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571.
In the light of global warming and sea level rise there are many coastal beaches that suffer from erosion. Beach nourishment has become a common practice to maintain the sediment balance on a shore-face. In this paper, a three-dimensional numerical model for evaluating long-term impact of beach nourishment projects has been developed. The model addresses the longstanding complex issue of coastal morphology and sediment grain size distribution from an unconventional angle, which exploits the strong links between grain size distribution and the prevailing transport direction of each sediment constituent under ‘average’ wave and storm action. The present model predicts the redistribution of nourished sediment according to the subtle clues implied by equilibrium distribution curves and latest coastal wave transformation theories. After verification against recent field observations in Terschelling, The Netherlands, the model was used to predict long-term effects of different beach nourishment strategies. It was found that: (a) given the source sediment available in Terschelling the tactics of large volume and less frequent implementation are better than otherwise; and (b) from a pure engineering point of view, waterline nourishment outperforms offshore trough nourishment.The model offers an additional tool for coastal engineers to evaluate the feasibility, effectiveness and the optimization of dumping locations for beach nourishment projects. It is also a useful tool for stratigraphic modelling of shallow-marine sedimentation in conjunction with sea level changes. 相似文献
572.
Binbin Lu Chris Brunsdon Martin Charlton Paul Harris 《International journal of geographical information science》2017,31(5):982-998
Geographically weighted regression (GWR) is an important local technique to model spatially varying relationships. A single distance metric (Euclidean or non-Euclidean) is generally used to calibrate a standard GWR model. However, variations in spatial relationships within a GWR model might also vary in intensity with respect to location and direction. This assertion has led to extensions of the standard GWR model to mixed (or semiparametric) GWR and to flexible bandwidth GWR models. In this article, we present a strongly related extension in fitting a GWR model with parameter-specific distance metrics (PSDM GWR). As with mixed and flexible bandwidth GWR models, a back-fitting algorithm is used for the calibration of the PSDM GWR model. The value of this new GWR model is demonstrated using a London house price data set as a case study. The results indicate that the PSDM GWR model can clearly improve the model calibration in terms of both goodness of fit and prediction accuracy, in contrast to the model fits when only one metric is singly used. Moreover, the PSDM GWR model provides added value in understanding how a regression model’s relationships may vary at different spatial scales, according to the bandwidths and distance metrics selected. PSDM GWR deals with spatial heterogeneities in data relationships in a general way, although questions remain on its model diagnostics, distance metric specification, and computational efficiency, providing options for further research. 相似文献
573.
V.Chris Lakhan 《Ocean & Coastal Management》1994,22(3)
Planning and development experiences in Guyana's coastal zone have evolved from being individualistic, ill-conceived, uncoordinated and theoretically unsound to become more systematic, integrated and practical. After presenting an overview of the efforts made by the early European settlers to make the below sea level, and flood prone coastal zone habitable and cultivable, the paper analyses the planning experiences in the post-emancipation and post Second World War periods. Analysis of the Black Bush Polder project reveals both the positive and negative experiences of policy and planning strategies.Although planners have acquired the experiential knowledge that water control is necessary for coastal development and they have attempted to develop scientific plans, the paper, nevertheless, claims that coastal residents are becoming disenchanted with the escalating and aggravating water control problems. With the planning experience considered as being neither disappointing nor successful the paper concludes that 90% of the country's population will continue living in the coastal zone given rehabilitation and modernization of the water control infrastructure, and implementation of better policy, planning and management strategies. 相似文献
574.
We implement a geographic information system (GIS) to map surficial geologic habitats (SGH) with varying scales at Nehalem Bank, Oregon, USA. Geologic interpretation was first used to produce a regional-scale SGH map of mega habitats. Local-scale algorithmic classification techniques were then implemented where data density and richness permitted the mapping of meso (10 m-1 km) macro scale (1-10 m) habitat features. We use a ranked-(data) density approach to assess the distribution and quality of input data for the regional SGH map. We then apply a virtual reference dataset and error matrix technique to assess the thematic accuracy of local-scale maps. 相似文献
575.
Finding the right jobs-housing balance has long been an important concern for urban planners. More recently, attention has turned to jobs-housing fit – the extent to which housing price is well matched to local job quality. Prior analyses have been constrained by a lack of local data on job quality, making it difficult to identify the geography and scale of the problem. We introduce a new methodology for calculating the low-wage jobs-housing fit at both a jurisdiction and neighborhood scale that was designed in collaboration with affordable housing advocates and has been directly applied in urban planning and affordable housing policy efforts. Low-wage fit is particularly important because of ongoing difficulties with affordable housing provision and the disproportionate benefits of reducing transportation costs for low-income earners. We use the calculated metric at both a city and neighborhood scale to identify what can be learned from a low-wage jobs-housing fit metric that is not evident in traditional measures of jobs-housing balance. In contrast to jobs-housing balance, the low-wage fit analysis clearly highlights those jurisdictions and neighborhoods where there is a substantial shortage of affordable housing in relation to the number of low-wage jobs. Because of the geographic coverage of the data sources used, the results can be widely applied across the United States by affordable housing advocates, land-use planners, and policy makers. 相似文献
576.
Binbin Lu Martin Charlton Chris Brunsdon Paul Harris 《International journal of geographical information science》2016,30(2):351-368
In this study, the geographically weighted regression (GWR) model is adapted to benefit from a broad range of distance metrics, where it is demonstrated that a well-chosen distance metric can improve model performance. How to choose or define such a distance metric is key, and in this respect, a ‘Minkowski approach’ is proposed that enables the selection of an optimum distance metric for a given GWR model. This approach is evaluated within a simulation experiment consisting of three scenarios. The results are twofold: (1) a well-chosen distance metric can significantly improve the predictive accuracy of a GWR model; and (2) the approach allows a good approximation of the underlying ‘optimal distance metric’, which is considered useful when the ‘true’ distance metric is unknown. 相似文献
577.
Numerical simulation of the paleohydrology of glacial Lake Oshkosh, eastern Wisconsin, USA 总被引:1,自引:0,他引:1
James A. Clark Kevin M. Befus Peter W. Stewart Chris T. Gregory 《Quaternary Research》2008,69(1):117-129
Proglacial lakes, formed during retreat of the Laurentide ice sheet, evolved quickly as outlets became ice-free and the earth deformed through glacial isostatic adjustment. With high-resolution digital elevation models (DEMs) and GIS methods, it is possible to reconstruct the evolution of surface hydrology. When a DEM deforms through time as predicted by our model of viscoelastic earth relaxation, the entire surface hydrologic system with its lakes, outlets, shorelines and rivers also evolves without requiring assumptions of outlet position. The method is applied to proglacial Lake Oshkosh in Wisconsin (13,600 to 12,900 cal yr BP). Comparison of predicted to observed shoreline tilt indicates the ice sheet was about 400 m thick over the Great Lakes region. During ice sheet recession, each of the five outlets are predicted to uplift more than 100 m and then subside approximately 30 m. At its maximum extent, Lake Oshkosh covered 6600 km2 with a volume of 111 km3. Using the Hydrologic Engineering Center-River Analysis System model, flow velocities during glacial outburst floods up to 9 m/s and peak discharge of 140,000 m3/s are predicted, which could drain 33.5 km3 of lake water in 10 days and transport boulders up to 3 m in diameter. 相似文献
578.
In this paper the development of a large-scale gravitational deformation involving the eastern lateral moraine of the Athabasca
Glacier in Jasper National Park, Alberta, Canada, is described. Interpretation and analysis of sequential aerial photographs
indicates that a 540-m-wide segment of the eastern lateral moraine began to deform in the early 1950s; however, significant
movement only began in the late 1960s. Since then, the moraine has undergone progressive gravitational deformation leading
to a network of fractures, bulging, and the development of a large gap in the moraine crest. Geographic information system
analysis of topographic changes between 1967 and 2006 indicates that the displaced volume of the moraine is approximately
9.0 × 105 m3. In the last 39 years, the moraine crest has displaced 55 m (1.4 m yr−1) down towards the glacier. The development of slope instability is linked to a combination of debuttressing from recent glacier
recession, deformation of the moraine, as well as the movement of a large, mobile, debris-mantled slope impinging the upslope
margin of the lateral moraine. This case study illustrates the importance of glacial conditioning and local geomorphological
factors in creating conditions for large-scale moraine instability in recently deglacierized alpine basins. 相似文献
579.
Anette Büchl Chris J Hawkesworth K Vala Ragnarsdottir David R Brown 《Geochemical transactions》2008,9(1):11
Cu and Zn have naturally occurring non radioactive isotopes, and their isotopic systematics in a biological context are poorly
understood. In this study we used double focussing mass spectroscopy to determine the ratios for these isotopes for the first
time in mouse brain. The Cu and Zn isotope ratios for four strains of wild-type mice showed no significant difference (δ65Cu -0.12 to -0.78 permil; δ66Zn -0.23 to -0.48 permil). We also looked at how altering the expression of a single copper binding protein, the prion protein
(PrP), alters the isotope ratios. Both knockout and overexpression of PrP had no significant effect on the ratio of Cu isotopes.
Mice brains expressing mutant PrP lacking the known metal binding domain have δ65Cu isotope values of on average 0.57 permil higher than wild-type mouse brains. This implies that loss of the copper binding
domain of PrP increases the level of 65Cu in the brain. δ66Zn isotope values of the transgenic mouse brains are enriched for 66Zn to the wild-type mouse brains. Here we show for the first time that the expression of a single protein can alter the partitioning
of metal isotopes in mouse brains. The results imply that the expression of the prion protein can alter cellular Cu isotope
content. 相似文献
580.
Liviu?Mihai?Irimia Cristian?Valeriu?PatricheEmail author Hervé?Quenol Lucian?Sf?c? Chris?Foss 《Theoretical and Applied Climatology》2018,131(3-4):1069-1081
Climate change is causing important shifts in the suitability of regions for wine production. Fine scale mapping of these shifts helps us to understand the evolution of vineyard climates, and to find solutions through viticultural adaptation. The aim of this study is to identify and map the structural and spatial shifts that occurred in the climatic suitability for wine production of the Cotnari wine growing region (Romania) between 1961 and 2013. Discontinuities in trends of temperature were identified, and the averages and trends of 13 climatic parameters for the 1961 to 1980 and 1981 to 2013 time periods were analysed. Using the averages of these climatic parameters, climate suitability for wine production was calculated at a resolution of 30 m and mapped for each time period, and the changes analysed. The results indicate shifts in the area’s historic climatic profile, due to an increase of heliothermal resources and precipitation constancy. The area’s climate suitability for wine production was modified by the loss of climate suitability for white table wines, sparkling wines and wine for distillates; shifts in suitability to higher altitudes by about 67 m, and a 48.6% decrease in the area suitable for quality white wines; and the occurrence of suitable climates for red wines at lower altitudes. The study showed that climate suitability for wine production has a multi-level spatial structure, with classes requiring a cooler climate being located at a higher altitude than those requiring a warmer climate. Climate change has therefore resulted in the shift of climate suitability classes for wine production to higher altitudes. 相似文献