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Glacial debris flows occurring on the Tibetan Plateau consistently result in significant property damage and loss of human life. A comprehensive field investigation was conducted in Tianmo valley along the Sichuan‐Tibet Highway to reveal the dynamics of a debris flow that occurred on 11 July 2018. Furthermore, a depth‐averaged multiphase debris flow model was proposed and employed to reconstruct the characteristics of the debris flow. The model derivation, implementation, evaluation, and application were presented to demonstrate its performance. The Voellmy model was chosen because it adequately accounts for both basal frictional effects and the entrainment phenomenon. The entrainment processes, the ice melting, and the lubrication effect, were also taken into consideration. Based on the numerical results combined with field investigation data, the kinetic characteristics of the glacial debris flow were analyzed. The Tianmo valley has a small area, but the volume and erosion rate of debris flows were much larger than that of two‐phase debris flows in the same location due to ice melting. The simulation results demonstrated that the glacial debris reached a peak velocity of 20 m/s. Additionally, the volume of the debris flow increased by 50% due to the erosion over a short runout distance of approximately 4,000 m. This increase was a result of the high velocity and abundant entrainment sources on the slope. This study aims to improve understanding of the high velocity and destructive potential of debris flows in the Tianmo valley. Plain Language Summary: Debris flows frequently affect people or infrastructure due to their large volumes and high velocities. A detailed field investigation was taken in Tianmo valley, Tibet Plateau, China in this paper to reveal the dynamics of debris flow hazard chains. In addition, an optimized numerical model was proposed and used to analyze the kinetic characteristics of a glacial debris flow that occurred on 11 July 2018. The basal friction, debris erosion, and ice melting were taken into account in the numerical simulation. Based on the numerical results combined with field investigation data, the kinetic characteristics of the glacial debris flow were obtained. Simulated results indicated that the movement process of a glacial debris flow moved approximately 4,000 m, reaching a maximum velocity of 20 m/s and 50% more materials through erosion along its path. It is expected that this study can help to better understand the significant destructive force in the Tianmo valley and establish evacuation and rescue plans for communities in Tibet Plateau. Key Points: The kinetic characteristics of a glacial debris flow in Tibet were investigatedAn optimized depth‐averaged multiphase debris flow model was derived, implemented, and evaluatedThe Tianmo debris flow exhibited high velocity, large volume, and high erosion rates due to ice melting and sufficient entrainment sources [ABSTRACT FROM AUTHOR]

An evaluation of the measurement uncertainty of on-road NOx emissions using portable emission measurement system (PEMS) based on real local testing data collected in China was carried out as per the type B method defined in the EN 17507 standard. The aim of this work was to quantify the "absolute" measurement uncertainty of PEMSs, which excluded "PEMS relative to laboratory constant volume sampler (CVS)" uncertainty from the calculation of on-road NOx measurement uncertainty using PEMSs. PEMS instruments from three mainstream manufacturers were employed. The zero drift of the NOx analyzers was evaluated periodically during the real driving emissions (RDE) test, and it was noticed that there was neither a linear nor step model of zero drift, with no correlation with the boundary conditions or measurement principle. Additionally, from the 256 valid RDE tests, the zero drift always ranged from 3.8 ppm to −3.8 ppm, and more than 95% of the span drifts were within a range of 1.5%. Based on the laboratory testing of ten vehicles using the worldwide harmonized light-duty vehicle test cycle (WLTC), the type B uncertainty of PEMS NOx measurements corresponding to China-6a and China-6b limits was assessed. An uncertainty of 26.5% for China-6a was found (NOx limit = 60 mg/km over the WLTC), which is very close to the 22.5% from the EU evaluation results (NOx limit = 80 mg/km over the WLTC); the uncertainty with respect to China-6b was found to be 42.8% because the type-I limit was tuned down to 35 mg/km. This result indicates that, with the ever-tightening regulatory limits of vehicle NOx emissions, big challenges will be posed in terms of the reliability of PEMS measurements, which requires PEMS manufacturers to improve the performance of the instruments and policymakers to refine the test procedures and/or result calculation method to minimize the impacts. [ABSTRACT FROM AUTHOR]

The fluvial geomorphology in tectonically active (particularly rapid uplift) regions often undergoes continuous change. The rapid uplift is coincident with high erosion rates; consequently, incised valleys are formed. Mass flows (for example, avalanches, landslides, and debris flows) in incised valleys can markedly influence fluvial processes and even reshape valley geomorphology. However, these processes and long-term evolution corresponding to mass flows require further clarification. Field campaigns were carried out in the region near the Yigong Tsangpo and Palong Tsangpo Rivers (hereafter the Yigong and Palong Rivers), the two largest tributaries of the lower Yarlung Tsangpo River, to examine the feedback between fluvial processes and mass flows. Remote sensing images from recent decades were used to compare the channel morphology before and after typical mass flows (particularly catastrophic ones). The morphology of the lower Yigong River has evidently been impacted by landslides, while that of the Palong River has mainly been shaped by glacial processes and debris flows. At present, the morphology of the latter consists of alternating sections of gorges and wide valleys, with a staircase-like longitudinal profile. The gorge sections exhibit single and deeply incised channels with a high-gradient channel bed and terraces. In contrast, the wide valley sections consist of lakes, braided or anabranching channels, gentle bed gradients, and thick alluvial deposits. Debris flows occur more frequently in gullies in the reaches of the gorge sections and rarely in gullies along the wide valley sections. The occurrence of mass flow events has resulted in an imbalance of the previous (quasi-)equilibrium in the river morphology; however, this has triggered negative feedback that is driving the transient river morphology to a new state of (quasi-)equilibrium. • Feedback between fluvial processes and mass flows in rapid-uplifting southeast Tibet is studied. • Field campaigns and satellite images of typical reaches were combined in the study. • Lotus root-like planform and staircase-like longitudinal profile form due to mass flows. • Negative feedback exists pushing unstable river morphology to a new (quasi-)equilibrium state. • 'Stairs (dams)' more likely form spatially from upstream to downstream by mass flows. [ABSTRACT FROM AUTHOR]

The penetration of diesel particulate filters (DPFs) in the market is growing fast. However, in the current inspection/maintenance (I/M) regulation for these vehicles, particulate emissions were capped with smoke opacity, which is incompetent to identify the excessive particle number (PN) induced by non-major DPF failures such as small cracks in substrate. This research aimed at developing a fast identification method for such malfunctioning vehicles using a low-cost condensation particle counter (CPC). To verify the effectiveness of idle PN test, 33 China-5 and China-6 heavy-duty vehicles fueled with diesel and natural gas (NG) were tested using the regulatory portable emission measurement system (PEMS) as per China-6 protocol and idle PN tests using a low-cost CPC-based system. PN emissions from China-6 vehicles with malfunctioning DPFs were at a similar level to those from China-5 vehicles (without DPF), which were significantly higher than the proper counterparts. Idle PN tests using a CPC-based system managed to identify the vehicles with DPF failures. Volumetric PN concentrations of these vehicles were much higher than those of the proper ones. This study proved that an easy, fast, and low-cost procedure could be used to screen out those high emitters with DPF failure. [ABSTRACT FROM AUTHOR]

Debris flows occurred very often in Guxiang gully, one tributary of Palongcangbu since 1950s. Debris flows were investigated and the volume of debris flows have been caculated since 1953. This paper collected 60-years data of accumulation rates of loose sediment in the upstream of the narrow sections of the gully with relationships of debris flows magnitude. Sediments changes in the upstream of the narrow gully section are compared with channel incision, debris flow activity and motions. The data of the sediment accumulations and its debris flow events provide insights into narrow gully section controls and debris flow dynamics. Acceleration in debris flow events was recorded between the 1950s and 1980s, compared with a decrease in debris flow events since the 2000s. The narrow gully section has always formed as a dam for sediment accumulation. The loose material accumulations rates have remained quite small and sediment is not enough to support the frequent debris flows since 2000. On the contrary, sediments accumulated in the upstream of the narrow section due to large earthquake in 1950 were the sources of debris flows. There was not a clear coupling between accumulation rates of sediment and the frequency-magnitude debris flows in the 1950s and 1980s. On the contrary, a clear link between accumulation rates of sediment and the frequency-magnitude debris flows exists since 2000. In the debris flow events since 2000, debris flows in the gully are both controlled by the rainfall and narrow section of the gully. In this paper we have considered the dynamics of many debris flow events in the upstream and downstream of the narrow gully section. The sediments accumulation in the upstream of the narrow section of the gully created as a dam, which was depending on the accumulated sediment volume and the width of the narrow section. The accumulation of sediment in the upstream of the narrow section could affect its longitudinal morphology and add the longitudinal gradient, which caused a perturbation of debris flow dynamic in the gully.Key Word: debris flow; narrow section; consolidation; intermittent motion; additional gradient [ABSTRACT FROM AUTHOR]

The Dadu River Basin (DRB) is an important economic corridor on the Chuanxi Plateau. The DRB is located in the highly changeable terrain of the eastern Qinghai-Tibet Plateau and is often threatened by debris flows. To mitigate the damage of debris flow disasters to the construction and operation of large infrastructures such as railways, roads and hydropower stations in the DRB, it is necessary to evaluate debris flow susceptibility. The connectivity of potential material sources (CPMS), which proxies the possibility of potential material transfer from the source to the outlet, was calculated using an improved index of connectivity, excess topography and brittle fracture index to identify and quantify debris flow susceptibility. The results show that the IC and the gully scale have a Logartihmic function in the DRB, in which IC decreases as the catchment area increases. In 3967 gullies of the Dadu River and its tributaries, the total connectivity of potential material sources (TCPMS) could be used to distinguish between debris flow gullies and non-debris flow gullies (AUC = 0.748). The TCPMS and average connectivity of potential material sources (ACPMS) were used to classify the scale and activity intensity of the 2398 debris flow gullies into four levels. The moderate- and high-activity intensity and large- and extra large-scale debris flows are mainly distributed in Danba, Luding and Kangding. The results of this study provide reference and evidence for the identification and evaluation of debris flow susceptibility. • A new method for assessing debris flow susceptibility based on potential material sources and sediment connectivity. • The quantitative relationship between the scale of debris flow and conditioning factors. • The contribution of excess topography was considered. [ABSTRACT FROM AUTHOR]