ISSN:0197-9337    

DOI:10.1002/esp.3290070402

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractEquilibrium is defined as a single‐valued, temporally invariant functional relationship between the values of an output variable and the values of the input variable(s) in a geomorphic system. Disequilibrium occurs if the output deviates from the functional relationship by more than a consensual degree. Natural geomorphic variables are characterized by a relaxation time. Output variables are insensitive to cyclical inputs with frequencies much greater than the relaxation time, but can respond completely for sufficiently low frequencies. Rapid trends, recent step changes or pulse inputs, and intermediate frequency inputs can cause disequilibrium.The gradient of sand‐bed alluvial channels (the output variable) is determined by sediment and water delivery from slopes (the input variables), and changes in this hydraulic regime require regrading by erosion and deposition. Initial stages of adjustment to changed regime in a long, unbranched channel with sediment and water delivery only at the upstream end propagate downstream, but later stages of adjustment occur simultaneously throughout the reach. In a dendritic channel network the gradient responds rather uniformly throughout the network to changes in regime during all stages of adjustment. The time scale of adjustment to changed regime depends upon the size of the channel network (or stream length), the sediment and water discharges, and to a lesser degree upon the magnitude of the change.Grade as defined by Mackin (1948) is synonymous with equilibrium as used in this paper if ‘a period of years’ is replaced by ‘a time period commensurate with the relaxation time of the gradient’. The use of the term grade is best restricted to a single‐valued relationship between channel gradient and the hyd

ISSN:0197-9337    

DOI:10.1002/esp.3290070403

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe conclusions of Ovenden and Gregory (1980) are reviewed in the context of a stream network on the blanket peat moorland of the Southern Pennines. The very great disparity between the 1:10560 map network and the present channel system suggests that the original survey only included the major tributaries. Map accuracy in areas of peat moorland must therefore be treated with some caution particularly if no air photograph or field checking can be done. Some problems of network definition in the peat moorlands are also briefly discussed.

ISSN:0197-9337    

DOI:10.1002/esp.3290070404

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractA laboratory experiment using a two‐dimensional wave tank was designed to investigate the mechanism of erosion at a cliff base by waves armed with rock fragments. The experiment was performed under constant wave conditions by systematically changing the amount of beach sand at the foot of steep model cliffs of the same slope and strength. Cliff erosion occurred when the beach material at the cliff/beach junction was moved by waves. Turbulence created by bores rushing up on the beach mobilized the sand and exerted a mechanical shearing force on the cliff face using the sand as an abrasive. The analysis of results indicated that the effect of the abrasive doubled when the cliff/beach junction was located above Still Water Level (SWL) as compared to when it was below SWL. The assailing force of the sediment‐laden water masses was proportional to the square of the bore speed immediately in front of the cliff face. The factor of proportionality is related to the quantity of beach sand entrapped in the turbulent fl

ISSN:0197-9337    

DOI:10.1002/esp.3290070405

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractDesert varnish is reported to have formed in 25 years on desert pavement stones in an abandoned road south of Barstow, California. It has been discovered that stones buried close to the surface of the roadbed and adjacent desert pavement bear the same dark desert varnish as the exposed stones at the surface. This and other observations refute the claim of 25 year old varnish.

ISSN:0197-9337    

DOI:10.1002/esp.3290070406

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractUpland gravel‐bedded streams in the U.K. have received only scant attention from both hydrologists and sedimentologists, but are worthy of further investigation. The sedimentology of three small streams in Teesdale in the Pennines has been examined in detail. Grain‐size characteristics, bedforms, structure, composition and packing characteristics of these deposits are described, and compared where appropriate with published information.It is argued that a fuller appreciation of gravel bed composition and morphology should eventually contribute to an improved understanding of sediment transport and deposition mechanisms, and, hence, to improved accuracy in sediment transport and deposition estima

ISSN:0197-9337    

DOI:10.1002/esp.3290070407

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe postglacial sediment record of Lake Manitoba is composed dominantly of silty clay to clayey silt with little variation in most physical, chemical, and mineralogical properties. Distinct in the sedimentary sequence of this large lake, however, are four zones that have a low moisture content, blocky to pelletal structure, and gleyed colour. All of these zones formed during the warmest and driest postglacial period in the region, 9500 to 4500 years ago. Although several possible hypotheses can be formulated regarding the origin of these zones including changes in sedimentation rate, clay mineralogy, lake chemistry, and depth of winter freezing, the most likely explanation is that they represent pedogenic horizons. Formation by pedogenesis during dry or extremely low water conditions is not mutually exclusive of the other hypotheses, and several are favoured by low water conditions.

ISSN:0197-9337    

DOI:10.1002/esp.3290070408

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractLittle attention has been paid to the role of sidewall processes in gully development. Simple estimates of linear incision/sidewall erosion ratios at two localities in New South Wales, Australia suggest that sidewall erosion is responsible for more than half the gully volume. Studies at three localities where overland flow and throughflow are limited to only one sidewall indicate that these processes are responsible for 10‐30 per cent of gully volume. These observations have important implications for gully managemen

ISSN:0197-9337    

DOI:10.1002/esp.3290070409

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290070410

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290070411

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY