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 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 The Erosion of Siletz Spit Oregon written by Campbell Cary Rea and published by . This book was released on 1974 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: Siletz Bay is a drowned river valley filled with Holocene alluvial and estuarine sediments and is separated from the ocean by a sand spit 3.8 km in length. Since the area was settled by white man in the 1890's, the bay has apparently experienced rapid siltation, due to increased farming and logging. This along with the damming of the Siletz River sloughs has altered circulation patterns in the bay. Deflection of the Siletz River flow by the prograding Drift Creek delta has caused 105 m of erosion since 1912 on the east side of Siletz Spit. The ocean side of the spit suffers periodic erosional episodes separated by periods of accretion and dune building. The most recent and publicized erosion occurred during the winter of 1972-73 when it was feared that the spit might be breached; one partially constructed house was lost and three others were saved only by timely riprapping. A sand mining operation may have aggravated the recent erosion by disrupting the sand budget, the balance of sand additions and losses from the beach. All of the foredune on the spit has been stabilized by dune grass and much of it has been riprapped. The long term effects of stabilization and riprapping are uncertain.
Download or read book Patterns of Fine grained Sediment Accumulation in the Delaware Estuary from PB 210 and CS 137 Distributions written by Elyse Scileppi and published by . This book was released on 2004 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spatial and Temporal Dynamics of Sediment and Wood in Headwater Streams in the Central Oregon Coast Range written by Christine L. May and published by . This book was released on 2001 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Channels that were scoured to bedrock by debris flows provided unique opportunities to calculate the rate of sediment and wood accumulation, to make inferences about processes associated with input and transport of sediment, and to gain insight into the temporal succession of channel morphology following disturbance. In an intensive investigation of 13 channels the time since the previous debris flow was estimated using dendrochronology. The volume of wood in the channel was positively and linearly correlated with the time since the previous debris flow. The pattern of sediment accumulation was non-linear and appeared to increase as the storage capacity of the channel increased through time. Wood stored the majority of the sediment in these steep headwater streams, and landslides and wind throw were the dominant mechanisms for delivering wood to the channel. With an adequate supply of wood, small streams have the potential to store large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain. In an extensive investigation of 125 headwater streams, the spatial and temporal patterns of debris flow occurrence and deposition were investigated. The temporal distribution of debris flow occurrence varied with network structure and drainage area of the tributary basin. Network structure may affect the frequency of debris flows delivered to the mainstem river valley because it reflects the number of potential landslide source areas and the routing ability of the channel. Tributary basins with larger drainage areas and more convergent topography had a greater proportion of channels in the younger, post-debris flow age-classes compared to smaller basins with less convergent topography. The flux rate of material delivered to the confluence with the larger river also influenced the development of debris flow fans. Fans at the mouth of tributary basins with smaller drainage areas had a higher likelihood of being eroded in the interval between debris flows, while larger, more persistent fans were present at the mouth of bigger basins. Valley floor width of the mainstem river typically constrained fan development and was also an important predictor of fan size.
Download or read book Sediment Accumulations Patterns in the Damariscotta River Estuary written by Emily A. Chandler and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Restoring the Pacific Northwest written by Dean Apostol and published by Island Press. This book was released on 2012-09-26 with total page 505 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Pacific Northwest is a global ecological "hotspot" because of its relatively healthy native ecosystems, a high degree of biodiversity, and the number and scope of restoration initiatives that have been undertaken there. Restoring the Pacific Northwest gathers and presents the best examples of state-of-the-art restoration techniques and projects. It is an encyclopedic overview that will be an invaluable reference not just for restorationists and students working in the Pacific Northwest, but for practitioners across North America and around the world.
Download or read book An Ecological Characterization of the Pacific Northwest Coastal Region Characterization atlas regional synopsis written by and published by . This book was released on 1980 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Ecological Characterization of the Pacific Northwest Coastal Region written by and published by . This book was released on 1980 with total page 834 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Ecological Characterization of the Pacific Northwest Coastal Region Data source appendix written by and published by . This book was released on 1980 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Geological Survey Bulletin written by and published by . This book was released on 1983 with total page 362 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 Science based Restoration Monitoring of Coastal Habitats Tools for monitoring coastal habitats written by and published by . This book was released on 2003 with total page 658 pages. Available in PDF, EPUB and Kindle. Book excerpt: This guidance manual ... provides technical assistance, outlines necessary steps, and provides useful tools for the development and implementation of sound scientific monitoring of coastal restoration efforts ... [and] offers a means to detect early warnings that the restoration is on track or not, to gauge how well a restoration site is functioning, to coordinate projects and efforts for consistent and successful restoration, and to evaluate the ecological health of specific coastal habitats both before and after project completion.
Download or read book Age and Origin of Fluvial Terraces in the Central Coast Range Western Oregon written by Stephen F. Personius and published by . This book was released on 1993 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiocarbon and thermoluminescence dating methods are used to determine the ages and probable origins of fluvial terraces.
Download or read book Coastline Changes written by Eric C. F. Bird and published by . This book was released on 1985-05-27 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes and analyses the advance and retreat patterns of the world's coastlines in recent decades. Based on a twelve-year investigation by the I.G.U. Commission on the Coastal Environment, this book examines the multiple factors responsible for coastline change and emphasizes the importance of monitoring these changes. It provides a basis for comparisons between changing coastline sections in various environments around the world.
