Sel is a stormy stream in which there is a large concentration of rock fragments, stones and mineral particles. Their amount may exceed half the volume of all water present in it. A natural disaster - mudflow - suddenly appears in the basins of small mountain rivers. Most often, the main reason for its occurrence is a sharp melting of snow or intense rainfall.
General information
The consistency of the flow is an intermediate substance between the solid and liquid mass. Sel is a phenomenon that is relatively short-lived and lasts no more than three hours. Mostly occurs in small streams, the length of which does not exceed 30 kilometers.
Characteristics
The speed of such flows is in the range from 2 to 6 meters per second. This is due to their destructive effect. Sel is a stream that creates deep channels on its way. They usually contain small streams or are completely dry. The components that make up the stream accumulate on the plains in front of the mountains. The mudflow is characterized by movement in the form of a water shaft of its frontal part. Most often there is a row, which consists of alternating shafts. When the mudflow descends, the consequences almost always represent strong changes in the form of the channel.
Reasons for the appearance
Sel is a stormy natural phenomenon. The flow may appear due to the rapid melting of glaciers, seasonal snow massifs or prolonged and intense rainfall. Also, the cause of the occurrence can be the ingress of a huge number of fragments in the channel. Deforestation in the mountains is one of the main factors in the emergence of a stormy stream. Trees play an important role in preventing mudflows, as their roots hold the topsoil. In dry logs with a large slope and in the basins of small mountain rivers, destructive flows rarely occur. Mudflows can be classified. There are landslide-landslide, breakthrough and erosive types of nucleation of this phenomenon.
Foci
Potential places for the flow to occur are a basin or a section of the channel, if a large amount of loose material has accumulated in them. At risk are also areas where all the conditions for its accumulation, and certain areas of flooding are created. These foci have their own classification. There are potholes, cuts and places of dispersed formation of flows. The area of dispersed mudflow formation is considered to be steep exposed areas in which a large number of heavily destroyed rocks have accumulated. Such a focus has a branched and dense network of furrows. Directly in them is the process of formation of microcells and the formation of weathering products. Then all these elements are combined into a single channel.
Mudflow pothole
This phenomenon is a linear formation that cuts through forested, sod and rocky slopes. Usually they are composed of thin weathering crust. Such potholes are characterized by small depth and length. The angle of its bottom is more than 15 degrees.
Insert
This phenomenon is a powerful formation that has developed in an array of ancient moraine deposits. Mainly included in the general part of sharp kinks of the slope. In addition, such incisions often occur on such types of relief as: landslide, volcanic, landslide and accumulative. The size of mudflow incisions significantly exceeds the potholes. Their longitudinal profiles also differ. In incisions, they have a smoother outline than in potholes. The maximum depth of the first can exceed 100 meters. The catchment area of this type can reach 60 kilometers, while the volume of soil carried out in one stream is 6 million cubic meters.
Protection methods
Sel (photo flow presented in the article) has a huge destructive effect. To combat them, special structures are being built and measures are being taken to consolidate the vegetation and soil cover. The choice of protection method is based on determining the boundaries of the mudflow basin. Ideally, preventive measures should, at the very beginning of the nucleation of the flow, stop and weaken its effect. Forest planting in hazardous areas is considered the most radical method. This technique is able to divide the total flow into separate jets, reduce the total mass of water and adjust the flow. In the danger zone, it is necessary to increase the stability of the slopes, and also with the help of earthen shafts and upland ditches to intercept and divert mudflows. The most effective use of dams in the channels. They are structures made of concrete and stone, the task of which is to delay part of the solid materials of the stream. The dams are intended to direct the mudflow to a shore less prone to rupture. Also an effective way of protection is the construction of guide dams. They are able to direct the flow in the right direction and significantly weaken its effect.