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81.
The Neebing-McIntyre floodway in Thunder Bay, Ontario, Canada, has been constructed with a relatively straight and uniform trapezoidal channel, compared with the prechannelized sinuous reaches of the Neebing and the McIntyre rivers. The flow regime of the floodway also contrasts significantly with the prechannelized regime, because of the combination of discharges from these rivers into a new channel and the regulation of flows by a diversion structure. The maximum channel capacity of the floodway is about 284 m3 s–1 (175-year regional flood), compared with about 40 m3 s–1 and 60 m3 s–1, respectively, for the Neebing and the McIntyre. According to regime theories, the construction of a straight and trapezoidal channel has upset the equilibrium of the stream system and therefore should lead to some accelerated erosion and sedimentation processes in the new channel immediately after construction. Erosion potential is particularly high during higher discharge events, when flow velocities are expected to be greater than the prechannelized velocities of the Neebing and the McIntyre. The overall sediment yield of the watershed is low (71t km–2 yr–1), compared with other documented watersheds of North America, but the rates of deposition in the floodway are relatively high, mainly due to the backwater effect of Lake Superior. Unless maintained by constant channel work, the floodway will tend to fill up with sediment, until a postconstructional equilibrium is reestablished. 相似文献
82.
Food habits of white-tailed deer (Odocoileus virginianus) were examined from January to November 1984 via fecal-pellet analysis at Valley Forge National Historical Park (VFNHP), which represents an island habitat for deer surrounded by extensive urbanization, in southeastern Pennsylvania. In addition, use of fields by deer was compared to food habits. Herbaceous vegetation (forbs, leaves of woody plants, and conifer needles) was the predominant food type in all seasons except fall. Acorns and graminoids (grasses and sedges) were important food resources in fall and spring, respectively. Use of woody browse (twigs) was similar among seasons. Field use was relatively high during fall, winter without snow cover (<20 cm), and spring when food resources in fields were readily available. In contrast, use of fields was lowest in summer when preferred woodland foods were available and in winter with snow cover when food in fields was not readily accessible. Patterns of food-type use by deer at VFNHP indicate the year-round importance of nonwoody foods and field habitats to deer populations on public lands such as national parks in the northeastern United States. 相似文献
83.
In this article, we suggest that a landscape approach might be useful in evaluating the effects of cumulative impacts on freshwater wetlands. The reason for using this approach is that most watersheds contain more than one wetland, and effects on water quality depend on the types of wetlands and their position in the landscape. Riparian areas that border uplands appear to be important sites for nitrogen processing and retention of large sediment particles. Fine particles associated with high concentrations of phosphorus are retained in downstream wetlands, where flow rates are slowed and where the surface water passes through plant litter. Riverine systems also may play an important role in processing nutrients, primarily during flooding events. Lacustrine wetlands appear to have the least impact on water quality, due to the small ratio of vegetated surface to open water. Examples are given of changes that occurred when the hydrology of a Maryland floodplain was altered. 相似文献
84.
This article presents a case history of hazardous waste landfill remediation activities at General Electric's Silicone's (GES's) manufacturing facility in Waterford, New York. The approach presented describes the development of the remedial program and its subsequent modification in achieving regulatory compliance goals, providing environmental benefit, and satisfying business considerations and budgetary constraints. 相似文献
85.
86.
Brian G. Field 《Journal of Environmental Planning and Management》1984,27(2):68-78
This paper focuses on the development plan activities of the London Boroughs and simply seeks to explain the relatively limited progress that has been made in the preparation and adoption of statutory local plans, by showing how production was constrained as local planners were caught up in the shifting ground of contemporary planning theory. The author suggests that uncertainty about the acceptable scope and content of local plans, at a time when planners were being encouraged to extend the emphasis of their work beyond the purely physical, led to serious problems as planners began to experiment with new approaches to local planning but failed to appreciate the operational implications of each approach. 相似文献
87.
This paper describes the primary energy resources of New Zealand and their relative importance. It describes the principal legislation that provides environmental protection and public participation with which State and private agencies are bound to comply. The paper then discusses air pollution in further detail and cites three examples where there is cause for concern. By international standards, air pollution is not a serious problem in New Zealand and so the economic consequences have received little attention Two simple examples are cited. A map showing the main centers and the location of facilities referred to in the text is included 相似文献
88.
In recent years, an increasing number of regulations and methodologies have begun to utilize total organic carbon (TOC) analysis for monitoring microbial contamination and/or disinfectant byproduct (DBP) precursors. This paper highlights some analytical differences and similarities between the two widely used TOC oxidation techniques: UV persulfate and high temperature combustion (HTC). Previous papers have come to different and sometimes contradictory conclusions on this subject. However, these studies either compared instruments with significantly different flow paths or TOC systems from different eras. Unlike previous studies, this paper compares two modern TOC analyzers with nearly identical flow paths for sample recovery, detection limits, and analysis of real world samples. On average, both persulfate and HTC oxidation yielded good recoveries for 10 hard to oxidize compounds and potable water samples from 5 different locations across the USA. In general, persulfate yielded more precise results because of its lower background response relative to sample response while HTC gave slightly higher results (roughly 2% to 3%) for surface water samples. 相似文献
89.
Brian M. Reich 《Journal of the American Water Resources Association》1971,7(6):1153-1171
A study is presented of the months in which the instantaneous annual maximum discharges from 66 watersheds occurred. The 2,052 flood values were measured on areas ranging from 2.4 through 214 square miles. The longest record was 60 years; the three shortest were 20. Pictorial results show both the number of floods for each month and individual discharges relative to the mean flood. A parameter which is weighted in this manner accounts for both the incidence and the magnitude of floods. Peculiarities of flood-timing charts, based on this parameter, are discussed with respect to watershed size, soils, geology, and land use. After anomolous watersheds had been assigned to special categories, flood-timing charts from most records exhibit a regional dichotomy dividing eastern from western Pennsylvania. 相似文献
90.
ELLISON BA 《Environmental management》1999,23(4):429-439
/ This paper explores the new politics of western water policy through an examination of the Animas-La Plata water project and implementation of the Endangered Species Act. It is suggested that the focus of western water programming has shifted from the source of distributed funds, the United States Congress, to the agencies originally created to deliver federal benefits because funding for new project construction has not been forthcoming. Under this new system, members of Congress continue to excite their constituents with promises of money for new project starts, while the administrative agencies perform the myriad duties needed to keep these projects alive. The result is that political objectives have replaced operational/management objectives in administrative processes. In this case, the author demonstrates how resource managers in the Bureau of Reclamation manipulated hydrological analysis to control administrative process, why their manipulation was unfair, and perhaps illegal, and why biologists from the US Fish and Wildlife Service accepted the analysis. While ostensibly protecting all interests, the result is that none of the objectives of federal water programming are achieved. KEY WORDS: Environmental management; Administrative politics; Water policy; Endangered Species Act; Animas-La Plata, Bureau of Reclamation 相似文献