ISSN:0197-9337    

DOI:10.1002/esp.3290170502

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290170503

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractValley recognition methods given in the literature fail to produce valley networks suitable for locating valley heads for one of two main reasons: (a) they are based on the concept of [higher than] or (b) they are based on contributing area thresholds. In this paper a new method for recognizing valley bottoms is presented. This is based on two improvements of Carroll's (1983) method, and produces a network that reflects the topography well. The network is used to locate valley heads. Once located, the valley heads are delineated using criteria suggested by geomorphologists and hydrologists. The resultant valley heads are generally well recognized although two problems are evident: (a) there are a number of commission errors; and (b) the valley heads recognized by the method are too small.

ISSN:0197-9337    

DOI:10.1002/esp.3290170504

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractProcess inference in geomorphology is hindered by a lack of information on the true temporal distribution of contemporary erosional and depositional activity. To tackle this problem a low‐cost, automatic monitoring system based on the photo‐electronic erosion pin (PEEP) sensor has been developed. The PEEP is essentially an array of photosensitive cells enclosed within a transparent tube and connected by cable to a datalogger. When inserted into an eroding landform, subsequent retreat of the face exposes more photosensitive cells to light which increases PEEP voltage output. Deposition decreases sensor outputs. The logged signals thus reveal the magnitude, timing and frequency of erosion and deposition events with much greater precision than has hitherto been possible. Measurement principles, electronic and physical design, calibration, field installation, problems and prospects and pilot results from a river bank erosion site are discussed. The PEEP system appears to have great potential for disentangling competing hypotheses in geomorphological process studies, and in building and testing erosion and sediment transport models of high temporal resolut

ISSN:0197-9337    

DOI:10.1002/esp.3290170505

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIn a basin developed on a stream table, effluent subsurface flow supported a channel network that evolved by a combination of headward growth, lateral widening and divide decay. The area occupied by the developing network increased with time. Circularity was used to characterize network evolution which occurred in three phases (initiation, extension and abstraction). Basin sediment discharge declined exponentially with time. Pronounced quasi‐cyclic variability was superimposed upon this general trend. Some of the variability was directly linked to changes in the amount of sediment supplied to the channel. The variation of mean network sediment yield (mean sediment discharge scaled by network area) with time adequately described the general decline in sediment discharge as the network evolve

ISSN:0197-9337    

DOI:10.1002/esp.3290170506

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractMorphometric analyses of glaciated valleys typically involve attempts to fit empirical data from valley cross‐profiles to quadratic (parabolic) or power‐law equations, with the choice of equation depending on the goal of the analysis. In assessing the relative merits of these two types of equations, some confusion has arisen because of apparent variations in coordinate system datums between studies which have made use of the power‐law equation. However, we show that this confusion relates to a simple mathematical error, rather than any true difference in methodology. Of more significance, however, is the fact that in fitting a power‐law equation to observed profiles, significant bias is introduced by the use of a logarithmic data transformation. Because of this implicit bias, power‐law equation parameters are influenced most strongly by data points close in elevation to the centre of the valley, and so failure to account for the depositional elements which frequently occur in these areas can lead to significant errors if the aim of the analysis is to characterize the form of the erosiona

ISSN:0197-9337    

DOI:10.1002/esp.3290170507

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe combined effects of climate and tectonism on general terrace stratigraphy and valley asymmetry during the last half million years in the Allier system (France) are simulated by a 3‐D conceptual model (LIMTER). This model allows the formulation and evaluation of long term terrace formation scenarios for the Allier system. Simulation results suggest that terrace stratigraphy in the study area is mainly the result of internal dynamics and climatic change. Local tectonism contributed to the development of unpaired terraces while the general regional uplift played a dominant role in determining terrace formation and preservation in genera

ISSN:0197-9337    

DOI:10.1002/esp.3290170508

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractBedforms and their migration are among the most important features determining bed load transport on point bars in sand‐bedded rivers. A case study has been carried out in the Danish river Gels Å in a bend with equilibrium point bar topography. Bedforms (dunes) were repeatedly surveyed to determine the bedform migration on the point bar surface. Bedforms occur in two categories in the bend: primary dunes and secondary dunes migrating transversely in the troughs between primary dunes. The study shows that the migration of these bedforms can account for the entire lateral transport known to concentrate the transport in the convex half of the cross section at the bend exit. The bedform transport is induced by both dune categories, partly by turning of the primary dunes towards the convex bank and partly by the migration of secondary dunes. In certain areas, the two categories operate together and thus make the lateral transport particularly large; it is shown that almost 60 per cent of the entire lateral transport in the bend takes place within less than 30 per cent of the streamwise extent of the point b

ISSN:0197-9337    

DOI:10.1002/esp.3290170509

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA relationship between discharge, flow velocity and flow area in rills is established using data from four field and laboratory studies. The proposed relationship is shown to predict successfully flow velocities measured in six other studies. Although slopes range from 0.035 to 0.45 and soil materials range from stony sands over silt loams to vertisols, mean flow velocity can be well predicted from discharge alone. Thus, there is no important influence of slope and/or soil material characteristics on flow velocities in rills. The proposed relationship may be used to improve performance of deterministic flow routing models when applied to rilled catchments. Furthermore, it allows the calculation of unit stream power, which has been shown to be related to the transporting capacity of overland flow, in terms of slope and discharge.

ISSN:0197-9337    

DOI:10.1002/esp.3290170510

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractData from Turkey Brook are used to demonstrate that the interaction between gravel bedforms, flow resistance and bedload transport is a dynamic one, both between and within hydrographs. and that creation of a significant component of form drag through construction of microforms (pebble clusters) may precede the eventual break‐up of the bed in a transport event. This process of drag augmentation', which can be seen as a feedback mechanism delaying transport and can be likened to dilation of a soil tested in a direct shear apparatus, itself appears to be dependent on the characteristics of turbulence, and therefore involves feedback at a finer resolution than envisaged by Hassan and Reid (1990

ISSN:0197-9337    

DOI:10.1002/esp.3290170511

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY