Assessment of denudation rate and erosion susceptibility in the upper Tamakoshi basin in the higher Himalayas, Nepal

The higher rate of slope erosion in the Himalayan basins is contributing to rapid change in landform in the mountainous terrain, which has caused sedimentation, and inundation downstream. The Tamakoshi basin is a trans-boundary river that originates from Tibet and flows through Dolakha and Ramechap districts before joining the Sapta Koshi river. Few studies exist in Nepal attempting to quantify the erosion rate and susceptibility. However, they are scattered and mainly focus on either rill-sheet erosion or landslide only. Hence, this study attempted to estimate slope erosion by applying the Revised Universal Soil Loss Equation (RUSLE), and soil and debris erosion from landslide (2000-2019). Spatially distributed erosion intensity maps derived from the RUSLE model, as well as index-based landslide susceptibility map, were integrated to capture both running water and gravity erosion processes. The novelty of this research is that it examined the soil erosion rate using a process-based model as well as from the soil or rock displaced by the observed landslides over the last 20 years. The study estimated gross annual erosion by running water of 9.1million tons/yr, equivalent to the denudation rate of 3.34 mm/yr. Of these, landslide erosion accounts for 7.6 million ton/yr, i.e., 2.88 mm/yr, this covers about 84% of total slope erosion. High landslide and erosion potential areas are associated with high rainfall, steep slopes, scarps, lower segment of valley side slopes, high relief, and highly fractured and deformed parts of high-grade metamorphic rocks, such as gneiss, quartzite, marbles, migmatite, and granitic gneiss.

Human palaeoenvironment in the Upper Kama River basin: experience of reconstruction

Here, we present the results of comprehensive (archaeological and palaeoecological) studies undertaken in 2014–2018 in the basin of the Upper Kama River in the north of Perm Region, eastern part of the East European Plain. The main objects for the research were archaeological sites, primarily their chronological attribution and localization specifics. In total, 100 sites belonging to a wide chronological range from the Mesolithic to the Late Middle Ages were identified in the study area. The palaeochannel method was used to identify the association of the archaeological sites to certain landscapes within the river valley. As a result, five morphologically diverse sectors have been identified. For the reconstruction of natural landscapes and plant communities, palynological and plant macrofossil methods were used. Radiocarbon analysis was used to date these events. The initial human habitation of the Upper Kama region took place in the early Holocene, after the formation of the 2nd and 1st river terraces. The Mesolithic sites have been dated to this period. They were located either on the second river terrace, or on the bedrock valley side. In the Middle Holocene, along with the spread of broad-leaved species in forests, 6th–5th floodplain generations were formed, and the river was characterized by high water content. The Neolithic sites located on the Kama river terraces belong to this period. In the end of the Middle Holocene, the maximum distribution of spruce forests began. This was the time of existence of the Garin Chalcolithic Culture settlements. They were located either on the 4th–5th floodplain generations, or on the bedrock valley side. In the end of the Subboreal and first half of the Subatlantic periods, a key role in the forest stand was played by pine, forming southern taiga light coniferous forests. The water content of the Kama decreased. The sites of the Early Iron Age, located on low terraces or in the floodplain, are dated to this time. In the second half of the Subatlantic period of the Holocene, forests acquired modern mid-taiga appearane, which coincided with the arrival of the medieval population. Medieval hillforts were located on the bedrock valley sides, and the settlements were associated with river terraces, shores of oxbow lakes and floodplains of small rivers.

Changes in floodplain geo-ecology in the Belgian loess belt during the first millennium AD

Variation in human activities has greatly impacted the processes and intensities of erosion, sediment transport and storage throughout the Late Holocene, and many lowland rivers around the world have responded to these variations. Although this long-term process–response relationship has been established before, the effects of short-term (c.200-year) changes in human impact on lowland rivers are less well studied. Here, we followed an integrated approach whereby observations of floodplain changes are evaluated against detailed data on human impact for three lowland rivers in the Belgian loess belt: Dijle, Mombeek and Gete rivers. Pollen data were used to reconstruct changes in local and regional vegetation and to calculate human impact scores. Corings along transects and a database of c.160 radiocarbon ages were used to reconstruct geomorphic changes in the river valleys. Our results show a decrease in human impact between 200 and 800 AD, which can be related to the decreased population density in Europe during the first millennium AD. During this period, forests in the studied catchments regenerated, soil erosion decreased, hillslope–floodplain connectivity decreased due to the regeneration of valley-side vegetation barriers, and sediment input in the floodplain decreased. A reaction to this decreased human impact can be observed in the river valleys during the first millennium AD, with a regrowth of the alder carr forest and an increase in the organic matter content of the alluvial deposits with a local reactivation of peat growth. The observed trajectories of Belgian river valleys during the first millennium AD provide more insight into the sensitivity of these river valleys to short-term variations in human impact. These results can in turn be used to better estimate the effects of future changes in the catchments on the fluvial system.

Performance Assessment of Crash Barriers used in Road Safety: A Case Study of Malekhu Kurintar Section of the Prithvi Highway

Hill roads in Nepal are comprised of critical geometry and limited roadway clearances. It causes high number of runoff roadway type of accidents with single vehicle. These accidents often carry huge number of fatalities and severe injuries. Installation of crash barriers is the most effective way of preventing such accidents along hill roads. However, the existing practice of construction of crash barriers does not show the satisfactory results. Therefore, this research aimed at the evaluation of typical crash barriers constructed along the valley side of highway. Analysis of the road accident of Malekhu-Kurintar section of Prithvi Highway record shows that this section has relatively higher accident rate and most of the accidents are runoff roadway type. Further, these accidents are mainly caused due to either the absence or the failure of the crash barriers along the valley side of the highway. On the basis of field records, kinetic energy absorbed by the crash barriers and their deflections was investigated by application of computer based analysis tool ABAQUS V6.10. It has given satisfactory results on the deflection of W-beam and plum concrete barriers due to the impact of vehicle moving in various range of speed.

ANALYSIS OF LANDSLIDE REACTIVATION USING SATELLITE DATA: A CASE STUDY OF KOTRUPI LANDSLIDE, MANDI, HIMACHAL PRADESH, INDIA

Landslide is a global natural hazard that occurs frequently in the areas of incompetent weak rocks, undulating topography, steep slopes and incessant rainfall. In the night of 12 August 2017, a massive landslide took place at Kotrupi, Mandi district, Himachal Pradesh, India. The slide was so huge that it eroded more than 300-meter stretch of NH-154 killing over 50 people with more than 40 missing. Local residents report that this area has always been unstable where small landslides had occurred in the past. The landslide scar could be seen on the past satellite images from December 2001 to March 2017 on Google Earth. A huge landslide occurred at this location on 13 August 1977. After two decades on 13 August 1997, the landslide reactivated and some part of the slope failed, which can be seen on satellite images of the year 2001. The landslide reactivated again on 13 August 2007, but not much attention was given to it, as it was a small event and did not affect much. Again, after a decade, in the night of 12 August 2017 this landslide was reactivated. There is the possibility of reoccurrence of slope instability from upper reaches of the crown area of the main slide complex as well as the debris, which have been already accumulated on hill and valley side. Based on the geological, geotechnical and geophysical investigations the site stability can be done but its monitoring from satellite provides the information for its future preventive measures.

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) < 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.

Geomorphological Parameters as Correlates of Channel Erosion in River Ajilosun in Ado-Ekiti, Ekiti, Nigeria

The paper examined the relationship between geomorphological parameters and channel erosion in River Ajilosun in Ado-Ekiti, Nigeria. Data on geomorphological parameters and channel erosion of the River Ajilosun were generated through direct field measurements using tape measure, ranging pole and a piece of flat board. Some of the variables were also derived through simple linear mathematical relationships. Analysis of the various data was done with both descriptive and inferential techniques. The result of the analysis showed that channel erosion exhibited spatial variation across and along the longitudinal profiles of River Ajilosun and also between the concrete-channelised and the alluvial reaches of the river. The result of the analysis also revealed both positive and negative correlations between the geomorphological parameters and channel erosion in the river. The measures suggested for controlling channel erosion in River Ajilosun included effective channel and slope management, improvement of the channel capacity retention of channel bank vegetation and protection of the valley side vegetation among others.

A 0.01° Resolving TRMM PR Precipitation Climatology

In this study, rainfall data are prepared at a 0.01° scale using 16-yr spaceborne radar data over the area of 36.13°S–36.13°N as provided by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). A spatial resolution that is finer than the field of view is obtained by assuming rainfall uniformity within an instantaneous footprint centered on the PR footprint geolocation. These ultra-high-resolution data reveal local rainfall concentrations over slope areas. A new estimate of the maximum rainfall at Cherrapunji, India, was observed on the valley side, approximately 5 km east of the gauge station, and is approximately 50% higher than the value indicated by the 0.1°-scale data. A case study of Yakushima Island, Japan, indicates that several percent of the sampling error arising from the spatial mismatch may be contained in conventional 0.05°-scale datasets generated without footprint areal information. The differences attributable to the enhancement in the resolution are significant in complex terrain such as the Himalayas. The differences in rainfall averaged for the 0.1° and 0.01° scales exceed 10 mm day−1 over specific slope areas. In the case of New Guinea, the mean rainfall on a mountain ridge can be 30 times smaller than that on an adjacent slope at a distance of 0.25°; this is not well represented by other high-resolution datasets based on gauges and infrared radiometers. The substantial nonuniformity of rainfall climatology highlights the need for a better understanding of kilometer-scale geographic constraints on rainfall and retrieval approaches.

Sustainable development and reconstruction of the architectural ensemble in Kirzhach, depending on the natural processes on its territory

The architectural ensemble of the convent, which has been developing since the XV century in the city of Kirzhach in the center of the European part of Russia, is under the influence of processes in soils and water bodies on its territory. Ignorance of builders of the past centuries about processes repeatedly led to accidents of constructions. Preserved ancient buildings have deformation marks in bearing structures. They are caused by the slow horizontal movement of soils towards the valley side of the river Kirzhach, which stands from the deformed, but not destroyed by the process cathedral on tens of meters. The process of horizontal movement of soils to the river is stimulated by lateral erosion – stream bank erosion by river. In the result of geo-ecological research, on the plan of the ensemble territory were identified areas, which are to different extents exposed to dangerous for constructions natural processes. The measures on protection of existing constructions of the ensemble from dangerous natural and technology-induced processes are recommended, the design of foundations of new constructions capable to protect the top constructions of buildings from harmful influences of geological environment is submitted.

Lee Mixing and Nocturnal Structure over Gentle Topography

This study analyzes measurements from a network of sonic anemometers over gentle topography to investigate the possibility of nocturnal lee-generated turbulence. Although the valley side slopes are less than 6° and extend only about 12 m above the floor of the valley, the turbulence can be enhanced in the lee of one of the slopes. Significant lee turbulence develops downwind from an abrupt slope transition between a miniplateau and the modest valley side slope. Lee-generated turbulence is not observed on the opposite slope, where the slope magnitude gradually decreases with height. With intermediate 1-m wind speeds of roughly 2–4 m s−1, the cold pool is advected up the downwind slope. This downwind displacement of the cold pool and warming by lee-generated turbulence, when it occurs, leads to significant horizontal asymmetry of the temperature across the valley. For stronger winds, the cold pool is eliminated by mixing. For weak winds, a more traditional cold pool forms centered on the valley floor with limited or no lee-generated turbulence. While the impact of the gentle topography is modest compared to more dramatic terrain, less organized gentle topography covers a large fraction of Earth’s surface. However, with gentle topography, various relationships show substantial scatter, and the generalization of results from an individual network is probably not possible.