Review several heavy rains in Beijing in recent years.

　　Using "Beijing rainstorm" as the key word, several obvious heavy rainfalls after 2010 were searched.

　　The first 721 rainstorm

　　From July 21 to 22, 2012, at around 8: 00, most areas of China were hit by heavy rain, among which Beijing and its surrounding areas suffered the strongest rainstorm and flood disaster in 61 years. As of August 6, 79 people have died in Beijing because of this rainstorm. According to the data of the disaster briefing held by the Beijing Municipal Government, the rainstorm caused 10,660 houses to collapse, 1.602 million people were affected, and the economic loss was 11.64 billion yuan.

　　721 Beijing rainstorm

　　There are several characteristics of rainfall in Beijing:

　　First, the total rainfall is rare in history. The average rainfall in the city is 170 mm, and the average rainfall in the urban area is 215 mm, which is the largest rainfall process since the founding of New China. The average rainfall in Fangshan, Pinggu and Shunyi is above 200mm, and the area with rainfall above 100mm accounts for more than 86% of the total area of this city.

　　Second, the long history of heavy rainfall is rare. Heavy rainfall has been going on for nearly 16 hours.

　　Third, the local rainfall intensity is rare in history. The largest rainfall point in the city is 460 mm in Hebei Town, Fangshan District, which is close to once in 500 years, and the largest rainfall point in the urban area is 328 mm in Shijingshan Mode, which is once in a hundred years. There are as many as 20 stations with hourly rainfall exceeding 70 mm.

　　Fourth, the huge history of local floods is rare. The maximum flood peak flow of Juma River is 2500 cubic meters per second, and the maximum flow of North Canal is 1700 cubic meters per second.

　　Conclusion and lesson: Every rainstorm should not just leave a hasty lesson, and every post-disaster reflection should not just stop at finding problems. In the opinion of experts, with policies, the key lies in implementation. Disaster prevention and mitigation should be a comprehensive project, and it is not possible to "treat the head and foot". It is necessary to dig deep into the root causes, comprehensively manage and combine prevention and control, and truly treat disaster prevention and mitigation as a century-old plan and a popular project. This is the way to cure the problem.

　　The impact of the July 21 rainstorm on Beijing was painful, causing 79 deaths. After the rainstorm, the Beijing Municipal Government started the formal transformation and reconstruction, aiming at protecting people's lives and property, and according to the principle of sponge city, transformed the city into a livable environment with no disasters and less disasters, and started the nationwide sponge city construction boom.

　　The second 720 rainstorm

　　July 20, 2016 rainstorm in Beijing refers to the heavy rainfall in Beijing from 1: 00 on July 19 to 6: 00 on July 21, 2016. The rainfall lasted for a long time, with a large total amount and a wide range. The total rainfall exceeded the July 21, 2012 torrential rain in Beijing. The city's average rainfall is 210.7 mm, and the urban area is 274 mm, forming a total of 3.3 billion cubic meters of water resources.

　　After four years, the rainstorm washed Beijing again. In the past four years, the water conservancy infrastructure built in Beijing has been tested and played a great role. It is understood that the rainstorm has formed a total of 3.3 billion cubic meters of water resources. Among them, from 8: 00 am on July 19, 2016 to 8: 00 am on July 21, 2016, Miyun Reservoir increased its water storage by 21 million cubic meters, and the municipal large and medium-sized reservoirs increased by 52.58 million cubic meters. The rainfall lasted for a long time, with a large total amount and a wide range. The total rainfall exceeded the July 21 torrential rain in Beijing. The city's average rainfall is 210.7 mm, and the urban area is 274 mm, forming a total of 3.3 billion cubic meters of water resources.

　　This rain lasted longer than the July 21 rainstorm, and the rainfall was larger, but the urban infrastructure withstood the test and effectively protected people's lives and property in the face of major natural disasters.

　　The third 812 rainstorm

　　On August 12, 2020, influenced by the southerly warm and humid airflow and the upper trough around the subtropical high, a regional heavy rainfall weather process occurred in Beijing-Tianjin-Hebei region. Heavy rain (≥50 mm) occurred in most parts of Beijing, and heavy rain (≥100 mm) along the mountain, accompanied by lightning and local short-term gale of magnitude 7 ~ 9. As of 8: 00 on August 13th, the average rainfall in Beijing was 69.4 mm, and the average rainfall in the urban area was 92.8 mm, which was the strongest rainfall process since the flood season in 2020, and it was also the first regional rainstorm process, with the maximum rainfall reaching 156.7 mm, which appeared in Shahe Reservoir in Changping.

　　812 rainstorm

　　The intensity and destructive power of this rainfall are less than the previous two.

　　The fourth 731 rainstorm

　　From July 29th, 2023, due to the combined effects of typhoon Du Surui's residual circulation, subtropical high, typhoon khanun's water vapor transport and topography, disastrous torrential rain occurred in Beijing, China and its surrounding areas. According to the Beijing Meteorological Observatory, the precipitation (mm) from 20: 00 on July 29th to 11: 00 on August 1st is 263.8 in the whole city, 239.1 in the urban area (north Korea, sea, abundant rocks, east and west), 452.6 in the southwest (doors and houses), 264.9 in the northwest (Yanchang), and 264.9 in the southeast (Tongda). The largest Fengtai Qianling Mountain in the urban area is 589.7, and the largest Changping Wangjiayuan Reservoir in the city is 744.8. The maximum hourly precipitation intensity of Fengtai Qianling Mountain is 111.8 mm/h (10: 00-11: 00 on the 31st).

　　As of 14: 00 on August 1, 2023, this round of heavy rainfall has killed 11 people, two of whom died in the line of duty during the rescue and disaster relief; Another 13 people lost contact.

　　conclusion

　　In the face of natural disasters, the strength of human beings is negligible. However, human beings can use collective strength to strive for the lowest loss in the face of disasters. Similarly, human beings can also make preventive plans ahead of time.

　　After experiencing great disasters, we should all learn from them, sum up experience, and strengthen our protective ability through technical improvement and improvement. Improve the accuracy of weather forecast, improve underground drainage facilities, improve the permeability of ground pavement materials, and prevent problems before they happen with the concept of refined urban governance, especially for drainage and flood discharge facilities in low-lying or waterlogged areas, so as to maintain the state of always online.