摘要:

AbstractGeomorphological evidence and recent trash lines were used as stage indicators in a step‐backwater computer model of high discharges through an ungauged bedrock channel. The simulation indicated that the peak discharge from the 26.7 m2catchment was close to 150m3s−1during the passage of Hurricane Charlie in August 1986. This estimate can be compared with an estimate of 130–160 m3s−1obtained using the Flood Studies Report (FSR) unit hydrograph methodology. Other palaeostage marks indicate that higher stages have occurred at an earlier time associated with a discharge of 200 m3s−1. However, consideration of both the geometry of a plunge pool and transport criteria for bedrock blocks in the channel indicates that floods since 1986 have not exceeded 150 m3s−1. Given that the estimated probable maximum flood (PMF) calculated from revised FSR procedure is at least 240 m3s−1, it is concluded that compelling evidence for floods equal to the PMF is lacking. Taking into consideration the uncertainty of the discharge estimation, the 1986 flood computed using field evidence has a minimum return period of 100 years using the FSR procedure. This may be compared with a return period for the same event in the neighbouring gauged River Greta of>100 years and a rainfall return period of 190 years. In as much as discharges of similar order to FSR estimates are indicated, it is concluded (a) that regional geomorphological evidence and flood simulation within ungauged catchments may be useful as a verification for hydrological estimates of recent widespread flood magnitude and (b) that palaeohydraulic computation can be useful in determining the magnitude of the local maximum [historic] flood when determining design discharges for hydraulic structures within specif

ISSN:0885-6087    

DOI:10.1002/hyp.3360080602

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA method for collecting suspended sediment samples has been developed that pumps a discharge‐weighted volume of water from fixed depths at four to 40 locations across a river and separates the suspended sediment in the sample using a continuous‐flow centrifuge. The efficacy of the method is evaluated by comparing the particle size distributions of sediment collected by the discharge‐weighted pumping method with the particle size distributions of sediment collected by depth integration and separated by gravitational settling. The pumping method was found to undersample the suspended sand sized particles (>63 μm) but to collect a representative sample of the suspended silt and clay sized particles (<63 μm). The centrifuge separated the silt and clay sized particles (<63 μm) into three fractions. Based on the average results of processing 17 samples from the Mississippi River and several of its large tributaries in 1990, about 10% of the silt and clay sized material was trapped in a centrifuge bowl‐bottom sealing unit containing the nozzle and consisted of mostly medium and coarse silt from 16 to 63 μm. About 74% was retained on a Teflon liner in the centrifuge bowl and consisted of sizes from 0–1 to 63 μm. About 9% was discharged from the centrifuge in the effluent and was finer than 0–1 μm. About 7% was lost during the processes of removing the wet sediment fractions from the centrifuge, drying and weighing.The success of the discharge‐weighted pumping method depends on how homogeneously the silt and clay sized particles (<63 μm) are distributed in the vertical direction in the river. The degree of homogeneity depends on the composition and degree of aggregation of the suspende

ISSN:0885-6087    

DOI:10.1002/hyp.3360080603

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe distribution of soil137Cs in relation to selected soil and landform properties was studied across a 16 ha hillslope hollow in the Hunter valley, New South Wales, Australia. The hillslope was used as grazing for cattle. Caesium‐137 was not significantly related to the amount of sand, silt, or clay, the bulk density, the organic matter content, the slope angle or the relative distance downslope. However,137Cs was significantly related to the thickness of the soil A horizon. Spatial variations in137Cs were compared with topographic units and a six‐element hillslope model, but there was little correspondence. It was thought that the effects of microtopography could have masked potential interrelationships between137Cs and broader scale landform paramet

ISSN:0885-6087    

DOI:10.1002/hyp.3360080604

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractSimilarity and scaling theory are applied to soil physics, specifically to several parameters of unsaturated soil water movement. Following a dimensional analysis of Richards' equation, a mechanical similarity criterion of the hydraulic parameters is developed. Dimensionless factors which conform to assumptions of kinematic and dynamic mechanical similarity in the flow system are converted to relations using the scale factor a derived under the assumption of geometric similarity. As an example, the infiltration process is assessed through scaling of the parameters in Philip's equation, using experimental data from double‐ring infiltration measurements at 54 locations in a study catchment as the scaling tes

ISSN:0885-6087    

DOI:10.1002/hyp.3360080605

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractHydrological and hydrochemical parameters for two mountain basins are presented and compared. The analysis focuses on the hydrology during the winter, the cumulative outflow of sulphate and nitrate from the basin and a mass balance. An integrated model for the simulation of the amount and quality of snowmelt from seasonal snow cover is briefly described. The possible application of the model to other basins is considered.

ISSN:0885-6087    

DOI:10.1002/hyp.3360080606

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractEphemeral channels in arid regions convey larger amounts of sediment than perennial channels in humid regions. Sediment graphs at the outlet of channels have been derived by the standard sediment rating curve technique and by a lumped model based on the instantaneous unit sediment graph (IUSG) concept. The IUSG gives estimates of sediment transport that are better than those derived with the sediment rating curve as it takes into account the availability of erodible material within the channel bed.

ISSN:0885-6087    

DOI:10.1002/hyp.3360080607

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractComparative hydrology attempts to identify regions with similar environmental attributes and then compares the hydrological activities in these regions to facilitate the transfer of knowledge and exchange of techniques. As a case study, the mountainous regions of Canada and China were compared. Vertical zonation is a characteristic feature of such regions, generating contrasts in microclimate, vegetation, soil and the resultant hydrological responses. An increase in precipitation with altitude is modified by aspect and other local factors. In temperate and colder latitudes, snow and ice are important, especially at higher elevations. Both countries have conducted many hydrological studies on snow and glaciers, but evaporation in mountainous terrain merits more attention. Runoff from mountainous catchments is often generated by a range of processes including rainfall, snowmelt and glacier melt, and runoff response to water input tends to be rapid. This study identifies some of the strengths and weaknesses of our current knowledge of mountain hydrology in both countries, and suggests that a more comprehensive treatment of the subject will improve the prediction of the hydrological behaviour of such regions.

ISSN:0885-6087    

DOI:10.1002/hyp.3360080608

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:0885-6087    

DOI:10.1002/hyp.3360080609

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:0885-6087    

DOI:10.1002/hyp.3360080601

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY