摘要:

ABSTRACTThe heavy rains of 10–11 July 1972 in Longyear valley, Spitsbergen were an extreme meteorological event Slides and debris flows corresponding to an average denudation of about 1 mm occurred in a small (6.8 km2) catchment area. The debris mantle of slopes in the area investigated has a wide range of particle sizes, and drainage is normally good. Debris flows were not triggered by longlasting rains, but when rainfall intensity increased to values higher than 2 mm/hour, risk of failure was reached. Factors which encouraged debris slides and flows, in addition to the intense rainstorm, were a permafrost table, pre-existing depressions on hillsides and hillside steepness. Judging from the morphology on Longyear valleys slopes and nearby areas, the rapid and sporadic mass movements have a considerable effect upon evolution of slopes in the high arctic area.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880059

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTThe escarpment of the Lias cueasta in the southern part of Luxembourg is formed by the Lias sandstone. The lowland in front is underlain by poorly consolidated Keuper marls. In several places the equally“weak”Psilonoten marls form a secondary step between the main escarpment and the lowland. As this relief configuration cannot be accounted for by lithological differences between the underlying rock types, the hypothesis is tested here that it is due to differential erosion of the soil under“natural”conditions, i.e. deciduous woodland. It is shown that this hypothesis can be accepted when the erosion processes are viewed in their ecological context. Today, erosion by splash is one of the major processes responsible for lowering the forest floor in Luxembourg. It was found that, other conditions being equal, the efficacy of this process is determined more by the absence of a protective litter cover than by the erodibility of the soil material. Due to a much larger exposed surface area, especially during the summer months, the Keuper soils are indeed more subject to splash than the Psilonoten soils, whereas the soils of the Lias sandstone remain protected by a litter layer virtually throughout the year. Leaf consumption by earthworm, mainlyLumbricus terrestris, is the principal cause of the observed differences. The ecological conditions of the poorly drained Keuper soils are most favourable for this earthworm species.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880060

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTFew published measurements of current erosion rates exist for Italy. The results of an erosion plot study for the period 1974–1980 on Plio-Pleistocene clay hillslopes in S. Italy are presented. Mean annual erosion rates for interrill areas were high, ranging from 5.3 mm/yr to 30.6 mm/yr. The rates obtained are explained in terms of the‘dispersive’properties of the Plio-Pleistocene clay, and in terms of the interaction of rainsplash and surface flow.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880061

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTAn episode of unusually intense rainfall triggered over a thousand landslides on Santa Cruz Island, California, during the winter of 1977–78. These included large, deep-seated failures, composite mudflows, and hundreds of shallow soil slips. In this study, landslide occurrence is examined in relation to lithologic, pedologic, topographic, and vegetational conditions. Their effects on soil permeability, water movement patterns, and shear strength are found to be related to landslide morphology and process.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880062

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTThe design and underlying assumptions of published works on salt weathering simulation are reviewed. It is argued that studies have tended to demonstrate the efficacy of salt weathering under conditions which owe more to experimental procedure than conditions experienced in hot deserts. As a result patterns and rates of weathering are produced which do not necessarily correspond to those observed in nature. Recommendations are made concerning the choice of suitable temperature and humidity regimes, salts, and salt application techniques which might produce rock breakdown more consistent with field observations.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880063

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTRates of sediment transport by surface wash and throughflow were measured at a virgin lowland rain forest site in northern Negri Sembilan, Peninsular Malaysia over a twelve month period. Two throughflow pits and 11 surface wash traps were installed on two hillslopes. Rates of suspended sediment transport at the wash trap sites ranged from 0.058 cm3/cm/yr to 0.735 cm3/cm/yr, with an average of 0.294 cm3/cm/yr. At all 11 of the wash trap sites suspended sediment transport was of far greater importance than the transport of solutes: on average, suspended sediment accounted for 83.3 % of total sediment transported and solutes 5.1 %. The remaining 11.6% comprised ash elements in litter washed downslope. It is suggested that the downslope transport of litter is a neglected denudational process. At both pit sites, sediment transport by surface wash was more important than lateral eluviation, accounting for 76.7 % of the total sediment transported at one pit site and 85 % at the other. The rates of suspended sediment transport by surface wash recorded at the Pasoh Forest Reserve are comparable with rates measured on forested slopes in West Africa, the Philippines and Java, but lower than rates recorded in Thailand.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880064

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTErosion processes in relatively undisturbed tropical forest ecosystems were investigated along a transect across the Central Andean Cordillera between Pereira and Venadillo in the Departamento del Tolima Colombia. Of particular interest were relationships between the nature of soil erosion and the forest ecology. Twenty-three sites were selected at 200 m intervals of altitude on east and west facing slopes.Surveys were made of the geomorphology and soils, both of which were mapped, and field measurements made of various site and soil properties related to splash erosion (raindrop size distribution, area of exposed soil and lowest canopy height), erosion by overland flow (infiltration rates, occurring of runoff producing zones) and biogenic erosion. Soil samples from the A1 horizon were collected for laboratory analyses (bulk density, aggregation and organic matter content).The results of the investigation are reported with respect to forest type and altitude, and aggregate stability, permeability and infiltration rates are treated as dependent variables in multiple regression analyses.In an attempt to synthesise the total effect of site conditions on erosion, splash and overland flow indices are developed. These would suggest that splash erosion is most active in the Subandean forest zone due to the relatively large area of exposed soil and the greater height of the lowest canopy. However, conditions within the Subandean zone are quite variable. Runoff producing zones are precluded in some areas by a thick root mat and tend to be most frequently found in relatively open woodland in the zone of maximum rainfall in the Subandean forest. They also occur quite frequently in the Warm Tropical forest zone.The volcanic ash soils are in many cases less permeable than might be expected and it is concluded that under cultivation, when soils are able to dry out, the permeability is likely to increase. Lower water retention and higher rates of percolation might then encourage mass movements.The relationships described require verification of the assumptions inherent to the indices by field measurement. Further research should be conducted into the nature of the interrelationships between erosion processes and forest ecology within the broad ecological units considered here.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880065

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTAnalysts of rainfall over Ghana have traditionally concerned themselves with the attempts to explain the rainfall anomaly along the coast of the country in terms of the nature of the coast, and some upwellings of cold waters off coast of Accra. Rarely is the problem percieved as a meteorological process that causes the anomaly. Examined in this paper are the monthly and annual rainfall distribution along the coast of Ghana. Also examined are the weather and climatic mechanisms, and the effect of the sea and the coast on the rainfall distribution over the eintire coast. The results show that the rainfall anomaly over Ghana's coastal region is due mainly to meteorological factors

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880066

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTUnusually large coastal dune formations occur on the east coast of Cape York Peninsula, North Queensland, an area which experiences a seasonally humid tropical climate. This paper describes the morphology and development of dunes at Cape Bedford and Cape Flattery, north of Cooktown. The dunefield consists of several generations of superimposed parabolic and elongate parabolic dunes, the older members of which are deeply weathered. The large scale of dune development in this area reflects an abundant sand supply from widespread outcrops of Mesozoic sandstones and older granites on the neighbouring part of Cape York Peninsula, and the exposed location of Cape Bedford and Cape Flattery in relation to the prevailing southeasterly winds. Many of the dunes are stabilized at the present day, and the major periods of dune formation appear to have taken place earlier in the Holocene or Pleistocene.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880067

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

ABSTRACTThe Uppsala esker between Arnöhuvud and Valsgärde, i.e. from c. 16 km SSW to c. 7 km N of Uppsala, was mapped around 1940 by Uppsala geography students. On most of the maps, ancient shorelines are indicated and can be stratified to contour intervals of 2 m. It was found that the ancient shorelines appear more concentrated in some vertical intervals than others. Comparison with a preliminary shore displacement curve for the area indicates some correspondence between halts or transgressions in shore-displacement and accumulation of ancient shorelines. On the other hand, during phases of rapid regression of the shore few shorelines were developed. Thus, the idea of G. De Geer (1932 and 1940) that the shorelines of the Mälar valley were developed during occasional strong storm surges from the west must, on the whole, be abandoned. However, eustatic transgressions due to melting glaciers might also be correlated to times of high cyclonic activity with frequent storm surges that could encourage shoreline development. It is also suggested that a transgression of sea level might erase shorelines earlier formed.

ISSN:0435-3676    

DOI:10.1080/04353676.1982.11880068

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor