How close is the mountain floods from us?

At around 15:30 on August 13, 2022, Longconggou, Pengzhou City, Chengdu City, Sichuan Province, suddenly developed mountain floods. As of now, this sudden disaster has caused 7 people to be killed and 8 people were injured. It was caused by the short rainfall in the short period of time.

The trapped crowd pictures in the mountains and floods Source: Surging News

Just a few days later, from August 17th to 18th, heavy rainfall appeared in Xining, Qinghai. On the 18th, a flood disaster occurred in Datong County, Xining City. As of 12:00 on the 18th, 16 people had died and 36 people lost contact.

From the rise of the river to the raging flood, the person experienced has only a few seconds of reactions and the best time to escape. In the face of such a tragedy, in addition to sadness, we started to think deeply, is the flood ignored by us? How close is the mountain flood from us?

What is mountain flood?

Mountain flood refers to the total name of the upstream floods formed along the rivers and rivers in mountainous areas (including mountainous areas, hills, and tangers) in mountainous areas (including mountainous areas, hills, and gangsters).

The flood disaster refers to the harm caused by the outbreak of mountain floods, including the flood of the stream and the critical casualties, property losses, infrastructure destruction, and environmental resource destruction caused by the flood of the stream and the landslide. A sort of.

It should be noted that mountain floods are not just water, they are often accompanied by sediment, stones, branches, weeds, etc. Therefore, it is difficult to get away once people fall into it.

At the scene of the flood, you can see the turbid water flowing with sand pictures source: publicdomainpictures.net

What are the characteristics of Chinese flood disasters?

Due to the East Asian monsoon area and spanning the multi -latitude zone, the distribution of precipitation space and space in my country is very different, the inter -annual changes are high, and there are significant regional differences in flood disasters.

At the same time, as a country of mountains, the area of ​​mountainous areas (mainly mountains, hills, and plateau) accounts for about two -thirds of the total area of ​​my country's land. In addition, complex geological and geologicalforms, diverse climate and dense population have led to the mountain flood disasters in my country. There is obvious geographicality.

In the history of Chinese history, mountain flood disasters are concentrated in the low mountain hilly plain area and the mid -to -low mountain plateau basin area of ​​the southeast, accounting for about 60%of all the flood disasters, of which the number of affected people in the southwest is very [8]. In the top ten provinces (2011-2019) in the flood disaster, Sichuan, Yunnan, Hunan, and Guizhou accounted for No. 1-4 [11], respectively.

Mountain floods are mostly caused by heavy rain, so the flood disasters have strong seasonality, mainly concentrated in the summer flood season (May-September), and the highest frequency occurred in June-August.

Mountain floods are sudden. Due to the steep slope of the mountains, the mountains and rivers are dense, and the rainfall is rapidly transformed into a impactful surface runoff after a short -term heavy precipitation. Due to the large flow rate and destructiveness, it can quickly disaster and cause serious harm. In May 2015, the heavy rainfall in Leibo County, Sichuan Province only triggered the flood for only 20 minutes.

When the flood disaster occurs in the late night people, it will bring greater safety hazards and further aggravate losses. From the evening of June 9, 2011 to the 10th in the morning of the 10th, a 300 -year encounter (6 hours of rainfall reached 275.6 mm) raid Hunan Linxiang City, which led to a large flood and mudslides disaster, causing 12 people to die 7 people disappeared.

When the floods, urban waterlogging, and landslides caused by extreme rainstorms are concurrent, major natural disasters can also be caused. On July 20, 2021, the mountain flood geological disasters in the western mountains of Zhengzhou killed 251 people and 44 towns and villages were affected.

Moreover, the mountain floods are prone to repeated disasters. The same county repeatedly encounters a maximum of 7 times a year. For example, in 2013, Yanjin County, Yunnan, repeatedly encountered 5 mountain flood disasters, and the short period of time was only 10 days.

It is precisely because of the high frequency, fierceness, fast disaster, great harm, easy to recur, and when the floods come out, it is often a sorrow.

Source of the scene of the flood geological disaster in the western mountains of Zhengzhou: References [7]

Mountain flood disasters behind the scenes

Sudden rainstorms in mountains will not cause flood disasters, nor is the heavy rain that people feel subjective to cause mountain floods in the local area.

First of all, mountain floods often occur in places with large heights, steep slopes, and depth of valley depths near the streams near the ravine and the intersection of Shuanghekou. At the same time, most of the geology near these places is the weathered rock layer and soil with little penetration strength. Its corrosion resistance is weak, and it is easy to soften and disintegrate when it comes to water.

Once the upstream encounters a strong precipitation and the water flow increases, the balance of the soil is easily destroyed. In addition, the terrain conditions at the ravine make the meter runoffs quickly gather. While gathered, it will bring soft soil along the way. In this way, the strong water flows with sediment to form a flood disaster.

However, because the upstream and downstream may not be precipitated at the same time, even if the upstream has formed a mountain flood, the downstream will reduce the vigilance because it does not feel the rainfall. By the time he heard the roar of the valley, when he turned his head, he had been involved in the water wall.

The red dot is the Longconggou that occurs in Pengzhou floods in Sichuan. At the foot of the mountain, the water flow from the mountains is gathered here. It is a place with a high risk of mountain floods.

In the long run, behind the emergence of mountain floods, there is also the "soil loss" as a "black hand". For a long time, over -development of mountain hill areas, and the construction of projects such as steep slope wasteland will cause damage to the mountain itself. Due to the changes in the terrain of the mountain, the natural vegetation was destroyed, the virgin forest was fell, and the effect of losing its natural water source, making the flood easily develop.

The rapid growth of urban construction land and the continuous expansion of urban boundaries forced the rise of construction models such as "cutting mountains and building land", "climbing", and "reclamation", which directly led to the risk of continuously growing mountain disasters. For example, the number of disasters that induce landslides and collapsed mountains in Guangdong to build houses in Guangdong account for 90.3%of the province's geological disasters [17].

Guangdong has potential geological disaster threats to cut off the slope and build a house in danger point. Source: Sina.com

Is the flood disaster ignored?

Compared with other natural disasters, flood disasters occupy the largest proportion of global natural disasters, which is also well known. Taking our country as an example, in 2020, the proportion of flood disasters reached 56.8%[2].

Source of the loss of flood disasters in China from 2009-2018: References [2]

From 1991 to 2020, my country ’s annual dying or missing population due to flood disasters or missing more than 60,000 people died. The annual average of 160.4 billion yuan in direct economic losses, totaling about 4.81 trillion yuan [18].

Since 2000, the number of Chinese flood disasters and the proportion of the number of deaths in flood disasters.

Unlike the deep impression of large flood disasters, most of the floods are small and medium -sized disasters, so they are easily ignored.

However, the small and medium -sized flood disasters have a strong sudden, difficult to predict and engineering measures, and have a high disaster. The number of people who die in my country each year due to the number of flood disasters account for about 70%of the total number of flood disasters [16] It is also one of the countries with the worst flood disaster.

From 2011 to 2019, there were four large-scale flood disasters in my country, with 1178 small and medium-sized romance disasters, accounting for 96.2%of the total number of floods, causing 2,353 deaths, accounting for 74.4%of the total death population [11].

Not only in my country, the World Meteorological Day World Meteorological Organization (WMO) in 2020 also pointed out that in the past few decades, the casualties caused by global flood disasters have increased, accounting for about 85%of flood disasters [3].

The "power" of mountain floods is not only in developing countries. Among the 139 countries investigating and statistics, the loss caused by flood disasters is ranked in the top 2 countries in various types of natural disasters to 75.5%, while the United States and the European Union Developed countries such as countries, South Korea, and Japan are also listed [15].

From 2011 to 2019, the number of mountain flood disasters in different levels of the country and the number of deaths (left) and the monthly distribution of the flood disaster (right) Picture source: References [11]

What do we need to do?

Due to severe loss of life and property, the warning and prevention of mountain floods have always been a major and urgent strategic needs in the national disaster prevention and mitigation plan.

At present, my country has initially built a mountain flood disaster defense system covering 2058 counties and an area of ​​4.63 million km2. Early warning.

After the implementation of mountain flood disasters, the average dying population was 333 people in the disaster in 2011 to 2020 due to the average dying population, which was 70 % compared with the average 1179 people annually from 2000 to 2010 [19]. It is very difficult.

Mountain flood disaster meteorological warning picture Source: China Meteorological Bureau

First of all, the warning of mountain floods needs to rely on accurate mountain sudden rainstorm early warning, and the forecast of heavy rain depends on high -precision monitoring materials. my country's flood disaster defensive water and rain and rain conditions are still based on ground monitoring stations. With the rapid development of technologies such as communications, informatization, and artificial intelligence, comprehensive monitoring technologies such as satellite radar, X -bands and ground stations need to be used in the future. [12].

Secondly, the forecast errors of sudden rainstorms in mountains and insufficient accuracy. To achieve fixed -point and quantitative hotspots and difficulties in international research [13].

In the future, the influence mechanism of numerical models on mountain, heavy rain and its suddenness, further tap the theoretical knowledge of sudden rainstorm formation and development of mountains, and improve the accuracy and timeliness of the time, regional and intensity forecasting and early warning of heavy rain. Essence

Only in this way can we achieve accurate forecasting of mountain floods in the future. Only by walking the "last mile" of the flood forecast can we avoid more tragedies.

What will happen in the future of mountain floods?

As soon as he heard the mountain floods, people thought in a subconscious area. However, with the increase of abnormal climate, more and more "incredible" areas in areas will increase.

Taklama Gang Desert suffered a flood picture source: Phoenix.com

In the context of global climate change, due to the heating of the climate, the increase in temperature will lead to the increase in water vapor content in the atmosphere, increased water circulation process, and increased precipitation [1].

The response of extreme precipitation to heating is stronger than the annual precipitation, which makes most parts of my country, even the Northwest region, has increased average precipitation, precipitation intensity, extreme strong precipitation and continuous precipitation in the future [14]. This will inevitably increase the possibility of future flood disasters. The risks of flood disasters in my country and even the world's regions may show a continuous increase.

Although with the continuous investment in the construction of my country's flood prevention, the number of deaths caused by flood disasters has shown a reduction in the number of direct economic losses, and the affected population and crop disasters will increase in the future. The top priority.

On the second day of the Pengzhou flood disaster, some people still ignore the dissuasion and possible dangers to "check in", which just shows that the public participation of disaster prevention and mitigation is still long -term. It is hoped that everyone can use this tragedy as a warning to raise their awareness of disaster defense and risk aversion.

Photo source: Tencent.com

Longmen Mountain Town Government's "cherish life, please do not go down the river" marked sign source: Observation Network

Produced: Popular Science China

Author: half laziness (Beijing Tao Shiyan Meteorological Development Foundation)

Producer: China Science Popularization Expo

references

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