事后报告：2026年3月夏威夷洪水

Hawaii Flood-March 2026 March 9-22, 2026 Hawaii experienced a major flood and wind event driven by an intense multi-day Kona low stormpattern. Repeated rounds of heavy rain produced widespread totals of at least 5 to 10 inches acrossmost islands, with swaths of 15 to 25 inches over parts of Maui and Hawaii Island and localized 30+inch totals in upslope terrain. Honolulu broke a 24-hour rainfall record that had stood for 75 years.Due to the impact of catastrophic flooding, many roadways collapsed, residential homes were sweptinto rivers, and communities were cut off for days. The severe flooding phase that struck every majorisland in the chain has been described as the worst in the past two decades since the 2004 floodevent. Impacts and recovery information are still developing. Key headlines Hazard magnitude −Multi-day rainfall with island maxima of 49.57 inches on Maui and 38.77 inches on HawaiiIsland, plus damaging winds with locally extreme gusts at hurricane strength exceeding 135 mph. Impact signal −Widespread flooding and landslides, significant disruptions to power and transportation, andongoing damage assessment with early statewide economic loss estimates over $1 billion. Flood defense stress −Heightened concern around Wahiawa Dam on Oahu, including evacuation planning andclose monitoring of reservoir levels during peak rainfall. Wahiawa Dam Evacuation ZoneSource: Dam Inventory System, HawaiiDepartment of Land and Natural Resources Estimated total precipitation, March 9-22 (legend in inches)Source: National Weather Prediction Center and Guy Carpenter A business of Marsh McLennan Event Recap and Damage Impact Meteorological Discussion The March 2026 impacts were driven by 2 back-to-back Kona low systems rather than a single storm. The first Kona lowstalled northwest of the islands during roughly March 9 to 15, repeatedly pulling deep tropical moisture into the state andproducing multiple waves of torrential rainfall and embedded thunderstorms across the major islands, alongside damagingsouth to southwesterly winds. Just days later, a second Kona low arrived around March 19, bringing another round of heavy rain onto already saturatedwatersheds and elevated stream flows. This sequencing helped amplify runoff response and prolong flooding impacts,since the second wave occurred before soils, channels, and infrastructure systems had time to recover from the initialevent. The dual-system pattern with two major Kona lows within 10 days, is considered highly unusual by National WeatherService (NWS) meteorologists. Damage Summary Flooding and wind drove widespread disruption across the state. Reported impacts included numerous road closures fromflooding, debris, and landslides; overflowing streams and drainage channels; inundation of homes and businesses; swift-water rescues; rockfalls; and localized sinkholes and erosion issues. Cleanup needs were significant in some urbancorridors where debris and sediment accumulated in drainage features, and multiple public facilities required cleanupfollowing water intrusion. Agricultural impacts were also notable, including flooded fields, downed trees, damaged farmstructures, and operational disruptions. Power and emergency response impacts were substantial for this event. At the storm’s peak, more than 130,000 HawaiianElectric customers were without power, and by the afternoon of Sunday, March 22, more than 32,000 were still withoutelectricity as repair crews worked through restoration. Emergency services reported numerous calls for help in flood-impacted areas, and officials indicated that more than 350 people were pulled from hazardous conditions during the peakresponse period. Early statewide damage estimates communicated publicly were on the order of USD 1 billion acrosspublic and private infrastructure, with assessments ongoing. Source: NWS, FEMA, Hawaiian Electric, The State of Hawaii Department of Transportation, The State of Hawaii Department ofDefense, US Coast Guard and Guy Carpenter Flood Mitigation, Insurance and Climate Implication Dam Crisis and Community Rating System (CRS) Flood defense lens: this event underscores that flood risk is not only “water on streets,” but also the performance of flooddefenses and the effectiveness of emergency operations under extreme rainfall. During the peak period, the 120-year-oldWahiawa Dam in central Oahu drew focused attention, including evacuation order for 5,000 residents in downstream areasand close monitoring of reservoir levels. Practical resilience actions include real-time reservoir and stream monitoring withreliable telemetry, clear operational triggers for spillway releases and evacuation thresholds, downstream inundationmapping tied to operational scenarios, and well-practiced Emergency Action Plans with coordinated publiccommunications. Following this event, longer-term priorities will include targeted improvements to spillway capacity, outletworks reliability, debris management, and re