Tsunami Waves Overtop Daiichi's 5.7 m Seawall

Beginning at approximately 15:27 JST, tsunami waves reaching 13–15 m inundated the Fukushima Daiichi complex, overwhelming the site's 5.7 m seawall. The tsunami flooded the turbine buildings, seawater pump intakes, and—critically—the emergency diesel generator rooms located in the basement, knocking out all AC power to reactor cooling systems. Only Unit 6's air-cooled diesel generator survived, powering limited safety systems for Units 5 and 6.