Could road constructions be more hazardous than an earthquake in terms of mass movement?

Roads can have a significant impact on the frequency of mass wasting events in mountainous areas. However, characterizing the extent and pervasiveness of mass movements over time has rarely been documented due to limitations in available data sources to consistently map such events. We monitored the evolution of a road network and assessed its effect on mass movements for a 11-year window in Arhavi, Turkey. The main road construction projects run in the area are associated with a hydroelectric power plant as well as other road extension works and are clearly associated with the vast majority (90.1%) of mass movements in the area. We also notice that the overall number and size of the mass movements are much larger than in the naturally occurring comparison area. This means that the sediment load originating from the anthropogenically induced mass movements is larger than its counterpart associated with naturally occurring landslides. Notably, this extra sediment load could cause river channel aggregation, reduce accommodation space and as a consequence, it could lead to an increase in the probability and severity of flooding along the river channel. This marks a strong and negative effect of human activities on the natural course of earth surface processes. We also compare frequency-area distributions of human-induced mass movements mapped in this study and co-seismic landslide inventories from the literature. By doing so, we aim to better understand the consequences of human effects on mass movements in a comparative manner. Our findings show that the damage generated by the road construction in terms of sediment loads to river channels is compatible with the possible effect of a theoretical earthquake with a magnitude greater than Mw = 6.0.

Technogenesis and Ecological State of Natural Waters in Eastern Transbaikalia

The research on the state of water ecosystems is significant in terms of future biological impacts of natural and anthropogenic effects. The key branches of natural resources management in Eastern Transbaikalia (agriculture, hydraulic power industry) are based on using water resources. The findings show that technogenesis affects surface waters of the region. Alluvial gold mining represents a significant part of mining industry. Gold mining in river channels results in run-of-stream diversion and interferes with the ecosystem of watercourses. A newly formed structure of a water ecosystem is not favourable for self-purification capacity of rivers. This leads to pollutants accumulation in water objects and deteriorates ecological state of watercourses. Natural components in the technoecosystem of hydropower objects in Eastern Transbaikalia are Lake Kenon and the Kharanor Reservoir. Although the catchment area is polluted by TPP-1, the ecosystem of the lake is still capable of self-purification due to biodiversity of hydrobionts. Under the dry climate in recent years, the Kharanor Reservoir ecosystem turned as rather unstable due to constant refilling from the Onon River. However, generally, pigment indices show physiological activity of primary producers of organic matter.

Antropogeniczne przekształcenie rzek na Ponidziu Pińczowskim

One of the three basic components of assessing ecological state is the determination of hydromorphological conditions occurring in river channels and valleys. In this paper an effort has been taken to check usefulness for such evaluations River Habitat Survey (RHS) – British research method, which is used in Poland for classification of ecological quality of surface waters from the view-point of their actual hydromorphological state. The possibilities of using this method in field teaching of geography students were checked. For this purpose, the RHS method was modified and adapted to the needs of field exercises. Research was conducted in Nida Riverside region, near Pińczów (świętokrzyskie voivodeship, Poland). Collected material makes it possible to calculate synthetic indicator HMS (Habitat Modification Score) which allow the hydromorphological state of a river to be presented in numerical form and assessing river modification by human activities. The research released advantages of the RHS in field teaching of students. The method can also be used in field exercises with secondary school students.

Assessing discharge periodicity in mountain catchments using classified environmental conditions (Tatra Mountains, Poland)

The periodicity of a river expressed in cycles of various lengths (monthly, seasonal, multiannual) is a result of climatic factors and overlapping environmental conditions within its catchment. In uncontrolled or poorly surveyed catchments, it is very difficult to determine the duration of a stream’s hydrological activity. This is especially relevant for catchments with complicated water circulation in karstic rocks. The present study concerns the small catchment of the Strązyski Potok river located in the area of the Tatra National Park, in the Western Tatras. The observation period covered the 2015 hydrological year, which differed hydrologically from average conditions. This study aims to develop a simple method to explain the processes shaping the mountain stream discharge periodicity. The research employed periodic field observations linked with climatic and non-climatic factors. Environmental conditions were assessed as four classes reflecting their influence on appearance or disappearance of mountain stream water. Class boundaries were the values of quartiles. The degree of correspondence between environmental factors and stream field observations was described via the Index DC (Degree Correspondence Index) approach. Complete correspondence (Index DC =0) was found in 23% catchments, a weak relationship between conditions favouring discharge and actual condition (Index DC= -1, +1) was noted within 11 catchments, while in 9 catchments, no such relationship was found (Index DC = -2, +2). The obtained results indicate a correspondence or lack thereof between the environmental potential of the catchment and its discharge periodicity. The discrepancies between the assessment of the influence of climatic and non-climatic factors and the data collected during field observations provide a basis for more detailed studies. Continuation of these studies based on the proposed classifications will allow for a more complete explanation of water disappearance in river channels and the determination of their short- and long-term discharge periodicity.

Assessment and Attribution of Mangrove Forest Changes in the Indian Sundarbans from 2000 to 2020

The Indian Sundarbans, together with Bangladesh, comprise the largest mangrove forest in the world. Reclamation of the mangroves in this region ceased in the 1930s. However, they are still subject to adverse environmental influences, such as sediment starvation due to migration of the main river channels in the Ganges–Brahmaputra delta over the last few centuries, cyclone landfall, wave action from the Bay of Bengal—changing hydrology due to upstream water diversion—and the pervasive effects of relative sea-level rise. This study builds on earlier work to assess changes from 2000 to 2020 in mangrove extent, genus composition, and mangrove ‘health’ indicators, using various vegetation indices derived from Landsat and MODIS satellite imagery by performing maximum likelihood supervised classification. We show that about 110 km2 of mangroves disappeared within the reserve forest due to erosion, and 81 km2 were gained within the inhabited part of Sundarbans Biosphere Reserve (SBR) through plantation and regeneration. The gains are all outside the contiguous mangroves. However, they partially compensate for the losses of the contiguous mangroves in terms of carbon. Genus composition, analyzed by amalgamating data from published literature and ground-truthing surveys, shows change towards more salt-tolerant genus accompanied by a reduction in the prevalence of freshwater-loving Heiritiera, Nypa, and Sonneratia assemblages. Health indicators, such as the enhanced vegetation index (EVI) and normalized differential vegetation index (NDVI), show a monotonic trend of deterioration over the last two decades, which is more pronounced in the sea-facing parts of the mangrove forests. An increase in salinity, a temperature rise, and rainfall reduction in the pre-monsoon and the post-monsoon periods appear to have led to such degradation. Collectively, these results show a decline in mangrove area and health, which poses an existential threat to the Indian Sundarbans in the long term, especially under scenarios of climate change and sea-level rise. Given its unique values, the policy process should acknowledge and address these threats.

Modern Analogues of Sedimentation of Lower Permian Reservoirs in the Dnieper-Donets Depression

The paper considers the problematics of identifying proper analogues for understanding carbonate and clastic reservoir distribution and prediction in the Lower Permian and Upper and Lower Carboniferous within the Dnieper-Donets basin. The focus of the exploration team was finding meandering rivers. This choice was proven good in mapping reservoirs and finding traps deeper in the Upper and Middle Carboniferous, although for Permian clastic section the approach was not helpful. The second option was desert dunes, but poor sorting of reservoirs suggests a more complex picture. Analogues such as desert environment is quite logical for describing Lower Permian as aridic climate, with red and brown shales and sands. Lower Permian reservoirs have a moon-like shape in the vertical sections that could be easily mistaken for river channels, but in such a dry climate, it is very likely water flow channels with sporadic hurricane-related activities. Core and logs shows chaotic grain sizes, but more with fine grains with almost no coarse grains. The source of sedimentary material could be mountains of Ukrainian Rock Shield from the South and Voronezh massif from the North. This conceptual model is proposing not to look for meandering channels, but more for braided channels with poorly sorted material. The current time analogue could be the Oman desert between the mountains and peninsula. From satellite images, braided channels are clearly visible in the direction towards the Indian Ocean. The channels’ internal structure is quite heterogeneous. This method suggests exploration targets with possible widths of the channels as big as hundreds of meters and their lengths under 10 and between 10-20 kilometres maximum.

Channel Migration of the Meandering River Fan: A Case Study of the Okavango Delta

Okavango delta is a typical distributive fluvial system, which is composed of a series of sand island-river-swamp networks. River migration in the Okavango delta is analyzed by using satellite images from Google Earth and Alaska Satellite Facility (ASF). Four configuration characterization parameters are selected to depict and measure the meandering river. These four parameters are sinuosity index (S), curvature (C), the difference of along-current deflection angle (Δθ) and expansion coefficient (Km). In the fan, the channel migration is mainly asymmetric. According to geomorphic elements and associated features, Okavango Delta can be subdivided into three zones: axial zone, median zone and distal zone. Under the influence of slope, climate and vegetation, different migration modes are developed in different zones. As the river moves downstream, the sinuosity index of the river on the Okavango Delta decreases downstream. Based on the characteristics of different zones, the sedimentary facies model of a single source distributive fluvial system of a meandering river is proposed. The models of channel migration and sedimentary facies have wide application. This research will not only provide a basis for the prediction of future river channels but will also provide important theoretical guidance for the study of the sedimentary morphology of underground reservoirs.

Study on Flow Velocity Distribution in Open Channel With Flexible Vegetation

Ecological management of river channels is a hot topic for current sustainable development and flow measurement of ecological river is an important part. In this article, a flow velocity distribution model of the channel containing flexible vegetation is constructed from the vegetation riverbed theory and the bursting phenomenon to reveal the microscopic mechanism of the flow velocity distribution in the upper layer of vegetation. In the vegetation riverbed law, the effect of flexible vegetation is evaluated by the mixed length formula. The bursting phenomenon law considers the influence of the channel sidewalls on the flow and a two-dimensional velocity model is established by introducing the concept of average turbulence structure. The mechanism of the downward shift of the maximum flow velocity point on the channel sidewall is explained. The verification of the calculated velocity profiles is carried out based on data obtained in laboratory experiments. The results show that the combination of the two models can well describe the velocity distribution of the whole channel. At the end, the phenomenon of flow velocity zoning in open channel is discussed, which provides a solution for flow measurement in ecological channel.