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71.
红壤坡地降雨产流产沙动态过程模拟试验研究 总被引:4,自引:0,他引:4
研究以浙江省兰溪水土保持综合试验站为研究基地,通过设定特定植被覆盖度(15%)不同坡度(8°、15°、20°)的径流试验小区,小区面积为2m2,采用野外人工模拟降雨试验方法,对降雨强度(0.8~2.9mm·min-1)范围内,红壤坡地产流和产沙随雨强和坡度的变化特性进行了模拟试验。通过32场模拟降雨试验数据的分析,得出结论如下:①产沙量与雨强呈指数函数关系,产流量与雨强呈幂函数关系,径流量与产沙量的相关性大于雨强与径流、雨强与产沙;②随坡度的增大,产流时刻提前,泥沙起动和产沙突增的雨强临界减小;③随坡度增大,累积产沙量的递增速率比累积径流量的递增速率要快;④场降雨侵蚀模数与雨强的相关性随着坡度的增大而增强。 相似文献
72.
This study evaluated the effectiveness of two application rates of a coral-derived surfacing material for both traffic and
nontraffic road conditions using simulated rainfall (110–120 mm h−1 for 30–90 min) on 0.75-m (wide) × 5.0-m (long) plots of similar slope (roughly 0.1 m m−1). The coral is a locally available material that has been applied to unpaved roads surfaces on Schoffield Barracks, Oahu,
Hawaii (USA), where this experiment was conducted. The simulations show that compared with a bare control plot, the coral-based
surface application rates of 80 and 160 kg m−2 (equivalent to only 10- and 20-mm thicknesses) reduced road sediment production by 75% and 95%, respectively, for nontraffic
conditions. However, after two passes of the research vehicle during wet conditions, sediment production rates for the two
coral treatments were not significantly different from those on the bare road plots. The overall effectiveness of the coral-derived
surfacing material is unsatisfactory, primarily because the on-road surface thickness associated with the application rates
tested was too small. These rates were selected to bracket those applied to training roads in the study area. Furthermore,
the composition of the coral-based material does not facilitate the development of a sealed, erosion-resistant surface. When
applied at the low rates tested, the coral material breaks down under normal traffic conditions, thereby losing its ability
to counter shearing forces exerted by overland flow on long hillslopes where erosion measures are most needed. These simulations,
combined with observations on roads in the study area, indicate that this material is not an appropriate road surfacing material
for the site—at least for the low application rates examined. These results are preliminary; extended testing of higher applications
rates at the hillslope scale under natural climate and traffic conditions is needed to better judge the effectiveness of this
material over time. 相似文献
73.
Cost/Benefit Considerations for Recent Saltcedar Control,Middle Pecos River,New Mexico 总被引:2,自引:1,他引:1
Major benefits were weighed against major costs associated with recent saltcedar control efforts along the Middle Pecos River,
New Mexico. The area of study was restricted to both sides of the channel and excluded tributaries along the 370 km between
Sumner and Brantley dams. Direct costs (helicopter spraying, dead tree removal, and revegetation) within the study area were
estimated to be $2.2 million but possibly rising to $6.4 million with the adoption of an aggressive revegetation program.
Indirect costs associated with increased potential for erosion and reservoir sedimentation would raise the costs due to increased
evaporation from more extensive shallows in the Pecos River as it enters Brantley Reservoir. Actions such as dredging are
unlikely given the conservative amount of sediment calculated (about 1% of the reservoir pool). The potential for water salvage
was identified as the only tangible benefit likely to be realized under the current control strategy. Estimates of evapotranspiration
(ET) using Landsat TM data allowed estimation of potential water salvage as the difference in ET before and after treatment,
an amount totaling 7.41 million m3 (6010 acre-ft) per year. Previous saltcedar control efforts of roughly the same magnitude found that salvaged ET recharged
groundwater and no additional flows were realized within the river. Thus, the value of this recharge is probably less than
the lowest value quoted for actual in-channel flow, and estimated to be < $63,000 per year. Though couched in terms of costs
and benefits, this paper is focused on what can be considered the key trade-off under a complete eradication strategy: water
salvage vs. erosion and sedimentation. It differs from previous efforts by focusing on evaluating the impacts of actual control
efforts within a specific system. Total costs (direct plus potential indirect) far outweighed benefits in this simple comparison
and are expected to be ongoing. Problems induced by saltcedar control may permanently reduce reservoir capacity and increase
reservoir evaporation rates, which could further deplete supplies on this water short system. These potential negative consequences
highlight that such costs and benefits need to be considered before initiating extensive saltcedar control programs on river
systems of the western United States. 相似文献
74.
From 2003 to 2006, a consortium of six European partners analysed the future of olive production systems on sloping land in the Mediterranean basin. Olive production on such land dates back to pre-Roman times, but the production systems (known by the acronym SMOPS, for "Sloping and Mountainous Olive Production Systems"), are under threat. Many are unsustainable environmentally (erosion hazard), socially (exodus of young people) or economically (high labour costs). The OLIVERO research project was possible thanks to a grant of euro1.5 million from the European Union, which gives out euro2.5 billion in subsidies annually for olive production. An extended survey conducted by the project in five sites in Portugal, Spain, Italy and Greece revealed the diversity and multifunctionality of SMOPS. Four main systems were identified as important for the future: traditional, organic, semi-intensive and intensive. The conceptual framework of OLIVERO involved six phases, ranging from the initial survey up to policy recommendations. In all phases there was intensive contact with stakeholders and institutions. End-users were identified at three levels: local, intermediate and regional, and national/international. This paper presents the highlights of the physical analysis of land and water resources, crop and land management, and economics and policies. Scenario studies gave insight into the possible future: some SMOPS will be gradually abandoned or transformed into nature conservation areas, others will exploit drip irrigation and follow the intensification patterns of agriculture in the valleys, and a third group will continue to be managed more extensively, perhaps augmenting their income with other activities (possibly off-farm) or turning to organic production systems. At the five international OLIVERO meetings held from 2003 to 2006, knowledge, experience and ideas on the future of olive production systems were intensively exchanged. A network was established for ongoing and future cooperation. Two end-user seminars were held in Matera (Italy) and Lisbon. Over 70 scientific papers have been published. 相似文献
75.
Francisco Taveira Pinto 《Journal of Coastal Conservation》2004,10(1):147-157
The practice of coastal zone management in Portugal is very recent. Key issues and considerations about natural shoreline
dynamics, main policy instruments, and lessons learned from the EU Demonstration Programmes on Integrated Coastal Zone Management
in Portugal will be outlined in this paper in an attempt to understand how the practice of ICZM and its prospects are. Coastal
zone management problems and their associated side effects, as well as national and international evolution patterns will
be drawn. Some means of achieving better coastal zone management practices and ways of addressing some of its forefront issues
are also identified. Special attention will go to erosion problems. The pressure induced by urban development and economic
activities on coastal areas is increasing. Poor sediment availability combined with years of neglected management and over-exploitation
of resources have had a negative impact, and there are many areas showing evidence of coastal erosion. There is a need to
improve policies and instruments of coastal planning and management. Coastal zone management plans are being developed for
the nine sectors of the continental Portuguese coast, providing a full analysis of coastal systems and a delimitation of uses
in relation to the carrying capacity of the shoreline. 相似文献
76.
R. Newsham P. S. Balson D. G. Tragheim A. M. Denniss 《Journal of Coastal Conservation》2002,8(1):49-54
The rapidly eroding cliffs and foreshore of the Holderness Coast represent one of the largest sources of sediment discharging
in the southern North Sea. For effective coastal management it is important to understand the sediment sources, transport
pathways and depositional sinks. The sediment budget is regarded as one of the key information needs for sustainable planning
and management. In order to quantify the sediment yield from recession of the Holderness Coast, digital photogrammetry has
been used, together with nearshore bathymetric survey data, to produce a single DTM for a length of over 52 km of coastline.
Other data including geological sections, sediment lithology, recession rates and the location of coastal defences have been
added to the DTM to create a GIS for the Holderness Coast. The GIS has been used to predict the volume and nature of the sediment
yield assuming that historical recession rates continue. The GIS can also be used to predict future yields using assumptions
of accelerated recession or the implications of arrested retreat due to construction of defences. 相似文献
77.
混凝土,砂浆和灰砂砖在模拟酸雨条件下的化学行为 总被引:4,自引:0,他引:4
用周期浸泡加速腐蚀试验法研究pH=3.5、5.6和pH为1.0时SO2-为0、0.06、0.1、0.2mol/L等6种模拟酸雨条件下混凝土、砂浆和灰砂砖的化学行为。研究表明:酸雨对材料的影响,主要是H+侵蚀引起的溶解腐蚀和SO42-侵蚀引起的膨胀腐蚀。 相似文献
78.
Raymond J. Burby 《Environmental management》1995,19(3):359-370
This article examines coercive and cooperative approaches to implementing state urban erosion and sedimentation pollution
control programs. State administrators report serious shortfalls in their ability to control sources of pollution, but comparison
of more and less successful programs provides evidence of what states can do to make programs more effective. Key ingredients
for a successful state effort include the use of coercion with both the private sector and local government, adequate staffing,
application of severe sanctions when violations of state standards are detected, and provision of technical assistance. Many
state programs lack one or more of those elements, which explains their inability to adequately control urban erosion and
sedimentation pollution. 相似文献
79.
Channel incision is a widespread phenomenon that results in stream and riparian habitat degradation. Fishes and physical habitat
variables were sampled at base flow from three incised stream channels and one reference stream in northwest Mississippi,
USA, to quantify incision effects on fish habitat and provide a basis for habitat rehabilitation planning and design. Incised
channels were sampled in spring and autumn; the reference channel was sampled only in the autumn. Incised channel habitat
quality was inferior to the reference channel despite the presence of structures designed to restore channel stability. Incised
channels had physical habitat diversity levels similar to a nonincised reference channel, but contained fewer types of habitat.
At base flow, incised channels were dominated by shallow, sandy habitats, moderate to high mean local Froude numbers, and
had relatively little organic debris in their beds. In contrast, the reference stream had greater mean water depth, contained
more woody debris, and provided more deep pool habitat. Fish assemblages in incised channels were composed of smaller fishes
representing fewer species relative to the reference site. Fish species richness was directly proportional to the mean local
Froude number, an indicator of the availability of pool habitat. 相似文献
80.
Steven D. Warren Victor E. Diersing Pamela J. Thompson William D. Goran 《Environmental management》1989,13(2):251-257
The universal soil loss equation (USLE) has been integrated with a geographic information system known as the geographical resources analysis support system (GRASS) to create a land classification system for use by military trainers and land managers to minimize the environmental impacts of military training activities. The USLE provides an estimate of current average annual sheet and rill erosion based upon factors representing climate, soil erodibility, topography, cover, and conservation support practices. The erosion estimate is compared to erosion tolerance values to produce an expression of the current erosion status. An index of inherent site erodibility is also achieved through manipulation of the USLE. Based on published soil surveys, satellite imagery, and ground-truth vegetation transects, data layers are created within GRASS for each of the component factors of the USLE. Appropriate mathematical operations are performed with the data layers, and color-coded maps are produced that represent the erosion status and erodibility index for each 50-m × 50-m area of soil surface. These maps aid military trainers and land managers in scheduling appropriate kinds and intensities of military training activities. 相似文献