ИСТИНА

The Gerkhozhan-Su river valley is one of the most prone in terms of debris flow formation in the North Caucasus Mountains. This work aimed to apply a chain of mathematical models to estimate debris flow characteristics. The simulation was carried out along the river from the upper reaches to the top of the debris flow cone. The choice to apply one model or another was based on the prevalence of the flow state in the particular section. Thus, the transport-shift model was used for debris flow source and sections,where intensification of the flow characteristics took place. The hydrodynamic FLO-2D model was used for transit and accumulation sections. Modeling was conducted for two scenarios: I – high-density flow and II –low-density flow. In the FLO–2D model, 5 cases of rheological parameters were used with different volume concentrations from 25 to 40%. Also, eight variants of loose material parameters in the transport-shift model were considered. According to the modeling results, the initial moisture of the material has the most significant influence on the maximum debris flow discharge. As for the input hydrological data, the results of the field survey, which was held right after the debris flow passage, were used for hydrograph construction. Modeling results included 12 hygrographs for each section. The comparison with field surveys and other modeled results showed the effectiveness of the modeling chain. Also, the causes and consequences of debris flow in 2000 and recent ones are given. The current state of the valley and possibilities of future debris flow formation based on field surveys are presented.