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通过试验,认为地电供电系统对地磁观测的影响主要是来自供电导线产生的磁场,其强与公式H=1/10.2I/r计算结果基本相符。而地下电流产生的磁场是很弱的,这对避免和减小其影响提供了新思维。 相似文献
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J. M. Roels 《地球表面变化过程与地形》1984,9(4):371-381
This paper presents a case study of runoff and sediment generation under Submediterranean rangeland conditions (Ardèche drainage basin, France). Measurements indicate that on a rough hillslope interrill runoff and sediment are not produced uniformly over the slope surface. It is observed that runoff concentrates immediately in non-permanent interrill flow paths, which under average storm conditions vary in length from 1.0 to 12.5 m. Long interrill flow paths may eventually become permanent. These permanent flow paths, called pre-rills, are introduced as a new source area, and are considered to be the initial stage in the development of rills. Along pre-rills considerable quantities of runoff and sediment are carried away. This study also shows that calculations based on interrill, pre-rill, and rill runoff will only have significance if storm and soil conditions are specified in detail. It is concluded from a correlation analysis between the runoff volume and the amount of soil loss on a storm-by-storm basis that the runoff volume alone cannot explain the amount of sediment that is generated in each source area; soil availability is an additional factor that must be taken into account. 相似文献
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Steve Wallis 《Acta Geophysica》2007,55(1):85-94
The simulation of solute transport in rivers is frequently based on numerical models of the Advection-Dispersion Equation.
The construction of reliable computational schemes, however, is not necessarily easy. The paper reviews some of the most important
issues in this regard, taking the finite volume method as the basis of the simulation, and compares the performance of several
types of scheme for a simple case of the transport of a patch of solute along a uniform river. The results illustrate some
typical (and well known) deficiencies of explicit schemes and compare the contrasting performance of implicit and semi-Lagrangian
versions of the same schemes. It is concluded that the latter have several benefits over the other types of scheme. 相似文献
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G. Toyos D. Oramas Dorta C. Oppenheimer M. T. Pareschi R. Sulpizio G. Zanchetta 《地球表面变化过程与地形》2007,32(10):1491-1502
Based on the debris flow events that occurred in May 1998 in the area of Sarno, Southern Italy, this paper presents an approach to simulate debris flow maximum run‐out. On the basis of the flow source areas and an average thickness of 1·2 m of the scarps, we estimated debris flow volumes of the order of 104 and 105 m3. Flow mobility ratios (ΔH/L) derived from the x, y, z coordinates of the lower‐most limit of the source areas (i.e. apex of the alluvial fan) and the distal limit of the flows ranged between 0·27 and 0·09. We performed regression analyses that showed a good correlation between the estimated flow volumes and mobility ratios. This paper presents a methodology for predicting maximum run‐out of future debris flow events, based on the developed empirical relationship. We implemented the equation that resulted from the calibration as a set of GIS macros written in Visual Basic for Applications (VBA) and running within ArcGIS. We carried out sensitivity analyses and observed that hazard mapping with this methodology should attempt to delineate hazard zones with a minimum horizontal resolution of 0·4 km. The developed procedure enables the rapid delineation of debris flow maximum extent within reasonable levels of uncertainty, it incorporates sensitivities and it facilitates hazard assessments via graphic user interfaces and with modest computing resources. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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