THURSDAY, SEPTEMBER 20, 2018
Western Japanese Floods
8/21/2018 5:00:00 PM
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Update 18/21/2018 5:00:00 PM 
First Posting 7/12/2018 5:00:00 PM 
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Posting Date: 8/21/2018 5:00:00 PM

AIR Worldwide estimates that industry insured losses from the flooding in western Japan caused by excessive rainfall from June 28 to July 8, 2018, will be between JPY 284 billion (USD 2.6 billion) and JPY 423 billion (USD 4.0 billion).

ALERTTM subscribers can download Touchstone®, CATRADER®, and Touchstone Re event sets; loss-based similar stochastic events (SSEs); and a flood inundation depth shapefile, with documentation, for the event.

AIR’s loss estimates explicitly capture residential, commercial, industrial, automobile, and agricultural/mutual losses from inland flood both on and off the floodplain based on a larger ensemble of simulated event scenarios that reflect uncertainty in precipitation observations, modeled flows, and levee failures. These loss estimates were derived based on AIR’s high-resolution Industry Exposure Database (IED) for Japan and inundation depths modeled using the event-based probabilistic AIR Inland Flood Model for Japan. AIR’s loss estimates and flood footprint reflect all affected prefectures in western and south-central Japan but do not include Hokkaido Prefecture in the north, which experienced less than 1% of the total impact.  

The range in AIR’s loss estimates also reflects uncertainty in the payment of damage to buildings, damage to contents, and extra expenses. Please note that total economic losses are expected to be higher than industry insured loss estimates.

The modeled hazard intensities reflect the maximum estimated river flows and maximum precipitation intensities during the event from June 28 to July 8, 2018. Note that many reinsurance contracts are subject to an hours clause (typically 168 hours for flood events). Given the duration and the high proportion of non-typhoon rainfall associated with this event, AIR expects this flood to be treated as a single occurrence of non-typhoon precipitation-induced flooding event.

See below for additional information on what AIR’s loss estimates capture.

AIR’s modeled insured loss estimates include:

  • Insured damage to property (residential, commercial, industrial, and agricultural/mutual), both structures and their contents, and automobile

AIR’s modeled insured loss estimates do not include:

  • Landslide
  • Losses to land
  • Losses to infrastructure
  • Losses to CAR/EAR, marine hull, or marine cargo lines of business
  • Business interruption losses
  • Loss adjustment expenses
  • Demand surge—the increase in costs of materials, services, and labor due to increased demand following a catastrophic event; demand surge can be applied by AIR software users who want to account for this variable

Western Japan Floods Recap

Following successive heavy downpours from June 28 onward, several days of record-breaking rainfall until July 8 led to widespread inland flooding in more than 30 prefectures across western and south-central Japan. The precipitation was described by an official at the Japan Meteorological Agency (JMA) as being “at a level we have never experienced.” As well as numerous rivers and streams bursting their banks, many landslides were reported. In addition to major damage to buildings and infrastructure, there was considerable business interruption. With at least 200 lives lost, this was Japan’s deadliest flood since 1982 and the country’s deadliest natural catastrophe since the 2011 Tohoku earthquake.

Meteorological Summary

The heavy precipitation began on June 28, much before the seasonal “Baiu” rain front that further interacted on July 4 with moisture from the remnants of Typhoon Prapiroon, which had dissipated over the Sea of Japan earlier that day. The front continued to drench the already saturated soils until July 8. The JMA issued Emergency Heavy Rain Warnings for Tottori, Okayama, Hiroshima, Fukuoka, Saga, Hyogo, Kyoto, and Nagasaki prefectures—a level of warning used only when an amount of rainfall not seen for decades is anticipated. 

kawabou_c-band_rader_japan_wide_2018-07-03to08.gif

An animated radar precipitation image for Japan from July 3 to 9, 2018. (Source:  Ministry of Land, Infrastructure, Transport and Tourism)

In just a few days, parts of Japan received four times the rainfall typically expected in the whole month of July, according to the JMA. Media reports state that new records for rainfall during 24-, 48-, or 72-hour periods were set in 93 locations. In Kochi Prefecture, for example, 1,190 mm (46.85 inches) of rain was reported in Umaji village in a 72-hour period, with the highest total from the World Meteorological Organization (WMO) being 1,852 mm (72.91 inches) recorded in Yanase. In Shikoku Island’s town of Motoyama, rain totals of nearly 1,694 mm (66.69 inches) fell throughout the event. JMA data indicates that 15 station gauges recorded at least 1,035 mm (40.75 inches) of rain falling between June 28 and July 8.

Numerous rivers in the impacted regions crested above their historic levels. Floodwaters reached as high as 5 meters (16.4 feet) above normal levels in some locations, and watercourses across the region overflowed. Several rivers such as the Asahi, Takahashi, Misasa, and Houman rivers near the cities of Okayama, Kurashiki, Hiroshima, and Fukuoka, respectively, experienced over 500-year return period flows. The Hijikawa River in Ehime Prefecture overflowed with an over 250-year return period flow. The rainfall abated on July 9 and water levels began to recede in some areas, but the threat of landslides remained and railroads and highways remained closed in affected regions, hindering relief and rescue operations.

Reported Damage and Disruption

More than 8 million people from 23 prefectures in western and central Japan were ordered to evacuate, with many thousands going to gymnasiums, schools, and other temporary shelters. In addition, 71,000 dwellings were set up as temporary housing, according to a statement made by Prime Minister Shinzo Abe during his visit to a shelter on July 11 in Okayama.

More than 46,000 residential buildings were destroyed, damaged, or inundated, according to data issued on August 8 by the Fire and Disaster Management Agency (FDMA). Many vehicles were swept away and large areas became choked with mud and debris.

Rail services across western and central Japan, among them the Shinkansen bullet train, were suspended because of debris on the rails or track being washed away. According to Japan's transport ministry, 27 railway lines experienced damage—mostly from landslides—at more than 100 locations. After its workers evacuated it on July 6, the Asahi Aluminium Industrial Company’s plant in Okayama exploded. Across the region roads, bridges, and other infrastructure were severely damaged or destroyed.

Thousands of homes lost electricity, many phone lines were downed, and roughly 270,000 homes lost their water supplies. There was widespread business interruption, particularly to auto and electronics manufacturers; impacted companies include Mazda, Panasonic, Daihatsu, and Mitsubishi. Production was suspended at several plants because of supply chain disruption, flood damage, or worker safety issues.

Western Japanese Floods
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