Drone erosion monitoring and overtopping alerts for Hawaiʻi coastal highways

Coastal Highway Watch: Erosion Monitoring and Wave-Overtopping Thresholds for Hawaiʻi’s Most Vulnerable Highways

Stretches of Kamehameha Highway (Hauʻula, Kaʻaʻawa, Kualoa, Waimānalo) and Honoapiʻilani Highway near Olowalu top HDOT’s own list of coastal roads most at risk, and several are the only route through their communities. This project gives HDOT a living picture of those segments: repeat drone surveys of erosion toward the road edge, wave-runup modeling that defines the swell and tide combinations that put water on the road, and forecast-linked alerts so crews and closures can be planned days ahead. Updated erosion projections will show how many years each segment has left and inform choices among hybrid reefs, fishpond-based protection and relocation. The drone, pilots and calibrated wave and shoreline models are already in place, so each year’s funds are spent within that year. HDOT gets a one-page card per segment: years until the road edge, and the swell-and-tide combination that triggers overtopping. Appropriate to the University of Hawaiʻi (UOH 100), SOEST Climate Resilience Collaborative, in partnership with HDOT Highways Division. Estimated cost: $350,000 per year in FY28 and FY29. Geography: Oʻahu and Maui.