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.

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).

<p>Mountains are some of the most inaccessible regions, where not many weather stations located due to the high altitudes. Thus, the amount of available mountain meteorological data is limited. One of the modern solutions to data insufficiency is modelling. However, it remains challenging to assess how well a model simulates local climate conditions.</p><p>The main goal of this study was to check the model accuracy by comparing its results to observed data, with a focus on the radiation budget.</p><p>The Community Land Model 4.5 (CLM4.5) provided by the University of Oslo was used. It is a one-dimensional model and the default land component in the Community Earth System Model 1.2. CLM4.5 simulates various biogeophysical and biogeochemical processes based on surface energy, water, and carbon balances [Oleson et al. 2013]. Here, the model was run from 1901 to 2014 in the offline mode, meaning it was getting input from a pre-existing dataset. Modelled fluxes from the radiation budget, such as incoming (K<sub>in</sub>) and outgoing shortwave (K<sub>out</sub>) radiation, incoming (L<sub>in</sub>) and outgoing (L<sub>out</sub>) longwave radiation, net all-wave (Q*), net shortwave (K*) and net longwave (L*) radiation, were used for compassion with observations.</p><p>A 2.5×0.2 km site on Mount Imingfjell (1191 m) in southern Norway was selected as the study object. Different microclimatic parameters, including radiation fluxes, were measured separately over lichens and shrubs for 44 days in the 2018-2019 summers [Aartsma et al. 2020]. These vegetation types were chosen to understand the differences between them and see the potential impact of “shrubification” on surface albedo. Since there was no time overlap between modelled and observed data, we had to make datasets more comparable. 44 days from field data were used to create composite datasets that represent three temperature regimes based on data from the nearest weather station: “cold”, “normal” and “warm”. Each observation was assigned to one of these temperature regimes. In CLM4.5, recently available years were analysed to find ones with average summer temperatures closest to the stated temperature regimes. Statistical analysis, such as a two-sample t-test, was performed to see if there were any significant differences between the datasets.</p><p>T-tests showed that modelled K<sub>in</sub>, L<sub>in</sub> and K* were always similar to measurements, except for L<sub>in</sub> and K* in “cold” conditions. CLM4.5 K<sub>out</sub> differed from observed ones in almost all regimes. Simulated L*, Q* and L<sub>out</sub> varied between temperature conditions and vegetation types. Still, about 70% of the modelled fluxes closely resembled the shrub ones, while only around 50% resembled lichens. Modelled albedo was also closer to shrub albedo.</p><p>In conclusion, CLM4.5 most likely modelled credible values for radiation fluxes, but further research is needed for greater clarity.</p><p><strong>References</strong></p><p>1. Aartsma, P., Asplund, J., Odland, A., Reinhardt, S., & Renssen, H. (2020). Surface albedo of alpine lichen heaths and shrub vegetation. Arctic, Antarctic, and Alpine Research, 52(1), 312-322.</p><p>2. Oleson, K., Lawrence, D., Bonan, G., Drewniak, B., Huang, M., Koven, C., . . . Yang, Z.-L. (2013). Technical description of version 4.5 of the Community Land Model (CLM).</p>