Spencer Wayne D.

No Thumbnail Available
Last Name
Spencer
First Name
Wayne D.
ORCID

Filters

1984 - 1989 1 1990 - 1998 4
5
5
Reset filters

Settings

Search Results

Now showing 1 - 5 of 5
  • Technical Report
    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.
  • Technical Report
    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.
  • Technical Report
    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.
  • Technical Report
    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.
  • Technical Report
    Sedimentation study, Environmental Monitoring and Operations Guidance System (EMOGS), Kings Bay, Georgia and Florida : Phase III--FY 1989
    (Woods Hole Oceanographic Institution, 1990-08) 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. Mary's entrance channel along the Georgia/Florida border (Fig. I), has a dredged channel approximately 46-52 feet in depth, 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-sized sediment in the vicinity. The jettied inlet produces flows tht are predominately tidally-driven, whereas farther offshore the driving forces consist predominately 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. This study was designed to elucidate the time and space scales of these variable 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.