Thesis (Ph. D.)--Columbia University, 1936. / Vita. Includes bibliographical references (p. 42).

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). One col. map in pocket. Includes bibliographical references. Also available via the World Wide Web.

Thesis (Ph. D.)--Columbia University, 1936. / Vita. Bibliography: p. 42.

abstract: Fluctuating flow releases on regulated rivers destabilize downstream riverbanks, causing unintended, unnatural, and uncontrolled geomorphologic changes. These flow releases, usually a result of upstream hydroelectric dam operations, create manmade tidal effects that cause significant environmental damage; harm fish, vegetation, mammal, and avian habitats; and destroy riverbank camping and boating areas. This work focuses on rivers regulated by hydroelectric dams and have banks formed by sediment processes. For these systems, bank failures can be reduced, but not eliminated, by modifying flow release schedules. Unfortunately, comprehensive mitigation can only be accomplished with expensive rebuilding floods which release trapped sediment back into the river. The contribution of this research is to optimize weekly hydroelectric dam releases to minimize the cost of annually mitigating downstream bank failures. Physical process modeling of dynamic seepage effects is achieved through a new analytical unsaturated porewater response model that allows arbitrary periodic stage loading by Fourier series. This model is incorporated into a derived bank failure risk model that utilizes stochastic parameters identified through a meta-analysis of more than 150 documented slope failures. The risk model is then expanded to the river reach level by a Monte Carlos simulation and nonlinear regression of measured attenuation effects. Finally, the comprehensive risk model is subjected to a simulated annealing (SA) optimization scheme that accounts for physical, environmental, mechanical, operations, and flow constraints. The complete risk model is used to optimize the weekly flow release schedule of the Glen Canyon Dam, which regulates flow in the Colorado River within the Grand Canyon. A solution was obtained that reduces downstream failure risk, allows annual rebuilding floods, and predicts a hydroelectric revenue increase of more than 2%. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2010

abstract: The Himalaya are the archetypal example of a continental collision belt, formed by the ongoing convergence between India and Eurasia. Boasting some of the highest and most rugged topography on Earth, there is currently no consensus on how climatic and tectonic processes have combined to shape its topographic evolution. The Kingdom of Bhutan in the eastern Himalaya provides a unique opportunity to study the interconnections among Himalayan climate, topography, erosion, and tectonics. The eastern Himalaya are remarkably different from the rest of the orogen, most strikingly due to the presence of the Shillong Plateau to the south of the Himalayan rangefront. The tectonic structures associated with the Shillong Plateau have accommodated convergence between India and Eurasia and created a natural experiment to test the possible response of the Himalaya to a reduction in local shortening. In addition, the position and orientation of the plateau topography has intercepted moisture once bound for the Himalaya and created a natural experiment to test the possible response of the range to a reduction in rainfall. I focused this study around the gently rolling landscapes found in the middle of the otherwise extremely rugged Bhutan Himalaya, with the understanding that these landscapes likely record a recent change in the evolution of the range. I have used geochronometric, thermochronometric, and cosmogenic nuclide techniques, combined with thermal-kinematic and landscape evolution models to draw three primary conclusions. 1) The cooling histories of bedrock samples from the hinterland of the Bhutan Himalaya show a protracted decrease in erosion rate from the Middle Miocene toward the Pliocene. I have attributed this change to a reduction in shortening rates across the Himalayan mountain belt, due to increased accommodation of shortening across the Shillong Plateau. 2) The low-relief landscapes of Bhutan were likely created by backtilting and surface uplift produced by an active, blind, hinterland duplex. These landscapes were formed during surface uplift, which initiated ca. 1.5 Ma and has totaled 800 m. 3) Millennial-scale erosion rates are coupled with modern rainfall rates. Non-linear relationships between topographic metrics and erosion rates, suggest a fundamental difference in the mode of river incision within the drier interior of Bhutan and the wetter foothills. / Dissertation/Thesis / Ph.D. Geological Sciences 2014

Esta pesquisa apresenta um retrato da dispersão urbana que ocorre na região da Macrometrópole de São Paulo sobre a ótica da apropriação do relevo. Quais são os compartimentos de relevo que estão sendo ocupados pelas peças urbanas que se dispersam sobre a área anteriormente utilizada pelos usos relativos ao mundo rural, e em que medida essas peças urbanas residenciais, industriais ou mistas, diferem da morfologia de suas congêneres da cidade compacta, e as consequências ambientais decorrentes dessa forma de apropriação. A partir de uma proposta metodológica de abordagem estratégica do relevo na escala regional, e tendo como base categorias de análise da geomorfologia, este trabalho identifica no processo de dispersão, além de uma tendência de ocupação indiscriminada, e sem critérios ambientalmente claros, de todos os tipos de compartimento de relevo, inclusive daqueles que se pode considerar como compartimentos ambientais estruturantes da paisagem regional para a regulação dos processos naturais e de sua ocorrência não conflituosa com os usos urbanos. Essa ocupação dispersa, que impacta esses compartimentos ambientais estruturantes, é realizada tanto pelas camadas de alta e de baixa renda, como também pelos usos industriais e de comércio atacadista, embora esses grupos apresentem predominância em vetores de dispersão diferentes. / This research presents a portrait of the urban sprawl that occurs in the large metropolitan area of São Paulo, in view of the allocation of relief. Which relief sectors are occupied by urban works that disperse over the region formerly used by the rural area, and to what extent these residential, industrial or mixed urban works differ from the morphology of its equivalents in a compact city, and the environmental consequences resulting from this form of allocation. From a methodological proposal for a strategic approach to relief on a regional scale, and based on analytical categories of geomorphology, this paper identifies the dispersion process and a trend of indiscriminate occupation, without clear environmental criteria, of all types of relief sectors, including those that can be considered as environmental zones of regional landscape designated for the regulation of natural processes and their occurrence without conflict with urban uses. This dispersed occupation, which impacts these environmental zones is performed by both levels of high and low income, but also by industrial uses and wholesale trade, although these groups predominate in different dispersal vectors.

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<p> Sand levels were monitored at five southern California beaches for periods of 3 to 15 years, spanning a total of 18 km alongshore. Every 3 months, GPS equipped vehicles measured sand elevations on cross-shore transects from the backbeach to 8 m depth, with 100 m alongshore resolution. Subaerial observations were collected monthly above the spring low-tide line. Wave buoys and a numerical model provided hourly wave estimates in 10 m depth at each site. </p><p> These observations show that beach profile shapes (depth versus cross-shore distance) evolve consistent with the equilibrium hypothesis: under steady wave conditions, evolution is toward a unique, wave condition dependent, equilibrium beach profile. Beaches far out of equilibrium change rapidly, and as equilibrium is approached they change ever more slowly. At the sandy regions, a simple equilibrium beach state model has skill >0.5 (Chapter 2, [Ludka et al., 2015]). </p><p> Repeated nourishments over multiple decades, costing hundreds of thousands of dollars, are a primary beach management strategy worldwide, but the wave-driven redistribution of nourishment sand is poorly understood. At four survey sites, 50,000-300,000 m</p><p>3 of imported sand was placed on the subaerial beach overalongshore spans between 300-1300 m. Wave conditions in the months after placement were similar at all sites, but the subaerial nourishment pads eroded and retreated landward at different rates. A pad built with native-sized sand washed offshore in the first few storms. In contrast, nourishments with coarser than native sand remained on the beach face for several years and protected shorelines during the significant wave attack of the 2015&ndash;16 El Ni&ntilde;o (Chapter 3, [Ludka et al., 2016]). These relatively resilient and coarse subaerial pads stretched alongshore in a pattern consistent with seasonally shifting, wave-driven alongshore currents. Natural gains and losses in the total sand volume budget, integrated spatially over each site, are sometimes larger than the nourishment contributions (Chapter 4, in prep for Coastal Engineering). </p>