Matching Items (10)
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Description
Worldwide, rivers and streams make up dense, interconnected conveyor belts of sediment– removing carved away earth and transporting it downstream. The propensity of alluvial river beds to self-organize into complex trains of bedforms (i.e. ripples and dunes) suggests that the associated fluid and sediment dynamics over individual bedforms are an

Worldwide, rivers and streams make up dense, interconnected conveyor belts of sediment– removing carved away earth and transporting it downstream. The propensity of alluvial river beds to self-organize into complex trains of bedforms (i.e. ripples and dunes) suggests that the associated fluid and sediment dynamics over individual bedforms are an integral component of bedload transport (sediment rolled or bounced along the river bed) over larger scales. Generally speaking, asymmetric bedforms (such as alluvial ripples and dunes) migrate downstream via erosion on the stoss side of the bedform and deposition on the lee side of the bedform. Thus, the migration of bedforms is intrinsically linked to the downstream flux of bedload sediment. Accurate quantification of bedload transport is important for the management of waters, civil engineering, and river restoration efforts. Although important, accurate qualification of bedload transport is a difficult task that continues t elude researchers. This dissertation focuses on improving our understanding and quantification of bedload transport on the two spatial scales: the bedform scale and the reach (~100m) scale.

Despite a breadth of work investigating the spatiotemporal details of fluid dynamics over bedforms and bedload transport dynamics over flat beds, there remains a relative dearth of investigations into the spatiotemporal details of bedload transport over bedforms and on a sub-bedform scale. To address this, we conducted two sets of flume experiments focused on the two fundamental regions of flow associated with bedforms: flow separation/reattachment on the lee side of the bedform (Chapter 1; backward facing-step) and flow reacceleration up the stoss side of the next bedform (Chapter 2; two-dimensional bedform). Using Laser and Acoustic Doppler Velocimetry to record fluid turbulent events and manual particle tracking of high-speed imagery to record bedload transport dynamics, we identified the existence and importance of “permeable splat events” in the region proximal to flow reattachment.

These coupled turbulent and sediment transport events are integral to the spatiotemporal pattern of bedload transport over bedforms. Splat events are localized, high magnitude, intermittent flow features in which fluid impinges on the bed, infiltrates the top portion of bed, and then exfiltrates in all directions surrounding the point of impingement. This initiates bedload transport in a radial pattern. These turbulent structures are primarily associated with quadrant 1 and 4 turbulent structures (i.e. instantaneous fluid fluctuations in the streamwise direction that bring fluid down into the bed in the case of quadrant 1 events, or up away from the bed in the case of quadrant 4 events) and generate a distinct pattern of bedload transport compared to transport dynamics distal to flow reattachment. Distal to flow reattachment, bedload transport is characterized by relatively unidirectional transport. The dynamics of splat events, specifically their potential for inducing significant magnitudes of cross-stream transport, has important implications for the evolution of bedforms from simple, two dimensional features to complex, three-dimensional features.

New advancements in sonar technology have enabled more detailed quantification of bedload transport on the reach scale, a process paramount to the effective management of rivers with sand or gravel-dominated bed material. However, a practical and scalable field methodology for reliably estimating bedload remains elusive. A popular approach involves calculating transport from the geometry and celerity of migrating bedforms, extracted from time-series of bed elevation profiles (BEPs) acquired using echosounders. Using two sets of repeat multibeam sonar surveys from the Diamond Creek USGS gage station in Grand Canyon National Park with large spatio-temporal resolution and coverage, we compute bedload using three field techniques for acquiring BEPs: repeat multi-, single-, and multiple single-beam sonar. Significant differences in flux arise between repeat multibeam and single beam sonar. Mulitbeam and multiple single beam sonar systems can potentially yield comparable results, but the latter relies on knowledge of bedform geometries and flow that collectively inform optimal beam spacing and sampling rate. These results serve to guide design of optimal sampling, and for comparing transport estimates from different sonar configurations.
ContributorsLeary, Kate (Author) / Schmeeckle, Mark W (Thesis advisor) / Whipple, Kelin X (Thesis advisor) / Heimsath, Arjun (Committee member) / Walker, Ian (Committee member) / Arrowsmith, Ramon (Committee member) / Arizona State University (Publisher)
Created2018
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Human-environment interactions in aeolian (windblown) systems has focused research on<br/>human’s role in causing and aiding recovery from natural and anthropogenic disturbance. There<br/>is room for improvement in understanding the best methods and considerations for manual<br/>coastal foredune restoration. Furthermore, the extent to which humans play a role in changing the<br/>shape and surface

Human-environment interactions in aeolian (windblown) systems has focused research on<br/>human’s role in causing and aiding recovery from natural and anthropogenic disturbance. There<br/>is room for improvement in understanding the best methods and considerations for manual<br/>coastal foredune restoration. Furthermore, the extent to which humans play a role in changing the<br/>shape and surface textures of quartz sand grains is poorly understood. The goal of this thesis is<br/>two-fold: 1) quantify the geomorphic effectiveness of a multi-year manually rebuilt foredune and<br/>2) compare the shapes and microtextures on disturbed and undisturbed quartz sand grains. For<br/>the rebuilt foredune, uncrewed aerial systems (UAS) were used to survey the site, collecting<br/>photos to create digital surface models (DSMs). These DSMs were compared at discrete<br/>moments in time to create a sediment budget. Water levels and cross-shore modeling is also<br/>considered to predict the decadal evolution of the site. In the two years since rebuilding, the<br/>foredune has been stable, but not geomorphically resilient. Modeling shows landward foredune<br/>retreat and beach widening. For the quartz grains, t-testing of shape characteristics showed that<br/>there may be differences in the mean circularity between grains from off-highway vehicle and<br/>non-riding areas. Quartz grains from a variety of coastal and inland dunes were imaged using a<br/>scanning electron microscopy to search for evidence of anthropogenically-induced<br/>microtextures. On grains from Oceano Dunes in California, encouraging textures like parallel<br/>striations, grain fracturing, and linear conchoidal fractures provide exploratory evidence of<br/>anthropogenic microtextures. More focused research is recommended to confirm this exploratory<br/>work.

ContributorsMarvin, Michael Colin (Author) / Walker, Ian (Thesis director) / Dorn, Ron (Committee member) / Schmeeckle, Mark (Committee member) / School of Geographical Sciences and Urban Planning (Contributor, Contributor, Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Antonin Artaud was one of the first internationally recognized writers to introduce the indigenous Tarahumara (Rarámuri) of Northwest Mexico to the world. In a series of publications based on his experiences with the tribe in 1936, Artaud left a vast visual legacy that positioned the Tarahumara within a powerful regime

Antonin Artaud was one of the first internationally recognized writers to introduce the indigenous Tarahumara (Rarámuri) of Northwest Mexico to the world. In a series of publications based on his experiences with the tribe in 1936, Artaud left a vast visual legacy that positioned the Tarahumara within a powerful regime of representation, one that framed them within a mixed landscape of exoticism, primitivism, and peyote-inspired mysticism. This paper focuses on these literary works and interrogates the veracity of Artaud’s experiences and observations among the “pure race.” Drawing on the ethnographic record of the twentieth century and anthropological field research, it is my intention to reveal Artaud’s ability to fabricate, exaggerate, and embellish “the truth” which he so desperately desired to understand.

ContributorsKrutak, Lars (Author)
Created2014
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When André Breton went to Mexico in 1938, he saw the photographs of Manuel Álvarez Bravo, took a set of them back with him to France and, the following year, published and exhibited them as part of his espousal of Mexico as “the surrealistic place par excellence.” That is the

When André Breton went to Mexico in 1938, he saw the photographs of Manuel Álvarez Bravo, took a set of them back with him to France and, the following year, published and exhibited them as part of his espousal of Mexico as “the surrealistic place par excellence.” That is the first reason why the work of Álvarez Bravo cannot be overlooked in the broader context of Surrealism. This circumstance, often cited, has rarely been analyzed in any depth and part of the aim of this essay is to undertake that analysis.

ContributorsWalker, Ian (Author)
Created2014
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Description

In New York in 1944, the Surrealist magazine VVV published two photographs of the Arizona desert by Frederick Sommer. They are radical images in their minimalism and intensity of attention to (apparently) very little.

Sommer’s immediate connection was with Max Ernst, who saw these pictures when he visited Arizona in 1943.

In New York in 1944, the Surrealist magazine VVV published two photographs of the Arizona desert by Frederick Sommer. They are radical images in their minimalism and intensity of attention to (apparently) very little.

Sommer’s immediate connection was with Max Ernst, who saw these pictures when he visited Arizona in 1943. Later, when Ernst came to live at Sedona, the two men influenced each other’s work. Yves Tanguy also visited in 1951 and J. T. Soby suggested that the ‘breathless congestion of boulders, pebbles and bones’ in Tanguy’s last paintings derive from his experience of the desert as viewed through Sommer’s photographs.

Even in Europe, where Surrealism was predominantly urban, there had been an interest in the extreme landscapes of desert or jungle. But while Salvador Dali transformed rock forms into bodies, the challenge of the desert as Sommer depicted it was that no such transformation was possible. In addition, there was a Surrealist fascination with the "terrain vague"—land which is formless, void of composition—and it would be intriguing to extend the idea to Sommer’s desert pictures, which equally irritate the eye with their apparent lack of organization and focus.

It was Sommer’s meeting with Edward Weston that led to his use of a 10 x 8” camera to create the intensity of these pictures. But Sommer’s sense of the violence of the desert was at odds with the positive way it was depicted by Weston or Ansel Adams and his work was written out of photographic history for a long time. It’s no accident that it was rediscovered in the 1970s, when the myth of the American West was subjected to a severe critique and it’s intriguing to also place Sommer’s photographs in a lineage that goes back to Timothy O’Sullivan and forward to Richard Misrach.

Sommer’s work stands then at the intersection between the photography of the American West and Surrealism - between Edward Weston and Max Ernst. But it is also quite unlike either and, in their unflinching gaze at a subject that is both intense and empty, Sommer’s Arizona Landscapes profoundly undermine the conventions of vision.

ContributorsWalker, Ian (Author)
Created2008
The Journal of Surrealism and the Americas: Vol. 2 No. 2 (2008)
Description

The Journal of Surrealism and the Americas: Vol. 2 No. 2 (2008) - Table of Contents

“Surrealism and Photography: Introduction” by Wendy Grossman, p. i-iv.

“‘Surrealistic and disturbing’: Timothy O’Sullivan as Seen by Ansel Adams in the 1930s” by Britt Salvesen, p. 162-179. 

“‘As if one’s eyelids had been cut away’: Frederick Sommer’s Arizona

The Journal of Surrealism and the Americas: Vol. 2 No. 2 (2008) - Table of Contents

“Surrealism and Photography: Introduction” by Wendy Grossman, p. i-iv.

“‘Surrealistic and disturbing’: Timothy O’Sullivan as Seen by Ansel Adams in the 1930s” by Britt Salvesen, p. 162-179. 

“‘As if one’s eyelids had been cut away’: Frederick Sommer’s Arizona Landscapes” by Ian Walker, p. 180-208.

“Clarence John Laughlin, Regionalist Surrealist” by Lewis Kachur, p. 209-226.

“A Swimmer Between Two Worlds: Francesca Woodman’s Maps of Interior Space” by Katharine Conley, p. 227-252. 

“Remembering Anne D’Harnoncourt” by Valery Oisteanu, p. 253.

“The 1930s: The Making of the ‘New Man’” by Julia Pine, p. 254-258.

“Beyond Bridges: The Cinema of Jean Rouch” by Robert McNab, p. 259-262.

“Review of Kirby Olson, ‘Andrei Codrescu and the Myth of America’” by Éva Forgács, p. 263-267.

“Review of Sally Price, 'Paris Primitive: Jacques Chirac’s Museum on the Quai Branly’” by Kate Duncan, p. 268-272. 

 

ContributorsGrossman, Wendy A. (Author) / Salvesen, Britt (Author) / Walker, Ian (Author) / Kachur, Lewis (Author) / Conley, Katharine (Author) / Oisteanu, Valery (Author) / Pine, Julia (Author) / McNab, Robert Donald (Author) / Forgács, Éva (Author) / Duncan, Kate (Author)
Created2008
The Journal of Surrealism and the Americas: Vol. 8 No. 1 (2014)
Description

The Journal of Surrealism and the Americas: Vol. 8 No. 1 (2014) - Table of Contents

“Manuel Álvarez Bravo: Surrealism and Documentary Photography” by Ian Walker, p. 1-27. 

“(Sur)real or Unreal?: Antonin Artaud in the Sierra Tarahumara of Mexico” by Lars Krutak, p. 28-50. 

“Surrealist Views, American Landscapes: Notes on Wolfgang Paalen’s Ruin

The Journal of Surrealism and the Americas: Vol. 8 No. 1 (2014) - Table of Contents

“Manuel Álvarez Bravo: Surrealism and Documentary Photography” by Ian Walker, p. 1-27. 

“(Sur)real or Unreal?: Antonin Artaud in the Sierra Tarahumara of Mexico” by Lars Krutak, p. 28-50. 

“Surrealist Views, American Landscapes: Notes on Wolfgang Paalen’s Ruin Gazing” by Kent L. Dickson, p. 51-73.

“‘Don’t Forget I Come From the Tropics’: Reconsidering the Surrealist Sculpture of Maria Martins” by Michael R. Taylor, p. 74-89.

‘Le centre du milieu’: Matta and the Exploding Dome” by Denise Birkhofer, p. 90-104. 

“Edward James and Plutarco Gastélum in Xilita: Critical Paranoia in the Mexican Jungle” by Irene Herner, p. 105-123.

“Review of Ellen Landau, ‘Mexico and American Modernism’” by Luis M. Castañeda, p. 124-126. 

“‘Surrealist Ghosts and Spectrality in Surrealist Ghostliness’ by Katharine Conley” by Martine Antle, p. 127-129. 

“Review of Roger Rothman, ‘Tiny Surrealism: Salvador Dalí and the Aesthetics of the Small’” by Jonathan S. Wallis, p. 130-135.

“Review of ‘Late Surrealism’: The Menil Collection, May 24- August 25, 2013” by Rachel Hooper, p. 136-139.

ContributorsWalker, Ian (Author) / Krutak, Lars (Author) / Dickson, Kent (Author) / Taylor, Michael Richard (Author) / Herner, Irene (Author) / Castañeda, Luis M. (Author) / Antle, Martine (Author) / Wallis, Jonathan S. (Author) / Hooper, Rachel (Author)
Created2014
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Coastal dunes are dynamic landforms that provide the first defense for sea-level rise and coastal flooding. Coastal dunes depend on vegetation to trap and store sediment, which alters beach-dune sediment budgets and foredune morphology. Invasive vegetation species change these patterns and alter how the system responds to both littoral and

Coastal dunes are dynamic landforms that provide the first defense for sea-level rise and coastal flooding. Coastal dunes depend on vegetation to trap and store sediment, which alters beach-dune sediment budgets and foredune morphology. Invasive vegetation species change these patterns and alter how the system responds to both littoral and aeolian processes. Dynamic restoration is a growing practice whereby plant communities are modified to enhance aeolian processes and help return coastal dune ecosystems to a more ‘natural’ state of ecosystem structure and function. A portion of the foredune system at the Lanphere Dunes in the Humboldt Bay National Wildlife Refuge (HBNWR), near Arcata in northern California was targeted for dynamic restoration. The invasive plant species Ammophila arenaria (European beach grass) was removed in August 2015, while native vegetation treatments consisting of combinations of a dune mat forb assemblage and the dune grass Elymus mollis (Sea Lyme-grass) were planted over the summer and over the winter of 2016-17. Four different vegetation regimes were studied consisting of a control plot of A. arenaria two plots of exclusively Dune mat and E. mollis, and then a plot that is the combination if Dune mat and E. mollis. This restoration presented the opportunity to study the patterns of vegetation re-establishment and the related responses in sedimentation and morphological adjustment of the foredune system at both the landform and vegetation plot scales. Bi-annual terrestrial laser scanning surveys and cross-shore transects were used to calculate volumes of sediment change, distinguish patterns of sediment erosion/deposition and discern geomorphic change within different plant cover types. Results suggest that the Dune mat-E. mollis assemblage was most effective a trapping sediment with 96.9% of the plot experiencing deposition over the 17-month observation period, to a spatially averaged depth of +0.16m. During the study, the Dune mat treatment site experienced a landward flattening of its crest and considerable erosion of up to -0.5m around the plants, resulting in a normalized volumetric change of -0.139 m3 m-2. The E. mollis site experienced considerable sediment bypassing on the stoss slope and deposition on the lee slope of the foredune, resulting in accumulation at the toe of the lee slope of +0.6m while base of the lee slope moved 4m landwards. Site morphodynamics and sediment budgets were also influenced by changes in vegetation density and recovery from storm erosion. Longer terms studies could be conducted to investigate responses to vegetation disturbances over a longer temporal scale.
ContributorsHuck, Rosemary Alice (Author) / Walker, Ian (Thesis director) / Dorn, Ronald (Committee member) / Historical, Philosophical & Religious Studies (Contributor) / School of Geographical Sciences and Urban Planning (Contributor, Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
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Sediment transport by atmospheric flows shapes landscapes on Earth and other planets. Improving the ability to quantify and predict sand transport by windblown (aeolian) processes has important implications for managing erosion, land degradation, desertification, dust emissions, air quality, and other climate change hazards and risks. Despite progress since Bagnold's seminal

Sediment transport by atmospheric flows shapes landscapes on Earth and other planets. Improving the ability to quantify and predict sand transport by windblown (aeolian) processes has important implications for managing erosion, land degradation, desertification, dust emissions, air quality, and other climate change hazards and risks. Despite progress since Bagnold's seminal works in the 1930s, the most frequently used aeolian sand transport equations show discrepancies between predicted and observed transport rates upwards of 300%. Differences of this magnitude strongly support re-examining how fundamental physical aeolian processes are expressed in predictive equations. Wind tunnel experiments using a Particle Imaging Velocimetry/Particle Tracking Velocimetry (PIV/PTV) system with a high-speed camera and high-powered laser were conducted to visualize fluid motions and sand particle trajectories to provide simultaneous measurements of wind flow and sand transport to re-examine the fundamental physical relationships between flow dynamics, sediment motions, and bedform development. The first experiment of this dissertation focuses on the characteristics of near-surface sand transport in the saltation cloud. From PTV particle trajectories, mean particle velocities appear independent of freestream wind speed, while velocity distribution characteristics (such as modality) and particle concentration intermittency vary with increasing sand transport. Particle trajectories from rippled bed runs show evidence of local slope influence on near-bed particle vectors. The second experiment used manual sand grain tracking to quantify particle-bed splash interactions. Results highlight that common rebound and ejecta functions do not sufficiently represent aeolian saltation splash events. Data indicate a shadowing effect of ripples, suggesting feedback between the saltation cloud, splash events, and bedform migration. The third experiment used dual PIV/PTV analysis to quantify fluid-particle interactions and compare sand concentrations with fluid stresses and turbulence characteristics through the saltation cloud. Results show that increased saltation leads to the disappearance of the constant fluid stress region, changes in aerodynamic roughness length, and increases in turbulence intensities. Leveraging technology advancements and multiple analysis methods, these results provide new, detailed information on the relationships between flow dynamics, sediment motions, and the presence of ripple bedforms. These novel empirical data illustrate some needed corrections to the theoretical and numerical frameworks for quantifying aeolian sand transport.
ContributorsKelley, Madeline (Author) / Schmeeckle, Mark (Thesis advisor) / Walker, Ian (Thesis advisor) / Dorn, Ron (Committee member) / Swann, Christy (Committee member) / Arizona State University (Publisher)
Created2023