Debris-flow-dominated sediment transport through a channel network after wildfire     

Petter Nyman  Walter A.C. Box  Justin C. Stout  Gary J. Sheridan  Saskia D. Keesstra  Patrick N.J. Lane  Christoph Langhans 《地球表面变化过程与地形》2020,45(5):1155-1167

Field studies that investigate sediment transport between debris-flow-producing headwaters and rivers are uncommon, particularly in forested settings, where debris flows are infrequent and opportunities for collecting data are limited. This study quantifies the volume and composition of sediment deposited in the arterial channel network of a 14-km² catchment (Washington Creek) that connects small, burned and debris-flow-producing headwaters (<1 km²) with the Ovens River in SE Australia. We construct a sediment budget by combining new data on deposition with a sediment delivery model for post-fire debris flows. Data on deposits were plotted alongside the slope–area curve to examine links between processes, catchment morphometry and geomorphic process domains. The results show that large deposits are concentrated in the proximity of three major channel junctions, which correspond to breaks in channel slope. Hyperconcentrated flows are more prominent towards the catchment outlet, where the slope–area curve indicates a transition from debris flow to fluvial domains. This shift corresponds to a change in efficiency of the flow, determined from the ratio of median grain size to channel slope. Our sediment budget suggests a total sediment efflux from Washington Creek catchment of 61 × 10³ m³. There are similar contributions from hillslopes (43 ± 14 × 10³ m³), first to third stream order channel (35 ± 12 × 10³ m³) and the arterial fourth to fifth stream order channel (31 ± 17 × 10³ m³) to the total volume of erosion. Deposition (39 ± 17 × 10³ m³) within the arterial channel was higher than erosion (31 ± 17 × 10³ m³), which means a net sediment gain of about 8 × 10³ m³ in the arterial channel. The ratio of total deposition to total erosion was 0.44. For fines <63 μm, this ratio was much smaller (0.11), which means that fines are preferentially exported. This has important implications for suspended sediment and water quality in downstream rivers. © 2019 John Wiley & Sons, Ltd.  相似文献   

Intercomparison of measurements of bulk snow density and water equivalent of snow cover with snow core samplers: Instrumental bias and variability induced by observers     

J. Ignacio López-Moreno  Leena Leppänen  Bartłomiej Luks  Ladislav Holko  Ghislain Picard  Alba Sanmiguel-Vallelado  Esteban Alonso-González  David C. Finger  Ali N. Arslan  Katalin Gillemot  Aynur Sensoy  Arda Sorman  M. Cansaran Ertaş  Steven R. Fassnacht  Charles Fierz  Christoph Marty 《水文研究》2020,34(14):3120-3133

Manually collected snow data are often considered as ground truth for many applications such as climatological or hydrological studies. However, there are many sources of uncertainty that are not quantified in detail. For the determination of water equivalent of snow cover (SWE), different snow core samplers and scales are used, but they are all based on the same measurement principle. We conducted two field campaigns with 9 samplers commonly used in observational measurements and research in Europe and northern America to better quantify uncertainties when measuring depth, density and SWE with core samplers. During the first campaign, as a first approach to distinguish snow variability measured at the plot and at the point scale, repeated measurements were taken along two 20 m long snow pits. The results revealed a much higher variability of SWE at the plot scale (resulting from both natural variability and instrumental bias) compared to repeated measurements at the same spot (resulting mostly from error induced by observers or very small scale variability of snow depth). The exceptionally homogeneous snowpack found in the second campaign permitted to almost neglect the natural variability of the snowpack properties and focus on the separation between instrumental bias and error induced by observers. Reported uncertainties refer to a shallow, homogeneous tundra-taiga snowpack less than 1 m deep (loose, mostly recrystallised snow and no wind impact). Under such measurement conditions, the uncertainty in bulk snow density estimation is about 5% for an individual instrument and is close to 10% among different instruments. Results confirmed that instrumental bias exceeded both the natural variability and the error induced by observers, even in the case when observers were not familiar with a given snow core sampler.  相似文献   

Jeans Instability of a Protoplanetary Circular Disk Taking into Account the Magnetic Field and Radiation in Nonextensive Tsallis Kinetics     

Kolesnichenko  A. V. 《Solar System Research》2021,55(2):132-149

Solar System Research - Within the framework of Tsallis nonextensive statistics, the criteria for the Jeans gravitational instability are derived for a self-gravitating protoplanetary disk, whose...  相似文献   

Characteristics of the Energy Transfer by Alfvén Waves in the Solar Atmosphere     

Tsap  Yu. T.  Stepanov  A. V.  Kopylova  Yu. G.  Khaneichuk  O. V. 《Geomagnetism and Aeronomy》2020,60(4):446-451

Geomagnetism and Aeronomy - The propagation of linear Alfvén waves with periods of 10–200 s from the photosphere to the solar chromosphere under the conditions of an isothermal...  相似文献   

Influence of Oxygen Ions on the Structure of the Thin Current Sheet in the Earth’s Magnetotail     

Domrin  V. I.  Malova  Kh. V.  Popov  V. Yu.  Grigorenko  E. E.  Petrukovich  A. A. 《Geomagnetism and Aeronomy》2020,60(2):171-183

Geomagnetism and Aeronomy - During geomagnetic substorms, the current sheet in the Earth’s magnetotail can transversely reduce in thickness from a few radii of the Earth (RE) to one to...  相似文献   

11-Year Index of Linear Configurations of Venus,Earth, and Jupiter and Solar Activity     

Okhlopkov  V. P. 《Geomagnetism and Aeronomy》2020,60(3):381-390

Geomagnetism and Aeronomy - This study uses the evolution of a parameter introduced by the author that characterizes the relative position of planets: the daily average difference of the...  相似文献   

Estimation of the Ionospheric Effects of Geomagnetic Disturbances Based on Data from Wakkanai Station     

Legen’ka  A. D.  Khegai  V. V. 《Geomagnetism and Aeronomy》2020,60(5):577-585

Geomagnetism and Aeronomy - Ionosonde measurements of the critical frequency of the ionospheric F2 layer (foF2) at Wakkanai station (Japan) are analyzed with the method of superposed epochs. The...  相似文献   

Climate Oscillations in Southern Bulgaria and Solar Activity: Analysis of Annual Rings of Needle Samples     

Komitov  B.  Kaftan  V. 《Geomagnetism and Aeronomy》2020,60(8):1180-1186

Geomagnetism and Aeronomy - Abstract—The main subject of the study is an analysis of time series of the width of annual rings of spruce and pine (D) that were obtained during the...  相似文献   

Detection of Cyanobacterial Toxins in Water Supply Sources and Tap Water in Some Russian Cities: Searching Producers and Testing Removal Methods     

Sidelev  S. I.  Babanazarova  O. V. 《Water Resources》2020,47(2):304-314

Water Resources - For the first time, data are given on cyanobacterial toxins entering tap water, supplied to the population of some cities in Yaroslavl oblast. The detection of microcystins with...  相似文献   

Groundwater Hydrochemistry of Suprapermafrost–Intrapermafrost Flow in Their Discharge Areas in Central Yakutia     

Pavlova  N. A.  Shepelev  V. V.  Galanin  A. A.  Efremov  V. S. 《Water Resources》2020,47(4):581-590

Water Resources - The results of long-term studies of a group of aufeis-forming Buluus groundwater sources are given. A stow, which has been formed by the spring, contains the drainage area of the...  相似文献