Validity of geophysical parameters in the mudflow cadastre of the south of Russia 

Introduction. When evaluating mudflow danger level and developing hydroengineering anti-mudflow measures, a great meaning is obtained by mudflow basin cadastres that are widely used as reference sources by water-economic project establishments, scientists, specialists of federal and local authorities. The cadastres influence the made decisions on development of the anti-mudflow measures and protective hydroengineering facilities, since the cadastres include basic dedicated data on mudflow basin locations, geophysical (geomorphometric, hydrological) characteristic and expected mudflow parameters. Materials and methods. The article uses known and proven methods of analysis of mudflow basin cadastres. The analytical methods are based on a comparative assessment of the presented results with basic geophysical data of primary sources (cadastres published earlier) and on-site investigations as well as compliance of the suggested empirical formulae on determination of mudflow carrying out volumes and indicators of territorial mudflow striking with mathematical and physical conditions of development of the real mudflow phenomena. Results. Critical analysis of the contents of the Cadastre of Mudflow Danger of the South of the European Part of Russia published in 2015 allows revealing multiple distortions and substitutions of basic geophysical data of mudflow basins. There is an inaccuracy (up to 3,000 to 4,000 % and even higher) of the empirical formulae used in the cadastre for determination of volumes of modflow carrying out. The analysis reveals a hydrogeographical error connected with unfounded substitution of the concept “river length” with the value of the “total length of the main course and all its inflows” that multiply overrates the calculated riverbed length and multiply underrates value of a riverbed bias. Also the study emphasizes unacceptability of definition of the mudflow danger territory by the principle “the water-collecting area of the mudflow course is totally mudflow-threatened" owing to which the absolutely safe natural landscapes are unreasonably declared mudflow-threatened territories. Conclusions. The stated analysis shows a discrepancy of the considered cadastre to the status of scientific and research work. In this connection, the cadastre cannot be recommended for use both in scientific researches and in practical ones. Recommendations on improvement of the mudflow basin cadastres are provided.