Velocity of debris flow is one of the most important characteristics for the protective construction design. Since debris flows are rare events, and observations are conducted only on stations in Russia, Ukraine, Italy, Switzerland, USA, China, Japan and New Zealand, the velocity is calculated rather than measured. Nowadays, a large number of videos with passing debris flows have appeared on the Internet. Scientists can use such video materials to obtain qualitative and quantitative characteristics of the debris flow. Therefore, the aim of our research is an attempt to measure the debris flow velocity using video materials and compare the obtained results with the calculated values using various methods. The debris flow that came down in Firgen, Austria on August 4, 2012 was chosen as the object of our study. The video was carried out from several angles, so it was possible to select a section of the channel, through which we could measure the debris flows waves velocity. In addition, we calculated the velocities of waves by formulas adopted in the regulatory documents and compared with the measured by video values. During the video analysis, debris flow velocities at different sites were observed: minimum-7.2 m/s and maximum-10 m/s. The calculated values varied from 4.5 m/s to 11.4 m/s. Moreover, we applied model of the transport-shear process of debris flow formation developed by Yu. B. Vinogradov. When we were comparing the obtained debris flow discharges with results from Austrian colleagues, we found out that the values were similar to each other. However, internal scatter in the model changed from 151 to 190 m 3 /s, while in the report of Austrian colleagues the discharges were from 80 to 250 m 3 /s.
Construction of debris flow protection structures is impossible without studying the processes first. Therefore, the purpose of this research was to calculate the magnitude of debris flows in three study areas. Initial information was provided by JSC Sevkavgiprovodkhoz and the Research Center "Geodinamika". The first object of this research was the river Ardon and its tributary the Buddon, because of disastrous consequences for Mizur village of passed debris flows and floods. Modeling of unsteady water movement was carried out for estimation of potential flooding. During modeling, 5 cases of flash floods and debris flows of various probabilities from 0.5% to 1% percent were considered. Therefore, maximum floods for the cross-sections above and in the Mizur village itself were obtained. The second study area was the Chat-Bash stream, which is also situated in the north of Caucasus mountains. For this stream, the maximum discharge that could impact the mining complex at Tyrnyauz was determined. The third study area was the Krasnoselskaia river due to frequent floods in Yuzhno-Sakhalinsk. Applying three cases of various probabilities from 10% to 0.1%, the model determined maximum discharge and water level for the last cross-section above confluence into the Susuya river. Numerical experiments for all study areas with different roughness values were conducted to identify optimal ones. Comparing the model results for all study areas with empirical formulas (Golubcov V.V., Herheulidze I.I., Kkhann, Sribnyj and ASFS of EMERCOM of Russia) revealed that formulas contain only average depth slope angle and empirical coefficients and do not allow estimating flood areas and maximum characteristics of the event with a certain degree of accuracy.
<p>Debris flow is one of the most hazardous events that occur in all mountain regions. &#160;Direct debris flow damage includes loss of human life, destruction of houses and facilities, damage to roads, rail lines and pipelines, vehicle accidents, and many other losses that are difficult to quantify. In July 2015, in the valley of the Barsemdara River (Gorno-Badakhshan Autonomous Region, Tajikistan), plenty of debris flows were observed. As a result, residential areas, social facilities, and infrastructure in Barsem village and neighboring settlements were destroyed and flooded. Besides, debris flow deposits blocked the Gunt River with the subsequent formation of a dammed lake with a maximum volume of 4.0 million m<sup>3</sup>.&#160;<br>The aim of this study was to obtain hydrographs of debris flow waves in the source and detailed zoning of the Barsemdara river valley. For the debris flow source, we applied transport-shift model. Equations of this model were developed by Yu.B. Vinogradov basing on Chemolgan experiments of artificial debris flows descending. Previously, the model characteristics were compared with the observational data of the Chemolgan experiments, and the results were found to be satisfactory [Vinogradova, Vinogradov, 2017]. Based on the equations, a computer program was created in the programming language Python. Besides, we improved the model by adding flow velocity calculations, and eventually it became possible to obtain hydrographs. To investigate quantitative characteristics of the debris flow in the river valley we implied a two-dimensional (2D) model called FLO-2D PRO. It is based on the numerical methods for solving the system of Saint-Venant equations. Besides, in this model, it is assumed that debris flows move like a Bingham fluid (viscoplastic fluid) [O'Brien et al., 1993]. The input information for modeling was digital elevation model (DEM) and previously obtained hydrographs. The output information included flow depth, velocity distribution and hazard level of the territory. The results of the study will be reported.</p><p>1. &#160; &#160;Vinogradova T.A., Vinogradov A.Y. The Experimental Debris Flows in the Chemolgan River Basin // Natural Hazards. &#8211; 2017. &#8211; V. 88. &#8211; P. 189-198.<br>2. &#160; &#160;O'Brien J. S., Julien P.Y., Fullerton W.T. Two-dimensional water flood and mudflow simulation //Journal of hydraulic engineering. &#8211; 1993. &#8211; V. 119, No 2. &#8211; P. 244-261.</p>
Significant area of Yuzhno-Sakhalinsk city within the river Susuya flood plain, a terrace above it and its tributaries are located in flood prone zone. The aim of this research was to estimate maximum characteristics of flash floods and low-density debris flows for the Susuya river and its tributaries, the Rogatka and Vladimirovka rivers. A one-dimensional model of unsteady water movement based on Saint-Venan equations was used. The modeling of river maximum characteristics include following tasks: 1) collect and analyze the data of past dangerous events, 2) process the initial information for the model, 3) simulate discharges of 0.1-10% exceeding probabilities with a change in the hydraulic-morphometric characteristics of the objects. The model does not take into account flow density, therefore numerical experiments were conducted with the increasing coefficient of roughness to identify optimal values of the parameter. The results can be further used in the construction design of residential buildings and infrastructure in Yuzhno-Sakhalinsk.
Models are often used when data is insufficient. However, it is difficult to assess how well they perform, especially for mountainous areas. The Community Land Model 4.5 was selected for testing with the Imingfjell mountain in Norway as a research area. Weather parameters from two nearest meteorological stations and energy fluxes for lichens and shrubs on the Imingfjell were used for comparison with model input and output data, respectively. Calculated by the model temperature from the input was higher by 1-2 °C than from the stations meaning the model underestimates the Imingfjell elevation by 3 times, possibly due to its spatial resolution. As for output data comparison, mean values for modelled soil heat fluxes slightly differed from field data by only 1-3 W/m2. However, these similarities cannot be considered significant due to average correlation coefficients (0.63 for model/lichen and 0.51 – model/shrub).
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