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Amy E. East

Bio: Amy E. East is an academic researcher from United States Geological Survey. The author has contributed to research in topics: Sediment & Fluvial. The author has an hindex of 13, co-authored 34 publications receiving 806 citations.
Topics: Sediment, Fluvial, Dam removal, Climate change, Canyon

Papers published on a yearly basis

Papers
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Journal ArticleDOI
TL;DR: The authors investigated the downstream effects of sediment released during the largest dam removal in history, on the Elwha River, Washington, USA, by measuring changes in riverbed elevation and topography, bed sediment grain size, and channel planform as two dams were removed in stages over two years.

199 citations

Journal ArticleDOI
TL;DR: In this article, a working group at the USGS John Wesley Powell Center for Analysis and Synthesis reviewed and synthesized available studies of dam removals and their findings, and some general conclusions have emerged: physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam-removal strategy.
Abstract: 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.

134 citations

Journal ArticleDOI
TL;DR: In this article, the authors provide a source-to-sink sediment budget of this sediment release during the first two years of the project (September 2011-September 2013) and synthesize the geomorphic changes that occurred to downstream fluvial and coastal landforms.

128 citations

Journal ArticleDOI
TL;DR: In this article, the authors synthesize information from empirical studies and ecological theory into conceptual models that depict key physical and biological links driving ecological responses to removing dams, and define models for three distinct spatial domains: upstream of the former reservoir, within the reservoir, and downstream of the removed dam.
Abstract: One of the desired outcomes of dam decommissioning and removal is the recovery of aquatic and riparian ecosystems. To investigate this common objective, we synthesized information from empirical studies and ecological theory into conceptual models that depict key physical and biological links driving ecological responses to removing dams. We define models for three distinct spatial domains: upstream of the former reservoir, within the reservoir, and downstream of the removed dam. Emerging from these models are response trajectories that clarify potential pathways of ecological transitions in each domain. We illustrate that the responses are controlled by multiple causal pathways and feedback loops among physical and biological components of the ecosystem, creating recovery trajectories that are dynamic and nonlinear. In most cases, short-term effects are typically followed by longer-term responses that bring ecosystems to new and frequently predictable ecological condition, which may or may not be similar to what existed prior to impoundment.

74 citations


Cited by
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07 May 2015
TL;DR: It is shown that fire weather seasons have lengthened across 29.6 million km2 (25.3%) of the Earth's vegetated surface, resulting in an 18.7% increase in global mean fire weather season length.
Abstract: Climate strongly influences global wildfire activity, and recent wildfire surges may signal fire weather-induced pyrogeographic shifts. Here we use three daily global climate data sets and three fire danger indices to develop a simple annual metric of fire weather season length, and map spatio-temporal trends from 1979 to 2013. We show that fire weather seasons have lengthened across 29.6 million km2 (25.3%) of the Earth's vegetated surface, resulting in an 18.7% increase in global mean fire weather season length. We also show a doubling (108.1% increase) of global burnable area affected by long fire weather seasons (>1.0 σ above the historical mean) and an increased global frequency of long fire weather seasons across 62.4 million km2 (53.4%) during the second half of the study period. If these fire weather changes are coupled with ignition sources and available fuel, they could markedly impact global ecosystems, societies, economies and climate.

693 citations

Journal ArticleDOI
TL;DR: A review of river restoration can be found in this article, where the authors critically examine how contemporary practitioners approach river restoration and challenges for implementing restoration, which include clearly identified objectives, holistic understanding of rivers as ecosystems, and the role of restoration as a social process.
Abstract: River restoration is one of the most prominent areas of applied water-resources science. From an initial focus on enhancing fish habitat or river appearance, primarily through structural modification of channel form, restoration has expanded to incorporate a wide variety of management activities designed to enhance river process and form. Restoration is conducted on headwater streams, large lowland rivers, and entire river networks in urban, agricultural, and less intensively human-altered environments. We critically examine how contemporary practitioners approach river restoration and challenges for implementing restoration, which include clearly identified objectives, holistic understanding of rivers as ecosystems, and the role of restoration as a social process. We also examine challenges for scientific understanding in river restoration. These include: how physical complexity supports biogeochemical function, stream metabolism, and stream ecosystem productivity; characterizing response curves of different river components; understanding sediment dynamics; and increasing appreciation of the importance of incorporating climate change considerations and resiliency into restoration planning. Finally, we examine changes in river restoration within the past decade, such as increasing use of stream mitigation banking; development of new tools and technologies; different types of process-based restoration; growing recognition of the importance of biological-physical feedbacks in rivers; increasing expectations of water quality improvements from restoration; and more effective communication between practitioners and river scientists.

419 citations

Journal ArticleDOI
20 Sep 2019-Science
TL;DR: How flow variability influences long-term persistence of riverine assemblages is demonstrated, and researchers are disentangling the direct effects of flow on communities and ecosystem processes from its indirect effects (e.g., via species interactions, light-blocking turbidity).
Abstract: BACKGROUND Early civilizations developed around seasonal river floodplains, and the natural rhythm of rivers remains critical to humans today. We use streams and rivers to meet drinking water, irrigation, and hydropower needs by storing and moving water in complex ways, at the times and places of our choosing. Consequently, many of Earth’s rivers have flow regimes that are “unnatural” in magnitude, frequency, duration, and timing. The rise in river degradation globally has motivated research on the link between hydrologic alteration and declines in valued biota. At the same time, largely fueled by new technologies and methods, research has expanded to understand the patterns in, and drivers of, riverine processes like primary production, in both near-pristine and degraded rivers. A third line of research, stymied by how difficult it has been to restore degraded rivers, has called for process-based restoration, building on knowledge from the other two research thrusts. Today’s hydroecological science seeks to understand the mechanisms whereby flow regimes affect biota and ecosystem processes, and the interplay between them, in a three-way interaction we call the flow-biota-ecosystem processes nexus. ADVANCES By shifting the focus from static patterns at sites to dynamic processes along river networks, advances are being made to understand the interactions and feedbacks at the nexus. Fueled by increasingly available time-series data and novel modeling, emerging research ranges from studies on regime-based properties such as flow periodicity and its change, to studies on river network structure and associated spatial variation in flow and water chemistry. These studies demonstrate how flow variability influences long-term persistence of riverine assemblages, and they are disentangling the direct effects of flow on communities and ecosystem processes from its indirect effects (e.g., via species interactions, light-blocking turbidity). Changes in temporal patterns in flow magnitudes can increase risk of community collapse and alter key ecosystem processes such as primary production. Growing research shows that storm flows not only enhance inputs and downstream export of terrestrially derived carbon to rivers but, when associated with sustained hydrologic connectivity with soils, exert particular influence on water chemistry and biogeochemical processes that can influence food webs. Increased availability of environmental sensors has stimulated research, showing that extreme flows may impart disproportionate impacts on stream metabolism, but the relationship can depend on the predictability of those flows. Research combining changes in flow patterns with stable isotope analyses is revealing how temporal fluctuations in habitat, and in the quality and quantity of basal resources, influence trophic pathways and resulting food-web structure. Evidence suggests that restoring particular facets of a flow regime can produce desirable conservation outcomes, but context is paramount. Restoration actions going beyond discrete flow events and enhancing groundwater-influenced river habitat or redirecting subsurface flow paths may be critical in future climates. OUTLOOK Our understanding of the flow-biota-ecosystem processes nexus is still incomplete and is a frontier research topic. Challenges include connecting organismal and ecosystem-level processes, and understanding the role of microbial communities as intermediaries. Capturing the effects of watershed-level physical and biogeochemical heterogeneity, and parsing out direct, indirect, or cascading effects of flow alteration on biota and processes would also reduce uncertainty in restoration outcomes, particularly in novel, nonstationary environments. Understanding how much flow restoration alone can achieve in urban watersheds is an urgent need, as is translating findings from hydroecology to design green infrastructure and flow release programs from reservoirs. These management tools may offer growing opportunities to experiment with flow regimes, which will assist in refining process-based river restoration. Both solid science, and effective translation into practice will be needed to curb the fast pace of global river ecosystem degradation.

270 citations

Journal ArticleDOI
TL;DR: The value in evaluating boundaries between components of geomorphic systems as transition zones and examining the fluxes across them to understand landscape functioning is emphasized.
Abstract: Connectivity describes the efficiency of material transfer between geomorphic system components such as hillslopes and rivers or longitudinal segments within a river network. Representations of geomorphic systems as networks should recognize that the compartments, links, and nodes exhibit connectivity at differing scales. The historical underpinnings of connectivity in geomorphology involve management of geomorphic systems and observations linking surface processes to landform dynamics. Current work in geomorphic connectivity emphasizes hydrological, sediment, or landscape connectivity. Signatures of connectivity can be detected using diverse indicators that vary from contemporary processes to stratigraphic records or a spatial metric such as sediment yield that encompasses geomorphic processes operate over time and space. One approach to measuring connectivity is to determine the fundamental temporal and spatial scales for the phenomenon of interest and to make measurements at a sufficiently large multiple of the fundamental scales to capture reliably a representative sample. Another approach seeks to characterize how connectivity varies with scale, by applying the same metric over a wide range of scales or using statistical measures that characterize the frequency distributions of connectivity across scales. Identifying and measuring connectivity is useful in basic and applied geomorphic research and we explore the implications of connectivity for river management. Common themes and ideas that merit further research include; increased understanding of the importance of capturing landscape heterogeneity and connectivity patterns; the potential to use graph and network theory metrics in analyzing connectivity; the need to understand which metrics best represent the physical system and its connectivity pathways, and to apply these metrics to the validation of numerical models; and the need to recognize the importance of low levels of connectivity in some situations. We emphasize the value in evaluating boundaries between components of geomorphic systems as transition zones and examining the fluxes across them to understand landscape functioning.

222 citations

Journal ArticleDOI
01 May 2015-Science
TL;DR: Dam removals are reconnecting rivers in the United States Forty years ago, the demolition of large dams was mostly fiction, notably plotted in Edward Abbey's novel The Monkey Wrench Gang.
Abstract: Forty years ago, the demolition of large dams was mostly fiction, notably plotted in Edward Abbey's novel The Monkey Wrench Gang. Its 1975 publication roughly coincided with the end of large-dam construction in the United States. Since then, dams have been taken down in increasing numbers as they have filled with sediment, become unsafe or inefficient, or otherwise outlived their usefulness ( 1 ) (see the figure, panel A). Last year's removals of the 64-m-high Glines Canyon Dam and the 32-m-high Elwha Dam in northwestern Washington State were among the largest yet, releasing over 10 million cubic meters of stored sediment. Published studies conducted in conjunction with about 100 U.S. dam removals and at least 26 removals outside the United States are now providing detailed insights into how rivers respond ( 2 , 3 ).

218 citations