摘要:

AbstractLandsat TM as well as SPOT HRV provides good possibilities for mapping of bedrock outcrop areas to be presented on the Swedish topographical map on the scale of 1:50 000. The errors of the computer-based classification can be reduced by a“clean-up”of the training areas, founded on level slicing with transformed spectral data. The mapping accuracy can be further improved by combining the automatic classification with a subsequent visual interpretation.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880243

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTMuch of the development in Precambrian Fennoscandia is unknown. Geomorphology may partly fill the gap. Six complementary ways of analysis are discussed. 1. Relation landform—geology. Differences between gneiss and granite play small role in the Precambrian relief, but quartzite and some basic rocks are important for the landforms. In the Caledonides with rocks of more varying metamorphic grade the topographic differences are larger. Quartzite and some basic rocks stand for special relief.—2. Structures. Joint valleys have played a central role in Fennoscandian geomorphology, mainly as to joint formation and age. The evacuation of debris from joint zones has been less studied, and here is a wide field for future work.—3. The drainage net is supposed to be old. In separate paragraphs are described the parallelism of N Swedish rivers, the varying numbers of tributaries and supposed deflections. Water gaps and wind gaps are numerous. Most important explanations are weak rock in upstream areas, or tectonic uplift in the gap area. The former is preferred. The primary drainage net was probably developed on a flat sediment-covered surface.—4. Erosion surfaces. Regenerated surfaces are discribed and erosion surfaces in a stepwise system. There are open questions as to both types of surfaces. The way of description is important.—5. Climatic geomorphology may be of future importance. The Inselberg plains in N Sweden and N Finland are probably preserved from warmer climates. Forms of lower magnitude such as pediments are more problematic. So also V-shaped valleys that may reflect a subpolar climate of excessive valley formation.—6. Glacial erosion. The number of glaciations is higher than the classical 4 (2) ones. Cold-based glaciers may have existed. The forms are discussed in seperate paragraphs for striae, roches mountonnées, flyggbergs, partly glacially transformed valleys, through valleys, cirques. The lowest cirques are separately treated. They probably reflect older glaciations, complete or not.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880244

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractThe assessment of soil erosion hazard over large areas is an important aid to land evaluation and land use panning. A methodology using a simple factorial scoring procedure for erosion hazard was derived in Zimbabwe in the early 1970s. Recent developments in soil toss prediction models opens the way for improvements in methodologies for the production of erosion hazard maps.Basing the new procedure on African conditions, limited data availability and coverage at a sub-continental scale, the SLEMSA (Soil Loss Estimation Model for Southern Africa) framework is shown as a useful tool in designing a suitable methodology. Through the major factors in erosion—relief, rainfall, vegetation and soil—variables are derived for the measurement of their influence on erosion. The abstraction of the variables—average slope, kinetic energy of rainfall, vegetal cover and an index of erodibility—is described and it is shown how they can be combined through a set of design graphs taken from the Zimbabwe Highveld version of the SLEMSA framework. Hazard is expressed in‘Erosion Hazard Units’and not tonnes per hectare.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880245

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTThe improved erosion hazard methodology presented in Part I of this paper was applied to Lesotho. Values for variables describing the contribution of the major factors in erosion were abstracted from existing topographic, soil and rainfall maps, and from climatic data and crop yield statistics. Using the SLEMSA framework as a model for combining the influence of the variables, the information was organized on a 14×14 km grid to give an erosion hazard map of Lesotho. Practical and methodological difficulties are discussed. Slope and rainfall are the dominant factors, and they largely explain the variation in‘Erosion Hazard Units’from 64 in the southern lowlands to 3230 in the north-eastern mountains. Lesotho is confirmed as having the highest erosion hazard of any single country in southern and central Africa.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880246

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTSpatial variations in runoff under different environmental conditions represent one of the key problems in hydrological as well as sedimentological and geomorphological studies. In this study the mesoscale runoff variability has been investigated with the help of campaign field measurements, made in many basins at the same time, which have complemented the routine hydrological observational activities. A thorough analysis of the physiography of the basin was performed before the field studies. This made it possible to choose the measurement sites objectively and to select the physiographic variables of importance for runoff variation and for the mathematical modelling of runoff. For the period with rain the spatial variability of runoff was best explained by the amount of precipitation, by‘relief’variables and by the percentage of forest, while for the period without precipitation the percentage of lakes proved to be the most important variable.The variability of runoff registered during the campaign field studies indicates the range of uncertainty, due to the application of only the permanent, macroscale hydrological network. This is especially significant when runoff information is required in ungauged basins for hydrological or geomorphological investigations.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880247

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTDaily measurements of suspended sediment discharge undertaken on the Euphrates River at Haditha by the Iraqi Ministry of Irrigation during the period 1974 to 1982 provide an estimate of the mean annual suspended sediment load of 1.4×107tyear-1. This is equivalent to a specific suspended sediment yield of approximately 60tkm-2year-1.The availability of an eight year series of daily suspended sediment measurements for this gauging station has prompted the authors to evaluate the potential for using a suspended sediment rating curve to estimate the suspended sediment load of this major river. Analysis of the total data set indicates that although considerable scatter exists in the concentration/discharge relationship there is no clear tendency for the rating plot to exhibit a shifting relationship in response to changing season or a contrast in sediment transport between rising and falling stages. Annual sediment loads calculated using a variety of rating relationships show close correspondence with the measured loads, and a single straight line relationship fitted to the entire data set provides the closest agreement between estimated and measured loads.The potential for using a programme of infrequent sampling coupled with a suspended sediment rating curve to estimate the suspended sediment loads at Haditha has been evaluated by abstracting hypothetical data sets corresponding to a sampling frequency of two, three and four samples per month from the overall data-base. Simple straight line rating relationships fitted to these data provide estimates of annual suspended sediment load and the mean annual load within±20% and±5% of the measured values respectively. Although several existing studies have demonstrated that the rating curve approach is unlikely to provide accurate estimates of suspended sediment load for small-and medium-sized drainage basins, the approach may offer greater potential for larger river basins where the spatial and temporal aggregation associated with an increase in scale reduces the complexity of suspended sediment behaviour.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880248

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTStudies of the ice-contact proglacial Briksdal Lake in Norway have demonstrated that drifting icebergs congregate in a well-defined zone near the outlet. Deposition of the englacial debris from decaying icebergs is concentrated within this area forming a shallow underwater shelf and associated beach. It is suggested that this process may have characterized former proglacial lakes.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880249

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTDuring the Australian National Antarctic Research Expeditions (ANARE) Voyage 6, 1987, observations were made of heavily glaciated Heard Island. Features of moraines and their sediments were recorded at three glaciers at the northwestern part of the island. They indicated that in these glaciers basal movements has little erosive effect. Erosion with up-transport of debris occurs mainly at the transition from steeper to lower gradients. Moraines formed there may contain basal till. In other positions moraines are formed mainly of supraglacial debris from rockfalls or wind transport. The moraine sediments are mainly waterlaid or debris flows and, in places, possibly flow till.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880250

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTThe authors have made an analysis of particles brought down by snow on the Swedish west coast in January 1987. The analyses included a quantitative study of the deposition and its organic/inorganic relationship, and a qualitative one including mineralogical composition, quartz grain size distribution and pollen distribution. The quantitative part showed that during this snowfall the Göteborg region received about 2.3 g/m2or 1.5 time its normal monthly deposition of solid particles. Organic matter made up for about 60 per cent of the material. The mineralogical analysis showed that the orgin must be from an area with young and quartz-rich soils. The grain size distribution showed that the material must have been transported a short distance only. The largest quartz particles found were 0.34 mm in size. The pollen composition indicates a vegetation like that of southern Scandinavia, northern Germany or some parts of Holland or England, and it is also obvious that the material has it orgin in an agricultural landscape. The presence of alien pollen grains like those byEphedra and Helianthemumin our samples would best be explained by contamination from higher atmospheric levels.Having studied the distribution of the coloured snow, organic and inorganic content, grain size distribution, mineralogical composition and pollen, along with the meteorological trajectory pattern, we have little doubt that the material originated in Denmark.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880251

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTA research programme is presented with the aim of describing the recent slope process activity and its variation during Upper Holocene along an east-west cross profile of the Caledonian mountain range in Northern Scandinavia. The recent process activity in monitored mainly by air-photo interpretation and Cs 137 measurements. The variation of the processes during Upper Holocene is investigated by lichenometry, dendrochronology and sediment studies. Some preliminary results are given from two study areas,Åknes, situated on Andøya island is northern Norway, and Kärkevagge in northern Sweden. These results show that certain non proglacial lakes have sediments in which traces of infrequent rapid mass movements can be observed. The results also indicate that slope processes related to extreme meteorological events are more important in the western, maritime part of the mountain range.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880252

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor