印度喀拉拉邦雨影区流域系统形态分析及其水文意义(英文)

The rain shadow regions requisite a comprehensive watershed development and management plan for sustainable water resources management. The Pambar River Basin (PRB) lies on the rain shadow region of the southern Western Ghats, India, where climate showed marked intra-basin variation. A morphometric analysis was done to evaluate the drainage characteristics of PRB using topographical maps and digital elevation data. PRB was divided into eighteen 4th order basins (SB1-SB18), distributed along various climatic...     

Coastal morphometry as regulator of water exchange—a Swedish example

This is a paper from the Swedish research project ‘The coastal zone—scientific criteria for planners’. The goal has been to establish simple, general scientific methods for management of Swedish coastal waters. In this paper the focus is on a set of empirical data from 21 so-called type areas and on the exchange of surface water. The working hypothesis has been that the water retention (or residence) time is regulated by the morphometry. The theory has been verified. It has been shown that the water retention time can be determined from a formula based on only two key morphometric parameters, the exposure and the mean coastal width. It provides an 86% degree of explanation (r²=0·86) of the variation in empirically determined retention times and can be physically linked to the basic mass balance equation. The formula is valid for the bioproductive season (May–Oct.) and for small (1–100 km²) Swedish coastal areas. It cannot be directly applied to areas affected by heavy tides.     

Quantitative Size Classification of Scoria Cones: The Case of Tenerife (Canary Islands,Spain)

Monogenetic volcanoes are the most abundant volcanic structures on the Earth's surface. Thousands of them exist in different tectonic contexts (e.g., subduction zones, intraplate areas, and divergent boundaries), appearing in groups forming volcanic fields. Tenerife, the largest and highest island of the Canarian archipelago, started to form about 14 million years ago (Ma), as a result of a complex eruptive history and a varied geomorphological evolution, including shield-building stages, volcanic rifts, stratovolcanoes, and monogenetic cones. Tenerife is an active, volcanic, oceanic island, where the last eruption occurred in 1909. In this paper, we propose a methodology for calculating the size of monogenetic basaltic volcanoes based on morphometric parameters, as well as a classification of the size of the volcanoes through the study of 297 scoria cones of Tenerife. Morphometric techniques, based mainly on height (H_co), volume (V_co), and area (A_co), were used together with correlations between different morphological parameters. The result is a simple quantitative classification, easy to use for estimating the size of monogenetic volcanoes. Of the monogenetic basaltic volcanoes of Tenerife, 98.98% fit into this classification, which distinguishes between large (H_co >200; V_co >0.1; A_co >0.5), medium (H_co >100 to <200; V_co >0.01 to <0.1; A_co >0.2 to <0.5), and small (H_co <100; V_co <0.01; A_co <0.2) volcanoes. There is a strong correlation between the size of cinder cones and their age: the more recent scoria cones are smaller in size than the older ones. This relationship supports suggestions by other researchers that eruptions have decreased in magnitude and the volume of available magma has become smaller. The results obtained by calculating the size of the scoria cones of Tenerife make possible the extrapolation of this technique to other insular or continental monogenetic volcanic fields.     

Recent limnological changes in a saline lake of the Bolivian Altiplano,Lake Poopo

During the past twelve years, Lake Poopo, located on the Bolivian Altiplano, has had two main types of morphometry. Before 1985, its level was low and the depth shallow (maximum 3 m); there was no outlet and a strong salinity gradient existed from north to south. After 1985, the depth doubled, an outlet developed and the salinity became uniform throughout the lake (∼10 g L⁻¹). Before 1985, the phytoplankton was distinguished by a high number of diatom taxa and by the dominance of diatoms in the algal biomass. After 1985, while diatoms were still numerous in terms of species composition, Peridiniales or Chlorophyceae dominated the algal biomass. *** DIRECT SUPPORT *** A02GG003 00002     

Investigation of drainage basin geometry near an anomalously straight reach of the Big Black River,Mississippi, USA

Drainage basin geometry was analyzed in the lower portion of the Big Black River, Mississippi. The study was centered on a reach of the Big Black River that encompasses an anomalous straight reach (ASR) and has morphometric characteristics that differ from those of upstream and downstream reaches. The study area was divided into three reaches, defined by alluvial valley and active floodplain width, sinuosity, and slope. Tributary streams with confluences in the three study reaches were investigated for evidence of surface tilting, and channel and valley slopes and sinuosity were measured. The average stream channel and valley slopes within the middle reach are nearly double those of the upper and lower reaches. Lateral stream migration within the tributary basins was quantitatively analyzed by measuring the asymmetry factor (AF) and transverse topographic symmetry factor (T) indices. While AF results suggest minimal to no lateral migration within the tributaries, the T results show some shifting. The results are inconclusive regarding the possible effect of neotectonic activity in the study area near the ASR. The mean southward migration may indicate a preferred migration direction relative to the general dip of the coastal plain and plunge of the Mississippi Embayment.     

Geospatial analysis of controls on subglacial bedform morphometry in the New York Drumlin Field – implications for Laurentide Ice Sheet dynamics

The outline and trend of 6566 subglacial bedforms in the New York Drumlin Field have been digitized from digital elevation data. A spatial predictive model has been used to extend values of bedform elongation over an area measuring 200 km × 110 km. The resulting surface is used in conjunction with depth‐to‐bedrock data and an assumed duration of ice residence to test three proposed controls on bedform elongation. Upon comparison, the resulting display of morphometry is best explained by differences in ice velocity across the field of study. The existence of multiple zones of fast‐moving ice located along the southern margin of the Laurentide Ice Sheet is implied by the observed patterns of bedform elongation and orientation. We present two interpretations that are consistent with the observations. First, enhanced basal sliding caused by decreasing effective pressure near a calving margin is suggested as a possible mechanism by which localized fast ice flow is initiated and maintained. Second, topographically controlled ice streams likely occupied the fjord‐like troughs of the Appalachian Upland northern rim. Contrary to previous understanding of the Laurentide southern margin in New York State, the resulting palaeoglaciological reconstruction illustrates a dynamic mosaic of ice stream and/or outlet glacier activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Channel sediment variability along a river: A case study of the Siret River (Romania)

The Siret River has the largest drainage basin (42 274 km²) in Romania. It gathers all the rivers from the eastern part of the Eastern Carpathians, a fact that causes marked asymmetry of the basin. This study is principally concerned with changes in the form of the longitudinal profile and the grain size variability introduced by the Carpathian tributaries. Channel sediment analyses considered the petrography, granulometry, and morphometry of the pebbles, relating these to the river bed and floodplain geometry and to some properties of the drainage basin. The following conclusions arise. The Siret River undergoes an intense regrading of its longitudinal profile, with marked aggradation between transects 24 and 26 (see Figures 1 and 2). This reflects selective accumulation of coarse material due to the massive contribution of the Carpathian tributaries. This phenomenon has been continuous throughout the Holocene, resulting in the gravel sheet formation of the Pericarpathian piedmont.     

Morphometry of Quartz Aggregates in Granites: Fractal Images Referring to Nucleation and Growth Processes

Knowledge of mineral aggregate morphologies is of importance to analyze characteristic differences in rock-forming features. For quantifying these differences, the fractal geometry of quartz aggregate cuts digitized from polish sections of different types of granites has been studied. As an approach to measure fractal dimension (D), a power-law dependence of square of aggregate cuts on their linear size has been used. The D values thus calculated mainly increase from 1.48–1.62 for amazonite granites to 1.63–1.70 for alaskite granites and 1.75–1.81 for standard granites. To account for the data of morphometry, the model of nucleation and growth as applied to silicate melt freezing has been considered. For comparison between the nature and model textures, the fractal properties of cluster cuts in the system of overlapping spheres randomly distributed with random radii have been investigated through computer simulation. It has been demonstrated that the distributions of quartz aggregates in granites may be simulated by homogeneous or heterogeneous Poisson models, and both order of crystallization and metamorphic recrystallization should be taken for explaining textural variability. The results of the simulation have enabled the granitic texture to be discussed with respect to the random configuration of the spatial percolation cluster.     

Seasonal variation of crescentic dune morphology and morphometry,Strzelecki–Simpson Desert,Australia

The general absence of contemporary dune building in the Australian arid zone finds the occurrence of crescentic dune genesis and evolution at Gurra Gurra waterhole, a somewhat enigmatic event amongst prevalent inactive linear dunescapes. Crescentic dune construction is geographically restricted to areas of dominant unidirectional high windiness and minimal vegetation, parameters that are generally uncommon in arid Australia today. The influence of seasonal multidirectional winds can see dune form undergo continual transition between quasi‐equilibrium and disequilibrium. Such dynamic antithesis is depicted in seasonal mathematical comparisons of the planimetric attributes, length and width. Dimensional equilibrium is a transient feature at Gurra Gurra waterhole and not characteristic of this dunescape. Copyright © 2001 John Wiley & Sons, Ltd.     

Human impact on fixed sand dunes revealed by morphometric analysis

The Nyírség is the second largest alluvial fan in Hungary covered by fixed sand dunes. The primary aim of the paper is to describe the morphology of dunes in the region and classify them based on their morphometric characteristics. The other major aim is to select those dunes which were exposed to significant anthropogenic impact, and to determine the spatial and temporal differences in the intensity of human activity. The following dune types were separated: valley‐marginal, transitional valley‐marginal, transitional parabolic, filled, partially and unfilled parabolic dunes. After defining different dune types and their parameters, certain dunes were selected based on exposure to significant anthropogenic impact. Definite connection was demonstrated between the intensity of human environmental impact and the rate of erosion on fixed sand dunes. The erosion of sand dunes was most intensive in Medieval times, most likely due to concentration of agricultural land use. Copyright © 2009 John Wiley & Sons, Ltd.