Assessment of the Potentiality to the Debris-Flow Occurrence from Physiographic and Morphometrics Parameters: a Case Study in Santo Antônio Basin (Caraguatatuba, São Paulo State, Brazil)

This work aims to evaluate the potential for the debris-flow triggering from Santo Antônio hydrographic basin, located in the Serra do Mar region on North Coast of the State of São Paulo, Brazil, based on physiographic attributes, rainfall data, and morphometric parameters. For this purpose, hydrographic basin techniques were applied, assessing the vulnerability to the debris flow from geomorphological, geological, climatic, and anthropic aspects, and morphometric parameters relevant to the triggering of these processes in watersheds were calculated. Seven physiographic units were identified, which supported the understanding of geological and geomorphological aspects of the basin: coastal plains; river plains; colluvium and talus ramps; escarpments of Serra do Mar; upland of Paraitinga; mountainous relief and hillocks domain. The sub-basins located in steep sections of the relief, with high slopes, valleys, and channels docked, high drainage densities present higher values in the morphometric parameters, indicating a greater potential for triggering and occurrence of debris-flow processes. The joint analysis of physiographic compartmentalization with the identification of relief features, slope, amplitude, valley, slope shapes and morphometric parameters, is extremely relevant to recognize hydrographic basins susceptible to debris flows, as it integrates, and correlates aspects of the physical environment considered to trigger in the occurrence of these processes.

Geological environment evaluation of river valley slope projects based on remote sensing technology

The method to evaluate the geological environment of river valley slope projects has a small precision in determining the weight of geological environment evaluation index, which leads to a large error between the results of geological environment evaluation and the actual value of river valley slope projects. Therefore, the reverse research of the geological environment evaluation of river valley slope projects based on remote sensing technology is proposed. Remote sensing technology is used to build the projects’ geological environment evaluation framework of river valley slope, on this basis, the Delphi method is used to preliminarily determine the geological environment evaluation index, the cluster analysis is used to screen the evaluation index, the evaluation system of projects’ geological environment is constructed, the AHP method is used to calculate the evaluation index weight, and the corresponding remote sensing image number is obtained according to the projects’ geological environment evaluation system. According to the data, the corresponding software is used to preprocess it, and the remote sensing data of projects’ geological environment is obtained. The grey evaluation method is constructed based on AHP to realize the evaluation of geological environment of river valley slope projects. The experimental results show that compared with the existing methods, the evaluation error of the proposed method is smaller, which fully proves that the application performance of the proposed method is better.

Evaluation of Anthropogenic Substrate Variability Based on Non-Destructive Testing of Ground Anchors

The purpose of this paper is to describe the variability of soil rheological properties based on research carried out using load tests of ground anchors under complex geotechnical conditions. The heterogeneity of soil should always be considered when designing geotechnical constructions. In the present case, the earthwork created at the Warsaw Slope revealed an embankment of anthropogenic origin, located in a geologically and geomorphologically complex area of the Vistula valley slope. Excavation protection was anchored mainly in soils of anthropogenic origin. When the acceptance tests of the ground anchor were completed, the subsoil randomness was confirmed using nondirect, geostatistical methods. A standard solid rheological model with nonlinear fitting to the data was used. This model was established to describe the creeping activity of the ground anchor more accurately. The characteristics of man-made embankments were described using the parameters obtained with the rheological model of the subsoil.

Measured Pipe Stresses on Gas Pipelines in Landslide Areas

Landslides are a risk to buried gas pipeline infrastructure, but these risks are particularly difficult to assess given the complex nature of landslide movements. This paper presents of portion of research conducted at the University of Manitoba where gas pipelines within active landslide areas were monitored over a four-year period. Two locations were examined in Western Manitoba within the Assiniboine river valley where a shallow natural gas pipeline runs parallel to the valley slope. A field investigation and monitoring program was undertaken where surficial ground movements and soil and pipe temperatures and pipe strains through strain gauges were measured. Monitoring results identified soil near the pipeline does not freeze, and ground movements are <50 mm/year. The monitoring results also showed pipe stresses and behaviour were affected by backfilling, thermal changes, soil-pipe relaxation, and ground movements. An unexpected outcome of the research was the response of the pipeline to slight ground movements was easily captured by the strain gauges and these movements, slow or surges tended to occur at the same time between the two sites suggesting movements occur due to regional environmental affects.

Rockfall hazard in the Imja Glacial Lake, eastern Nepal

In Nepal, rockfall related studies are rarely conducted and are limited to the landslide study along with few case studies on rockfall events. Rockfall problems in Nepal are more frequent in the Higher Himalayan region than Midland and Lesser Himalayan regions. In the glaciated valley and glacial lakes, rockfall and associated tsunami like huge wave are a recently initiated research. In this context, a glacial lake of the Himalaya, named as Imja Glacial Lake situated in eastern Nepal has been selected to understand the rockfall problems and their possible consequences. The lake was formed at the end part of the Imja glacier. The northern valley slope of Imja Glacier Lake, i.e. southern slope of the Island Peak has serious problem of rockfall into the lake. Rockfall simulation was performed during this research with field data. Three different Plots were defined for simulation of rockfall. Among them, Plot III seems to be the most hazardous since the detached boulders on the higher elevation can enter into the lake with the maximum velocity of 40 m/s with pre-impact energy more than 3500 kJ. This can develop a surge in the lake water that can break moraine dam. This leads to a serious threat to the downstream communities. Moreover, this research confirms that the rockfall hazard in the higher mountain region of Nepal is critical to creating flash floods due to tsunamis like surge in the lake water and breaching of the dam.

Failure Mechanism and Mitigation Measures of the G1002 Electricity Pylon Landslide at the Jinping I Hydropower Station

On August 29 and 30, 2012, local extreme rainfalls struck the construction area of the Jinping I Hydropower Station, Xichang, China, and triggered many geohazards. The upper region of the left valley slope 200 m downstream of the dam failed and slid, exposing the D-pile of the G1002 electricity pylon and threatening the entire power transmission line. Therefore, guaranteeing the stability of the residual soil masses in the rear area of the main scarp and the safety of the G1002 electricity pylon became a primary emergency task. Geological field surveys, topographical mapping, study of the failure mechanisms, and stability evaluations were carried out from October 12, 2012, to November 7, 2013. It is revealed that the failure mechanism of the G1002 electricity pylon landslide is flood-induced tractive sliding along the interlayer between the colluvium and the bedrock, significantly influenced by heavy precipitation and frequent blasting activities during the dam construction. The residual soil masses around the G1002 electricity pylon foundation are unstable under rainfall conditions. In order to ensure the stability of the residual soil masses and pylon foundation, a mitigation measure of the anchor cables combined with lattice frame beams was proposed and applied in practice. This paper provides insights into the problems associated with the selection of the locations of electricity pylons in ravine regions as well as mitigation strategies for similar landslides.

Out of equilibrium sinuosity: The development of incised meandering channels in response to base-level fall

&lt;p&gt;Meandering rivers and valleys are dominant landscape features on Earth and Mars, and central to a geomorphological debate: do sinuous channels actively develop during steepening of regional slope or whether they inherited the sinuosity of an ancient meandering channel through vertical incision? This and related questions were studied by field-scale case studies of channel evolution, numerical simulations, and physical laboratory experiments. Here, we document and investigate decadal- and field-scale formation of meandering valleys in perennial channels. These channels have incised into a homogeneous erodible substrate in response to the progressive Dead Sea level fall in recent decades (&gt;30 m over 40 years). This unique study area enabled analysis of three clusters of adjacent elongating and incising channels with stable confined discharge, that evolved through an active increase in regional and channel slopes. The emerged slopes greatly vary along the study area and channels, allowing the test of slope impact under three primary settings: (a) relatively long and low gradients on shelf-like margins, (b) sharp basinward gradient increase on a shelf-slope transition, and (c) steepening slopes. These clusters triggered different channel and valley response by means of stream incision depth, channel sinuosity, and valley width. The sinuosity of the channels was actively increased only following steepening in the valley slope. During stable valley slope, the channels were mainly incising vertically, inheriting previous sinuous pattern. The highest sinuosity was developed in the channel within the most steepening slope, that was also developed the deepest and widest valley. Together with the Jordan River response to the same Dead Sea level fall in recent decades, these insights promote the interpretations regarding the evolution of incised meandering channels under changes in regional slope. Abundant evidence for chute cutoffs along an incised channel can imply that frequent overbank floods prevailed in the channel during the incision, whereas the absence of or rare evidence for such cutoffs can be the result of infrequent high-magnitude floods during the evolution.&lt;/p&gt;

Genesis of giant, bouldery bars in a Miocene gravel-bed river: Insights from outcrop sedimentology, UAS-SfM photogrammetry, and GPR

ABSTRACT Bedsets of bouldery intraformational conglomerate partly fill a narrow, 40-m-deep paleovalley in the Arikaree Group (lower Miocene) in Nebraska, USA. Entire bar successions are exposed in 3D, offering an opportunity to improve upon sedimentological models for coarse-grained fluvial deposits. Using unmanned aircraft, structure-from-motion photogrammetry, and ground-penetrating radar, we offer the first comprehensive assessment of the lithofacies and stratigraphic architecture of this regionally unique fluvial conglomerate. We interpret three lithofacies associations: (1) beds of chaotic breccias lining the exhumed valley wall (colluvium), (2) &lt; 5-m-thick units dominated by horizontal to gently inclined (2–3°) beds of granule to pebble conglomerates, and (3) 10–24-m-thick units of steeply inclined (∼ 30°) beds of bouldery conglomerates, which dominate the channel fill. The deposit comprises at least four stories, but its thickest part is a deep scour filled by a single story of steeply inclined bouldery deposits. The direction of accretion of the giant bars was toward the paleovalley wall, where contemporaneous valley-side colluvium and bar deposits are juxtaposed. We propose that increased discharge in a high-order trunk stream rapidly eroded the friable sandstone of the underlying Monroe Creek–Harrison formations, amassing resistant, large concretions that were subject to valley-slope mass movements and fluvial transport (subaqueous traction, grainflow, and debris flow). Giant accretion surfaces formed as fluvial bars migrated over the edges of deep scours. Thus, the funneling of increased discharges through a confined paleovalley amplified the magnitudes of valley and bed erosion, water depth, stream competence, and bar thickness, preserving an exceptionally thick, coarse-grained deposit.

Smykiv – the new key section of the upper pleistocene of the Volyn Upland

Formulation the problem. The new section at Smykiv in the Volyn Upland has an informative stratigraphic record, showing details of climatic phases in the Late Pleistocene. The site is located in the Rivne Oblast, 40 km south of Lutsk, on slope of the River Dezha (the tributary of the River Styr). Review of previous publications and studies. The loess-palaeosol sequence of the Volyn’ Upland has been intensively studied by Ukrainian, Russian and Polish researchers such as A. Bogucki, M. Lanczont, P. Voloshyn, A. Tsatskin, V. Nechaev, T. Morozova, L. Bezusko, J. Kusiak, S. Fedorowicz, J. Nawrocki, R. Dmytruk and many others. Methods. The section has been studied using lithostratigraphic, palaeopedological, palaeocryological, grain size, micromorphological and partial chemical methods, which enable the reconstruction of past climate and environment. The stratigraphy is applied follows the Quaternary Framework of Ukraine (Veklitch et al., 1993). All the stratigraphical units of the Upper Pleistocene are represented in the section; and, herein, these divided into smaller parts characterized by distinct environmental histories. The purpose of the article is to study the detailed stratified sequence at Smykiv by various methods in order to clarify the regional Quaternary palaeogeographical scheme. Results. The periglacial alluvium of the Dnipro unit, at the base of the sequence, and the analysis of the position of the site in the relief indicate the interpretation that it is located on the Dezha river’s terrace. The alluvium bed is distorted by syngenetic involutions. The overlying Kaydaky unit truncates the alluvium, and is inclined parallel to the present valley slope. Three pedogenetic phases during the Kaydaky times are identifiable: pedosediments formed in the first phase (kda), pedosediments of forest soil formed in the early optimum (kdb1) and a Retisol formed in the late optimum (kdb2). During the Tyasmyn cold event, a network of small soil veins formed. Renewed, but less intense than in the Kaydaky unit, erosion processes started in Pryluky times. It can be demonstrated that the Pryluky polygenetic soil was formed in three phases, divided by a cold event in mid Pryluky times (pl2). A Chernozem with signs of slight podzolisation and biogenic aggregation was formed during the first phase (pl1b2). The soil is disturbed by cryogenic features formed during pl2. An incipient Cambisol was enriched with a fine organic matter during the phase pl3b1. An incipient Calcic Cambisol (pl3b2), aggregated and slightly gleyed, formed at the end of the Pryluky time. Erosion processes were not strongly developed during Pleniglacial. At the beginning of the stadials (in Uday and Bug times), solifluction processes occurred. At the beginning of these stadials, other cryogenic features, such as soil veins, frost fissures and ice-wedges, were also formed. Upper Pleistocene loess beds show slight pedogenesis, particularly very weak humus accumulation and biogenic aggregation. Furthermore, all Pleniglacial units are enriched in carbonates in diverse forms: however, the most common is disperse powdery lime. These last are frequently interpreted as being the result of calcite crystallization under cryogenic processes. During Vytachiv and Dofinivka interstadial times, boreal soils were formed – Gleyic Cambisol and Calcic Gleyic Cambisol, respectively. The first is mostly represented by pedosediments (indicating intense erosion), whereas the second soil is preserved in situ and it is enriched in fine organic matter and is well-microaggregated. The last loess unit of the Upper Pleistocene, the Prychornomorsk loess unit, is subdivided into two loess subunits (pc1 and pc3) which are connected with cryogenic events, and a Gleysol (pc2), indicating a relatively warm period.