Inlet Closure and Morphological Behavior in a Northern California Estuary PDF Download

Author: Dane Kristopher Behrens
Publisher:
ISBN:
Category :
Languages : en
Pages : 330

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Author: Dane Kristopher Behrens
Publisher:
ISBN: 9781267967510
Category :
Languages : en
Pages :

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Bar-built estuaries with unstable tidal inlets are widespread in Mediterranean climates and along wave-exposed coasts. While similarly important to coastal sediment balances and estuarine ecosystems, and more numerous than larger inlet systems, they suffer from a relative lack of understanding. This is a result of the setting: bar-built estuaries lie at a nexus of coastal and fluvial environments, often behaving like lakes with extreme variability in boundary conditions. At the ocean-side boundary, inlet channel blockage from wave-driven sedimentation is common, leading to water levels in the lagoon that are consistently higher than ocean levels (perched conditions) or to complete disconnection between the lagoon and the ocean (inlet closure). During times when the inlet channel allows tidal conveyance, flood tides provide saline, nutrient-rich water and vigorous turbulent mixing. Inlet closure traps seawater in the estuary and transforms these systems into salt-stratified coastal lakes. The amount of habitat space provided by the closed system is then constrained by the extent of the salt field, since it has marked effects on temperature and dissolved oxygen. Although closed and perched conditions are natural, encroachment from agriculture, roads and development has led to a host of fundamental changes to the way the inlet and estuary function. Combined with the present lack of understanding of how these systems behave in response to natural processes, this will be a growing concern as long-term shifts in climate continually alter the landscape and forcing conditions. This dissertation explores three areas in need of better understanding: (1) Variability of inlet closure frequency, (2) response of the estuarine salt field to inlet closure, and (3) the influence of inlet management on stratification in the estuary. These questions are addressed by examining the Russian River Estuary (RRE), a prototypical bar-built estuary in Northern California. This work builds from existing studies of the site by the author, leveraging a uniquely extensive set of in situ observations of daily inlet behavior with additional field and numerical modeling work. The aim is to use these tools to provide a more complete picture of the combined function of the inlet and estuary than is currently present in the literature. Inlet closure frequency is examined using over 60 years of daily closure records detailing the behavior of the Russian River mouth. Inlet morphological behavior is shown to be a response to processes which act to scour the inlet (driven by tides and river flows) and processes that act to deposit sand in the inlet (driven by waves). The observed time-dependent closure pattern is shown to be well-described as a response to tidal, weather-related, seasonal and interannual processes. A parametric model is developed to predict closure events in the short- and seasonal-term scales, and is shown to improve on existing models. Lastly, closure records from the nineteenth and twentieth centuries are compared, showing that inlet closures have become shorter and more sporadic over time at this site. Long term shifts such as this are examined within the context of management practices and climate variability. The evolution of the salt field is tracked during several inlet closure events in 2009 and 2010 using repeated boat-based conductivity temperature depth (CTD) surveys, stationary sondes and upward facing acoustic doppler current profilers (ADCPs). The motion of the intruding salt front is in general well-studied in relatively deep estuaries with gradually varying bathymetry. However, in bar-built estuaries such as the RRE, the mechanisms of upstream salt transport are more obscure, since these systems are often associated with sharply-varying bathymetry resulting from extensive meandering and high stream gradients. The field data are used to show that the salt front movement persists in the estuary despite these characteristics. Empirical orthogonal functions and a horizontal Richardson Number are employed to link the salt transport into the inner estuary to buoyancy-driven currents which move epilimnetic salt water upstream along the top of the pycnocline when diurnal winds are not active. Internal waves are also present, but are limited by the bathymetry in the extent to which they transport salt upstream. Volumetric capacity of the pools upstream of the front and turbulence caused by diurnal winds are shown to be the main impediment to the salt front advance. The impacts of inlet management on stratification in the estuary are assessed by examining two practices: (1) Allowing the inlet to remain closed and (2) enforcing perched conditions by cutting a one-way supratidal outflow channel over the beach. The ramifications of the latter are presently unknown. A numerical model is used to examine the different outcomes achieved during hypothetical two-week closure and overflow events at the RRE. The model uses a two-dimensional (x-z plane) representation that emphasizes the vertical salt stratification in the estuary. The modeling results show that having an overflow channel only several meters above the pycnocline results in strengthened stratification when winds are applied, while inlet closure leaves stratification mostly intact. Long-term changes in estuary salt mass are well-described as a function of the hydraulic gradient through the beach during closure, and as a function of vertical diffusion of salt during perched overflow. A ratio of the magnitudes of seepage flow out of the beach and vertical diffusive flow of salt across the pycnocline is a good descriptor of which process will dominate the long-term evolution of salt in the estuary. Boat-based field data confirm the model results, suggesting that the two management states present divergent outcomes in the estuary.

Author: Carlos Vionnet
Publisher: CRC Press
ISBN: 1482266601
Category : Science
Languages : en
Pages : 1116

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Coastal, estuarine, fluvial and submarine morphodynamics encompass some of the leading processes shaping our planet. They stem mainly, but not only, from the interaction of water in motion and movable sediment boundaries, resulting in morphological changes produced by erosion, transport and deposition of sediments that generate a variety of landsca

Author: Rowan A. Rowntree
Publisher:
ISBN:
Category : Bolinas Lagoon (Calif.)
Languages : en
Pages : 602

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Author:
Publisher:
ISBN:
Category : Aquatic biology
Languages : en
Pages : 410

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Publisher: Academic Press
ISBN: 0080885225
Category : Science
Languages : en
Pages : 6392

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The changing focus and approach of geomorphic research suggests that the time is opportune for a summary of the state of discipline. The number of peer-reviewed papers published in geomorphic journals has grown steadily for more than two decades and, more importantly, the diversity of authors with respect to geographic location and disciplinary background (geography, geology, ecology, civil engineering, computer science, geographic information science, and others) has expanded dramatically. As more good minds are drawn to geomorphology, and the breadth of the peer-reviewed literature grows, an effective summary of contemporary geomorphic knowledge becomes increasingly difficult. The fourteen volumes of this Treatise on Geomorphology will provide an important reference for users from undergraduate students looking for term paper topics, to graduate students starting a literature review for their thesis work, and professionals seeking a concise summary of a particular topic. Information on the historical development of diverse topics within geomorphology provides context for ongoing research; discussion of research strategies, equipment, and field methods, laboratory experiments, and numerical simulations reflect the multiple approaches to understanding Earth’s surfaces; and summaries of outstanding research questions highlight future challenges and suggest productive new avenues for research. Our future ability to adapt to geomorphic changes in the critical zone very much hinges upon how well landform scientists comprehend the dynamics of Earth’s diverse surfaces. This Treatise on Geomorphology provides a useful synthesis of the state of the discipline, as well as highlighting productive research directions, that Educators and students/researchers will find useful. Geomorphology has advanced greatly in the last 10 years to become a very interdisciplinary field. Undergraduate students looking for term paper topics, to graduate students starting a literature review for their thesis work, and professionals seeking a concise summary of a particular topic will find the answers they need in this broad reference work which has been designed and written to accommodate their diverse backgrounds and levels of understanding Editor-in-Chief, Prof. J. F. Shroder of the University of Nebraska at Omaha, is past president of the QG&G section of the Geological Society of America and present Trustee of the GSA Foundation, while being well respected in the geomorphology research community and having won numerous awards in the field. A host of noted international geomorphologists have contributed state-of-the-art chapters to the work. Readers can be guaranteed that every chapter in this extensive work has been critically reviewed for consistency and accuracy by the World expert Volume Editors and by the Editor-in-Chief himself No other reference work exists in the area of Geomorphology that offers the breadth and depth of information contained in this 14-volume masterpiece. From the foundations and history of geomorphology through to geomorphological innovations and computer modelling, and the past and future states of landform science, no "stone" has been left unturned!

Author: Duncan M. FitzGerald
Publisher: Springer Science & Business Media
ISBN: 140203296X
Category : Science
Languages : en
Pages : 365

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This collection of papers offers a new approach to nearshore and estuary studies, with an emphasis on multidisciplinary techniques and data integration. The important results of these studies are accompanied by full color images.

Author: Rafael Almar
Publisher: Frontiers Media SA
ISBN: 288971926X
Category : Science
Languages : en
Pages : 197

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Author: Pierre Lasserre
Publisher:
ISBN:
Category : Coastal ecology
Languages : fr
Pages : 484

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Author: Eduard A. Koster
Publisher: OUP Oxford
ISBN: 0191515434
Category : Science
Languages : en
Pages : 472

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A distinguished team of Western European scholars has written an advanced, full-length physical geography designed to be a state-of -the-art evaluation of the physical environment of Western Europe, being both retrospective and prospective in its perception of environmental change. The unique natural and regional environments of Western Europe are discussed, as well as the physical geographic framework of the region. Particular emphasis is placed on the impact and responses of human society on the physical environment of the region which is characterized by a very high population density. As an enhanced reference work it will be of enduring value.