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...
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...
Theoretical breaking criteria for progressive surface gravity
waves are examined, and laboratory and field experiments concerned
with breaking waves are reviewed with respect to the testing of these
breaking criteria. The measurements of Komar and Simmons are
presented here for the first time. Only three theoretical breaking
criteria have been...
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...
Field observations are made of the formation of backwash ripples
on the beachface, formed by undular hydraulic jumps generated by backwash
down the beach face colliding with wave bores. Measured ripple
wavelengths range from set averages of 48 to 70 cm. Within a particular
set of ripples there is a...
Heavy mineral compositions of sands from Oregon beaches,
rivers and sea cliffs have been determined in order to examine the
causes of marked along-coast variations in the beach-sand
mineralogy. The study area extends southward from the Columbia
River to the Coquille River in southern Oregon. The heavy-mineral
compositions were determined...
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...
The formation of beach placers primarily involves processes of
waves and currents that selectively sort and concentrate the valuable
minerals according to their densities, sizes and shapes. Black sand
placers are found on the beaches adjacent to the mouth of the Columbia
River. Reviews of historical shoreline changes show that...
Grain-size distributions of gravels transported as bedload in Oak Creek, Oregon,
show systematic variations with changing flow discharges. At low discharges the gravel
distributions are nearly symmetrical and Gaussian. As discharges increase, the
distributions become more skewed and follow the ideal Rosin distribution. The patterns of
variations are established by...
Concern regarding increased coastal erosion has heightened amid growing acceptance of global warming and associated sea-level rise. This study examines shoreline erosion in Flathead Lake, Montana due to five decades of artificially elevated lake levels. It provides a model to investigate coastal erosion associated with sea-level rise. The natural water...
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...
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...
Based on the principle that the history of a discipline is important to the discipline itself, this thesis devotes two chapters to ROBERT HOOKE AND THE FOUNDATION OF GEOLOGY and two chapters to modern geology, viz. THE TECTONIC EVOLUTION OF THE OREGON CONTINENTAL MARGIN. The first part of this abstract...
