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71.
Floods at the northern foothills of the Tatra Mountains — A Polish-Swiss research project 总被引:1,自引:1,他引:0
Zbigniew W. Kundzewicz Markus Stoffel Ryszard J. Kaczka Bartłomiej Wyżga Tadeusz Niedźwiedź Iwona Pińskwar Virginia Ruiz-Villanueva Ewa Łupikasza Barbara Czajka Juan Antonio Ballesteros-Canovas Łukasz Małarzewski Adam Choryński Karolina Janecka Paweł Mikuś 《Acta Geophysica》2014,62(3):620-641
The present paper introduces the topical area of the Polish-Swiss research project FLORIST (Flood risk on the northern foothills of the Tatra Mountains), informs on its objectives, and reports on initial results. The Tatra Mountains are the area of the highest precipitation in Poland and largely contribute to flood generation. The project is focused around four competence clusters: observation-based climatology, model-based climate change projections and impact assessment, dendrogeomorphology, and impact of large wood debris on fluvial processes. The knowledge generated in the FLORIST project is likely to have impact on understanding and interpretation of flood risk on the northern foothills of the Tatra Mountains, in the past, present, and future. It can help solving important practical problems related to flood risk reduction strategies and flood preparedness. 相似文献
72.
Robert J. Bialik Mikołaj Karpiński Agnieszka Rajwa Bartłomiej Luks Paweł M. Rowiński 《Acta Geophysica》2014,62(6):1413-1434
This paper presents results of a field investigation conducted to examine the bed sediment, riverbed morphology and flow structure over dunes in natural and regulated channels. Field measurements using an acoustic Doppler current profiler (ADCP) have been carried out on two parts of lowland Wilga River in Poland. It is shown that the bedforms with a low angle of lee side develop more frequently than asymmetrical dunes with high lee-side angles, which are mostly associated with the occurrence of local scours and river meanders. Wavenumber analysis of bed elevation confirms the existence of scaling region in the longitudinal wavenumber spectrum, with “?3” scaling exponents for the natural and regulated channels as well. Moreover, the results of flow velocity field are presented in the form of a 2-D streamwise-vertical vector field, showing several similarities to previous laboratory and field investigations conducted on much deeper rivers than the Wilga. The experimental campaign and methods used to obtain the results are also presented briefly. In addition, a short database of fluvial dunes statistics is provided. 相似文献
73.
Reconstruction of eroded and deposited sediment volumes of the embanked River Waal,the Netherlands,for the period ad 1631–present 下载免费PDF全文
In the last few centuries humans have modified rivers, and rivers have responded with noticeable changes in sedimentary dynamics. The objective of this study is to assess these responses of the sedimentary dynamics. Therefore, we calculated a sediment budget for eroded and deposited sediment volumes in a ~12‐km long floodplain section of the largest semi‐natural embanked but still dynamic lower Rhine distributary, for ~50‐years time slices between ad 1631 and present. This is the period during which embanked floodplains were formed by downstream migration of meander bends between confining dykes. Our sediment budget involves a detailed reconstruction of vertical and lateral accretion rates and erosion rates of floodplain sediment. To do so, we developed a series of historical geomorphological maps, and lithogenetic cross‐sections. Based on the maps and cross‐sections, we divided the floodplain into building blocks representing channel bed and overbank sediment bodies. Chronostratigraphy within the blocks was estimated by interpretation of heavy metal profiles and from optically stimulated luminescence (OSL) dating results. Sediment budgets were hence calculated as a change of volume of each building block between time steps. The amount of lateral accretion initially increased, as a result of island and sand bar formation following embankment. From the eighteenth century onwards, there was a decrease of lateral processes in time, which is a result of straightening of the river by human activities, and a reduction of water and sediment supply due to the construction of a new upstream bifurcation. With straightening of the river, the floodplain area grew. Artificial fixation of the channel banks after ad 1872 prevented lateral activity. From then on, overbank deposition became the main process, leading to a continuous increase of floodplain elevation, and inherent decrease of flooding frequency and sediment accumulation rate. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
74.
A methodology is presented to construct supply curves and cost–supply curves for carbon plantations based on land-use scenarios from the Integrated Model to Assess the Global Environment (IMAGE 2). A sensitivity analysis for assessing which factors are most important in shaping these curves is also presented. In the IPCC SRES B2 Scenario, the carbon sequestration potential on abandoned agricultural land increases from 60 MtC/year in 2010 to 2,700 MtC/year in 2100 for prices up to 1,000 $/tC, assuming harvest when the mean annual increment decreases and assuming no environmental, economical or political barriers in the implementation-phase. Taking these barriers into consideration would reduce the potential by at least 60%. On the other hand, the potential will increase 55 to 75% if plantations on harvested timberland are considered. Taking into account land and establishment costs, the largest part of the potential up to 2025 can be supplied below 100 $/tC (In this article all dollar values are in US dollars of 1995, unless indicated otherwise.). Beyond 2050, more than 50% of the costs come to over 200 $/tC. Compared to other mitigation options, this is relative cheap. So a large part of the potential will likely be used in an overall mitigation strategy. However, since huge emission reductions are probably needed, the relative contribution of plantations will be low (around 3%). The largest source of uncertainty with respect to both potentials and costs is the growth rate of plantations compared to the natural vegetation. 相似文献
75.
Juan F. García-Quijano Gaby Deckmyn Reinhart Ceulemans Jos van Orshoven Bart Muys 《Climatic change》2008,86(3-4):397-424
There is a gap between the increased scientific understanding of carbon pools and fluxes at individual trees/stand and that
of forested landscape with complex structures (i.e. variety of species, age classes, site characteristic and management practices).
The question about how results generated from a simulated physiologically distinct individual(s)/stands grown at a particular
location (scale) can be extrapolated (scaling) across a diverse population in time and space with diverse environments, has
been troubling scientists for many years. Scale and scaling present three problems in common: (a) spatial heterogeneity, (b)
non-linearity in response and (c) disturbance regimes. Scale, in particular, presents other three problems: (d) threshold
scale for processes, (e) dominant processes with scales and (f) emerging properties of the system. Scaling presents problems
with (g) feedbacks between plants and environment and (h) plant interactions. The present study proposes a modeling framework
linking a process-based model SECRETS – to overcome some of the scale and scaling problems (a, b, c, d and g) – to a C accounting
model GORCAM – to integrate the effects of C stock in wood products and from fossil fuel substitution. The capabilities of
the modeling framework are tested against three theoretical complex forested landscapes that combine some of the five following
scenarios: existing multifunctional forest under (1) actual and (2) changing environmental conditions, and afforestation of
an agricultural area with (3) a new multifunctional forest or with (4) a short rotation coppice (poplar) or with (5) an agricultural
crop (miscanthus) for bioenergy production. Forest reserves calculations are included for completeness of the landscape C
balance and as reference. Results, on the one hand, suggest that the framework is able to simulate C sequestration and stock
in ecosystem pools, wood products and fossil fuel substitution of the scenarios under actual environmental conditions. However,
comparison of results under changing environmental conditions, against specific plant literature suggest SECRETS formulation
must be improved with recent development in photosynthesis, stomatal conductance and N balances. On the other hand, results
also suggest that under actual environmental conditions, the optimum landscape scenario to sequester C and avoid fossil emissions
to the atmosphere is composed by existing multifunctional forest, reserves and afforestation with short rotation coppice for
bioenergy production. 相似文献
76.
Distributions of boulders ejected from lunar craters 总被引:1,自引:0,他引:1
We investigate the spatial distributions of boulders ejected from 18 lunar impact craters that are hundreds of meters in diameter. To accomplish this goal, we measured the diameters of 13,955 ejected boulders and the distance of each boulder from the crater center. Using the boulder distances, we calculated ejection velocities for the boulders. We compare these data with previously published data on larger craters and use this information to determine how boulder ejection velocity scales with crater diameter. We also measured regolith depths in the areas surrounding many of the craters, for comparison with the boulder distributions. These results contribute to understanding boulder ejection velocities, to determining whether there is a relationship between the quantity of ejected boulders and lunar regolith depths, and to understanding the distributions of secondary craters in the Solar System. Understanding distributions of blocky ejecta is an important consideration for landing site selection on both the Moon and Mars. 相似文献
77.
Rita C. S. von Randow Celso von Randow Ronald W. A. Hutjes Javier Tomasella Bart Kruijt 《Theoretical and Applied Climatology》2012,109(1-2):205-220
Considering the high rates of evapotranspiration of Amazonian forests, understanding the impacts of deforestation on water loss rates is important for assessing those impacts on a regional and global scale. This paper quantifies evapotranspiration rates in two different pasture sites in Amazonia and evaluates the differences between the sites. In both places, measured evapotranspiration varies seasonally, decreasing during the dry season. The decrease is higher at the southwestern Amazonia site, while at the central Amazonia site, the decrease is less pronounced. During the dry season, average values of evapotranspiration are around 2.2?±?0.6?mm?day?1 in central Amazonia and 2.4?±?0.6?mm?day?1 in southwestern Amazonia, while during the wet season, those values are 2.1?±?0.6?mm?day?1 in central Amazonia and 3.5?±?0.8?mm?day?1 in southwestern Amazonia. On an annual basis, the pasture in southwestern Amazonia has higher evapotranspiration than in central Amazonia. We conclude that the main reason for this difference is the lower available energy in the wet season at the central Amazonian site, combined with a lower leaf area index at this site during the whole year. Still, the evapotranspiration is significantly controlled by the vegetation, which is well coupled with the local moisture conditions in the dry season. 相似文献
78.
Martin P. Cooke Bart E. van Dongen Helen M. Talbot Igor Semiletov Natalia Shakhova Laodong Guo
rjan Gustafsson 《Organic Geochemistry》2009,40(11):1151-1159
Bacteriohopanepolyols (BHPs) are a diverse group of membrane lipids produced by a wide variety of bacteria and can be used as molecular biomarkers for bacterial processes and populations in both modern and ancient environments. A group of BHPs, including adenosylhopane and structurally related compounds, have been identified as being specific to soils, enabling the transport of terrestrial organic matter (terrOM) to the marine realm to be monitored. Estuary surface sediment samples were obtained from the five Great Russian Arctic Rivers (GRARs; Ob, Yenisey, Lena, Indigirka and Kolyma) and river sediments were obtained from two North American Rivers (Yukon and Mackenzie). Analysis of the BHP signatures, using high performance liquid chromatography–tandem mass spectrometry (HPLC–MSn), indicated the presence of 15 different BHPs originating from a variety of different bacteria, as well as a significant presence of terrestrially derived OM. Total BHP abundance and the contribution of the “soil-marker” BHPs to the total BHP pool increased eastwards among the GRAR sediments. This suggests increasing terrestrial OM or increased preservation of OM as a result of shorter periods of permafrost thawing. The North American rivers showed greatly differing BHP levels between the Yukon and Mackenzie rivers, with a greater BHP input and thus a relatively higher soil OM contribution from the Yukon. The Indigirka River basin in the eastern Siberian Arctic appeared to be the epicentre in the pan-Arctic BHP distribution trend, with the highest “soil-marker” BHPs but the lowest tetrafunctionalised BHPs. Aminobacteriohopanepentol, an indicator of aerobic methane oxidation, was observed in all the sediments, with the source being either the marine environment or methane producing terrestrial environments. 相似文献
79.
Upstream control of river anastomosis by sediment overloading,upper Columbia River,British Columbia,Canada 下载免费PDF全文
Bart Makaske Eva Lavooi Tjalling de Haas Maarten G. Kleinhans Derald G. Smith 《Sedimentology》2017,64(6):1488-1510
Anastomosing rivers, systems of multiple interconnected channels that enclose floodbasins, constitute a major category of rivers for which various sedimentary facies models have been developed. While the sedimentary products of anastomosing rivers are relatively well‐known, their genesis is still debated. A rapidly growing number of ancient alluvial successions being interpreted as of anastomosing river origin, including important hydrocarbon reservoirs, urge the development of robust models for the genesis of anastomosis, to facilitate better interpretation of ancient depositional settings and controls. The upper Columbia River, British Columbia, Canada, is the most‐studied anastomosing river and has played a key role in the development of an anastomosing river facies model. Two hypotheses for the origin of upper Columbia River anastomosis include the following: (i) downstream control by aggrading cross‐valley alluvial fans; and (ii) upstream control by excessive bedload input from tributaries. Both upstream and downstream control may force aggradation and avulsions in the upper Columbia River. In order to test both hypotheses, long‐term (millennia‐scale) floodplain sedimentation rates and avulsion frequencies are calculated using 14C‐dated deeply buried organic floodplain material from cross‐valley borehole transects. The results indicate a downstream decrease in floodplain sedimentation rate and avulsion frequency along the anastomosed reach, which is consistent with dominant upstream control by sediment overloading. The data here link recent avulsion activity to increased sediment supply during the Little Ice Age (ca 1100 to 1950 ad ). This link is supported by data showing that sediment supply to the upper Columbia study reach fluctuated in response to Holocene glacial advances and retreats in the hinterland. Upstream control of anastomosis has considerable implications for the reconstruction of the setting of interpreted ancient anastomosing systems. The present research underscores that anastomosing systems typically occur in relatively proximal settings with abundant sediment supplied to low‐gradient floodplains, a situation commonly found in intermontane and foreland basins. 相似文献
80.
Laura A.Richards Dan J.Lapworth Daniel Magnone Daren C.Gooddy Lee Chambers Peter J.Williams Bart E.van Dongen David A.Polya 《地学前缘(英文版)》2019,10(5):1653-1667
Organic matter in the environment is involved in many biogeochemical processes,including the mobilization of geogenic trace elements,such as arsenic,into groundwater.In this paper we present the use of fluorescence spectroscopy to characterize the dissolved organic matter(DOM)pool in heavily arsenicaffected groundwaters in Kandal Province,Cambodia.The fluorescence DOM(fDOM)characteristics between contrasting field areas of differing dominant lithologies were compared and linked to other hydrogeochemical parameters,including arsenic and dissolved methane as well as selected sedimentary characteristics.Absorbance-corrected fluorescence indices were used to characterize depth profiles and compare field areas.Groundwater fDOM was generally dominated by terrestrial humic and fulvic-like components,with relatively small contributions from microbially-derived,tryptophan-like components.Groundwater fDOM from sand-dominated sequences typically contained lower tryptophan-like,lower fulvic-like and lower humic-like components,was less bioavailable,and had higher humification index than clay-dominated sequences.Methane concentrations were strongly correlated with fDOM bioavailability as well as with tryptophan-like components,suggesting that groundwater methane in these arsenic-prone aquifers is likely of biogenic origin.A comparison of fDOM tracers with sedimentary OM tracers is consistent with the hypothesis that external,surface-derived contributions to the aqueous DOM pool are an important control on groundwater hydrogeochemistry. 相似文献