{"id":232696,"date":"2026-04-22T08:00:01","date_gmt":"2026-04-22T18:00:01","guid":{"rendered":"https:\/\/www.hawaii.edu\/news\/?p=232696"},"modified":"2026-04-21T13:45:52","modified_gmt":"2026-04-21T23:45:52","slug":"sewage-contaminated-flooding","status":"publish","type":"post","link":"https:\/\/www.hawaii.edu\/news\/2026\/04\/22\/sewage-contaminated-flooding\/","title":{"rendered":"Waikīkī faces escalating threat of sewage-contaminated flooding"},"content":{"rendered":"Reading time: <\/span> 3<\/span> minutes<\/span><\/span>
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Flooded streets in Waikīkī<\/span>. (Photo credit: David Muther)<\/figcaption><\/figure>\n

University of Hawaiʻi<\/span> at Mānoa<\/span> researchers revealed that Waikīkī<\/span> is facing a fundamental shift in flood hazards as sea levels rise—transitioning from a flooding that is driven primarily by rainfall to events increasingly dominated by tidal processes. The team identified two key pathways that will become more significant with sea-level rise, both of which will increase public exposure to sewage-contaminated waters. The study was published in Scientific Reports<\/em><\/a>.<\/p>\n

“Our findings make clear that current flood management strategies for Waikīkī<\/span> are incomplete,” said Kayla Yamamoto, climate modeling analyst at the Coastal Research Collaborative<\/a> in the 糖心视频<\/abbr> Mānoa<\/span> School of Ocean and Earth Science and Technology<\/a> (SOEST<\/abbr>). “Most planning focuses on surface damage and economic loss from storms, but largely ignores the contamination dimension. Our results show that contaminated flooding will become more frequent, more extensive, and eventually a daily occurrence rather than a storm-driven one. There are currently no effective management strategies in place to address this.”<\/p>\n

Simulating future scenarios<\/h2>\n

The team used an open-source, physics-based flood model to simulate how multiple flood sources interact in Waikīkī.<\/span> The team used an advanced flood model that, unlike previous models, integrates all sources of flooding—rain, tides, underground water behavior, and storm drains—to provide a single, complete view of the hazard<\/p>\n

“What we found is that during extreme rainfall like we\u2019ve been experiencing, high tides and elevated water levels in the Ala Wai can combine to create conditions where contaminated water flows back into low-lying streets and sidewalks,” said Shellie Habel, study co-author and coastal geologist with the Coastal Research Collaborative and Hawaiʻi<\/span> Sea Grant<\/a>. “As sea level rises, it will take less extreme rainfall and tides to cause similar flooding in the future.”<\/p>\n

The two key pathways they identified were: storm drain backflow, where polluted water from the Ala Wai Canal is forced into streets and public spaces in Waikīkī<\/span> through drainage systems, and groundwater emergence, which brings sewage and other contaminants from aging and leaking sewage infrastructure to the surface.<\/p>\n

The model simulations show that storm drain backflow is projected to occur even when there is no rainfall:<\/p>\n