Devising a procedure to calculate and analyze parameters for passing the flood and breakthrough wave taking into consideration the topographical and hydraulic riverbed irregularities

Abstract

It has been established that the most likely period of breakthrough wave occurrence is the time of spring flooding or heavy rain when water-head facilities are subjected to significant loads that lead to the collapse of their individual elements or the entire structure. In addition, the possibility of man-made accidents that can occur at any time cannot be ruled out. It has been proven that breakthrough wave formation depends on the nature of the destruction or the overflow through a water-head facility. For the study reported in this paper, a model of the kinematics of riverbed and breakthrough flows was used, which is based on the equations of flow, washout, and transport of sediments that are averaged for the depths of the stream. The differential equations describing the nonstationary flow averaged for depth are solved using the numerical grid system FST2DH (2D Depth-averaged Flow and Sediment Transport Model), which implements a finite-element method on the plan of a riverbed's topographic region. These tools are publicly available, which allows their wide application to specific loads and boundary conditions of mathematical models. The construction of an estimation grid involving the setting of boundary conditions and the use of geoinformation system tools makes it possible to simulate the destruction of a culvert of the pressure circuit and obtain results for a specific case of an actual riverbed and a water-head facility. It has been established that there is a decrease in the speed of wave propagation along the profile, from 3 m/s to 1 m/s. The impact of bottom irregularities, the effect of floodplains, and the variety of bottom roughness have also been assessed, compared to the results of their calculation based on one-dimensional models given in the regulatory documents. Hydraulic calculations were carried out taking into consideration the related properties of the main layer of the floodplain, which consists of peat accumulations, and the heterogeneity of the depths and roughness of floodplain surfaces of soils. It has been established that there is almost no erosion of supports in the floodplain zone in this case. It was found that as the distance between the flow and breakthrough intersection increases, there is a decrease in the height of the head from 2.1 m to 1.25 m.

Devising a procedure for integrated modeling of riverbed shape in the area of bridge crossing in order to avoid dangerous washing erosion

“…The first attempts to use such calculation systems are described in work [7], in which a numerical model of the kinematics of riverbed and flood flows was built, which made it possible to calculate the parameters of the flood passage and the breakthrough wave. It is also possible to determine their influence on the formation of erosion of underbridge structures, taking into account the factors of topographic and hydraulic conditions on the river.…”

“…Our review of the literature [1][2][3][4][5][6][7][8][9][10][11] revealed that in the cases of solving complex problems of studying riverbed processes for the practical purposes of designing bridges and other important hydraulic structures, it is necessary to use and improve numerical methods that make it possible to simulate hydromorphodynamic processes in riverbeds. Therefore, it is expedient to study the specific problem of river processes, namely the hydromorphodynamics of bottom and bank changes, through the integrated application of modern computer technologies with the use of GIS for the grid approximation of the calculation area and analysis of the calculation results.…”