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1.
A significant metamorphosis of channel form occurred on the lower Macdonald River between 1949 and 1955; width and width-depth ratio increased and depth, sinuosity and weighted mean per cent silt-clay in the channel perimeter decreased. The channel has remained unstable since 1955, exhibiting frequent variations in bed elevation and a recent period of minor channel contraction followed by slight enlargement. Since 1946 there has been an increase in summer and annual rainfall and an abrupt, upward shift of the annual series flood frequency curve. As a result an increased proportion of the total sediment load of the river is now being transported as bed-material load. The change in sediment load is a result of greater stream competence and the consequent reworking of sandy sediment temporarily stored within the channel as benches. The observed channel changes are a quasi-adjustment to the increased flood and bed-material load discharges.  相似文献   

2.
Since the early 1970s the Avoca River catchment has experienced a marked increase in all discharges, particularly high magnitude ones. This results from a change in the rainfall/runoff relationship, which is probably due to rising groundwater tables. Since 1973 the frequency of flooding in the lower Avoca, Loddon and Avon-Richardson catchments has increased markedly, placing pressure on downstream flood mitigation and irrigation works, as well as contributing to the degradation of environmentally sensitive wetlands. It also has the potential to exacerbate rising groundwater/salinity problems of the lower catchments. Human interference and changes in the rainfall regime are assessed to explain the nature of the apparent change in streamflows of the Avoca River catchment.  相似文献   

3.
Since 1955 the NSW Department of Water Resources has undertaken extensive river training works on many NSW streams. In the Hunter Valley alone over $23 million have been spent and more than 850 km of channel have been treated Published work suggests that river training works are usually undertaken in response to a pre-existing problem of river instability but can also induce adverse hydrogeomorphic effects. One of the treated streams, the Allyn River, had been supposedly degraded by the constructed works. It was alleged that vegetation clearing, channel excavations, alignment straightening and bank protection works had decreased roughness thus increasing velocity and flood frequency. As a result, what were thought to be relatively moderate floods were eroding the banks and destroying the floodplain. A critical evaluation of the available hydraulic, hydrologic and geomorphic data revealed that the river training works were a response to, rather than a cause of river instability.  相似文献   

4.
Sydney's water crisis has been attributed to long-term drought, a population growing at >50 000 a year, the early impacts of global warming and the demands of a 4.2 million population leading a water-thirsty lifestyle. In this paper the drought is linked with a return to a drought-dominated flow regime in eastern New South Wales. This began in 1991 and is associated with a shift from flood to drought domination that occurs every 20 to 50 years. Its impacts will be further exaggerated by global warming. The reduction of runoff into Sydney's reservoirs is due primarily to regime shift, resulting in the diminution of inflows to about 25% of their levels in the 42 years before 1991. Possible ways of managing these dwindling water resources include building more reservoirs, exploiting largely unknown sources of groundwater, constructing a desalination plant, harvesting rainwater in the city, recycling used urban water and reducing individual water use. Despite arguments against the first three of these options, a desalination plant is currently under construction and investigations of deep groundwater proceed (shelved 18th June, 2008). Given that sources of water are distant and located in areas where rainfall reductions have been significant, greater efforts should be made to use water already in the city (rainfall and recycled water). Water restrictions and better domestic management of water are also areas where great savings can be and have been made.  相似文献   

5.
Lake Albacutya is a well‐known intermittent lake in north‐western Victoria. The lake is near the termination of the Wimmera River. From time‐to‐time the lake fills and flow passes down Outlet Creek into Wyperfeld National Park. The wetlands associated with the lake have a high biodiversity value and are named in international treaties. This paper examines the hydrologic factors associated with lake filling and flow into Wyperfeld. The lake has filled approximately six times since 1880 and has partially filled on other occasions. Examination of rainfall data from 1875 at Horsham gave no indication of long term rainfall decline, and showed that rainfall at Horsham can be viewed as representative of rainfall in the Wimmera River catchment. However a double‐mass analysis showed that the relationship between the Wimmera River flow and rainfall has varied from 1890 to the present. Examination of data associated with six fillings of Lake Albacutya suggested that filling is a two‐year event requiring at least 550 GL of flow passing Horsham over the two years immediately associated with the flood. A simple model based on rainfall and this threshold reproduced observed characteristics of the data reasonably well. This suggested that the flooding frequency of Lake Albacutya has dropped from about one in 25 years in the natural state to a substantially lower frequency under current river conditions. The results also suggested that because of changes in the Wimmera River the last filling and flood into Wyperfeld in 1976 was far smaller than it would otherwise have been. This is consistent with field mapping of the flood in relation to River Red Gum (Eucalyptus camaldulensis Dehnh.) stands. Analysis of the health of these stands showed major dieback with the severity of this being roughly proportional to the distance from the 1976 flood boundaries. An examination of values associated with the lake and adjoining Wyperfeld National Park suggested that biodiversity and economic values are and will be compromised by the reduction in flooding. In particular, an internationally‐known provenance of Red Gum is at risk, and bird‐breeding opportunities have diminished.  相似文献   

6.
The flat topography of the Red River Valley reflects the morphology of underlying bedrock covered with late Quaternary glacial and glaciolacustrine sediments. The meandering Red River occupies a shallow stream‐cut valley that became incised into the Red River Valley plain following the final recession of glacial Lake Agassiz. Extreme flows carried by the river overtop the sides of the stream‐cut valley and spread laterally up to several tens of kilometres across the plain. An array of flood protection infrastructure has been constructed in the landscape to mitigate the flood hazard.  相似文献   

7.
Many empirically derived models of downstream changes in channel form are based on the concept of hydraulic geometry, whereby changes in channel morphological variables are related by a continuous power function to increasing discharge or its surrogate. However, changes in discharge throughout a drainage basin are normally concentrated at the junctions of stream channels. At junctions, the relationship between discharge and channel morphology is discontinuous. Some Lower Hunter Valley stream channels were surveyed upstream and downstream of tributary junctions. While significant regional downstream relationships were established, consistent trends at tributary junctions were not apparent from the data. It is possible that considerable scatter evident in ratios of change on either side of each junction was due to local within-site variability. In addition, the relative timing of discharge inputs and the nature of introduced sediment loads could be important in determining the magnitude and direction of channel change at tributary junctions. Interrelated changes in cross-sectional, profile and planform variables may be expected below junctions. The resultant channel morphology, in terms of these variables, might not be wholly determinate.  相似文献   

8.
This article examines the impact of economic restructuring on gender relations. It examines the implications of labour market change for households within a region, in this case the Greater Latrobe Valley, Victoria, Australia. The argument is that the unchanging gender structures of the labour market constrain the intentions and efforts of individuals within households to significantly alter household gender relations. The analysis considers how restructuring has reshaped the regional labour market since 1996, changing opportunities for both men’s and women’s employment. Despite these changes, the regional labour market continues to be underpinned by a ‘male breadwinner’ gender regime and significant occupational and industrial gender segregation. Drawing on four vignettes, the analysis shows that the impetus towards greater gender equality in the household is constrained by a stagnant and stable labour market gender regime.  相似文献   

9.
Dealing with differing and sometimes conflicting criteria for priority‐setting is an essential part of sustainable natural resource management. However, all too often, these ethical and political considerations are neglected within a planning regime based upon apparently ‘objective’ biophysical assessment techniques. Input into associated decision‐making processes is also frequently restricted to a narrow range of ‘stakes’ based upon historical and geographic circumstances. This paper reports on the findings of interviews and discussion groups in the Hunter Valley, New South Wales, which aimed to canvass the diversity of perceptions of distributive and procedural justice in river rehabilitation. A range of biophysical and social criteria for setting priorities in rehabilitation work was identified. Participants also had differing ideas on the composition of decision‐making bodies and on decision‐making processes. The key implications of these findings are that sustainable river management policy needs to openly address differing conceptions of justice and that rehabilitation practice should be holistic, transdisciplinary and concerned with both outcome and process.  相似文献   

10.
黄河长期泛淮使淮河以北地区沧桑巨变。它淤平了河湖 ,吞没了良田、村庄、城市和道路 ,在很大程度上改变了当地的自然地理环境。更为严重的是 ,它给淮北地区社会经济的发展带来了极大的负面影响 ,使原本发达的经济区变为经济相对落后区。  相似文献   

11.
ABSTRACT Water is a resource that both unites and divides people in the Upper Hunter Valley of New South Wales, where many communities are facing the prospect of large‐scale open‐cut coalmining developments on productive mixed use land, or already live in proximity to mines and power stations. This article analyses conflicts over a proposed coal mine at Bickham in the Upper Hunter Valley, by contrasting the various protagonists' discourses of water scarcity, supply, and connectivity. It examines the ways in which the terms of opposition are narrowed to the arena of state and industry supported science and economic development, marginalising other cultural values and environmental ethics that are integral to opponents' discourses. Opponents have achieved some measure of success through contestation of the uncertain science of hydrological modelling, bolstered by the context of drought and increasing public acceptance of climate change science.  相似文献   

12.
The Illawarra Region some 80 kilometres south of Sydney is characterised by a prominent coastal escarpment that rises to 700 m within 12 km of the coast and forms a locus for frequent, high intensity rainfall events. One of the most recent recorded events occurred on 17 August 1998 with rainfall intensities at several pluviometers exceeding 120 mm hr‐1 over a duration of one hour, with up to 249 mm falling in 3.5 hours during the main storm burst. Detailed pluviometer data indicate that the storm was non‐stationary and moved down catchment producing a widespread zone of 120 mm hr‐1 intensity rainfall over a 30 minute duration across mid‐lower catchment areas after similar intensity but longer duration rainfall in catchment headwaters. Slope‐area reconstructions of peak discharge indicate that small catchments on the escarpment within the zone of maximum intensity experienced close to 100% rainfall‐runoff relationships, with peak discharges correlated to short duration (<1 hr) peak rainfall intensities. Widespread erosion occurred particularly where urban development had encroached on natural water courses. Debris/hyperconcentrated flows originating from both anthropogenic and natural sediment sources caused damage to urban areas. This paper provides an overview of the spatial and temporal characteristics of the 17 August 1998 storm, the hydrologic and geomorphic response of the streams, and the nature of damage to urban areas. It reassesses the frequency of recent high‐magnitude rainfall/flood events in the region, discussing the relationships between rainfall intensities, estimates of flood magnitudes and stormwater channel capacities.  相似文献   

13.
Large-scale river training works have been carried out in the Hunter valley since 1955 in response to flood-driven channel changes. Vegetation was planted on in-channel benches induced by river training works to consolidate the deposits and to increase channel boundary roughness. Exotic species of vegetation such as willows and poplars were previously used. In 1983, ten trial sites were planted with various species of native vegetation. Survival rates were evaluated in 1987 and 1997. The most successful species planted was Eucalyptus camaldulensis with an overall survival rate of 77 per cent in 1997. The Acacia species were found to be short-lived, exhibiting a significant decline in survival rates between 1987 and 1997. Survival rates for most species were higher on sand-bed than on gravel-bed sites. This difference may be attributed to better drainage on benches at the sand-bed sites. Investigations of flood disturbance showed that between 1983 and 1997 the sites were flooded between four and 13 times. The survival rates of Grevillea robusta and Eucalyptus melliodora trees were negatively correlated with the total number of recorded floods at each site. Poor natural regeneration of planted species is attributed to a combination of periodic flooding, intensive weed growth, low light intensities at ground level and grazing disturbance. These trials were not well designed for statistical analysis but provide valuable long-term information on the suitability of various species for planting in riparian rehabilitation programs. Such information is of relevance not only to river and catchment management authorities, but also to community groups.  相似文献   

14.
This study assesses human impact on the landscape around Cobrico, a volcanic crater lake in dairying country in south-western Victoria. It compares the last 150 years of impact of European settlement against approximately the previous 1500 years of prehistoric occupation and land use. Focus is on vegetation dynamics, erosion, productivity changes and the fire regime. Since European settlement there has been woodland clearance and recovery, the introduction of many plant and animal species and a significant increase in the intensity in the fire regime. While many direct linkages are apparent between environmental variables some operate over significant time lags. Fire has played a major role in vegetation dynamics and has favoured open ground taxa at the expense of Eucalyptus and Melaleuca. While major fires do not always lead to erosion in the catchment it is clear that some changes in the chemistry of erosion products have resulted, with potassium and iron showing increases in the historic period.  相似文献   

15.
This study tests a model for the impact that Ceausescu's pro-natalist policies had on the Romanian fertility rate between 1967 and 1989. Using time-series analysis the authors' findings show that the Ceausescu regime continually struggled with the Romanian population to increase the national birthrate. As a result the regime's policies, there was a significant increase in overall fertility between 1967 and 1989, when the Ceausescu regime was overthrown. Reasons are offered as to why Romania pursued such policies and was able to make them work, while other Eastern and Central European regimes proved to be less able to sustain drives to increase national fertility. This article also presents a model of what has happened to the Romanian fertility rate since 1989, showing that there has been a significant decline in fertility in the post-Communist period.  相似文献   

16.
This paper examines the emergence of a sharply delineated socioeconomic and sociocultural fault‐line between Cessnock's former coal towns and the immediately adjacent Hunter Valley Wine Country, centred on Pokolbin. We provide evidence that divergent culturally‐related class identities act as mutually reinforcing constraints on reciprocity between job‐deficit former coal towns and the job‐surplus wine country. We relate this to a consideration of time‐space dimensions in the interdependencies between the class and place identities of Cessnock and Pokolbin. These identities have been influenced by metropolitan colonisation, with the markedly differentiated absorption of these two locales into the enlarged metropolitan population‐work‐welfare‐housing‐leisure agglomeration. Further, we propose that the former coal towns and the wine country can both be seen as place‐specific representations of wider class‐related changes within Australian society. Our interpretations are founded on three current research directions: first, the role of culture as a critical intervening variable in class identities and actions; second, the current flux in class formations, most notably the loss of self‐identity and solidarity in the working class and the emergence of a new middle‐class sector dedicated to self‐realisation and self‐fulfilment; and third, recognition of class formation as a geographical process.  相似文献   

17.
Coal seam gas and other unconventional gas industries have often struggled to develop a social licence to operate in surrounding communities, frequently resulting in the emergence of broad opposition coalitions and legal challenges. In this article, the authors explore the relational aspects of coal seam gas's space‐based setting with reference to Keith Halfacree's three‐fold model of rural space. Applying this model to coal seam gas development in New South Wales' Hunter Valley, we argue that it is only by understanding the so‐called total space that efforts can be undertaken to promote the more inclusive stakeholder collaboration, which is a prerequisite for achieving shared value for industry and society.  相似文献   

18.
Abstract: Recent years have witnessed increased geographical interest in the changing nature of forestry in the UK. Critical attention has been given to a transition from a previously dominant regime of industrial forestry, primarily concerned with the mass production of timber, to a post‐industrial regime, within which timber production sits alongside a broader range of social, economic and environmental objectives. Investigations of this transition, however, have been largely restricted to analyses of national policy discourse, with relatively little attention given to the implementation of post‐industrial forestry in regional and local spaces. In this paper, we argue that the emergence of this new forestry regime has been associated with a great deal of spatial complexity. Drawing on findings from recent research in the southern valleys of Wales, we highlight the complex geographies bound up with the implementation of national regimes of forestry in the UK, and the significant roles played by the local socio‐natural context in facilitating and resisting the implementation of new forestry regimes in particular spaces.  相似文献   

19.
The dramatic topography of the Dordogne Valley region of southwestern France has long been recognized as an influence on prehistoric human settlement and subsistence patterns. Previous research on late Pleistocene settlement patterns in this region implies that, as cold-adapted higher-ranked resources became scarce in the lowlands, site location in the Dordogne and adjacent river valleys should shift towards higher-elevation areas during the period from 18,000 to 6500 years BP. This study employs a GIS-based analysis to evaluate the changing settlement patterns in the Dordogne region at this time. While no significant changes in elevation were found during this period, site elevation variance does appear to increase significantly between the Magdalenian and the Sauveterrian. Explanations for this finding are explored using zooarchaeological data from Moulin du Roc, one of the sites in the data set. Results suggest that the Magdalenian period in the Dordogne may not have been as resource-rich as is often assumed.  相似文献   

20.
金、元以后永定河水害急剧增多,由北京的母亲河变成了常常威胁京城安全的害河。金代以来各朝都十分重视对永定河的治理,元明清三朝更是把修筑永定河的堤防作为京畿事务中的重大问题。历史上永定河的大规模筑堤为京城减少了洪水之虞,但同时也带来了包括北京水环境在内的一系列地理环境的变化。本文追溯永定河筑堤后北京地区水环境变迁以及下游地貌改变的重要史实,阐述筑堤工程对于流域整体环境的深远影响,以期引起人们对历史上一些重大水利工程的环境效应的反思。  相似文献   

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