Hawaii DOT Studies Potential Flooding Impact on Infrastructure

The Hawaii Department of Transportation is looking at a range of studies that examine how the potential for sea level rise (SLR) due to climate change could impact transportation infrastructure. 

The most recent study, published in March of 2020 examined how direct marine inundation – which is when sea water levels rising above the current land levels – could affect Hawaii’s infrastructure but also at the impact of groundwater inundation, known as GWI.

GWI describes flooding that occurs as groundwater is lifted above the elevation of the ground surface and buried infrastructure; a difficult flooding type to manage since groundwater flooding cannot be stopped by coastal barriers such as sea walls. 

That study – conducted by researchers at the University of Hawaii at Mānoa School of Ocean and Earth Science and Technology – predicts that sea level rise will likely cause large percentages of Hawaiian land area to be impacted GWI, with Shellie Habel, lead author of the study, noting that the results “highlight the need to readjust our thinking regarding the flooding that accompanies sea level rise.”

Ed Sniffen, Hawaii DOT’s deputy director for highways and chair of AASHTO’s Committee on Transportation System Security and Resilience, estimated in a previous report that it would cost around $15 billion to protect all of the state’s coastal highways from the rising seas. The figure assumed $7.5 million for every mile of road that will need to escape erosion in the next 50 to 100 years and $40 million for every mile of bridge.

The agency began a vulnerability study in December 2019 to develop a comprehensive inventory of “potential extreme weather impacts” to Hawaii’s highway system; impacts that include GWI, SLR, and other natural disasters such as rockfalls and landslides.

Photo courtesy of Hawaii DOT

That’s in addition to a statewide assessment of SLR impacts conducted in 2017, which resulted in the Hawaii Sea Level Rise Vulnerability and Adaptation Report. That report predicted a 3.2-foot rise in global sea levels by 2100, one that could be reached as early as year 2060 under more recently published scenarios. Chronic flooding with 3.2 feet of SLR could result in approximately 25,800 acres of land in the Hawaii unusable, with roughly 34 percent of that potentially lost land containing a large amount of highway infrastructure in Maui, Oahu, and Kauai alone.

Currently, over 38 miles of major roads could be chronically flooded across the Hawaiian Islands, ranging from residential roads to sections of coastal highways such as Kamehameha Highway on Oahu. 

And much of that flooding could be from GWI rather than just direct marine inundation, thus not stoppable by traditional sea walls, which is why the Hawaii DOT is looking closely at creative engineering mitigation strategies for all flooding mechanisms for highways and bridge foundations.

Part of the agency’s flood mitigation planning is based on a study conducted for the Hawaii DOT by the University of Hawaii – called State Coastal Highway Program Report – released in August 2019. That report uses a new, detailed formula developed by the university to rank nearshore roads in order of urgency. Most of its suggested mitigation efforts focus on either “hardening” the roads and bridges or relocating them all together to higher ground. 

As a result, for the next two decades or so, the Hawaii DOT plans to strengthen and maintain the roadways as they are in place. For the future, it is also looking at elevating roadways and even relocating highways further inland and tunneling through parts of mountains to make that happen.  For instance, elevating the highway on Oahu’s Windward side could involve raising the road as high as nine feet. An alternative solution would be to relocate the highway further inland which would likely include tunneling through parts of the Koolau mountains at greater cost, the agency noted.

Webinar Series Focuses on Community Outreach Techniques

A webinar series sponsored by Smart Growth America is examining virtual public engagement practices for community outreach, examining a range of online platforms, as well as email and social media, as means of public involvement on projects and programs.

The group is holding three webinars on the subject, the first of which was held on April 28 and is now available via recording. The next two webinars are in June and cover:

“Online engagement might not be the best platform for every community to engage every citizen on every topic,” Smart Growth America noted. “But necessity is often the mother of invention and the need to stay home has exposed inequities and fostered innovations that have started many community leaders thinking about new and better ways to achieve wider and more meaningful representation in public decision-making.” For more information, registration, and recordings, click here.

Environmental News Highlights – May 27, 2020

A roundup of headlines curated for state transportation environmental professionals


Outdoor Industry groups call on Congress to invest in outdoor recreation infrastructure KSL

Virginia, Maryland, D.C. to sue EPA over failure to enforce pollution reduction targets in Chesapeake Bay – Virginia Mercury

EPA Clean Air Panel Chair Dismisses His Oil Industry Ties, Slams Harvard Study on Air Pollution and COVID Risks – DESMOG

Trump’s EPA must strengthen standards for deadly particle pollution – The Hill (Opinion)

AG opposes federal effort to scale back environmental regulations by replacing WOTUS rule – WNEM

Federal appeals court rules on ‘Good Neighbor’ provision of Clean Air Act – Jurist.org

A Stimulus Proposal Emerges From The Ashes With GOP Support: Infrastructure Spending – Forbes


Carbon emissions dropped 17 percent globally amid coronavirus – NBC News

Minnesota, other states sue EPA for ‘blanket waiver’ as nation fights pandemicStarTribune

Coronavirus is reshaping urban mobility – Axios


Groups Propose Tweaks to FEMA Infrastructure Resilience Guidance – Transport Topics

Disaster-heavy year risks a FEMA ‘code red’ for hurricane season – Virgin Islands Daily News

Bill Would Direct $50M Annually for Clean Energy to Low-Income Areas – NJ Spotlight

SunZia offers to move project out of White Sands – Albuquerque Journal


Texas’ Air Quality Improved During The Stay-At-Home Order. Here’s Why It Probably Won’t Last Houston Public Media

Pollution case against U.S. Steel dismissed – Pittsburgh Post-Gazette (subscription required)


Op-Ed: Coronavirus Crisis Demands Environmental-Justice Response – NJ Spotlight (Opinion)

Op-ed: Environmental Justice Task Force reveals first draft definition Washington State Wire (Opinion)

Report says removing state energy mandates would save consumers money – Bakersfield.com


Guest opinion: It’s not a food fight, it’s a water fight – Naples Daily News (Opinion)

Tree Deaths in Urban Settings Are Linked to Leaks from Natural Gas Pipelines Below Streets – InsideClimate News

Ripple Effect: When politics ignores science, it jeopardizes local clean water – The Hill (Opinion)

Loss of Louisiana marshes that protect New Orleans is ‘probably inevitable,’ study findsWashington Post (subscription required)


UO archaeologists help keep state road projects moving – University of Oregon


Transit Is Being Drawn to an On-Demand Model in Kansas – Government Technology

Want to buy a bike? Get ready for a long wait thanks to the coronavirus pandemic – Changing America

CDC Issues Tools To Guide Reopening Of Schools, Businesses, Transit – NPR

As recycling rate drops, California should embrace innovative recycling technologies – CalMatters (Commentary)

Safe Transportation for Every Pedestrian (STEP)FHWA Center for Accelerating Innovation


Data sharing presents major opportunities for transportation – National Academies

TRB Webinar: How Much Will COVID-19 Affect Travel Behavior? – TRB

TRB Webinar: Transportation Experiences and Next Steps in the COVID-19 Pandemic – TRB

TRB Webinar: A Research Roadmap for Transportation and Public Health – TRB

TRB Webinar: Forecasting Zero Emission Vehicles Fleet Scenarios & Emissions Implications – TRB

Review of California Wildfire Evacuations from 2017 to 2019 – University of California (Report)


EPA Guidance; Administrative Procedures for Issuance and Public Petitions – EPA (Proposed Rule)

Environmental Impact Statements; Notice of Availability – EPA (Notice)

Request for Nominations for the 2020 Clean Air Excellence Awards Program – EPA (Notice)

Agency Information Collection Activities; Proposed Collection; Comment Request; Requirements for Generators, Transporters, and Waste Management Facilities Under the RCRA Hazardous Waste Manifest System – EPA (Notice)

Proposed Fourth Renewed Memorandum of Understanding (MOU) Assigning Certain Federal Environmental Responsibilities to the State of Utah, Including National Environmental Policy Act (NEPA) Authority for Certain Categorical Exclusions (CEs) – FHWA (Notice of proposed MOU and request for comments)

National Register of Historic Places; Notification of Pending Nominations and Related Actions – National Park Service (Notice)