Journal of Mountain Science

Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding processes under different slope gradients at a rate of 10°, 15°, 20° and 25° with rainfall intensity of 1.5 mm min−1 in a laboratory setting. Results revealed that mean rill depth and rill density has a positive interrelation to the slope gradient. To the contrary, width-depth ratio and distance of the longest rill to the top of the slope negatively related to slope gradient. All these suggested that increasing slope steepness could enhance rill headward erosion, vertical erosion and the fragmentation of the slope surface. Furthermore, total erosion tended to approach a stable maximum value with increasing slope, which implied that there is probably a threshold slope gradient where soil erosion begins to weaken. At the same time, the correlation analysis showed that there was a close connection between slope gradient and the various indices of soil erosion: the correlation coefficients of slope gradient with maximal rill depth, number of rills and the distance of the longest rill from the top of the slope were 0.98, 0.97 and −0.98, respectively, indicating that slope gradient is the major factor of affecting the development of rills. Furthermore, runoff was not sensitive to slope gradient and rill formation in this study. Sediment concentration, however, is positively related to slope gradient and rill formation, the sediment concentrations increased rapidly after rill initiation, especially. These results may be essential for soil loss prediction.

Kathmandu Kyirong Highway (KKH) is one of the most strategic Sino-Nepal highways. Low-cost mitigation measures are common in Nepalese highways, however, they are not even applied sufficiently to control slope instability since the major part of this highway falls still under the category of feeder road, and thus less resources are made available for its maintenance. It is subjected to frequent landslide events in an annual basis, especially during monsoon season. The Gorkha earthquake, 2015 further mobilized substantial hillslope materials and damaged the road in several locations. The aim of this research is to access the dynamic landslide susceptibility considering pre, co and post seismic mass failures. We mapped 5,349 multi-temporal landslides of 15 years (2004–2018), using high resolution satellite images and field data, and grouped them in aforementioned three time periods. Landslide susceptibility was assessed with the application of ‘certainty factor’ (CF). Seventy percent landslides were used for susceptibility modelling and 30% for validation. The obtained results were evaluated by plotting ‘receiver operative characteristic’ (ROC) curves. The CF performed well with the ‘area under curve’ (AUC) 0.820, 0.875 and 0.817 for the success rates, and 0.809, 0.890 and 0.760 for the prediction rates for respective pre, co and post seismic landslide susceptibility. The accuracy for seismic landslide susceptibility was better than pre and post-quake ones. It might be because of the differences on completeness of the landslide inventory, which might have been possibly done better for the single event based co-seismic landslide mapping in comparison with multitemporal inventories in pre and post-quake situations. The results obtained in this study provide insights on dynamic spatial probability of landslide occurrences in the changing condition of triggering agents. This work can be a good contribution to the methodologies for the evaluation of the dynamic landslide hazard and risk, which will further help to design the efficient mitigation measures along the mountain highways.

This research describes a quantitative, rapid, and low-cost methodology for debris flow susceptibility evaluation at the basin scale using open-access data and geodatabases. The proposed approach can aid decision makers in land management and territorial planning, by first screening for areas with a higher debris flow susceptibility. Five environmental predisposing factors, namely, bedrock lithology, fracture network, quaternary deposits, slope inclination, and hydrographic network, were selected as independent parameters and their mutual interactions were described and quantified using the Rock Engineering System (RES) methodology. For each parameter, specific indexes were proposed, aiming to provide a final synthetic and representative index of debris flow susceptibility at the basin scale. The methodology was tested in four basins located in the Upper Susa Valley (NW Italian Alps) where debris flow events are the predominant natural hazard. The proposed matrix can represent a useful standardized tool, universally applicable, since it is independent of type and characteristic of the basin.

The incidence of the airborne fungal spores was determined in the air of subalpine zone of the Karkonosze Mountains and of the Izerskie Mountains in the borderland between Poland and the Czech Republic. The experiment was conducted in 2011 and 2012 at three to four week intervals from May to October. Air samples were taken from three locations in the Karkonosze Mts. and one from the Izerskie Mts. To examine the air, the Air Ideal 3P sampler and acidified PDA medium were used. The results show that Cladosporium cladosporioides was the most abundant spore type in all the sampling locations (up to 30%), followed by Alternaria alternata (16%–20%), Fusarium (up to 10%) and Sclerotinia sclerotiorium (up to 6%). The lower spore counts were recorded in May samples, compared to the other months. In this case the snow cover, that was still present in the area at the beginning of May, may be the reason for the lower, compared to June, July and August samplings, CFU (Colony Forming Unit) counts in that month. The influx of air masses from SE, S and SW sectors in the area under study may affect dissemination of the plant-pathogenic fungi from the Czech Republic and from the South of Europe in general.

The objective of this study was to assess runoff discharge and sediment yield from Da River Basin in the Northwest of Vietnam using Soil and Water Assessment Tools (SWAT) model. The SWAT model was calibrated and validated using the observed monthly stream flows and sediment yield at selected gauging stations. The results indicated that SWAT generally performs well in simulating runoff and sediment yield according to Nash-Sutcliffe efficiency (NSE), Observation’s standard deviation ratio (RSR), and percent bias (PBIAS) values. For runoff, the values of NSE, RSR, and PBIAS were 0.98, 0.02, and 3.69 during calibration period and 0.99, 0.01, and 1.56 during validation period, respectively. For sediment yield, the efficiency was lower than the value of NSE, RSR, and PBIAS during calibration period were 0.81, 0.19, and −4.14 and 0.84, 0.16, and −2.56 during validation period, respectively. The results of the study indicated that the vegetation status has a significant impact on runoff and sediment yield. Changes in land use type between 1995 and 2005 from forest to field crop and urban strongly contributed to increasing the average annual runoff from 182.5 to 342.7 mm and sediment yield from 101.3 to 148.1 ton−1 ha. Between 2005 and 2010, a decrease of both runoff (from 342.7 to 167.6 mm) and sediment yield (from 148.1 to 74.0 ton−1 ha) was due to the expansion of forested area and application of soil conservation practices. The results of this study are important for developing soil and water conservation programs, extending future SWAT modelling studies and disseminating these results to other regions in Vietnam.

This paper presents a lumped mass model to describe the run-out and velocity of a series of large flume tests, which was carried out to investigate some propagation mechanisms involved in rapid, dry, dense granular flows and energy transformation when the flows encountered obstacles and reoriented their movement directions. Comparisons between predicted and measured results show that the trend of predicted velocities was basically matched with that of measured ones. Careful scrutiny of test videos reveals that subsequent particles with a higher velocity collided with slowed fronts to make them accelerate. However, this simple model cannot reflect collisions between particles because it treated released materials as a rigid block. Thus, the predicted velocity was somewhat lower than the measured velocity in most cases. When the flow changed its direction due to the variation in slope inclination, the model predicted a decrease in velocity. The predicted decrease in velocity was less than the measured one within a reasonable range of 10% or less. For some cases in which a convexity was introduced, the model also predicted the same trend of velocities as measured in the tests. The velocity increased greatly after the materials took a ballistic trajectory from the vertex of the convexity, and reduced dramatically when they finally made contact with the base of the lower slope. The difference between prediced and measured decrease in velocity was estimated to be about 5% due to the landing. Therefore, the simple lumped mass model based on the energy approach could roughly predict the run-out and velocity of granular flows, although it neglected internal deformation, intergranular collision and friction.