ISSN:0197-9337    

DOI:10.1002/esp.3290140802

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractDischarge characteristics in six adjacent mountainous watersheds in northern New Mexico, U.S.A., vary substantially between basins underlain by different lithologies. Relatively resistant gneisses and granites underlie two basins (drainage areas: 43 and 94 km2) that have high unit discharge (0·010 to 0·14 m3s−1km−2), high bankfull discharge, and sustained high discharge. Less resistant sandstones and shales underlie four basins (drainage areas: 96 to 215 km2) that have relatively low unit discharge (0·001 to 0·005 m3s−1km−2), relatively low bankfull discharge, and peak discharges that are not sustained as long as those in the crystalline terrane.Analysis of snowmelt‐runoff water budgets suggests that three factors control hydrologic conditions in the basins. First, area‐elevation distributions appear to control the timing and amounts of water input. These distributions probably reflect the erosional resistance of the different lithologies. Second, lithology appears to control runoff production in areas having minor amounts of storage. Third, glacial deposits in headwater regions control discharge duration and timing via storage and return flow releases. The amount of return flow released by glacial deposits, however, is probably controlled by the permeability of underlying bedrock. Therefore it appears that the duration, timing, and magnitude of discharge events in the study area are controlled both directly and indirectly by lithology.Stream power and shear stress estimates derived from bankfull discharge and bed‐material size data suggest that higher bedload transport rates and larger bedload particle sizes exist in streams draining crystalline rocks than in streams draining sedimentary terrane. It appears that source‐area lithology, by controlling discharge production, also influences stream power, bedload transport capabilities, and therefore total amounts o

ISSN:0197-9337    

DOI:10.1002/esp.3290140803

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAnalysis of grain size statistics of upper foreshore sediments on sand beaches at two tidal inlets in New Jersey, U.S.A. reveals that sediments are coarser at beaches flanking the inlets than updrift, although sediments become finer downdrift at the broad, regional scale. The local reversal of the regional trend in size grading is attributed to: (1) the offshore diversion of the finer sands along the surf zone on the ebb tidal delta, and (2) the removal of the finer sands from the inlet flank beach caused by low wave energy conditions at low stages of the tide and by deflation. Sediments thus become coarser at inlet beaches as a result of alterations in the interaction of waves with the beach and as a result of aeolian processes, not solely as a result of increased tidal current velocities as previously reported. The distance along the New Jersey barrier islands over which inlet processes are likely to affect changes in sediment size updrift averages less than 1100 m, but the impacts of inlets on the sedimentary record can be extended greater distances as a result of inlet migration.

ISSN:0197-9337    

DOI:10.1002/esp.3290140804

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPredictive models for calculating sediment yield and discharge require accurate areal data. Such models may be unrealistic when using digitized data given the potential error involved in compiling and digitizing thematic polygon maps.The estimation of boundary variability for digitized polygon maps of a 0·34 km2area of badlands in Dinosaur Provincial Park, Alberta shows the effects of positional errors introduced during mapping and digitizing processes. Polygon overlay of maps of surface features and slopes produced high frequencies of very small polygons and some unlikely combinations of slopes and surface features, and decreased reliability in areal measurements in the composite map. At an epsilon band width of 0·7 m, a reasonable estimate of boundary variability, 31·7 per cent of the resultant overlaid map can be considered unreliab

ISSN:0197-9337    

DOI:10.1002/esp.3290140805

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe velocities with which grains were observed to emerge from a sand bed after an intersaltation collision atu*= 40 cm s−1are reported for four bed attitudes, from horizontal bed to adverse bed slope 15°. The principal effect of bed angle is to alter the magnitude and direction of the ricochet velocity. However, emergent velocities of dislodged grains are consistent with reptation path lengths comparable to the length of the upwind face of ripples in the corresponding wind.Calculations of the loss of forward momentum at collision, using the data for the range of bed attitudes studied suggest that creep is most vigorous on the sloping upwind face of the ripple and diminishes at the crest. As a result, the crest would be expected to accumulate the coarse material which moves predominantly by creep.The saltations originating in ricochet from the sloping back of the ripple are more vigorous and more concentrated in plan than are those originating at the crest. However, the saltation path length is at least an order of magnitude greater than the ripple wavelength and the probability distribution of path lengths is quite dispersed. Consequently it is very unlikely that these spatial patterns of ricochet are preserved sufficiently distinctly in the saltation cloud and subsequent collision distribution to be the agent of ripple development.This study therefore supports a view of moving grain interaction with the bed in which saltation provides the power to mobilize grains but ripple growth is associated with reptation and particularly with a pattern of impact which develops with the bed relief. Creep is more active on upwind facing slopes than at the crest, which therefore is a zone of net creep grain depositi

ISSN:0197-9337    

DOI:10.1002/esp.3290140806

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractMarkov models offer an objective and quantitative method of assessing beach changes. For a stretch of the Holderness coast a beach classification scheme was devised and a probabilistic first order matrix model based on surveyed profile data was produced. This could describe and predict transitions between beach types and between different time periods. Different profile types dominated different coastal locations and seasonal variations were seen. In order to improve the accuracy of prediction throughout the year a second, ‘winter’, model was added to the original ‘summer’ one. Although the models had been prepared independently of wave conditions, a comparison of the wave record and beach transitions revealed that waves under 0·3–0·5 m high produced fairly static beaches; when waves were between 0·5 and 1·0 m the beach was more dynamic and variable, while waves over 1·0 m led to the depletion of the upper beach. This was broadly in accordance with published theory. Markov models have the advantage that they can be adjusted periodically if conditions change, and are thus useful for prediction on coasts for which no wave

ISSN:0197-9337    

DOI:10.1002/esp.3290140807

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA Schmidt test hammer was employed to assess the aggregate surface hardness of samples of boulders dug out from under late‐lying snowpatches at sites in Switzerland, Scotland and Norway. The results were compared with an equivalent set of readings made on boulders at nearby snow‐free control sites. The results in every case reveal that the aggregate surface hardness of boulders buried by late‐lying snow is significantly less (at the 0·001 level) than that of boulders at the corresponding control sites. This result indicates that late‐lying snow significantly enhances rock weathering, probably because boulder and rock surfaces are exposed to prolonged wetting by percolating meltwater under late‐lyin

ISSN:0197-9337    

DOI:10.1002/esp.3290140808

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290140809

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290140810

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290140811

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY