RECONSTRUCTION OF DANGEROUS SURGES IN THE NORTHERN CASPIAN BASED ON DIGITAL ELEVATION MODELS AND HYDROLOGICAL MODELING

The results of reconstruction of dangerous surges in the Volga delta and the Northern Caspian Sea using hydrological modeling tools are presented in the article. High-precision digital models of the Volga delta and Northern Caspian Sea have been developed based on topographic and hydrographic maps. The control was carried out in manual mode. The special algorithm described in the article was developed to take into account the peculiarities of the structure of the channels. The HEC-RAS model has been verified for a number of hydrological scenarios with different variants of the roughness coefficient. The redistribution of the Volga runoff along the branches was taken into account in the calculations, the optimal points for setting the river flow rates and level were proposed. For reconstruction, the choice of dangerous surges in the 20th and 21st centuries was carried out on the basis of information from the scientific literature and according to the data of river level gauges. A total of 26 cases were identified for which calculations were performed. Maximum flooding maps for each case are built. Some features of the Volga delta flooding have been identified. In addition to level fluctuations in the northern part of the Caspian Sea, the inundation area is significantly affected by the discharge in the river Volga – the greater the river discharge – the larger is the flooded area during surges of similar dynamics. The maximum flooded area was 17.5 thousand km2 for the surge in 1991, at the annual flood runoff, the minimum – for the 1940s and 1960s (less than 10 thousand km2), when surges with the maximum level below −27 meters were identified.

digital elevation model, digital terrain model, geographic information system, numerical modeling, Caspian Sea, Volga River