Development and erosion history of Bayocean Spit, Tillamook, Oregon

Bayocean sand spit lies along the northern Oregon coast approximately 70 miles south of the Columbia River. Work was begun on the construction of a large recreational resort on the spit in the early 1900's. At the outset, the resort appeared to have a promising future. However, a three-year delay in the completion of the railroad to Tillamook created financial instability and lawsuits which continued up to the depression of the early 1930's. There soon followed severe erosion of Bayocean spit leading to its breaching in 1952 and forcing the abandonment of the deteriorated resort. The erosion appeared to have been initiated by the construction and subsequent lengthening of a north jetty to the Tillamook Bay channel. Rapid sand deposition north of the north jetty indicated that the structure had blocked a predominant north to south longshore sand transport, thus depriving the spit of sand and resulting in erosion. Similar occurrences have been documented at other coastal locations. However, analysis of historical shoreline changes and aerial photographs taken in 1971, 1972, and 1973 show that sand eroded from beaches to the north and to the south of the jetty has been transported and deposited immediately adjacent to both sides of the structure. This symmetrical pattern of erosion and deposition on both sides of the jetty indicates a reversing longshore sand transport with a near zero net annual drift. The shoreline conditions at Bayocean demonstrate that beach erosion can result from the construction of a jetty transverse to a seasonally reversing longshore sand transport with a near-zero net drift

Breaking waves : a review of theory and measurements

Theoretical b:::-eaking 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 proposed for maximum steady waves in water of constant depth: ( 1) the kinematic breaking criterion, in which the horizontal partical velocity at the crest just equals the wave phase velocity, (2) the reversal of the vertical particle velocity near the crest as the ratio of wave height to water depth, H/h, increases, and (3)the reversal of the vertical pressure gradient beneath the crest as H/h increases. Although most theoreticians have applied the kinematic breaking criterion in conjunction with relatively simple wave theories (based on the motion being inviscid, irrotational, incompressible, surface tension free, and two dimensional), they do not always obtain identical results; for example, theoretical estimates of the particle acceleration at the crest range from zero to g, the gravitational acceleration. For shoaling waves, the kinematic breaking criterion and the presence of a vertical surface are suggested as breaking criteria. Unfortunately, these criteria were applied to the long wave theory which is considered inadequate near the breaking position. The re-examination of experiments on breaking waves shows that past measurements are not sufficient for testing any of these breaking criteria, In particular, the following improvements should be made: (1) standardize definitions of wave and breaking parameters, (2) apply or design, if necessary, more accurate techniques to measure water particle velocities and accelerations, and (3) monitor the fluid motions from which the breakers cannot be separated (e.g. backwash, solitons, reflected waves, edge waves and rip currents). Studies specifically designed to obtain the necessary measurements for testing the theoretical breaking criteria are needed

Analysis of benthic infauna communities and sedimentation patterns of a proposed fill site and nearby regions in the Columbia River Estuary

The Port of Astoria has proposed to fill a 32.4 hectare inter- and subtidal area at the mouth of Youngs Bay, Columbia River, Oregon. The possible effects of this fill on the biota and sedimentation patterns of this area were studied from 31 August 1975 to 29 February 1976. Part I, the biological studies, analyzed the quantity of benthic life at the fill site in comparison to that in the lower 28 miles of the Columbia River estuary. The sediment textures of benthos samples were analyzed to determine sediment-fauna relations; salinity-temperature measurements were made at selected sites. Fish life at the fill site was also sampled to determine species composition and the relation of fish stomach contents to benthic life. Studies on sedimentation patterns (based on dredging records, photographs, and sediment samples taken in Slip 2 of the port docks) aimed at identifying undesirable sediment deposits which might occur because of the fill. The dominant benthic taxa at most stations were amphipods and polychaetes, although oligochaetes were abundant at some muddy stations. Amphipod densities in the lower river varied from about 200/m2 in deep areas to between 5,000 and 50,000/m2 in shallow, fine sediment areas such as Youngs Bay and extensive shoaling areas. These areas of high density, which include the fill site, were dominated by the tube-building amphipod Corophium. Twenty-five species of fish have been captured in this and previous work in Youngs Bay. Food habit studies have shown Corophium to be eaten in large quantities by many of these species. Using density estimates and river bathymetry as guides, it was very roughly estimated that 0.8 percent of the amphipod standing crop in the study area (CRM 0-28) occurred at the fill site, which represents 0.09 percent of this area. Net sediment transport seems to be from the Columbia River into Youngs Bay, but transport out of Youngs Bay does occur and may contribute greatly to sediment deposition in Slips 1 and 2. Sediment samples from Slip 2 were mud, but this changed abruptly to coarse sand at the slip mouth. This shows that slip sediments arise from suspended fine mud and not from coarser-grained bed-load sediments. There is little that can be done to prevent such deposition. The proposed extension would probably not affect this problem, but might alter the flow of water around the port. More extensive investigations of circulation and suspended sediment content should be made

An evaluation of methods of differentiating beach and dune sands by application to Lake Michigan env

Master of ScienceGeologyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/115042/1/39015003265819.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115042/2/39015003265819.pd