Geographical aspects of origin of flood mudflows

The main part. Floods occur at unexpected times, causing significant damage to the national economy. It is also noteworthy that such incidents often occur in mountainous areas. However, floods, their origin and genesis have not yet been studied in depth. In many cases, information about them and short lines of damage caused by them are saved only after the flood. Sometimes the causes of floods cannot be fully disclosed. The causes of floods in recent years have been significantly enriched by rapid changes in the water regime of mountain rivers, as well as by the problems of accurately predicting their state in the context of global climate change. This, in turn, requires an in-depth analysis of the factors causing floods, a study of their genesis and determination of their causes.

Before determining the genesis of a flood, it is necessary to have information about its types. Flood waters are classified as rocky, muddy and muddy. When classifying them, the granulometric composition of the floodplains is taken into account. In general, their strength can also be determined by the types of flood waters. The stronger the flood flow, the larger the size and size of the rocks in its sediments and, conversely, the softness of the sediments, the smaller the volume, the weaker the flood flow. However, classifying floods by type also helps determine their genesis. For example, heavy rainfall on steep slopes creates a mostly turbid and rocky mixed flow. They also have trees. The flood currents that form in the plains are mainly a mixture of turbid and shallow streams, the strength of which is not very great.

First of all, the necessary conditions for the occurrence of flooding are necessary. These include the relief structure of the terrain, the nature of the rocks, the degree of overgrowth, the state of the territory in relation to meteorological factors (exposure), the state of existing natural and man-made hydrographic objects on the territory, the degree of contamination of the territory. anthropogenic load on hydrographic objects, etc.

Relief structure of the area. This factor largely determines the nature of the flood runoff. This is because the destructive force of flood currents is associated with this very factor. Flood currents often form in mountainous and foothill areas and cause large losses. In this case, it will be very difficult to determine their genesis depending on the location of the floodplain. This is due to the fact that their ovens are usually located at very high altitudes. The Ecological Atlas of Uzbekistan identifies 9 of these floodplains in the mountainous and foothill regions of Uzbekistan. They are located in the Nurata, Chatkal, Gissar ridges.

The nature of the rocks. The condition of the rocks also determines the nature of the flood flow. Washed-out rocks not only increase the amount of muddy sediments in the flood flow, but also cause landslides. Also, the presence of unreinforced rocks leads to the presence of a large amount of solid materials of various sizes in the composition of flood currents.

The flow rate is determined by the absolute height, slope and position of the rocks in which the floodplain is located. As a result of floods, the process of cracking develops in the regions. Intense precipitation is actively falling in the foothills and mountainous regions. According to AN Nigmatov (2005), the specific water consumption and the volume of surface runoff under various conditions are directly proportional to two parameters of precipitation - their kinetic energy and the maximum flow rate from the watershed to the bottom of the slope [2].

Land cover level. Plants usually slow down the process of erosion of mountain rivers and slopes, prevent landslides, and strengthen terraces. On slopes overgrown with trees, the movement of surface currents slows down and the strength of flood currents decreases.

The state of the region in relation to meteorological factors (exposure). The impact on the environment is one of the most important factors in the location of floodplains. The fact that the exposition enters the path of air masses causes a large amount of precipitation to fall here. This causes flood flows associated with heavy rainfall. The aforementioned 9 flood centers in Uzbekistan are also prone to this. The location of the floodplain in the Shohimardon river basin is also closely related to exposure. At the confluence of the Oksna river valley with the Shohimardon river, 1 km south of Kadamjay, there is a floodplain, where the western route of air masses turns into a narrow gorge, which forms a closed valley with Katrontov on the right bank of the Shohimardon river. This valley in a small area is a favorable condition for the accumulation of air masses and the formation of intense precipitation.