Coarse Sand Beaches Research Articles

Vulnerability of the East Coast of Balikpapan City in East Kalimantan (Lamaru Beach - Klandasan Beach)

Balikpapan City located in the east coast of Kalimantan Island. The city of Balikpapan is directly adjacent to the Makassar Strait. The problem faced by Balikpapan City is the function of the land, namely the reclamation of the construction of shopping centre which results in changing the shape of the coast so that it has the potential to experience abrasion. In the city of Balikpapan for the past 6 years there has been an abrasion of 40 meters which has resulted in a decrease in Regional Original Income (PAD). Research on the vulnerability of the east coast of Balikpapan City to changes in coastline in 2005 and 2018 was focused on the calculation of social vulnerability and changes in coastline analyzed using crosstab. This study divides the area based on the shape of the beach, namely fine sand beaches, coarse sand beaches, and thick beaches. Based on the results of the analysis there are three levels of vulnerability, namely low, medium, and high. Areas with a high level of vulnerability are found in the rough sand segment. The level of vulnerability is along the fine sand beach segment and the low level of vulnerability is along the shore coast segment.

Numerical modelling of the flow and bed evolution of a single bore-driven swash event on a coarse sand beach

This paper examines the numerical prediction of the sediment transport and bed evolution for a single swash event on a coarse sediment beach. In these conditions bed load is the dominant mode of sediment transport. Laboratory experiments of a single bore-driven swash event are simulated numerically using a fully-coupled model that solves the system of Non Linear Shallow Water Equations and the Exner sediment conservation formula. The analysis focuses on two aspects: the optimal choice of parameters for the Meyer-Peter and Müller sediment transport formula and the model used for computing the shear stress. The methods tested for the bed shear stress are the momentum integral method and the Chezy formulation in which the friction factor is computed using two different formulae. Infiltration into the beach and its effects on the shear stress and sediment transport are also modelled. Results show that the basic Meyer-Peter and Müller sediment transport formula provides good results in the run-up. On the other hand, the sediment transport in the early stage of the backwash is overestimated. A reduction of the sediment mobility constant in the formula in the backwash marginally improves the results. However, the causes of the overestimation of the sediment transport at the early stage of the backwash is the overestimation of the shear stress, while at later stages there are several contributions that are identified, i.e. modelling of the sediment transport and infiltration. It is also suggested that the Meyer-Peter and Müller sediment transport formula might not capture the complexity of the processes involved during the backwash. The comparison of the methods for the estimate of the bed shear stress show that comparable results can be obtained using the momentum integral method and the Chezy formulation with time and space varying friction factor. The resulting bed evolution is also described. In the predicted final profile, deposition is found in the upper part of the beach and erosion in the lower part. A bed step is formed just below the position of the initial shoreline. This feature is determined by the onset of a hydraulic jump during the backwash.

Estimating the speed of poroelastic interface waves using ambient noise

Pairs of hydrophones were buried at mid-tide height in a 1:10 sloped mixed gravel and coarse sand beach and used to make ambient noise recordings over a period of three weeks in Advocate Harbour, Nova Scotia, in the Bay of Fundy. The pairs were arranged in vertical and horizontal configurations and recorded pressure time series, power spectral density, and vertical and horizontal coherence measurements of the noise field in the seabed. A nearby suite of oceanographic instruments measured the water level, ocean wave properties, bed dynamics and weather during the experiment. The measured noise between 1 Hz and 1 kHz was dominated by poroelastic interface waves generated by plunging surf on the beach face. The speed of the compressional component of the interface wave was estimated by cross-correlating the noise recorded on the across-shore oriented pair of sensors while the unconsolidated sediment was water-saturated as well as drained. Additionally, the increasing and decreasing overburden pressure due to the rising and falling 10-m tide was found to drive a respective increase and decrease in the poroelastic interface wave speed. A buried acoustic source was used to directly measure the compressional wave speed in the seabed on the across-shore array.

Intra-swash hydrodynamics and sediment flux for dambreak swash on coarse-grained beaches

The paper reports on dambreak-type swash experiments in which intra-swash hydrodynamics and sediment flux are measured for swash on a coarse sand beach and a gravel beach. Flow velocity and depth are measured using PIV and LIF respectively; the intra-swash sediment flux is measured using sediment traps. Comparison of measured hydrodynamics with the immobile, permeable bed experiments of Kikkert et al. (2013) indicates that bed mobility impacts on the swash hydrodynamics, reducing the maximum run-up by approximately 8% for both beaches, compared to the maximum run-up on the corresponding immobile beach. The measured intra swash sediment flux at a given location is characterised by high flux at the moment of bore arrival, followed by rapid decay during uprush, becoming zero at some time before flow reversal. For the gravel beach, the backwash sediment flux is negligibly small, while for the sand beach the backwash flux increases slowly as the flow accelerates down the beach, and peaks at about the time of maximum backwash velocity. Intra-swash sediment flux calculated using the Meyer-Peter and Müller bed load transport formula, with measured hydrodynamics as input and bed shear stress estimated using both the Swart and Colebrook formulae, is within a factor 2 of the measured intra-swash flux. The agreement between the calculated and measured flux is better for the sand beach than for the gravel beach, and better for uprush than for backwash. For the sand beach there is good agreement between calculated and measured total uprush and total backwash sediment volumes. The agreement is less good for the gravel beach, for which calculated and measured uprush volumes show a similar trend but the calculated backwash volumes over-estimate the (negligible) volumes observed in the experiments.

Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part II: Sediment transport

This is the second of two papers on the 3D numerical modeling of nearshore hydro- and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross- and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., k-e, k-L, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the k-e and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model’s ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance.

OCCURRENCE OF THE INTERSTITIAL OPISTHOBRANCH UNELA REMANEI MARCUS, IN THE CARIBBEAN SEA

Five specimens of the opisthobranch snail Unela remanei Marcus were found in a coarse sand beach at Santa Marta, Columbia The animals are briefly described. This is the second of this species, which was hitherto only known from Brazil.

Sediment transport partitioning in the swash zone of a large-scale laboratory beach

Swash zone sheet flow and suspended sediment transport rates are estimated on a coarse sand beach constructed in a large-scale laboratory wave flume. Three test cases under monochromatic waves with wave heights of 0.74m and wave periods of 8 and 12.2s were analyzed. Sediment flux in the sheet flow layer exceeds several hundred kgm−2s−1 during both uprush and backwash. Suspended sediment flux is large during uprush and can exceed 200kgm−2s−1. Instantaneous sediment flux magnitudes in the sheet layer are nearly always larger than those for suspended sediment flux. However, sediment transport rates, those integrated over depth, indicate that suspended load transport is dominant during uprush for all cases and during the early stages of backwash except in the case for the 12.2s wave case when the foreshore was steeper. Results could not be obtained for an entire swash event and were particularly truncated during backwash when water depths fell below the elevation of the lowest current meter.

EXPERIMENTAL STUDY ON BORE-INDUCED SWASH INTERACTIONS

The current study reports the results from a new laboratory experimental investigation, carried out to improve understanding and modeling of the internal kinematics of swash interactions, and its role on beach face morphology. Two typical types of swash interactions, wave capture interaction and backwash interaction (Erikson et al., 2005), were observed in detail by conducting large-scale dam-break experiments in a flume with two adjacent reservoirs and a fixed coarse-sand beach. The experiments were designed to enable detailed measurements of swash depths, velocity fields and turbulent quantities at different locations across the swash zone to be obtained.

Numerical experiments on breaking waves on contrasting beaches using a two-phase flow approach

A mechanistic understanding of beach environments needs to account for interactions of oceanic forcing and beach materials, in particular the role of waves on the evolution of the beach profile. A fully coupled two-phase flow model was used to simulate nearshore fluid-sediment turbulent flow in the cross-shore direction. It includes the Reynolds-Averaged Navier–Stokes equations and turbulent stress closures for each phase, and accounts for inter-granular stresses. The model has previously been validated using laboratory-scale data, so the results are likely more reliable for that scale. It was used to simulate wave breaking and the ensuing hydrodynamics and sediment transport processes in the surf/swash zones. Numerical experiments were conducted to investigate the effects of varying beach and wave characteristics (e.g., beach slope, sediment grain size, wave periods and heights) on the foreshore profile changes. Spilling and plunging breakers occur on dissipative and intermediate beaches, respectively. The impact of these wave/beach types on nearshore zone hydrodynamics and beach morphology was determined. The numerical results showed that turbulent kinetic energy, sediment concentrations and transport rate are greater on intermediate than on dissipative beaches. The results confirmed that wave energy, beach grain size and bed slope are main factors for sediment transport and beach morphodynamics. The location of the maximum sediment transport is near the breaking point for both beach types. Coarse- and fine-sand beaches differ significantly in their erosive characteristics (e.g., foreshore profile evolutions are erosive and accretionary on the fine and coarse sand beaches, respectively). In addition, a new parameter (based on main driving factors) is proposed that can characterize the sediment transport in the surf and swash zones. The results are consistent with existing physical observations, suggesting that the two-phase flow model is suitable for the simulation of hyper-concentrated mixed water-sediment flows in the nearshore. The model thus has potential as a useful tool for investigating interactions between nearshore hydrodynamics and beach morphology.

Numerical experiments on interactions between wave motion and variable-density coastal aquifers

A comprehensive two-dimensional (cross-shore) process-based numerical model of nearshore hydrodynamics (based on the Navier–Stokes equations, k–ε turbulence closure and the Volume-Of-Fluid method), beach morphology, and variable-density groundwater flow (SEAWAT-2000) was developed. This model, which was applied at the field scale, relaxes simplifications in existing models that do not include such detailed mechanistic descriptions. Numerical experiments were conducted to investigate the effects of varying aquifer, beach and wave characteristics (e.g., inland groundwater head, sand grain size, different wave heights and periods) on the coupled system. Spilling and plunging breakers on dissipative and intermediate beaches were simulated. For a given set of boundary conditions, the model was run for 1y without the hydrodynamic sub-model to achieve a realistic salt-/freshwater interface. Then, the hydrodynamic component was run for 15min and the model results analyzed. The main features considered were groundwater circulation, saltwater wedge position, in/exfiltration across the beach face, and beach morphology. The predictions of the numerical model agree well with existing understanding and experimental measurements. For an inland watertable that is lower than the still water level (SWL), such that the groundwater flow is mainly landward, on both coarse and fine sand beaches the addition of wave motion moves the saltwater wedge further landward. For an inland watertable that is higher than the SWL, the opposite behavior occurred. The numerical experiments showed that more sediment transport takes place on intermediate beaches than on dissipative beaches. In addition, beach profile variations are greater under plunging breakers, while coarse sand beaches are steeper than fine sand beaches for the same wave conditions. There is a strong correlation between in/exfiltration and beach face deposition/erosion for the coarse beaches, while in/exfiltration has a slight effect on sediment transport for fine beaches. The model is capable of simulating the short-term evolution of foreshore profile changes, and beach watertable and saltwater wedge movement due to interactions between wave motion and coastal groundwater.

Introduction to a Special Issue

Boston Harbor Islands national park area includes 34 discrete islands and peninsulas, ranging in size from small rock outcrops (e.g., The Graves, Little Calf Island) to Worlds End, a complex of woodland, grassland, freshwater and coastal wetlands, and intertidal habitats (Fig. 1). Given a large mean tidal range of 2.9 m (9.5 ft) within Boston Harbor, many of the islands have extensive intertidal areas of sandflats and mudflats, cobble and coarse sand beaches, salt marshes, and rocky shores. Intertidal areas are almost equal to the terrestrial area of the islands (Table 1). A geographic grouping of the islands would include the outer islands or Brewster Islands, the inner islands or Dorchester Bay Islands, the Quincy Bay Islands, and the Hingham Bay Islands. Aside from the few outcrops of exposed bedrock, most of the islands are geologically classified as drumlins, elongate landforms of unconsolidated glacial tills (Rosen and Leach 1987). As these drumlin islands erode, the sediment is reworked to form sand and gravel spits, beaches, and tombolos (beaches or bars connecting islands to each other or the mainland). The park includes approximately 55 km (34 mi) of shoreline, most of which is relatively undeveloped. All of the islands have a rich history of human use; many islands have structures, and some islands (e.g., Deer, Little Brewster, and Thompson) are still occupied with institutional uses. These various landforms, the interface of marine and terrestrial environments, and past land use within an urban region all contribute to a diversity of habitats found throughout the islands. Visitors to the national park area are likely to be drawn to the different habitats that are represented, the historical and cultural attractions, and the beaches and recreational facilities.

BURROWING AND SWASH BEHAVIOR OF THE PACIFIC MOLE CRAB HIPPA PACIFICA (ANOMURA, HIPPIDAE) IN TROPICAL SANDY BEACHES

To investigate factors associated with the distribution of an intertidal crab, Hippa pacifica Dana, which is common in the swash zones of reflective subtropical and tropical sandy beaches, we examined the effect of sediment size on burrowing rates of a wide size range of individuals. We also examined aspects of swash behavior in field conditions, including drift time, distance and velocity of individual crabs. Hippa pacifica burrowed very rapidly (in 0.3 to 2.7 s) in laboratory and field conditions. Burrowing time increased significantly with increasing crab size in all sediments tested but did not differ between male and female crabs nor between ovigerous and non-ovigerous crabs. There were no significant differences in burrowing times among five sediments ranging from very fine sand to gravel, suggesting that this species is a sediment generalist whose distribution is not limited by sediment size. Individual crabs released in the swash zone of a reflective beach oriented, swam and/or drifted for 1.2 to 3.8 seconds before contacting substrate and burrowing. Drift times were similar for all sizes of crabs. However, drift distance (ranging 0.10 m to 1.16 m) and drift velocity (ranging 0.11 m/s to 0.45 m/s), decreased with increasing crab size, suggesting a possible mechanism for size-specific zonation patterns reported in this species. Burrowing times observed in H. pacifica in this study were faster than reported for other sandy beach macrofauna, including tropical forms. This burrowing ability, in combination with the characteristics of substrate generalist and well-oriented swash behavior, appear to be a key to the ability of H. pacifica to inhabit reflective coarse sand beaches.

Burrowing and Swash Behavior of the Pacific Mole Crab Hippa Pacifica (Anomura, Hippidae) in Tropical Sandy Beaches

To investigate factors associated with the distribution of an intertidal crab, Hippa pacifica Dana, which is common in the swash zones of reflective subtropical and tropical sandy beaches, we examined the effect of sediment size on burrowing rates of a wide size range of individuals. We also examined aspects of swash behavior in field conditions, including drift time, distance and velocity of individual crabs. Hippa pacifica burrowed very rapidly (in 0.3 to 2.7 s) in laboratory and field conditions. Burrowing time increased significantly with increasing crab size in all sediments tested but did not differ between male and female crabs nor between ovigerous and non-ovigerous crabs. There were no significant differences in burrowing times among five sediments ranging from very fine sand to gravel, suggesting that this species is a sediment generalist whose distribution is not limited by sediment size. Individual crabs released in the swash zone of a reflective beach oriented, swam and/or drifted for 1.2 to 3.8 seconds before contacting substrate and burrowing. Drift times were similar for all sizes of crabs. However, drift distance (ranging 0.10 m to 1.16 m) and drift velocity (ranging 0.11 m/s to 0.45 m/s), decreased with increasing crab size, suggesting a possible mechanism for size-specific zonation patterns reported in this species. Burrowing times observed in H. pacifica in this study were faster than reported for other sandy beach macrofauna, including tropical forms. This burrowing ability, in combination with the characteristics of substrate generalist and well-oriented swash behavior, appear to be a key to the ability of H. pacifica to inhabit reflective coarse sand beaches.

Is Sandy Beach Macrofauna Only Physically Controlled? Role of Substrate and Competition in Isopods

Exposed sandy beaches have been defined as physically stressful environments, so that benthic populations living there are thought to be regulated mainly by physical factors, biological interactions being minimal. However, recent long-term studies indicate that potential intra- and interspecific interactions should also play a role in structuring populations and communities. This paper evaluates the role of sediment characteristics and potential interactions in determining the abundance and distribution patterns of the cirolanid isopodsExcirolana armataandExcirolana braziliensisin sandy beaches of Uruguay. Results from concurrent field sampling and laboratory experiments showed that: (1) at a macroscale (between beaches),E. armataoccurred only in beaches with fine sands, whereasE. braziliensiswas observed in both fine and coarse sand beaches, reaching its highest density in the latter; (2) at a mesoscale (within beaches) and in sympatry (fine sands), both cirolanids showed maximum densities at different tidal heights, withE. braziliensisrestricted to the upper beach levels; (3) both isopods showed a clear preference for fine sands, when tested in isolation or combined; (4) survivorship ofE. armatawas higher when tested in the preferred sediment under co-occurrence withE. braziliensis, which in turn presented higher survivorship in coarse sand, either in isolation or combined withE. armata; and (5) individual mean length of both species was consistently higher in allopatry, and similar body lengths were observed in sympatric populations. A geographical analysis of the abundance ofE. braziliensisalong Pan-American beaches showed that this isopod is most abundant in fine sands; this overall pattern supports conclusions derived from sediment preference experiments, implicating a greater niche breadth than that observed in Uruguayan beaches. It was concluded thatE. armatacould be defined as a high substrate-specific species in which intraspecific interactions would be of utmost importance in population regulation. However, distribution patterns ofE. braziliensiscould not be explained by a simple animal-sediment relationship, and correlational evidence suggests that it is displaced byE. armatatowards coarse sands and upper beach levels. Thus, potential biotic interactions cannot be discarded as a structuring force in sandy beach communities.

Influence of tide and waves on washout of dissolved nutrients from the bioremediation zone of a coarse-sand beach: Application in oil-spill bioremediation

Successful bioremediation of oil-contaminated beaches requires maintenance of a sufficient quantity of growth-limiting nutrients in contact with the oiled beach material. A conservative tracer study was conducted on a moderate-energy, sandy beach on Delaware Bay to estimate the washout rate for dissolved nutrients from the bioremediation zone at different stages during the lunar tidal cycle. When an aqueous solution of the conservative tracer (LiNO 3) was applied to the beach surface in the upper intertidal zone at the full moon spring tide, it was completely removed within one day. When it was applied at neap tide, however, the tracer persisted in the bioremediation zone for several days. The amount of nutrient remaining in the bioremediation zone was highly correlated with the maximum extent to which the treated area had previously been submerged by water at high tide: submergence resulted in nearly complete removal of dissolved compounds from the bioremediation zone. This high rate of nutrient washout was confirmed by daily monitoring of nutrient concentrations in the bioremediation zone during an oil-spill bioremdiation field study that was conducted on a nearby beach.

Subaqueous Grain Flows at the Head of Carmel Submarine Canyon, California

ABSTRACT The head of Carmel Submarine Canyon lies in 15 m of water about 200 m off a coarse-sand beach in the southeast corner of Carmel Bay, California. Very coarse sand is the predominate material on the beach, adjacent shelf, and upper canyon-head slopes, while silt and clay cover the surface below a water depth of about 35 m. Along a shore-normal transect, median grain size decreases between the beach and canyon rim but increases down the upper canyon-head slope. On angle-of-repose slopes in the upper canyon head, downslope-coarsening deposits, which are everywhere there is active sand movement, are similar to a type of sediment gravity flow deposit formed by grain flows (sand avalanches). Using three sand fractions that were dyed different fluorescent colors, scuba divers generated sand avalanches that produced deposits similar to the natural deposits. The dyed-sand deposits, which extended as far as 25 m below the initiation point, were inversely graded and increased in grain size downslope. Inverse grading was well developed within two m of the initiation point, though the thicknesses of the three layers varied in a nonsystematic manner both across and down slope. The minor amount of native material found within the dyed-sand layers showed hat entrainment of the underlying sand was minimal.

High-frequency sediment-level oscillations in the swash zone

Sediment-level oscillations with heights of about 6 cm and shore-normal lengths of order 10 m have been measured in the swash zone of a high-energy, coarse-sand beach. Crests of oscillations were shore parallel and continuous alongshore. The oscillations were of such low steepness (height-to-length ratio approximately 0.006) that they were difficult to detect visually. The period of oscillation ranged between 6 and 15 min and decreased landward across the swash zone. The sediment-level oscillations were progressive landward with an average migration rate in the middle to upper swash zone of 0.8 m min −1. Migration was caused mostly by erosion on the seaward flank of the crest of an oscillation during a period of net seaward sediment transport. Thus, the observed migration was a form migration landward rather than a migration involving net landward sediment transport. The observed sediment-level oscillations were different than sand waves or other swash-zone bedforms previously described.

Swash Mark and Grain Flow

ABSTRACT Swash marks composed entirely of coarse sand are commonly found on coarse-sand beaches. These swash marks are 10 to 30 centimeters in width and a few millimeters to one centimeter in height. Previous observations, mostly on finer-sand beaches, indicate swash marks are seldom over a few millimeters in height and are commonly composed of material readily floated by surface tension (e.g., mica flakes and shell fragments). Swash marks composed of coarse sand have both fining seaward and fining with depth trends in grain size. Apparently, the leading margin of a wave upwash drives a highly concentrated flow of grains in which both grain size and grain velocity decrease with depth. Therefore, large grains are transported at greater velocities than are smaller grains. Thus, at the maximum advance of an upwash, a swash mark is deposited which has the observed fining seaward and fining with depth trends in grain size.

First record of a free-living dalyellioid turbellarian from the pacific:Balgetia pacifica nov. spec.

Balgetia pacifica nov. spec. from coarse sand beaches along the west coast of San Juan Island (Washington) is described and its taxonomy discussed. The species is characterized by its large bursal apparatus with a strengthened copulatory bursa.B. pacifica is the first free-living species of the Turbellaria Dalyellioida recorded from the Pacific Ocean.

TheUrquiola oil spill, La Coruña, Spain: Impact and reaction on beaches and rocky coasts

The supertankerUrquiola grounded, exploded, and burned at the entrance to La Coruna harbor (Spain) on May 12, 1976. A total of 100,000 tons of Persian Gulf crude oil was lost, of which about 30,000 tons washed onto shoreline environments. From May 17 to June 10, 1976, the impact and interaction of oil on fine-sand, coarse-sand, and gravel beaches and on sheltered and exposed rocky coasts was monitored in detail. At 32 localities, the beach was profiled, trenched, extensively sampled, and photographed. Another 67 stations were examined for surficial oil coverage and distribution. The surficial distribution of oil on the beaches was influenced primarily by wave activity, tidal stage, and oil quantity. Heaviest accumulations formed along the high-tide swash line. Within beach sediments, oil was present at distinct oiled sediment layers, which were often deeply buried. The depth of burial was related to wave energy and sediment type. Deepest burial (1 m) was on a high-energy, coarse-sand beach (Mz=0.82φ). Burial on fine-sand beaches was less than 30 cm. The thickness of oiled sediment depended on sedimentary characteristics, the quantity of oil present, wave action, and capillary forces. Oil-soaked sediment, as much as 65-cm thick, occurred on coarse-grained beaches. On fine-sand beaches, oiled sediment was limited to thicknesses of 10 cm or less. On rocky shores, oil distribution was determined primarily by wave energy. Along high-energy, cliffed, or steeply dipping rocky areas, wave reflection kept the oil approximately 5 m offshore and contamination was minimal. In low-energy, sheltered areas, oil readily accumulated, causing apparent environmental damage.