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71.
Meandering river sinuosity increases until the channel erodes into itself (neck cutoff) or forms a new channel over the floodplain (chute cutoff) and sinuosity is reduced. Unlike neck cutoff, which can be measured or modelled without considering overbank processes, chute cutoff must be at least partially controlled by channel-forming processes on the floodplain. Even though chute cutoff controls meandering river form, the processes that cause chute cutoff are not well understood. This study analyses the morphology of two incipient chute cutoffs along the East Fork White River, Indiana, USA, using high temporal and spatial resolution UAS-based LiDAR and aerial photography. LiDAR and aerial imagery obtained between 1998 and 2019 reveals that large scour holes formed in the centre of both chutes sometime after chute channel initiation. A larger analysis within the study watershed reveals that scour holes within incipient chutes can be stable or unstable, and tend to stabilize when the chute is colonized by native vegetation and forest. When the scour holes form in farmed floodplain, they enlarge rapidly after initial formation and contribute to complete chute cutoff. In addition, this study shows that the formation of scour holes can occur in response to common, relatively low-magnitude floods and that the amount of incipient chute erosion does not depend on peak flood magnitude. The role of scour holes in enlarging chute channels could be an important mechanism for chute channel evolution in meandering rivers. This study also confirms that understanding the relationships among flow, land cover, and cutoff morphology is substantially improved with on-demand remote sensing techniques like integrated UAS and LiDAR. © 2020 John Wiley & Sons, Ltd. 相似文献
72.
ABSTRACTCharacterizing, understanding and better estimating uncertainties are key concerns for drawing robust conclusions when analyzing changing socio-hydrological systems. Here we suggest developing a perceptual model of uncertainty that is complementary to the perceptual model of the socio-hydrological system and we provide an example application to flood risk change analysis. Such a perceptual model aims to make all relevant uncertainty sources – and different perceptions thereof – explicit in a structured way. It is a first step to assessing uncertainty in system outcomes that can help to prioritize research efforts and to structure dialogue and communication about uncertainty in interdisciplinary work. 相似文献
73.
Daniel Lane Colin P.R. McCarter Murray Richardson Chris McConnell Tim Field Huaxia Yao George Arhonditsis Carl P.J. Mitchell 《水文研究》2020,34(3):598-614
The estimation of hydrologic transit times in a catchment provides insights into the integrated effects of water storage, mixing dynamics, and runoff generation processes. There has been limited effort to estimate transit times in southern boreal Precambrian Shield landscapes, which are characteristically heterogeneous with surface cover including till, thin soils, bedrock outcrops, and depressional wetland features that play contrasting hydrologic roles. This study presents approximately 3.5 years of precipitation and streamflow water isotope data and estimates mean transit times (MTTs) and the young water fraction (py) across six small catchments in the Muskoka-Haliburton region of south-central Ontario. The main objectives were to define a typical range of MTTs for headwater catchments in this region and to identify landscape variables that best explain differences in MTTs/py using airborne light detection and ranging and digital terrain analysis. Of the transit time distributions, the two parallel linear reservoir and gamma distributions best describe the hydrology of these catchments, particularly because of their ability to capture more extreme changes related to events such as snowmelt. The estimated MTTs, regardless of the modelling approach or distribution used, are positively associated with the percent wetland area and negatively with mean slope in the catchments. In this landscape, low-gradient features such as wetlands increase catchment scale water storage when antecedent conditions are dryer and decrease transit times when there is a moisture surplus, which plausibly explains the increases in MTTs and mean annual runoff from catchments with significant coverage of these landscape features. 相似文献
74.
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
75.
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
76.
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
77.
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
78.
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
79.
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
80.
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