2018 Japan floods

2018 Japan floods
平成 30 年7月豪雨 (Heavy rain in July Heisei 30)
Kawabou C-band rader Japan wide 2018-07-03to08.gif
Radar animation of the event from 3–8 July nationwide; the animation starts with Typhoon Prapiroon affecting western areas of the country followed by successive rounds of heavy rain along the Meiyu front
Date28 June 2018 (2018-06-28) – 9 July 2018 (2018-07-09)
LocationJapan, primarily Shikoku and western Honshu
Death(s)225 fatalities, 13 missing
Property damage¥1.09 trillion (US$9.86 billion)

In late June through mid-July 2018, successive heavy downpours in southwestern Japan resulted in widespread, devastating floods and mudflows. The event is officially referred to as Heisei san-jū-nen shichi-gatsu gōu (平成30年7月豪雨, "Heavy rain of July, Heisei 30") by the Japan Meteorological Agency.[1] As of 20 July, 225 people were confirmed dead across 15 prefectures with a further 13 people reported missing.[2] More than 8 million people were advised or urged to evacuate across 23 prefectures.[3] It is the deadliest freshwater flood-related disaster in the country since the 1982 Nagasaki flood [ja] when 299 people died.[4]

Approximately 54,000 members of the Japan Self-Defense Forces, police and firefighters have been searching for the people trapped or injured in landslides and flooding triggered by the heavy rain, while the Japanese government has set up a liaison unit at the crisis management center of the prime minister's office to gather information.[5]


Ten-day rainfall summary of the event from 28 June to 8 July (in Japanese)
Rainfall accumulations reached to 1,852.5 mm in Umaji, Kōchi

On 28 June 2018, a seasonal Meiyu front extending west from a non-tropical low near Hokkaido became stationary over Japan. Multiple rounds of heavy rain occurred in the subsequent days, primarily in northern Kyushu.[6] On 3 July Typhoon Prapiroon brought heavy rains and winds to southwestern Japan.[7] The surge of moisture brought north by the typhoon interacted with and enhanced precipitation along the front in Kyushu, Shikoku, and western and central Honshu.[6] Enhanced rainfall extended as far west as Okinawa Prefecture.[8] Large swathes of these areas saw 10-day rainfall accumulations in excess of 400 mm (16 in).[6] Deadly floods began on 5 July, primarily in Kansai region which was struck by a deadly earthquake three weeks prior.[9] Accumulations peaked at 1,852.5 mm (72.93 in) in Shikoku.[6]

Multiple areas saw their greatest one-hour and three-day rainfall totals on record.[7] Some areas were hit by more than 1,000 mm (39 in) of rain, prompting the Japan Meteorological Agency (JMA) to issue emergency heavy rain warnings[note 1] for eight prefectures: Okayama, Hiroshima, Tottori, Fukuoka, Saga, Nagasaki, Hyogo, and Kyoto.[10][11] This marked the largest issuance of these warnings since their implementation. An official at the JMA described the event as "heavy rain at a level we've never experienced".[10]

The torrential rain triggered landslides and flash flooding, with water levels reaching 5 m (16 ft) in the worst hit areas.[11] Motoyama, Kōchi, saw 584 mm (23.0 in) of rain between 6 and 7 July.[12] One town in Kōchi measured 263 mm (10.4 in) of rain in two hours.[13] Mount Ontake observed its greatest three-day rainfall on record at 655.5 mm (25.81 in).[7] Although the Yura River remained within its banks in northern Kyoto Prefecture, an embankment built after Typhoon Tokage in 2004 prevented runoff from flowing into the river. This inadvertently led to flooding in Maizuru after the flood gate was closed.[14]

As the rain lessened on July 9, high temperatures reaching 30 °C (86 °F), coupled with some 11,200 households without electricity, raised concerns over heatstroke and unsafe drinking water.[15]

Hiroshima prefecture alone had 1,243 mudslides in 2018, which is more than the entire nation's total in an average year. Ehime had 419 in 2018, results were not broken down by month, but its inferred that most of these were during this major event.[16]


Death toll by prefecture as of 20 July 2018[17]

Throughout the affected areas at least 225 people died in various rain-related incidents,[2] primarily due to mudslides, landslides and vehicles being swept away by the flood waters.[18] Many of the dead had ignored evacuation orders, and chose to stay in their homes despite repeated warnings.[19] Police received numerous reports across the country of people trapped in homes buried by landslides, of people being swept away by swollen rivers, and from people trapped in cars. At least ten people were buried inside their homes in Higashihiroshima; rescuers were able to confirm seven survived but remained trapped as of 7 July.[20]

Fatalities and missing person reports by island and prefecture[17]
Island Prefecture Fatalities Missing
Honshū Gifu 1 0
Hyōgo 2 0
Hiroshima 113 N/A
Kyoto 5 0
Nara 1 0
Okayama 61 N/A
Shiga 1 0
Tottori 1 0
Yamaguchi 3 0
Kyūshū Fukuoka 2 0
Kagoshima 2 0
Miyazaki 1 0
Saga 2 0
Shikoku Ehime 26 N/A
Kōchi 3 0
Unspecified 0 13
Total 225 13


By 7 July no bullet trains were running west of Shin-Osaka Station and the West Japan Railway Company officials were uncertain when the trains would be running again.[21] The widespread cancellation of trains stranded numerous travelers; some bullet trains were utilized as temporary hotels.[20] Some automakers (Mitsubishi Motors & Mazda Motor) halted production as the rain and flooding disrupted the companies' supply chains and risked the safety of workers.[19] Other companies such as Daihatsu and Panasonic suspended operations at plants until debris was cleared and the water receded from the factories.[15] The Asahi Aluminium Industrial Company plant in Okayama exploded on July 6, after workers had evacuated during the flooding.[22]

Delivery companies Sagawa Express Co. and Yamato Transport Co, with cargo service Japan Freight Railway Co. reported that some of their shipments into and out of the affected areas have been either reduced or suspended. Regional supermarkets have also been affected, with outlets closed or hosting shortened service hours due to delivery delays and/or product shortages.[23]

Nationwide sustained tremendous damage; losses reached an estimated ¥1.09 trillion (US$9.86 billion). Damage to agriculture, forestry, and fishery industries reached ¥629 billion (US$5.69 billion). Losses to public infrastructure, including levees, railways, and roads, amounted to ¥465 billion (US$4.21 billion).[24]

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