Aubrey David G.

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Tidal circulation and flushing characteristics of the Nauset Marsh System : report to the Town of Orleans

(Woods Hole Oceanographic Institution, 1997-07) Aubrey, David G. ; Voulgaris, George ; Spencer, Wayne D. ; O'Malley, Stephen P.

Various interested bodies (i.e., National Park Servce, Cape Cod Commssion, and the Town of Orleans) charged with management of the Nauset Marsh system on Cape Cod, MA, commissioned a study of the estuarine circulation within the Nauset system. Recent signficant morphological changes in the system have changed mixing processes and residence times for the embayment. This study specifically addressed the differing water circulation and residence times arising from a migrating single inlet (dominant condition) and dual inlet (1992-1996) situations. These residence times are to be used by the Cape Cod Commission to identify nitrogen-sensitive sub-embayments based on various assumptions of build-out and nutrient loading. The Nauset Marsh system has experienced considerable development in recent years; proper management of this resource area requires knowledge of the consequences of such development. Application of field observations of bathymetry, sea surface elevation, temperature, salinity and currents, leads to better understanding the physics of the system. These data, analyzed in various forms, served as input data for a numerical, two-dimensional circulation model of the embayment. The circulation model provided flow and discharge data with which the residence times were calculated. Bathymetric measurements defined the volumes of the various sub-embayments to be used in the calculation of residence times. Residence times were calculated for six sub-embayments of the system, defined on the basis of their common hydrodynamic and morphologic characteristics. Two scenarios were evaluated: one for the present single-inlet system, which is near typical for most system states, and one for a dual inlet system such as existed for a period of time from 1992 through 1996. Residence times were evaluated for twelve cases, to demonstrate the range of residence times that can be defined based on varing assumptions. For instance, residence times can be defined on the basis of mean low water volumes or mean water levels, the latter being the more conservative (yielding a longer residence time). In addition, residence times depend on whether spring tides, neap tides, or average tidal conditions are used. We provide data on all three conditions: the neap tidal case is the most conservative in the sense of providing a longer residence time. This case can serve as the basis for flushing if conservatism is desired. Finally, residence time can be defined based on the amount of time it takes for water to renew itself with water from adjacent sub-embayments, or more conservatively assuming renewal from the offshore waters (which are presumed to be cleaner). Based on these various inputs, assumptions and calculations, residence times for Salt and Mill ponds under conditions of a single inlet are the longest of the various sub-embayments. Town Cove is still relatively quickly renewed, though not as fast as the main channels serving the system. Flow pattern under dual-inlet condition does seem to be partioned well, with the northern inlet serving the northern part of the system and the southern inlet serving the southern part of the system, with litte hydrodynamc communication between the two divisions. This new hydrodynamc behavior results in shorter residence times under dual inlets than under a single inlet. Calculations indicate that the slowest flushing occurs in Mill and Salt ponds. The main body of the embayment, consisting of narrow channels between well-flushed salt marsh and tidal flats, flushes rapidly. Two-dimensional calculations show that Town Cove also flushes relatively rapidly, on average. However, its greater depth and occasional temperature stratification create conditions which might accumulate nutrients in bottom sediments, which, when released, can cause decrease in water quality (such as plankton blooms). A more sophisticated low-trophic level ecosystem model combined with vertical hydrodynamic structure could clarfy the dynamics of this process. This study provides a defensible basis for evaluating nutrient loading and potential eutrophication arising from development in the watershed around Nauset embayment. However, since morphological changes occur on a rapid basis in this area, the issue of residence time should be re-examined periodically. For instance, rapid onshore migration of the southern barrier beach is threatening closure of the south chanel, a condition which could adversely affect water quality in Nauset Harbor in the near futue. A process should be established to examine the sensitivity of residence times for rapidly changing morphology.
Pressure/Temperature Logger (PTL) development and field deployment for the Great Bay, NH, tidal dynamics experiment

(Woods Hole Oceanographic Institution, 1998-01) Friedrichs, Carl T. ; Spencer, Wayne D. ; Aubrey, David G.

Durg 1992 and 1993 experiments were conducted in the shallow east side of Great Bay, New Hampshire. These experiments were conducted to better understand the morphodynamics and evolutionary tendencies of shallow tidal embayments and intertidal fiats. Hardware and software used in the collection of data are described. Discussed also are techniques used to collect data. Six pressure temperature loggers (PTL) and one current meter (TCSWG) were developed for the experiments. Both instruments are internally powered and internally recording. The instruments were developed because no company was found that manufactured a similar instrument within the price range of the project.
Beach changes at Nauset Inlet, Cape Cod, Massachusetts, 1670-1981

(Woods Hole Oceanographic Institution, 1982-08) Speer, Paul E. ; Aubrey, David G. ; Ruder, E.

A historical study of barrier beach and inlet changes for the Nauset Inlet region, Cape Cod, Massachusetts, was performed to document patterns of beach and inlet change as a preliminary to designing and carrying out ffeld studies of inlet sediment transport. 120 historical charts from 1670 and 125 sets of aerial photographs from 1938 formed the basis for this study. Specific aspects of barrier beach and inlet change addressed include onshore barrier beach movement, longshore tidal inlet migration, and longshore sand bypassing past the inlet. In an effort to correlate forcing events with barrier changes, an exhaustive study of the local storm climate was performed. Detailed treatment of the specific mechanisms responsible for Nauset Inlet migration episodes in a direction opposite the dominant littoral drift are treated in a companion paper by Aubrey, Speer, and Ruder (1982). Documentation of the data base available for the Nauset Area is presented herein as appendices.
Atlantic shelf sand ridge study : physical oceanography and sediment dynamics data report

(Woods Hole Oceanographic Institution, 1990-02) Dragos, Paul ; Aubrey, David G.

This report describes and presents the hydrodynamic meaurements made during the Atlantic Shelf Sand Ridge Study at and near Peahala Ridge, offshore of Long Beach Island, New Jersey, in Spring 1985. The intent of this phase of the study was to examine the physical oceanographic and fluid mechanical processes in the vicinity of Peahala Ridge, one of the large shore-oblique sand ridges common in the area, and from this to identify those processes responsible for sand transport near the ridge with particular reference to its generation, maintenance and migration. The field measurement program was carried out from March to May 1985 by scientists and staff of the Woods Hole Oceanographic Institution. It included measurements of currents, temperature, waves, pressure and near-bed velocity profiles. This phase was part of a larger oil industry study that included extensive geological and geophysical measurements of Peahala Ridge and other ridge-and-swale areas of the mid-Atlantic continental shelf.
Remote sensing in the coastal and marine environment : proceedings of the first U. S. North Atlantic regional workshop held at the W. Alton Jones campus, University of Rhode Island, May 30-June 1, 1979

(Center for Ocean Management Studies, University of Rhode Island and the Woods Hole Oceanographic Institution, 1980) Zaitzeff, James B. ; Cornillon, Peter ; Aubrey, David G.

The First U.S. North Atlantic Regional Workshop on Remote Sensing in the Coastal and Marine Environment was held at the W. Alton Jones Campus, University of Rhode Island, May 30- June 1, 1979. The objectives of the meeting were to determine and document regional user needs for marine environmental data that might be acquired by remote sensing and to further the interchange of information between the developers of remote sensing technology, suppliers of remote sensing data products, and users of coastal and marine information. The workshop was structured to expose coastal specialists and users of marine data to the potentials of remote sensing and to provide a mechanism through which representatives of the remote sensing community might gain knowledge of the priorities of the potential users. A mutual awareness of the perspectives of each group is essential for beginning a dialogue and for overcoming one of the major obstacles to technology transfer - communications. In planning the remote sensing workshop, a committee was organized to insure a balanced review of the technology and to invite the involvement of the user community. The members of t;1e planning committee represented scientific, private, and federal interests. The activity documented in this report consists of invited presentations that were grouped in the following categories: (1) a technical orientation of earth resources remote sensing, including data sources and processing, (2) a review of the present status of remote sensing -technology applicable to the coastal and marine environment, (3) a description of data and information needs of selected coastal and marine activities and (4) an outline of plans for marine monitoring systems for the U.S. East Coast and a concept for an East Coast remote sensing facility. In addition to these invited presentations, one of the evening sessions was devoted to three working groups that addressed user needs and remote sensing potentials in the areas of coastal processes and management, commercial and recreational fisheries, and marine physical processes. The results of these working group sessions were presented and discussed on the morning of the final day. The recommendations of the workshop, which are provided in the executive summary and in the body of this document, represent a cross-section of needs for present and future consideration for remote sensing data. They concern improvement in addressing user remote sensing data needs, defining deficiencies, and in specifying research areas. The two and one-half day meeting provided an effective mechanism for establishing new dialogue between operational and research regional marine data users and the appropriate federal agencies and private interests developing remote sensing technology. Participants in this workshop reflected a cross section of U.S. North Atlantic interests, with representation from state, federal, academic research, and commercial activities. The ultimate goal of the workshop will be continued input and association with remote sensing programs by the marine user.
The use of the coastal oceans in the 80's : opportunities for marine geology

(Woods Hole Oceanographic Institution, 1980-04) Ross, David A. ; Aubrey, David G.

Events of recent years have clearly indicated that the United States will be making greater use of its coastal and offshore region in the 1980's. Rational use of this area will require the combined talents of scientists, engineers, politicians, environmentalists and others . There will be pressures and needs to use the coastal ocean for nuclear waste disposal, marine mining, disposal of waste materials, and hydrocarbon exploration: these uses will require new answers and technologies for many important marine geological questions. In an effort to identify these questions and determine what is needed to answer them, a group of approximately sixty geologists and marine scientists from academia, industry and the federal government met for a 2-1/2 day workshop at Woods Hole in October 1979. Initially the group looked at six uses of the offshore region: Nuclear Waste Disposal; Sewage, Industrial and Dredge Material Disposal; Offshore Structures; Marine Mining; Hydrocarbon Exploration and Extraction; and Military Related Activities .
Proceedings of a Workshop on Coastal Zone Research in Massachusetts : (November 27-28, 1978)

(Woods Hole Oceanographic Institution, 1979-04) Aubrey, David G.

A workshop on Coastal Zone Research held on 27 and 28 November, 1978, at Woods Hole Oceanographic Institution, brought together fifty researchers actively studying physical processes in the Massachusetts coastal zone (Appendix 1). Presentations were given by nearly half of the participants to acquaint other researchers with their past, present, and future research interests. Summaries of the presentations are included in Appendix 3. Although the scope of the workshop was narrow, emphasizing only selected aspects of coastal zone research, it represented an important attempt to assess our knowledge of physical processes in the nearshore, and to encourage cooperation and communication between scientists. Two sets of recommendations evolved from the workshop. The first set recommends ways to facilitate scientist - user communication, and provide more rapid dissemination of coastal research results. The second set describes areas of future research in the Massachusetts coastal zone. Neither of the two sets of recommendations is comprehensive: they reflect primarily the opinions and judgements of the workshop participants. Because of the interest expressed by the participants, the workshop will be held on an annual basis until the need for such meetings disappears. Future workshops may have specific goals, e.g. preparation of coastal erosion maps or historical shoreline change maps. Future meetings may also have more state, federal, and local governmental participants in an effort to foster scientist - user communications. The workshop was co-sponsored by the Woods Hole Sea Grant Program and Woods Hole Oceanographic Institution. The Woods Hole Sea Grant Program has offered to co-sponsor future Workshops on Coastal zone Research as part of their continued interest in the Massachusetts coastal zone.
Geodetic fixing of tide gauge bench marks : technical report

(Woods Hole Oceanographic Institution, 1989-08) Carter, William E. ; Aubrey, David G. ; Baker, Trevor ; Boucher, Claude ; LeProvost, Christian ; Pugh, David T. ; Peltier, W. R. ; Zumberge, Mark A. ; Rapp, Richard H. ; Schultz, Robert E. ; Emery, Kenneth O. ; Enfield, David B.

Under the auspices of the International Association for Physical Sciences of the Ocean (IAPSO) a committee was established to identify the oceanographic and geophysical requirements for fixing Tide Gauge Bench Maries (TGBM's) in an absolute terrestrial coordinate system; to evaluate the technology for fixing TGBM's; and to malce recommendations to the Commission on Mean Sea Level and Tides (IAPSO) of a strategy for coordinated global fixing ofTGBM's and for making the results centrally·available. To meet these goals, the committee met for a several day session at the Woods Hole Oceanographic Institution in November, 1988. From this workshop came a series of technical conclusions, plus specific recommendations to achieve the goals of the committee. Included in these discussions were Very Long Baseline Interferometry, Satellite Laser Ranging, Lunar Laser Ranging, Global Positioning System, and Absolute Gravity Meters, as well as mechanisms for logging and distributing the results from these systems, perhaps via the Permanent Service for Mean Sea Level (PSMSL) in Britain.
Hurricane impacts on the Caribbean coastal/marine environment : using scientific assessment to plan for the future

(Woods Hole Oceanographic Institution, 1991-09) Aubrey, David G. ; Giese, Graham S. ; Burdick, D. M. ; Agardy, M. T. ; Haney, J. Christopher ; Gable, F. J.

The passage of Hurricane Hugo through the eastern Caribbean provided a unique opportunity for multidisciplinary study of (1) the effects of severe storms on tropical coastal and marine ecosystems, and (2) the physical and biological responses of those ecosystems to intense storm-induced changes. In addition to its direct value as basic science, this study can be used to facilitate development of improved coastal and marine resource management capabilities.
Field evaluation of Sea Data directional wave gage : (Model 635-9)

(Woods Hole Oceanographic Institution, 1981-05) Aubrey, David G.

A directional wave gage consisting of a two-axis electromagnetic current meter and a pressure sensor, developed by Sea Data Corporation, with modifications specified by the author, was successfully deployed during the joint NOAA/U.S. Army Corps of Engineers Coastal Engineering Research Center's Atlantic Remote Sensing Land/Ocean Experiment (ARSLOE) during November, 1980. Data recovery rate was 100%, and instrument function was verified through comparison with a four-element pressure sensor array at the same location, an X-band imaging radar, and with surface meteorological observations charting developing local wave fields. The instrument was proven to be a viable alternative for point measurements of directional wave fields and for estimating the first five fourier coefficients in a directional wave model.
Recent evolution of an active barrier beach complex : Popponesset Beach, Cape Cod, Massachusetts

(Woods Hole Oceanographic Institution, 1982-01) Aubrey, David G. ; Gaines, Arthur G.

Popponesset Spit, the barrier beach sheltering Popponesset Bay on Cape Cod, Massachusetts, has experienced large changes in its location and shape over the past thirty years. Concern by the public over loss of this barrier beach and the associated recreational and wildlife resources, as well as its storm-protection function, resulted in a number of studies involving local, state and federal officials. The purpose of these studies was to identify causes and future trends (Benoit and Donahoe, 1979) and to identify engineering solutions to this instability (U.S. Army Corps of Engineers, 1972; Camp, Dresser and McKee, 1981). For various reasons, these studies were incomplete and stated some conclusions which were generally misleading or incorrect. The purpose of the present study was to provide a thorough reexamination of the geological problem at Popponesset Spit, to dispel the misconceptions and to more rigorously document the large-scale changes. The impetus for our concern over the beach was a desire to contribute to an effective, rational management and utilization strategy for this coastal region.
Sediment transport in a tidal inlet

(Woods Hole Oceanographic Institution, 1983-06) Aubrey, David G. ; Speer, Paul E.

Various aspects of sediment transport in and around natural, unstructured tidal inlets were investigated over the two year period of study. Concentrating on two tidal inlets (Nauset Inlet and Popponesset Inlet, Cape Cod, MA), and combining detailed field observations with numerical model studies of tidal flows in inlet/estuarine environments, several aspects of tidal inlet behavior have been clarified. In addition, field work has resulted in a number of technical publications of general utility to a wide spectrum of coastal research interest. Primary scientific items addressed in this study include: 1) diagnostic numerical model of generation and propagation of tidal non-liniarities in shallow estuarine channels; 2) effects of flow curvature on tidal inlet sediment transport; 3) definition of mechanisms by which tidal inlets migrate in a direction opposite to the net littoral drift direction; 4) hypothesis of a mechanism for rapid barrier spit growth in locations with low rates of littoral transport; 5) clarification of long-term patterns of sea-level rise in the United States to assess its role in tidal inlet/esturarine evolution; 6) historical descriptions of massive inlet migration at two study inlets as supporting evidence for the inlet modeling studies. Technical information generated by the study includes a description of a low-cost, reliable method to join nearshore electrical cables; description and intercomparison of instrumentation and analysis routines for estimating directional spectral parameters from wave gage data; and development of a field system and laboratory analysis package for preparing accurate bathymetric charts in shallow, nearshore regions, using microwave navigation and precision echo-sounding.
Beach changes and management options for Nauset Barrier Beach and Orleans Town Beach, Cape Cod, MA : report to the Town of Orleans

(Woods Hole Oceanographic Institution, 1998-04) Aubrey, David G. ; Robertson, William

The present study investigated the shoreline and dune changes occurrng along Nauset Barrier Beach system during the past sixty years, based on examination of aerial photographs, charts, and other data sources. Significant changes have occurred to the barrier beach and dune systems of Nauset during the fifteeen intervening years since the last major study of the system. The barrier and shoreline in general has continued to retreat, and nearly all the dunes along South Spit have eroded away during storms, so the new profile of the South Spit is extremely low lying and storm waves overtop it frequently. Overwash has resulted in closing off South Channel which separates the Spit from New Island. Dunes near Aspinet Road have been eroded away, causing increased flooding of Aspinet Road. Extensive previous research performed on erosion rates are consistent with the present rates. However, present data from this report include more up-to-date photographs, and include specific attention to dune retreat and recent tidal inlet migration and number of inlets. Such decadal updates on the behavior of Nauset Barrier Beach and the adjacent Orleans Town Beach can provide valuable timely information for assessing management practices for this region.
Dynamic response of electromagnetic current meters

(Woods Hole Oceanographic Institution, 1984-05) Aubrey, David G. ; Spencer, Wayne D. ; Trowbridge, John H.

The dynamic response of electromagnetic current meters (manufactured by Marsh-McBirney, Inc.) has been clarified through a comprehensive laboratory measurement program combined with a thorough literature review. Elucidation of the behavior of these flowmeters under a variety of dynamic conditions has been neglected in the past. Since flow past a spherical body has considerable hydrodynamic complexity for different dynamic conditions, a careful laboratory study was carried out for pure steady, pure oscillatory (horizontal plane), and combined steady/oscillatory conditions at two test facilities. Test results indicate that flowmeter behavior under pure steady flow is excellent in the absence of high levels of free-stream turbulence, with an r.m.s. error of 1-5 cm/sec. These errors could· be reduced with a higher-order polynomial regression fit. Pure oscillatory response was also excellent, with r.m.s. errors of 1-2 cm/sec, and sensitivity which is correlated with the oscillatory Reynolds number, (Re)o, and the Keulegan-Carpenter number, (A/d). Combined steady/oscillatory flows degraded current meter performance with larger residual errors (1-6 em/sec) and significant differences in sensitivity (up to 20°/o). Horizontal cosine response showed systematic deviations from pure cosine behavior, with a notable inter-cardinal undersensitivity and cosine "shoulder" at lower Reynolds numbers. Error analysis shows these current sensors are adequate for many kinematic measurements, but may lead to excessive errors when using velocity to calculate dynamical quantities (such as bottom friction, Reynolds Stress, or log-layer friction velocities). A careful error analysis must precede any use of these meters for estimating dynamical quantities. These studies pointed out a potential difficulty in using these meters in areas of large ambient turbulence levels (20°/o turbulent intensities), which are characteristic of many near-bottom shallow water environments. Further study is needed to clarify this behavior.
Survey of shoreline structures, Popponesset Beach, MA

(Woods Hole Oceanographic Institution, 1983-05) Goud, Margaret R. ; Aubrey, David G.

The structures along a 12 km section of the shoreline of Cape Cod, Mass., were evaluated for condition and effectiveness at protecting the coast. Structures in the area include groins, jetties, revetments, and seawalls; each has been located, photographed and described. The region has been subject to erosion in recent years, including the loss of a 1 km section of barrier spit. The role of shoreline structures in controlling or enhancing the erosion was examined as part of a larger study of coastal processes in the area. The shoreline structures serve two primary functions: beach enhancement and protection of the bluffs from erosion. The structures• effects on bluffs and beaches in their immediate vicinity (approximately lOOm along the coastline to the north and south of the structure) are detailed in this report. Seawalls generally protect the cliffs into which they are built without enhancing erosion of surrounding bluffs, though the bluffs are protected at the expense of the beaches in the central area (Meadow Point). Large scale changes in beach configuration are not primarily caused by local, small-scale structures, but rather by a more regional paucity of sand input into the system. This scarcity is caused in part by large jetties controlling inlet flows to Waquoit Bay, which impedes free transport of sand into the area.
Development, characteristics, and effects of the new Chatham Harbor inlet

(Woods Hole Oceanographic Institution, 1989-06) Giese, Graham S. ; Aubrey, David G. ; Liu, James T.

A new tidal inlet into Chatham Harbor, Massachusetts, has developed from a breach in the barrier beach, Nauset Beach, that forms the outer shoreline of southeastern Cape Cod. Increased tidal range and wave energy resulting from the new inlet produced acute coastal erosion and channel shoaling within Chatham Harbor, with significant impacts on the fishing and boating industries, and on private and public propeny and interests. Study results are consistent with the hypothesis that the Nauset-Monomoy barrier beach system undergoes a long-term cycle of geomorphological change, and that a new cycle was initiated with the formation of this new inlet. Based on this new understanding, future changes in the system can be foreseen and provided to coastal resource managers.
Hydroblack 91 : report of the CTD Intercalibration Workshop

(Woods Hole Oceanographic Institution, 1992-02) Aubrey, David G. ; Oguz, T. ; Demirev, E. ; Ivanov, V. ; McSherry, T. R. ; Diaconu, V. ; Nikolaenko, E.

An Intercalibration Workshop was held at the Woods Hole Oceanographic Institution (W.H.O.I.) from 1-10 December, 1991, for the CTD data acquired during HYDROBLACK '91. This intercalibration exercise was a prelude to an interdisciplinary HYDROBLACK '91 intercalibration to be held in Crimea, Ukraine, in February, 1992, incorporating the full suite of physical, biological, and chemical measurements acquired during the cruise. HYDROBLACK '91 acquired for the first time a complete hydrographic, biological, and chemical data set for the entire Black Sea, to 200 m water depth, with the participation of all Black Sea riparian countres as well as the U.S. Nearly 300 hydrographic stations were occupied to full water depth; biological and chemical measurements were made at 100 of these stations. This quasi-synoptic survey was accomplished using five ships during an interval of approximately three weeks. Results show some disparities between CTD's from the different regions, but the intercalibrated results show a consistent and high resolution detail of the dynamic topography and other physical characteristics of the entire Black Sea basin. The intercalibrated data set is now available within each country and from W.H.O.I., and will form the basis for studies on ocean physics as well as interdisciplinary issues such as oxygen depletion within the basin and hydrogen sulfide distribution. This effort provides an intercalibrated, spatially-dense baseline against which all future and past measurements can be compared. In spite of significant economic pressures arising from the changes in the eastern European countries, and the inadequate scientific exchange with the west during the past two decades, HYDROBLACK '91 is considered a success and a model for future international scientific and monitoring efforts thoughout the Black Sea. Similar efforts are anticipated twice-yearly in the framework of the new Cooperative Marine Science Program for the Black Sea.
Tidal observations at Ria Formosa, Algarve, Portugal

(Woods Hole Oceanographic Institution, 2000-05) Salles, Paulo ; O'Malley, Stephen P. ; Voulgaris, George ; Aubrey, David G.

The apparent persistence and stability of multiple tidal inlets in coastal lagoons are important for a variety of reasons, such as water quality, navigability and beach/barrier stability. To identify and study the processes controlling the persistence of multiple tidal inlets, the hydrodynamics of the system have to be better understood. This project is part of a larger study (INDIA) examining general tidal inlet processes. The present components consist of a numerical simulation study of processes controlling multiple inlet stability, combined with exhaustive field measurements. This report addresses only the second component. The analysis uses as study site and main source of data the Ria Formosa lagoon in Portugal, which has multiple and historically persistent inlets. For the numerical simulation model, field measurements are needed to provide (i) updated bathymetry of the inlets, in situ measurements of (ii) water level fluctuations within the estuary and (iii) flow velocities through the inlets. This report gives first a brief description of the instrumentation used in the field (section 2), then describes the methods used to deploy the instruments, perform the surveys and gather the data (section 3), explains the procedures for data reduction and show some results (section 4 and Annex).
Sedimentation study, Environmental Monitoring and Operations Guidance System (EMOGS), Kings Bay, Georgia and Florida, 1988-1990 : final report

(Woods Hole Oceanographic Institution, 1991-07) Aubrey, David G. ; McSherry, T. R. ; Spencer, Wayne D.

Repeated side-scan sonar and multi-frequency bathymetric surveys, accompanied by accurate, high resolution, and repeatable navigation, were conducted in the vicinity of a tidal inlet to define the length and time scales associated with bedforms and channel shoaling in a structured tidal inlet. The study site, St. Marys entrance channel along the Georgia/Florida border (Fig. 1), has a dredged channel approximately 46-52 feet in depth at a datum of mean low water (MLW), bordered by a large ebb tidal delta. The tidal inlet serves Cumberland Sound, Kings Bay, and associated waterways, providing a large discharge of water from the inlet that creates bedforms and channel shoaling, given the abundance of sand-size sediment in the vicinity. The jettied inlet produces flows that are predominantly tidally-driven, whereas farther offshore the driving forces consist predominantly of waves and storm-generated flows. In the channel reaches (Table 1) between these two areas, combined wave/steady flows are present, creating a myriad of scales of bedforms and shoaling patterns, emphasizing the difference in these scales between the three different flow regimes. The results provide an important data base for quantifying shoaling processes and mechanisms in tidal inlet channels.
Coastal sediment transport, Popponesset Beach, MA

(Woods Hole Oceanographic Institution, 1983-08) Aubrey, David G. ; Goud, Margaret R.

Pathways and rates of near-bed sediment transport near Popponesset Beach, MA ., were calculated using several distinct techniques. For the nearshore platform, sand transport in the form of sand waves was determined from vertical aerial photography spanning periods of four decades. In addition, calculations based on theoretical and empirical equations for near-bed sediment transport were made using field measurements of wind waves and tidal currents. Net sediment transport to the southwest inferred from these two techniques differed by about a factor of five. The higher net transport rate predicted in the aerial photographic method is a result of lack of wave measurements during storm conditions. Storm waves increase the net transport through a local increase in bed shear stress. Net transport to the southwest across the platform is between 700 and 3300 m3/yr. Littoral sand transport along Popponesset Beach was calculated from one month of directional wave measurements, extrapolated to a yearly value using long-term meteorological observations. Littoral transport from these calculations is 10,000 m3/yr to the northeast, opposite the sense of alongshore transport in the shallow nearshore. Patterns of shoreline change are discussed from a historical perspective, and using the transport calculations discussed above. Several management alternatives for coping with predicted shoreline change are presented for consideration by the Town of Mashpee.

Aubrey David G.

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