MODELS AND ALGORITHMS FOR OPTIMAL RELEASE OF POPULATIONS FROM RIVER VALLEYS AND FLOODPLAINS

Significant flooding of urbanized areas of river valleys and f loodplains during floods poses a serious potential danger to their populations due to the low-lying location of settlements and the low density of the road network. The lack of detailed guidelines for the formation of adaptive schedules for organized evacuation of the population during floods, taking into account the properties of the relief, spatial distribution of the population and the road network of specific territories, creates an additional potential danger. This paper presents the general task of finding schedules for organized transport evacuation of the population of river valleys and floodplains that minimize the magnitude of the aggregated life risk, in the presence of a forecast by a river hydrographer based on hydrodynamic calculation of the moments of flooding of settlements and road sections, as well as a series of its private versions for various evacuation situations. Algorithms for finding the minimum number of evacuation vehicles that ensure the safe evacuation of the entire population with known values of the evacuation situation parameters are presented. An algorithm for constructing effective schedules that ensure partial evacuation of the population in conditions of shortage of evacuation vehicles is also proposed. The numerical implementation of the proposed algorithms was carried out for the territory of the northern part of the Volga-Akhtuba floodplain. Geoinformation and hydrodynamic modeling was carried out using the software package “Web-ECOGIS”, designed for modeling emergency situations on rivers and reservoirs, as well as for modeling seasonal f loods. The package uses modern GIS technologies, OpenMP, MPI, and CUDA parallel computing technologies. The multilayer digital maps in this package include layers of relief, riverbed system, socio-economic infrastructure, as well as numerous maps of flooding in a wide range of parameters of the catastrophic hydrograph of the Volga hydroelectric power station. As a result of a series of computational experiments, it has been shown that the implementation of the proposed algorithms for finding optimal evacuation schedules for the population of the northern part of the Volga-Akhtuba floodplain during floods can significantly reduce the number of evacuation vehicles that ensure the safe evacuation of the entire population. The limits of the number of vehicles ensuring the safe evacuation of the entire population of the territory are found, depending on the values of the hydrograph of the Volga hydroelectric power station and the start of the evacuation. Effective schedules have been built to ensure partial evacuation of the population in conditions of a shortage of vehicles.