摘要:

ABSTRACTSnow avalanche impact landforms have been found at many localities in Troms, North Norway. Three morphological varieties occur: a) avalanche impacttongues—tongue-shaped debris accumulations on the distal banks of streams, b) avalanche impactpits—water-filled depressions having a distal tongue-shaped accumulation, c) avalanche impactpools—submerged depressions occurring in larger water bodies and bounded distally by a debris ridge. The features have formed by the cumulative effect of repeated snow avalanche impact whereby debris is ejected from the impact area and deposited distally.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11879994

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTMeasurements of the physical properties of strongly weathered soils from greywacke, in the South Auckland region of New Zealand, indicate that the dominant clay mineral is kaolinite, that the hydraulic conductivities of subsoils are greater than those of surface horizons and that the soils are cohesive. Strength changes from natural moisture content to saturation are 22 percent with c' 17 to 14 kPa andø' 44°to 36°for the clay material immediately above the failure planes of translational landslides, and 38 percent for the silty clay below the failure plane.Infinite slope analysis supports the conclusion, drawn from field observations, that intense summer rainstorms trigger landslides by causing high hydrostatic pressures in tension cracks. The high pore water pressures are then transmitted through the permeable subsoil. The only effective soil conservation measure is reafforestattion which adds to the apparent cohesion of the soils.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11879995

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTPublished records of the rainfall intensities and durations associated with shallow landsliding and debris flow activity suggests a limiting threshold for this type of slope instability. The limit has the general form:I = 14.82 D-0.39and is best defined for rainfall durations between 10 minutes and 10 days.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11879996

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTFollowing from an earlier paper on the altitudinal gradients of temperature in the British Isles (Harding, 1978) a statistical study is made of the more extensive network of upland observations from southern Norway. The effects of altitude are found to be similar in the two regions: the mean values of the altitudinal gradients are the same and characteristic maximum in the spring is observable and is found to be more pronounced in the eastern half of the country. The larger number of high level stations in Norway allows a more complete description of the variability about the mean gradient, which shows a very significant seasonal variation.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11879997

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTIn the Canadian High Arctic, the bulk of annual streamflow occurs during the period when valleys are choked with snow. A study was carried out near Resolute, Northwest Territories, to examine the manner in which meltwater runoff carves channels in the valley snowpacks. Major factors controlling channel development include snow distribution and snow characteristics which in turn are related to local topography and the prevailing direction of winter snow drift. Channel development begins with a saturation of the valley snowpack, followed by water movement within or on the surface of the snow. Several processes then take place including the ponding and subsequent release of water behind snow-dams formed by drifts, the formation and collapse of snow tunnels, the vertical incision and lateral shifting of channels in the snowpack, the abandonment of channels due to flow diversion, and a disintegration and decay of the snow in the valleys. Based on the close relationship between topography, snow accumulation patterns and the recurrence of channel development processes, a qualitative model was formulated to predict the sequence of channel development events.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11879998

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTThis paper re-examines the geomorphological role of meltwater derived from snow patches in the light of observations made during the break up of snow cover on Byers Peninsula in 1976. The object is to draw attention to the erosive capacity of snow melt and the fact that channels created by this action can show similar morphological characteristics to those commonly ascribed to a fluvioglacial origin. These include the crossing of local topographic divides and commencement in the middle of slopes.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11879999

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTFluvial transportation has been studied at six sites along the River Västerdalälven in middle Sweden during 1977 and 1978. The total transportation was calculated to be 62,360 at the most upstream station and 193,660 metric tonnes at the most downstream station. 81–87 % of the total transported amounts are dissolved solids. Bed-load transportation constitutes only 1–2 % of the total. Differences in transportation along the river are found to be due to changes in fall profile and sediment composition. No effects of relative relief or land use practices can be detected.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11880000

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTRelations and interdependence between factors determining the processes of eolian transportation and deposition and results of these processes were studied in the area of theŁeba barrier on the Polish Baltic coast where modern eolian processes are intensive.From quantitative studies of transport intensity it was found that: (1) Transport intensity is approximately proportional to the 4.68 power of wind velocity measured 1 m above the ground, and calculated indices of wind effectiveness showed that storm winds even of short duration are the most significant for creation of the eolian relief. (2) Transport intensity is inversely proportional to air temperature which explains, among other things, the particularly high efficiency of eolian processes in winter and fall periods. (3) Ground moisture does not hinder eolian transportation, especially not at high wind velocities. (4) Increase in transport intensity is inversely proportional to a height element of the surface roughness. Even microforms, e.g. ripple marks, cause a distinct decrease in transportation.Distinct dependencies were found between the character of the surface face and the sand stream structure since it turned out that: (1) The thickness of the sand stream is not only a function of wind velocity, but also depends on surface moisture and roughness. Over a moist and smooth surface the thickness of the sand stream is considerably larger than over a dry rippled surface. (2) The sand stream is denser over the latter rippled bed.The transport studies and observations of microforms and mesoforms made it possible to dinstiguish a group of factors influencing morphology, structure and texture of depositional forms: (I) In the case of a dune field it is not wind velocity but surface roughness and ground moisture that have a decisive influence on dune morphology. In humid periods, mainly deflation relief is formed, while in dry ones, a whole set of depositional micro and meso forms develops. (2) The size of the smallest depositional forms (ripple marks) in proportional to the average grain size and inversely proportional to the degree of sorting in these forms. (3) Differentiation in graining in the distal slope of a dune depends more on the character of the proximal slope and sand moisture than on wind velocity. (4) Depositional intensity and humidity of the deposited sand have a direct in influence on gravitational motion in the distal slope, and an indirect influence on graining and development of disturbance structures.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11880001

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTShore displacement at Stockholm has been studied by indications of former water levels from e.g. tide-pole records, old oak-trees,14C-datings of sediments in lakes isolated from the Baltic and archaeological material. Through the excavations at Helgeandsholmen, more material has appeared to give information about the process on the Baltic (“Saltsjö”-) side of the town. It has been found that shore-displacement at Stockholm is not so regular as was previously thought. Eustatic factors strongly modify the isostatic uplift that might be considered more or less linear over the last millenium. Since the isolation of Lake Mälar that probably occurred in the 12th-13th centuries the lake has cut down its outlet (mainly at Norrström) at about the same rate that shore displacement has taken place on the Baltic side. However, this process has stopped during the last 3–4 decades, due to regulation of the water level through damming.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11880002

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

ABSTRACTThe micromorphology of a chronosequence of lowland soils developed on till exposed by the retreating Breidamerkur glacier is compared with that of a palaeosol buried by the advancing glacier about 1700 A. D. and with three soils from the mountainous hinterland.As first exposed the wet highly dispersed till has a dense matrix with a few spherical bubble pores near the surface and an incipient platy structure below the surface layer. In the early years after deglaciation, on freely drained sites, the surface layers develop a porous spongy fabric and silt is gradually washed down into the lower part of the solum to form a dense silty layer. Within thirty years a weakly developed silt droplet fabric is present in the surface layer and reaches a depth of more than 50 cm in the oldest soil of the sequence on the 1894 moraine. A similar weakly developed silt droplet fabric is present in the Fjall palaeosol and in two of the three mountain soils.The weak patchy silt droplet fabric currently developing in these immature Icelandic soils is very similar to the fabric which developed in upland soils at the southern margin of the zone of discontinuous permafrost in the British Isles at the beginning of the present cycle of soil profile development in the Pre-Boreal Period.

ISSN:0435-3676    

DOI:10.1080/04353676.1980.11880003

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor