Conference dates: Sunday, August 30 – Saturday, September 5, 2026 Main venue: Hiroshima International Conference Center (within Peace Memorial Park), and others Drafted: July 22, 2026 FOSS4G Hiroshima 2026 Local Organizing Committee (Draft for Disaster Prevention / BCP Discussion)
This document, prepared for FOSS4G Hiroshima 2026 (dates: August 30 – September 5, 2026; main venue: Hiroshima International Conference Center and others), identifies the "cancellation/interruption risks" anticipated given the characteristics of the host city Hiroshima and the timing of late August through early September, and organizes both preventive measures to avoid those risks and contingency plans in case they materialize.
Note: Starting May 29, Reiwa 8 (2026), the Japan Meteorological Agency (JMA) revised its disaster-prevention weather information for heavy rain, river flooding, landslides, and storm surge so that it corresponds numerically to the five-tier evacuation alert levels (e.g., Heavy Rain Warning → Level 3 Heavy Rain Warning; a newly established Level 4-equivalent information called "Danger Warning" is now in operation). The alert-level notation in this document follows this new system.
Since risks affect each phase of the event differently, the structure of the conference schedule is organized first.
Note: Because the event spans a long seven-day period across multiple phases and venues, the scope of impact and required response will differ depending on the timing of any disaster.
Given the combination of the host city Hiroshima and the late-August-to-early-September timing, the risks requiring particular attention are organized below.
| Risk type | Anticipated event | Characteristics under Hiroshima / Aug 30 – Sep 5 conditions | Main impact on conference operations |
|---|---|---|---|
| Typhoon / storm | Storm winds/rain from an approaching or landfalling typhoon; planned rail suspensions; flight cancellations | Per JMA statistics (1991–2020 averages), September sees an average of 5.0 typhoon formations/month, the most of any month annually; landfalls also peak in September at 1.0/month. August has the highest number of formations of any month. From September onward, typhoons more commonly follow a "parabolic" track curving around the Pacific High and striking Japan directly. | Difficulty for participants/speakers to arrive in or depart from Hiroshima; international and domestic travel may be constrained for several days |
| Heavy rain / landslides / river flooding | Concentrated heavy rainfall from linear rainbands or the autumn rain front; landslides, river flooding | The July 2018 Western Japan Floods caused 114 deaths/missing and 624 landslide incidents within Hiroshima Prefecture. Hiroshima's residential areas sit close to steep granite slopes, making it structurally vulnerable to heavy rain. Late August–early September is also a period when the autumn rain front is easily stimulated in addition to direct typhoon rainfall. | Paralysis of city transit; difficulty reaching the venue/accommodations; possible issuance of Alert Level 4 ("Danger Warning") or Level 5 |
| Storm surge / flooding | Coastal/river-mouth flooding from storm surge during typhoon approach | The main venue (Hiroshima International Conference Center) sits within Peace Memorial Park, on low-lying former Ota River delta land at the river mouth, surrounded by the Motoyasu and Hon rivers. | Blocked access routes due to flooding around the venue; possible flood damage to underground facilities (power, HVAC, etc.) |
| Earthquake / tsunami | A Nankai Trough megaquake; an intraplate earthquake in the Aki Sea–Iyo Sea–Bungo Channel area; issuance of Nankai Trough Earthquake Extra Information ("under investigation" / "megaquake caution/warning") | In its damage estimate revised in October 2025, Hiroshima Prefecture projects that a Nankai Trough megaquake (M9.0) could bring seismic intensity of upper 5 to as high as 6 in the prefecture's southeast, over 12,000 ha of tsunami inundation, roughly 90,000 fully collapsed buildings, and roughly 14,000 deaths (about 13,000 from tsunami). The possibility of Nankai Trough Extra Information being issued during the conference period is not zero. Damaging earthquakes from prefectural active faults are rarely documented historically, but subduction-zone/intraplate earthquakes recur repeatedly. | Damage to venue/accommodations, occurrence of stranded commuters/travelers; issuance of extra information may prompt social requests such as "advance evacuation" |
| Fire / facility accidents | Fire or power outage at the venue, accommodations, or reception venue; HVAC trouble, large-scale power outages | Forest fires are more common in the dry winter–spring season, making them relatively less likely in hot, humid Hiroshima during August–September; however, electrical or kitchen fires within venue buildings (e.g., the gala dinner venue) and equipment trouble from power-demand strain during heat waves can occur regardless of season. | Facility becomes unusable, evacuation guidance needed; possible spillover to other concurrent programs (shared access routes, power, etc.) |
| Transportation disruption | Planned suspension of Shinkansen/conventional rail lines; cancellation/delay of flights including international routes at Hiroshima Airport; suspension of the Miyajima ferry route, streetcars, and buses | It is standard practice for JR West and others to announce planned suspensions the day before or day of a typhoon's approach. Because this is an international conference with a high proportion of overseas participants, the impact of missed connections and airport closures is significant. The Miyajima/Itsukushima Shrine excursion depends on ferry service and is directly affected by suspensions. | All phases (workshops, main conference, community sprint) involve cross-day travel and are vulnerable to this; speakers may be unable to reach Hiroshima at all |
| Heat-related health risks | Participant illness from extreme heat/tropical nights; issuance of heatstroke alert | Late August–early September in Hiroshima remains likely to bring very hot/extremely hot days. Outdoor programs such as the Ice Breaker (Hiroshima Gate Park) and the Miyajima excursion carry particular risk. | Need for emergency response at outdoor programs; absences or early departures due to participant illness |
| Compound / other risks | Risk of overlapping events across the 7-day period; infectious disease outbreaks; overseas-participant-specific issues (language, travel documents, insurance, etc.) | Because participant composition and venues differ across the Workshop (8/30–31), Main Conference (9/1–3), and Community Sprint (9/4–5) phases, a single uniform response policy may not suffice | Different decisions and communications are needed per phase; a multilingual emergency contact system is essential |
According to JMA's 1991–2020 averages, typhoon formation is highest in August, followed by September. The number of typhoons approaching and making landfall in Japan is highest in September (approach: about 3.3/month; landfall: about 1.0/month), and from September onward more typhoons take a track that curves around the Pacific High to strike Japan directly. Many past typhoons that caused major disasters followed this track in September.