Use of Constructed Wetlands for Urban Stream Restoration: A Critical Analysis

/ Investigation of a delta marsh restoration project proposed forthe Don River in Toronto, Ontario, underlines several concerns aboutconstructed wetland projects designed for water quality improvement andaquatic habitat enhancement. The Don is a highly urbanized river that hasundergone significant physiographic modifications and continually receives acomplex mixture of conventional, metallic, and organic contaminants frommultiple point and nonpoint sources. Rather than providing permanent removalof urban contaminants, wetland processes offer a limited capacity fortemporary storage of contaminant inputs, and potential reactions may actuallyproduce more toxic and/or bioavailable forms of some chemicals. Theseprocesses tend to result in the concentration of watershed contaminants inwetland vegetation and sediments. As the restored marsh would be availablefor spawning and feeding by aquatic fauna, the potential exists for chemicalbioconcentration and biomagnification through the aquatic community.Accordingly, wetland systems are not suited to the dual purposes of waterquality improvement and aquatic habitat enhancement. Upstream controls,including source reduction of contaminant inputs, are recommended asessential components of all constructed wetland projects.KEY WORDS: Constructed wetlands; Water quality; Ecological restoration;Don River     

Improving the Urban Stream Restoration Effort: Identifying Critical Form and Processes Relationships

Stream restoration projects are often based on morphological form or stream type and, as a result, there needs to be a clear tie established between form and function of the stream. An examination of the literature identifies numerous relationships in naturally forming streams that link morphologic form and stream processes. Urban stream restoration designs often work around infrastructure and incorporate bank stabilization and grade control structures. Because of these imposed constraints and highly altered hydrologic and sediment discharge regimens, the design of urban channel projects is rather unclear. In this paper, we examine the state of the art in relationships between form and processes, the strengths and weaknesses of these existing relationships, and the current lack of understanding in applying these relationships in the urban environment. In particular, we identify relationships that are critical to urban stream restoration projects and provide recommendations for future research into how this information can be used to improve urban stream restoration design. It is also suggested that improving the success of urban restoration projects requires further investigation into incorporating process-based methodologies, which can potentially reduce ambiguity in the design and the necessity of using an abundant amount of in-stream structures.     

Urban Stream Rehabilitation: A Design and Construction Case Study

/ This paper describes the fundamental design features, and construction methods and sequence, of a rehabilitation project on a small suburban creek in Moscow, Idaho, USA. A meandering channel pattern was reestablished for approximately 280 m of straightened, dredged channel, a new floodplain was excavated, and the new riparian zone was replanted. The new stream channel was sized to accommodate an estimated natural bankfull discharge ( approximately 5.6 cms), and floodplain design attempted to match the conveyance of the old enlarged channel (14-20 cms). The project was coordinated by a local nonprofit environmental organization, and the design and construction were tailored to donated materials and a largely volunteer labor force. A high-magnitude flood event (ca. 50-year recurrence interval) six months after construction had no significant impact on the newly constructed channel and revetments, but underscored the need for important detailing of the structures. The use of volunteer labor, while entailing certain benefits, complicates project planning and construction. The most general lesson learned from this project is that sponsoring agencies and clients need to be informed of the many steps and sequencing of properly constructed, complex stream rehabilitation projects as well as the high time and cost requirements for these tasks. KEY WORDS: Stream corridor restoration; Channel design; Streambank revetments     

Trout Population Responses to Restoration of Stream Flows

There are numerous demands for the limited water supplies in the Rocky Mountain (USA) region, and controversies surrounding instream flows abound. A specific problem involves water diversions (i.e., small dams that shunt water out of stream channels) during the summer irrigation season. We developed an approach to assess the effects of restoration of natural or less-than-natural summer flows on trout that accounts for variation in habitat over long segments of low-gradient, alluvial-valley streams. The approach has utility for managers because it can be conducted with hydologic data, aerial photographs, topographic maps, and a spreadsheet without extensive fieldwork. We applied the approach by assessing the effects of different summer flows on abundance of brown trout (Salmo trutta) in several streams annually dewatered in the Salt River Valley of western Wyoming. The assessment approach can be calibrated for other trout species and areas of the Rocky Mountain region.     

FORUM: Restoration of Stream Habitats in the Western United States: Restoration as Reexpression of Habitat Capacity

/ Ecological restoration is increasingly invoked as a tool for the maintenance and regeneration of biodiversity. Yet the conceptual foundations and assumptions underlying many restoration management activities are frequently unclear or unstated. Unforeseen, undesirable consequences of restoration activities may emerge as a result. A general conceptual framework for restoration is needed to better accommodate dynamic habitat systems and evolving biota in restoration strategies. A preliminary framework for stream habitat restoration emphasizing stream habitat-biota development is proposed. As developing systems, streams and stream biota exhibit temporal behaviors that change with stream environments. Underlying the dynamic development of streams is potential capacity. Streams express this capacity as an array of habitats over time and across the landscape. Human land uses in the western United States have rapidly altered aquatic habitats and the processes that shape habitat. As a result, the diversity of native fishes and their habitats has been suppressed. Restoration is fundamentally about allowing stream systems to reexpress their capacities. Several steps are provided to guide stream restoration activities. Key tasks include: identification of the historic patterns of habitat development; identification of developmental constraints; relief of those constraints; classification of sensitive, critical, or refuge habitats; protection of the developmental diversity that remains; and monitoring of biotic responses to habitat development. KEY WORDS: Stream habitat; Stream biota; System capacity; System development; Restoration; Classification     

Socially Strategic Ecological Restoration: A Game-Theoretic Analysis Shortened: Socially Strategic Restoration

Major transitions in a multiple-use or mosaic landscape often lead to frictions among new and existing users. In this article, we consider the problem of ecological restoration within a mosaic landscape in which restoration activities elicit feedbacks from individuals and groups that are harmed by restoration outcomes. Using game theory, we identify three potential outcomes ranked by the extent of restoration of ecosystem services and processes: nonstrategic, noncooperative strategic equilibrium, and cooperative bargaining solution. We identify conditions under which additional restoration can decrease the overall flow of ecosystem services and processes. A “strategic restorationist” will cease new restoration activities when the net effect of defensive response moves by farmers offsets gains. Imperfect information regarding expected payoffs to farmers can lead to inefficient overshooting or undershooting the optimal scale, geographical positioning, and form of restoration. Gains to all parties from cooperation might exist. As a case study and to aid model design, we consider restoration activities on California’s upper Sacramento River. An erratum to this article is available at .     

Dispersal Constraints for Stream Invertebrates: Setting Realistic Timescales for Biodiversity Restoration

Biodiversity goals are becoming increasingly important in stream restoration. Typical models of stream restoration are based on the assumption that if habitat is restored then species will return and ecological processes will re-establish. However, a range of constraints at different scales can affect restoration success. Much of the research in stream restoration ecology has focused on habitat constraints, namely the in-stream and riparian conditions required to restore biota. Dispersal constraints are also integral to determining the timescales, trajectory and potential endpoints of a restored ecosystem. Dispersal is both a means of organism recolonization of restored sites and a vital ecological process that maintains viable populations. We review knowledge of dispersal pathways and explore the factors influencing stream invertebrate dispersal. From empirical and modeling studies of restoration in warm-temperate zones of New Zealand, we make predictions about the timescales of stream ecological restoration under differing levels of dispersal constraints. This process of constraints identification and timescale prediction is proposed as a practical step for resource managers to prioritize and appropriately monitor restoration sites and highlights that in some instances, natural recolonization and achievement of biodiversity goals may not occur.     

Design of Experimental Streams for Simulating Headwater Stream Restoration1

Huang, Jung-Chen, William J. Mitsch, and Andrew D. Ward, 2010. Design of Experimental Streams for Simulating Headwater Stream Restoration. Journal of the American Water Resources Association (JAWRA) 1-15. DOI: 10.1111/j.1752-1688.2010.00467.x Abstract: Headwater streams flowing through agricultural fields in the midwestern United States have been extensively modified to accommodate subsurface drainage systems, resulting in deepened, straightened, and widened streams. To restore these headwater streams, partial or total reconstruction of channels is frequently attempted. There are different approaches to reconstructing the channel, yet there is little evidence that indicates which promises more success and there has been no experimental work to evaluate these approaches. This study designs three experimental channels – two-stage, self-design, and straightened channels – on a human-created swale at the Olentangy River Wetland Research Park, Columbus, Ohio, for long-term evaluation of headwater stream evolution after restoration. The swale receives a continuous flow of pumped river water from upstream wetlands. Using streamflow and stage data for the past 12 years, a channel-forming discharge of 0.18 m³/s was estimated from bankfull discharge, effective discharge, and recurrence interval. These stream channels, after construction, will be monitored to evaluate physical, chemical, and biological responses to different channels over a decade-long experiment. We hypothesize that the three stream restoration designs will eventually evolve to a similar channel form but with different time periods for convergence. Monitoring the frequency and magnitude of changes over at least 10 years is needed to document the most stable restored channel form.     

城市绿化规划研究初探--以长沙市雨花区为例

城市绿化规划是城市生态规划的基本内容。本文以长沙市雨花区为例，运用景观生态学原理，分析了城市绿地系统建设存在的问题，提出了城市生态绿地系统规划的基本内容和生态对策，可为一些城市的生态建设提供参考依据。     

Ecological Success in Stream Restoration: Case Studies from the Midwestern United States

Despite rapid growth in river restoration, few projects receive the necessary evaluation and reporting to determine their success or failure and to learn from experience. As part of the National River Restoration Science Synthesis, we interviewed 39 project contacts from a database of 1,345 restoration projects in Michigan, Wisconsin, and Ohio to (1) verify project information; (2) gather data on project design, implementation, and coordination; (3) assess the extent of monitoring; and (4) evaluate success and the factors that may influence it. Projects were selected randomly within the four most common project goals from a national database: in-stream habitat improvement, channel reconfiguration, riparian management, and water-quality improvement. Roughly half of the projects were implemented as part of a watershed management plan and had some advisory group. Monitoring occurred in 79% of projects but often was minimal and seldom documented biological improvements. Baseline data for evaluation often relied on previous data obtained under regional monitoring programs using state protocols. Although 89% of project contacts reported success, only 11% of the projects were considered successful because of the response of a specific ecological indicator, and monitoring data were underused in project assessment. Estimates of ecological success, using three criteria from Palmer and others (2005), indicated that half or fewer of the projects were ecologically successful, markedly below the success level that project contacts self-reported, and sent a strong signal of the need for well-designed evaluation programs that can document ecological success.     

城市绿化对改善西宁城市生态系统的影响

文章简要介绍城市生态系统的特点和功能以及城市绿化在城市生态系统中的地位和作用,通过探讨西宁市城市绿化的现状,提出了建设西宁生态园林城市的思路。     

城市生态系统恢复研究进展

定义了城市生态系统恢复的概念,分析了全球城市生态系统恢复状况,总结了城市生态系统恢复的研究进展,指出了城市生态系统恢复科学的研究方向.     

An Evaluation of the Influence of Natural Science in Regional-Scale Restoration Projects

Regional-scale restoration is a tool of growing importance in environmental management, and the number, scope, and complexity of restoration programs is increasing. Although the importance of natural science to the success of such projects generally is recognized, the actual use of natural science in these programs rarely has been evaluated. We used techniques of program evaluation to examine the use of natural science in six American and three Western European regional-scale restoration programs. Our results suggest that ensuring the technical rigor and directed application of the science is important to program development and delivery. However, the influence of science may be constrained if strategies for its integration into the broader program are lacking. Consequently, the influence of natural science in restoration programs is greatest when formal mechanisms exist for incorporating science into programs, for example, via a framework for integration of science and policy. Our evaluation proposes a model that can be used to enhance the influence of natural science in regional-scale restoration programs in the United States and elsewhere.     

Perceptions of Wood in Rivers and Challenges for Stream Restoration in the United States

This article reports a study of the public perception of large wood in rivers and streams in the United States. Large wood is an element of freshwater aquatic ecosystems that has attracted much scientific interest in recent years because of its value in biological and geomorphological processes. At the heart of the issue is the nature of the relationship between scientific recognition of the ecological and geomorphological benefits of wood in rivers, management practices utilizing wood for river remediation progress, and public perceptions of in-channel wood. Surveys of students’ perceptions of riverscapes with and without large wood in the states of Colorado, Connecticut, Georgia, Illinois, Iowa, Missouri, Oregon, and Texas suggest that many individuals in the United States adhere to traditionally negative views of wood. Except for students in Oregon, most respondents considered photographs of riverscapes with wood to be less aesthetically pleasing and needing more improvement than rivers without wood. Analysis of reasons given for improvement needs suggest that Oregon students are concerned with improving channels without wood for fauna habitat, whereas respondents elsewhere focused on the need for cleaning wood-rich channels for flood risk management. These results underscore the importance of public education to increase awareness of the geomorphological and ecological significance of wood in stream systems. This awareness should foster more positive attitudes toward wood. An integrated program of research, education, and policy is advocated to bridge the gap between scientific knowledge and public perception for effective management and restoration of river systems with wood.     

Flood Effects on an Alaskan Stream Restoration Project: The Value of Long‐Term Monitoring1

Densmore, Roseann V. and Kenneth F. Karle, 2009. Flood Effects on an Alaskan Stream Restoration Project: The Value of Long‐Term Monitoring. Journal of the American Water Resources Association (JAWRA) 45(6):1424‐1433. Abstract: On a nationwide basis, few stream restoration projects have long‐term programs in place to monitor the effects of floods on channel and floodplain configuration and floodplain vegetation, but long‐term and event‐based monitoring is required to measure the effects of these stochastic events and to use the knowledge for adaptive management and the design of future projects. This paper describes a long‐term monitoring effort (15 years) on a stream restoration project in Glen Creek in Denali National Park and Preserve in Alaska. The stream channel and floodplain of Glen Creek had been severely degraded over a period of 80 years by placer mining for gold, which left many reaches with unstable and incised streambeds without functioning vegetated floodplains. The objectives of the original project, initiated in 1991, were to develop and test methods for the hydraulic design of channel and floodplain morphology and for floodplain stabilization and riparian habitat recovery, and to conduct research and monitoring to provide information for future projects in similar degraded watersheds. Monitoring methods included surveyed stream cross‐sections, vegetation plots, and aerial, ground, and satellite photos. In this paper we address the immediate and outlying effects of a 25‐year flood on the stream and floodplain geometry and riparian vegetation. The long‐term monitoring revealed that significant channel widening occurred following the flood, likely caused by excessive upstream sediment loading and the fairly slow development of floodplain vegetation in this climate. Our results illustrated design flaws, particularly in regard to identification and analysis of sediment sources and the dominant processes of channel adjustment.     

Observations and Modeling of Stream Plunging in an Urban Lake1

Owens, Emmet M., Steven W. Effler, Anthony R. Prestigiacomo, David A. Matthews, and Susan M. O’Donnell, 2012. Observations and Modeling of Stream Plunging in an Urban Lake. Journal of the American Water Resources Association (JAWRA) 48(4): 707‐721. DOI: 10.1111/j.1752‐1688.2012.00646.x Abstract: The plunging behavior of two tributaries in Onondaga Lake, New York, is quantified based on a program of monitoring, process studies, and modeling. The dynamics of buoyancy of the tributaries are resolved with hourly measurements of temperature (T), specific conductance (SC), and turbidity (Tn) at the mouths, and observations every 6 h in the lake. Negative buoyancy of the tributaries is found to diminish and change rapidly during runoff events compared to dry periods. In‐lake patterns of the transport of plunging inflow are resolved for dry weather conditions using a dye tracer, and following a runoff event through measurements of T, SC, and Tn. The hydrodynamic/transport model ELCOM (Estuary Lake and Coastal Ocean Model) is demonstrated to perform well in simulating these patterns. Analyses conducted with the model establish the importance of diurnal effects and in‐lake mixing mediated by wind, the need for temporally detailed measurements during runoff events, and modifications of the plunging behavior of the urban tributary as it passes through a harbor. The model provides critical information to support rehabilitation programs for the lake by quantifying the transport of the two largest tributaries, particularly the distribution of the loads between the upper waters and stratified layers. The model predicts that 10% of the urban tributary load enters the upper waters of the lake within 24 h for a dry weather period; this portion increases to 30% for a runoff event.     

Predicting Opportunities for Greening and Patterns of Vegetation on Private Urban Lands

This paper examines predictors of vegetative cover on private lands in Baltimore, Maryland. Using high-resolution spatial data, we generated two measures: “possible stewardship,” which is the proportion of private land that does not have built structures on it and hence has the possibility of supporting vegetation, and “realized stewardship,” which is the proportion of possible stewardship land upon which vegetation is growing. These measures were calculated at the parcel level and averaged by US Census block group. Realized stewardship was further defined by proportion of tree canopy and grass. Expenditures on yard supplies and services, available by block group, were used to help understand where vegetation condition appears to be the result of current activity, past legacies, or abandonment. PRIZM™ market segmentation data were tested as categorical predictors of possible and realized stewardship and yard expenditures. PRIZM™ segmentations are hierarchically clustered into 5, 15, and 62 categories, which correspond to population density, social stratification (income and education), and lifestyle clusters, respectively. We found that PRIZM 15 best predicted variation in possible stewardship and PRIZM 62 best predicted variation in realized stewardship. These results were further analyzed by regressing each dependent variable against a set of continuous variables reflective of each of the three PRIZM groupings. Housing age, vacancy, and population density were found to be critical determinants of both stewardship metrics. A number of lifestyle factors, such as average family size, marriage rates, and percentage of single-family detached homes, were strongly related to realized stewardship. The percentage of African Americans by block group was positively related to realized stewardship but negatively related to yard expenditures.     

Perceptions about Environmental Use and Future Restoration of an Urban Estuary

Recent interest in restoring urban ecosystems has engendered studies on public perceptions of these ecosystems and future land use. This paper examines the perceptions of people using the waterfront area of the New York/New Jersey harbour estuary about their use of the area, and how this environment could be improved. Pollution was viewed as the most important problem in New Jersey, and removing pollution was rated the most important way to improve the waterfront habitat. Using the remaining undeveloped area for natural habitat and to improve quality of life were rated as the most important uses of the waterfront. People valued the waterfront for walking, providing open green space, and as a place to commune with nature without people. Management options people favoured were removing pollution and cleaning up rubbish and adding educational signs and information brochures about the remaining, natural habitat. Age, income and education influenced which activities people said they undertook. For improvements to the waterfront: Hispanics rated adding educational signs and creating information brochures higher, Blacks rated building promenades as more important, and Asians and Whites rated improving habitat for birds and butterflies more important than others. The data indicate that the public has a firm understanding of the big picture (pollution in the region and locally), habitat improvement, and of the small improvements that can be done locally. Planners and managers could move forward on three fronts: source reduction, wildlife habitat improvement, and amenity (signs, brochures, cleaning up rubbish) development. Understanding how people use an environment, and wish to improve it, can provide valuable information for future restoration and management of urban environments generally, as well as for structuring a citizen advisory committee.     

A Critical Realist Perspective on Urban Environmental Risk: a case study of an informal settlement in South Africa

This paper uses a critical realist framework to analyse environmental risk in a local space. It argues that urban risk needs to be understood in terms of the causal mechanisms that shape risk events and the contingent conditions that provide the context within which they occur. It uses a case study of an informal settlement in Hout Bay, South Africa, to explore these ideas. It is an approach that challenges the dominant technical and scientific discourse that usually determines the understanding of risk. The research suggests that the key causal mechanisms that shape risk events in informal settlements are globalisation and urbanisation, poverty and vulnerability, the social construction of environmental problems, gender relations, the rise of civil society organisations, political governance and the spatial distribution of risk. The environmental characteristics of the site, as well as the development of the settlement during the political transformation in South Africa, are the key contingent conditions determining the nature of risk.