Practice of early warning

In 2006, the forecast and early warning software platform was upgraded, which realized the automatic closing of the forecast and early warning curve and increased the landform background of the forecast and early warning base map. Based on the samples of geological disasters in 2005, the prediction and early warning standards were revised. A new form of forecasting and early warning information has been added. When a level 5 alarm is issued, the forecast and early warning information is sent in the form of mass SMS by mobile phone. The data transmission line has been improved, and the SDHL dedicated line of China Telecom has been rented, with a bandwidth of 2M/ s, which ensures the stable, safe and fast data transmission between early warning business departments.

3.5. 1 Analysis of geological disasters in flood season

According to statistics, in the flood season of 2006 (May to September), there were a total of geological disasters10210/,including 88 landslides137, collapses 12974, 404 mudslides and 30 ground collapses. Mainly distributed in Hunan, Guangdong, Fujian, Jiangxi, Guangxi, Anhui, Chongqing, Sichuan, Yunnan and other provinces (autonomous regions and municipalities), and no geological disasters occurred in Beijing, Shanghai and Ningxia (Figure 3.37). * * * caused 665 deaths (including missing persons), 405 injuries and direct economic losses of 3.5 billion yuan.

Figure 3.37 Comparison of the number of geological disasters among provinces (autonomous regions and municipalities) in flood season in 2006.

3.5.2 Analysis of the Relationship between Geological Disasters and Rain in Flood Season

3.5.2. 1 data base

Rainfall data come from meteorological impact assessment data (several major rainfall processes) of meteorological department and daily live rainfall of 755 rainfall stations. Rainfall stations are rare, but they can basically reflect the rainfall situation in 74 secondary early warning areas in China, but their accuracy is limited.

Geological disaster data (casualties or economic losses of more than 6,543,800 yuan) have exact occurrence time, landslides, mudslides, etc. Caused by rainfall, there were 875 incidents (places).

General situation of precipitation in flood season in 3.5.2.2 in 2006

According to the data of meteorological department, the national average precipitation in 2006 was less than normal, but the heavy rainfall process and local rainstorm were frequent, and the intensity and frequency of landing typhoons were high (Table 3.2; Figure 3.38).

1)No. 1 strong typhoon "Pearl" landed in Guangdong on May 18, 40 days earlier than the historical average typhoon landing time;

2) The duration of low-pressure circulation reached 120h after the No.4 strong tropical storm "Bilis" went inland, which was rare in previous years;

3) When the No.8 super typhoon "Sang Mei" landed, the maximum wind force near the center reached 17 (60m/s), which was the strongest typhoon landing in Chinese mainland in recent 50 years;

4) * * * Six typhoons landed in Chinese mainland and Taiwan Province Province, especially in July and August, five typhoons landed one after another, with an average of 9d 1 time, which is the second highest frequency in history.

Distribution characteristics of geological disasters caused by rainfall in flood season in 3.5.2.3 in 2006

Figure 3.39 shows the histogram of geological disasters caused by rainfall and the time distribution of rainfall (the dotted line shows the monthly average rainfall). June and July have the most geological disasters, accounting for 33.9% and 35.2% of the total respectively. September was the least, accounting for only 3.0% of the total, and May accounted for 15.8% of the total. There is a certain correspondence between the number of geological disasters and the corresponding monthly average rainfall (right axis).

Table 3.2 Monthly Precipitation in Flood Season in 2006

(According to China Meteorological Bureau)

Figure 3.38 Comparison of annual average rainfall in China (according to China Meteorological Bureau, 2006)

Figure 3.39 Geological disasters and rainfall time distribution caused by rainfall in flood season in 2006.

Figure 3.40 shows that Guizhou, Yunnan and Anhui account for more than 5% of the total geological disasters; Fujian, Guangxi, Hubei, Sichuan, Jiangsu and Shaanxi account for more than 1% of the total; Hunan and Zhejiang provinces accounted for more than 10% of the total, especially in the flood season of 2006, the geological disasters in Hunan were extremely serious, accounting for 43.2% of the total.

Fig. 3.40 Spatial Distribution of Geological Hazards in Flood Season of 2006 by Province

Typical rainstorm process and geological disasters in flood season in 3.5.2.4 in 2006.

1) On May 18, Typhoon Pearl landed on the coast of Guangdong. Affected by the typhoon, the rainfall in eastern Guangdong, most of Fujian and southern Zhejiang is100 ~ 300mm, with some areas exceeding 300mm. Fujian and Guangdong provinces caused different degrees of geological disasters respectively, of which 13 caused great losses, resulting in 22 deaths or missing persons (Figure 3.4438+0). The number of people affected by the disaster accounted for 5.4% of the total in May, and the number of people killed and missing accounted for 53.7% in May. During the typhoon landing, geological disaster clusters are mainly concentrated in the typhoon rainfall center, which has the characteristics of "sliding when it rains".

2) Three heavy rainfall events in June affected Fujian, Hunan, Guizhou and other provinces. On June 2nd ~ 10, rainfall 100 ~ 300mm occurred in most parts of southern China and southern Guizhou, resulting in five provinces (regions) of Zhejiang, Guangxi, Guizhou, Hunan and Yunnan 12 1 times, resulting in 15.

From June 13 to June 18, the process precipitation in southern China is generally 50 ~ 150mm, and locally exceeds 150mm, resulting in 30 geological disasters in Zhejiang, Anhui, Hunan, Guangxi and Guizhou provinces (regions), resulting in 2/kloc.

From June 23 to June 26, thunderstorms and heavy rains occurred continuously in central Hunan, causing 5/kloc-0 cluster geological disasters, resulting in 28 deaths, accounting for 14% of the total disasters in June and 18.0% of the total deaths in June. Among them, in Group 6, Qingshan 'ao Village, Huxingshan Town, Longhui County, Shaoyang City, where the catastrophic flash flood caused the debris flow disaster on June 25th, the precipitation observed by the meteorological post in this township was 273.7mm from 20: 00 to 25: 00/6 on the 24th.

3) During the three heavy rains in July, Hunan Province was among them, and the geological disasters were the most serious. Geological disasters in Hunan Province accounted for 74.4% of the total disasters in that month (Figure 3.43).

Fig. 3.41the range of major rainfall processes and the distribution of geological disasters in may 2006 (thematic data of Taiwan Province province are temporarily missing).

Figure 3.42 Scope of main rainfall process and distribution of geological disasters in June 2006 (thematic data of Taiwan Province Province is temporarily missing).

Fig. 3.43 Scope of main rainfall process and distribution of geological disasters in July 2006 (thematic data of Taiwan Province Province is temporarily missing).

On July 13, the severe tropical storm "Bilis" landed in Yilan County, Taiwan Province Province, landed again in Xiapu, Fujian Province on June 14, and weakened and disappeared in eastern Yunnan on June 18, lasting for * * * 5 days with a rainfall of 50-200mm. From July 14 to July 18, Fujian, Hunan, Guangdong and Yunnan provinces caused a total of 195 geological disasters, with 309 people dead and missing, accounting for 22.3% of the total disasters caused by rainfall in flood season and 92.2% of the deaths and missing in that month.

On July 24th, "Meg" landed on the coast of Taitung County, Taiwan Province Province, and landed again on the coast of Jinjiang, Fujian Province on the 25th. Meg weakened rapidly after landing, and weakened and disappeared in Jiangxi on the 27th, with a cumulative rainfall of 100 ~ 200mm. Eight geological disasters occurred in Fujian, Hunan and Jiangxi provinces, resulting in eight deaths or disappearances, accounting for 7.5% of the total disasters and 2.4% of the deaths in that month.

From July 7 to 10, heavy rains and floods occurred in Liuyang, Xinhua, Loudi and Xiangxiang, Hunan Province. There were 42 heavy rains in the province, including 8 heavy rains. This process is the biggest heavy rainfall since the flood season in 2006, which triggered a series of group geological disasters. From July 7th to12nd, 37 geological disasters occurred in Hunan province, accounting for 12.0% of the total disasters in that month, and no casualties were caused.

4) On August 10, the super typhoon "Sang Mei" landed in Zhejiang. From August 10 ~ 12, there were serious geological disasters in Fujian and Zhejiang provinces, and 58 geological disasters with great losses occurred, resulting in 37 deaths or disappearances (Figure 3.44). When the typhoon landed, geological disasters mainly occurred in the typhoon rainfall center.

5) In September, the national average precipitation was less than normal, and some provinces experienced heavy rain. For example, Nanjiang and Tongjiang counties in Sichuan province were hit by heavy rain from September 2 to 4, but did not cause large-scale group geological disasters.

Relationship between Early Warning Division and Meteorological Station in 3.5.2.5

By plotting the actual rainfall stations and geological disaster points on 74 national early warning zoning maps, the distribution of disaster points in each early warning area can be counted (Figure 3.45, Figure 3.46; Table 3.3). Among them, C 1 1 and C 13 have the most geological disasters, which are 136 and 12 1 respectively. Take C 1 1 early warning area as an example.

Fig. 3.44 Scope of main rainfall process and distribution of geological disasters in August 2006 (thematic data of Taiwan Province Province is temporarily missing).

Figure 3.45 National Actual Rainfall Stations, Geological Disasters and Early Warning Areas in 2006 (there is no special data of Taiwan Province Province).

Fig. 3.46 C 1 1 Rainfall Points and Geological Disasters in Early Warning Area

Table 3.3 Distribution of Disaster Points in Geological Disaster Warning Area

(1) Relationship between rainfall and geological disasters

Geological disaster points are1136 disaster points in the area of C1,and the rainfall data of the rainfall station closest to the disaster point are selected. Define and select two rainfall parameters: the rainfall of the day, that is, the rainfall of the disaster day (from 20:00 the day before to 20: 00 the day before); Accumulated rainfall in the previous period, that is, the rainfall in a rainfall process before the disaster (continuous rainy days in the middle), two rainfall parameters and disaster point distribution maps are drawn respectively (Figure 3.47 and Figure 3.48).

Fig. 3.47 C 1 1 distribution map of accumulated rainfall and geological disasters.

Fig. 3.48 C 1 1 regional daily rainfall and geological disaster distribution map

There were three cluster disasters caused by heavy rainfall (local rainstorm) in this area, and the rainfall on that day reached 50.6mm, 142.3mm and 2 17.8mm respectively. The previous rainfall was 0mm, 68.85mm and 2 1 1. 15mm respectively. Draw the daily rainfall of the day and the previous rainfall on the same map, and you can get a general rule: if the previous rainfall is not considered, the daily rainfall will reach at least 50mm, and if the previous rainfall reaches at least 120mm, there is a greater possibility of disaster (Figure 3.49).

Figure 3.49 Geological hazard possibility discrimination

When diagonal lines are used in the figure, disasters above this line (disaster points account for 92.2%) are more likely to occur, while disasters below this line (disaster points account for 7.8%) are less likely to occur.

The approximate formula of geological disasters is

Regional early warning method of geological disasters in China and its application

When k≥0, the possibility of geological disasters is greater;

When k < 0, the possibility of geological disasters is relatively small. Among them: Rsum is the previous cumulative rainfall, that is, the cumulative rainfall in a rainfall process before the disaster (with uninterrupted rainy days in the middle); Rd is the rainfall on the day of geological disaster (from 20: 00 the day before to 20:00 the day before).

(2) Analysis of rainfall patterns and geological disasters

Rainfall patterns that cause geological disasters can be divided into three types: one is continuous rainfall; The second is local heavy rain; The third is the combination of continuous rainfall and local heavy rain. Three rainfall stations (typical rainfall patterns) in the early warning area of C1/KLOC-0 are selected for analysis (the histogram shows daily rainfall and the dotted line shows disaster occurrence).

1) continuous rainfall pattern: According to the records of No.57874 weather station (Changning, Hunan) from July 8 to 28, we can see three intermittent continuous rainfall processes, each of which did not last long (3-4d) and the rainfall was not large (less than 50mm). Geological disasters only occur when the accumulated rainfall reaches a certain amount, that is, the occurrence of geological disasters is generally mainly caused by the accumulated rainfall in the previous period, not the rainfall of the day (Figure 3.50).

Figure 3.50 Geological disasters caused by continuous rainfall

2) Type of local rainstorm: from June/KOOC-0/5 to June/KOOC-0/9, there was no rainfall on June/KOOC-0/5 and June/KOOC-0/6, and local rainstorm (50.6mm) occurred on June/KOOC-0/7.

Figure 3.5 1 Geological disasters caused by local rainstorm and rainfall

On June 17, 8 geological disasters were caused by local rainstorm, which mainly occurred on the day of rainstorm. The geological disasters caused by this rain type are concentrated on the day of local rainstorm, and the rainfall forecast is difficult, with low accuracy, high possibility of causing geological disasters and strong suddenness, which is also a difficult point in geological disaster early warning.

3) Continuous rainfall+local rainstorm: Meteorological Station No.57972 (Chenzhou, Hunan Province) recorded a minimum daily rainfall of 0.0 1mm and a maximum daily rainfall of 2 17.8mm from July 5 to June 7. Rainfall-rainfall type is a combination of continuous rainfall and local rainstorm, which is easy to cause group geological disasters (Figure 3.52).

Figure 3.52 Geological disasters caused by continuous rainfall and local rainstorm.

In the previous continuous drizzle, the soil moisture content of the slope gradually increased, but due to the small daily rainfall and insufficient accumulated rainfall, no geological disaster was caused; However, from July 15 to July 17, heavy rainfall occurred continuously, resulting in a large number of disasters and clustering. The rainfall peaked on July 16, but there was a disaster on July 15. Because on the day of 15, a lot of disasters occurred and a lot of energy was released. It was not until July 16 that more rain came and the disaster was reduced.

It can be seen that the laws of geological disasters caused by different rainfall values and different rainfall patterns are different. Therefore, in the prediction and early warning of geological disasters, we should not only pay attention to the difference of critical rainfall caused by geological disasters in different regions, but also pay attention to the role of rainfall patterns in prediction and early warning.

In the early warning duty work, it is necessary to analyze the rain pattern first, and then calculate the rainfall, that is, first analyze and judge the rain pattern of this rainfall, analyze the law of its disaster (mainly affected by the rainfall of the day or the accumulated rainfall in the previous period), and then calculate and analyze according to the critical rainfall values in different regions, so as to judge the possibility of geological disasters.

3.5.3 Field Investigation of Geological Disasters-Field Investigation of Loess Landslide in Yili, Xinjiang

3.5.3.1"7.3" large loess landslide in Wuer Tamiz ditch, Qilewuzeke Township, Tekes County.

At about 3: 00 a.m. on July 3, 2006, a landslide occurred in Urtamis Gully (N43 12' 39 ",E8 1 29' 47") in Wuzeke Township, Tex County, Yili Kazakh Autonomous Prefecture, Xinjiang. It is about 260m long and 400m wide, with an average thickness of about10m (Figure 3.53). Two herders were affected by the disaster, resulting in the death of 597 sheep and no casualties.

There has been no disaster in this area since records began. However, there are many disasters in the whole Urtamis gully.

Landslide occurred on the shady slope on the south side of gully, and the landform type belongs to the landform of high mountain and loess ridge in erosion structure. Above 2000m above sea level, the terrain slope is 30 ~ 40, with steep slope at the foot and gentle slope at the upper part. The water system is developed and the cutting is strong, forming deep gullies. The relative height difference is large, but the grass is rich, which is an excellent summer pasture. The loess cover is thick and there is no bedrock exposed. Material composition of landslide: mainly loess soil layer. The vegetation type is mainly turf, with coverage of 80% ~ 90%. The landslide was caused by two consecutive days of moderate to heavy rain, but there was a lack of meteorological records. There is a disaster prevention plan for landslides, and herders have been mobilized to move and avoid them many times. A few days before the disaster, a puddle was found on the upper part of the landslide to remind herders. Before the landslide that night, the dog slammed the door to wake the owner and evacuated in time.

In addition, ancient loess landslides are also common along the Urtamis gully. Among them, you can see both the ancient landslide landform and the landslide that just happened; At the same time, we can see the potential hidden danger points of the landslide that is gestating, and the cracks are clearly visible. It can be called "Loess Landslide Museum" and its geological environment is very fragile. In case of heavy precipitation, landslides may occur at any time.

Fig. 3.53 The whole picture of the "7.3" large loess landslide in Wuertamisigou, Qilewuzek Township, Tex County.

Typical geological disasters in Gong Liu County, 3.5.3.2

Geological disasters in Gong Liu County are mainly concentrated in Mocher Township and Jigelan Township.

(1) Xiaokuole Sayigou, Alar Village, Mohe Township1March 23, 990 landslide.

1On the morning of March 23rd, 990, a landslide occurred in Xiaokuole Sayigou (N43 13' 26.8 ",E82 42' 9.2") in Alar Village, Mohe Township, Gong Liu County, Yili Kazakh Autonomous Prefecture, Xinjiang, with a height difference of about 40m, a width of about 100m and an average thickness of over 6544. The front of the loess landslide pushed downstream for about 100m, and part of it rushed through the ravine, burying the houses opposite the ravine, resulting in 8 deaths, including sheep 130, horses 10 and houses 1 room.

Geomorphologically, it belongs to the dome-shaped low mountain in the denudation accumulation massive uplift mountain, with an altitude of 1700 ~ 2600m and a relative height of1000 ~ 200 m. Due to long-term weathering and flowing water erosion, it forms a round mountain with inconspicuous hills. The hillside is gentle, the original terrain slope is about 28, and the ravines are densely covered. The surface of the mountain is covered with gravelly loess with a thickness of several meters to more than ten meters, and the vegetation is developed. There is running water in the valley at present. The direction of the valley is about 320, and the main sliding direction of the landslide is about 40.

The loess cover is thick, and no bedrock outcrop is found. Landslides are mainly composed of gravelly loess-like soil cover. The vegetation type is mainly mountainous grassland, with a coverage rate of 80% ~ 90%.

Landslides are caused by melting snow and rainfall, but there is a lack of meteorological records. At the same time, it is also related to the erosion of river valleys. There are precursors before the landslide. There is a spring in the middle of the landslide. Three days before the landslide, the spring water became turbid, and some people heard strange sounds in the morning.

(2) On April 9, 2003, a landslide occurred in Dammohegou.

On April 9, 2003, a landslide occurred in Da Mocher Gully (E43 10' 12 ",N82 49' 13.7") in Mocher Township, Gong Liu County, Yili Kazakh Autonomous Prefecture, Xinjiang. The landslide has a height difference of about 124m, a width of about 30m and an average thickness of about 5m.

The loess landslide killed 8 people and damaged more than 200 trees. When landslides occur, the energy is very large. Some trees were uprooted and some trees were interrupted. The landform is similar to that of Xiaokuo Lesayigou, and it belongs to the dome-shaped low mountain in the denudation and accumulation massive uplift mountain, with an altitude of1700 ~ 2,600 m and a relative height of1000 ~ 200 m. Due to long-term weathering and flowing water erosion, a round mountain with low hills is formed. The original terrain slope of the upper part of the landslide is about 35, and the lower part is 26 ~ 27. The loess is covered with thick and unclear thickness, and no bedrock outcrop is found. Landslides are mainly composed of gravelly loess-like soil cover. The vegetation development type is mainly Chinese fir, with a coverage rate of 80% ~ 90%.

Landslides are caused by melting snow and rainfall, but there is a lack of meteorological records. Cracks appeared on the right bank of the river and were listed as hidden dangers. As a result, there was a landslide on the left bank without any sign of hidden danger.

(3) The hidden danger of large landslide in Xiao Mo, Mohe Township.

The landslide disaster is located in Xiao Mo Helgou (N43 13' 52 ",E82 42' 29") in Arele Village, Mocher Township, about 50 kilometers southeast of the county. The crack is located near the top of the west bank slope. They were discovered in May 2000, gradually infiltrated in 2003, and gradually increased and expanded. Two years ago, there were only two cracks. Now the cracks are distributed in a straight line along the ridge, with a strike of 330 and a slope angle of 60. The original 37 households have moved. The slope height difference is 300m, and there are convex slopes on both sides of the split mountain. The cracked hillside is concave, the top of the mountain is round and gentle, and it becomes steeper down the slope. The slope of cracking is about 25, and then it becomes steep to 30.

The slope is composed of Cenozoic strata. The lower part of the slope is Paleogene mudstone and sandstone, and the upper part is in unconformity contact with the semi-cemented gravel of Middle Pleistocene. The top and slope are covered with middle-upper Pleistocene loess, which is composed of silty loam.

Typical geological disasters in xinyuan county, 3.5.3.3

Xinyuan county is one of the hardest hit areas of geological disasters in Yili. According to reports, in recent years, dozens to hundreds of geological disasters such as landslides and mudslides have occurred every year in xinyuan county. Most of them are loess landslides and mudslides caused by loess landslides.

(1) Ancient Landslide Group in Qiabhemuye Village, Bestobe Township

The ancient landslide group is located in Qiabhe Animal Husbandry Village, Bestobe Township, xinyuan county. It is a loess ancient landslide group, located on the south bank of Chabu River, extending about 20 kilometers from Kesang-Baorankele. Ancient landslides are mainly located in the foothills, with a gentle slope of about 20, and landslides have occurred many times in history. Since 2002, the activity has been strong, and cracks have gradually appeared in the trailing edge, and there is a trend of gradual development. Its threat targets are mainly excellent grassland resources and scattered herders (Figure 3.54).

Fig. 3.54 Ancient landslide in Qiabhe Animal Husbandry Village, Bestobe Township.

(2) East landslide of Qiabhemuye Village

On May 4th, 2003, a loess landslide occurred in Muye Village (N43 19' 34.8 ",E83 20' 4 1. 1") on the south bank of Chabu River in xinyuan county, Yili Kazakh Autonomous Prefecture, Xinjiang. Horizontal sliding 1000m or more, with an average width of about 150m and a thickness of about 5 m. The landslide buried the house 1, resulting in 2 deaths, 1 missing, 6 houses destroyed and 201/80 livestock buried. Landslides slide on a large scale, accompanied by ground sound and air pressure. The original terrain slope is about 30, and now the slope is about 20. The bedrock is clastic rock. Landslide is mainly loess soil. The vegetation type is mainly mountainous grassland, with a coverage of 70% ~ 80% (Figure 3.55). Landslides are caused by melting snow and rainfall, but there is a lack of meteorological records.

Fig. 3.55 East Landslide of Qiabhemuye Village

(3) Landslides, mudslides and dammed lakes in the upper reaches of Zeketaigou.

In March, 2002, a large-scale landslide occurred on the left bank of the mountain at the upstream of Zeketai 10.5km in xinyuan county, Xinjiang, which triggered a mudslide. The landslide area is about 66. 15× 104m2, and the earth generated by the landslide is about 960× 104m3. The generated debris flow flows downstream along the main ditch, forming a pile with a height of 8 ~ 15m and a width of 80 ~ 120m in the main ditch. The landslide dammed lake has a maximum water depth of 13m, an area of1.33x104m3 and a storage capacity of 90.4x104m3 (Figure 3.56). Landslides have caused serious losses to Zeketai Town.

Fig. 3.56 The panorama of Zeketai landslide, with a dammed lake formed at the front edge.

Geomorphologically, it belongs to shady slopes, gullies and concave slopes in middle and low mountainous areas. The loess is thick and severely weathered, and the front of the slope is cut by the river. Earthquake intensity Ⅷ. The stratum is mainly loess and loess-like soil, and no bedrock is exposed. Mainly silty clay silt and silty light loam, with poor physical and mechanical properties, which is very beneficial to the formation of landslides.

Landslide is mainly loess soil. The type of vegetation development is mainly mountainous grassland, with a coverage rate of 80% ~ 90%. The reason for the landslide is continuous precipitation. At present, the reservoir water level formed in front of the landslide has been effectively controlled, and the upstream and downstream water inflow and outflow are basically balanced. However, landslides and debris flow accumulations are still in an unstable state, and they are still one of the major geological disasters in xinyuan county, directly threatening the lives of 20,970 people and the property safety of 253 million yuan in the downstream areas.