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81.
Many nearshore restoration projects are currently underway at coastal locations where human influence and development have disrupted natural habitat and coastal ecological systems. The objectives of these projects in general are to restore the lost estuarine functions to the tidal marshland. Often these projects are conducted with little understanding of the potential effects of other nearby projects within the ecosystem, and similarly, it is easy to neglect the effect of the local project on the larger estuarine scale. In this paper, a modeling study is presented to evaluate the hydrodynamic responses of multiple restoration projects and their cumulative effect in the Snohomish River estuary in Washington, USA. The concept of absolute mean tidal transport is introduced and used to measure the cumulative effect of the proposed restoration projects on the estuarine hydrodynamics. The results show that the hydrodynamic responses due to multiple restoration projects are additive in the estuary, and the effect is nonlinear. The hydrodynamic response under restoration conditions depends on the size of the restoration area and the geometric configuration of the existing river channels. Within a complex braided estuary such as the Snohomish, the influence of a specific restoration project is not only experienced locally, but also found to significantly affect tidal transport in all distributary branches within the system. 相似文献
82.
Mark J. Brush 《Ecological modelling》2010,221(7):965-968
The development and application of ecosystem models in estuarine and coastal systems has grown exponentially over the past four decades. Models have become ensconced as major tools for both heuristic study of ecosystem structure and function as well as for informing management decisions, particularly with respect to cultural eutrophication. In recent years an ever-expanding toolbox of modeling approaches is being offered to complement traditional methods. This expansion of modeling in estuarine and coastal science was exemplified by four sessions devoted to modeling at the 2007 biennial conference of the Estuarine Research Federation in Providence, RI. We felt the time was right to propose a special session of Ecological Modelling to synthesize talks from these sessions to present the state of the art in coastal and estuarine modeling. The collection of papers contained in this special issue presents a diversity of traditional and novel modeling approaches, methods for assessing model validity and predictability, and the utility of models in management applications. We believe that together these papers provide an excellent overview of current approaches to modeling estuarine hydrodynamics, water quality, and ecosystem/food web dynamics, applications of complex and relatively simple modeling approaches, applications in both deep and shallow coastal systems, goals relevant for both heuristic and management applications, and perspectives based on traditional mechanistic model development as well as more recent alternative approaches. 相似文献
83.
Estimating the relevance of engineered carbonaceous nanoparticle facilitated transport of hydrophobic organic contaminants in porous media 总被引:1,自引:0,他引:1
Thilo Hofmann Frank von der Kammer 《Environmental pollution (Barking, Essex : 1987)》2009,157(4):1117-1126
Naturally occurring nanoparticles (NP) enhance the transport of hydrophobic organic contaminants (HOCs) in porous media. In addition, the debate on the environmental impact of engineered nanoparticles (ENP) has become increasingly important. HOC bind strongly to carbonaceous ENP. Thus, carbonaceous ENP may also act as carriers for contaminant transport and might be important when compared to existing transport processes. ENP bound transport is strongly linked to the sorption behavior, and other carbonaceous ENP-specific properties. In our analysis the HOC-ENP sorption mechanism, as well as ENP size and ENP residence time, was of major importance. Our results show that depending on ENP size, sorption kinetics and residence time in the system, the ENP bound transport can be estimated either as (1) negligible, (2) enhancing contaminant transport, or (3) should be assessed by reactive transport modeling. One major challenge to this field is the current lack of data for HOC-ENP desorption kinetics. 相似文献
84.
Wei Huilan Chen Haiyun Bai Jianming Zhu Ting 《Environment, Development and Sustainability》2009,11(4):725-734
A statistical model of community participation and investment in biodiversity protection projects was developed in order to
understand patterns in the effectiveness of conservation actions in forest-edge communities in Gansu, China. Extensive questionnaires
were used to validate the model. The effectiveness of biodiversity programs is strongly and positively influenced by the level
of public participation and investment. Higher education improves the use of resources associated with conservation, such
as reduced hunting, reduced use of forest products, and the use of fuels other than wood. Nevertheless, it will be important
to balance the implementation of conservation programs with the rights of communities to earn or gather a livelihood. The
CBI model will benefit from further development, but proves to be a valuable tool for evaluating the design and effectiveness
of biodiversity protection programs.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
85.
Laura K. Schmitt 《Environment, Development and Sustainability》2009,11(1):19-42
Soil erosion in many parts of the developing world poses a threat to rural livelihoods, to the sustainbility of the agricultural
sector, and to the environment. Most erosion prediction models are mechanistic and unsuited to quantify the severity of soil
erosion in a data-limited developing world context. The model developed in this paper for Negros Island, in the central Philippines,
is based on the Revised Universal Soil Loss Equation, but contains important innovations such as the movement of eroded soil
over the landscape, simulating deposition on lower slopes and in waterways. It also includes a term describing farmer strategies
to reduce soil erosion, which are typically ignored in erosion prediction models. A two-sample t-test found that model-predicted sediment loading values were not significantly different from field-measured sediment loading
values when corrected for watershed size (P = 0.857). The model predicts an annual loss of 2.7 million cubic meters of sediment to waterways such that by 2050 more than
416,000 ha of agricultural land will be rendered unproductive due to erosion. Farmer behavior conserves soil, but on the steepest
slopes soil conservation practices are not adequate to prevent erosion. Of two proposed strategies to control soil erosion
in the rural Philippines, the model suggests that a complete switch to tree crops would conserve more soil than universal
terrace adoption. However, even under these conservation scenarios, erosion threatens the areal extent of upland agriculture
on Negros, and hence the sustainability of the island’s food supply.
相似文献
Laura K. SchmittEmail: |
86.
Building future scenarios and uncovering persisting challenges of participatory forest management in Chilimo Forest, Central Ethiopia 总被引:1,自引:0,他引:1
Kassa H Campbell B Sandewall M Kebede M Tesfaye Y Dessie G Seifu A Tadesse M Garedew E Sandewall K 《Journal of environmental management》2009,90(2):1004-1013
We examined the changes in forest status and people's livelihoods through building future scenarios for Chilimo Forest in Central Ethiopia where participatory forest management (PFM) is being implemented. Participatory methods were employed to collect data, and a dynamic modeling technique was applied to explore trends over time. By integrating the more quantitative model outputs with qualitative insights, information on forests and livelihoods was summarized and returned to users, both to inform them and get feedback. A scenario of open access without PFM provides higher income benefits in the short term but not over the longer term, as compared to a scenario with PFM. Follow up meetings were organized with national decision makers to explore the possibility of new provisions in the national forest proclamation related to joint community-state ownership of forests. Project implementers must constantly work towards improving short term incentives from PFM, as these may be insufficient to garner support for PFM. Other necessary elements for PFM to succeed include: ensuring active participation of the communities in the process; and, clarifying and harmonizing the rules and regulations at different levels. 相似文献
87.
A hybrid approach using ISM and fuzzy TOPSIS for the selection of reverse logistics provider 总被引:5,自引:0,他引:5
Govindan Kannan Shaligram Pokharel P. Sasi Kumar 《Resources, Conservation and Recycling》2009,54(1):28-36
Return of used products is becoming an important logistics activity due to government legislation and increasing awareness among the people to protect the environment and reduce waste. For industries, the management of return flow usually requires a specialized infrastructure with special information systems for tracking and dedicated equipment for the processing of returns. Therefore, industries are turning to third-party reverse logistics providers (3PRLPs). In this study, a multi-criteria group decision-making (MCGDM) model in fuzzy environment is developed to guide the selection process of best 3PRLP. The interactions among the criteria are also analyzed before arriving at a decision for the selection of 3PRLP from among 15 alternatives. The analysis is done through Interpretive Structural Modeling (ISM) and fuzzy technique for order preference by similarity to ideal solution (TOPSIS). Finally the effectiveness of the model is illustrated using a case study on battery manufacturing industry in India. 相似文献
88.
Assessing Watershed-Scale, Long-Term Hydrologic Impacts of Land-Use Change Using a GIS-NPS Model 总被引:25,自引:0,他引:25
Land-use change, dominated by an increase in urban/impervious areas, has a significant impact on water resources. This includes
impacts on nonpoint source (NPS) pollution, which is the leading cause of degraded water quality in the United States. Traditional
hydrologic models focus on estimating peak discharges and NPS pollution from high-magnitude, episodic storms and successfully
address short-term, local-scale surface water management issues. However, runoff from small, low-frequency storms dominates
long-term hydrologic impacts, and existing hydrologic models are usually of limited use in assessing the long-term impacts
of land-use change. A long-term hydrologic impact assessment (L-THIA) model has been developed using the curve number (CN)
method. Long-term climatic records are used in combination with soils and land-use information to calculate average annual
runoff and NPS pollution at a watershed scale. The model is linked to a geographic information system (GIS) for convenient
generation and management of model input and output data, and advanced visualization of model results.
The L-THIA/NPS GIS model was applied to the Little Eagle Creek (LEC) watershed near Indianapolis, Indiana, USA. Historical
land-use scenarios for 1973, 1984, and 1991 were analyzed to track land-use change in the watershed and to assess impacts
on annual average runoff and NPS pollution from the watershed and its five subbasins. For the entire watershed between 1973
and 1991, an 18% increase in urban or impervious areas resulted in an estimated 80% increase in annual average runoff volume
and estimated increases of more than 50% in annual average loads for lead, copper, and zinc. Estimated nutrient (nitrogen
and phosphorus) loads decreased by 15% mainly because of loss of agricultural areas. The L-THIA/NPS GIS model is a powerful
tool for identifying environmentally sensitive areas in terms of NPS pollution potential and for evaluating alternative land
use scenarios for NPS pollution management. 相似文献
89.
The potential purification of an horizontal subsurface flow constructed wetlands (HSSFCW) treating greywater in a Moroccan primary school was investigated according to the monitoring of water quality parameters over a period of 100 days through two simultaneous stages: first, an internal three dimensional grid of sampling ports; secondly, an entry and exit. The calibration of the relaxed TIS concentration model based on tank in series hydraulic assumption with experimental data gave the frequency distribution profiles of K-rate constant values for the three parameters: BOD5, COD and TN, whose maximum values are respectively 50 m/yr, 70 m/yr, and 42 m/yr. The HSSFCW system has higher K-rate coefficient for all the three parameters at the bottom layer compared with the surface layer, with increasing K-rates over length. The analysis of bacteriological and chemical results has shown that the HSSFCW could not completely remove all pollutants (especially TN and TP), but it could be used successfully to upgrade the quality of greywater to an acceptable level. However, we predict that there will be an increase in removal efficiencies with time bearing in mind that the system is newly implemented. 相似文献
90.