Suspended sediment dynamics in a steep,glacier‐fed mountain stream,Place Creek,Canada     

G. Richards  R. D. Moore 《水文研究》2003,17(9):1733-1753

This study examined suspended sediment concentration (SSC) during the ablation seasons of 2000 and 2001 in Place Creek, Canada, a steep, glacier‐fed mountain stream. Comparison of stream flow in Place Creek with that in an adjacent, almost unglacierized catchment provided a rational basis for separating the ablation seasons into nival, nival–glacial, glacial and autumn recession subseasons. Distinct groupings of points in plots of electrical conductivity against discharge supported the validity of the subseasonal divisions in terms of varying hydrological conditions. Relationships between SSC and discharge (Q) varied between the two study seasons, and between subseasons. Hysteresis in the SSC–Q relationship was evident at both event and weekly time‐scales. Some suspended sediment released from pro‐glacial Place Lake (the source of Place Creek) appeared to be lost to channel storage at low flows, especially early in the ablation season, with re‐entrainment at higher flows. Multiple regression models were derived for the subseasons using predictor variables including Q, Q², the change in Q over the previous 3 h, cumulative discharge over the ablation season, total precipitation over the previous 24 h and SSC measured at 1500 hours as an index value for each day. The models produced adjusted R² values ranging from 0·71 to 0·91, and provided tentative insights into the differences in SSC dynamics amongst subseasons. Introduction of the index value of SSC significantly improved the model fit during the nival–glacial and glacial subseasons for both years, as it adjusts the model to the current condition of sediment supply. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Observations of the Dust Around Evolved Stars     

H.J. Walker  I. Heinrichsen  P.J. Richards 《Astrophysics and Space Science》1997,255(1-2):481-482

ISOPHOT has been used to obtain low resolution spectra from 2.5μm to 5μm and 5.8μm to 11.6μm and multi-aperture photometry at 60μm of several evolved stars; oxygen-rich and carbon-rich (including the peculiar carbon-rich stars R CrB and RY Sgr). R CrB was observed early in the ISO mission, 3 weeks after it had been at minimum light. Another spectrum was obtained several months later. The second spectrum shows that the broad plateau (from around 6μm to 8μm) is still present but the flux density has declined from 60Jy to 50Jy. The spectrum for RY Sgr shows the same type of plateau. The multi-aperture data suggest that the dust shells are resolved around R CrB, RY Sgr, Y CVn and RS Lib. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Evidence for Co-Propagation of 4765- and 1720-MHz OH Masers in Star-Forming Regions     

A. Niezurawska  M. Szymczak  A. M. S. Richards  R. J. Cohen 《Astrophysics and Space Science》2005,295(1-2):37-42

Two star-forming regions Cepheus A and W75N, were searched for the 4765-MHz OH maser emission using the multi-element radio linked interferometer network (MERLIN). The excited OH emission has an arc-like structure of 40 mas in Cep A and a linear structure of size 45 mas in W75N. We also found the 1720-MHz line in Cep A and Hutawarakorn [MNRAS 330 (2002) 349] reported the 1720-MHz emission in W75N. The 1720- and 4765-MHz OH spots coincided in space within 60 mas and in velocity within 0.3 km s^–1 in both targets implying that both maser transitions arise from the same region. According to the modelling by Gray [MNRAS 252 (1991) 30] the 1720/4765-MHz co-propagation requires a low density, warm environment. The masers lie at the edges of H II regions where such conditions are expected.  相似文献   

INCORPORATING INHERENT MAP ERROR INTO FLOOD-HAZARD ANALYSIS     

John D. Vitek  Donald G. Richards 《The Professional geographer》1978,30(2):168-173

Maps are an important source of data for planning and land use analysis of flood-prone areas. Map users with inadequate training are not aware that map errors can lead to ineffective decisions. Although inherent errors introduced by transformation, map construction, and symbolization are never identified on maps, they limit the effectiveness of maps as sources of data. Additional vertical and horizontal errors can be introduced during map use. Knowledge of the sources and amounts of such errors should result in more effective decisions regarding flood hazards.  相似文献   

Slipping strip analysis of reinforced earth     

D. J. Naylor  H. Richards 《国际地质力学数值与分析法杂志》1978,2(4):343-366

Reinforced earth in plane strain is idealized as a homogeneous material with the strips attached to the elastic soil matirx by a conceptual shear zone. A ‘no-slip’ finite element model is derived by assigning a large shear modulus to the shear zone. Relaxation of this modulus using a tangential stiffness algorithm in conjunction with a Mohr–Coulomb strip-slip criterion allows slipping to be simulated. The finite element formulation is validated and the finite element discretization assessed by comparisons against exact solutions for a simple test problem. An idealized reinforced earth wall example is used to demonstrate the feasibility of the method and to answer the question: ‘is slipping significant?’ The method is shown to be potentially useful, and slipping is shown to be significant.  相似文献   

Assessing market and non-market costs of freshwater flooding due to climate change in the community of Fredericton, Eastern Canada     

Van Lantz  Ryan Trenholm  Jeff Wilson  William Richards 《Climatic change》2012,110(1-2):347-372

There is a general consensus that climate change will increase the frequency and severity of freshwater flooding in many parts of the world. Communities prone to such flooding have struggled to understand the manner in which this will affect them (in both economic and social terms) and the appropriate way to adapt. In this study, we conduct a case-study investigation into the costs of freshwater flooding due to climate change along the Saint John River in Fredericton, NB, Canada. We develop a four-step framework that combines extreme event analysis, downscaled general circulation models, hydrologic analysis, and the contingent valuation method. Using this framework, together with primary data on a 2005 flooding event, we estimate market and non-market annual average flood damage under a number of climate and population scenarios. We find that non-market costs can represent up to 50% of total household costs of flooding events, and 23–42% of the total costs of flooding due to climate change, depending on the different climate and population scenarios considered. Incorporating such costs into flood adaptation planning may substantially increase support for active adaptation activities, especially in ‘worst case’ climate scenarios.  相似文献   

The concepts and development of a participatory regional integrated assessment tool   总被引：2，自引：1，他引：1  

I. P. Holman  M. D. A. Rounsevell  G. Cojacaru  S. Shackley  C. McLachlan  E. Audsley  P. M. Berry  C. Fontaine  P. A. Harrison  C. Henriques  M. Mokrech  R. J. Nicholls  K. R. Pearn  J. A. Richards 《Climatic change》2008,90(1-2):5-30

This paper provides an overview of the development of the ‘Regional Impact Simulator’ – a user friendly software tool designed to allow stakeholders to perform integrated assessments of the effects of climate and/or socio-economic change on the important sectors and resources of two contrasting UK regions. This includes the assessment of agriculture, water resources, biodiversity and coastal and river flooding. The tool arose from the need to further develop the methods applied in the earlier RegIS project, which was the first local to regional integrated assessment in the UK. The limitations of RegIS included very long run times, a limited number of simulations, incomplete linkages between models and no allowance for scenario uncertainty. Based upon the stakeholder needs identified within RegIS, a series of guiding principles were developed with Steering Committee stakeholders, which informed the concept of the ‘Regional Impact Simulator’ including functionality, appearance and complexity. An Integrated Assessment Methodology based upon the Drivers-Pressure-State-Impact-Response (DPSIR) framework facilitated the integration of multiple models, scenarios and datasets within the software interface. The development of the ‘Regional Impact Simulator’ provides a test-bed for further studies of stakeholder-led, regional, integrated assessment, and provides an opportunity to learn the many lessons in undertaking such studies.  相似文献   

Influence of Thermal Effects on the Wind Field Within the Urban Environment   总被引：1，自引：1，他引：0  

R. Dimitrova  Jean-François Sini  K. Richards  M. Schatzmann  M. Weeks  E. Perez García  C. Borrego 《Boundary-Layer Meteorology》2009,131(2):223-243

Micrometeorological conditions in the vicinity of urban buildings strongly influence the requirements that are imposed on building heating and cooling. The goal of the present study, carried out within the Advance Tools for Rational Energy Use towards Sustainability (ATREUS) European research network, is the evaluation of the wind field around buildings with walls heated by solar radiation. Two computational fluid dynamics (CFD) codes were validated against extensive wind-tunnel observations to assess the influence of thermal effects on model performance. The code selected from this validation was used to simulate the wind and temperature fields for a summer day in a specific region of the city of Lisbon. For this study, the meteorological data produced by a non-hydrostatic mesoscale atmospheric model (MM5) were used as boundary conditions for a CFD code, which was further applied to analyze the effects of local roughness elements and thermodynamic conditions on the air flow around buildings. The CFD modelling can also provide the inflow parameters for a Heating, Ventilation and Air Conditioning (HVAC) system, used to evaluate the building energy budgets and to predict performance of the air-conditioning system. The main finding of the present three-dimensional analyses is that thermal forcing associated with the heating of buildings can significantly modify local properties of the air flow.  相似文献   

Photometric redshift estimation using spectral connectivity analysis     

P. E. Freeman  J. A. Newman  A. B. Lee  J. W. Richards  C. M. Schafer 《Monthly notices of the Royal Astronomical Society》2009,398(4):2012-2021

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The 2dF–SDSS LRG and QSO survey: the QSO luminosity function at 0.4 < z < 2.6     

Scott M. Croom  Gordon T. Richards  Tom Shanks  Brian J. Boyle  Michael A. Strauss  Adam D. Myers  Robert C. Nichol  Kevin A. Pimbblet  Nicholas P. Ross  Donald P. Schneider  Robert G. Sharp  David A. Wake 《Monthly notices of the Royal Astronomical Society》2009,399(4):1755-1772

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