Modeling the Territorial Structure Dynamics of the Northern Part of the Volga-Akhtuba Floodplain

Abstract

The subject of our study is the tendency to reduce the floodplain area of regulated rivers and its impact on the degradation of the socio-environmental systems in the floodplain. The aim of the work is to create a new approach to the analysis and forecasting of the multidimensional degradation processes of floodplain territories under the influence of natural and technogenic factors. This approach uses methods of hydrodynamic and geoinformation modeling, statistical analysis of observational data and results of high-performance computational experiments. The basis of our approach is the dynamics model of the complex structure of the floodplain. This structure combines the characteristics of the frequency ranges of flooding and the socio-environmental features of various sites (cadastral data of land use). Modeling of the hydrological regime is based on numerical shallow water models. The regression model of the technogenic dynamics of the riverbed allowed us to calculate corrections to the parameters of real floods that imitate the effect of this factor. This made it possible to use digital maps of the modern topography for hydrodynamic modeling and the construction of floods maps for past and future decades. The technological basis of our study is a set of algorithms and software, consisting of three modules. The data module includes, first of all, the cadastres of the territory of the Volga-Akhtuba floodplain (VAF, this floodplain is the interfluve of the Volga and Akhtuba rivers for the last 400 km before flowing into the Caspian Sea), satellite and natural observation data, spatial distributions of parameters of geoinformation and hydrodynamic models. The second module provides the construction of a multilayer digital model of the floodplain area, digital maps of floods and their aggregated characteristics. The third module calculates a complex territorial structure, criteria for the state of the environmental and socio-economic system (ESES) and a forecast of its changes. We have shown that the degradation of the ESES of the northern part of the VAF is caused by the negative dynamics of the hydrological structure of its territory, due to the technogenic influence the hydroelectric power station on the Volga riverbed. This dynamic manifests itself in a decrease in the stable flooded area and an increase in the unflooded and unstable flooded areas. An important result is the forecast of the complex territorial structure and criteria for the state of the interfluve until 2050.

The Problem of Effective Evacuation of the Population from Floodplains under Threat of Flooding: Algorithmic and Software Support with Shortage of Resources

“…The VAF region is covered by a grid with the cell size of ∆x = ∆y = 15 m as the base model. The choice of a specific area for water regime modeling requires setting the Digital Hydrological Landscape Model (DHLM [77]), which includes a set of spatial matrixes on the (x i ; y j ) grid. When studying the dynamics of surface waters, one can limit oneself to the matrixes b ij , n Mij .…”

“…The hydrological regime of NPVAF is determined by the discharge of water flow through the dam Q(t) (m 3 /s). The territory of the entire VAF is characterized by a complex branched system of natural canals, the so-called eriks, which ensure the water flow from the Akhtuba and the Volga to the flat part of the interfluve when approximately Q > 17,000 m 3 /s [77]. Moreover, approximately 70-80% of water enters the floodplain through the Akhtuba River and 20-30% directly from the Volga through small canals on the left side.…”

“…Hydrodynamic models of such events describe well the dynamics of water level rise [8,17,37,74]. Separately, we single out a series of works devoted to the study of the hydrological regime of the Volga-Akhtuba Floodplain (VAF) during the spring flood, since the VAF is the testing ground for our study [24,25,[75][76][77][78].…”