RESEARCH OF COASTAL WASHING PROCESSES

ABSTRACT

The article presents the results of an experimental study conducted on the study of watercourse processes in the lower water intake area of the Amudarya River Basin without a dam. The article also presents the factors that lead to the washing of the shores in different water flows, and recommendations for strengthening the shores.

АННОТАЦИЯ

В статье представлены результаты экспериментального исследования, проведенного по изучению водотоковых процессов в нижнем водозаборе бассейна реки Амударья без плотины. Также в статье представлены факторы, приводящие к размыву берегов различными потоками воды, и рекомендации по укреплению берегов.

Ключевые слова: русло реки, русловые процессы, береговая эрозия, водопотребление, скорость течения воды.

Keywords: riverbed, riverbed processes, coastal erosion, water consumption, water velocity.

Entrance. The rapid development of agriculture sharply increases the demand for water for irrigated lands specific to the conditions of the region. In addition, the development of hydropower in the region leads to a redistribution of the time and amount of use of existing water resources. All this caused the hydrological regimes of rivers to change. In this situation, global warming on the planet is increasing the shortage of water resources in Central Asia. In order to provide the people and agriculture with the required amount of water in time in the conditions of the complex water resource shortage, it is time to improve the efficiency of the operating conditions of the hydraulic structures, which were built mainly for irrigation purposes in the past centuries. In the performance of these tasks, there is sufficient information about increasing the efficiency of water extraction from rivers, changing the morphometry of the bed and the hydrodynamic elements of the stream in the area of influence of the structure, and the speed of the processes that occur as a result of the interaction between the bed and the stream. It is desirable to have a base.

Natural deformations mainly occur as a result of changes in the hydrological regime and flow regime of the river, and develop along the cross-section and along the length of the riverbed with certain dynamics. Of course, climate change is expanding the scope of these types of deformations. The instability of riverbeds mainly depends on the change in the distribution of sediments along the length of the riverbed and the change in the saturation of the flow with sediments. Such development of processes in Uzan often interferes with the economic activities of mankind. In many cases, the deformations of the river cause great damage to the national economy. For example, siltation of the bottom of the riverbed and elevation of the elevation mark can lead to a rise in the water level and flooding of productive lands and settlements.

The purpose of the study. The goal of our study is to study the results of the research of the Amudarya damless catchment area and evaluate the state of the Amudarya riverbed and the occurrence of riverbed processes as a result of unstable flow.

Results. The variability of the river bed complicates the operating conditions of the river water intake facilities, and there are constant washing deformations and washing away of fertile lands. It also washes away protective dams that are being built (Fig. 1).

Figure 1. The course of river processes in Amudarya

Looking at the nature of changes in the average monthly parameters of the water level in the Amudarya, it should be noted that the distribution of water without dams to the KMK takes place in large fluctuations of water levels.

The flow of the river is unevenly distributed, and the total amount of flow 80% of it flows in the period of high water and 20% in the period of low water. The largest annual fluctuation of the water level varies in the range of 2.2 - 3.05 m, the largest value corresponds to the period of high water level, and the hydrographs also have many peaks characteristic of Amudarya. 16 ÷ 17 times, frequency 3 ÷ 4.

It is equal to the values from 10 ÷ 12. The maximum consumption and levels are observed in July of the year, and by August, the levels and consumption begin to decrease gradually. The period of low water lasts from October to the end of March. During this period, the level and flow are stable, and the hydrograph has 1-2 peaks in April as a result of floods or hot days.

In order to assess the processes taking place in the river bed, depth measurement works were carried out and the structure of the river bed was determined. Based on the results of depth measurement in the longitudinal and transverse cuts of the walls, a graph of the dynamics of the bed of the stream was made.

An increase in the flow of water into the channel causes the depth of the flow of water moving in the channel to decrease and the width of the channel to increase. This situation, in turn, leads to the emergence of a dynamic balance. The expansion of the channel width leads to an increase in the width of the flow front and ensures their transport. The change in depth was compared in the water catchment area of KMK.

Researching the dynamics of river sediment distribution and applying its results in practice is of great scientific and practical importance. The design of hydrotechnical structures and channels requires taking into account the mode of deposition or transport of sediments and the effect of the constructed structure on the conditions of sediment flow.

In the course of our research, we used reduced and detailed methods of water consumption in the analytical calculation of turbid waste consumption. Turbidity was analyzed by taking samples at different depths along 6 vertical lines in 3-4 reservoirs in the Amudarya basin, and a graph representing the distribution of turbidity by depth was constructed.

Figure 2. Terrain reconstruction with elevation markers and coastlines graphically

The calculation of the flow structure in the lower area of water intake without a dam of the KMK was carried out with the help of software. As a basis for numerical modeling, several types of calculations were identified and built. The lower part of the main water intake section of the Amudarya without a dam is based on topographical data [2; 120-b], the area of flow movement in this area is DX=36.8 m in the direction of movement, with the exception of the 4th block in the entrance section, where the step DX was 22 m, 24 m, 28 m and 33 m) and the cross-flow direction was taken as DY=20 m. The estimated length of the fragment was 2 km downstream from the water intake.

DX and DY steps were increased by 10% when moving away from the damless intake to the main canal. In the case of uneven types, the height of the bed of the uneven type was not determined using topographical data, and the height of the bed of the uneven type was accepted as if the cells were of a flat type. This allowed the centers of even and uneven types to overlap. In the used method of determining the height of the river bed, the initial cells of the flat types in the lower part of the water intake area of the Karshi main channel are divided into four types, and the height of the river bed in each of them is assumed to be equal to the height marks of the initial flat type. done. The program shows the flow direction and distribution of surface velocities based on the data (velocities and depths) measured at the site. This gives an opportunity to determine where the planned processes will take place.

Conclusion. It was found that the average speed of the flow in the area of the main water intake structure without a dam of KMK is several times higher than the non-washable speed determined for the soils of the Amudarya river basin. Sudden changes in flow rate and level, high speed, saturation of the stream with nanoparticles moving and suspended along the bottom of the bed and sudden changes in their migration character cause the bed to constantly change and deformation processes in the plan. increasing speed. As a result of the dumping of sediments from the cleaning of the nanos entering the opposite Main channel, the riverbed is narrowing in the lower part, and the left bank is being washed away. Based on this result, it was recognized that there is a need for more accurate research in the future.

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