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Amy East

I study how landscapes change over time, focusing on response to hydroclimatic and anthropogenic disturbances. These studies inform resource management as well as fundamental understanding of earth-surface processes. I am also interested in how sediment moves from source to sink, and how the sedimentary record reflects changes in sediment supply and transport.

Biography

**Please note: Prior to 2014, my name was Amy Draut and my earlier publications used that name. **

Research Geologist, U.S. Geological Survey, Coastal and Marine Geology Program (2006 - present), Santa Cruz, CA

Postdoctoral Researcher, U.S. Geological Survey / University of California, Santa Cruz (2003 - 2006)

Ph.D., Geology and Geophysics, 2003

  • Massachusetts Institute of Technology / Woods Hole Oceanographic Institution Joint Program, Cambridge and Woods Hole, MA

B.S., Geological Sciences and Environmental Studies, 1997

  • Tufts University, Medford, MA

 

Research Topics

(Selected publications listed beneath each topic. For a complete publication list, contact me at aeast@usgs.gov)

Effects of Large Dam Removal on River Channel and Floodplain Morphology

I have spent more than 12 years studying the removal of large dams on the Elwha River, Washington, and the Carmel River, California. Dam-removal research allows us to understand better how landscapes respond to large sediment pulses, a fundamental and long-standing problem in geomorphology but one that is rarely studied at field scales because of the unanticipated nature of most sediment-pulse releases. Because dam removal is increasingly used as a means to restore watershed and coastal enviroments, it is critical to understand how physical and biological systems respond to these substantial perturbations. In addition to ongoing studies on the Elwha River and Carmel River, I was one of five Principal Investigators on a USGS John Wesley Powell Center working group that synthesized the state of knowledge in dam-removal science (the working group officially lasted from 2013 to 2015, but with ongoing collaborations).

The Carmel River study (removal of 32-m-high San Clemente Dam in late 2015) was unique in being the first large dam removal in a Mediterranean hydroclimatic setting, and the first in which the river experienced large floods so soon post-dam-removal (two 10-year floods and a 30-year flood, about a year after removal). We (Harrison et al., ESPL) documented the importance of high flows in driving erosion of reservoir sediment and moving sediment downstream in a region where transport capacity is elevated only very episodically.

Removal of two large dams (64 m and 32 m high) on the Elwha River during 2011-2014 constitutes the largest dam removal to date in the U.S. In addition to restoring salmonid fish access to the watershed in Olympic National Park, dam removal is an unprecedented opportunity to study fluvial and coastal response to large-scale sediment influx. The Elwha program is a major focus for agencies including the USGS, National Park Service, Bureau of Reclamation, and the Lower Elwha Klallam Tribe, whose lands are part of the restoration area. I lead a USGS study of topography and sediment grain size on the lower Elwha River before, during, and after dam removal; our study here began in 2006, using field data and historical aerial photographs in the first comprehensive evaluation of how an anabranching, gravel-bed river responded to losing its upstream sediment supply through damming. 

We found that the Elwha River changed substantially as a result of dam removal, with geomorphic changes that were two- to ten-fold as large as those caused by a 40-year flood four years before dam removal. Over five years, the river moved more than 20 million tons of sediment out of the two former reservoirs, a sediment pulse comparable in scale to that caused by the 1980 Mount St. Helens volcanic eruption. On the Elwha River, 90% of the released sediment reached the river mouth, with only 10% stored in the fluvial system. The major disturbance (bed aggradation and major topographic changes) lasted a brief 5 months; given sufficient stream power, rivers can efficiently export sediment pulses from a dam removal of this size even without flood hydrology. This, and other findings from this project, will be important information for management decisions in future large dam removals. We identified significant differences in responses of this gravel-bed river to flows of various magnitude under high vs. low sediment supply, and use these results to proposed that the concept of a threshold stream power is likely untenable in gravel-bed rivers.

East, A.E., Logan, J.B., Mastin, M.C., Ritchie, A.C., Bountry, J.A., Magirl, C.S., and Sankey, J.B., Geomorphic evolution of a gravel-bed river under sediment-starved vs. sediment-rich conditions: River response to the world's largest dam removal. Journal of Geophysical Research - Earth Surface, in revision. 

Harrison, L.R., East, A.E., Smith, D.P., Logan, J.B., Bond, R., Nicol, C., Williams, T.H., Boughton, D.A., Chow, K., and Luna, L., River response to large-dam removal in a Mediterranean hydroclimatic setting: Carmel River, California USA: Earth Surface Processes and Landforms, in press, DOI: 10.1002/esp.4464.

Ritchie, A.C., Warrick, J.A., East, A.E., Magirl, C.S., Stevens, A.W., Bountry, J.A., Randle, T.J., Curran, C.A., Hilldale, R.C., Duda, J.J., Gelfenbaum, G.R., Miller, I.M., Pess, G.R., Foley, M.M., McCoy, R., and Ogston, A.S., 2018, Morphodynamic evolution following sediment release from the world’s largest dam removal: Nature Scientific Reports, v. 8, 13279, doi:10.1038/s41598-018-30817.

East, A.E., Pess, G.R., Bountry, J.A., Magirl, C.S., Ritchie, A.C., Logan, J.B., Randle, T.J., Mastin, M.C., Minear, J.T., Duda, J.J., Liermann, M.C., McHenry, M.L., Beechie, T.J., and Shafroth, P.B., 2015, Large-scale dam removal on the Elwha River, Washington, USA: River channel and floodplain geomorphic change. Geomorphology, v. 228, p. 765–786, doi:10.1016/j.geomorph.2014.08.028

Warrick, J.A., Bountry, J.A., East, A.E., Magirl, C.S., Randle, T.J., Gelfenbaum, G., Ritchie, A.C., Pess, G.R., Leung, V., and Duda, J.J., 2015, Large-scale dam removal on the Elwha River, Washington, USA: Source-to-sink sediment budget and synthesis. Geomorphology, v. 246, p. 729–750.

Draut, A.E., and Ritchie, A.C., 2015, Sedimentology of new fluvial deposits on the Elwha River, Washington, USA, formed during large-scale dam removal: River Research and Applications, v. 31, p. 42–61, doi:10.1002/rra.2724

Draut, A.E., Logan, J.B., and Mastin, M.C., 2011, Channel evolution on the dammed Elwha River, Washington, USA: Geomorphology, v. 127, p. 71-87.

Draut, A.E., Logan, J.B., McCoy, R.E., McHenry, M., and Warrick, J.A., 2008, Channel evolution on the lower Elwha river, Washington, 1939 to 2006: US Geological Survey Scientific Investigations Report 2008-5127, http://pubs.usgs.gov/sir/2008/5127/

See also our synthesis papers on dam removal:

Major, J.J., East, A.E., O’Connor, J.E., Grant, G.E., Wilcox, A.C., Magirl, C.S., Collins, M.J., and Tullos, D.D., 2017, Geomorphic responses to dam removals in the United States—a two-decade perspective, in Tsutsumi, D., and Laronne, J., eds., Gravel-Bed Rivers: Processes and Disasters, p. 355–384. Wiley-Blackwell, ISBN 978-1-118-97140-6.

Foley, M.M., Bellmore, J.R., O’Connor, J.E., Duda, J.J., East, A.E., Grant, G.E., Anderson, C.W., Bountry, J.A., Collins, M.J., Connolly, P.J., Craig, L.S., Evans, J.E., Greene, S.L., Magilligan, F.J., Magirl, C.S., Major, J.J., Pess, G.R., Randle, T.J., Shafroth, P.B., Torgersen, C.E., Tullos, D., and Wilcox, A.C., 2017, Dam removal—listening in: Water Resources Research, v. 53, 5229–5246, doi:10.1002/2017WR020457.

Bellmore, J.R., Pess, G.R., Duda, J.J., O’Connor, J.E., East, A.E., Foley, M.M., Wilcox, A.C., Major, J., Shafroth, P.B., Magirl, C.S., Anderson, C.W., Evans, J.E., Torgersen, C.E., and Craig, L.S. Conceptualizing ecological responses to dam removal: if you remove it, what’s to come? BioScience, in press.

 

Landscape response to extreme hydroclimatic disturbances, California

Landscapes of the western U.S. coast commonly produce and export large sediment fluxes, given their steep terrain, tectonic activity, and potential to receive extreme rainfall. I study landscape response to severe hydroclimatic disturbances in several California watersheds, including drought and extreme rainfall (on seasonal and individual-event scales), and some post-fire runoff situations. A recent paper of ours examined a regime shift evident in sediment export from the San Lorenzo River, central CA coast, as a result of record rainfall in the winter of 2017, which induced substantial fluvial sediment flux due to landslide debris becoming abundant in the watershed (East et al., 2018), and looked at coupling between the fluvial suspended-sediment regime and coastal geomorphic response.

With colleagues in the USGS Geology, Minerals, Energy and Geophysics group, I have an ongoing study of an extreme landslide and debris-flow situation caused by intense rainfall from a major storm in 2018 that hit the Tuolumne basin, Sierra Nevada foothills. That two-hour rain event produced 40-100x the amount of sediment normally carried by that river in a year, despite being generated from only one-twentieth of one percent of the basin area. Understanding the effects of such hydrologic disturbances is critical to constraining effects of modern climate change on landscapes and sediment budgets, with applications for infrastructure and human safety, river and coastal ecosystems, and water-resource security.

East, A.E., Stevens, A.W., Ritchie, A.C., Barnard, P.L., Campbell-Swarzenski, P.L., Collins, B.D., and Conaway, C.H., 2018, A regime shift in sediment export from a coastal watershed during a record wet winter, California—implications for landscape response to hydroclimatic extremes: Earth Surface Processes and Landforms, v. 43, p. 2562–2577.

 

Physical vs. Ecological Drivers of Channel Change

Identifying the relative contributions of physical and ecological processes to channel evolution remains a substantial challenge in fluvial geomorphology. We used a 74-year aerial photographic record of the Hoh, Queets, Quinault, and Elwha Rivers, Olympic National Park, Washington, U.S.A., to investigate whether physical or trophic-cascade-driven ecological factors—excessive elk impacts after wolves were extirpated a century ago—are the dominant controls on channel planform of these gravel-bed rivers. We found that channel width and braiding show strong relationships with recent flood history; all four rivers have widened significantly in recent decades, consistent with increased flood activity since the 1970s. Channel planform also reflects sediment-supply changes, e.g., response of the Elwha River to a landslide. We surmised that the Hoh River, which shows a unique multi-decadal trend toward greater braiding, is adjusting to increased sediment supply associated with rapid glacial retreat. However, we inferred no correspondence between channel evolution and elk abundance, suggesting that in this system effects of the wolf-driven trophic cascade are subsidiary to physical controls on channel morphology. Our examinations of stage–discharge history, historical maps, photographs, and descriptions, and empirical geomorphic thresholds do not support a previous conceptual model that these rivers underwent a fundamental geomorphic transition resulting from large elk populations in the early 20th century. These findings differ from previous interpretations of Olympic National Park river dynamics, and also contrast with previous findings in Yellowstone National Park.

East, A.E., Jenkins, K.J., Happe, P.J., Bountry, J.A., Beechie, T.J., Mastin, M.C., Sankey, J.B., and Randle, T.J., 2017, Channel-planform evolution in four rivers of Olympic National Park, Washington, U.S.A.: the roles of physical drivers and trophic cascades: Earth Surface Processes and Landforms, v. 42, p. 1011–1032.

East, A.E., Jenkins, K.J., Happe, P.J., Bountry, J.A., Beechie, T.J., Mastin, M.C., Sankey, J.B., and Randle, T.J., 2018, Reply to “Wolf-triggered trophic cascades and stream channel dynamics in Olympic National Park: a comment on East et al. (2017)”: Earth Surface Processes and Landforms, doi:10.1002/esp.4288.

 

Landscape Evolution in the Colorado River Ecosystem

Since 2003, I have been studying connectivity among fluvial, aeolian, and hillslope processes in the Colorado River corridor, southwestern USA. Since 1963, Glen Canyon Dam operations have substantially altered river flow and fluvial sediment supply in the Colorado River corridor through Grand Canyon National Park. My work focuses on the role of aeolian sand in ecosystem development and archaeological-site preservation, and the influence of controlled floods on aeolian sand supply and transport in the river corridor. Because fluvial and aeolian sedimentary systems are strongly coupled there, the loss of fluvial sandbars in the dammed river reduces the supply of windblown sand to aeolian dunes above the high water line. Where aeolian sand supply has been lost in post-dam time, the ecosystem changes as biologic soil crust and vegetation replace formerly open sand. This study, which included making comparisons between Grand Canyon and a less regulated reach of the Colorado River upstream in Cataract Canyon, Utah, is the first study to show that river regulation by dams affects the evolution of aeolian landscapes up above the river's high water line, demonstrating a newly recognized human impact on arid environments.

East, A.E., Collins, B.D., Sankey, J.B., Corbett, S.C., Fairley, H.C., and Caster, J., 2016, Conditions and processes affecting sand resources at archeological sites in the Colorado River corridor below Glen Canyon Dam: U.S. Geological Survey Professional Paper 1825, 104 pp., http://dx.doi.org/10.3133/pp1825

Sankey, J.B., Kasprak, A., Caster, J., East, A.E, and Fairley, H.C., 2018, The response of source-bordering aeolian dunefields to sediment-supply changes, 1. Effects of wind variability and river-valley morphodynamics: Aeolian Research, v. 32, p. 228–245.

Sankey, J.B., Caster, J., Kasprak, A., and East, A.E., 2018, The response of source-bordering aeolian dune fields to sediment-supply changes, 2. Controlled floods of the Colorado River in Grand Canyon, Arizona, USA: Aeolian Research, Aeolian Research, v. 32, p. 154–169.

Sankey, J.B., and Draut, A.E., 2014, Gully annealing by aeolian sediment: field and remote-sensing investigation of aeolian-hillslope-fluvial interactions, Colorado River corridor, Arizona, USA: Geomorphology, v. 230, p. 68-80.

Draut, A.E., 2012, Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA: Journal of Geophysical Research—Earth Surface, v. 117, F02022, doi:10.1029/2011JF002329

Draut, A.E., and Rubin, D.M., 2008, The role of aeolian sediment in the preservation of archaeological sites in the Colorado River corridor, Grand Canyon, Arizona: USGS Professional Paper 1756, http://pubs.usgs.gov/pp/1756/

Draut, A.E., et al., 2008, Application of sedimentary-structure interpretation to geoarchaeological studies in the Colorado River corridor, Grand Canyon, Arizona, USA: Geomorphology, v. 101, p. 497-509.

 

Aeolian Landscape Stability

Constraining the processes governing aeolian landscape stability and associated windblown sediment transport is both an interesting research problem and essential for planning human occupation of arid lands. I have a new, ongoing project working with the Bureau of Land Management to quantify rates of sediment accumulation and characterize spatial variations in landscape stability in areas of the Mojave Desert, California, that are being considered for major expansions of solar-energy projects. This work is beginning in spring 2019 in earnest, so stay tuned for future updates.

Previously, I worked on an interesting aeolian-process study on the Navajo Nation. Native Americans of the southwestern U.S. live on ecologically sensitive arid lands with limited resources. On the 65,000 km2 Navajo Nation, one third of the land surface is covered by aeolian sand dunes. Higher temperatures, reduced precipitation, and the spread of exotic plants are transforming the landscape, negatively impacting residents, many of whom live a traditional, subsistence lifestyle. During the past 14 years of drought, wind-blown sand mobility has increased appreciably and destabilized ground surfaces, endangering housing and transportation, jeopardizing grazing lands, and impacting air quality. I worked with the USGS Navajo Nation Land Use Project led by Margaret Hiza Redsteer to study processes that are rapidly altering these lands. We studied how aeolian sand transport, vegetation abundance and assemblage, and stabilizing biologic soil crust vary with seasonal and longer-term climatic changes and livestock use.

Draut, A.E., Redsteer, M.H., and Amoroso, L., 2012, Vegetation, substrate, and aeolian sand transport at Teesto Wash, Navajo Nation, 2009–12: U.S. Geological Survey Scientific Investigations Report 2012-5095, 78 p., http://pubs.usgs.gov/sir/2012/5095/.

Draut, A.E., Redsteer, M.H., and Amoroso, L., 2012, Recent seasonal variations in arid landscape cover and aeolian sand mobility, Navajo Nation, southwestern U.S., in Giosan, L., and others, eds., Climate, Landscapes and Civilizations: American Geophysical Union Monograph 198, p. 51–60.

 

Sedimentary, Tectonic, and Geochemical Processes of Active Margins

I have worked on both modern and ancient tectonic and sedimentary processes along active margins. Currently, my work in this area focuses on the Queen Charlotte Fault, the plate boundary between the Pacific and North American plates along southeastern Alaska. This work is ongoing thanks to great new data sets (multibeam bathymetric and shallow seismic-reflection data) collected in 2015 and 2016... stay tuned. Much of my work in the ancient record dealt with island-arc magmatism, which is thought to be a primary way to generate continental crust. Origin of continental crust is a contentious issue, as scientists must reconcile geochemical disparities between most arc volcanism and bulk continental crust. Studying evolution of modern and ancient accreted arc terranes contributes new understanding into arc-continent collision processes, with implications for understanding more about these important systems - both their role in forming continental crust, and, from a geohazards perspective, their ability to generate large tsunamigenic earthquakes. I have worked in accreted arc terranes of Ireland, Alaska, and Taiwan, studying geochemical and sedimentary processes that accompany arc-continent collision, and also worked around the Aleutian arc studying sedimentary and tectonic evolution of the forearc evident from sedimentary basin development. By better understanding the structural history and sedimentary environments of Alaska and the Aleutians, we aim to clarify the risk of great earthquakes and tsunami generation there.

Draut, A.E., and Clift, P.D., 2013, Differential preservation in the geologic record of island-arc sedimentary and tectonic processes: Earth-Science Reviews, v. 116, p. 57–84.

Ryan, H.F., Draut, A.E., Scholl, D.W., and Keranen, K., 2012, Influence of the Amlia fracture zone on the evolution of the Aleutian Terrace forearc basin, central Aleutian subduction zone: Geosphere, v. 8, no. 6, p. 1254–1273, doi:10.1130/GES00815.1.

Draut, A.E., Clift, P.D., Amato, J.M., Blusztajn, J., and Schouten, H., 2009, Arc-continent collision and the formation of continental crust - a new geochemical and isotopic record from the Ordovician Tyrone Igneous Complex, Ireland: Journal of the Geological Society, London, v. 166, p. 485 - 500.

Draut, A.E., Clift, P.D., and Scholl, D.W., eds., 2008, Formation and applications of the sedimentary record in arc collision zones. GSA Special Paper 436, collection of 18 papers.

Draut, A.E., and Clift, P.D., 2006, Sedimentary processes in modern and ancient oceanic arc settings - evidence from the Jurassic Talkeetna Formation of Alaska and the Mariana and Tonga arcs, western Pacific: Journal of Sedimentary Research, v. 76, p. 493 - 514.

Clift, P.D., Draut, A.E., Kelemen, P.B., Blusztajn, J., and Greene, A., 2005, Stratigraphic and geochemical evolution an oceanic arc upper crustal section—the Jurassic Talkeetna Volcanic Formation, south-central Alaska: Geological Society of America Bulletin, v. 117, p. 902–925, DOI: 10.1130/B25638. 

Draut, A.E., and Clift, P.D., 2001, Geochemical evolution of arc magmatism during arc-continent collision, South Mayo, Ireland: Geology, v. 29, p. 543-546.

 

Terrestrial Sediment Effects on Coral Reef Ecosystems

Terrestrial sediment input to the coastal ocean can threaten coral-reef ecosystems. In Hawaii, sedimentation on nearshore reefs is a concern because changing land-use patterns (urbanization, agricultural practices, and nonnative species expansion) can increase sediment entering coastal waters, inhibiting photosynthesis and smothering corals. Working with the USGS Coral Reefs Project in 2005 and 2006, I collected sediment cores in Hanalei Bay and used them to trace flood sediment delivery. We found that winter flood sediment stays in the bay for months after a large flood event if the wave energy is not great enough to flush sediment out of the bay, highlighting an important difference between hydroclimatic processes in tropical vs. temperate zones. Whereas in temperate regions (like the California coast) floods and wave energy usually coincide, which rapidly reworks flood sediment near shore, in tropical regions the deposition and reworking of flood sediment are often seasonally decoupled. When tropical flood sediment stays near shore for months during summer low wave energy, this can harm coral reefs, particularly if sediment influx increases (land use changes) and/or climate change brings more summer rain to Hawaii, as some models of future climate project.

Draut, A.E., Bothner, M.H., Field, M.E., Reynolds, R.L., Cochran, S.A., Logan, J.B., Storlazzi, C.D., and Berg, C.J., 2009, Supply and dispersal of seasonal flood sediment from a steep, tropical watershed - Hanalei Bay, Kauai, Hawaii, USA: Geological Society of America Bulletin, v. 121, p. 574 - 585.

Storlazzi, C.D., Field, M.E., Bothner, M.H., Presto, M.K., and Draut, A.E., 2009, Sedimentation processes in a coral reef embayment: Hanalei Bay, Kauai: Marine Geology, v. 264, p. 140-151.