Estuarine Shoreline Research Articles

Impact of land-use change and hard structures on the evolution of fringing marsh shorelines

Estuarine fringe marshes provide essential ecosystem services to coastal regions, including carbon sequestration and provision of shelter and nursery grounds for aquatic and terrestrial animals. The ability of a marsh to sustain itself by vertical accretion in response to sea-level rise is, in part, limited by inorganic sediment supply. Models attempting to forecast salt-marsh response to future sea-level rise commonly ignore land-use changes, despite the recent coastal population boom and the potential of land-use changes to alter sediment sources and modify established sediment-transport pathways. This study investigates the impacts of landscape modifications, which are typical of coastal areas, on the nearshore sedimentation and edge evolution of two fringing marshes. The sites examined include a marsh fringing the upper bay and a marsh fringing a beach ridge on the estuarine shoreline of a barrier island. Both sites are located in the same estuarine system, have similar hydrologic settings and comparable vegetation densities. Previous work, marsh cores, and a historical record from aerial photos indicate that although the fringe marshes are in different geomorphic locations, prior to anthropogenic modifications they were similar in terms of nearshore-sediment composition, scarp-shoreline morphology, and shoreline trajectory. The upper-bay marsh was impacted by the introduction of tree farming in the watershed of a tributary creek to the upper bay, which increased upland erosion and caused higher sedimentation rates in the estuary. The back-barrier marsh, which received no contribution from the tree farm because it is distal with respect to river input, was modified by the installation of a pier and rock sill. Terrestrial LIDAR, surface elevation tables, and accretion rates obtained from radioisotope analyses show that the deforestation induced high rates of nearshore and marsh accretion at the upper-bay site, which is promoting marsh colonization and expansion. These same types of data, in addition to aerial photos, were obtained at the back-barrier site and show increased rates of marsh-shoreline erosion adjacent to the structures. The fringing marshes were once similar, but started to evolve differently over a short time period as a result of human-induced changes to the landscape. Coastal development can significantly influence marsh-shoreline behavior, which must be taken into account when developing models of coastal response to sea-level rise.

Spatial Patterns of Plastic Debris along Estuarine Shorelines

The human population generates vast quantities of waste material. Macro (>1 mm) and microscopic (<1 mm) fragments of plastic debris represent a substantial contamination problem. Here, we test hypotheses about the influence of wind and depositional regime on spatial patterns of micro- and macro-plastic debris within the Tamar Estuary, UK. Debris was identified to the type of polymer using Fourier-transform infrared spectroscopy (FT-IR) and categorized according to density. In terms of abundance, microplastic accounted for 65% of debris recorded and mainly comprised polyvinylchloride, polyester, and polyamide. Generally, there were greater quantities of plastic at downwind sites. For macroplastic, there were clear patterns of distribution for less dense items, while for microplastic debris, clear patterns were for denser material. Small particles of sediment and plastic are both likely to settle slowly from the water-column and are likely to be transported by the flow of water and be deposited in areas where the movements of water are slower. There was, however, no relationship between the abundance of microplastic and the proportion of clay in sediments from the strandline. These results illustrate how FT-IR spectroscopy can be used to identify the different types of plastic and in this case was used to indicate spatial patterns, demonstrating habitats that are downwind acting as potential sinks for the accumulation of debris.

Estuarine shoreline processes in a dynamic low-energy system

Estuarine shorelines are often classified as low-energy coasts and are, therefore, expected to undergo little variation. Port Stephens (SE Australia) is a ria-like drowned river valley microtidal estuary located on a wave-dominated coast. The outer part of the estuary is tide-dominated and has a large shallow flood-tide delta, which is also affected by waves. The northern (predominantly low-energy) shoreline of outer Port Stephens is a continuous stretch of sand comprising areas of high mobility and areas of relative stability terminating in a western extending sand spit. This paper investigates the effects of periodic high-energy conditions during which waves penetrate into the estuary by analysing two types of storms, low to moderate (more frequent type) storms and severe to extreme (low frequency) storms. It is established that low to moderate storms cause generalised erosion over the northern shoreline. On the contrary, severe to extreme storms, while causing erosion on parts of the beach, can transport new sediment across the flood-tide delta and deposit it to build a mobile shore attached sandwave. Long-term (decadal) trends identified in the study area are in agreement with short- and medium-term results. Moving into the estuary are four complementary zones of sediment transport which include: (1) sandwave formation and westward migration; (2) a relatively stable area between the sandwave and an erosion zone; (3) an erosion zone undergoing shoreline retreat and finally (4) a depositional terminus causing westward extension of the sand spit.

Human‐Transported Material Soils of Urbanizing Estuarine Landscapes

Additions of human‐transported materials (HTM) have significantly altered many coastal shorelines and wetlands. The hydrology and the ability of these anthropogenic soils to support ecologically important functions is poorly understood. In this study, we documented soil hydrologic patterns along disturbed estuarine shorelines and wetlands. Our goal was to determine if the soils had properties relative to the potential to support denitrification (i.e., labile C, saturation, and reducing conditions). Eleven anthropogenic sites, located in Rhode Island and 30 to &gt;60 yr old, were studied. Auger transects were completed to characterize anthropogenic soils. Water table levels were monitored twice a month. Anthropogenic soils were described and sampled from pits at five representative locations. Soil organic C (SOC), permanganate‐oxidizable C (POC), bulk density, and pH were measured. Deposits of HTM, comprised of dredge and fill materials, ranged in thickness from 26 to &gt;285 cm, were predominantly sandy and often contained artifacts. In the thickest HTM deposits, water table levels rose as much as 2.5 m above the original buried soil surface. Redoximorphic features were identified within the range of water table activity in 16 of the 18 monitored anthropogenic soils, suggesting reducing conditions. Soil organic C ranged from 1.6 to 88.9 g kg−1, was highest in surface horizons, and had an irregular distribution with depth. Labile C, estimated from POC measurements, followed the SOC distribution. Evidence of labile C, saturation, and reducing conditions in the majority of these soils suggest that most of the disturbed estuarine soils we studied have the capacity for denitrification.

Common reed Phragmites australis occurrence and adjacent land use along estuarine shoreline in Chesapeake Bay

We completed a shoreline survey of Phragmites occurrence and adjacent land use along more than 8,400 km of shoreline in the Maryland and Virginia portions of the Chesapeake Bay and its tidal tributaries. Phragmites occurred along 14.6% of Maryland estuarine shoreline in the mid-to-upper portion of Chesapeake Bay, but along only 2.0% of the surveyed Virginia shoreline in the mid-to-lower portion. The dramatic difference in occurrence was not related exclusively to high salinity restrictions on plant distribution in the lower portion of the bay since most of the survey was completed in mesohaline to oligohaline sections of the estuary. Phragmites occurrence was highest—up to 30% of all shoreline—in the upper northeastern section of the bay and was over-represented adjacent to cleared but undeveloped land. Although Phragmites was found growing adjacent to all types of land uses including undisturbed forest in the mid-to-upper estuary, its occurrence was positively correlated with the percentage of agricultural shoreline. The extensive Phragmites occurrence throughout the upper estuary suggests that both local and regional environmental factors of management concern may contribute to the suspected spread of Phragmites along both Maryland and Virginia shoreline.

Organizing the manufacture of Bondi points at Balmoral Beach, Middle Harbour, Sydney, NSW, Australia

AbstractAnalysis of the stone artefact assemblage excavated from a stratified midden in a sandstone rockshelter at Balmoral Beach in Middle Harbour, Sydney, has revealed various strategies were adopted in manufacturing asymmetric backed artefacts, also known as Bondi points. The irregular morphology of many Bondi points and the small size of most in this assemblage suggest a need to economize and improvise, which we propose was due to the relatively limited availability of suitable stone materials in coastal Sydney. It was not only a question of distance to source and access but of abundance—there are few sources of suitable stone close to Balmoral Beach. The documented technological organization shows that people at Balmoral Beach were creatively backing flakes in several different ways to produce Bondi points with standardized width and thickness—length of the complete Bondi points was seemingly not as important. This observation, combined with the evidence that some broken Bondi points were re‐worked, is discussed in the context of reliability and maintainability, design principles that may have been adopted for their manufacture.

Geospatial Analysis of Barrier Island Width of Two Segments of the Outer Banks, North Carolina, USA: Anthropogenic Curtailment of Natural Self-Sustaining Processes

A comparison of two sections of the Outer Banks, North Carolina, USA (Pea Island and Avon-Buxton areas), reveals the importance of the interplay between oceanic and estuarine shoreline dynamics to long-term changes in barrier island width. From 1852 to 1998, the northern portion of Pea Island experienced an average net increase in width of 431 m (3 m/y); this area experienced low to moderate rates of oceanic shoreline erosion and high rates of back-barrier land accretion via overwash and formation of flood tidal delta islands. In contrast, between 1852 and 1998, the width of the southern portion of Pea Island and the Avon-Buxton area decreased an average of 515 m (4 m/y) and 594 m (4 m/y), respectively, because of high rates of oceanic shoreline erosion and variable changes in estuarine shoreline accretion and erosion. Net gain or net loss of barrier island width is strongly dependent on the natural depositional processes of overwash and flood tide delta formation. Anthropogenic modifications to the barrier island, such as construction of barrier dune ridges, planting of stabilizing vegetation, and urban development, can curtail or even eliminate the natural, self-sustaining processes of overwash and inlet dynamics.

Utilization of a citizen monitoring protocol to assess the structure and function of natural and stabilized fringing salt marshes in North Carolina

Narrow fringing salt marshes dominated by Spartina alterniflora occur naturally along estuarine shorelines and provide many of the same ecological functions as more extensive marshes. These fringing salt marshes are sometimes incorporated into shoreline stabilization efforts. We obtained data on elevation, salinity, sediment characteristics, vegetation and fish utilization at three study sites containing both natural fringing marshes and nearby restored marshes located landward of a stone sill constructed for shoreline stabilization. During the study, sediment accretion rates in the restored marshes were approximately 1.5- to 2-fold greater than those recorded in the natural marshes. Natural fringing marsh sediments were predominantly sandy with a mean organic matter content ranging between 1.5 and 6.0%. Average S. alterniflora stem density in natural marshes ranged between 130 and 222 stems m−2, while mean maximum stem height exceeded 64 cm. After 3 years, one of the three restored marshes (NCMM) achieved S. alterniflora stem densities equivalent to that of the natural fringing marshes, while percentage cover and maximum stem heights were significantly greater in the natural than in the restored marshes at all sites. There was no significant difference in the mean number of fish, crabs or shrimp captured with fyke nets between the natural and restored marshes, and only the abundance of Palaemonetes vulgaris (grass shrimp) was significantly greater in the natural marshes than in the restored ones. Mean numbers of fish caught per 5 m of marsh front were similar to those reported in the literature from marshes adjacent to tidal creeks and channels, and ranged between 509 and 634 fish net−1. Most of the field data and some of the sample analyses were obtained by volunteers as they contributed 223 h of the total 300 h spent collecting data from three sites in one season. The use of fyke nets required twice as many man-hours as any other single task. Vegetation and sediment parameters were sensitive indicators of marsh restoration success, and volunteers were capable of contributing a significant portion of the labor needed to collect these parameters.

Spatial patterns of benthic macrofauna in relation to environmental variables in an intertidal habitat in the Humber estuary, UK: Developing a tool for estuarine shoreline management

Spatial variations in benthic macrofaunal species composition, abundance and biomass in estuarine intertidal habitats have been often related to such environmental variables as salinity, sediment types and tidal depth. However, there have been few attempts to investigate the relations between such macrobenthic parameters and intertidal beach width gradient in order to predict their likely responses to coastal squeeze induced by accelerating sea-level rise in an estuarine environment. This article investigates the linkages between environmental variables and patterns in the distribution, abundance and biomass of estuarine intertidal macrobenthos in order to provide a basis for describing the effect of future sea-level rise in the Humber estuary, UK. Field surveys were conducted in September 2003 and 2004 over a variety of spatial scales based on a hierarchically scaled field study (system: 10 5 m; region: 10 5–10 4 m; local 10 4–10 3 m; transect: 10 3–10 2 m; station; 10 2–10 1 m) along two focal environmental gradients: (1) the longitudinal gradient (length of the estuary) over an entire estuarine system and (2) the beach width gradient (varying beach width altered by historic land-claim) over a sub-area of the estuary. Statistical analysis was carried out in order to identify key environmental variables and the most relevant spatial scales that best explain the observed spatial variability in macrobenthic biomasses. At the system scale, the dominant species were two bivalves Cerastoderma edule and Macoma balthica and a polychaete Nereis diversicolor, which accounted for 51.7%, 25.0% and 12.1%, respectively, of the total biomass. At the regional scale, univariate analysis showed clear trends in species richness, abundance and biomass along the longitudinal and beach width gradient. At the transect scale, multiple regression analysis revealed that the variances in biomass of M. balthica, C. edule and other remaining species as well as total macrobenthic biomass were largely explained (54–98%) by the key environmental variables, such as salinity, organic matter content, beach width and beach slope. At the station scale, the degree of variability explained by the environmental variables was markedly lower along beach width gradient (8–32%) than along longitudinal gradient (34–77%), but the analysis revealed a significant role of tidal depth along both gradients at this spatial scale. Overall, intertidal habitats with higher macrobenthic biomass were significantly positively related to higher salinity, muddier sediments, wider beach and shallower beach slope. This article indicates that such areas are currently situated around the lower and outer regions of the estuary where extensive shallow muddy intertidal areas can be found, but they will also be most susceptible to the impacts of sea-level rise due to their outer location and the shallowness of the beach in the Humber estuary.

Bacterial contamination associated with estuarine shoreline development

To examine the relationships among increasing estuarine shellfish closings due to bacterial contamination, adjacent shoreline land uses and environmental variables. A 1 year study of faecal coliform bacterial contamination of a small estuary in central NC, USA was done relative to adjacent land uses. The area has experienced rapid growth in residential shoreline development including the installation of adjacent, separate docking facilities for larger boats, each <11 slips (pseudomarina) that appear to be a single marina (individual facilities of >10 slips). Six near-shore sites were selected [old developed shore (OD), undeveloped shore (UD), two pseudomarinas (P1, P2), newly developed shore (ND) and a real marina (RM)]. Five locations were spaced along the shore near each site. Paired Thursday/Monday samples were collected biweekly (summer) and monthly (other seasons). Results indicate that OD had the highest bacteria counts followed by ND, RM and P1 & P2. Three sites (OD, ND and RM) failed to meet NC shellfishing waters standards at all locations. At the pseudomarina sites 4 of 10 locations failed to meet shellfish standards while two locations at UD failed to meet these standards. There were no significant differences between paired Thursday/Monday samples. At three sites (OD, UD and P2) bacteria counts were positively correlated with increased water level due to wind tides. Any type of estuarine shoreline development may result in closing of adjacent shellfishing waters. ND had bacterial counts second only to OD in spite of the retention of vegetated shoreline buffers and very new septic systems. As expected, the RM also failed to meet shellfish standards. Unexpectedly, only four of the 10 pseudomarina locations failed to meet the standards. Weekend boat use had no effect on bacterial counts. Surface runoff from rain and shoreline flooding from increased water levels increased bacterial counts, probably as a result of suspension of surface deposited faeces from wildlife and domestic animals. Multiple docking facilities do not necessarily result in violations of shellfish water quality standards. However, the elevated bacterial counts observed along the newly developed shore suggest caution in approving the practice of allowing individual 'oyster gardening' off private piers if the oysters are intended for human consumption. The practice of automatic closure of shellfish waters around RMs was supported. Correlations of bacterial counts with time following significant rainfall suggests a sampling strategy to separate local sources of bacteria from more remote sources thus focusing limited remedial resources more effectively.

Taxonomic sufficiency in distinguishing natural spatial patterns on an estuarine shoreline

Studies of marine benthic communities have shown that pollution impacts can often be detected without identifying taxa to the species level, thus saving considerable time and cost. We tested whether differences among unpolluted intertidal communities along weak estuarine physical gradients could similarly be detected with various species aggregates. We used a spatially hierarchi- cal sampling design to study species-rich, low-shore communities from pebble-sand beaches in Puget Sound, Washington. Previous research showed that weak north-south gradients in salinity, wave energy, and proportion of fine sediments correlate clearly with species richness of the benthic epibiota and macroinfauna. In this study, we found similar correlations with data aggregated to the family level but weaker correlations at higher levels (class, phylum, or trophic groupings). Multivari- ate analyses of community data at the species level show distinct separation among geographically distinct areas; similar spatial patterns are visible almost as clearly when data are gathered at lower resolution in the field or when species-level data are aggregated to families. Higher-level aggrega- tions cause spatial patterns to become progressively less distinct. Much of this effectiveness of family- level aggregation stems from the biota being family-rich but with few species per family. For this biota, monitoring programs using only families or other readily identifiable taxa should be able to detect many potential changes in community patterns in space or time. Incorporating occasional sur- veys using identification and analysis at the species level would add the capacity to examine biodi- versity and possible within-family changes in species abundances.

GPR investigation of multiple stage-5 sea-level fluctuations on a siliciclastic estuarine shoreline, Delaware Bay, southern New Jersey, USA

Abstract Ground penetrating radar (GPR) surveys were used to identify three distinct sea-level highstands within the oxygen isotope stage (OIS) 5-equivalent sediments of the Quaternary Cape May Formation in southern New Jersey. The three units, QCM1a, QCM1b, and QCM1c, are designated as submembers of the Cape May 1 member. The transgressive ravinement surfaces (TRS) forming the bounding unconformities of these units are recognized as laterally extensive reflections on the radar records and have been corroborated as gravel lag deposits and associated lithological discontinuities in continuous vibracores and hand-augered boreholes. GPR and lithological data have been used to interpret these highstand deposits in a sequence-stratigraphic framework. These units are thin (3 m or less), lithologically similar and present limited geomorphic expression of their individual existence beneath a low terrace (+6 m to mean sea level/MSL) on the northern margin of Delaware Bay. In the upper two units, QCM1b and QCM1a, radar surveys across subtle, bay-margin parallel, sublinear topographic highs of 3 m relief or less in the Jones Island area reveal internal structures consistent with geomorphic interpretation as stranded estuarine shorelines. The newly identified shoreline complexes are located well bayward of, and lower in elevation than, the commonly accepted +5 m to +6 m MSL OIS 5e shoreline. This older shoreline abuts the Cedarville Scarp and is attributed to the sea-level highstand associated with QCM1a. GPR was also used to accurately place vibracores for gathering samples of the three units for optically stimulated luminescence dating. Together, these three highstand deposits record sea-level fluctuations within OIS 5, at time scales shorter than those commonly recognized in the mid-Atlantic region.

Ground Penetrating Radar Analysis of an Emergent Mid-Pleistocene Estuarine Shoreline Complex, Chesapeake Bay, Maryland, USA.

ABSTRACT In northeastern Dorchester County, Maryland, 100 and 250 MHz ground penetrating radar surveys were used to define the east-west trending, linear Parsonsburg Sand deposit as a stranded estuarine shoreline complex, composed of three distinct highstand successions emplaced during climate-driven sea level cycles during the mid Pleistocene. These deposits form a broad ridge with 5 meters of relief, rising from their contact with the Kent Island Formation at + 10 m MSLto ~ + 14 m MSLalong the crest. The thin (<5 m) highstand deposits are cut into the underlying Pliocene Beaverdam and/or Miocene Pensauken Formations and overtop one another, attaining modern elevations of + 12 m, + 11 m, and + 14 m MSL, in succession. Radar facies and lithologic data were used to identify transgressive and highstand components of these deposits, as well as backbarrier, shoreface, and nearshore facies and structures which can be traced into their equivalent bay bottom facies in the adjacent Kent Island Formation. These da...

Rapid development of ferricretes on a subtropical valley side slope

Ferricretes can be formed along some valley‐side slopes in the southeastern United States coastal plain as a consequence of erosional exposure of zones of iron precipitation in areas of groundwater discharge. This mode of ferricrete formation was demonstrated due to the recession of estuarine shoreline bluffs after hurricanes in 1996. Iron‐precipitation zones exposed by bluff retreat at Flanner Beach, North Carolina in 1996 had formed indurated ferricretes by 1998. This confirms the valley‐side groundwater discharge model of ferricrete formation, and shows that, once the zone of iron precipitation is exposed, ferricrete can form in less than two years. The newly formed ferricretes also allow the identification of five distinct stages in their formation: (1) iron precipitation in the zone of water table fluctuation; (2) the formation of brittle iron‐cemented layers; (3) exposure by erosion or mass wasting and the first stage of hardening; (4) further hardening into indurated ferricrete; and (5) formation of limonite ferricretes, and impregnation with manganese oxides. The results from Flanner Beach show that the process may proceed from stages two and three to four and five in less than two years, suggesting that only short periods of stability following erosion or mass wasting episodes are necessary to allow ferricrete formation.

CRAB PREDATION, WATERBORNE CUES, AND INDUCIBLE DEFENSES IN THE BLUE MUSSEL,MYTILUS EDULIS

Inducible defenses are found in both terrestrial and aquatic organisms and appear to be a common defensive strategy of both sessile and mobile species. Here we report the presence of previously undescribed inducible defenses in marine mussels, a dominant member of temperate rocky intertidal communities. In the Gulf of Maine, estuarine shorelines with low water flow are characterized by high crab predation on the common blue mussel, Mytilus edulis, compared to nearby shore- lines with high water flow. Mussels at these high predation sites had thicker shells, relatively more shell mass, and were more tightly attached to the substrate than mussels at low predation sites. Field and laboratory experiments were used to test whether the between- site differences in these traits were the result of phenotypic plasticity. Mussels outplanted to high predation sites produced more byssal threads and attached more firmly to the substrate than did mussels outplanted to low predation sites. In the laboratory, thicker shells were induced by waterborne cues from both the common predator, Carcinus maenus, and damaged conspecifics, and these thicker shells were mechanically stronger than thinner, noninduced ones. Our results contribute to growing evidence that inducible defenses are a pervasive feature of intertidal assemblages. In addition to the bivalve example presented here, gastropods, barnacles, bryozoans, and seaweeds are also known to have inducible defenses. Phenotypic plasticity for defensive traits has likely evolved repeatedly in intertidal organisms and appears to play a major role in the dynamics of rocky intertidal communities.

Habitat quality for shallow water fishes in an urban estuary:the effects of man-made structures on growth

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 187:227-235 (1999) - doi:10.3354/meps187227 Habitat quality for shallow water fishes in an urban estuary: the effects of man-made structures on growth Kenneth W. Able1,*, John P. Manderson2, Anne L. Studholme2 1Marine Field Station, Institute of Marine and Coastal Sciences, Rutgers University, 800 Great Bay Blvd., c/o 132 Great Bay Blvd., Tuckerton, New Jersey 08087-2004, USA 2NOAA/National Marine Fisheries Service, Northeast Fisheries Science Center, James J. Howard Marine Sciences Laboratory, Sandy Hook, New Jersey 07732, USA *E-mail: able@imcs.rutgers.edu ABSTRACT: Caging experiments were conducted to determine the growth of juvenile fishes as a measure of habitat quality under large pile-supported platforms or piers, in pile fields and in open-water habitat types in shallow areas (average depth 1.1 to 3.9 m) in the Hudson River estuary in 1994. Three 10 d caging experiments were conducted in June and early July with recently settled winter flounder Pseudopleuronectes americanus (14.3 to 40.1 mm SL) and 3 experiments of similar duration in July and August with recently settled tautog Tautoga onitis (20.6 to 48.6 mm TL). For both species, within-experiment instantaneous growth rates in weight (Gw-1) were significantly higher (3-way ANOVA, Tukey's pair-wise test, p < 0.05) in pile field and open-water habitats than under the piers where fish lost weight in all of the experiments. Growth rates for individual winter flounder and tautog reached values as high as 0.09 d-1 and 0.11 d-1, respectively, in open water and pile field habitats. In addition, Gw values for both winter flounder and tautog caged under piers were not significantly different (p > 0.017, 1-sided Dunnett test with Bonferroni correction) from those of conspecifics held concurrently in the laboratory without food. These results, as well as related studies of fish distribution and abundance in the same habitats, indicate that habitat quality under the platforms of large piers (>20000 m2) is poor for juvenile fishes when compared with nearby pile field and open-water habitat types. As a result, the impacts of these structures should be considered when estuarine shorelines are developed or renovated. KEY WORDS: Habitat quality · Growth · Fishes · Urban estuary · Piers Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 187. Publication date: October 14, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Spatial and temporal variations in debris accumulation and composition on an estuarine shoreline, Cliffwood Beach, New Jersey, USA

A twelve month field investigation documents differences in cross shore accumulation and composition of debris on the dune, backbeach, and foreshore of a sandy estuarine shoreline. Debris was gathered monthly within 3 belt transects extending from the dune crest to the low tide terrace (base of the foreshore). Individual pieces of debris were classified by type, function, degree of fragmentation, length, weight, and location on the beach profile (dune, vegetated backbeach, backbeach and foreshore). Plastic comprised 42.5% and glass 29.3% of the 5793 pieces of debris that were collected. Debris was primarily consumer and household related items, and the greatest quantities of debris were found during beach user months. The cross shore spatial distribution of debris reflects the influence of wind or wave processes across the profile with small lightweight debris on the wind-dominated upper profile and heavier debris on the wave-dominated lower profile. A chi-square test revealed that more plastic was observed than expected in the dune and backbeach areas with the greatest quantities found after onshore winds. More glass was observed than expected on the foreshore where low wave energies prevent transport higher on the beach profile.

Geography and Fieldwork at the Secondary School Level: An Investigation of Anthropogenic Litter on an Estuarine Shoreline

Teaching geography within a field-based, environmental-problem-solving framework integrates geographic knowledge and practice and introduces high school students to skills required to undertake geographic research. A five-day field investigation on coastal geography was designed for juniors at a science high school in New Jersey. The goal of the field investigation was to allow students to engage in problem-solving, gather field data, apply geographic concepts and tools, and foster the ability to think critically. The purpose of the investigation was to identify the spatial distribution of litter on a beach and interpret the distribution based on physical and human processes. The field site is a 400-m-long shoreline reach in Raritan Bay, New Jersey. Students defined the term “litter” for purposes of the investigation, developed a classification system, and mapped the location and type of litter on the beach. Three sampling grids were established across the beach from the dune crest to the waterline. Students conducted topographic surveys of the sampling grids, collected litter in each grid cell, and counted, classified, and weighed the litter. Data gathered were reduced, analyzed, and interpreted based on the published literature. Findings were presented at a formal presentation on the last day of the investigation. Students submitted a written report and presented the results of the investigation at a student conference two months later. Field investigations can expose students to different methods of data sampling and measurement. Collaboration between secondary schools and universities can result in successful learning initiatives that allow students the opportunity to experience the role of a practicing professional.

The mobility of beach fill in front of a seawall on an estuarine shoreline, Cliffwood Beach, New Jersey, USA

A field investigation was conducted to identify beach change associated with emplacement of a stone seawall and beach fill designed to protect an eroding cliff near the west end of a meso-tidal estuary. Visual observations of wave processes reveal a mean breaking wave height of 0·2 m at the most exposed monitoring site, a storm-wave height of 0·43 m and a maximum longshore current velocity of 0·55 ms −1. Maximum net erosion at any one monitoring site over 44 months was 26·3 m 3 m −1 of beach, resulting in a rate of erosion of 2·3 m year −1. Up to 6·8 m 3 m −1 of eolian accretion occurred due to the overly wide nourished beach. Local differences in shoreline orientation, sheltering by headlands, position of the seawall on the beach profile, shore-perpendicular structures and sediment availability resulted in variability in beach processes and changes in beach profile. Flanking occurred at the southeast end of the seawall, where fill material bypassed the upper foreshore and moved along the low tide terrace, favored by a pronounced break in shoreline orientation. Net erosion did not occur at the west end of the seawall because sufficient fill sediment was available from updrift sources. Where no fill remained in front of the seawall, wave energy dissipation on the outer low-tide terrace at low tide and wave reflection off the structure without breaking at high tide diminished the effectiveness of wave-energy concentration and turbulence on the low-tide terrace at the base of the wall, and there was no net scour. Shore-parallel structures constructed on the low-tide terrace on meso-tidal estuarine shorelines may not require a fronting protective beach to prevent net toe scour, but nourishment may delay flanking problems on the upper foreshore at downdrift sites.

Estuarine stream piracy: Calvert County, U.S. Atlantic coastal plain

The topography of Maryland's western shore of the Chesapeake Bay shows that five steams now flowing eastward into the bay comprise the pirated (and inverted) headwaters of streams previously flowing westward from a varnished Pliocene upland now occupied by the central Chesapeake. Estuarine shoreline erosion during Pleistocene interglaciations removed the upland, exposing the upper reaches of west-flowing stream valleys. Headward (westward) erosion by east-flowing streams then occurred along existing valleys, facilitated by steep eastward gradients and easily eroded valley-floor sediments. Stream inversion may be more common than previously recognized, since any eroding shoreline causes consumption of seaward-draining watershed and steepening of gradients, thus setting the stage for eventual stream inversion.