann Glacier in Greenland is melting faster than expected. And while Greenland is more than 2,000 miles away from the U.S., the glacier’s melting could potentially double present sea level rise projections. 

Current models show that coastal hazards such as shoreline erosion, flooding and the destruction of shoreline structures “are going to increase at a much more rapid pace than initially anticipated,” said Staley Prom, a senior legal associate of the Surfrider Foundation, a nonprofit that advocates for the protection of coastal environments. That’s why “it’s essential that coastal development be built to the most protective standards and keep up with current science.”

In fact, a 2022 analysis from the research nonprofit Climate Central estimates that sea level rise could land 4.4 million acres of coastal U.S. counties partially underwater by 2050, putting at least $108 billion of assessed value at risk by 2100. 

To get ahead of future sea level rise threats, one county in Hawaii is weaving together data and legislation. Kauai County unanimously approved a bill in October 2022 that requires buildings constructed in an at-risk area of the island, known as the sea level rise constraint district, to be “elevated two feet above the highest sea level rise flood elevation” based on projected estimates. 

The bill that establishes the constraint sea level rise district signifies the importance of preparing infrastructure to meet the needs of future climate demands, said Alan Clinton, administrative planning officer at the county’s Planning Department.

As the oldest of the populated Hawaiian islands, many of Kauai’s “coastal areas have been developed on sand and not bedrock, so we have a lot of eroding shorelines,” Clinton said. That erosion is exacerbated by sea level rise, compounding Kauai’s vulnerability to high waves and passive flooding, which includes flooding caused by overflowing storm drains or rising groundwater tables.

“We realize the creep of sea level rise is going to continue to pose challenges,” he said. In fact, the Planning Department team partnered with the University of Hawaii Manoa School of Ocean and Earth Science Technology to develop computer models for the legislation. The Sea Level Rise Constraint District Viewer visualizes projected wave run up and passive flooding until 2100, Clinton said, which policymakers and developers can leverage to inform coastal erosion mitigation plans. 

Kauai officials hope to encourage other state and local governments to take environmental models into account in building and construction projects, Clinton said, rather than just historic data. “We have all this data about the future, why are we not constructing our built environment in a manner consistent with what we are expecting to see?” 

The county’s legislation is based on a similar initiative in Boston. In 2019, its Planning and Development Agency developed and adopted Coastal Flood Resilience Design Guidelines to inform construction projects in the geographic areas and zoning districts the city designated as the coastal flood resilience overlay district. For at-risk buildings, the flood resilience guidelines encourage developers to “identify future coastal flood risk,” which can be assessed using the department’s Zoning Viewer. Like Kauai’s viewer, the zoning map shows where flooding with 40 inches of sea level rise is projected to occur during a major coastal storm, known as “a 1% chance storm event,” between 2070 and 2100, according to the BPDA site.

Kauai’s sea level policy is a step in the right direction, Prom said, adding that coastal states should continue “being proactive and increasing the resilience of their communities and coastlines.” For instance, state and local governments should reform zoning policies to include sea level rise vulnerability assessments that consider future projections. 

Indeed, the California Legislature in 2021 introduced a bill that would require state agencies to take sea level rise projections into account when planning, designing or maintaining state infrastructure within a coastal zone. Had it passed, the bill would have also required agencies to conduct a sea level rise analysis before approving public funds for a new or expanded infrastructure project along the coast. 

In Oregon, the state’s Department of Land Conservation and Development and the Oregon Coastal Management Program released a planning guide late last year to support state and local planners’ efforts to assess sea level rise and craft policies and building codes to mitigate its effects. The guide points to the program’s Sea Level Rise Impact Explorer mapping tool, which offers estimates of sea water inundation and coastal erosion 30 to 50 years in the future. 

Building infrastructure that’s resilient to future sea level rise sets communities up for long-term success, Prom said. Other methods of sea level rise mitigation, such as fortifying beaches with coastal armoring, can weaken shoreline integrity and worsen the effects of erosion and flooding. 

It’s critical for state and local governments, Prom said, “to always use the best available scientific estimates and understand that climate change and sea level rise is happening much more quickly than anticipated.”