ISSN:0197-9337    

DOI:10.1002/esp.3290070203

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractRain and throughfall drops were sampled during rain events in a New Zealand beech forest and the frequency distributions of drop mass and kinetic energy calculated. The kinetic energy of throughfall under the canopy was always greater than that of rainfall in the open, notwithstanding interception losses. During a typical rain event in which 51 mm fell in 36 h, the total kinetic energy of throughfail was 1.5 times greater than that of rainfall, and the mean amount of sand splashed from sample cups was 3.1 times greater under the canopy than in the open. It appears that where mineral soil is exposed at the surface, by animal trampling or burrowing for example, rates of soil detachment by splash under a forest canopy will probably exceed those in the open.

ISSN:0197-9337    

DOI:10.1002/esp.3290070204

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractA comparison was made between the distal ends of twenty‐two avalanche and fifteen non‐avalanche slopes in the San Juan Mountains of Colorado, U.S.A. All slopes occurred in the subalpine zone. Six characteristics were used for analysis: type of slope, surface material, longitudinal profile, perched debris or debris tails, avalanche impact on opposite valley wall, and transverse profile. Both fan and roadbank avalanche slope types were found along with the non‐avalanche slopes. Almost all slopes were turf covered rather than talus since the work was done below treeline. Twenty avalanche slopes had a distinctive concave longitudinal profile. Little debris of any kind was found since the slopes were in an area of insignificant amounts of detritus. Many of the larger and two of the smaller avalanche slopes showed evidence of impact upon the opposite slope. Eighteen of the avalanche slopes had convex transverse pro

ISSN:0197-9337    

DOI:10.1002/esp.3290070205

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractA five‐stage model of the development of cross‐sectional asymmetry is proposed in which alternating bar deposition and bed scour are important elements. Quasi‐periodic reversals in the sense of asymmetry and a progressive increase in the magnitude of asymmetry at sections which develop an asymmetry initially are major features of the model. Application of Bridge's (1977) model confirms several features of the model and suggests that the degree of asymmetry is directly related to bend curvature. After the initial stages, subsequent changes to the cross‐sectional and planimetric form of the channel may be intensified by the developing asymmetry through a system of positive feedbacks in which the levels of form and flow distortion are interrelated. Asymmetry appears to provide an important link between cross‐sectional and plan form adjustment.Spatial series of asymmetry obtained for three lengths along a mountain stream contain features predicted by the model. In particular, the dominant peak in spectral density functions occurs at a frequency with a corresponding wavelength close to 4πwwhich has significance in terms of the meander wavelength‐width relationship (Richards, 1976a). This consistency is remarkable considering local differences. In addition, sections in curved reaches tend to be more asymmetric, especially when sited at pools. However, contrary to expectation, channel width is not significantly correlated wi

ISSN:0197-9337    

DOI:10.1002/esp.3290070206

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractLarge cliff failures involving forward toppling over a basal hinge have occurred on more than half of the plateau edge of Ben Lomond, northeastern Tasmania. This mode of failure, which is readily identified from the columnar structure of the dolerite involved, has affected up to 107m3of rock at a time and a total of more than 50 × 106m3in all the cases which can still be identified. It represents perhaps the most important form of cliff retreat, amounting to a rate of 0.2 mm yr−1over the last 100,000 years.Topographic evidence and joint surveys suggest that two different mechanisms have produced the topples on Ben Lomond. One has involved failure in the sediments underlying the dolerite with consequent foundering and cambering of large sections of the plateau edge. This mechanism accounts for relatively few of the Ben Lomond topples, though it includes the largest individual cases. The second mechanism, dominant in most of the topples, involved slab failure in the cliffs. Both modes of failure have been facilitated by vertical weaknesses within the bedrock and both require an initially steep cliff profile. Because of the latter requirement, which is not met on the other mountains of northeastern Tasmania, large‐scale topples are found only on Ben Lomond, and only there where glacial steepening of the cliff has been possible. Following the initial failure, topples of both types have migrated downslope by block sliding for distances up to

ISSN:0197-9337    

DOI:10.1002/esp.3290070207

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe development and testing of sediment simulation models require continuous monitoring of erosion processes and sediment yields from catchment areas at a wide range of scales. A series of experiments are described in which runoff and sediment yields from a small laboratory catchment were monitored through six consecutive storms applied to each of three soil types. Slope microtopography and the surface particle‐size distribution were surveyed between storms. Pronounced peaks in sediment concentration at the start of each storm were not observed for these conditions, but significant variation in yield through a series of storms was shown to result from the interaction of rilling and armouring processes as the source of sediment shifted from the rills to interrill areas. In view of the experimental findings the validity of experiments reporting average or ‘stable’ erosion rates is questioned. The need for dynamic models capable of simulating rill development and changes in sediment availability is empha

ISSN:0197-9337    

DOI:10.1002/esp.3290070208

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe type and relative rate of geomorphic process activity on residual hillslopes in the White River Badlands of South Dakota were found to vary as a function of aspect‐induced differences in topoclimate. Drainage densities on north‐facing slopes several orders of magnitude greater than those on slopes facing south indicate that north‐facing slopes experience greater fluvial erosion. Comparative analysis of mass movement features suggests that north‐facing slopes are prone to relatively high‐magnitude, low‐frequency failures, whereas south‐facing slopes experience far more frequent but much smaller movements.Variations in process activity can be explained in large part by aspect‐induced differences in moisture regime. Field monitoring of moisture conditions indicates that north‐facing slopes maintain higher and less variable moisture levels. South‐facing slopes are not only drier in‐ general but are subject to more frequent and intense episodes of wetting and drying. Differences in moisture conditions promote differences in weathering activity as evidenced by thicknesses of slope regoliths. Higher moisture levels on north‐facing slopes lead to more rapid dissolution of binding cements and consequently, thicker regolith covers. On south‐facing slopes, however, regolith covers are virtually non‐existent due to both drier conditions and episodic desiccation, which triggers small rockfalls. Greater fluvial erosion on north‐facing slopes is a consequence of higher antecedent moisture levels, which retard infiltration. Further, the unconsolidated regolith cover is more erodible than the relatively unweathered materials exposed on the surfaces of south‐facing slopes. Resistance to slumps and mudflows is lower on north‐facing slopes because the weathered regolith is less cohesive than the unweathered parent material and also because the reg

ISSN:0197-9337    

DOI:10.1002/esp.3290070209

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractAerial photographs led to the detection of a previously undescribed type of river meander. These features are characterized by nearly circular pools located at the apex of the bend and are widely distributed on small to medium sized coastal plain streams in the southeastern United States. Bathymetric evidence shows that the structure of meanders containing circular pools is distinctive. Field and laboratory evidence suggests that these features are formed by a short‐lived countercurrent that develops during the flood cycl

ISSN:0197-9337    

DOI:10.1002/esp.3290070210

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractGeomorphologists have not devoted sufficient attention to the formation of clay minerals by hydrothermal activity. This paper describes the breakdown of freshly‐quarried basalt by cyclic wetting and drying. Breakdown is attributed to the swelling of hydrothermally‐derived smectite, and it is argued that the effects of endogenic processes can exert a significant control upon weathering behaviour under earth surface conditi

ISSN:0197-9337    

DOI:10.1002/esp.3290070211

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290070212

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY