Steep Sides Research Articles

Effect of Triton X-100 surfactant and agitation on tetramethylammonium hydroxide wet etching for microneedle fabrication

Solid silicon (Si) microneedles have many applications such as skin pretreatment to form micrometer-sized holes in the skin surface in transdermal drug delivery systems. Wet etching based on tetramethylammonium hydroxide (TMAH) is an efficient method to fabricate solid microneedles. However, it is challenging to increase the density of microneedle arrays due to the faster lateral etching than the vertical etching that requires a large initial mask size. In this work, we used wet etching based on TMAH to fabricate solid Si microneedles. One kind of nonionic surfactant, Triton X-100, was introduced into the TMAH solution to suppress the lateral etching. When Triton X-100 was added into TMAH for a given etching condition, the maximum height (attained right before the mask fell off) of microneedles could reach ∼230 μm for 600 μm square-shaped mask size and 700 μm array period, compared to microneedles of maximum 152 μm height for the same mask size and period without surfactant addition. Correspondingly, when the target heights of microneedles were the same as ∼230 μm, denser (down to 700 μm period, 600 μm mask size) microneedle arrays were achieved with the help of Triton X-100, in comparison to arrays down to 900 μm period (800 μm mask size) without surfactant addition. Furthermore, agitation by a magnetic stirring bar is important for the fabrication of dense solid Si microneedle arrays based on TMAH. The microneedle structures were rhombic pyramid in shape with Triton X-100 and agitation. But microneedle structures obtained with Triton X-100 yet without agitation were octagonal pyramid in shape with a much less steep side surface.

Evolution of the Lower Barun lake and its exposure to potential mass movement slopes in the Nepal Himalaya

The Lower Barun Lake, the largest glacier-fed lake in the Nepal Himalaya, has been designated as critically or highly vulnerable to Glacier Lake Outburst Floods (GLOFs) due to the lake's massive volume and steep side walls that are susceptible to mass movements. The current study estimates the future evolution of the lake's extent and its exposure to potential avalanche under different climate scenarios by simulating the evolution of the Lower Barun glacier, which feeds the lake. We then assess this exposure (i) at the lake's current extent, (ii) when the lake length grows to 75 % of its maximum length, and (iii) when the lake length reaches its maximum possible length. We use a mass conservation based numerical flowline model for our analyses. The model was forced by the glacier surface mass balance (SMB) and meteorological data collected from weather stations in Kathmandu, Nepal and Darjeeling, India. Modelled lake lengths matched measured lengths within an RMSE of ∼200 m. Analyses show that under SSP2–4.5 and SSP5–8.5 scenarios, the lake will reach its maximum length by 2075 ± 2 and 2061 ± 1, respectively. The largest uncertainty in future lake length fluctuations is approximately 200 m. Our study reveals that in current conditions, the zone where the angle of reach of potential avalanches is highest lies on the slopes along the right shore (south side) of the lake. The angle of reach shifts upstream and steepens—and the mass movement hazard increases—as the lake grows in the future.

Neotectonic deformations of the lakebeds in Esrum Sø, eastern Denmark, interpreted to indicate a Postglacial pull-apart basin.

Esrum Sø, with a marked elongation trending N–S, located in the glaciomorphological landscape of north-eastern Sjælland, is one of the biggest lakes in Denmark. The lake is shaped as a large ‘sink’ with steep sides and a maximum depth of c. 22 m. The present investigation and mapping of the structures of the lakebeds is based on the interpretation of 10 reflectors on 82 acquired high-resolution seismic sections (Chirp III) and correlation to the 8.5 m long Esrum Sø drill core in the northern part of Esrum Sø. A new formation, the Esrum Formation, with two members, the Fredensborg and Nødebo Members, is erected based on the geological information obtained from the drill core, and traced on the seismic sections over the major part of Esrum Sø. In the northern part of the lake, the seismic sections reveal a number of anti- and synform structures, which we group into five architectural features. The mapping of these structures show N–S trending vertical fractures, fault scarps and fold crests, which in places are bent towards a NW direction. In some, mainly southern, parts of the lake, gas stored in the gyttja (Nødebo Member) and close to the lake floor degrades the seismic signal significantly. The gas is ascribed to seepage and production close to the lake floor. The integration of the seismic interpretation and the Esrum Sø drill core data shows that the Young Baltic till constitutes the base of the depression where Esrum Sø is located. In Bølling to Preboreal time the Esrum Sø was a shallow freshwater lake with no tectonic activity (Fredensborg Member), and the major deformation and subsidence of the lake basin took place in Boreal to Atlantic time (Nødebo Member). Our interpretation favours a model of a Postglacial pull-apart basin related to extension in the wrench-fault tectonic zone aligned with the Sorgenfrei–Tornquist Zone.

Erosion, deposition and breach evolution of landslide dams composed of various dam material types based on flume tests

The accurate and rapid prediction of breach outflow rates of landslide dams is crucial for effective risk assessment and mitigation strategies. However, challenges arise due to the complexities associated with breaching mechanisms. In this study, 12 flume tests were conducted on landslide dams composed of various material types, including fine-grained, coarse-grained, well-graded, and gap-graded materials, each with two dry densities. This study comprehensively investigated erosion, deposition, and breach evolution, providing the foundation for the development of breach evolution models. A comprehensive logic diagram, focusing on shear stress and grain size distribution, was proposed to forecast the failure modes of landslide dams. The study also suggested a method to assess the longitudinal breach evolution based on the prediction of the Erosion Point (EP) and Deposition Point (DP), and to assess the lateral breach evolution by considering both steep and gentle breach side slopes. Our findings indicate that fine-grained materials undergo layer erosion, coarse-grained materials remain stable, well-graded materials develop erosion pits, and gap-graded materials are prone to piping. The existence of an interface can result in piping channels, even when the overall hydraulic gradient is insufficient to initiate piping. Incorporating the longitudinal slope angle and its influence on both driving and resisting forces into the traditional erosion rate equation can significantly enhance its accuracy, especially when coarse particles are present. Coarse particles play a pivotal role in erosion and deposition behavior and reshaping the breach evolution as the initiation of coarse particles is dominated by rolling instead of slipping in fine particles. Deposition on the downstream slope of a dam can significantly influence the longitudinal breach process, leading to changes in the downstream topography and grain size distribution. The proposed method for assessing longitudinal breach evolution unifies the previous methodologies by predicting the positions of EP and DP based on erosion and deposition.

Internal waves generated from asymmetric topographies

Previous experimental and theoretical research on tidally generated internal waves over oceanic topography has often used symmetric topographic profiles. However, due to the complex nature of real ocean topography, the effect of asymmetry cannot be overlooked. Studies have shown that topographic complexities, including asymmetry, can have a significant impact on internal wave generation, but topographic asymmetry has not yet been explored in a systematic manner. This work presents a comparison of tidally generated internal waves from nine different two-dimensional asymmetric topographies, consisting of a steeper Gaussian curve on one side, and a wider Gaussian curve on the other. The amplitude of the wider curve varies from 60% of the steeper curve to its equivalent. Two oscillation frequencies are tested. Kinetic energy density in tidally generated internal waves on each side of the topography is compared qualitatively and quantitatively, in both physical and Fourier space. When compared to similar symmetric topographies, waves generated by the asymmetric topographies varied distinctly in both magnitude and wavenumber distribution of kinetic energy density. Waves on the relatively steep side of the topography contain up to 50% more kinetic energy than on the wider side. However, there is very little kinetic energy at the higher wavenumbers associated with the steeper topography. Instead, the internal wavefield is dominated by lower wavenumbers, 50%–90% of the kinetic energy density is contained in wavelengths corresponding to the wider side of the topography. Decreasing the amplitude of the wider curve does not make an appreciable difference in the kinetic energy density spectrum. Thus, the differences quantified here are due solely to changing slope and show the effect which relatively slight asymmetry has on internal wave generation.

Investigation of coherent Fourier scatterometry as a calibration tool for determination of steep side wall angle and height of a nanostructure

Nanostructures with steep side wall angles (swa) play a pivotal role in various technological applications. Accurate characterization of these nanostructures is crucial for optimizing their performance. In this study, we propose a far-field detection method based on coherent Fourier scatterometry (CFS) for accurate quantification of steep swa and heights in cliff-like nanostructures. Our approach introduces a parameter termed ‘visibility’, derived from the unique far-field signatures of cliff-like nanostructures. This parameter serves as a quantitative metric for the calibration of swa and heights. The heightened sensitivity of our method is demonstrated, particularly when the incident polarization is perpendicular to the invariant direction of the nanostructure for swa calibration, while both polarization states exhibit sensitivity to height calibration. Furthermore, a comprehensive sensitivity analysis reveals the stable nature of our method, showcasing that even with fluctuations of ±10 nm in the position of the nanostructure, the resulting swa remains stable within a range of ±0.5∘ . The exponential variation of the visibility parameter with edge roundness is observed, with fluctuations in edge roundness within 10 nm resulting in swa variations within 1.7∘ for both polarization states. In experimental validations, our results demonstrate reasonable agreement between CFS-derived and AFM measurements. The AFM data for swa ( 77.99∘±1.37∘ ) and height (148.35 nm ±2.11 nm) are corroborated with CFS-derived value of swa ( 77.75∘±3.61∘ , 78.36∘±3.89∘ ) and height (149.42 nm ±1.66 nm, 150.05 nm ±1.04 nm) obtained from calibration curves for TM and TE incident beams, respectively. Overall, our findings underscore CFS as a potential and reliable tool for nanostructure characterization, offering precise measurements that are pivotal for advancing nanotechnology.

Temperature Inversion and Particulate Matter Concentration in the Low Troposphere of Cergy-Pontoise (Parisian Region)

This study aims to elucidate the influence of meteorological conditions on particle levels in Cergy-Pontoise. It explores the temporal variability of PM10 pollution days by associating them with the vertical temperature profile derived from conventional radiosondes from 2013 to 2022 (regional station). The results indicate that nearly 80% of exceedance days were associated with thermal inversions, primarily observed in winter and typically lasting 1 to 3 days. Analysis of winter thermal inversion characteristics suggests that those linked to pollution primarily occur near the ground, with higher intensity in December (12.1 °C) and lower in February (10.3 °C). Persistent inversions (extended nocturnal by diurnal inversion) account for 91.4% of the total inversions associated with high concentrations. Captive balloon soundings and temperature measurements at different altitudes were conducted during the winter of 2022/2023 to clarify thermal inversion in the Oise Valley at the center of Cergy-Pontoise. The results highlight three nocturnal wind circulation mechanisms in the valley, including downslope flow, circulation influenced by an urban heat island, and mechanical air evacuation under an inversion layer towards the less steep East side of the valley. Analysis of PM with the temperature gradient in the Oise Valley shows a significant correlation, suggesting an increase in concentrations during locally detected inversions and a decrease during atmospheric disturbance.

Rock anchor hanger effect on single-tower earth-anchored suspension bridge mechanical performance: An analytical model and multi-objective golden eagle optimization

The application of a composite saddle in single-tower earth-anchored suspension bridges (STEASBs) replaces the tower on the steep slope side, which is a cost-effective solution that improves bridge safety and provides environmental protection for the steep bank slope of the valley. However, this novel bridge design needs an appropriate model to evaluate the effect of rock anchor hangers on the structure in the non-girder area and adjust their parameters to optimize the mechanical response of the whole bridge structure. This study proposes an approach to quickly evaluate the most unfavorable load cases of the STEASB and further optimizes the structural parameters of rock anchor hangers to enhance structural safety. An analytical model for the STEASBs under the live load is proposed and verified by the finite element model (FEM), with the maximum relative error not exceeding 7.37%. Combined with the golden eagle optimizer (GEO), the most unfavorable load cases of the corresponding design indices are yielded. The Pareto optimal solutions for the spacing, cross-sectional area, and initial tension of the vertical rock anchor hangers are obtained through multi-objective optimization to improve the mechanical behavior of STEASBs. In addition, it is clarified that the main function of rock anchor hangers is to reduce the peak value of the stress amplitude of the hangers and girder-end rotation, providing a theoretical basis for the STEASB design.

A Micro-Topography Measurement and Compensation Method for the Key Component Surface Based on White-Light Interferometry.

The grinding grooves of material removal machining and the residues of a machining tool on the key component surface cause surface stress concentration. Thus, it is critical to carry out precise measurements on the key component surface to evaluate the stress concentration. Based on white-light interferometry (WLI), we studied the measurement distortion caused by the reflected light from the steep side of the grinding groove being unable to return to the optical system for imaging. A threshold value was set to eliminate the distorted measurement points, and the cubic spline algorithm was used to interpolate the eliminated points for compensation. The compensation result agrees well with the atomic force microscope (AFM) measurement result. However, for residues on the surface, a practical method was established to obtain a microscopic 3D micro-topography point cloud and a super-depth-of-field fusion image simultaneously. Afterward, the semantic segmentation network U-net was adopted to identify the residues in the super-depth-of-field fusion image and achieved a recognition accuracy of 91.06% for residual identification. Residual feature information, including height, position, and size, was obtained by integrating the information from point clouds and super-depth-of-field fusion images. This work can provide foundational data to study surface stress concentration.

Modelling Water Erosion and Mass Movements (Wet) by Using GIS-Based Multi-Hazard Susceptibility Assessment Approaches: A Case Study—Kratovska Reka Catchment (North Macedonia)

Kratovska Reka is a short (17.3 km) left tributary of Kriva Reka, whose watershed (68.5 km2) is located on the northwestern slopes of the Osogovo Mountains (North Macedonia). Due to the favorable natural conditions and anthropogenic factors, the Kratovska Reka catchment is under a high risk of natural hazards, especially water erosion and landslide occurrences. For this reason, the paper presents an approach of modelling of potential erosion and areas susceptible to the above-mentioned hydro-meteorological hazards in the Kratovska River catchment. Firstly, this study analyzed the main geographical features that contribute to intensive erosion processes in the area. Then, using the Gavrilović EPM erosion potential method, an average value of 0.56 was obtained for the erosion coefficient Z, indicating areas prone to high erosion risk. Furthermore, by using landslide susceptibility analysis (LSA), terrains susceptible to landslides were identified. The results shows that 1/3 of the catchment is very susceptible to mass movements in wet conditions (landslides). According to the combined multi-hazard model, 3.13% of the total area of the Kratovska River catchment is both at high risk of landslides and under severe erosion. The Kratovska River catchment is significantly endangered by the excessive water erosion processes (39.86%), especially on the steep valley sides, i.e., terrains that are completely exposed, under sparse vegetation, and open to the effects of distribution/concentration of the rainfall amounts throughout the year. Identifying locations with the highest erosion risk serves as the initial step in defining and implementing appropriate mitigation measures across local and regional scales, thus enhancing overall resilience to environmental challenges.

Improving the diffraction efficiency of structures in direct laser writing using obliquely incident beams: modeling and experiment

A brief review of methods for increasing the diffraction efficiency of optical elements synthesized by direct laser writing is done. It is noted that the previously proposed methods for recording the topology of similar elements using volumetric or surface contour masks do not provide an ultimate solution to a problem of increasing the diffraction efficiency. The performed model and physical experiments on the fabrication of structures of surface-relief phase optical elements by recording zone profiles using oblique laser beams show the fundamental possibility of forming steep side walls of the reverse zone slopes and the feasibility of developing this technology based on laser image generators.

Analytical investigation of trapped waves over a submerged exponential ridge

Based on the linear shallow-water equations, analytical solutions for trapped waves over an asymmetric oceanic ridge with an exponential cross-sectional profile are presented. The solutions can become those for a symmetric ridge by setting the same topographic parameter for both sides, in which there are both symmetric and asymmetric trapped waves. The dispersion relationships imply that the wavenumber is related to not only the frequency and water depth at the top of the ridge but also the cross-section profile parameters and the mode number. With increasing frequency, the phase velocity decreases rapidly and approaches the classical shallow-water wave velocity for fixed water depth at the top and profile parameters. Meanwhile, for increasing angular frequency, the energy velocity first increases sharply from less than the shallow-water wave velocity and then decreases gently toward it. For an asymmetric ridge, the amplitude profile is confined to a narrower region on the steeper side and spread in a wider region on the less-steep side. Finally, the analytical solutions are applied to reveal the trapping effect of the Hawaii ridge on the 2011 Tohoku Tsunami in the North Pacific.

Salair–Gornaya Shoria Junction (Northwestern Central Asian Orogenic Belt): Deep Structure and Tectonics from Magnetotelluric Data

Abstract —The Salair fold-thrust orogenic belt (Salair orogen, Salair) is located in the northwestern Altai–Sayan fold area within the Central Asian Orogenic Belt. The Salair orogen is an allochthon overriding the Kuznetsk Basin on a system of imbricate thrusts. The southern flank of the Salair thrust system is tectonically juxtaposed against the Gornaya Shoria terrane which differs markedly from Salair in its geological setting. The Salair and Gornaya Shoria terranes are separated by the Nenya-Chumysh Basin, a deep Mesozoic trough. The Salair orogen is composed of Cambrian–Early Ordovician island arc volcanic and sedimentary rocks, widespread garnet amphibolites and gneisses of the Angurep complex in its southern flank, and the Shalap subduction-related melange in the Alambai ophiolite suture. The southern Salair orogen and its junction with Gornaya Shoria have been imaged down to the lower crust by magnetotelluric (MT) soundings, which is an efficient tool for investigating the deep structure and tectonic history of orogenic areas. The MT surveys were performed at 25 stations on a 120 km long profile. MT data revealed an up to 70 km wide low-resistivity zone (a conductor) traceable till a depth of 20 km between the Salair and Gornaya Shoria terranes. The low-resistivity zone has a complex structure with its outer and interior boundaries dipping almost vertically. The conductor lies under several major geological structures: the Shalap melange, the Nenya-Chumysh Basin, and the NE trending Altai–Salair right-lateral strike-slip fault. The Altai–Salair fault, along which the Salair allochthon was displaced relative to Gorny Altai and Gornaya Shoria, joins the Salair system of imbricate thrusts. The Nenya-Chumysh Basin at the Salair–Gornaya Shoria junction is a deep trough having an asymmetric transversal profile with a steep western side and a shallower-dipping stepped eastern side. The southeastern flank of the basin is a wide area of thin sediments over the Paleozoic basement dipping gently in the northwestern direction. The revealed deep structure of the Nenya-Chumysh trough is consistent with its tectonic model implying an Early Cretaceous basin superposed over an early Jurassic pull-apart basin. Early Mesozoic motions on major faults is a regional-scale phenomenon known from many areas of southern West Siberia.

Ground Investigations and Detection and Monitoring of Landslides Using SAR Interferometry in Gangtok, Sikkim Himalaya

The Himalayan state of Sikkim is prone to some of the world’s largest landslides, which have caused catastrophic damage to lives, properties, and infrastructures in the region. The settlements along the steep valley sides are particularly subject to frequent rainfall-triggered landslide events during the monsoon season. The region has also experienced smaller rock slope failures (RSF) after the 2011 Sikkim earthquake. The surface displacement field is a critical observable for determining landslide depth and constraining failure mechanisms to develop effective mitigation techniques that minimise landslide damage. In the present study, the persistent scatterers InSAR (PSI) method is employed to process the series of Sentinel 1-A/B synthetic aperture radar (SAR) images acquired between 2015 and 2021 along ascending and descending orbits for the selected areas in Gangtok, Sikkim, to detect potentially active, landslide-prone areas. InSAR-derived ground surface displacements and their spatio-temporal evolutions are combined with field investigations to better understand the state of activity and landslide risk assessment. Field investigations confirm the ongoing ground surface displacements revealed by the InSAR results. Some urban areas have been completely abandoned due to the structural damage to residential housing, schools, and office buildings caused by displacement. This paper relates the geotechnical investigations carried out on the ground to the data obtained through interferometric synthetic aperture radar (InSAR), focusing on the triggering mechanisms. A strong correlation between seasonal rainfall and landslide acceleration, as well as predisposing geological-structural setting, suggest a causative mechanism of the landslides.

Use of emerging technologies to help measure fjordic biodiversity and blue carbon: mini-manned submarines and autonomous underwater vehicle swarms

Meaningful protection of global oceans lags far behind that of land and has taken little consideration of climate mitigation potential to date (such as through assessment of blue carbon stocks and change). With the new emphasis on synergistic approaches to the identification and conservation of both carbon- and species- rich habitats, we need much better knowledge of the geography and status of blue carbon habitats beyond coastal wetlands. In subpolar and polar regions, some blue carbon habitats are still emerging and work as negative (mitigating) feedback on climate change, yet remain unprotected despite strong evidence of threat overlap. Scientific research expeditions are gradually increasing our understanding, but appropriate vessels are a limiting factor due to high costs and carbon footprints. Even when available such vessels cannot access all areas (e.g. remote fjords with sills) and may struggle to measure certain aspects of habitats (e.g. steep or vertical surfaces). New technologies and opportunities have advanced to aid some of these problems, and here, two of them are considered, mini-manned submersibles and autonomous underwater vehicles. These two platforms have both become much more available and affordable (through novel partnerships) while also being much more scientifically capable. This technology has the potential to reduce the carbon footprint of science and particularly aid in assessing biology and environment status and change on steep sides, such as fjord walls.

Soil Erosion Assessment Using the RUSLE Model, Remote Sensing, and GIS in the Shatt Al-Arab Basin (Iraq-Iran)

In the Shatt Al-Arab basin, soil erosion is a major problem due to the steepness of the terrain and the significant difference in altitude between the upstream and downstream parts of the basin. Vast quantities of soil are moved annually, resulting in massive repercussions including soil degradation, structural damage, biodiversity loss, and productivity reduction in the catchment area, huge sediment load, and the pollution of streams and rivers. Consequently, the assessment of soil erosion risk and geographical distribution is essential for constructing a database for developing effective control strategies. Revised Universal Soil Loss Equation (RUSLE) was combined with Remote Sensing (RS) and Geographic Information System (GIS) in the current work to define the soil erosion hazard map in the Shatt Al-Arab basin. The RUSLE model included various characteristics for soil erosion zonation including rainfall erosivity, soil erodibility, slope length and steepness, land cover and management, and conservation support practices. Annual erosion rates in this study in tons per hectare were: extremely high (more than 50); very high (50 to 16.5); high (16.5 to 2.2); medium (2.2 to 1); and low (1 to 0) ton ha−1year−1 representing 16, 4, 13, 7, and 60 % of the basin’s area, respectively. The high soil loss rates are associated with heavy rainfall, loamy soil predominance, elevated terrains/plateau borders with a steep side slope, and intensive farming. Managers and policymakers may use the results of this study to implement adequate conservation programs to prevent soil erosion or recommend soil conservation acts if development projects are to proceed in places with a high soil erosion risk.

Through Thick and Thin

Through Thick and Thin

Numerical simulation of dam-breach flood waves

Dam breach due to the earthquake, Land sliding inside the dam reservoir, dam overtopping as a result of intense precipitation in a watershed are examples of dangerous risks which flood caused by any of them should be predicted by suitable hydraulic or numerical models in the framework of a risk management plan. In the present research, 2DHec-Ras model has been applied in order to flood modeling of Sattarkhan dam. This dam is in the North West of Iran, located 15 km from the west of Ahar city, in the East Azerbaijan province, Iran. The downstream part of the dam to Ahar city has been studied considering the population and infrastructures in this district according to two different scenarios of dam failure. The first scenario includes piping of flow and dam failure profile with steep side walls while the second scenario consists of inclined sidewalls in the dam breach profile and overtopping of flow as the main cause of breaching. The population centers have been selected in the downstream area of dam according to the field facts. The maximum flood depth reaches up to 9.1 m for the first scenario and 7.1 m for the second scenario at the Islamic Azad University and Tabriz-Ahar road, respectively. The results show the notable risk for some of the population centers in the downstream of the dam. Furthermore, the arrival time of flood, recession time, and maximum velocities in the targeted areas for preparing emergency action plans has been calculated.

Kinematics of the molecular interstellar medium probed by Gaia: steep velocity dispersion–size relation, isotropic turbulence, and location-dependent energy dissipation

ABSTRACT The evolution of the molecular interstellar medium is controlled by processes such as turbulence, gravity, stellar feedback, and Galactic shear. AL a part of the ISM-6D project, using Gaia astrometric measurements towards a sample of young stellar objects (YSOs), we study the morphology and kinematic structure of the associated molecular gas. We identify 150 YSO associations with distance $d \lesssim 3 \,\,\rm kpc$. The YSO associations are elongated, with a median aspect ratio of 1.97, and are oriented parallel to the disc mid-plane, with a median angle of 30°. The turbulence in the molecular clouds as probed by the YSOs is isotropic, and the velocity dispersions are related to the sizes by σv, 2D = 0.74 (r/pc)0.67 (km s−1) . The slope is on the steeper side, yet consistent with previous measurements. The energy dissipation rate of turbulence $\dot{\epsilon } = \sigma _{v,{\rm 3D}}^3 /L$ decreases with the Galactocentric distance, with a gradient of 0.2 $\rm dex \,\, kpc^{-1}$, which can be explained if turbulence is driven by cloud collisions. In this scenario, the clouds located in the inner Galaxy have higher chances to accrete smaller clouds and are more turbulent. Although the density structures of the complexes are anisotropic, the turbulence is consistent with being isotropic. If the alignment between density structures and the Galactic-disc mid-plane is due to shear, we expect $t_{\rm cloud} \gtrsim t_{\rm shear}\approx 30\,\, \rm Myr$. This cloud lifetime is longer than the turbulence crossing time, and a continuous energy injection is required to maintain the turbulence.

Assessment of Groundwater Potential Zones of Upper Blue Nile River Basin Using Multi-Influencing Factors under GIS and RS Environment: A Case Study on Guder Watersheds, Abay Basin, Oromia Region, Ethiopia

Groundwater is the most crucial resource for human beings and plays an important role in combating climate change and is substantial to human existence on the globe. Overall increased demand for water in different sectors, population growth, and unreliable rainfall necessitates the planning and management of groundwater. In this study, groundwater potential zones are delineated by combining remote sensing and geographical information system techniques in the Guder watersheds of the Upper Blue Nile Basin. Groundwater potential zones are prepared by using various multi-influencing factors like geomorphology, land use/cover, lithology, soil type, soil texture, drainage density, slope, lineament, rainfall, and elevation. These influencing factors’ features were given appropriate weightage according to Saaty’s AHP method, expert judgment, and their relative significance for groundwater occurrence. The groundwater potential zone was classified into different categories as very poor, poor, moderate, good, and very good according to quantile classification. This study reveals that about 33.6% of the Guder River Basin represents a good andvery good GWPZ category with an equal value of 16.8%,; while values 23.3%, 20.2%, and 22.9% were denoted by very poor, poor, and moderate groundwater potential zone, respectively. GWPZ was validated by field-collected data such as well discharge and soil depth. An accepted similarity was observed between delineated GWPZ and the basin’s soil depth graphically. The results of this study were also verified by correlation and kappa statistics values of 0.73and 77%, respectively. The study is certain with a sensible dimension of consistency in pairwise comparison between influencing and the overall weightage. The very high GWPZs are found in the northern part starting from the center longitude of the study area, more along with the northwestern, southern, and southwestern of the Guder subbasin. Low to very low groundwater potentiality has been seen at different distances from the center due to the presence of escapements, hills and steep side slopes, slopes, and rock surfaces. The study also revealed that the zone of high groundwater potential has high soil depth, and the zone of low groundwater showed low soil depth as the capacity of the aquifer to store water may depend on the depth of soil profile. This study attests to the GIS and remote sensing techniques as an effective model for delineation of GWPZs and can be applied at other basins of Ethiopia.