Extreme phases of denudation and questions of geomorphological security of the Upper Angara region

An analysis is made of the manifestations of fluvial and aeolian processes in the southern, developed areas of Irkutsk oblast belonging to the upstream part of the Angara basin. We examine the formation probability and the recurrence frequency of disastrous geomorphological events. The study revealed their association with positive (fluvial processes) and negative (aeolian processes) extremes and anomalies of atmospheric moistening. It is shown that at the time of an extreme event the rate of the processes and the volumes of transported material increase abruptly (by an order of magnitude), and the affected areas show an increase. The criteria for an extreme fluvial event can be represented by a spasmodic buildup of gullies and appearance of new gullies, an abrupt increase in soil losses due to erosion of agricultural lands reaching 100?200 m³/ha, death of crops, releases of mud flows, and destruction of roads, dams, bridges and other structures. The geomorphological consequences of the 1960 summer storm rains are considered to exemplify the disastrous fluvial events. The extremes of aeolian processes have the character of hurricanes encompassing most of the agricultural areas of Irkutsk oblast. The hurricanes are accompanied by a powerful removal of aeolian material from north-west to south-east to the water area of Baikal, to windward slopes and watershed divides of the mountain ranges along the eastern coast. The finest dust particles are transported to neighboring areas of Buryatia, Mongolia and China. The negative consequences of extreme aeolian events include agricultural crop destruction or damage, soil deflation, pollution of surface waters by deflation products, fires, damage to power transmission lines or even death of people. The findings were used in zoning the Upper Angara region according to the degree of geomorphological security of the territory.     

Forecasting the water inflow into the Krasnoyarsk and Sayano-Shushenskoe reservoirs in the second quarter of the year

We consider the various methods of constructing models intended to forecast the average water inflow, in the second quarter of the year, into two reservoirs on the Yenisei river. To solve modeling problems used a new computer technology implemented in the specialized “Stochastic Modeling” software package. Independent data were employed to verify the variants of the models for the formation of variability in quarterly inflow as generated based on different algorithms. A more sophisticated and robust model for forecasting the inflow was constructed as an ensemble of partial models. Based on aggregate results of modeling, we suggest the method of constructing a forecast of the average (for the second quarter) lateral inflow into the Krasnoyarsk reservoir and the inflow into the Sayano-Shushenskoe reservoir by use of observational data accumulated by Srednesibirskoe UGMS (Weather Control and Environmental Monitoring Service), based on an ensemble of partial models. It is established that such an operation reduces the probability of forecasting errors implying an arbitrary selection of models. We constructed forecasts of the aforementioned characteristics using real-time data for 2015. It is stated that the solution of the forecasting problem can be facilitated by using additional information.     

Influence of melioration in natural ecological processes of a small river valley (Poland)

On the basis of the topographic maps from 1933, 1951 and 1962 (sc 1:10 000, 1:25 000 and 1:100 000, respectively) and the satellite image from 2014 (sc 1:10 000), we determined changes in the channel of the small Brynica river (Southern Poland) as well as in the land-use pattern along this river valley after its melioration. Terrain regulation and drainage brought about an intensification of the overland runoff, and a decrease in irrigation of the territory. Due to soil overdrying, some tracts of the valley are experiencing a moisture deficiency. Peat drying can lead to negative consequences, because shallow peats mostly occur on the study territory. Disappearance of peaty soils acts to decrease the degree of suitability of the riverside territories for economic purposes as well as their capacity for recovery. The schematic map of vegetation distribution along the river valley prior to and after melioration as compiled from results of field observations displays differences between mosaic quasi-natural vegetation and areas of typical agrocenoses. The preservation of the natural values along the Brynica valley is possible through balanced economic management, while the differentiation of topography contributes to creating favorable conditions for the formation of biodiversity.     

Sequence hierarchy in a Mesoproterozoic interior sag basin: from basin fill to reservoir scale,the Tombador Formation,Chapada Diamantina Basin,Brazil

The Tombador Formation exhibits depositional sequence boundaries placed at the base of extensive amalgamated fluvial sand sheets or at the base of alluvial fan conglomeratic successions that indicate basinward shifts of facies. The hierarchy system that applies to the Tombador Formation includes sequences of different orders, which are defined as follows: sequences associated with a particular tectonic setting are designated as ‘first order’ and are separated by first‐order sequence boundaries where changes in the tectonic setting are recorded; second‐order sequences represent the major subdivisions of a first‐order sequence and reflect cycles of change in stratal stacking pattern observed at 10² m scales (i.e., 200–300 m); changes in stratal stacking pattern at 10¹ m scales indicate third‐order sequences (i.e., 40–70 m); and changes in stratal stacking pattern at 10⁰ m scales are assigned to the fourth order (i.e., 8–12 m). Changes in palaeogeography due to relative sea level changes are recorded at all hierarchical levels, with a magnitude that increases with the hierarchical rank. Thus, the Tombador Formation corresponds to one‐first‐order sequence, representing a distinct intracratonic sag basin fill in the polycyclic history of the Espinhaço Supergroup in Chapada Diamantina Basin. An angular unconformity separates fluvial‐estuarine to alluvial fan deposits and marks the second‐order boundary. Below the angular unconformity the third‐order sequences record fluvial to estuarine deposition. In contrast, above the angular unconformity these sequences exhibit continental alluvial successions composed conglomerates overlain by fluvial and eolian strata. Fourth‐order sequences are recognized within third‐order transgressive systems tract, and they exhibit distinct facies associations depending on their occurrence at estuarine or fluvial domains. At the estuarine domain, they are composed of tidal channel, tidal bar and overlying shoreface heterolithic strata. At the fluvial domain the sequences are formed of fluvial deposits bounded by fine‐grained or tidal influenced intervals. Fine grained intervals are the most reliable to map in fourth‐order sequences because of their broad laterally extensive sheet‐like external geometry. Therefore, they constitute fourth‐order sequence boundaries that, at the reservoir approach, constitute the most important horizontal heterogeneity and, hence, the preferable boundaries of production zones. The criteria applied to assign sequence hierarchies in the Tombador Formation are based on rock attributes, are easy to apply, and can be used as a baseline for the study of sequence stratigraphy in Precambrian and Phanerozoic basins placed in similar tectonic settings.     

Petrophysical features of the tectonic structures of the Okhotsk continent–ocean transition zone

Petrophysical characteristics are determined for the rock complexes of the Okhotsk margin within the continent–ocean transition zone. Petrophysical maps showing the major inhomogeneities of the main tectonic elements of the studied area are constructed. Petrophysical inhomogeneities and the corresponding geophysical field anomalies are compared. A relationship between the magnetic field anomalies and subsurface rock complexes is revealed. The gravity field anomalies are related to deep inhomogeneities and are almost independent of the subsurface rock complexes of relatively low thickness.     

Evaluation of coseismic landslide hazard on the proposed Haast-Hollyford Highway,South Island,New Zealand

Coseismic landsliding presents a major hazard to infrastructure in mountains during large earthquakes. This is particularly true for road networks, as historically coseismic landsliding has resulted in road losses larger than those due to ground shaking. Assessing the exposure of current and planned highway links to coseismic landsliding for future earthquake scenarios is therefore vital for disaster risk reduction. This study presents a method to evaluate the exposure of critical infrastructure to landsliding from scenario earthquakes from an underlying quantitative landslide hazard assessment. The method is applied to a proposed new highway link in South Island, New Zealand, for a scenario Alpine Fault earthquake and compared to the current network. Exposure (the likelihood of a network being affected by one or more landslides) is evaluated from a regional-scale coseismic landslide hazard model and assessed on a relative basis from 0 to 1. The results show that the proposed Haast-Hollyford Highway (HHH) would be highly exposed to coseismic landsliding with at least 30–40?km likely to be badly affected (the Simonin Pass route being the worse affected of the two routes). In the current South Island State Highway network, the HHH would be the link most exposed to landsliding and would increase the total network exposure by 50–70% despite increasing the total road length by just 3%. The present work is intended to provide an effective method to assess coseismic landslide hazard of infrastructure in mountains with seismic hazard, and potentially identify mitigation options and critical network segments.     

Mechanistic evaluation and reaction pathway of UV photo-assisted Fenton-like degradation of progesterone in water and wastewater

The mechanisms and reaction pathway of UV photo-assisted Fenton-like degradation of progesterone in water and wastewater were investigated. The reaction followed the pseudo-first-order kinetics for both the dark Fenton-like and UV photo-Fenton-like processes. The reaction kinetics of the UV photo-assisted process improved with the presence of humic acid (HA) in wastewater, due to the formation of Fe(III)-HA complexes which enhanced Fe(II) production by a ligand-to-metal charge transfer. The UV photo-assisted process reduced the amount of ferric required to completely degrade progesterone by 60 % and lowered the activation energy to 42 kJ/mol compared to 104 kJ/mol for the dark Fenton-like process. Complete degradation of progesterone was achieved through a multi-step process involving several intermediate compounds.