Being interested in events in the country and the world, looking through news feeds, we often see photos, videos of natural disasters caused by mudflows. There are more and more disasters in the world: whether global warming is to blame, or maybe human activity, or does our planet itself go through certain "catastrophic" periods of its history for some other reason, but the consequences of cataclysms are always the same. Frightened people, refugees, lost homes and property, dead cattle, disfigured natural landscapes, which only yesterday seemed like a fairy tale, and today resemble pictures from films on the theme of the apocalypse. So how is the mud formed, what can be done to avoid death and destruction or to make the consequences of rampant disaster minimal?
What is sel in nature?
The word has Arabic roots. Translated means "rapid flow". Muddy mud masses rushing at great speed sow death, sweep away everything in its path - buildings, natural landscapes, together with all their inhabitants, from animals to humans. The mudflow contains many solid inclusions: large and small stones, rock particles, which, by the way, may be more than half of the total mass. Many settlements in the mountains exist for a long time, have a long history, happily avoiding natural disasters, but something unusual and extraordinary happens in nature (stormy and prolonged rainfall, sharp warming, coupled with especially violent melting of snow, a glacier in the mountains) - and disaster is approaching. The disruption of the elements usually does not last long, for several hours, but this is more than enough to inflict permanent damage on nature and people over several years, as, for example, this happened after the mudflow in Georgia descended in 2013. Then, due to the disaster, the movement was completely paralyzed. The mudflow in Taba also caused quite serious damage (we will talk about it a little later).
Characteristics
Debris flow has a very high speed. Mud masses often appear unexpectedly, preventing them from taking sufficiently operational measures to protect the population and nature. Debris flow, including hard rock, sweeps at a speed of 2-4 to 4-6 meters per second. As a result of the descent, the surrounding landscape can take on completely different outlines: stones literally in just a few hours break through new channels of rivers and streams, a layer of debris and dirt covers the fertile foothill plains used for growing crops and grazing livestock. Blooming valley becomes dead and unsuitable for living and activity. Debris flow can descend in several stages, with each new wave further increasing the size of the disaster.
What are the causes of this natural phenomenon?
- Stormy and prolonged rainfall. If local “global floods” did occur, then they looked just like that, with torches descending from the mountains, people dying and buildings.
- Abrupt warming, seasonal or off-season, which can cause the melting of snow and glaciers. The villages below the glacier are always at increased risk.
- In areas with a large slope, a significant part of the soil with debris may collapse into the river bed and, thus, block the watercourse, direct it along a different, unexpected path, and provoke an avalanche.
What can serve as additional factors provoking a catastrophe?
The roots of the trees well strengthen the upper layers of the soil, preventing it from moving even under the influence of heavy rainfalls or weathering, therefore thoughtless cutting of forest stands is one of the main factors that increase the threat of natural phenomena of this kind. Mudflows for reasons of occurrence are divided into three groups: as a result of erosion, breakthrough and landslide.
Where are potentially dangerous foci located?
In the long term, any section of a mountain river, where soil and rock are easily transported by water flows, can become dangerous. It can be cuts or potholes, as well as foci of dispersed mudflow formation.
Classification of foci
Potholes are formations on the slopes that cut rocky, soddy and other surfaces, they are small in length and depth and do not pose a danger until a stream appears that can lead to rock movement. Insert - a formation based on moraine deposits associated with abrupt elevations. They are very ancient in origin. Young cuts may appear as a result of recent volcanic activity, as well as as a result of landslides, landslides. The incisions are larger than the potholes in depth and length. Distributed mudflow formation can occur in steep mountain areas, where a lot of rock fragments, weathering products are concentrated. Such surfaces, significant in area, may appear as a result of a recent earthquake, an active tectonic process. The surface of these foci is dotted with furrows, in which mudflow products gradually accumulate, which, under certain conditions, can merge into a single channel and bring down their power on objects located on the slope.
How to prevent avalanches?
Since one of the main reasons for the flow of mudflows is the loss of forest plantations, one can try to solve the problem by forest planting. Hydrotechnical structures (ditches, earthen ramparts, tracing) that divert potentially dangerous flows can also give a considerable positive result. The installation of dams on the path of dangerous riverbeds and streams will delay part of the mass rushing from the slope, which will somewhat weaken its destructive potential. Any other structures (pits, pools, dams) will also reduce the risk of natural disaster, it is important to strengthen coastlines and prevent their additional erosion, especially if buildings are located on the banks. Pavement often suffers from mudflows, for the protection of which it is advisable to build trays (stone or reinforced concrete) above or below the road in high-risk places.
The most famous avalanches and their consequences recorded by historical science
- From August 17 to 18, 1891, a large mudflow came down in Tyrol, in the Austrian Alps: the wave reached a height of 18 meters, a huge area was covered with a thick layer of mudflow.
- Los Angeles suffered on March 1, 1938, killing more than 200 people.
- On July 8, 1921, a stream hit Alma-Ata (now Alma-Ata), several waves brought 3.5 million square meters to the city. m of solid material.
- In 1970, a catastrophe occurred in Peru, as a result of mudflow activities, more than 60 thousand people died, and 800 thousand became refugees, lost property, remained homeless.
