GUNMA - A 56-year-old woman who was swept away by a flash flood while climbing a mountain stream in Minakami, Gunma Prefecture, was rescued alive on August 17 after surviving eight days in the remote mountains with a broken heel, relying on food she had brought with her, stream water and her knowledge of the area until anglers found her sitting on a forest road.
The accident occurred in a mountainous area near Naramata Dam, a popular destination for boating and other water sports that also has campgrounds nearby. The woman was eventually found about 3 kilometers from the dam in an area with no houses or other residences.
Police received an emergency call shortly after 4 p.m. on August 9 reporting that a woman had been swept away by a flash flood while climbing a stream and could no longer be located.
The woman had begun stream climbing with three friends near the confluence of the Naramata River and Heizuru Stream. During the trip, the group was caught in a sudden flash flood, and she was the only person who went missing.
After being carried away by the water, the woman eventually reached the bank. She later said she ate food she had been carrying and is also believed to have drunk water from the stream while trying to survive.
Her condition remained unknown for eight days until around 7 a.m. on August 17, when a man and woman who had come to the area to fish spotted her sitting on a forest road.
The woman had suffered a serious fracture to the heel of her right foot and was physically weakened, but her condition was not life-threatening. She was taken to a hospital.
A local resident described her survival as close to a miracle, noting that the area becomes completely dark at night, has no streetlights or residents and is inhabited by various wild animals.
The accident has also highlighted the danger of flash floods in mountain streams, where calm waterways can transform within minutes.
Video recorded on August 9 in the Sanashi River in Niigata Prefecture showed another group encountering a flash flood on the same day as the Gunma accident.
The footage was taken by a man with seven years of stream-climbing experience. After rain began, he abandoned his climb and sheltered beneath trees. About 20 minutes later, the river level began rising rapidly.
He moved to higher ground and watched as muddy water surged downstream with a roaring sound, transforming the previously calm river in only a few minutes.
"The spray is reaching where we were just standing. This is bad, this is bad," a voice can be heard saying in the footage.
The man later said the increase in water level happened almost instantly. Although he knew about the dangers of flash floods and had experienced smaller ones before, he said the scale and force of this one were so great that he was afraid even to approach the stream.
Strong rain may also have fallen upstream of the Naramata River when the 56-year-old woman went missing.
Takahiro Kinoshita, an official with the Tone River Upper Reach Integrated Management Office, said thunderstorms had been forecast for the Naramata River basin and radar showed rainfall upstream.
"A fairly strong area of rain had developed," Kinoshita said. "It appears the rain clouds formed very suddenly."
The dam management office said the rainfall may have triggered a flash flood in the Naramata River, which runs through the mountainous area.
Conditions remained difficult after the woman disappeared. Two days later, Typhoon No. 15 made landfall in southern Ibaraki Prefecture, bringing unsettled weather to the region.
Weather forecaster Go Yazawa said conditions favorable for light rain persisted for two or three days and that temperatures in the high-altitude area were likely considerably lower than in surrounding locations.
A nearby campground said nighttime temperatures can fall to around 12 degrees Celsius.
After washing ashore, the woman apparently wandered through the mountains while surviving on the food she had brought before reaching the forest road where the anglers eventually found her.
Mountain guide Norio Toyono, who is familiar with the area, said two factors may have played an important role in her survival: careful preparation before entering the stream and knowledge of possible escape routes.
Experienced stream climbers typically study "escape routes" that can be used in an emergency, Toyono said, as well as detailed route maps showing the terrain and course of a stream.
"If you have been stream climbing for many years, you generally know the route maps," he said. "This is different from simply becoming lost in the mountains. Because she was following a stream, she probably knew that if she went downstream she would eventually reach a forest road."
Toyono also noted that the area attracts many anglers, suggesting the woman may have deliberately remained near the road in the hope that someone would pass by.
The woman's husband spoke publicly on the afternoon of August 18, thanking those involved in the search and rescue.
"We caused everyone trouble and concern," he said. "I am grateful that she came home. Thank you very much."
Experts say flash floods have become an increasingly important hazard as changing weather patterns create conditions in which intense rainfall can develop rapidly in mountain areas.
Nobuyuki Tsuchiya of the Riverfront Research Center, an expert in river disaster prevention, said people near rivers should watch closely for warning signs such as rapidly developing towering clouds and the sound of thunder.
Because flash floods can arrive suddenly and with tremendous force, people should immediately move away from a river when such signs appear.
Changes in water level are another warning. A rise that covers rocks that had previously been visible can indicate increasing danger, but an unexpected drop in the water level can also signal a serious threat.
If a landslide or other obstruction blocks a river upstream, the water level downstream may temporarily fall. If the blockage then breaks, the accumulated water can rush downstream at once.
Experts therefore advise people engaged in stream climbing or other river activities to pay attention to even small changes in water level and weather conditions, particularly in mountainous areas where conditions can deteriorate rapidly.
Source: フジテレビ 報道
