On the evening of the 16th, Haidian encountered small-scale and strong convective weather, and the accumulated rainfall in multiple areas exceeded 50 mm in one hour.
2 people were killed while driving under the bridge of Hanhe Road.
The Beijing News reported on the morning of the 17th that Haidian District reported that there had been a process of strong local rainfall in the area under its jurisdiction. There was severe water accumulation under the Hanhe Road Railway Bridge for a short time. Unfortunately, the hospital failed to rescue.
Experts explained that Haidian encountered a small-scale strong convective "super cell" that night, which formed fast and difficult to predict, and the short-term precipitation had exceeded the design standard for the discharge of the pipe network.
Therefore, there was water accumulation under the bridge.
2 people who were trapped while driving through the water were killed
An eyewitness citizen living nearby told reporters that the rain was heavy here on the night of the 16th. He ran out to see the water accumulated under the bridge from his home. When I went to the scene to rescue, the water was too deep and I didn't dare to go forward. Later I heard that someone had been killed."
From the video posted on the Internet by netizens, it can be seen that under a lower concave bridge, the flooded vehicle will float up due to the accumulation of water. In the distance, there are flashing warning lights, and the staff are on guard at the periphery of the scene.
In another video, three people were doing first aid measures to a lying person on the roof of a flooded car. They turned around and shouted "Hit 120!" to the onlookers. Someone in the video responded "Hit, hit."
The reporter was informed that after the accumulation of water occurred on the evening of the 16th, relevant departments of Haidian District and Tiancun Road street carried out drainage and drainage.
The road is a municipal road. After Beijing Drainage Group arrived, it took over the drainage and drainage work.
Yesterday morning, the reporter called the Tiancun Police Station of the Public Security Bureau of Haidian District, Beijing where the incident occurred.
"There was no water accumulation in the road section where the incident occurred"
The accident site was located under the Hanhe Road Railway Bridge, only more than 300 meters away from the Tiancun Station of Metro Line 6, and adjacent to Jingliang Square on the southeast side.
The Jishui section is a concave bridge with four bridge holes and two-way six-lane.
The section underneath the Xisha line railway, the reporter noticed that this railway bridge is basically the lowest point in the surrounding area, and the slope is relatively steep.
According to a video taken by netizens, after the rain, the rain continued to wash down this section of the road, and the water was rushing.
However, after searching, the reporter did not find any obvious warning signs on the road and its surroundings. Only the bottom pier had a red water level warning line with a height of more than 20 centimeters.
After the rain subsided, there was still a lot of silt on the roadside.
Yesterday morning, relevant units carried out clean-up work at the scene.
Along the road, the reporter walked into the deepest part of this recessed railway bridge. Clear watermark lines can be seen on the concrete guardrails on both sides of the road. The watermark lines at the piers are already close to two meters.
"This bridge has hardly ever accumulated water." The surrounding residents said.
The reporter noticed that Tiancun East Road, 400 meters west, also crossed the Xisha Line. According to the description of surrounding residents, there was also water accumulation on the evening of the 16th.
According to the Beijing Daily, the accumulation of water in the bridge area of the Hanhe Road Railway was "implicated" by the inversion.
Due to the saturation of the main drainage line in the bridge area where water has occurred, the accumulated water has risen rapidly, and even the manhole cover has been lifted up by the inverted rainwater. happen.
At present, the stagnant water on the Hanhe Road Railway Bridge has been drained, and the traffic has returned to normal.
Doubt 1
Is a weather warning issued in advance?
The rainstorm warning level in Haidian District rose from blue to orange within half an hour
At around 21:00 on the 16th, within half an hour, the rainstorm warning level in Haidian District was upgraded from blue to yellow, and from yellow to orange.
Almost at the same time, at 21:01 and 21:01 on the 16th, the official Weibo of the Beijing Meteorological Bureau issued a blue rainstorm warning and a gale blue warning.
At 21:15, 21:15, and 21:25 on the 16th, within half an hour, the rainstorm warning level in Haidian District was upgraded from blue to yellow, and from yellow to orange.
The orange rainstorm warning issued by the Haidian District Meteorological Observatory at 21:25 shows that precipitation is expected to continue until 23:00. The accumulated rainfall in the streets and towns of central and southern Haidian is relatively large. In mountainous and shallow mountainous areas, there may be small and medium-sized river floods and mountain torrents induced by heavy rainfall. , Geological disasters and other secondary disasters, low-lying areas may have water.
Meteorological expert Zhang Mingying introduced that from 21:00 to 21:50 on the 16th, the rain in Haidian District was the heaviest. "In the past one hour, precipitation in the vicinity of Minzhuang, Yuyuantan, and Chedaogou reached 50-70 mm. It’s already raining heavily.”
After 22:00, the range of heavy rainfall suddenly expanded, covering Yongfeng Middle School, Qinglong Bridge, and Chenchun Bridge. The accumulated rainfall in one hour also reached 50-70 mm.
"The rainfall in a short period of time is extremely heavy, that is, the rain is very strong and it is easy to cause disasters." Zhang Mingying explained.
Doubt 2
Why did the precipitation come and go so fast this time?
Small-scale strong convective "supercells" form fast and difficult to predict
Zhang Mingying analyzed that the Haidian District encountered small-scale strong convective weather on the evening of the 16th, called supercell.
"That is to say, a cumulonimbus cloud that has developed particularly vigorously. When it is formed, the characteristics of disastrous weather such as heavy rain and strong wind are particularly obvious."
Super monomers form quickly and disappear quickly.
It can be seen from the precipitation statistics of Haidian District that the time for this heavy rainfall to concentrate is about two hours.
At 21:15, 21:15, and 21:25 on August 16, the rainstorm warning level in Haidian District was upgraded from blue to yellow, and from yellow to orange in less than half an hour.
At 23:10 that day, the orange warning signal of heavy rain was lifted in Haidian District.
This type of weather is often difficult to forecast in advance.
"Generally, such small-scale weather covers a few kilometers, and its life is short, and it disappears after two or three hours. Therefore, the forecast of this kind of weather is very small, and it is impossible to predict it one day in advance like a weather forecast. "Zhang Mingying said.
Zhang Mingying explained that the best way to find a supercell that is not easily forecasted in advance is to use weather radar to monitor it.
According to the analysis of actual weather conditions, forecasters can forecast different times in advance.
Even after the discovery of supercells, the forecast aging can only be calculated in hours.
"We can see that the Haidian District Meteorological Observatory issued three consecutive warnings in about half an hour, which is the reaction after the supercell was discovered by radar."
Doubt 3
How heavy was the rain on the night of the incident?
Hourly rain intensity reaches more than 50-60 mm
According to Chai Fuxin, a senior engineer at the Engineering Research Center for Flood Control, Drought Relief and Disaster Mitigation, China Institute of Water Resources and Hydropower Research, according to the iso-surface map data, the hourly rainfall intensity of the Hanhe Road Railway Bridge reaches 50-60 mm.
According to the Beijing Daily, people familiar with the matter revealed that 60 millimeters of rain fell in 20 minutes in Haidian District.
The rainfall is too much and too fast.
According to statistics from the Beijing Municipal Meteorological Bureau, on the night of the 16th, the accumulated rainfall of the Beichanghe Hydrological Station in Haidian District exceeded 80 millimeters in one hour, and the accumulated rainfall in the streets and towns of central and southern Haidian was relatively large.
Residents in Haidian District reported that the umbrella was shattered by the heavy rain accompanied by strong winds, and the three trees in the community were also broken.
From 20:30 on the 16th to 3:00 on the 17th, the average rainfall of the national weather station Haidian station reached 55.9 mm.
The maximum wind speed of the gust is 8 and the maximum wind speed reaches 18.6 m/s.
"When it rains, you can't see people at all. Water is poured in the sky." Mr. Sun's family lived in the Xuefangyuan community one kilometer southwest of the railway bridge. He told the Beijing News reporter that the rain was so heavy at around 9pm on the 16th. It was outrageous and the wind was very strong. "My wife went downstairs to give me an umbrella. She was trapped in the communication room of the community. The umbrella was shattered. There were trees in the community that were broken by the wind."
Mr. Sun recalled that the rainstorm lasted about 40 minutes.
Chai Fuxin explained that the urban drainage system includes the natural drainage of rainwater by the pipe network. The pipe network construction standard in most areas of Beijing is once in 1-3 years, and in some areas it is high.
He pointed out that the rain intensity of the Hanhe Road Railway Bridge on the evening of the 16th was too strong, and the hourly rain intensity was above 50-60 mm, which has reached the construction standard of once in 5-10 years in a short time.
"This means that the rain on the Hanhe Road Railway Bridge on the evening of the 16th has exceeded the construction standards of the pipe network, so there will be stagnant water, which makes its own rainwater unable to be discharged, and the rainwater on the surrounding roads is also in a short period of time. Confluence, forming deep stagnant water."
Doubt 4
Has the site of the incident been drained?
Rainfall areas are uncertain; flood-prone points are checked and updated every year
On July 21, 2012, a heavy rainstorm occurred in Beijing, causing serious loss of personnel and property.
In November of that year, Beijing proposed to comprehensively improve the city’s water conservancy engineering facilities’ flood control capacity and water resource utilization capacity, and eliminate the hidden danger of urban waterlogging. Regulating storage tanks and pumping stations, and taking measures for the extraction of standing personnel and facilities for key overpasses, are required to be completed within 4 years.
So is the Hanhe Road Railway Bridge within the scope of reconstruction?
Chai Fuxin introduced that under the organization of the Beijing Municipal Water Affairs Bureau, relevant research departments conducted waterlogging risk analysis in key areas of Beijing, especially the central city, from 2013 to 2017, and sorted out areas prone to waterlogging. Establish ledgers for flood-prone points and water accumulation points, and formulate "one bridge, one policy" emergency plan.
However, due to the uncertainty of rainfall areas, flood-prone points need to be checked and updated every year.
Is there still a possibility of danger after the flood-prone point is renovated?
Chai Fuxin gave an example. After "July 21", the flood drainage capacity of Lianhua Bridge, the underground passage of Beijing West Railway Station, and Guangqumen was improved significantly.
He said that in the face of heavy rains, urban infrastructure still needs to be tested by actual heavy rains. “Maybe it will rain heavily this year, but it will rain heavily next year. If the rain exceeds the design standard, water will be generated. We are unlikely to Raising all facilities to a very high standard can only focus on the gradual transformation of areas prone to water accumulation."
How can we prevent the tragedy from happening?
Chai Fuxin said that it is possible to consider raising the drainage standards. “The occurrence of extreme heavy rainfall is uncertain, so government departments must strengthen the management and detection of flood-prone points.” At the same time, early warnings and other countermeasures must be taken for heavy rainfall. .
The public should also be reminded to enhance their safety awareness and avoid going to sections prone to stagnant water and low-lying sections when heavy rainfall occurs.
■ Dialogue
Wang Jun, rescuer of flooded vehicles on Hanhe Road Railway Bridge:
Feeling uncomfortable, I'm late
At around 9 pm on August 16, 37-year-old Wang Jun participated in the rescue while driving across the Hanhe Road Railway Bridge.
Yesterday afternoon, Wang Jun told a reporter from the Beijing News, “When I moved people to the roof, I looked at people as if they were dysfunctional. I felt very uncomfortable and felt that I was late.”
Beijing News: How was the water accumulation on the Hanhe Road Railway Bridge at that time?
Wang Jun: The road surface is concave, and the concave part is full of water. You can't see any cars under the water, and you can't see anything.
Beijing News: How was the flooded vehicle discovered?
Wang Jun: At that time, the flooded car was already covered, and it was invisible from standing on the side of the road. People around said that there was a car under the bridge that did not come out. Someone should have seen it before it was flooded.
At this time, two people got into the water and said to look for a car.
Beijing News: How was the rescue at the scene?
Wang Jun: After the two people who got into the water first touched the car, they found someone in the car through the windshield, and immediately shouted to the people on the side of the road, and the people around also shouted to each other, "Who can swim and save people." I can swim. The water is better, so I didn't think about it too much. I took off my clothes and went into the water.
When I swam, there were already 3 people who were rescuing, count me 4, and then 2 more people came.
When we got into the water, let the person next to you call the police and call 119 or 120.
At first I thought the water was not too deep. I didn’t expect that I only walked more than ten meters into the water. I couldn’t touch the ground with my feet. I had to swim over it. I swam for about 1 minute and then I swam through the bridge hole to reach the location of the flooded vehicle. I think it’s under the bridge. The water should be 2 meters deep.
The two people who got into the water first started smashing windows and driving doors.
The doors and windows of the car were shut tightly, and it took them a lot of effort to open them.
We dragged a man and a woman in the driver's cab and co-driver's cab out through the door of the driver's cab, and two people standing on the roof of the car pulled them onto the roof of the car.
The two seemed to be around 60 years old, and had no breath when they were dragged out of the car.
In addition, someone grabbed the door of the cab, and put their feet into the rear seat to test to see if there was anyone else in the rear seat.
After confirming that they did not, the two people on the roof gave them artificial respiration and continued chest compressions for first aid.
Beijing News: How long did the rescue last?
Wang Jun: The rescue lasted about 40 minutes.
After the rescue, the water level dropped a lot. A big brother was carrying a person on his back, and the firefighter was pulling a person. After everyone moved the two drowning people to a place where there was no water, the water had dropped to our chest.
Beijing News: What kind of difficulties did you encounter during the rescue process?
Wang Jun: I feel that I can’t work hard, it’s too tired, and when I move the person to the roof, I look at people as if I can’t do it.
Beijing News: Did you consider the danger at the time?
Wang Jun: I didn't think so much at the time, but I thought I could swim and I must go.
Because I can swim, and the water is good, I think that there is no water or grass under my feet, I think it doesn't matter, the past is over.
A06-A07 edition writing/Beijing News reporter Ma Jinqian Pei Jianfei Sha Xueliang Wu Tingting Wu Wei Dai Xuan Wang Jingxi Feng Yajun Mu Hongju Zhao Min intern Xu Lindi