Download or read book Wave Conditions and Beach Erosion on the Oregon Coast written by Paul D. Komar and published by . This book was released on 1976 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Beach Profile Changes and Onshore offshore Sand Transport on the Oregon Coast written by Nicolás A. Aguilar Tun̄ón and published by . This book was released on 1977 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two beaches with significant differences in grain size and thus in beach profile morphology and response to wave conditions were studied on the Oregon coast. Gleneden Beach, just south of Siletz Spit and Lincoln City, has a median grain size of 0.36 mm (medium sand) and a steep beach face slope, while Devil's Punchbowl Beach has a median grain size of 0.23 mm (fine sand) and low concave-up beach face slope. Eleven beach profile surveys were obtained at Gleneden Beach and twelve at Devil's Punchbowl Beach between August 1976 and April 1977; on average once every two weeks during spring tides. Gleneden Beach showed the typical change from a swell profile with a wide berm that prevails during summer months to a storm profile with little or no berm that exists during the stormy winter months. This transition occurred in August and September, being completed by early November. The finer-grained Devil's Punchbowl Beach also showed general erosion during the fall. However, a transition from a swell profile to a storm profile is not as clear there as the beach has little berm, even in mid-summer, and always has a concave-up appearance typical of the winter storm profile. Gleneden Beach and Devil's Punchbowl Beach did not always agree in their responses to the changing wave conditions. One may be eroding at the same time the other is accreting. These differences in response to changing wave conditions appear to result from their differences in grain size. Volume changes of the erosion or deposition at the two beaches were computed from successive beach profiles. The coarser-grained Gleneden Beach showed larger changes in erosion and deposition, the maximum erosion being 0.71 m3 per meter of profile length, while the finer-grained Devil's Punchbowl Beach showed a maximum erosion of 0.25 m3 per meter of profile length. Attempts were made at relating the erosion or deposition and the volumes of erosion/deposition to the wave breaker heights and deep-water wave steepness that occurred between the beach profile sequences. There is only a vague relationship between the volumes of beach erosion/deposition and the wave heights, the probability of erosion increasing and the volume of sand eroded increasing with increasing wave breaker heights. The maximum wave heights that occur during the time interval appear to be most important to the volume of erosion, erosion volumes being large if storm breaker heights reach 5 to 6 meters or greater. Deposition prevails when the average breaker heights fall below 4 meters and storms are limited to breaker heights less than 5 meters. The deep-water wave steepness shows little relationship to the erosion or deposition volumes, indicating that the wave period is not as important a parameter as the wave height to beach erosion.
Download or read book Beach Processes on the Oregon Coast Jul 1973 written by William T. Fox and published by . This book was released on 1974 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt: During July and August, 1973, a 45-day time-series study was undertaken on the central Oregon coast to relate weather and wave conditions to beach erosion and sand bar migration. The summer weather pattern was dominated by the East-Pacific subtropical high which produced winds and waves from the northwest and extended periods of upwelling and coastal fog. When low pressure systems moved through, wind and waves shifted to the southwest. Three beaches were mapped at low tide to show changes in beach and bar morphology through time. At South Beach, Oregon two sets of bars with intervening rip channels advanced shoreward at 1 to 5 meters/day and southward at 10 to 15 meters/day. At Beverly Beach, Oregon, a basalt ridge 700 meters offshore resulted in wave diffraction and sand deposition in the central portion of the beach. A rip channel at the south end of the beach moved 300 meters to the south. At Gleneden Beach, cusps 40 meters long were cut into the steep foreshore. (Modified author abstract).
Download or read book Shoreline Changes Due to Jetty Construction on the Oregon Coast written by J. R. Lizarraga-Arciniega and published by . This book was released on 1975 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Patterns of beach erosion and accretion due to jetty construction are examined for the coast of Oregon. All jetty systems are included with the exception of those on the Columbia River, making a total of nine systems. All evidence indicates that these areas of the Oregon coast are experiencing a seasonal reversal in the sand drift, but with a zero or near zero net drift over a several years time span. Thus, shoreline changes resulting from jetty construction are not the usual examples of jetties blocking a net drift as found in southern California and elsewhere. In general, accretion of the shoreline took place adjacent to the jetties following their construction, both to the north and south. This accretion resulted mainly from the embayment formed between the jetty and the pre-jetty shoreline, the embayment becoming filled until the shoreline is straight and again in equilibrium with the waves such that there is a zero net sand drift. In some cases, as at the entrance to Yaquina Bay, the jetties are oblique to the trend of the shoreline and so produced a protected zone from the waves where accretion could occur. Sand for the accretion adjacent to the jetties was derived from beach erosion at greater distances from the jetties. The severity of the erosion depended on the total amount of sand required for the beach accretion to a new equilibrium, and the length of beach that was undergoing erosion. When only a short stretch of beach occurs to one side of the jetties, as at Bayocean Spit, then the resulting erosion was particularly severe, in that case leading to the breaching of the spit. A computer model is developed to simulate the shoreline changes that occurred following construction of the jetties on the Siuslaw River mouth. The model demonstrates deposition next to the jetty to fill the embayment created by the jetty, and erosion at greater distances from the jetty. The shoreline advances of the model agreed closely with the actual shoreline changes found in surveys following jetty construction.
Download or read book Dynamic Revetments for Coastal Erosion in Oregon written by Jonathan C. Allan and published by . This book was released on 2005 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Beach Processes on the Oregon Coast July 1973 written by William T. Fox and published by . This book was released on 1974 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Spring 1976 Erosion of Siletz Spit Oregon written by Paul D. Komar and published by . This book was released on 1977 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the period 1970-76, Siletz Spit on the mid-Oregon coast has suffered foredune erosion. This erosion is associated with high wave conditions along the coast, produced by intense storms in the North Pacific. During the winter of 1972-73 and during January through March 1976 the erosion was particularly severe. The pre-1975 erosion of the spit has been documented in a previous study. One of the main purposes of the present study is to document the 1976 erosion and to contrast it with the earlier episodes. It differed principally in that a small wash-over of the spit occurred in one area and beach drift logs were thrown up onto the dunes. Neither occurred during previous erosion episodes, even during the 25 December 1972 storm when wave breakers exceeded a significant wave height of 7 meters. This is because the 1972 storm occurred at a time of low water level, neap tide conditions. In contrast, the 18 February 1976 major storm occurred during spring tide conditions, causing the wash-over and log throwing, even though the waves were smaller than in December 1972. The amount of dune retreat was somewhat less in 1976 than in 1972-73, partly because of the shorter time period over which the 1976 erosion occurred and partly because of the use of protective riprap. The large waves causing the erosion at Siletz Spit are generated by storms in the North Pacific. The storm systems for December 1972, January 1973, and February 1976 were analyzed as to fetch distances, wind speeds and directions, movements of the fetches, and other factors important in the generation of waves. Waves hindcasted from these data were compared with measurements of the waves obtained from a seismometer system at the Marine Science Center in Newport, Oregon. This comparison demonstrated that these distant fetches were responsible for the waves causing erosion on Siletz Spit. Waves generated locally by coastal winds appear to be of negligible importance in the erosion. This is also shown by a comparison between the wave measurements and data on the coastal winds at Newport during the times of maximum erosion. Tides were investigated for their role in contributing to coastal erosion. High spring tides allow the storm waves to better reach the dunes or sea cliffs and so permit greater erosion. Neap tides, with their lower water levels, diminish the amount of erosion. Many of the differences in the December 1972 and February 1976 erosion episodes were due to the difference in tide levels. Storm surges were determined for Yaquina Bay, Oregon, by subtracting the predicted high-tide levels from the observed levels. It was concluded that significant storm surges did not occur at the times of maximum spit erosion and therefore did not contribute to the erosion processes.
Download or read book Handbook of Coastal Processes and Erosion written by Paul D. Komar and published by CRC Press. This book was released on 2018-02-06 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this book is to focus on the physical processes that cause coastal erosion.Many scientists and engineers have focused their research on the entire range of physical processes from the waves and the currents in the nearshore to the response of the beach, via sand transport, resulting in a changing coastal morphology. Of these many processes, this book focuses only on those which directly relate the generation of coastal erosion. Some chapters deal exclusively with the physical processes, while others provide examples of erosion problems although most of the chapter topics have clear implications for issues of coastal-zone management, these issues are not belaboured as several other books are already available in this area. The objective is to provide state-of-the-art presentation of the science of coastal erosion processes.
Download or read book Processes of Sea cliff Erosion on the Oregon Coast written by Shyuer-ming Shih and published by . This book was released on 1992 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sea-cliff erosion is a significant problem along the Oregon coast in that many communities have been built on terraces affected by bluff retreat. There is considerable coast-wide variability in the rates of cliff erosion. This variability is attributed in part to tectonic activity that is causing differential interseismic uplift along the coast. Analyses of geodetic survey data and tide gauge measurements have established rates of local sea-level rise along the entire coast, including areas lacking direct tide measurements. A littoral cell around the Lincoln City area on the central Oregon Coast is experiencing the smallest degree of tectonic uplift and this results in the highest rate of local sea-level rise and significant sea-cliff erosion. High cliffs cut into a Pleistocene marine terrace, consisting of semi-consolidated sands, back the beaches over the length of the littoral cell and supply coarse-grained sands to the beaches in the south of the cell. Dissections of multimodal grain-size distributions of the beach and cliff sands have shown that coarse-fraction modes are resistant to longshore wave dispersion, and this produces a marked longshore variation in the coarseness of beach sand, in the beach morphology, and in the nearshore processes affecting the cliff-toe erosion. Two years of monthly beach-profile surveys at eleven beaches along the Lincoln City littoral cell have shown that there is a significant difference in volumetric changes between beaches of different sand sizes. The coarse-grained reflective beaches are much more dynamic in profile changes, and the total quantity of sand moved under a given storm is much greater than on the fine-grained dissipative beaches. Rip-current embayments are also more important to cliff erosion o the reflective beach, producing bluff retreat that has a high degree of spatial variability and is extremely episodic. Risk assessments based on the probability curve of the extreme run-up have demonstrated that the height of the cliff-beach junction and the beach slope are important factors in controlling the risk of cliff-toe erosion. Run-up measurements using video techniques on three beaches having contrasting morphologies suggest that the maximum run-up calculation based on the empirical relationship derived by Holman and Sallenger (1985) appears to be valid, although the permeability effects might have contributed to a significance deviation in the prediction of maximum run-up on a sediment-starved beach.
Download or read book An Ecological Characterization of the Pacific Northwest Coastal Region Characterization atlas watershed unit descriptions written by and published by . This book was released on 1980 with total page 620 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 The Pacific Northwest Coast written by Paul D. Komar and published by Living with the Shore. This book was released on 1997 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: While the coast of the Pacific Northwest becomes ever more populated and developed, its beaches and cliffs continue to be altered by ocean currents and winter storms. Coastal oceanographer Paul Komar reminds readers of the area's geological and cultural history and the ever-present problem of erosion. He issues an urgent call for changes in shoreline management and attitudes toward development. 41 figures. 20 maps. 112 photos.
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:
Download or read book Hdbk Coastal Processes Erosion written by Paul D. Komar and published by Springer. This book was released on 1983-12-20 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this book is to focus on the physical processes that cause coastal erosion.Many scientists and engineers have focused their research on the entire range of physical processes from the waves and the currents in the nearshore to the response of the beach, via sand transport, resulting in a changing coastal morphology. Of these many processes, this book focuses only on those which directly relate the generation of coastal erosion. Some chapters deal exclusively with the physical processes, while others provide examples of erosion problems although most of the chapter topics have clear implications for issues of coastal-zone management, these issues are not belaboured as several other books are already available in this area. The objective is to provide state-of-the-art presentation of the science of coastal erosion processes.
Download or read book Cause and Prediction of Beach Erosion written by Stanley E. Wasserman and published by . This book was released on 1973 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
