摘要:

AbstractVertical velocity profiles measured over various bed configurations (plane beds, ripples, and dunes) in. the meandering River South Esk, Glen Clova, Scotland are presented on semilogarithmic paper. Local bed shear stress and roughness height are calculated from the lowermost parts of the profiles using the Karman‐Prandtl law of the wall; these parameters, and the geometrical properties of the profiles, are related to the various bed configurations. A graphical model is used to identify profiles developed on specific regions of dune geometry, in order to discriminate those profiles that define bed shear effective in transporting sediment over dunes. An assessment is made of the errors involved in estimating local mean velocity from extrapolating the law of the wall to the water surface. A Darcy‐Weisbach friction coefficient is related to bed configuration and local stream po

ISSN:0360-1269    

DOI:10.1002/esp.3290020402

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractIn 1971 and 1972, the Terrain Sciences Division of the Geological Survey of Canada carried out the largest mapping program in its history of the distribution and characteristics of terrain types. Over 140.000 mile2(360,000 km2) of the Mackenzie Transportation Corridor was evaluated. This information was supplied to the public, industry and government in order to plan and design projects properly, by efficiently utilizing natural resources and minimizing environmental damage.The requirements of potential users varied to such a degree that it was decided to map the ‘basic’ geology and other terrain characteristics so that derivative maps could be constructed for specific uses. A mapping system was devised for surficial deposits using genesis as the primary unit, modified by texture and morphology. Organic and permafrost terrain were included, factors not ordinarily a part of traditional geological mapping. The system was comprehensive and flexible enough to include such aspects as the percentages of minor units, unit thickness, and slope and other morphological characteristics. In bedrock and unglaciated areas, a second system based upon the same principles as the first but arranged in a different manner was devised. In this case, the primary unit is based upon relief, with additional information on lithology of the bedrock, texture of overlying debris, and broad morphological and slope characteristics.Comprehensive legends were prepared. Using the mapping units as the base, the legends were divided into various categories, providing information on the composition, ground ice content, thickness, and engineering characteristics of the deposits, and surface characteristics including topography, drainage pattern, vegetation, and dominant soils (pedologic sen

ISSN:0360-1269    

DOI:10.1002/esp.3290020403

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe fabrics of tills deposited by continental glaciers are usually assumed to reflect clast orientation during transportation and yet might only be imprinted during depositional processes. However, the striated surfaces of clasts must be acquired during transportation and by relating striation patterns to clast shape one can deduce the positions most frequently maintained by each group of clasts. Comparison of these orientations with the actual depositional fabrics of the same shape groups, demonstrates that dast orientations are maintained from transportation through deposition. Therefore subglacial transportation processes grade smoothly into those of deposition. The favoured interpretation is that bottom melting is the dominant mechanism leading to final deposition and that lodgement and smearing are likely restricted more to preliminary cycles of redeposition and re‐erosio

ISSN:0360-1269    

DOI:10.1002/esp.3290020404

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractSlopewash measurements were made at 449 sites on the badlands of Hong Kong over a 15‐month period. The mean amount of ground retreat was 2.17 cm and the spread of data was large (coefficient of variation = 36.6 per cent). This demonstrates a large variation in rates of slopewash in the study area. A large sample size is suggested for any future work to narrow the limits of the sampling error. It is also shown that ground retreat, as conventionally measured in the field, is different and should be distinguished from vertical lowering. In the study of erosion rates and slope evolution, different conclusions are likely to be drawn unless the distinction is realized.Various attempts have been made to account for the observed variations in slopewash rates on the badlands of the study area. It was found that the site to site variations in slopewash rate could not be attributed to the conventional soil, microtopographic and distance parameters. This absence of relationship is probably due to the fact that the sites on the slope profiles are not isolated systems, but are components of a larger functional entity, in which all sites are in some form of adjustment and equilibrium with the other

ISSN:0360-1269    

DOI:10.1002/esp.3290020405

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractOverwash deposits are characterized by horizontally layered laminations. Vertical sequences could be interpreted in terms of individual storm deposits by recognizing time breaks or discontinuities in the stratigraphic section. Results from comparison of channel deposit data for textural grading across the washover fan were inconclusive. Samples taken from individual laminations revealed the true textural grading when traced along a 61 m trench and sampled at designated localities. The overwash deposit was found to become finer in grain size from the apex to the margins of sedimentation in the direction of transport.

ISSN:0360-1269    

DOI:10.1002/esp.3290020406

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractSediment transport for five small watersheds in arid southern Israel, eroded into shales, chalks, anhydrites and alluvium is studied. Analysis includes data from three large watersheds in the southern United States. Results indicate that floodwater heavily laden with suspended load (10‐60 per cent, by weight) is characteristic of watersheds cut in erodible materials. No correlation was found between environmental characteristics such as lithology, catchment area, angle of slope or rainfall intensity and suspended‐sediment concentration or texture. The carrying capacity for sands, derived both from hillslopes and channel alluvium is greatly increased by high suspended silt concentration, the trend being\documentclass{article}\pagestyle{empty}\begin{document}$$ R \propto C_s^{- 2.5} $$\end{document}(whereR= ratio, % fines/% sand;Cs= suspended load concentration, per cent by weight). The high concentration of fine sediment effectively causes more sand transport than would normally occur. This is also true for transport of coarser clastics; higher velocities, typical of highly concentrated silt suspensions, increased competence for transporting pebbles and boulders. The action of a large variety of processes (splash, wash, rilling, gullying, sliding, mudflow) combine with low infiltration and high credibility to render every rainstorm erosionally effective, and high concentrations of washload increase both the capacity and competence of coarse clastic transport. Whole basins are thus subjected to high rates of denudation (2‐10 m

ISSN:0360-1269    

DOI:10.1002/esp.3290020407

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractRecent arguments that the straight parts of talus slopes stand, in general, at angles less than the angle of repose of the talus material are considered in relation to different test procedures used in the measurement of the repose angle. Observations on coarse, well sorted, angular fragments showed no significant difference between the values for this angle determined in laboratory tilting‐box tests and determined during outdoor cone build‐up by rapid discrete particle rockfall. Measurements did indicate, however, that laboratory tests in which specimen size (in relation to particle size) is small produce steeper repose angles which are unrealistic in the field context. A detailed description is provided of process and form changes which occurred on large cones built up by stockpiling of crushed stone in a limestone quarry. These observations indicate that the processes of discrete particle rockfall and of avalanching of talus material may not be as independent of each other as previously suggested, and, together with the values of the repose angle of the cone material (35°), provide some support for the traditional view that talus slopes do, in fact, stand at or close to the repose angle of the talus mate

ISSN:0360-1269    

DOI:10.1002/esp.3290020408

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractOne of the major problems of shingle beach dynamics is the method by which coarse gravel is transferred from beach face to storm beach, the latter often lying several metres above high spring tidal levels. The mechanism which is usually proposed, cites the action of plunging breakers as being central to this problem of sediment transfer. However, the nature of net residual fluid force of plunging breakers is deemed unsatisfactory for any substantial upbeach (onshore) sediment transport during storm conditions on gravel beaches. A mechanism is proposed by which high still water levels due to high astronomical tides, onshore storm force winds and allied wave surge, promote shoaling characteristics and beach profile changes which are conducive to spilling breaker development at tidal extremities. It is the net onshore fluid force vector of the spilling breaker overtopping the beach crest which may be the cause of extreme sedimentation events on the storm beach. An example of such sediment transfer is given for a known storm beach sedimentation event at Llanrhystyd gravel beach, West Wales, during February 1974. Process variables were monitored on several days allowing the use of an inshore breaker steepness criterion, to indicate positions in the tidal regime where plunging breakers give way to spilling forms. This example serves to suggest that more attention should be given to the nature and characteristics of shoaling waves, especially in respect of breaker type, when examining problems of shingle beach dynamics and sedimentation.

ISSN:0360-1269    

DOI:10.1002/esp.3290020409

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractBed topography and grain size are predicted for steady, uniform flow in circular bends by consideration of the balance of fluid, gravity and frictional forces acting on bed load particles. Uniform flow pattern is adequately described by conventional hydraulic equations, with bed shear defined as that effectively acting on bed load grains. This analysis is used as a basis to predict bed topography and grain size for steady, non‐uniform flow in non‐circular bends (represented by a ‘sine‐generated’ curve). The non‐uniform flow pattern is calculated using the method of Engelund (1974a). Equilibrium bed form, hence sedimentary structure, is found by comparison of existing flow conditions with one of the schemes describing the hydraulic stability limits of the various bed forms.The model was compared with bankfull flow observations from a channel bend on the River South Esk, Scotland. Theoretical bed topography and velocity distribution were very close to the observed data. However, bed shear stress showed only a broad agreement, probably because of the use a constant friction coefficient value. Mean grain size distribution showed good agreement, but theory did not account adequately for gravel sizes in the talweg region and on the upstream, inner part of the bar, possibly due to theoretical underestimation of effective bed shear. Bed form and sedimentary structure are predicted well using the familiar stream power‐grain size scheme.The behaviour of the model under unsteady uniform flow conditions in circular bends was analyzed, and suggests that any variation of grain size and bed topography with stage is likely to be limited to deeper parts o

ISSN:0360-1269    

DOI:10.1002/esp.3290020410

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe equilibrium stream represents a compromise between three tendencies: (i) to maximize grain size, (ii) to maximize quantity of bed load transported, and (iii) to minimize bed shear stress (which represents, among other things, water discharge).

ISSN:0360-1269    

DOI:10.1002/esp.3290020411

出版商:John Wiley&Sons, Ltd    

年代:1977

数据来源: WILEY