Waikīkī is at risk of sewage-contaminated flooding as sea levels continue to rise, according to a new study from the University of Hawaiʻi at Mānoa.
“The drainage infrastructure in Waikīkī is already failing,” said Kayla Yamamoto, a climate modeling analyst at UH Mānoa and co-author of the study.
She said the research revealed that rising sea levels will cause storm drains to become pathways for contaminated water from the Ala Wai Canal to backwash into low-lying streets and sidewalks in Waikīkī.
“In one of the storms we looked at in our study, we found that about 90% of the drainage inlets were overwhelmed during the storm,” Yamamoto said. “So this is not a future problem, it's a current problem, and it'll only get worse with sea level rise.”
The team used a flood model that tracks multiple sources of flooding including rain, tides, underground water behavior and storm drains. The goal was to create a comprehensive, large-scale map of what flooding hazards are the biggest threat.
The study said that tidal movement is becoming more of a flood threat in Waikīkī, rather than mainly being prompted by heavy rainfall.
“Our results show that contaminated flooding will become more frequent, more extensive, and eventually a daily occurrence rather than a storm-driven one,” Yamamoto said. “There are currently no effective management strategies in place to address this.”
Researchers believe that as sea levels rise, the backwash of contaminated water will still happen even without heavy rainfall. The study emphasized the importance of integrating water-quality issues and the possibility of drainage failure into flood management planning going forward.
