The difference between landslide and debris flow

It is important to enjoy the beautiful scenery when you are away from home, but there are often some natural and man-made disasters in reality. You need to be careful at this time, especially when you encounter landslides and mudslides, you must learn to distinguish them. The consequences are very serious. So today Bian Xiao will tell you, how do we identify it?

First of all, what are landslides and mudslides?

1. Landslide refers to the phenomenon that the soil layer or rock layer slides down the slope as a whole or dispersedly under the influence of river scouring, rainfall, earthquake, artificial slope cutting and other factors. Landslides are also called ground slides, and they are also commonly known as "walking the mountain", "collapsing the mountain" and "cutting the mountain" among the masses.

2. Debris flow refers to a special torrent with a lot of solid substances such as mud, sand and stones in valleys or hillsides under the action of surface water formed by precipitation, dam break or melting of snow and ice. Commonly known as "walking dumpling", "dragon" and "dragon".

What are the characteristics of landslides and mudslides?

Landslide is characterized by "sliding" along the slope, and debris flow is characterized by "flowing" along the ditch. Whether it is "sliding" or "flowing", it is the motion form of matter from high to low under the action of gravity. Therefore, the speed of "slide" and "flow" is restricted by the terrain slope, that is, when the terrain slope is slow, the movement speed of landslide and debris flow is slow; When the terrain slope is steep, the movement speed of landslide and debris flow is faster.

How to identify landslide and debris flow? -There were signs before it happened!

Although landslides and mudslides are sudden and destructive disasters, there are often some precursors that can help us judge whether disasters occur or not, so as to take quick and correct self-help methods.

As for whether the debris flow occurs, besides estimating the possibility of the debris flow according to the local rainfall, it can also be judged by some special phenomena: if the normal flow of the river (ditch) bed suddenly stops or the flood suddenly increases, and there are more firewood and trees, it can be confirmed that the debris flow has formed in the upper reaches of the river (ditch); If you hear the roar of the train or the low thunder coming from a deep valley or ditch, you should assume that a mudslide is forming and you must leave the dangerous area quickly. In addition, the dark sky deep in the valley, accompanied by roar or slight vibration, indicates that mudslides have occurred in the upper reaches of the valley.

Generally speaking, the precursors of landslides are: the revival of spring water at the foot of the slope at the front of the landslide, or the sudden drying up of spring water (well water), the sudden change of well water level and other similar abnormal phenomena; Transverse and longitudinal radial cracks appear in the middle and front of the landslide body, indicating that it has entered the state of imminent sliding; The soil at the toe of the landslide front appears uplift phenomenon, accompanied by the sound of rock fracture or shear extrusion.

Nip in the bud is the key!

(A) landslide identification basis

1. Geomorphic foundation: When round-backed chairs, horseshoe-shaped landforms or multi-level abnormal abutments appear on the slope, their shapes are obviously out of harmony with the surrounding slopes; There are depressions in the upper part of the slope, and the depth of the lower slope foot extending into the riverbed is greater than that on both sides; The sources of the two valleys turn and meet at the upper part of the slope; The above landforms indicate that landslides may have occurred in these areas. There are obvious cracks on the slope, which have been lengthened and widened recently; The house on the slope is cracked and tilted; There is soil squeezing at the foot of the slope, which often collapses; The above landforms may be the basis of landslide formation.

2. Stratigraphic basis: In areas where landslides have occurred, the types and occurrences of rock strata or soil are often obviously different from those of surrounding non-landslides. Compared with non-sliding slope, sliding rock or soil is usually disordered in sequence and loose in structure.

3. Groundwater basis: Landslide will destroy the unity of the original slope aquifer, leading to the change of groundwater flow path and discharge position. When it is found that the distribution of local slope is not harmonious with the distribution of spring points and seepage zones on the whole slope, and many springs or original springs suddenly dry up in a short time, it can be combined with other evidence to judge whether there is a landslide.

4. Vegetation foundation: the trees on the slope are staggered, which is generally the performance that the slope has experienced violent sliding; On the slope, the trunk of the tree bends downward and the upper part of the trunk keeps growing vertically, which is generally the result of slow sliding of the slope for a long time.

(2) Identification basis of debris flow gully

1. provenance: a certain amount of loose earth and stone must participate in the formation of debris flow. Therefore, there are a lot of broken and evacuated materials on both sides of the valley, and the landslides and collapses on both sides of the valley are obvious, and the vegetation is underdeveloped. Debris flow is easy to occur in valleys with strong soil erosion and slope erosion.

2. Topographic foundation: A large amount of soil and stones can be accommodated and transported in a valley that can store a large amount of water and maintain a high water flow speed. The upper reaches of the valley are surrounded by mountains on three sides, with steep slopes. The plane shapes of the valley area are funnel-shaped, spoon-shaped and leaf-shaped. The middle reaches of the valley are narrow, the gullies in the lower reaches are wide, the height difference between the upper and lower reaches of the valley is more than 300 meters, and the slopes on both sides of the valley are more than 25 degrees, which is beneficial to the formation of debris flow.

3. Water source foundation: Water provides dynamic conditions for the formation of debris flow. Local rainstorm-prone areas, reservoirs in danger of dam failure, downstream of ponds and seasonal melting areas of ice and snow have conditions to produce a large amount of running water in a short time, which is conducive to the formation of debris flows. Among them, the frequency of debris flow in local rainstorm-prone areas is the highest.

If a ditch is conducive to the formation of debris flow in terms of material source, topography and water source, it must be a debris flow ditch. The frequency, scale and viscosity of debris flow will change with the above factors. Gullies where mudslides have occurred are still dangerous in the future.

How to prevent landslides and mudslides?

In order to avoid landslides, in the frequent season of landslides, we should pay attention to listening to the local weather forecast and early warning information of geological disasters, and do not enter mountain valleys after heavy rain or rainy days. In rainy season, don't walk in steep slopes and places where dangerous rocks are prominent, and don't climb dangerous rocks.

When you are on a landslide, you should move to a safe zone such as a stable zone on both sides, and you are not allowed to run up and down on the landslide. When you are in a landslide or encounter a high-speed landslide, you can find an open place with a gentle slope to stay, but you must not be too close to houses, fences, telephone poles, etc.

The site selection of the project should try to avoid disaster-prone areas. Attention should be paid to avoid landslide induced by excavation, soil abandonment and drainage in engineering design and construction.

Don't panic if you suddenly encounter a mudslide. The following measures can be taken to avoid danger and seek rescue: in case of rainstorm or rainstorm in the valley, you should quickly move to a high place, and don't avoid or stay under a low-lying valley or steep slope. When you find a debris flow, don't run upstream or downstream along the ditch, but run to the slopes on both sides. Never cross a mudslide.

People who have been evacuated from the danger zone before the mudslide, don't rush back to their original places after the rainstorm stops, but wait for a while.

It is particularly worth mentioning that in the season with frequent mudslides (such as summer), don't go to areas with frequent mudslides. If you go, you should know the terrain in advance and arrange the evacuation route. When camping in the wild, you should choose the flat highland as the camp, and don't camp under the hillside with rolling stones and a lot of deposits or at the bottom of valleys and ditches.

Although landslides and mudslides are inevitable in mountainous areas, taking active defensive measures can reduce their harm.

I hope everyone will have more crisis awareness and safety awareness after reading the above contents, and I hope everyone can enter and exit safely.