Rocky Banks Research Articles

Research on the geological process of river action on the toppling deformation of rocky bank slopes in V-shaped gorge reservoirs

The toppling deformation in bank slope of V-shaped Gorge reservoirs in Southwest China is very common. After the impoundment of the reservoir, geological disasters such as collapse and landslide may occur in toppling bank slope, which poses a threat to the normal operation of hydropower projects and personnel safety. Therefore, it is of great engineering significance to study its genetic mechanism and development law. The trenching of river valley is one of the main factors of bank slope toppling deformation. In the process of river action, the free face is formed on the slope, and the rock mass is unloaded to the free face, resulting in toppling. Taking the bank slope of a reservoir in the V-shaped Gorge area on the edge of the Qinghai Tibet Plateau in Southwest China as an example, this paper studies the relationship between river action and the development of toppling. According to the seven terraces formed on both banks of the river, the trenching of the river valley is divided into seven stages. The toppling development characteristics of each stage are analyzed by discrete element method. According to the development characteristics of toppling deformation category, the toppling deformation is divided into five stages, they are initial toppling deformation stage, toppling development stage, intensified toppling deformation stage, temporary stability stage and failure stage. The research results can help to determine the development type and stage of bank slope toppling deformation in V-shaped Gorge area, so as to predict its further development deformation characteristics.

Naturalisation of the tree of love Aichryson laxum (Crassulaceae) and its implications for biosecurity surveillance in New Zealand

ABSTRACT Aichryson laxum is documented as newly naturalised in Aotearoa New Zealand. Although tree of love is its colloquial name, it is a small, succulent herb in the Crassulaceae, and is indigenous to the Canary Islands. It has been cultivated in New Zealand for at least several decades. The species has recently been collected wild at multiple sites around Wellington, with collections also from Napier and near Ōtaki Forks, and an additional report of wild plants from Christchurch. Despite its small size, A. laxum can grow densely, adding to the weeds smothering surfaces and displacing indigenous species from habitats such as open, rocky banks. Within Wellington, A. laxum was first noticed to be growing wild in 2019, but it has now been found to be established at multiple sites throughout the city. Either it is spreading aggressively via its tiny, wind-dispersed seeds, or it has lain undetected for some time, even though it is a distinctive species among Wellington’s flora. Both scenarios are concerning, and A. laxum provides another example of the shortcomings of the nation’s current surveillance – recently described by the Parliamentary Commissioner for the Environment as largely passive and serendipitous – for emerging weeds newly naturalising from the tens of thousands of exotic plant species cultivated in New Zealand.

Geomorphic changes in river styles in a typical catchment of the Brazilian semiarid region

Rivers in drylands behave differently from those in wetlands due to their irregular flow patterns. This study investigated morphological changes in the Brazilian semiarid region to infer the evolutionary trend of the river. Consequently, the focus was on analyzing the fluvial dynamics and the propensity for change in rivers within the Piranhas River basin. River styles were defined based on the typologies of valley configuration, planimetric shape, sets of geomorphic units, and bed material attributes of the rivers under analysis. In total, eight river styles were identified, broadly classified into confined (two styles), partially confined (three styles), and laterally unconfined (three styles). Confined styles are typically associated with areas near the headwaters, characterized by rocky banks and beds with high flow energy. These channels were found to have low sensitivity to changes in geomorphic conditions. In contrast, unconfined styles predominantly displayed high sensitivity in their stretches, primarily due to the presence of a rocky bed. In the case of partially-confined styles, channels with moderate sensitivity were primarily observed. These channels exhibit a strong tendency to adapt based on their geoindicators and geomorphic conditions, rather than external influences. Interestingly, the resistance to change in geomorphic conditions was linked to unexpected river characteristics within the catchment. Lastly, a historical analysis of the flow allowed an understanding of the dynamics of the styles that displayed a higher propensity to change. This unveiled possible high-magnitude events that may have caused morphological alterations in these styles.

Spatial-temporal assessment of Norovirus contamination in mussels from Cherrat estuary, Morocco, by real-time Reverse Transcription-Polymerase Chain Reaction

Mussels filter large amounts of water to extract nutrients; therefore, they can concentrate and accumulate in their tissues infectious agents, and vectors of enteric diseases. The aim of this study was to assess mussel contamination by Norovirus genogroups I and II in the Cherrat estuary to determine the public health risk linked to their consumption. Mussels (Mytilus galloprovincialis) were collected (n=52 samples; 12 mussels/sample) at four sites (S1 and S2 located on the right rocky bank / S3 and S4, located on the rocky left bank) in the Cherrat estuary (Casa-Settat region), Morocco, during 13 months, from March 2019 to March 2020. Norovirus was detected and quantified by real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR). Norovirus genogroups I and II were detected in 17.30% and 94.23% of mussel samples, respectively. Contamination by Norovirus (genogroups I and II) was not correlated with seasonal factors (month and rainfall), and Norovirus prevalence was comparable among the four sampling sites. Consumption of raw or undercooked mussels contaminated with Norovirus can cause gastroenteritis, which represents a potential risk to human health. The present study would be helpful to control and manage the potential risk to the public health of the Moroccan population due to the degradation of water quality continuously impacted by runoff, the urban wastewater treatment system malfunctions, and overflows from nearby sewage systems.

Degradation of Typical Reverse Sand-Mudstone Interbedded Bank Slope Based on Multi-Source Field Experiments.

The bank slopes in the Three Gorges Reservoir area (TGRA) have experienced obvious deterioration under the action of the periodic fluctuations in the reservoir water level. Generally, laboratory tests have been used to reveal the evolution trend of the slope banks. However, this method has a certain degree of cross-scale problem, especially for the mechanical state in a complex environment. Therefore, in this study, we took the Yangjiaping bank slope in the TGRA as an example and proposed a comprehensive on-site detection method to further reveal the rock mass degradation phenomenon of this typical reverse sand-mudstone interbedded bank slope. Specifically, multi-scale laser scanning, cross-hole acoustic wave detection, and inclination measurements were performed to analyze the fractures, quality, and deformation of rocky banks. The results showed that the deterioration of the bank slope manifested as the expansion, deepening, and widening of the cracks, as well as the peeling off and loosening of rocky banks. Large-scale laser scanning revealed that the deterioration zone was deformed along large fracture zones and layers. Unlike limestone slopes, the intact sandstone underground might be degraded by changes in water. There are few inclinometers and no deformation or weak deformation, which requires long-term monitoring. The relevant research methods provide an important reference for determining the instability and failure trend of the reservoir bank slopes.

Dream Routes Intersecting; Shape of Water Shaping Rocky Banks

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Dream Routes Intersecting; Shape of Water Shaping Rocky Banks

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Seafloor habitats across geological boundaries in Disko Bay, central West Greenland

In this paper we describe seafloor terrain of nearly the entire Disko Bay region and provide scientific baseline information about surface geology and sedimentary environments that can support the seafloor management plan in Greenland. Our study utilized multiple datasets of multibeam bathymetry and backscatter, seismic profiles and ground-truthing consisting of video footage from drop camera and benthic video sled, as well as sediment samples from grab and corers. Our results revealed that the key geological units in Disko Bay characterize the scale of geomorphic features, which in turn affects the distribution and complexity of habitat zones. The NE sub-region is underlain by Cretaceous sandstone and characterized by large-scale landforms, mainly vast flat areas draped by glacial lineations, bedrock ridges and pockmark fields. This setting promotes less topographically complex habitats, i.e. coarse plain, muddy/sandy plain with dropstones, and muddy plain. The SW sub-region is characterized by Precambrian Gneiss and Paleoproterozoic metasedimentary rocks with complex system of small-scale geomorphic features, such as cross-cutting channels. This results in topographically complex habitats in the area, such as rocky bank, coarse rugged terrain, and rocky slopes. Two distinctive habitat areas, associated with potential gas seeps, i) southern pockmark field and ii) western zoanthid-sponge wall, were discovered at the geological boundary separating the two sub-regions. Our study highlights the importance of seafloor habitat mapping and analyses by providing fundamental geophysical knowledge necessary to comply with long-term sustainable use of marine resources in Greenland.

Fluvial archives as records of the late quaternary landscape evolution in the southeastern Brazilian highlands

This paper discusses the role of fluvial archives as records of the landscape evolution and geomorphological configuration of the southeastern Brazilian highlands (Brazilian Atlantic Plateau), particularly in the Espinhaço meridional ridge. A cartographic bases search was carried out, complemented by fieldwork to support the definition of the studied 10 valleys. During fieldwork, depositional levels and sequences were described in terms of composition, thickness, organization, and transitions, vertical sections were selected and described. Different fluvial levels in each valley were identified mainly by the heights and characteristics of the sediments of which they were composed. Sediments were sampled at 24 representative points and dated using the Single-Aliquot Regenerative Optically Stimulated Luminescence technique (SAR OSL, five aliquots). The depositional archives allow the reconstruction of six regional relief evolution phases associated with fluvial processes throughout the Late Quaternary (from 26 ka to present). On the upper quartzite surfaces, the bottom valleys are wider, and the channels are straighter, with beds and/or rocky banks than the down surfaces. In this context, the current river dynamics have been controlled by local baseline levels that have reduced the intensity of downcutting. In the lower crystalline areas, valleys tend to be narrower and deeply dissected, favoring the mischaracterization of older archives. Stepped depositional levels in these compartments indicate the role of the Brazilian Shield tectonics (epirogenetic uplifts) in regional geomorphological evolution. Furthermore, the set of deposits and river system characteristics, which show filled valley bottoms, reflect the current stabilization of the regional base level and indicate the importance of lithostructural, climate, and anthropic aspects for understanding the role of fluvial processes in landscape configuration.

Evolution analysis of the Banbiyan dangerous rock mass in the three gorges reservoir area, China

ABSTRACT Due to the changing mechanical environment, it is difficult to determine the evolution process of the rocky bank. In this paper, the Banbiyan dangerous rock mass (BDRM) in the Three Gorges Reservoir area was taken as an example to analyze its failure characteristics. As for this specific evolutionary environment, a new judgment system was proposed, involving the comprehensive field survey method and indoor tests. The key information about the steep areas, interior areas, and underwater areas was obtained, which overcomes the limitations of the conventional survey methods. On this basis, combined with a simplified geo-mechanical model and dry-wet cycle tests, the evolution trend of BDRM under variable water levels was predicted. The results show that the stability of BDRM depends on many factors, including the self-weight of overlying rock mass (the location of the broken area), the strength of the broken area, the water pressure of the trailing edge crack (rainfall) and the reservoir water level. According to the calculation results, the BDRM is likely to slip along the broken area after 46 dry-wet cycles. The application of related methods can provide an important reference for judging the evolution trend of unstable rocky banks worldwide.

Cross-Scale Study of the High-Steep Reservoir Banks under Different Mechanical States

AbstractThe deformation of high-steep rocky banks is caused by the self-weight of overlying rock mass and the fluctuation of reservoir water. In this paper, the newly developed testing equipment and the particle flow code (PFC) were used to complete the cross-scale study of the high-steep rocky banks under different mechanical states. The test conditions involved the dry state, saturated state, and hydraulic coupling states under different confining pressures. Combined with the micrographs of the fractured surface under different mechanical states, it can be found that the participation of the water could reduce the bond contact and accelerate the deformation of the particles, ultimately leading to an increase in the plastic deformation and a decrease in the peak strength of the rock mass. Compared to the saturated state, the water in the hydraulic coupling state was not transferred though the storage space was compressed; thus, the water pressure would further promote the extension of the microcracks. When considering the fluctuations of the reservoir water, the changes in the mechanical state may accelerate the degradation rate of the rock mass. The related methods can provide data support and a theoretical basis to the evolution trend of high-steep rocky reservoir banks.

Gharials (Gavialis gangeticus) in Bardiya National Park, Nepal: Population, habitat and threats

Abstract The Critically Endangered gharial (Gavialis gangeticus) residing within Bardiya National Park (BNP) in Nepal constitutes the sixth major sub‐population of this unique lineage; however, this population is not well studied. A 46 km protected stretch of the Babai River and a 60 km stretch of the Karnali River in and around BNP were surveyed for gharials in early 2017 and in 2019. Gharial counts in 2017 – 17 from the Babai and one from the Karnali rivers – consisted of 10 adults, five sub‐adults and three juveniles. In 2019, 19 gharials were counted – 18 for the Babai and one for the Karnali – comprising 11 adults, six sub‐adults and two juveniles. In the Babai River within BNP, four breeding groups were identified. Gharials in BNP prefer sandy vs. rocky banks for basking and completely avoid sand‐grass and clay banks. Habitat preference did not vary with size class. Protected stretches of both rivers inside BNP (76 km) have resident gharial, intact habitats and few human threats. In contrast, the unprotected stretch of the Karnali (30 km) is threatened by boulder quarrying, sand mining and unlicensed fishing, and is avoided by gharials despite the availability of habitat. This study established baseline data, including indices of population size, distribution and habitat preferences, and documented resident gharials that are breeding in the Babai River in BNP. The conservation of this Babai population is crucial for the species’ survival in BNP. Based on this study, we recommend the following conservation actions on the Babai stretch: (a) determine hatching success; (b) assess juvenile recruitment; (c) consider supplementation by releasing captives; (d) study riverine features important as baselines; (e) accommodate upstream movements on the protected Babai stretch; and (f) protect the downstream Babai outside the boundary of the BNP.

Toward nearshore, bathymetry induced wave amplification in False Bay, South Africa

A seamount called Rocky Bank (RB) has been suspected to spatially focus wave energy toward the eastern periphery of False Bay, South Africa, where it is not uncommon for fishermen to get washed off by waves. Situated at the bay’s mouth, the submerged seamount acts like a refracting lens for incoming long-crested swell. The present study aims at understanding the wave transformation effects of RB and the nearshore bathymetry using the phase-averaging spectral wave model simulating waves in the nearshore. Open ocean conditions around the Cape Peninsula, derived from National Center for Environmental Prediction reanalysis products, were used as model boundary conditions. To establish RB’s influence, a bathymetry without RB was created. The model output indicated that coastal significant wave heights were 9% greater when RB was removed. This difference was largest for smaller incident significant wave height and increasing incident peak period. RB also causes wave convergence via refraction and presents evidence for spatial focusing, a coincidental interference, extreme wave generating mechanism. This result, together with recorded incidents and anecdotal evidence, suggests that the wave transformation effects of RB may be leading to extreme waves along the eastern periphery. Evidence for spatial focusing toward the eastern periphery occurred for peak wave directions between 210° and 245° true north and for peak periods greater than 13 s. The likelihood of a wave leading to an incident is greater in smaller, long-crested seas based on the recent literature for the region. To extend this study to predict rogue wave events within False Bay, a phase-resolving model would be required.

Demographic structure of clonal, endemic, and endangered rheophyte bromeliad Dyckia ibiramensis: asexual vs sexual reproduction

Abstract In southern Brazil some species of Dyckia genus occur as rheophytes. Dyckia ibiramensis is an endemic bromeliad that occurs in discrete patches of the rocky banks along Itajaí do Norte River, Santa Catarina state. Four populations along Itajaí do Norte River were studied. In each population, all rosettes were counted and the diameter of each rosette was measured. The spatial distribution of the rosettes was identified as an isolated rosette or a clump. The clumps were classified according to the number of rosettes. The total number of rosettes per population ranged from 295 to 1,412. Most rosettes occur in clumps (98.1%), and 41% have reproductive rosettes. The number of rosettes per clump ranged from two to 43 rosettes. The percentage of reproductive rosettes per population ranged from 7.8 to 26.7%. The correlation between the number of clumps or between the total number of rosettes and the area of occupation was significant and positive. Few seedlings and isolated rosettes, production of offshoots occurred on both immature, and reproductive rosettes, and clumps with few rosettes can indicate the clonal propagation predominate in D. ibiramensis. Therefore, the maintenance and monitoring of the populations are essential for its long-term in situ conservation.

What is in our seas? Assessing anthropogenic litter on the seafloor of the central Mediterranean Sea

Abundance, composition, and distribution of macro-litter found on the seafloor of the Strait of Sicily between 10 and 800 m depth has been studied using data collected by bottom trawl surveys MEDITS from 2015 to 2019. Three waste categories based on the items use were considered: single-use, fishing-related and generic-use. Over 600 sampling sites, just 14% of these were litter-free. The five-years average density of seafloor litter was 79.6 items/km2 and ranged between 46.8 in 2019 and 118.1 items/km2 in 2015. The predominant waste type was plastic (58% of all items). Regardless of material type, single-use items were a dominant (60% of items) and widespread (79% of hauls) fraction of litter with a mean density of 48.4 items/km2. Fishing-related items accounted for 12% of total litter items. Percentage of dirty hauls and litter density increased with depth. Analysis of the relation density-depth indicates a progressive increase of litter density beyond depth values situated within the interval 234–477 m depending on the litter category. A significant decrease in litter density by categories was observed over the period. Patterns of spatial distribution at the higher depths (200–80 0m) resulted stable over the years. Density hotspots of fishing-related items were found where the fishing activity that uses fish aggregating devices (FADs) is practised and in the proximity of rocky banks. Single-use and generic-use objects densities were greater on the seafloor along main maritime routes than other areas. Comparisons between the percentage of hauls littered with anthropic waste from the mid-1990s against those in 2018–19 highlighted an increase of about 10.8% and 15.3% for single-use items and fishing-related items respectively, and a decrease of 18.6% for generic-use items. This study provides a snapshot of the current situation of littering in the central Mediterranean Sea and represents a solid baseline against which the effectiveness of current and future mitigation strategies of the litter impact on marine environment can be measured.

The abundance and habitat use of demersal fishes on a rocky offshore bank using the ROPOS remotely operated vehicle

Offshore rocky banks are ecologically important refuge habitats for a number of U.S. commercial groundfish species. However, they are challenging to survey, and data on the abundance and ecology of fish populations at deep banks are limited. We used the remotely operated vehicle ROPOS to carry out visual surveys at two sites on Cherry Bank in the Southern California Bight, eastern Pacific Ocean. We observed differences in fish assemblages related to depth and habitat type and found that rockfishes (Sebastes spp) made up 65% of fishes recorded. Rockfishes and combfish (Zaniolepis spp) were associated with relatively shallow areas with hard substrate whereas flatfishes (Pleuronectiformes) and poachers (Agonidae) were found on unconsolidated sediments. Thornyheads (Sebastolobus spp) and hagfishes (Myxinidae) mainly occurred in areas of patchy habitat. Habitat and depth explained 52% of the variation in fish assemblages between transects with habitat explaining a greater proportion of the variation than depth. We observed large differences in the number of juvenile rockfishes and Sebastomus rockfishes between study sites with hard substrates and also had higher abundances of juvenile rockfishes versus sites characterized by mixed substrates. With the exception of unidentified Sebastomus, the current design had relatively low power to reliably detect observed differences for most taxa, so we report the number of additional transects that would be required to detect a 50% increase in densities. These data provide a baseline on groundfish densities and habitat associations at Cherry Bank and key information for the design of future work including Bayesian approaches to estimating coast-wide abundance.

First direct evidence of reproductive behaviour of the white grouper, Epinephelus aeneus (Geoffroy Saint-Hilaire, 1817)

This study describes the first ever reported direct observation of a pair spawning event and the reproductive liveries of the white grouper, Epinephelus aeneus. Spawning took place on a rocky bank located in the Marine Protected Area (MPA) of Tavolara-Punta Coda Cavallo (NE Sardinia, Italy), in the Western Mediterranean Sea. In the evening of August 4th, 2018, the spawning of two large-sized individuals (~90 cm total length), displaying distinct colour patterns, was observed using SCUBA diving. This direct observation is the first record of E. aeneus male reproductive livery, characterized by a darker coloration on the head, the dorsal part of the body and the caudal fin. In addition, information on the environmental conditions in which reproduction occurred was collected. At the study site, relatively high seawater temperatures were recorded at the time of the E. aeneus spawning (24 °C at 24.7 m), as well as over the 2018 summer months (July-September), even in deep waters (>35 m), compared to previous summers. The spawning event occurred in a coralligenous-dominated seascape where fishing is prohibited, while diving activities are allowed. The site hosts abundant populations of ecologically and commercially valuable fish species (e.g., groupers, sparid fishes), with significant proportions of large-sized individuals (i.e. reproducers). Further studies are needed to advance our knowledge of the white grouper, with a particular emphasis on reproduction and the importance of implementing effective protection measures. Prioritizing management actions at key reproductive sites, such as rocky banks, is essential for ensuring the protection and/or recovery of over-exploited species.

Rational arrangement of direct plummets in concrete dams

Introduction. The design and construction of high hydroelectric installations are closely related to in-situ observations and studies over their condition and operation, which are the most reliable and effective means of verifying the reliability of calculation methods and design solutions. According to the results of the in-situ observations and studies during the construction and operation of dams, to monitor their condition by means of measurement systems, laboratory tests and calculation methods, unified methods can be developed for equipping the installations with devices on a unified principle. Currently, there is quite a lot of experience in the development and application of methods of in-situ research. New-type devices for measuring displacements, stresses in concrete, filtration flows and piezometric levels are developed. Automated systems for monitoring the behavior of hydraulic structures during the construction, filling of the reservoir and operation are installed. Modern satellite systems GLONASS and GPS are used. Materials and methods. The research was carried out on the arch dam of Inguri HEPS by means of 2177 measuring systems, 46 of which are direct and opposite plummets. The body of the dam has three direct plummets and one in each of the rocky bank abutments. Displacements relative to the plummets were measured with an optical coordinate-measuring apparatus. Statistical analysis methods were used to process the measurement data. Results. A technique of rational direct plummet arrangement in concrete dams was fine-tuned using statistical analysis methods and Barlow-Hunter-Proshan mathematical model based on the modern experience of in-situ observations and research. The type of distribution law of dam horizontal displacements was determined by means of analyzing the histograms of the measured indicators of the static state of the installation. The required number of plummets for the key console of the Inguri arch dam was specified. This technique was used in practice for designing high concrete dams. Conclusions. Munlti-year experience in the research and operation of the Inguri HEPS arch dam allowed assessing the compliance of the mounted measuring systems with special control requirements and allocating the necessary amount of them for monitoring the strength and stability of the installation. The proposed methods of in-situ research data analysis based on the theory of probability, statistics and reliability were used in the design of the Hudoni HEPS dam.

Beach Morphodynamic Response to a Submerged Reef

To develop beach engineering, the submerged structure’s primary physical functions have to be understood. This study focuses on submerged structures in order to understand the strategy of reduced wave energy, stabilizing the shoreline and not generating erosion or adversely modifying coastal processes. Important developments have been made since the 1990s, taking into account the functions of recreational amenity. However, non-dimensional models cannot explain the physical mechanisms that generate accretion or erosion morphological features in the lee of the submerged structure. The present study aims to collaborate with the understanding of the mechanism of beach response to a submerged structure. For this, 26 surveys were made using topographic, Lagrangian, and Eulerian hydrodynamic measures during one seasonal cycle of a beach system from Rio de Janeiro (Brazil) with a natural submerged reef or rocky bank V-shape in the plan. This beach system is energetic and intermediate when referring to wave energy conditions and beach states, respectively. The wave breaking vector system on the rocky bank’s geometry was examined in the intermediate and dissipative beach morphodynamic organization. The variability of the wave breaking vector system determines the establishment, deformation, and erosion features in the lee of the structure. During high-energy waves, the submerged structure’s hydrodynamic and morphodynamic processes are transparent. When the submerged structure combines with the dissipative beach state, the surfing wave conditions are improved. These results provide the dimensional and positional references for an engineering proposal for a beach system.

Petasites kablikianus (Asteraceae) in the Slovak Carpathians: Distribution, chromosome number and genome size

The paper treats the distribution and ecological characteristics of the butterbur species Petasites kablikianus in the Slovak Carpathians (Central Europe). Study of herbarium specimens, review of published sources and results of field research show its wide distribution in northern and central Slovakia, mainly in wet biotopes such as gravel riverbeds and rocky banks of mountain streams. The majority of populations occur from the submontane to montane level (mainly at elevations of 600-1200 m a.s.l.) with the altitudinal maximum at ca. 1850 m a.s.l. Chromosome number analysis showed 2n = 60. The nuclear DNA content measured in leaves was 2C = 5.96 ? 0.17 pg, or 5828 Mbp. Characters used for determination are also discussed. A distribution map is attached.