ИСТИНА

On the Northern Dvina River, floods are the most serious natural disaster. The main feature of their formation is ice jams that occur in the river bars and in places of narrowing of the channel.To simulate the characteristics of flooding, a set of models consisting of three blocks was used: the stochastic model WGEN by A.N. Gelfan, ECOMAG flow formation model by Yu.G. Motovilov and STREAM-2D two-dimensional hydrodynamic model by V.V. Belikov et al.The stochastic WGEN model contains embedded generators that describe sequences of meteorological variables with yearly, monthly and daily time averaging.The series of meteorological observations with a duration of 42 years at 35 stations were used as initial data for stochastic modeling. Based on the actual data, statistical values were calculated (mathematical expectation and standard deviation for each simulated value, as well as the correlation coefficient between precipitation values and air humidity deficit). In addition, using the WGEN model based on the Monte Carlo method, artificial 1000 years series of average daily values of temperature, precipitation intensity and a deficit of air humidity were generated.The obtained values of meteorological parameters were used as input data in the ECOMAG (ECOlogical Model for Applied Geophysics) flow formation model which includes: ECOMAG mathematical model; the specialized geographic information system (GIS); the database of archive data on soil characteristics, vegetation, land use, pollutants; the database of operational hydrometeorological data; the information on the characteristics of the territory; the control shell that links the GIS and databases and allows for calculations.For a detailed study of the water flow at the peak of the simulated flood, the two-dimensional hydrodynamic model STREAM-2D was applied. The model is based on the solution of the Saint-Venant equation, known as the shallow water equation. The equation is obtained by integrating over the depth of the Navier-Stokes equation, provided that the horizontal scale is much larger than the vertical one.The calculation through two-dimensional hydrodynamic model was carried out for the period of 3 months, from April 1 to June 30. The maximum level mark when simulating the passage of the most adverse hydrograph was 57.36 m at the hydrological station of Velikiy Ustyug.