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Wolfson M.L. Naar D.F. Howd P.A. Locker S.D. Donahue B.T. Friedrichs C.T. Trembanis A.C. Richardson M.D. Wever T.F. 《Oceanic Engineering, IEEE Journal of》2007,32(1):103-118
A Kongsberg Simrad EM 3000 multibeam sonar (Kongsberg Simrad, Kongsberg, Norway) was used to conduct a set of six repeat high-resolution bathymetric surveys west of Indian Rocks Beach (IRB), just to the south of Clearwater, FL, between January and March 2003, to observe in situ scour and burial of instrumented inert mines and mine-like cylinders. Three closely located study sites were chosen: two fine-sand sites, a shallow one located in 13 m of water depth and a deep site located in 14 m of water depth; and a coarse-sand site in 13 m. Results from these surveys indicate that mines deployed in fine sand are nearly buried within two months of deployment (i.e., they sunk 74.5% or more below the ambient seafloor depth). Mines deployed in coarse sand showed a lesser amount of scour, burying until they present roughly the same hydrodynamic roughness as the surrounding rippled bedforms. These data were also used to test the validity of the Virginia Institute of Marine Science (VIMS, Gloucester Point, VA) 2-D burial model. The model worked well in areas of fine sand, sufficiently predicting burial over the course of the experiment. In the area of coarse sand, the model greatly overpredicted the amount of burial. This is believed to be due to the presence of rippled bedforms around the mines, which affect local bottom morphodynamics and are not accounted for in the model, an issue currently being addressed by the modelers. This paper focuses specifically on two instrumented mines: an acoustic mine located in fine sand and an optical instrumented mine located in coarse sand. 相似文献
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Trembanis A.C. Friedrichs C.T. Richardson M.D. Traykovski P. Howd P.A. Elmore P.A. Wever T.F. 《Oceanic Engineering, IEEE Journal of》2007,32(1):167-183
A simple parameterized model for wave-induced burial of mine-like cylinders as a function of grain-size, time-varying, wave orbital velocity and mine diameter was implemented and assessed against results from inert instrumented mines placed off the Indian Rocks Beach (IRB, FL), and off the Martha's vineyard coastal observatory (MVCO, Edgartown, MA). The steady flow scour parameters provided by Whitehouse (1998) for self-settling cylinders worked well for predicting burial by depth below the ambient seabed for (0.5 m) diameter mines in fine sand at both sites. By including or excluding scour pit infilling, a range of percent burial by surface area was predicted that was also consistent with observations. Rapid scour pit infilling was often seen at MVCO but never at IRB, suggesting that the environmental presence of fine sediment plays a key role in promoting infilling. Overprediction of mine scour in coarse sand was corrected by assuming a mine within a field of large ripples buries only until it generates no more turbulence than that produced by surrounding bedforms. The feasibility of using a regional wave model to predict mine burial in both hindcast and real-time forecast mode was tested using the National Oceanic and Atmospheric Administration (NOAA, Washington, DC) WaveWatch 3 (WW3) model. Hindcast waves were adequate for useful operational forcing of mine burial predictions, but five-day wave forecasts introduced large errors. This investigation was part of a larger effort to develop simple yet reliable predictions of mine burial suitable for addressing the operational needs of the U.S. Navy. 相似文献
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A novel method for parameterizing the morphology of seafloor ripples with fingerprint analysis numerical techniques is presented. This fully automated analysis tool identifies rippled areas in two-dimensional imagery of the seafloor, and returns ripple orientation and wavelength as well as a new morphological parameter, the spatial density of ripple defects. In contrast to widely used manual and spectral parameterization methods, this new technique yields a unique probability distribution for each derived parameter, which describes its spatial variability across the sampled domain. Here we apply this new analysis technique to synthetic and field collected side-scan sonar seafloor images in order to assess the methods capacity to define bed geometry across a wide range of simulated and observed morphological conditions. The resulting orientation and wavelength values compare favorably with those of the existing manual and spectral parameterization methods, and are superior under environmental conditions characterized by low signal to noise ratios as well as high planform ripple sinuosity. Furthermore, the resulting ripple defect density values demonstrate correlation with ripple orientation, wave direction, and the Shields parameter, which is consistent with recent investigations that have theoretically linked this parameter to hydrodynamic forcing conditions. The presented fingerprint analysis method surpasses the capacity of existing methods for ripple parameterization and promises to yield greater insight into theoretical and applied problems associated with the temporal and spatial variability of ripple morphology across a wide spectrum of marine environments. 相似文献
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Sorted bedforms on the inner shelf off northeastern New Zealand: spatiotemporal relationships and potential paleo-environmental implications 总被引：1，自引：1，他引：0
Sorted bedforms are heterogeneous shelf seabed features found ubiquitously on the inner shelf of New Zealand and around the
world. In this study we examine the shallow stratigraphy of sorted bedforms using diver-collected short cores together with
the textural analysis of the associated surface sediments in the Tairua-Pauanui embayment on the northeast coast of the North
Island of New Zealand. Combining sonar and textural analysis together with the local oceanographic conditions provides new
insight into the interpretation of sorted bedform features. In this regional case study, sorted bedforms are found to have
a stratigraphic signature characterized by alternating fine and coarse sequences that does not reflect alternating calm (low-energy)
and storm (high-energy) cycles. Instead, the core sequences suggest the signature of a heterogeneous inner shelf sedimentary
facies developed from morphodynamic feedback mechanisms operating at the scale of the bottom boundary layer. The resulting
sedimentary sequence (alternating coarse and fine units) found throughout this study site is the result of contemporaneous
sorting processes. 相似文献
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Accurate benthic habitat maps are critical for resource management in coastal waters with competing uses. We used a 500 kHz
phase-measuring bathymetric sonar (PMBS) and 900 kHz side-scan sonar to acquire seafloor data in estuarine and shelf environments.
Grab samples and remotely operated vehicle video created geological and biological classifications for segmented maps produced
by a backscatter clustering program. PMBS improves regional map resolution (<1 m), reduces the need for direct sampling, extends
information on sediment–biological relationships to larger areas, and allows measurements of bedforms. Auto-segmentation was
successful in environments with highly contrasting acoustic signatures and meters-scale homogeneity. Patchier communities
are identifiable in PMBS data. Species preferences for sediment (i.e., tubeworm preference for sediment without shell hash)
allowed us to determine potential habitat without identifying individual organisms in acoustic data. PMBS with sufficient
ground-truthing offers an efficient way to map seafloor characteristics, which is critical in marine spatial planning efforts. 相似文献
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