Stefan Talke

Assistant Professor

Background

Ph.D., Civil and Environmental Engineering, University of California, Berkeley, 2005
M.S., Civil and Environmental Engineering, University of California, Berkeley, 2001
B.S., Mechanical Engineering, University of California, Berkeley, 1996

Dr. Talke’s research focuses on hydrodynamic processes and sediment transport in estuaries, rivers, and the ocean, using a combination of field research,data analysis, and modeling. He joined Portland State in September 2010 to analyze and model historical changes to tides in the Pacific Ocean, with a particular focus on west coast tidal stations such as Astoria.

A recent project at the University of Washington combined state-of the art thermal remote sensing with in-situ flow measurements to characterize turbulent mixing and coherent structures such as vortices and internal waves in a stratified tidal river. Results show how large-scale vortices bring elevated turbulent kinetic energy to the water surface. The research has implications for mixing processes (e.g., of sediment) and for air/water gas transfer (e.g., oxygen).

In Germany and the Netherlands, Dr. Talke measured and modeled sediment transport, focusing on how dredging-induced changes to depth altered tides, circulation, sediment trapping, and water quality in the Ems estuary. The increased oxygen depletion over the last 20 years was linked to anthropogenically-influenced increases in suspended sediment concentration.

Dr. Talke’s PhD thesis focused on tidal processes, turbulent mixing, and sediment transport in an intertidal area of S.F. Bay. Dr. Talke remains interested in small scale, turbulent mixing process, transport issues, and changes to coastal processes caused by climate and by local anthropogenic development.

Publications

33 entries « ‹ 2 of 4 › »

Orton, P M; Hall, T M; Talke, S A; Blumberg, A F; Georgas, N; Vinogradov, S

A validated tropical-extratropical flood hazard assessment for New York Harbor Journal Article

In: Journal of Geophysical Research: Oceans, 121 (12), pp. 8904–8929, 2016, ISSN: 2169-9291.

Abstract | Links | BibTeX

@article{JGRC:JGRC22000,
title = {A validated tropical-extratropical flood hazard assessment for New York Harbor},
author = {P. M. Orton and T. M. Hall and S. A. Talke and A. F. Blumberg and N. Georgas and S. Vinogradov},
url = {http://dx.doi.org/10.1002/2016JC011679},
doi = {10.1002/2016JC011679},
issn = {2169-9291},
year = {2016},
date = {2016-01-01},
journal = {Journal of Geophysical Research: Oceans},
volume = {121},
number = {12},
pages = {8904--8929},
abstract = {Recent studies of flood risk at New York Harbor (NYH) have shown disparate results for the 100 year storm tide, providing an uncertain foundation for the flood mitigation response after Hurricane Sandy. Here we present a flood hazard assessment that improves confidence in our understanding of the region's present-day potential for flooding, by separately including the contribution of tropical cyclones (TCs) and extratropical cyclones (ETCs), and validating our modeling study at multiple stages against historical observations. The TC assessment is based on a climatology of 606 synthetic storms developed from a statistical-stochastic model of North Atlantic TCs. The ETC assessment is based on simulations of historical storms with many random tide scenarios. Synthetic TC landfall rates and the final TC and ETC flood exceedance curves are all shown to be consistent with curves computed using historical data, within 95% confidence ranges. Combining the ETC and TC results together, the 100 year return period storm tide at NYH is 2.70 m (2.51–2.92 at 95% confidence), and Hurricane Sandy's storm tide of 3.38 m was a 260 year (170–420) storm tide. Deeper analyses of historical flood reports from estimated Category-3 hurricanes in 1788 and 1821 lead to new estimates and reduced uncertainties for their floods and show that Sandy's storm tide was the largest at NYH back to at least 1700. The flood exceedance curves for ETCs and TCs have sharply different slopes due to their differing meteorology and frequency, warranting separate treatment in hazard assessments.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

Jay, D A; Talke, S A; Hudson, A; Twardowski, M S

Estuarine turbidity maxima revisited: Instrumental approaches, remote sensing, modeling studies, and new directions Book Chapter

In: Ashworth, P J; Best, J L; Parsons, D R (Ed.): 68 , pp. 48-109, Elsevier, 1, 2015, ISBN: 9780444635297.

Abstract | Links | BibTeX

@inbook{Jay2015,
title = {Estuarine turbidity maxima revisited: Instrumental approaches, remote sensing, modeling studies, and new directions},
author = {D. A. Jay and S. A. Talke and A. Hudson and M. S. Twardowski},
editor = {P. J. Ashworth and J. L. Best and D. R. Parsons
},
doi = {10.1016/B978-0-444-63529-7.00004-3},
isbn = {9780444635297},
year = {2015},
date = {2015-11-23},
volume = {68},
pages = {48-109},
publisher = {Elsevier},
edition = {1},
series = {Developments in Sedimentology},
abstract = {Estuarine turbidity maxima (ETM) are zones of elevated sediment concentration that often occur in coastal plain, salt wedge, and river-dominated estuaries, where they influence the morphodynamic development, biogeochemical cycling, and contaminant redistribution of these systems. In this review, we examine recent advances in in situ and remote sensing techniques that can be used to improve our understanding of ETM, summarize recent theoretical and numerical modeling results, and define a series of research questions for the next decade. New acoustic configurations and instruments have the potential to address gaps in current observational capabilities and understanding, for example by providing better definition of vertical and horizontal sediment fluxes. Higher resolution (meter scale) ocean color remote sensing will allow visualization of small-scale features such as frontal boundaries and turbulent eddies in a manner that has not previously been possible. Increasing spectral resolution in ocean color images will allow development of improved algorithms to quantify sediment concentrations remotely. Additionally, the in-water optical techniques used to validate and develop algorithms for ocean color remote sensing can be adapted to estuaries, and are often amenable to rapid survey modes of deployment. In sum, these techniques provide opportunities to improve ETM models and theory.
Recent theoretical analyses of the profiles of velocity and suspended sediment concentration (SSC) in estuaries, integral analyses of ETM SSC conservation, and numerical model studies provide important insights into the response of ETM to external forcing and the mechanisms behind ETM particle trapping. However, existing studies produce more questions than answers. For example, it is still not possible to predict, except in very general terms, what trapping mechanisms will be active in different kinds of estuaries, and whether multiple ETM can be expected. The role of nonstationarity, extreme events, and climate change (e.g., mean sea level (MSL) rise and altered flow regimes) on ETM dynamics have not been systematically investigated, and feedbacks between anthropogenic influences and other system changes remain poorly understood. We summarize possible future analysis paths in terms of 10 research questions.},
keywords = {},
pubstate = {published},
tppubtype = {inbook}
}

Estuarine turbidity maxima (ETM) are zones of elevated sediment concentration that often occur in coastal plain, salt wedge, and river-dominated estuaries, where they influence the morphodynamic development, biogeochemical cycling, and contaminant redistribution of these systems. In this review, we examine recent advances in in situ and remote sensing techniques that can be used to improve our understanding of ETM, summarize recent theoretical and numerical modeling results, and define a series of research questions for the next decade. New acoustic configurations and instruments have the potential to address gaps in current observational capabilities and understanding, for example by providing better definition of vertical and horizontal sediment fluxes. Higher resolution (meter scale) ocean color remote sensing will allow visualization of small-scale features such as frontal boundaries and turbulent eddies in a manner that has not previously been possible. Increasing spectral resolution in ocean color images will allow development of improved algorithms to quantify sediment concentrations remotely. Additionally, the in-water optical techniques used to validate and develop algorithms for ocean color remote sensing can be adapted to estuaries, and are often amenable to rapid survey modes of deployment. In sum, these techniques provide opportunities to improve ETM models and theory.
Recent theoretical analyses of the profiles of velocity and suspended sediment concentration (SSC) in estuaries, integral analyses of ETM SSC conservation, and numerical model studies provide important insights into the response of ETM to external forcing and the mechanisms behind ETM particle trapping. However, existing studies produce more questions than answers. For example, it is still not possible to predict, except in very general terms, what trapping mechanisms will be active in different kinds of estuaries, and whether multiple ETM can be expected. The role of nonstationarity, extreme events, and climate change (e.g., mean sea level (MSL) rise and altered flow regimes) on ETM dynamics have not been systematically investigated, and feedbacks between anthropogenic influences and other system changes remain poorly understood. We summarize possible future analysis paths in terms of 10 research questions.

Moftakahri, H R; Jay, D A; Talke, S A; Schoellhamer, D H

Estimation of historic flows and sediment loads to San Francisco Bay, 1848-2011 Journal Article

In: Journal of Hydrology, 529 (3), pp. 1247-1261, 2015.

BibTeX

Orton, P M; Talke, S A; Jay, D A; Yin, L; Blumberg, A F; Georgas, N; Zhao, H; Roberts, H J; MacManus, K

Channel Shallowing as Mitigation of Coastal Flooding Journal Article

In: Journal of Marine Science and Engineering, 3 (3), pp. 654-673, 2015.

BibTeX

Talke, S A; Orton, P; Jay, D A

Increasing storm tides in New York Harbor, 1844-2013 Journal Article

In: Geophysical Research Letters, 41 (9), 2014.

Links | BibTeX

de Jonge, V N; Schuttelaars, H M; Beusekom, M.van J M; Talke, S A; de Swart, H E

The influence of channel deepening on estuarine turbidity dynamics, as exemplified by the Ems estuary Journal Article

In: Estuary, Coastal and Shelf Science, 139 , pp. 46-59, 2014.

Links | BibTeX

Devlin, A T; Jay, D A; Talke, S A; Zaron, E D

Can tidal perturbations associated with sea level variations in the western Pacific Ocean be used to understand future effects of tidal evolution? Journal Article

In: Ocean Dynamics, 64 (8), pp. 1093-1120, 2014.

Links | BibTeX

Talke, S A; Horner-Devine, A R; Chickadel, C C; Jessup, A T

Turbulent kinetic energy and coherent structures in a tidal river Journal Article

In: Journal of Geophysical Research: Oceans, 118 (12), pp. 6965-6981, 2013.

Links | BibTeX

Moftakahri, H R; Jay, D A; Talke, S A; Kukulka, T; Bromirski, P D

A novel approach to flow estimation in tidal rivers Journal Article

In: Water Resources Research, 49 (8), pp. 1-16, 2013.

Links | BibTeX

Talke, S A; Jay, D A

Nineteenth Century North American and Pacific Tides: Lost or just forgotten? Journal Article

In: Journal of Coastal Research, 29 (6a), pp. 118-127, 2013.

Links | BibTeX

33 entries « ‹ 2 of 4 › »

Courses

CE 361 – Fluid Mechanics

Credits: 4

Lecture and Laboratory: Properties of fluid; fluid statics; fluid dynamics; control volume and Reynolds transport theorem; conservation of mass, momentum and energy; differential analysis; rotational and irrotational flows, non-viscous and viscous flows, Navier Stokes equations. Lecture and laboratory.

Prerequisites: EAS 215 and Mth 256

CE 410/510 – TOP: Extreme Events in Environmental Water Resources

Credits: 4

Lecture: The flooding risk of coastal and inland communities depends on the total water level, which is influenced by factors such as land subsidence, sea-level rise, tidal variation, waves, tsunami exposure, river flows, storm surge, and other climate processes. In this course we will investigate both the physics and science behind extreme water levels, using both theory and analysis of actual data, and address the difficult problem of changing (non-stationary) risk. Statistical methods of assessing risk will be introduced, and case-studies of particular areas will be made. ‘Soft’ engineering measures to mitigate floods will be discussed. Students will be expected to complete a project that focuses on data analysis and/or numerical modeling. Local practitioners will be invited to give guest lectures.

Prerequisites:

CE 410/510 – TOP: Remote Sensing in Coastal and Inland Waters

Credits: 4

Lecture: Remote sensing is becoming increasing important in consulting practice, yet is still under- utilized in coastal and inland waters. This project based class will introduce students to different types of remote sensing techniques used in water resources, including fixed imagery, airborne imagery, and satellite imagery. The focus of the class will be to learn how to analyze remote sensing data products, using the matlab programming environment. Data filtering and error analysis will be covered. A particular focus will be using remote sensing data to understand physical processes. Areas of interest include (a) using infra-red data to assess turbulent structures and turbulence statistics; (b) using infra-red data to assess temperature gradients, upwelling, plumes, and other features in nature; (c) assessing water quality (turbidity, CDOM); (d) imaging and analyzing coastal waves using SAR data; (e) Analyzing flow using Codar and similar instruments; and (f) Analyzing mean sea-level and tides using satellite altimetry. For graduate students, the course will include a final, data based project. The class will include guest lectures by practitioners in the field.

Prerequisites:

CE 489/589 – Introduction to Advanced Fluid Mechanics

Credits: 4

Lecture and Laboratory: Advanced introduction to the geophysical fluid flows, including properties of seawater; conservation of mass, energy and momentum; dimensional analysis; the Navier‐Stokes, Reynolds and turbulent kinetc energy equations; geostrophy and potential vorticity; long and short waves; and turbulence and boundary layers. May be taken only once for credit.

Prerequisites: EAS 215, Mth 256, CE 361, and CE 362