Zhouqu catastrophic debris flow

Middle school geography textbooks teach rough knowledge. Gansu Governor's Mansion 1.600 km, including all landform types except the sea in China. From north to south and from east to west, the climate is very different. As for Zhouqu County, which is bordered by Sichuan Province and belongs to the monsoon region, the annual rainfall is about 400-800 mm. ..

The place where the mudslide happened this time was in Zhouqu County, and the time was about 10 in the afternoon. The causes of catastrophic debris flow are:

1. Terrain factors. The basic topographical structure of Zhouqu County is that the ravine is deep, and there is a river between the two mountains. The county is built on the floodplain, and this debris flow pours into the county from the towering north valley.

2. Human destruction of the environment. Zhouqu is called "Jiangnan of Gansu" because of its rich virgin forest. Since 1950s, the forest coverage rate has dropped from 67% to 20%. 198 1 year, a serious mudslide disaster occurred in Zhouqu. Since 1985, the amount of logging has been decreasing and the afforestation plan has been strengthened. However, due to perennial drought and previous deforestation, the yield of newly planted trees is very low. Since 200 1, Zhouqu has started to build Daxing Hydropower Station on Bailong River and its tributaries. However, if we want to bomb the hydropower station for land acquisition, it will loosen the rock mass, destroy the vegetation, and cause new landslides. The river channel will be blocked with waste slag and piled up randomly in the river channel to provide loose solid materials for debris flow. At the same time, gold mining is also closely followed.

I won't say much about the impact of the Wenchuan earthquake.

The causes of heavy casualties are:

1. Insufficient weather information. According to Southern Weekend, the occurrence of debris flow is related to weather forecast. The weather forecast that day said that the rainfall in Zhouqu County was about 10mm, which was also in line with the actual situation, but the rainfall in mountainous areas reached more than 90 mm (nearly a quarter of the annual rainfall)! Although someone was on duty in the relevant area, it was not reported because the rainfall in this area was not outstanding. When the mudslide was discovered, Zhouqu County had lost power and could not be contacted.

2. Time factor of disaster. It was afternoon 10, and everyone in the small county should have gone to bed, and there was not much rainfall in the county at that time. Of course, they will think that nothing will happen.

3. Failure mode of debris flow. Debris flow and flood damage buildings differently. Debris flow is a huge soil flow mixed with sand and gravel, and buildings are knocked down by impact, not damaged by soaking. It is precisely because of the soil flow that people are buried firmly, and people can't breathe, causing a lot of deaths in an instant. So this time, the number of people affected by the disaster is small, but there are many deaths, which is very different from earthquakes and floods.