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Deposition Areas (deposition + area)
Selected AbstractsEmpirical prediction of debris-flow mobility and deposition on fansEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2010Christian Scheidl Abstract A new method to predict the runout of debris flows is presented. A data base of documented sediment-transporting events in torrent catchments of Austria, Switzerland and northern Italy has been compiled, using common classification techniques. With this data we test an empirical approach between planimetric deposition area and event volume, and compare it with results from other studies. We introduce a new empirical relation to determine the mobility coefficient as a function of geomorphologic catchment parameters. The mobility coefficient is thought to reflect some of the flow properties during the depositional part of the debris-flow event. The empirical equations are implemented in a geographical information system (GIS) based simulation program and combined with a simple flow routing algorithm, to determine the potential runout area covered by debris-flow deposits. For a given volume and starting point of the deposits, a Monte-Carlo technique is used to produce flow paths that simulate the spreading effect of a debris flow. The runout zone is delineated by confining the simulated potential spreading area in the down slope direction with the empirically determined planimetric deposition area. The debris-flow volume is then distributed over the predicted area according to the calculated outflow probability of each cell. The simulation uses the ARC-Objects environment of ESRI© and is adapted to run with high resolution (2·5,m × 2·5,m) digital elevation models, generated for example from LiDAR data. The simulation program called TopRunDF is tested with debris-flow events of 1987 and 2005 in Switzerland. Copyright © 2009 John Wiley & Sons, Ltd. [source] Shaping Carbon Nanotubes and the Effects on Their Electrical and Mechanical Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2006S. Wang Abstract A method is developed and shown to be able to shape a carbon nanotube (CNT) into a desired morphology while maintaining its excellent electrical and mechanical properties. Single, freestanding nanotubes are bent by a scanning tunneling microscopy probe, and their morphology is fixed by electron-beam-induced deposition (inside a transmission electron microscope) of amorphous carbon on the bent area. It is shown that the mechanical strength of the bent CNT may be greatly enhanced by increasing the amount of carbon glue or the deposition area, and the electrical conduction of the nanotube shows hardly any dependence on the bending deformation or on the deposition of amorphous carbon. Our findings suggest that CNTs might be manipulated and processed as interconnections between electronic devices without much degradation in their electrical conductance, and be used in areas requiring complex morphology, such as nanometer-scale transport carriers and nanoelectromechanical systems. [source] Discussion of landslide self-organized criticality and the initiation of debris flowEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2007Chen Chien-Yuan Abstract The study contains descriptions of landslides and debris flows in a small upland catchment in Taiwan between 1986 and 2004. This catchment, the Chushui Creek, is situated near the epicentre of the 1999 M7·6 Chi-Chi earthquake. This is an area with high background erosion rate. The Chi-Chi earthquake caused a sharp increase in the rate of mass wasting in the epicentral area, and the data presented in this study illustrates the geomorphic change associated with the earthquake. The measurements of the geometry of the trunk stream of the Chushui catchment also show its change due to the impact of a strong typhoon in 1996. Two channel reaches that were affected by separate debris flows during this event were identified. Each reach has three sections: scour, transfer and deposition. Cross profiles of these sections show a systematic change from V-shaped bedrock channel in the scour areas to flat-floored channel in the transfer and deposition areas. Debris flows also occurred on other occasions in this channel, and their frequency has increased since the 1999 earthquake. In addition, this study contains precise geographic and statistical descriptions of the landslides triggered by three typhoons and an earthquake that affected the catchment since 1996. The total landslide area is measured for different time intervals, and a marked increase in landslide incidence is found after the 1999 earthquake. Frequency,area plots of the 126 landslides in the catchment indicate a power-law scaling with an exponent of about -1·5 of these quantities, as has been observed in other studies. We propose that a link exists between landslide frequency,area distributions and initialization of debris flow in the catchment. It may be classified as a self-organized criticality process with a critical frequency,area distribution for the landslide population. In this case, the landslide frequency,area distribution is useful in quantifying the severity of the trigger and the contribution of landslides to debris flow. Copyright © 2006 John Wiley & Sons, Ltd. [source] Atmospheric nitrogen deposition has caused nitrogen enrichment and eutrophication of lakes in the northern hemisphereGLOBAL CHANGE BIOLOGY, Issue 4 2006ANN-KRISTIN BERGSTRÖM Abstract We compiled chemical data and phytoplankton biomass (PB) data (chlorophyll a) from unproductive lakes in 42 different regions in Europe and North America, and compared these data to inorganic nitrogen (N) deposition over these regions. We demonstrate that increased deposition of inorganic N over large areas of Europe and North America has caused elevated concentrations of inorganic N in lakes. In addition, the unproductive lakes in high N deposition areas had clearly higher PB relative to the total phosphorus (P) concentrations illustrating that the elevated inorganic N concentrations has resulted in eutrophication and increased biomass of phytoplankton. The eutrophication caused by inorganic N deposition indicates that PB yield in a majority of lakes in the northern hemisphere is (was) limited by N in their natural state. We, therefore, suggest that P limitation largely concerns lakes where the balance between N and P has been changed because of increased anthropogenic input of N. [source] Flow Velocity Effect on Leaf Litter Breakdown in Tufa Depositing System (Plitvice Lakes, Croatia)INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 4 2009Anita Belan Abstract Considerable amount of riparian leaf litter is annually supplied to the cascade Plitvice Lakes and trapped on tufa barriers where it decays together with aquatic macrophytes. These barriers are the sites of heavy calcite precipitation that can widely differ in terms of current velocity. We conducted a leafbag experiment at sites differing in flow velocity and tufa deposition rate. Decomposition of Petasites spp. and Fagus sylvatica was higher under high current (0.80 m/s) and high tufa deposition areas than in low current (< 0.20 m/s) and low tufa deposition areas (k = 0.085 vs. 0.021 for Petasites spp. and 0.009 vs. 0.002 for Fagus sylvatica). We concluded that although tufa deposition could interfere with decomposition by obstructing physical abrasion and also restricting microbial conditioning, thin calcite crusts developed on the surface of the leaves made them more fragile and thus accelerated their decomposition. High current velocity probably magnified this effect by supporting higher tufa deposition and coarser type of tufa fabrics. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||