"The road is getting wider and wider, but it is getting harder and harder to get into the water." On July 23rd, 2021, when Bo Huang, a citizen of Zhengzhou, passed by the wulongkou parking lot of Metro Line 5 (hereinafter referred to as wulongkou parking lot), he was so emotional when he looked at the flood continuously spewed out by the pump pipeline.
On July 20th, Zhengzhou Metro Line 5 was forced to stop by flood, and more than 500 people were trapped. At present, at least 12 people have been killed. According to the official report on the cause of the accident, on July 20th, a rare torrential rain suddenly fell in Zhengzhou, causing serious water accumulation in the wulongkou parking lot of Zhengzhou Metro Line 5 and its surrounding areas. At about 18 o’clock, the accumulated water washed out of the water retaining wall of the entrance line and entered the main line section, causing a train on Zhengzhou Metro Line 5 to stop.
What is not clear in the circular is, where did the serious accumulated water in wulongkou parking lot and its surrounding areas come from? Is there any other spillway before the flood breaks through the parking lot retaining wall? And, after the meteorological department issued a number of red warnings, why didn’t this "well-known" low-lying area respond to the plan?
According to the survey of Interface News, it is no accident that water accumulated in the parking lot and its surrounding areas in wulongkou. Ten years ago, it was a "famous" water accumulation area, and it has improved after treatment. However, before the rainstorm, tens of meters of cement cover plates were added to the open drain more than 20 meters away from the parking lot in wulongkou, which led to poor flood discharge, or was one of the reasons for the water accumulation in the subway tunnel.
"Water from three directions meets in one place"
Bo Huang felt that flooding into Metro Line 5 was not completely inevitable.
At about 17: 00 on July 20th, the accumulated water brought by the rainstorm was almost knee-deep, but Bo Huang decided to walk home from the company near the parking lot in wulongkou. He has lived in this area for nearly 40 years and is familiar with the roads and terrain here. He walked south along Lantian Road, and when he reached the first intersection, he turned into Songshan North Road.
"It’s not stagnant water. I can see the water flowing to the north (in the direction of wulongkou parking lot) with the naked eye." Bo Huang said. He walked in the direction of the incoming water, feeling that the water was getting deeper and deeper, and the resistance his body encountered was getting bigger and bigger. Although the parking lot in wulongkou is low-lying, he was somewhat surprised by the rising speed of the flood.
Less than 1000 meters from the company to the first intersection, Bo Huang walked for more than half an hour. This is an intersection inclined to the east, and the four roads radiated from it have four names due to different construction times, namely Songshan North Road facing east, wulongkou South Road facing west, Tongbai North Road facing south and Lantian Road facing north. Arriving at the crossroads, Bo Huang was surprised to find that all the accumulated water on the other three roads rushed to Lantian Road, heading north towards the parking lot in wulongkou.
Bo Huang is 1.75 meters tall. At this time, the flood has flooded his waist. He didn’t dare to wade forward and chose to return to the company. He walked back carefully along the current.
At about the same time, Wang Chao, a worker near the parking lot of Line 5, came out of the shed to see if his car was flooded. He saw that the accumulated water on the environmental protection road in front of the office area of wulongkou parking lot was flowing in the direction of Lantian Road; Not only that, the water in the northern section of Lantian Road is also flowing south. Floods from three directions flock together to the intersection of Lantian Road and Environmental Protection Road, which is the wall of wulongkou parking lot on Metro Line 5 facing the highway.
Wang Chao noticed that across the Blue Sky Road, a yellow plastic baffle was erected opposite the parking lot in wulongkou. Behind the baffle was a small river, but the flood could not cross the baffle for a while and accumulated higher and higher in this area. Wang Chao had never seen such a flood, so he ran back to the shed. Before long, he heard "a sound like a waterfall falling", which lasted for a while and became a steady sound of falling into the water.
On his way back, Bo Huang felt that the flood had a downward trend. When he walked back to the parking lot near wulongkou, he found out the reason: the wall near Lantian Road in wulongkou parking lot was washed away, and the flood fell like a dam and entered the subway parking lot dozens of meters deep.
Afterwards, Zhengzhou officially informed that on July 20th, a rare torrential rain suddenly fell in Zhengzhou, causing serious water accumulation in the wulongkou parking lot of Zhengzhou Metro Line 5 and its surrounding areas. At about 18 o’clock, the accumulated water washed out of the water retaining wall of the entrance line and entered the main line section, causing a train of Zhengzhou Metro Line 5 to stop in the section from Shakou Road Station to Beach Temple Station, and more than 500 passengers were trapped.
Zhengzhou Metro Line 5 started construction in December 2014 and was opened to traffic on May 20, 2019. This line is a ring road with 32 stations, a depot and a parking lot-wulongkou parking lot, which is the busiest line in Zhengzhou subway.
The subway parking lot mainly undertakes the work of stopping inspection and cleaning of subway trains. The train passes through the entrance and exit lines and enters the main line. This is also the route for the flood to enter the subway car tunnel. Although the parking lot in wulongkou is a ground parking lot, there are still several meters of height difference between the train parking area and the ground. On the periphery of the parking lot, there is a fence with a brick base and a steel pipe at the upper part.
According to a tender information of the parking lot published in 2017, the parking lot in wulongkou is in the shape of a knife handle, with a length of about 900m from east to west and a width of about 220 m from north to south. The total planned area of the parking lot is about 18.3 hectares, of which the subway land area is about 11.3 hectares.
At this time, Bo Huang noticed that, just opposite the wall of the washed-out parking lot of Metro Line 5, the yellow building baffle was also washed away with some gaps, but on the other side of the gap, the flood did not drain into the river smoothly, but stayed on a section of tens of meters long cover plate on the river.
He believes that the rainstorm is not the whole cause of the disaster. "The rainstorm is very heavy, but if the drainage ditch can play a role, it will not necessarily flood the subway."
Open drainage ditch becomes culvert
On July 23rd, the interface journalist came to the wulongkou parking lot of Metro Line 5. The washed-out area seemed to have opened a gap, and the fence and reinforced guardrail fell into the parking lot, with messy garbage hanging on it. Several pumps are working to drain the accumulated water to the road several meters away. The discharged water does not flow, but is deposited here and enters the underground pipeline through the filter screen. "Everyone knows that the terrain here is the lowest." Bo Huang said.
Across the Blue Sky Road, more than 20 meters away is a small river named wulongkou Minggou, which flows from south to north. Bo Huang introduced that when Lantian Road was not built, wulongkou Minggou belonged to Minghe River, and nearby villagers often built board houses to do business. Later, the blue sky road crossed the river, and a section of the river became an underground river.
The natural landform of Zhengzhou is high in the southwest and low in the northeast, with a natural gradient of 3.4‰ and a natural height difference of more than 30 meters between the west and east of the city. Wulongkou parking lot is located in the northwest of Zhengzhou, between the Second Ring Road and the Third Ring Road. Compared with the whole city, the terrain here is not low, but it is a well-known depression in wulongkou area. Standing near the washed-out wall of the subway parking lot, you can feel visually that the road surface in three directions is obviously higher than here.
The problem of water accumulation near wulongkou has a long history. As early as 2009, a person in charge of the Zhengzhou Municipal Department introduced in an official document that the accumulated water in the roads of Funiu Road and Tongbai Road was mainly discharged to wulongkou Minggou, and then discharged from the urban area through wulongkou Minggou. However, before entering wulongkou Minggou, the accumulated water in these roads had to "climb" over a high slope of 80cm before entering the river.
In July 2010, Zhengzhou City was hit by heavy rain, and a large number of roads were flooded. The citizens complained quite a lot. In this context, the Zhengzhou municipal government sorted out 62 water accumulation points in the whole city, and the responsible persons of several units subcontracted them to transform them in place within a time limit. Among the materials seen by the interface journalists, the problem of water accumulation in the Minggou area of wulongkou was "famous on the list", and the subcontracting leader was Yue Moumou, then vice chairman of Zhengzhou CPPCC.
After this reconstruction and subsequent dredging, the drainage function of wulongkou open ditch has been improved, and the problem of water accumulation in the nearby area has been alleviated to some extent. Bo Huang remembers that there was a rainstorm in Zhengzhou about three years ago. At that time, the accumulated water in the vicinity was close to the knees, but the excessive accumulated water finally flowed into the open ditch in wulongkou, causing no serious losses.
A number of nearby residents said that this small river has a history of several decades, and later the wulongkou Sewage Treatment Plant was built nearby, and the small river became a drainage river of the plant. After the construction of Lantian Road, the river flows out from under the road, and people standing on the side of the road can see the river. In case of rainstorm, excessive accumulated water directly drains into the open ditch of wulongkou over the subgrade, flows about 5 kilometers, flows into the famous Jia Luhe of Zhengzhou, and finally flows into the Huaihe River.
The interface journalist noticed that the height of the brick wall base of wulongkou parking lot is obviously higher than the entrance of wulongkou Minggou across the road. This means that when the flood reaches this area, it should normally first flood into the open ditch in wulongkou and be discharged.
A number of nearby citizens said that about a few months ago, a cement cover plate was added to the river section here, and the original open ditch became a culvert, resulting in poor drainage of excessive accumulated water. The interface journalist saw at the scene that the cover was about 8 meters wide and nearly 50 meters long, and it was made by splicing a single white reinforced concrete beam. At the gap between the two covers, a large amount of domestic garbage flowed down.
There are several excavators parked by the river. The yellow baffles have been dismantled, some have been squashed, and some mounds have been shoveled off. From the sidewalk into the upper cover, you can see the whole picture of wulongkou open ditch. The river is about ten meters wide and five or six meters deep, and there are a lot of weeds and garbage scattered on both sides. Wastewater flows out of the river under the cover plate and smells bad.
There is a precedent for poor flood discharge after the river is covered with slabs. On July 18th, 2007, Jinan was hit by a super heavy rain, and many flood discharge ditches covered with sheds were congested, resulting in poor flood discharge, which caused many losses to citizens’ lives. Later, Jinan took this opportunity to demolish some buildings with shed roofs on flood discharge ditches.
On July 23, a staff member of Shifo Sub-district Office of Zhengzhou High-tech Zone responded to the news of the interface. The open ditch in wulongkou was managed by the office. Because of the height difference between the river and Lantian Road, there was a safety hazard, so a cover plate was added to the river, which will be developed into a green belt. "After the approval of the municipal government, the (high-tech zone) management Committee." Regarding the impact of increasing the cover plate on flood discharge, she said that "this situation should have been considered."
Does the red warning work?
So, does the relevant department of Zhengzhou really consider the flood discharge risk brought by heavy rain? Are all aspects of early warning in place?
After the disaster, Zhengzhou officially announced that from 20: 00 on July 17 to 20: 00 on July 20, the rainfall during the three days was 617.1 mm. Among them, hourly precipitation and single-day precipitation have all exceeded the historical record of 60 years since Zhengzhou station was established in 1951. The average annual rainfall in Zhengzhou is 640.8mm, which is equivalent to the previous year’s rainfall in these three days. At the same time, the saying about the rainstorm "once in a hundred years" and "once in a thousand years" began to spread.
On July 21st, Chen Tao, chief forecaster of the Central Meteorological Observatory, introduced that from the perspective of atmospheric science research, it was after 1950 that China formed a rigorous meteorological record, and only then did it have a more accurate and complete scientific record of rainfall. Up to now, the whole rainfall record is about 70 years. He said that the so-called "once in a hundred years" and "once in a thousand years" is "difficult to talk about this problem" until reliable, long-term and effective rainfall records are obtained.
According to public information, on July 19th, @ Zhengzhou Meteorology released a number of information about local heavy rainfall. At 12: 28 on July 19th, Zhengzhou Meteorological Observatory released the yellow rainstorm warning signal. The approaching forecast issued at 13: 00, 14: 00, 14: 28, 16: 00, 18: 00 and 18: 13 on the same day is still yellow rainstorm warning, or yellow rainstorm warning and lightning warning.
At 19: 13 on the same day, Zhengzhou Meteorological Observatory issued the first orange rainstorm warning signal of this rainfall. At 21: 59, Zhengzhou Meteorological Observatory released the first rainstorm red warning signal of this round of rainfall. At 06: 02 on July 20th, the station released the rainstorm red warning signal again. On the same day, Zhengzhou Meteorological Observatory issued 10 red rainstorm warnings.
The rainstorm warning signal is divided into four levels: blue, yellow, orange and red. In Chinese mainland, the red rainstorm warning signal is the highest level. The corresponding defense guidelines include: the government and relevant departments should do a good job in emergency and rescue work against rainstorm according to their duties; Stop assembly, suspend classes and suspend business (except for special industries); Do a good job in the prevention and rescue of disasters such as flash floods, landslides and mudslides.
Looking back before and after the disaster, these early warnings did not play their due role. On July 23, interface journalists interviewed a number of surrounding citizens along the flood discharge channel of Changzhuang Reservoir in Zhengzhou City. Many people said that they had not received any reminders such as suspension of work, suspension of classes and evacuation before the waterlogging occurred, and many people still went to work as usual.
A person from the meteorological department introduced to the interface news that it is rare to issue nearly 10 red rainstorm warnings in one day, and the emergency management department should pay enough attention to it. However, among various government units, the meteorological department is relatively weak and is a "small department". "They listen to what we say, and they don’t listen if they don’t want to listen."
According to the requirements of Zhengzhou City Flood Control Emergency Plan, the road and bridge facilities in the district should be inspected before the flood season. Dredging open ditches and rainwater collection wells in the jurisdiction; Clean up the branches and leaves on the grate of the water collecting well in time; Control and dispose of the water accumulation area of the district management road. River and municipal departments should, according to the rainfall situation, open the drainage gates of river channels and open ditches in advance when there is more than three-level warning, reduce various dams in river channels, and closely monitor them.
However, the workers said that they had been working here for more than 20 days before the rainstorm, and no personnel from relevant departments came to check the drainage of the river.
Mr. Chen, who lives near the spillway of Guojiazui Reservoir, said that he didn’t receive a short message from Zhengzhou Flood Control Headquarters until 5: 31 am on July 21, reminding him that there were major security risks in Guojiazui Reservoir, and people in many areas needed to be transferred immediately. Mr. Wang belongs to the staff in the transferred area, but he said that there was no staff to inform him how to transfer, nor did he receive a notice from the unit requesting to stop work.
Mr. Shi’s children are attending kindergarten, and parents have not received the news of kindergarten suspension. On the morning of July 20th, as usual, he sent his children to the kindergarten on the west side of Chengdong Road. A few hours later, the accumulated water brought by the heavy rain flooded into the kindergarten, and the school informed the parents to pick up the children. Mr. Shi’s mother was almost washed away by the flood when she went to pick up the children. Afterwards, he learned that the meteorological department had issued a red rainstorm warning the night before.
Almost everyone in this city is commuting normally. On the afternoon of July 20th, more than 500 passengers in the rush hour set foot on Metro Line 5. Soon, when the train passed between Tantan Temple and Shakou Road Station, the flood flooded into the carriage and the train was forced to stop. After nearly four hours of despair and rescue, some people were able to get away, but at least 12 people were killed, and some family members are still looking for their lost relatives.
On July 24th, the interface journalist came to the parking lot in wulongkou again. The gap opened by the flood has been blocked, but the messy scene in the parking lot is still there. On the open ditch in wulongkou across the road, there are many workers under construction. Except some building baffles have been removed, the cover plate on the river has been covered with a layer of green mat cloth. The workers said that concrete will be laid on the cover next. "No one asked us to stop."
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