Download or read book Sediment Accumulation in Tillamook Bay Oregon a Large Drowned river Estuary written by Paul D. Komar and published by . This book was released on 1997 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of the sediments in Tillamook Bay.

Download or read book Sediment Accumulation and Human Impacts in Tillamook Bay Oregon written by Michael N. Styllas and published by . This book was released on 2001 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tillamook Bay is the second largest estuary on the Oregon coast, and concerns have been raised whether human induced impacts have been responsible for the perceived increase in sedimentation rates during the past century. Major land-use practices within the five watersheds of the Bay include logging, forest fires, the construction of forest roads, the placement of dikes along the channels of the main rivers and in the estuary, the removal of riparian vegetation, and the construction of jetties at the tidal inlet. Each of these practices has led to impacts on the entire ecosystem of the watersheds and the Bay, but this study focuses on the effects of human disturbances on the Bay's sediment accumulation. This study examines in detail the land-use practices that have occurred in the watersheds, on the beaches, and in the estuary, focusing on those that have had a direct impact on the sedimentation regime of the Bay. One goal of the study is to assess the relative roles of natural processes versus human impacts on the sedimentation. A general description of the physical characteristics of Tillamook Bay and its surroundings is included, and a brief discussion is provided about the tectonic setting of the Northwest Coast, including its history of subduction earthquakes and the associate sea-level changes. Also provided is a summary of the existing information concerning the arrival of Indians and their environmental impacts, followed by a more detailed account of the major impacts that have resulted from the settlement of the Euro-Americans in the Tillamook area, in the 1850's. The study then focuses on the description of the watersheds from a geomorphologic point of view, and the important land-use practices that may have affected sediment yields during the past century. Analyses of the hydrology of the Tillamook Bay watersheds are included, and the relations between annual water yields and total precipitation are examined in distinct time intervals, each corresponding to a different period with different amounts of land uses. The results of these hydrology analyses suggest that the Tillamook watershed gradually recovered from a period of major disturbances (from 1933 to 1955) to more normal conditions (from 1977 to 1998). In addition, this part of the study attempts to quantify the sediment transport regime of the rivers draining the watershed by using a hydraulic model that is based on the principle of stream power, and on considerations of availability of transported material. Application of this model during the 1933-1955 period for the major rivers suggests an average sediment yield on the order of 410,540 tons/year, but most important are the relative changes of the delivered sediment through time. The results of the model suggest a 1.6-factor decrease of the amount of river sediments from the Heavily Impacted Period (1933-1955) of major disturbances to the Normal Period (1977- 1998). The spatial variations of beach and river derived sediments throughout the Bay are determined from textural and mineralogical analyses of surface sediment samples, with the beach sands dominating the area close to the inlet and the river derived sands being mainly deposited at the southeast and northeast parts of the Bay. The relative contributions of these two major sources of sediment were found to be 60% for the marine beach and 40% for the river sands. Further attempt is made to distinguish between the sand transported into the Bay from the individual rivers, and to determine the main processes that are responsible for the dispersion of sediments within the Bay. The attempts to distinguish sands contributed by the individual rivers involved modal analyses of the frequency curves of the surface sediment samples, and the results mainly suggest a grain-size increase away from the mouth of the rivers as a result of sediment reworking by estuarine processes following its initial deposition during episodic river flooding. The main processes that control the dispersion of sediments and their deposition within the Bay were identified by using factor analysis, the results of which suggest that various estuarine processes are responsible for the observed dispersal patterns. A brief review is provided of the study undertaken by Dr. James McManus for the collection and analyses of core samples from Tillamook Bay. Down-core geochemical analyses of major and minor elements indicate that there have been times of episodic input of marine sediment in the central and western portions of the Bay, which is a result of either periodic breaching or washover of Bayocean Spit, so that the beach sand source was more important in the past. This episodic input of marine sand as inferred from the down-core geochemical variations was related to the most recent subduction earthquake, which occurred on January 26th, 1700. Finally, a summary of the results and conclusions of different aspects of this study is presented, so that sedimentation in Tillamook Bay can be viewed as an integrated process involving the watersheds, the estuary, and the ocean beaches.

Download or read book Sediment Sources and the History of Accumulation in Tillamook Bay Oregon written by James McManus and published by . This book was released on 1998 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Patterns of Sediment Accumulation in the Siletz River Estuary Oregon written by Anna Pakenham and published by . This book was released on 2010 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Anecdotal evidence suggests many Pacific Northwest estuaries are filling with sediment due to historical logging activities in upstream watersheds. Using the Siletz River estuary as a case study, this research began by analyzing timber harvest and discharge records of the Siletz River watershed, and found that increased timber harvest coincides with a period of higher discharge. Based on these findings, sediment flux from the Siletz watershed was expected to have increased and resulted in higher sediment accumulation rates (SARs) in the estuary. To test these assumptions, SARs were estimated using down-core profiles of excess 210Pb and 137Cs from thirty-three cores taken within the estuary. Digital x-radiographs and grain size distributions of cores were used to provide a timeframe for flood deposits and provided further information on retention-related functions of the system. Results indicate minimal evidence for changes in SARs with only two 210Pb profiles and six 137Cs profiles that indicate an increase in deposition attributable to land use and hydroclimatic changes. Calculated SARs (0.18cm/y) were comparable to the rate of local sea level rise (0.19 cm/y), which indicates that retention in the estuary is influenced by the available accommodation space. This finding helps explain the distinct difference in sediment supplied (5.91 x 107 kg/y) to, and retained (8.42 x 106 kg/y) in, the estuary. Overall, this study illuminates the complexity of the forces that influence sediment flux from a watershed and retention within an estuary.

Download or read book Sand Rights 99 written by Lesley Ewing and published by . This book was released on 2000 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection contains 37 papers presented at the Sand Rights '99 conference, held in Ventura, California, September 23-26, 1999.

Download or read book Rocks of the Tillamook Bay Drainage Basin the Coast Range of Oregon written by Gregory Bostrom and published by . This book was released on 1997 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sediment Sources and the History of Accumulation in Tillamook Bay Oregon August 1998 written by James McManus and published by . This book was released on 1998 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: Final report.

Download or read book National Water Summary on Wetland Resources written by Geological Survey (U.S.) and published by . This book was released on 1996 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sedimentology and Neoichnology of a Mixed energy Estuary Tillamook Bay Oregon United States written by Rares Bistran and published by . This book was released on 2014 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies of modern, marginal marine sedimentary environments are widely used in paleoenvironmental interpretations, due to the high amount of sedimentological and neoichnological insight they can provide. Limited studies have been conducted on the distribution of facies in mixed-energy estuaries, which, when incorporated with observations from tide- and wave-dominated estuaries, can provide a better understanding of the range of controls on sediment and trace distribution within interpreted estuary settings observed in the rock record. This study focuses on the sedimentological and neoichnological facies observed within the inner estuary, middle estuary, and outer estuary settings of the mixed-energy Tillamook Bay Estuary, Oregon. Field research and data collection consists of detailed surface and subsurface observations aided by sediment cores. The sedimentological and neoichnological facies model presented contributes to the knowledge of proximal to distal facies models of estuary settings, ranging from the innermost fluvial-tidal transition zone to the outermost estuary, tidal sand bar-dominated zone.

Download or read book Rocks of the Tillamook Bay Drainage Basin the Coast Range of Oregon Sources of Sediment Accumulation in the Bay March 1997 written by Gregory Bostrom and published by . This book was released on 1997 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Summarizes the nature of geologic rock formations found within Tillamook Bay drainage.

Download or read book Final Report written by Larry Kester Benninger and published by . This book was released on 1982 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Journal of Sedimentary Petrology written by and published by . This book was released on 1984 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bibliography of the Geology and Mineral Resources of Oregon written by and published by . This book was released on 1980 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sea Level Rise for the Coasts of California Oregon and Washington written by National Research Council and published by National Academies Press. This book was released on 2012-12-06 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tide gauges show that global sea level has risen about 7 inches during the 20th century, and recent satellite data show that the rate of sea-level rise is accelerating. As Earth warms, sea levels are rising mainly because ocean water expands as it warms; and water from melting glaciers and ice sheets is flowing into the ocean. Sea-level rise poses enormous risks to the valuable infrastructure, development, and wetlands that line much of the 1,600 mile shoreline of California, Oregon, and Washington. As those states seek to incorporate projections of sea-level rise into coastal planning, they asked the National Research Council to make independent projections of sea-level rise along their coasts for the years 2030, 2050, and 2100, taking into account regional factors that affect sea level. Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future explains that sea level along the U.S. west coast is affected by a number of factors. These include: climate patterns such as the El Niño, effects from the melting of modern and ancient ice sheets, and geologic processes, such as plate tectonics. Regional projections for California, Oregon, and Washington show a sharp distinction at Cape Mendocino in northern California. South of that point, sea-level rise is expected to be very close to global projections. However, projections are lower north of Cape Mendocino because the land is being pushed upward as the ocean plate moves under the continental plate along the Cascadia Subduction Zone. However, an earthquake magnitude 8 or larger, which occurs in the region every few hundred to 1,000 years, would cause the land to drop and sea level to suddenly rise.

Download or read book Oregon Geology written by and published by . This book was released on 1992 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Ecology of Humboldt Bay California written by Roger A. Barnhart and published by . This book was released on 1992 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book National Assessment of Shoreline Change written by and published by . This book was released on 2006 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: