Scientific substantiation on land reclamation in the cryolithozone of Yakutia in the context of climate change

The review presents data from studies on climate change in the Arctic and subarctic regions of Russia It is showed, that climate changes unevenly within different regions and seasons. In Yakutia there is a tendency of more frequent events, such as: unexpected spring floods, summer-autumn rain floods, heavy precipitation in winter and other phenomena resulted in hydrodynamic accidents at low-pressure water management structures as well as water supply decrease for reclamation purposes. Takin into account the results of the analysis, it can be assumed that the adaptive technologies application under conditions of climate change in order to increase water availability in the rural areas of both Yakutia and Subarctic zones is a fundamental direction of scientific research in the field of land melioration in the cryolithozone of Yakutia in the context of climate change, which requires research updating to improve methods, new technical, constructive and technological solutions in hydraulic amelioration.

Hydromorphological characteristics of the rivers of Algeria

The article presents the results of a study on the water regime of the rivers of Algeria, which are characterized by a flood feeding regime. The flood regime is mainly formed from heavy rains, the flow of which is 80-90 % of the annual flow. Due to the short duration of rain floods, stationary hydrological posts do not always register them, so they can be characterized as single-modal, which simplifies their design possibilities. For the design of hydrographs of rain floods, a parabolic model-a flood scheme is adopted, and the main characteristics of hydrographs are determined according to this scheme.

Simulation of Rainfall-Induced Floods in Small Catchments (the Polomet’ River, North-West Russia) Using Rain Gauge and Radar Data

In recent years, rain floods caused by abnormal rainfall precipitation have caused several damages in various part of Russia. Precise forecasting of rainfall runoff is essential for both operational practice to optimize the operation of the infrastructure in urbanized territories and for better practices on flood prevention, protection, and mitigation. The network of rain gauges in some Russian regions are very scarce. Thus, an adequate assessment and modeling of precipitation patterns and its spatial distribution is always impossible. In this case, radar data could be efficiently used for modeling of rain floods, which were shown by previous research. This study is aimed to simulate the rain floods in the small catchment in north-west Russia using radar- and ground-based measurements. The investigation area is located the Polomet’ river basin, which is the key object for runoff and water discharge monitoring in Valdai Hills, Russia. Two datasets (rain gauge and weather radar) for precipitation were used in this work. The modeling was performed in open-source Soil and Water Assessment Tool (SWAT) hydrological model with three types of input data: rain gauge, radar, and gauge-adjusted radar data. The simulation efficiency is assessed using the coefficient of determination R2, Nash–Sutcliffe model efficiency coefficient (NSE), by comparing the mean values to standard deviations for the calculated and measured values of water discharge. The SWAT model captures well the different phases of the water regime and demonstrates a good quality of reproduction of the hydrographs of the river runoff of the Polomet’ river. In general, the best model performance was observed for rain gauge data (NSE is up to 0.70 in the Polomet’river-Lychkovo station); however, good results have been also obtained when using adjusted data. The discrepancies between observed and simulated water flows in the model might be explained by the scarce network of meteorological stations in the area of studied basin, which does not allow for a more accurate correction of the radar data.

The change of maximum surface runoff characteristics and following risks for the settlements infrastructure (on the example of the biathlon complex construction in Yuzhno-Sakhalinsk)

The determination of maximum water discharges of floods and rain floods at small mountain streams is relevant for engineering and construction purposes. However, currently, the accounting of the surface runoff of small watercourses is often neglected when construction works are being carrying out. This fact leads to various problems with the exploitation of constructed objects. The purpose of this work is to assess the impact of the construction of the biathlon complex in the recreational area of Yuzhno-Sakhalinsk on the maximum surface runoff from the territory that it occupies. Maps of natural and anthropogenically transformed catchments of the territory were created with the usage of the data, collected during the field work in the summer of 2018. Hydrographical characteristics of both kinds of catchments were determined in accordance with generally accepted recommendations. On the basis of the obtained data, there was carried out the comparative analysis of the current state of the study area and its characteristics before the creation of sports facilities in years 2016–2017. The calculations of the maximum runoff in periods of flood and rain floods according to analytical formulas recommended in the literature were made. The results of the calculations clearly show that water discharges from this area during the period of flood and rain floods increased after the construction of the complex in comparison with discharges observed before construction. Studies have confirmed that the construction of biathlon tracks on the mountainside led to the increase in surface runoff from this area, which is the reason for the overflow of the urban storm sewer of Yuzhno-Sakhalinsk during the period of flood and rain floods, stormwater outlets on the day surface and the activation of erosion processes, suffusion on the considered territory.

The role of precipitation for high-magnitude flood generation in a large mountainous catchment (upper Rhône River, NW European Alps)

High-impact climate events such as floods are highly destructive natural hazards causing widespread impacts on socio-ecosystems. However, processes leading to such events are still poorly understood, which limiting reliable prediction. This study takes advantage of centennial-long discharge series (1923–2010) and meteorological reanalysis (ERA-20C) to study processes generating the high-magnitude flood events (i.e. above the percentile 99.9) of the upper Rhône River (NW European Alps). A particular focus is paid to the role of precipitation on the flood generation to explore in what extent such events could be explained by only atmospheric variables. A flood typology is thus established using a hierarchical clustering analysis and three variables: long (8-day) and short (2-day) precipitation accumulations as well as an index characterizing the amplitude of the discharge increase during the 7 days prior to the flood day. The typology result in four classes, of which two are directly linked to precipitation. One results from heavy precipitation over two days (similar to short-rain floods in the literature) and the other one from a combination of short and long intense precipitation sequences (similar to long-rain floods). The two other types of floods cannot be explained by precipitation only, most probably involving ice and snow melting. The four events of highest magnitude (> 20 year return period) are of various types but are all triggered by heavy precipitation during the days preceding the floods. The role of the precipitation accumulations progressively decreases when considering floods of weaker magnitude, suggesting a higher diversity of processes involved in the generation of e.g. annual flooding. Our results highlight the needs to better understand the atmospheric processes leading to heavy precipitation accumulation since this would allow a better understanding of past and future trends of extreme flood events.