Kuhio Highway, Kauai

The Wainiha landslide in April 2018 was triggered by record-breaking rainfall exceeding 40 inches in 24 hours on Kauai's North Shore, causing a massive debris flow from steep valley walls that buried sections of Kuhio Highway (Route 560) near Mile Marker 25 with boulders, mud, and trees, completely blocking the only road access to Wainiha Valley, Haena, and Kee Beach. This isolated over 300 residents and stranded tourists, severed emergency services, and halted tourism to popular sites like Na Pali Coast, with damages estimated at $180 million across 12 slide sites that made the highway impassable for months.​

Fixing it proved extremely challenging due to the remote, narrow terrain with single-lane bridges, sheer cliffs, and ongoing flood risks that prevented heavy equipment access, forcing helicopter lifts for debris removal and hand-scaling of unstable slopes. Crews faced repeated rain delays, cultural site protections (like Native Hawaiian burials), environmental regulations for the sensitive watershed, and logistical hurdles hauling material over winding roads from Lihue, stretching repairs into 2019 with phased single-lane convoys.​

Mitigation involved soil nails, shotcrete walls, drainage rerouting, and culvert upgrades similar to Hanalei Hills, but Wainiha's wetter microclimate and private land ownership complicated long-term monitoring and funding, relying on federal disaster aid amid Kauai's high slide recurrence.