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Benjamin T. Gutierrez

Publications and source records attributed to Benjamin T. Gutierrez.

23 records · Page 2Linked to original sources
USGS2005

Exploring the persistence of sorted bedforms on the inner-shelf of Wrightsville Beach, North Carolina

Geological studies offshore of Wrightsville Beach, North Carolina reveal subtle large-scale regions of coarse sand with gravel and shell hash (widths between 100 and 200 m and negative relief of ∼1 m) that trend obliquely to the coast. It was previously suggested that these regions serve as conduits for sand exchange between the shoreface and inner shelf during storm-associated downwelling. Consequently they were classified as rippled scour depressions. More recently, the role of alongshore flows and self-organization as a result of inhibited settling of fine sand has been discussed. In this study, 45 days of near-bed current measurements were analyzed using benthic boundary layer and sediment transport models to examine the role of along- and cross-shore flows in driving sediment transport at this site. The wind climate was found to be a dominant influence on near-bed flows. Six distinct sediment transport events were recognized. During these events, sediment transport models show that bedload transport is directed mainly in the cross-shore direction, while suspended sediments are directed alongshore to the southwest. Current observations during these sediment transport events provide no evidence of cross-shore sediment transport caused by steady downwelling currents. Instead, benthic boundary layer model results are used to show that differences in bed roughness between the coarse areas of the seabed within the “rippled scour depressions” and the finer areas of the inner shelf are more pronounced during increasingly energetic wave and current conditions. The enhanced difference in roughness results in increased turbulence intensities over coarse regions inhibiting the deposition of the fine sand that is resuspended over the shelf during these events relative to finer areas over the shelf. Findings from this study contribute to explaining the observed long-term persistence of these features.

North Carolina↗
USGS2004

Long-Term Oceanographic Observations in Western Massachusetts Bay Offshore of Boston, Massachusetts: Data Report for 1989-2002

This data report presents long-term oceanographic observations made in western Massachusetts Bay at two locations: (1) 42 deg 22.6' N., 70 deg 47.0' W. (Site A, 33 m water depth) from December 1989 through December 2002 (figure 1), and (2) 42 deg 9.8' N., 70 deg 38.4' W. (Site B, 21 m water depth) from October 1997 through December 2002. Site A is approximately 1 km south of the new ocean outfall that began discharging treated sewage effluent from the Boston metropolitan area into Massachusetts Bay on September 6, 2000. These long-term oceanographic observations have been collected by the U.S. Geological Survey (USGS) in partnership with the Massachusetts Water Resources Authority (MWRA) and with logistical support from the U.S. Coast Guard (USCG - http://www.uscg.mil). This report presents time series data through December 2002, updating a similar report that presented data through December 2000 (Butman and others, 2002). In addition, the Statistics and Mean Flow sections include some new plots and tables and the format of the report has been streamlined by combining yearly figures into single .pdfs. Figure 1 (PDF format) The long-term measurements are planned to continue at least through 2005. The long-term oceanographic observations at Sites A and B are part of a USGS study designed to understand the transport and long-term fate of sediments and associated contaminants in the Massachusetts bays. (See http://woodshole.er.usgs.gov/project-pages/bostonharbor/ and Butman and Bothner, 1997.) The long-term observations document seasonal and inter-annual changes in currents, hydrography, and suspended-matter concentration in western Massachusetts Bay, and the importance of infrequent catastrophic events, such as major storms or hurricanes, in sediment resuspension and transport. They also provide observations for testing numerical models of circulation. This data report presents a description of the field program and instrumentation, an overview of the data through summary plots and statistics, and the data in NetCDF and ASCII format for the period December 1989 through December 2002 for Site A and October 1997 through December 2002 for Site B. The objective of this report is to make the data available in digital form and to provide summary plots and statistics to facilitate browsing of the long-term data set.

Data Series↗
USGS2003

Photographs of the Sea floor Offshore of New York and New Jersey

This DVD-ROM contains photographs of the sea floor and sediment texture data collected as part of studies carried out by the U.S. Geological Survey (USGS) in the New York Bight (Figure 1a (PDF format)). The studies were designed to map the sea floor (Butman, 1998, URL: http://pubs.usgs.gov/fs/fs133-98/) and to develop an understanding of the transport and long-term fate of sediments and associated contaminants in the region (Mecray and others, 1999, URL: http://pubs.usgs.gov/fs/fs114-99/). The data were collected on four research cruises carried out between 1996 and 2000 (Appendix I). The images and texture data were collected to provide direct observations of the sea floor geology and to aid in the interpretation of backscatter intensity data obtained from sidescan sonar and multibeam surveys of the sea floor. Preliminary descriptions of the sea floor geology in this region may be found in Schwab and others (2000, URL: http://pubs.usgs.gov/of/of00-295/; 2003), Butman and others (1998, URL: http://pubs.usgs.gov/of/of98-616/.), and Butman and others (2002, URL: http://pubs.usgs.gov/of/of00-503/). Schwab and others (2000 URL: http://pubs.usgs.gov/of/of00-295/; 2003) have identified 11 geologic units in New York Bight (Figure 2 (PDF format)). These units identify areas of active sediment transport, extensive anthropogenic influence on the sea floor, and various geologic units. Butman and others (2003) and Harris and others (in press) present the results of a moored array experiment carried out in the Hudson Shelf Valley to investigate the transport of sediments during winter. Summaries of these and other studies may be found at USGS studies in the New York Bight (URL: http://woodshole.er.usgs.gov/project-pages/newyork/). This DVD-ROM contains digital images of bottom still photographs, images digitized from videos, sediment grain-size analysis results, and short QuickTime movies from video transects. The data are presented in tabular form and in an ESRI (Environmental Systems Research Institute, URL: http://www.esri.com) ArcView project where the image and sample locations may be viewed superimposed on maps showing side-scan sonar and/or multibeam backscatter intensity and bottom topography.

Open-File Report↗
USGS2001

Photographs of the sea floor in western Massachusetts Bay, offshore of Boston, Massachusetts, July, 1999

This CD-ROM contains photographs and sediment sample analyses of the sea floor obtained at 142 sites in western Massachusetts Bay (Figure 1) during a research cruise (USGS cruise ISBL99024) aboard the Fishing Vessel (FV) Isabel S. (Figure 2) conducted July 18-21, 1999. These photographs and samples provide critical ground truth information for the interpretation of shaded relief and backscatter intensity maps created using data collected with a multibeam echo sounder system (Butman and others, in press, a, b, c; Valentine and others, in press, a, b, c). Collection of these photographs and samples was undertaken in support of a large project whose overall objective is to map and describe the sea floor of Massachusetts Bay.

Massachusetts↗