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[U11-06] Characteristics of the location where human casualties occurred due to heavy rainfall on the Noto Peninsula in September 2024
★Invited Papers
Keywords:flood and sediment disaster, meteorological information, hazard map
On September 21, 2024, heavy rain fell in the Noto region of Ishikawa Prefecture. This heavy rain caused damage in Wajima City, Suzu City, and Noto Town in Ishikawa Prefecture, including 16 deaths.
The author has been conducting research into the human toll (dead and missing) of the wind and flood disasters that have occurred in Japan since 1999. The location and circumstances of the damage are estimated based on information that is generally available, such as news reports, housing maps, and aerial photographs, as well as the author's observations on site. In recent years, the author has been examining disaster risk information (hazard maps, etc.) for areas that have experienced flooding and sediment disasters, as well as meteorological information during disasters. In this presentation, we will report on the results of our survey into the heavy rain disaster on the Noto Peninsula.
The meteorological information examined in this study is as follows.
* Precipitation (any of 1, 2, 3, 4, 5, 6, 12, 24, 48, or 72-hour precipitation totals) at a JMA observation station near the location where the disaster occurred
* Weather warnings that had been issued by the time the disaster occurred
* Heavy rainfall information
* Recording short time heavy rain information
*The level of “Kikikuru” at the time of the damage
The disaster risk information examined in this study was flood inundation areas, landslide disaster warning areas, and topographical classification.
The location of the disaster was estimated for 15 of the 16 victims. There were multiple cases of damage occurring in the same location, and the number of locations where damage occurred was 13. The breakdown by municipality is as follows: 8 locations (10 people) in Wajima City, 3 locations (3 people) in Suzu City, and 2 locations (2 people) in Noto Town.
The hazards that caused damage were “flood” in 7 places (9 people) and “sediment disaster” in 6 places (6 people). Sometimes it is difficult to classify between “flood” and “sediment disaster”. In this disaster, there were relatively many cases like this. In the author's survey, cases where the gradient of the valley near the site of the damage is 3 degrees or more are classified as “sediment disaster”, and cases where it is less than 3 degrees are classified as “floods”. This is because the slope at which debris flows flow is generally 2 to 3 degrees or more.
The locations of the damage were as follows: 6 indoor locations (6 people), 6 outdoor locations (7 people), and 1 unknown location (2 people). One of these (one person) was a case where the person was swept away by a flood while traveling by car.
There were 11 locations (13 people) where the time of the disaster could be estimated. The largest ever recorded rainfall was observed at all 11 locations. At the time of the damage, the level of “Kikikuru” was “Danger (Level 4)” in 8 places (9 people) and “Imminent (Level 5)” in 3 places (4 people). Heavy rainfall information was announced at all 11 locations. Recording short time heavy rain information was announced at eight locations (ten people).
Of the six places classified as “sediment”, three (three people) were outside the scope of the sediment disaster warning area. Two of these locations (two people) were in areas with no houses around them and were not subject to the landslide disaster warning area system.
All seven locations classified as “floods” were outside the scope of the flood inundation zone. However, the topography of all seven of these places is lowland, and they are not places where flooding does not occur. In some cases, no flood inundation zones have been designated near small and medium-sized rivers. It is important to promote the designation of flood inundation zones near small and medium-sized rivers, as well as to raise awareness of the risk of flood disasters near small and medium-sized rivers.
The author has been conducting research into the human toll (dead and missing) of the wind and flood disasters that have occurred in Japan since 1999. The location and circumstances of the damage are estimated based on information that is generally available, such as news reports, housing maps, and aerial photographs, as well as the author's observations on site. In recent years, the author has been examining disaster risk information (hazard maps, etc.) for areas that have experienced flooding and sediment disasters, as well as meteorological information during disasters. In this presentation, we will report on the results of our survey into the heavy rain disaster on the Noto Peninsula.
The meteorological information examined in this study is as follows.
* Precipitation (any of 1, 2, 3, 4, 5, 6, 12, 24, 48, or 72-hour precipitation totals) at a JMA observation station near the location where the disaster occurred
* Weather warnings that had been issued by the time the disaster occurred
* Heavy rainfall information
* Recording short time heavy rain information
*The level of “Kikikuru” at the time of the damage
The disaster risk information examined in this study was flood inundation areas, landslide disaster warning areas, and topographical classification.
The location of the disaster was estimated for 15 of the 16 victims. There were multiple cases of damage occurring in the same location, and the number of locations where damage occurred was 13. The breakdown by municipality is as follows: 8 locations (10 people) in Wajima City, 3 locations (3 people) in Suzu City, and 2 locations (2 people) in Noto Town.
The hazards that caused damage were “flood” in 7 places (9 people) and “sediment disaster” in 6 places (6 people). Sometimes it is difficult to classify between “flood” and “sediment disaster”. In this disaster, there were relatively many cases like this. In the author's survey, cases where the gradient of the valley near the site of the damage is 3 degrees or more are classified as “sediment disaster”, and cases where it is less than 3 degrees are classified as “floods”. This is because the slope at which debris flows flow is generally 2 to 3 degrees or more.
The locations of the damage were as follows: 6 indoor locations (6 people), 6 outdoor locations (7 people), and 1 unknown location (2 people). One of these (one person) was a case where the person was swept away by a flood while traveling by car.
There were 11 locations (13 people) where the time of the disaster could be estimated. The largest ever recorded rainfall was observed at all 11 locations. At the time of the damage, the level of “Kikikuru” was “Danger (Level 4)” in 8 places (9 people) and “Imminent (Level 5)” in 3 places (4 people). Heavy rainfall information was announced at all 11 locations. Recording short time heavy rain information was announced at eight locations (ten people).
Of the six places classified as “sediment”, three (three people) were outside the scope of the sediment disaster warning area. Two of these locations (two people) were in areas with no houses around them and were not subject to the landslide disaster warning area system.
All seven locations classified as “floods” were outside the scope of the flood inundation zone. However, the topography of all seven of these places is lowland, and they are not places where flooding does not occur. In some cases, no flood inundation zones have been designated near small and medium-sized rivers. It is important to promote the designation of flood inundation zones near small and medium-sized rivers, as well as to raise awareness of the risk of flood disasters near small and medium-sized rivers.