A Moisture Balance Reconstruction for the Drainage Basin of Albemarle Sound, North Carolina

Freshwater discharge into Albemarle Sound and many other large estuaries can have a major impact on the physical and biological properties of the estuary. Earlywood (EW) and latewood (LW) width tree ring chronologies recently developed from ancient trees and sub-fossil logs found at Devil’s Gut of the Roanoke River, North Carolina, were used with new EW and LW width data from Blackwater River, Virginia, to reconstruct the July Palmer Hydrological Drought Index (PHDI) over the drainage basin of Albemarle Sound from 934 to 2005. This reconstruction is based on a principal component regression using millennium-long chronologies of both EW and LW widths, calibrated and verified against instrumental July PHDI from 1895 to 1985. The reconstruction provides a lengthy representation of inter-annual to multi-decadal growing season moisture variability that directly affects water quality in the Albemarle Sound estuarine ecosystem. Single-year drought and wetness extremes were more common in the modern instrumental period (1895–2005), but prolonged droughts reconstructed during the Medieval and Early Colonial eras were more severe and sustained than the reconstructed or observed droughts during the twentieth century. Several abrupt transitions between decadal drought and wetness regimes are reconstructed, especially during the Medieval Era. Composite analysis of lower-magnitude sub-decadal regime shifts in the instrumental record during the twentieth century indicates that major changes in mid-latitude circulation over the Northern Hemisphere may have been involved in these longer decadal transitions between moisture regimes over Albemarle Sound in prehistory.     

Potential competition between hybrid striped bass (Morone saxatilis × M. americana) and striped bass (M. saxatilis) in the Cape Fear River estuary, North Carolina

Gillnet surveys from 1990 to 1992 and from 1996 to 1999 indicated a two-fold decrease in native striped bass (Morone saxatilis) populations and a concomitant two-fold increase in hybrid striped bass (Morone saxatilis × M. americana) in the Cape Fear River estuary, North Carolina. Gut content analysis indicated high diet overlap, and tagrecapture data suggested that hybrid striped bass participate in spawning migrations. These data provide circumstantial evidence that hybrid striped bass compete with striped bass for food and that they may compete for mates or habitat on the spawning grounds. Increasing abundance of adult hybrid striped bass in this system elevates the likelihood of hybrid introgression. We recommend that stocking of hybrid striped bass be terminated to preserve native striped bass populations.     

Sediment evolution and habitat function of organic-rich muds within the Albemarle estuarine system,North Carolina

The analyses of 248 samples have revealed that the composition and distribution patterns of sediments within the Albemarle estuarine system (AES) represent a complex interaction between multiple sediment sources, basin morphology and evolution, and associated estuarine processes. Three sediment end-member types are dominant: sand, peat, and organic-rich mud (ORM). Throughout the AES, shallow perimeter platforms and associated sediment-bank shorelines are eroded into Pleistocene units. Shoreline recession supplies sand to the platforms and mud to the central basins; these sediments mix with suspended sediment from the fluvial drainages. Swamp forest-peat and marsh-peat shorelines are actively eroding and supply fine organic detritus to produce the dominant ORM sediment in the central basins. Perimeter platform sands grade into ORM on the platform slope. ORM constitutes about 70% of the benthic habitats within the AES and has an average composition of 76.2% inorganic mud, 13.1% sand, and 10.7% organic matter. The characteristics of ORM greatly affect the benthic community structure, chemical quality of the sediments, and the water quality of the estuary. ORM readily moves in and out of the water column in response to natural and anthropogenic activities, affecting water column turbidity and trace and major element geochemistry. Organic matter and clay minerals in ORM are chemically reactive and interact with the water column to adsorb or release contaminants, nutrients, and gases. Thus, ORM acts as both a sink and source for many different chemical constituents in the water column and plays important, but poorly understood, functions in the physical and chemical dynamics of estuarine ecosystems.     

Coastal saltmarsh development at Southern Topsail Sound,North Carolina

Topsail Sound is a marsh-filled barrier lagoon in southeastern North Carolina. This study quantified changes within a 477-ha tidal marsh located landward of Lea and Coke islands in southern Topsail Sound. Aerial photographs from 1949, 1966, and 1984 were enlarged, and sample areas of salt marsh were digitized and compared. Since 1949, Old Topsail Inlet has migrated southwest 1.2 km. As the inlet migrated, new Spartina alterniflora marsh colonized 33.2 ha of intertidal sand flats within the inlet flood tidal delta, adjacent islands, and primary tidal creeks. Landward of the flood tidal delta, site specific gains and losses of marsh were recorded. It is estimated that since 1949, approximately 34.1 ha of the marsh area occupying the zone landward of the flood tidal delta has drowned. This loss of marsh, combined with the colonization of marsh mentioned above, resulted in a net decrease of 1 ha in the total area of marsh. This study provides evidence that, although lagoonal marshes may be drowning as a result of soil waterlogging, reduced sediment supply, and sea-level rise, potential marsh environments are created by oceanic inputs of sand when inlets migrate.     

Relationship of larval-stage growth and mortality to recruitment of striped bass,Morone saxatilis, in Chesapeake Bay

Variable recruitments of striped bass were hypothesized to be caused by factors influencing growth and survival of larvae. Eggs and larvae were collected in the Potomac River from 1987 to 1989 and in the Upper Chesapeake Bay in 1988 and 1989 to estimate abundances, larval growth and survival rates, and environmental variability. Larval batch dates, ages, and growth and mortality rates were estimated from analysis of otolith daily increments. A retrospective analysis of Potomae River ichthyoplankton data from 1974–1977 and 1980–1982 provided additional estimates of larval abundances and vital rates for comparative purposes. Significant correlations betweens vital rates (growth and mortality) and abundances of striped bass larvae, and the Maryland juvenile recruitment index indicated that recruitment level may be fixed during the larval stage. The ratio of mean daily growth and mortality rates (G:Z) of larvae in the Potomac River for 1987–1989 was highest in 1987 when the juvenile index was relatively high, and was lower in 1988 and 1989 when juvenile indices were low. In the Upper Bay, mean larval growth rate, survival rate, and the G:Z ratio were highest in 1989 when the juvenile index also was high. In both tributaries, abundances of late-stage larvae (8 mm SL) were correlated with juvenile-stage recruitment indices. The retrospective analysis provided additional evidence that Potomac River larval abundances and G:Z ratios were positively correlated with juvenile recruitment indices in the 1974–1977 and 1980–1982 periods. Conditions favoring striped bass larval abundance and potential recruitment differed between the Potomac River and the Upper Bay. In the Potomac, late-stage larval abundances coincided with late-season water temperatures that were relatively warm, low river discharges and high, late-season densities of zooplankton prey, which favored larval growth. In the Upper Bay, the high abundance of late-stage larvae in 1989 relative to 1988 was attributed to a higher egg production that was coincident with high zooplankton abundances.     

Serum and blood from adult striped bass,Morone saxatilis

Results of blood and serum analyses on striped bass,Morone saxatilis (Walbaum), adults taken during the 1975 spawning season on the Nanticoke River, Maryland, are reported. The range in values found were 16–70% for hematocrit, 4.0–12.3 g/100 ml for hemoglobin, 2.86–4.49×10⁶/cc for erythrocyte count, 4.5–18.8 mg% for serum calcium, and 6.1–13.0 g/100 ml for plasma protein. These values are compared with others previously reported for adult bass. Serum chloride and serum protein values, ranging from 80 to 186 mEq/l and 3.92 to 8.32 g%, respectively, are reported for the first time for this species. Hemoglobin and hematocrit values for non-spawning, mature striped bass held in ambient sea water for a year fall within the reported ranges. Serum total protein values ranged from 2.36 to 6.14 g% and serum calcium values varied between 8.1 and 14.9 mg% from migratory adult striped bass. The possibility of sexing striped bass using serum calcium levels is discussed. Hematological values reported will help in defining the range encountered in healthy adults of this species.     

Recruitment and growth of the Eastern oyster,Crassostrea virginica,in North Carolina

The effects of location, salinity, and depth on recruitment and growth of the eastern oyster Crassostrea virginica in Pamlico and Core sounds, North Carolina, were investigated from 1988 to 1990. We measured length and density of spat settling on oyster cultch deployed at deep (～3 m) and shallow (～1 m) depths at six sites in areas with low salinity and six sites in areas with high salinity. These data were compared with similar data taken at some of these sites by the North Carolina Division of Marine Fisheries since 1981 as part of their cultch planting program. Recruitment was generally greater in the high salinity sites, compared to the low salinity sites. Recruitment was less at shallow depths compared to deeper depths. In all three years the highest recruitment occurred in August and September, corresponding to the months of maximum water temperature. Recruitment was highly variable in space and time, but appeared to diminish from 1988 to 1990. Recruitment was reduced by sedimentation and a variety of sessile organisms. All sites appeared to have a similar potential for growth.     

Relationship between waterfowl and American coot abundance with submersed macrophytic vegetation in Currituck Sound,North Carolina

Waterfowl and American coot data collected from aerial censusing on Currituck Sound were compared during three periods: before Eurasian watermilfoil (Myriophyllum spicatum) colonization (1961–1965); during Eurasian watermilfoil infestation (1968–1977); and following the near absence of submersed macrophytic vegetation after Eurasian watermilfoil decline (1981–1990). Numbers of dabbling ducks (Anas rubripes, Anas platyrhynchos, Anas acuta, Anas americana, Anas crecca), ring-necked ducks (Aythya collaris), and American coot (Fulica americana) were significantly different in Currituck Sound (p<0.05) in at least two of these periods and were highest during Eurasian watermilfoil infestation. These species also constituted higher percentages of the Atlantic Flyway counts during Eurasian watermilfoil infestation. than in periods before or after. Numbers of snow geese (Chen caerulescens), Canada geese (Branta canadensis), and canvasbacks (Aythya valisneria) were significantly different between periods; however, these birds exhibited a consistent decline from the early to the late period. This study suggests that submersed macrophytes, specifically Eurasian watermilfoil, support increased numbers of dabbling ducks, ring-necked ducks, and American coot.     

Rapid Holocene coastal change revealed by high-resolution micropaleontological analysis, Pamlico Sound, North Carolina, USA

Foraminiferal analyses of 404 contiguous samples, supported by diatom, lithologic, geochronologic and seismic data, reveal both rapid and gradual Holocene paleoenvironmental changes in an 8.21-m vibracore taken from southern Pamlico Sound, North Carolina. Data record initial flooding of a latest Pleistocene river drainage and the formation of an estuary 9000 yr ago. Estuarine conditions were punctuated by two intervals of marine influence from approximately 4100 to 3700 and 1150 to 500 cal yr BP. Foraminiferal assemblages in the muddy sand facies that accumulated during these intervals contain many well-preserved benthic foraminiferal species, which occur today in open marine settings as deep as the mid shelf, and significant numbers of well-preserved planktonic foraminifera, some typical of Gulf Stream waters. We postulate that these marine-influenced units resulted from temporary destruction of the southern Outer Banks barrier islands by hurricanes. The second increase in marine influence is coeval with increased rate of sea-level rise and a peak in Atlantic tropical cyclone activity during the Medieval Climate Anomaly. This high-resolution analysis demonstrates the range of environmental variability and the rapidity of coastal change that can result from the interplay of changing climate, sea level and geomorphology in an estuarine setting.     

Prey density requirements of the striped bass,Morone saxatilis (Walbaum), larvae

Striped bass,Morone saxatilis, larvae of 9 DAH (days after hatching) were fed for 16 d with five densities of adults (5–100 l^?1), copepodites (10–200 l^?1), and nauplii (50–1,000^?1) of the copepodEurytemora affinis, and 5-DAH and 10-DAH larvae were fed at seven densities (5–500 l^?1) of brine shrimp,Artemia salina, nauplii. The study determined the effects of prey types and densities on the survival and growth of the fish larvae, and the effects of delaying first feeding from 5 DAH to 10 DAH. The survival and grwoth of the larvae fedE. affinis adults was higher than those fedE. affinis copepodites.E. affinis nauplii were the poorest prey. OneE. affinis adult provided nutrition equivalent to 1.45 copepoditer or 11.12 nauplii. The percentage survival of the larvae was higher for those fedA. salina nauplii thanE. affinis adults at the densities below 67.25 l^?1, but there was no difference at this density or higher. Delaying first feeding from 5 DAH to 10 DAH did not affect percentage survival and size of larvae at the end of the experiments. Because the survival and growth of the larvae increased as the prey density increased, it was difficult to set a point along the regression line as the minimum density requirement level. It may be said that for striped bass larvae, the higher the prey density, the higher the survival and growth, and thus the greater the recruitment success.     

Comparative growth of juvenile white sturgeon and striped bass: Effects of temperature and hypoxia

The influences of temperature and environmental hypoxia on the growth rates of two California anadromous fishes, white sturgeon (Acipenser transmontanus) and striped bass (Morone saxatilis) were examined. Fish (0.5–0.6 g initial weight) were fedad libitum rations ofArtemia in flow-through aquaria regulated for temperature (15, 20, and 25°C) and oxygen tension (130 and 90 torr P_{o 2}). Growth of sturgeon was significantly greater at 20 °C compared with 15 °C, but there was no difference between 20 and 25 °C. Striped bass growth increased with each 5° increment of temeprature elevation to 3.2% body weight per d at 25 °C, the fastest growth rate measured. The temperature of maximum growth reflected the temperature of the native estuarine rearing area. Environmental hypoxia (90 torr P_{o 2}) reduced growth of sturgeon within each temperature level, whereas striped bass growth was reduced by hypoxia only at the upper two temperatures. Sturgeon were much more active in the growth chambers than striped bass. Sturgeon activity increased with each 5 °C temperature increase under normoxia and hypoxia, except at 25 °C (hypoxia) where activity was insignificantly different from that at 20 °C (hypoxia).     

A geochemical atlas of North Carolina, USA

A geochemical atlas of North Carolina, U.S.A., was prepared using National Uranium Resource Evaluation (NURE) stream-sediment data. Before termination of the NURE program, sampling of nearly the entire state (48,666 square miles of land area) was completed and geochemical analyses were obtained.The NURE data are applicable to mineral exploration, agriculture, waste disposal siting issues, health, and environmental studies. Applications in state government include resource surveys to assist mineral exploration by identifying geochemical anomalies and areas of mineralization. Agriculture seeks to identify areas with favorable (or unfavorable) conditions for plant growth, disease, and crop productivity. Trace elements such as cobalt, copper, chromium, iron, manganese, zinc, and molybdenum must be present within narrow ranges in soils for optimum growth and productivity. Trace elements as a contributing factor to disease are of concern to health professionals. Industry can use pH and conductivity data for water samples to site facilities which require specific water quality.The North Carolina NURE database consists of stream-sediment samples, groundwater samples, and stream-water analyses. The statewide database consists of 6,744 stream-sediment sites, 5,778 groundwater sample sites, and 295 stream-water sites. Neutron activation analyses were provided for U, Br, Cl, F, Mn, Na, Al, V, Dy in groundwater and stream water, and for U, Th, Hf, Ce, Fe, Mn, Na, Sc, Ti, V, Al, Dy, Eu, La, Sm, Yb, and Lu in stream sediments. Supplemental analyses by other techniques were reported on U (extractable), Ag, As, Ba, Be, Ca, Co, Cr, Cu, K, Li, Mg, Mo, Nb, Ni, P, Pb, Se, Sn, Sr, W, Y, and Zn for 4,619 stream-sediment samples. A small subset of 334 stream samples was analyzed for gold.The goal of the atlas was to make available the statewide NURE data with minimal interpretation to enable prospective users to modify and manipulate the data for their end use. The atlas provides only very general indication of geochemical distribution patterns and should not be used for site specific studies. The atlas maps for each element were computer-generated at the state's geographic information system (Center for Geographic Information and Analysis [CGIA]). The Division of Statistics and Information Services provided input files. The maps in the atlas are point maps. Each sample is represented by a symbol generally corresponding to a quartile class. Other reports will transmit sample and analytical data for state regions. Data are tentatively planned to be available on disks in spreadsheet format for personal computers.During the second phase of this project, stream-sediment samples are being assigned to state geologic map unit names using a GIS system to determine background and anomaly values. Subsequent publications will make this geochemical data and accompanying interpretations available to a wide spectrum of interdisciplinary users.     

Aging and growth of larval bay anchovy,Anchoa mitchilli,from the Newport River estuary,North Carolina

Bay anchovy (Anchoa mitchilli) larvae were hatched and reared in the laboratory from eggs collected near Beaufort, North Carolina. The first growth increment formed on otoliths on the fifth day after hatching when larvae were between 3.7 and 4.2 mm standard length. On the average, one otolith growth increment was formed per day thereafter in larvae up to 23 d posthatch. Age of wild larvae from the Newport River estuary in North Carolina was determined from otolith increment counts based on the assumption that increment deposition rates in nature are the same as in the laboratory. From their size and estimated age, it appears that the standard length (SL) of wild larvae in the estuary increases exponentially at about 4% d^?1 during their first 1.6 months, increasing from 0.24 mm d^?1 on day 12 to 1.11 mm d^?1 on day 49. Bay anchovy spawned early in the season (e.g., April–May) could grow to maturity and reach a size (>40 mm SL) that would enable them to spawn during their first summer.     

Food of Paralichthys dentatus and P. lethostigma (Pisces: Bothidae) in North Carolina estuaries

The diets of the spatially segregated summer flounder, Paralichthys dentatus, and southern flounder, P. lethostigma, in Pamlico Sound, North Carolina, were composed of crustaceans and fishes. Young flounders fed mainly on mysids and fishes throughout the year, but the ratios of these items differed between species. Feeding was minimal during winter, but summer flounder from near-inlet stations had a high frequency of stomachs with food. Older summer flounder fed equally on shrimp and fishes, while southern flounder fed almost solely on fishes. This difference was probably related to food availability.     

Ecological response to hurricane events in the Pamlico Sound system, North Carolina, and implications for assessment and management in a regime of increased frequency

Since the mid 1990s, the Atlantic and Gulf Coast regions have experienced a dramatic increase in the number of hurricane landfalls. In eastern North Carolina alone, eight hurricances have affected the coast in the past 9 years. These storms have exhibited individualistic hydrologic, nutrient, and sediment loading effects and represent a formidable challenge to nutrient management aimed at reducing eutrophication in the Pamlico Sound and its estuarine tributaries. Different rainfall amounts among hurricanes lead to variable freshwater and nutrient discharge and variable nutrient, organic matter, and sediment enrichment. These enrichments differentially affected physical and chemical properties (salinity, water residence time, transparency, stratification, dissolved oxygen), phytoplankton primary production, and phytoplankton community composition. Contrasting ecological responses were accompanied, by changes in nutrient and oxygen cycling, habitat, and higher trophic levels, including different direct effects on fish populations. Floodwaters from the two largest hurricances, Fran (1996) and Floyd (1999), exerted, multi-month to multi-annual effects on hydrology, nutrient loads, productivity, and biotic composition. Relatively low rainfall coastal hurricanes like Isabel (2003) and Ophelia (2005) caused strong vertical mixing and storm surges, but relatively minor hydrologic and nutrient effects. Both hydrologic loading and wind forcing are important drivers and must be integrated with nutrient loading in assessing short-term and long-term ecological effects of these storms. These climatic forcings cannot be managed but should be considered in the development of water quality management strategies for these and other large estuarine ecosystems faced with increasing frequencies and intensities of hurricane activity.     

The influence of nitrogen level,form, and application method on the growth response ofSpartina alterniflora in North Carolina

The influence of nitrogen level, form, and application method on the growth response of short and tallSpartina alterniflora was determined in a North Carolina salt marsh. The application of various nitrogen levels increased the aerial standing crop of shortSpartina as much as 172%, but had no significant effect on that of the tall form. Band application produced a significantly greater yield response than broadcast application in both height forms. The yield of shortSpartina increased significantly more from ammonium fertilization than from nitrate, while there was no significant effect of nitrogen form on tallSpartina. Band application of ammonium-nitrogen fertilizer significantly increased the yield of shortSpartina more than band application of nitrate-nitrogen and broadcast application of either nitrogen form.     

Petrology of the Mecklenburg gabbro-metagabbro complex,North Carolina

The Mecklenburg complex, which crops out in the Carolina Piedmont, consists of older metagabbro and metafelsic rocks of upper amphibolite grade, and a younger postmetamorphic gabbro. On the evidence of field data and gravity measurements, the younger gabbro appears to be a plug-like body with steeply dipping contacts that may converge inward at relatively shallow depth; the pluton may extend only 8,000–15,000 feet into the subsurface.Gabbroic rocks contain plagioclase, olivine, orthopyroxene, clinopyroxene, hornblende, and biotite, and display hypidiomorphic textures characterized by numerous reaction relations among the mafic phases; hydrous minerals are commonly abundant, comprising up to 37% of the rock, and indicate the fugacity of H₂O was relatively high during primary crystallization. In contrast metagabbro lacks olivine and exhibits textures that range from relict igneous varieties to crystalloblastic types that appear to represent equilibrium assemblages. A less common metagabbro type, associated with local zones of deformation, is characterized by faint banding and only trace amounts of anhydrous mafics. Varieties of metagabbro are complexly intermingled in the field, and resultant assemblages and textures largely reflect whole-rock composition and differences in initial H₂O contents, slightly modified locally by addition of fluid along favorable channelways.In general metagabbro is slightly higher in TiO₂, Na₂O, and K₂O, and lower in MgO relative to gabbro; regardless of the degree of recrystallization, the chemistry of the various metagabbro types is nearly identical, thus indicating metamorphism was essentially isochemical.     

Origin and differentiation of Triassic dolerite magmas,North Carolina,USA

Ten dolerite dikes intruded into Triassic fault troughs in the Piedmont area of North Carolina have been analyzed for the contents of major elements plus selected trace elements. The average composition of the initial magma, as indicated by four chill margins for major elements and three for trace elements, is: SiO₂, 48.6%; Al₂O₃, 16.9%; TiO₂, 0.57%; Fe₂O₃, 3.30%; FeO, 6.72%; MgO, 10.59; CaO, 10.42%; Na₂O, 2.03%; K₂O, 0.20%; MnO, 0.20%; Rb, 2.6 ppm; Sr, 133 ppm; Zr, 46 ppm; Th, 0.4 ppm; and U, below detection limit of approximately 0.1 ppm. One large dike (BP) exhibits a Palisades-type of differentiation by crystal settling of olivine, and the comparatively thick JY dike shows development of micropegmatite toward the center; the smaller dikes, however, are relatively homogeneous across their width. Study of the relationship between SiO₂ content and the ratio FeO+Fe₂O₃/MgO+ FeO+Fe₂O₃ indicates that most dikes crystallize under conditions of decreasing oxygen pressure, but the differentiation trend of the JY, RD, and RS dikes indicates either constant or increasing oxygen pressure during their evolution.Statistical comparison of the composition of the initial dolerite magmas with a variety of basalt types around the world suggests that the North Carolina dolerites are far more similar to oceanic or oceanic margin tholeiites than to continental tholeiites. The North Carolina rocks are distinctly different from plateau basalts but are similar to the chill zones of the Precambrian Bushveld and Stillwater lopoliths. The comparatively low contents of Th, U, and Sr, plus the relatively high K/Rb ratio all support the possibility that the magmas for the North Carolina dolerites evolved in a dominantly oceanic environment. It seems distinctly possible that continental-type crust and mantle did not exist in the Appalachian Piedmont area in Triassic time, even after major orogeny and the concurrent formation of granitic intrusions.     

Quaternary depositional patterns and sea-level fluctuations, northeastern North Carolina

A detailed record of late Quaternary sea-level oscillations is preserved within the upper 45 m of deposits along an eight km transect across Croatan Sound, a drowned tributary of the Roanoke/Albemarle drainage system, northeastern North Carolina. Drill-hole and seismic data reveal nine relatively complete sequences filling an antecedent valley comprised of discontinuous middle and early Pleistocene deposits. On interfluves, lithologically similar marine deposits of different sequences occur stacked in vertical succession and separated by ravinement surfaces. Within the paleo-drainage, marine deposits are separated by fluvial and/or estuarine sediments deposited during periods of lowered sea level. Foraminiferal and molluscan fossil assemblages indicate that marine facies were deposited in a shallow-marine embayment with open connection to shelf waters. Each sequence modifies or truncates portions of the preceding sequence or sequences. Sequence boundaries are the product of a combination of fluvial, estuarine, and marine erosional processes. Stratigraphic and age analyses constrain the ages of sequences to late Marine Isotope Stage (MIS) 6 and younger (∼ 140 ka to present), indicating multiple sea-level oscillations during this interval. Elevations of highstand deposits associated with late MIS 5 and MIS 3 imply that sea level was either similar to present during those times, or that the region may have been influenced by glacio-isostatic uplift and subsidence.     

Transverse structure of residual flow in North Inlet,South Carolina

Transverse distributions of the depth-averaged, axial residual current across the mouth of North Inlet are computed. A numerical model is used in which the acceleration at any point of the section is governed by a balance between surface slope forcing, friction, and viscous drag. Computed velocities are compared with observations taken over three tidal cycles. The transverse structure of residual flow is similar to that described by the model. However, an additional circulation pattern is present in the data and may be due to advective effects.