4.1. Lack of Strict and Practical Measures at the Highest Warning Level

According to the tenth press conference on flood tide dominance in Henan province on August 2, the total number of deaths was 302, of which 292 were in Zhengzhou, 7 in Xinxiang, 2 in Pingdingshan, and 1 in Luohe. Of the 292 deaths in Zhengzhou, 189 deaths were caused by floods and mudslides, 54 were caused by collapse houses, and 39 were caused by drowning in basements, garages, underground pipe galleries, and other clandestine spaces. Of the 39 deaths caused by deep water system in belowground spaces, 14 were along Zhengzhou Metro Line 5 and 6 were in the Jingguang North Road Tunnel, on July 20, which attracted public attention. We analyze these two cases in detail to learn lessons on emergency reply in central urban areas. Zhengzhou Metro Line 5 was constructed on 18 December 2014 and ran an air-load test on 29 December 2018. As of 14 May 2021, the total length of the channel was 40.7 kilometer, and it had a entire of 32 stations, all belowground. This is the lone circular line of the existing Metro lines, as shown in Figure 15. Connections to the downtown area and the surrounding areas are made by transferring to other lines. It has the largest casual passenger capacitance of the seven existing Metro lines on weekdays, according to the datum from the Weibo of Zhengzhou Metro [ 28 ], as shown in Figure 16 On July 20, serious ground waterlogging occurred around the Wulongkou parking area on the line, caused by intemperate rain. At approximately 18:00 in the haste hour, water gushed across the retaining wall of the entrance and into the main wrinkle area, which resulted in a train barricade between the Shakou Road station and the Beach Temple station, shown as a black line in human body 15. More than 500 people were stranded [ 29 ]. On the lapp day, some entries to early stations on the trace were closed successively ; the times are besides labeled in trope 15. At 17:00, the emergency reaction level in Zhengzhou was upgraded to the highest charge. At 18:42, on the Weibo of Zhengzhou Metro, it was announced that the whole Metro system was closing down. Line 5 was out of avail until September 14.

3/s and 0.5 m3/s, respectively, there are three pumps at each station, which are triggered automatically by a certain water depth [ Jingguang North Road Tunnel is a separate of the Jingguang Expressway system, which is in the south incision of the north–south expressway. structure was started on 17 December 2009, and it opened to traffic on 28 April 2012. The full length of the tunnel is 1.8 kilometer, composed of a bury section of 1.36 kilometer and an open incision of 475 megabyte, and the utmost height difference between the ground and the tunnel plate is about 9 m. The depth of land urine is 11.8–15.7 m, and the historical highest level was at a depth of about 10.0 m. This burrow is approximately 300 m away from the west square of the Zhengzhou Railway Station, and contributes to distributing the pass passengers promptly. The drain system in the tunnel is designed to drain away the water system from the open section in the showery season, the ground water brought into the tunnel by vehicles, the daily blush effluent, fire effluent, and a little escape of water. This arrangement is composed of three parts : a revoke slope is set at the capture to block the background water in the showery season. a orthogonal drain ditch is set on the correct side of the lane, and two clandestine pump stations are set to the west of the tunnel, as shown in Figure 17. With a design return time period of 50 years and a flow capacity of 0.52 m/s and 0.5 m/s, respectively, there are three pumps at each station, which are triggered automatically by a certain water depth [ 30 31 ] .2 along the Jingguang Road, draining it into Jinshui River and Xionger River with a flow capacity of 2.8 m3/s and 7.3 m3/s, respectively. Some of the main problems of flood control and drainage were discussed in detail a decade ago in [2 around the tunnel was one of the most waterlogged areas in Zhengzhou, and when the standing water could not be discharged by the drainage systems, it would flow toward the lowest area; (3) the water levels of Jinshui River and Xionger River were high, which was not conducive to drainage; (4) the flow capacity of the ground drainage system was much higher than that of the two pump stations in the tunnel drainage system. The early drain organization is designed to drain away the ground water from an area of about 2.78 kmalong the Jingguang Road, draining it into Jinshui River and Xionger River with a menstruate capacity of 2.8 m/s and 7.3 m/s, respectively. Some of the main problems of flood control and drain were discussed in detail a decade ago in [ 30 ] : ( 1 ) the long distance and big depth of the buried incision were the concealed factors leading to stalled and flood vehicles during the showery temper ; ( 2 ) the area of 6.75 kmaround the burrow was one of the most boggy areas in Zhengzhou, and when the standing body of water could not be discharged by the drain systems, it would flow toward the lowest area ; ( 3 ) the water system levels of Jinshui River and Xionger River were high, which was not conducive to drainage ; ( 4 ) the flow capacity of the ground drain system was a lot higher than that of the two pump stations in the tunnel drain system.

At about 16:00 on July 20, vehicles started to be blocked at the south die of the tunnel, and ground urine flowed from confederacy to north into the burrow half an hour belated. At the fifth weigh conference on deluge control in Henan Province on July 26, it was stated that the deep water level was about 6 m, and 6 × 106 m3 of water was discharged. A entire of 247 vehicles were pulled out from the Jingguang Road Tunnel after it was drained by 30 high-octane pumps operating over five days for 24 h/day.

From July 18, warnings of big rain were posted on “ Zhengzhou Meteorology ” which is the official Weibo of Zhengzhou Meteorology Bureau [ 32 ]. At 21:59 on July 19, 06:02, 09:08, 11:50, 16:01, and 21:32 on July 20 and 00:25 on July 21, the Zhengzhou Meteorology Bureau issued seven crimson warn alerts for a rainstorm, which was the highest warning level and entail that the precipitation in the follow 3 h would amount to more than 100 millimeter. According to [ 33 ], the designed life of the main structures of the Metro was 100 years, and the drain capacity was the rain amount in the 50-year recurrence period. In the “ Zhengzhou City of Urban Rail Transit Operation and Management Measures ”, released in 2013, it was stated that the operation unit could suspend the line operation or the operation of some road sections in the event of natural disasters and austere meteorologic conditions that badly affected the operational guard of the urban rail transit system if measures could not be taken to ensure safe operation, and that this should be announced to the public in good time. According to Zhengzhou Meteorology, the hourly and casual precipitation in this rainstorm were probable to occur once in a thousand years, exceeding the designed drain capacitance of Metro Line 5 and the Jingguang North Road Tunnel. however, there are respective lessons to be memorize. first, the emergency response should be feasible. In the “ Henan Province Meteorological Disaster Prevention Regulations ”, released in 2009 and revised in 2020, it was stated that the meteorologic stations affiliated to the competent meteorologic authority are in commit of forecast and warning of black weather conditions, and they should report to the local politics and the competent meteorologic authority immediately and notify the relevant authorities. In the case of major meteorologic disasters, the local governments and relevant authorities should, in accordance with the early on warn flush and the hand brake plan for meteorologic disasters, take the necessary emergency response measures such as closure, business suspension, class abeyance, and traffic manipulate in a timely fashion. There is a gap between the highest rainstorm warning issued by the competent agency and the emergency decisions made by the governors, which should be bridged in drill. Once the highest-level warn has been issued, the countermeasures should be executed rigorously and immediately, quite than in the mannequin of recommendations. For exemplar, after the crimson warning signals issued on July 19 and early on on July 20, notices regarding closure, business abeyance, class suspension, and traffic operate should have been issued to avoid people being exposed to the rainstorm. second, an early warning arrangement should be installed around areas that may potentially be waterlogged. In the showery season, early warnings should be issued on the vane, television receiver, broadcasts, and cellular telephone phones, and specially on the electronic screen on the road, or gates should be installed at intersections to stop vehicles from entering or to shut down Metro operation, based on the waterlogging situation at the lowest orient, the calculate precipitation, and the drain capacity. This should be developed as an automatic procedure in the future. relatively, the measures adopted in the pandemic were more appropriate since the governors and the public understand the importance and the measures had been put into exercise respective times in 2020 .

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