Desiree Tullos

Analysis of functional traits in reconfigured channels: implications for the bioassessment and disturbance of river restoration

Abstract Channel reconfiguration is a popular but controversial approach to river restoration, and ecological responses to channel reconfiguration have not been rigorously assessed. We compared physical-habitat variables, taxonomic and functional-trait diversities, taxonomic composition, and functional-trait abundances between 24 pairs of upstream (control) and downstream reconfigured (restored) reaches in 3 catchment land uses (urban, agricultural, rural) across the North Carolina Piedmont. We asked how environmental filters and functional species traits might provide insight to biological responses to restoration. Taxonomic and functional-trait differences between control and restored reaches suggest that restoration affected aquatic assemblages only in agricultural and rural catchments. Our results highlight 2 important aspects of channel reconfiguration as a restoration practice. First, responses to restoration differ between agricultural/rural and urban catchments, possibly because of modified hydrological regimes caused by urbanization. Second, we find evidence that channel reconfiguration disturbs food and habitat resources in stream ecosystems. Taxa sensitive to disturbance were characteristic of control reaches, whereas insensitive taxa were characteristic of restored reaches. Abundances of traits related to reproduction (voltinism, development, synchronization of emergence, adult life span), mobility (occurrence in drift, maximum crawling rate, swimming ability), and use of resources (trophic and habitat preferences) differed significantly between control and recently restored reaches. Our results suggest that taxa in restored habitats are environmentally selected for traits favored in disturbed environments. Our work suggests how functional-trait approaches could benefit the practice of river restoration when used to target restoration activities and to develop informed expectations regarding recovery following restoration activities.

Modeling the costs and benefits of dam construction from a multidisciplinary perspective.

Although the benefits of dam construction are numerous, particularly in the context of climate change and growing global demand for electricity, recent experience has shown that many dams have serious negative environmental, human, and political consequences. Despite an extensive literature documenting the benefits and costs of dams from a single disciplinary perspective, few studies have simultaneously evaluated the distribution of biophysical, socio-economic, and geopolitical implications of dams. To meet the simultaneous demands for water, energy, and environmental protection well into the future, a broader view of dams is needed. We thus propose a new tool for evaluating the relative costs and benefits of dam construction based on multi-objective planning techniques. The Integrative Dam Assessment Modeling (IDAM) tool is designed to integrate biophysical, socio-economic, and geopolitical perspectives into a single cost/benefit analysis of dam construction. Each of 27 different impacts of dam construction is evaluated both objectively (e.g., flood protection, as measured by RYI years) and subjectively (i.e., the valuation of said flood protection) by a team of decision-makers. By providing a visual representation of the various costs and benefits associated with two or more dams, the IDAM tool allows decision-makers to evaluate alternatives and to articulate priorities associated with a dam project, making the decision process about dams more informed and more transparent. For all of these reasons, we believe that the IDAM tool represents an important evolutionary step in dam evaluation.

Geomorphic and Ecological Disturbance and Recovery from Two Small Dams and Their Removal

Dams are known to impact river channels and ecosystems, both during their lifetime and in their decommissioning. In this study, we applied a before-after-control-impact design associated with two small dam removals to investigate abiotic and biotic recovery trajectories from both the elimination of the press disturbance associated with the presence of dams and the introduction of a pulse disturbance associated with removal of dams. The two case studies represent different geomorphic and ecological conditions that we expected to represent low and high sensitivities to the pulse disturbance of dam removal: the 4 m tall, gravel-filled Brownsville Dam on the wadeable Calapooia River and the 12.5 m tall, sand and gravel-filled Savage Rapids Dam on the largely non-wadeable Rogue River. We evaluated both geomorphic and ecological responses annually for two years post removal, and asked if functional traits of the macroinvertebrate assemblages provided more persistent signals of ecological disturbance than taxonomically defined assemblages over the period of study. Results indicate that: 1) the presence of the dams constituted a strong ecological press disturbance to the near-downstream reaches on both rivers, despite the fact that both rivers passed unregulated flow and sediment during the high flow season; 2) ecological recovery from this press disturbance occurred within the year following the restoration action of dam removal, whereas signals of geomorphic disturbance from the pulse of released sediment persisted two years post-removal, and 3) the strength of the press disturbance and the rapid ecological recovery were detected regardless of whether recovery was assessed by taxonomic or functional assemblages and for both case studies, in spite of their different geomorphic settings.

Biophysical, Socioeconomic, and Geopolitical Vulnerabilities to Hydropower Development on the Nu River, China

Rapid hydropower development is occurring in China’s Yunnan province in response to increasing clean energy demands, exposing potential vulnerabilities of the area’s ecosystems, communities, and geopolitical systems. Here, the authors present original data on the cultures, economics, hydro-politics, and environments of the Nu River basin, based on household surveys, analysis of geopolitical events, and hydrological, hydraulic, and landscape modeling. The authors identify sources of vulnerability and investigate relationships among biophysical, socioeconomic, and geopolitical elements that contribute to vulnerability. The results illustrate the role of geographic isolation in intensifying vulnerability to hydropower development and how access to information, data uncertainty, and geopolitics influence the vulnerability of people and the environment. The authors emphasize specific needs for developing support mechanisms for social, ecological, and political groups that are vulnerable to hydropower development.

Introduction to the special issue: understanding and linking the biophysical, socioeconomic and geopolitical effects of dams.

Dams have made important contributions to human development, and the benefits derived from them have been considerable (World Commission on Dams, 2000). With the rising global population and desire to increase quality of life, dams are prominently staged to deliver hydropower, irrigation and drinking water supplies, recreation, navigation, and many other resources to the growing planet. Further, the uncertainty of the future climate regime may mean that dams will play an increasingly important role in water resources. For example, it is predicted that droughtaffected areas will likely increase in extent and flood risks will be augmented in response to increased frequency of heavy precipitation events (IPCC, 2007), the effects of both of which may be ameliorated by dams. Thus, the construction of new dams, while in decline in the United States since the 1970s (US Army Corps of Engineers, 1996), may see a renewed intensity both at home and abroad. At the same time, dams are increasingly slated for removal, reflecting a growing concern over their adverse ecological, social, and economic impacts (Pejchar and Warner, 2001). Aging structures, which can pose a risk to public safety, are increasingly removed under new policies and funding sources to support removal projects (Heinz Center, 2002). Dam removal is also emerging as a promising option for restoring continuums and reconnecting habitats for migratory fish species, including anadromous salmon, that are federally listed as threatened or endangered in the United States (Gregory et al., 2002). However, there is a great deal of uncertainty about the consequences of dam removal (Aspen Institute, 2002; Hart et al., 2002), particularly the unknowns related to the extent, magnitude, and timing of physical and ecological outcomes (Heinz Center, 2002; Hart et al., 2002). Thus, dams are a crucial issue for resource managers, scientists and policymakers. To advance the knowledge about and inform the management of dams, this special issue of the Journal of Environmental Management presents cutting-edge research in various academic disciplines and proposes new multi-disciplinary approaches for understanding and predicting how dams and dam removals affect societies and ecosystems. The goal of this collection is to offer guidance for and provoke conversations about the interdisciplinary nature of dams. The idea for the special issue was conceived at a symposium, held in April of 2007 at Skamania Lodge on the Columbia River in Washington State, USA, which brought together scientists and resource managers to discuss the effects of dams on social and ecological systems. Many of

Synthesis of common management concerns associated with dam removal

Managers make decisions regarding if and how to remove dams in spite of uncertainty surrounding physical and ecological responses, and stakeholders often raise concerns about certain negative effects, regardless of whether these concerns are warranted at a particular site. We used a dam-removal science database supplemented with other information sources to explore seven frequently raised concerns, herein Common Management Concerns (CMCs). We investigate the occurrence of these concerns and the contributing biophysical controls. The CMCs addressed are the following: degree and rate of reservoir sediment erosion, excessive channel incision upstream of reservoirs, downstream sediment aggradation, elevated downstream turbidity, drawdown impacts on local water infrastructure, colonization of reservoir sediments by nonnative plants, and expansion of invasive fish. Biophysical controls emerged for some of the concerns, providing managers with information to assess whether a given concern is likely to occur at a site. To fully assess CMC risk, managers should concurrently evaluate site conditions and identify the ecosystem or human uses that will be negatively affected if the biophysical phenomenon producing the CMC occurs. We show how many CMCs have one or more controls in common, facilitating the identification of multiple risks at a site, and demonstrate why CMC risks should be considered in the context of other factors such as natural watershed variability and disturbance history.

A review of atmospheric and land surface processes with emphasis on flood generation in the Southern Himalayan rivers

Floods in the southern rim of the Indian Himalayas are a major cause of loss of life, property, crops, infrastructure, etc. They have long term socio-economic impacts on the habitat living along/across the Himalayas. In the recent decade extreme precipitation events have led to numerous flash floods in and around the Himalayan region. Sporadic case-based studies have tried to explain the mechanisms causing the floods. However, in some of the cases, the causative mechanisms have been elusive. Various types of flood events have been debated at different spatial and temporal scales. The present study provides an overview of mechanisms that lead to floods in and around the southern rim of the Indian Himalayas. Atmospheric processes, landuse interaction, and glacier-related outbreaks are considered in the overview.

Dam removal: Listening in

Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam-removal studies over the last few decades motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam-removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad-scale ecological effects, and gives managers information needed to understand and predict long-term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam-removal methods in the U.S.

Finding water scarcity amid abundance using human–natural system models

Significance Climate change will heighten the need to anticipate water shortages worldwide. The task is daunting due to water’s variability, spatial-temporal movement, feedbacks, and other system complexities. A high-resolution coupled human–natural system model identifies how both climate change and socioeconomic drivers will alter water scarcity in future decades. The results illuminate how water scarcity varies greatly across small distances and brief time periods, even in basins where water may be relatively abundant overall. These findings, and other unexpected results that may seem counterintuitive, underscore the potential value of such models for policy. Water scarcity afflicts societies worldwide. Anticipating water shortages is vital because of water’s indispensable role in social-ecological systems. But the challenge is daunting due to heterogeneity, feedbacks, and water’s spatial-temporal sequencing throughout such systems. Regional system models with sufficient detail can help address this challenge. In our study, a detailed coupled human–natural system model of one such region identifies how climate change and socioeconomic growth will alter the availability and use of water in coming decades. Results demonstrate how water scarcity varies greatly across small distances and brief time periods, even in basins where water may be relatively abundant overall. Some of these results were unexpected and may appear counterintuitive to some observers. Key determinants of water scarcity are found to be the cost of transporting and storing water, society’s institutions that circumscribe human choices, and the opportunity cost of water when alternative uses compete.

Review of challenges of and practices for sustainable management of mountain flood hazards

Mountain areas are the source of important cultural, ecological, and life-sustaining resources, but are also subject to devastating losses from floods. To work toward reducing these losses, this paper aims to (a) synthesize understanding on the elements that make flood risk management challenging in high mountain areas and (b) identify practices that can be applied in reducing the exposure and vulnerability of mountain communities. Through a review of the literature and case studies, we identified the flood-related challenges associated with complex topography and hydrogeology, insufficient data and infrastructure, weakly defined governance structures, and sensitivity to climatic and landscape changes. We examined five practices needed for reducing flood risk in these vulnerable areas, involving (1) the acquisition and effective dissemination of information about floods, (2) basin-scale hazard assessment and disaster response planning, (3) clearly defining governance responsibilities and distributing them across multiple jurisdictional layers, (4) implementing effective and diverse mitigation measures, and (5) training and engaging local residents and officials in flood risk reduction. Considerations and needs for implementing these practices in mountain areas are discussed, highlighting the commitment of resources needed for distributed governance, effective planning, land use and building regulations, and engagement of the public.