Seasonal changes and morphodynamic behavior of a high-energy mesotidal beach: case study of Charf el Akab beach on the North Atlantic coast of Morocco

The morphodynamic behavior of a mesotidal sandy beach was monitored during both calm and energetic conditions. Two years of seasonal surveys were carried out on Charf el Akab, a gently sloped beach in the North Atlantic coast of Morocco. The method of survey consisted of a 3D study of the beach morphological changes and provided 2 cm vertical accuracy. During the surveyed period, Charf el Akab beach underwent very energetic wave conditions, and the breaking wave height was of H _b ≥ 1.5 m. The beach is characterized by a nonpermanent swash bar and composed of well-sorted medium sand. The application of environmental parameters revealed a dissipative state with very low beach gradient which did not vary significantly over the studied period. Morphological changes consist of beach erosion and bar decay under high-energy waves, whereas the intertidal bar re-established and the beach recorded an accentuated accretion due to relatively fair weather conditions. The beach volume reveals a seasonal behavior; the sand accumulated during summer is dramatically removed during winter season. The range in beach sand volume from the most accreted to the most eroded conditions observed is about −5,493 m³. The average sand volume flux between surveys reaches −1 and 0.4 m²/day during peak erosion and accretion periods. The relationships between the wave forcing and the sand volume adjustments were examined. The sand volume change was found to be highly correlated (0.91) with the wave energy flux. The highest correspondence (0.95) was found between the sand flux rate and the wave energy flux. The wave forcing is expected to be the main factor governing beach morphodynamics at Charf el Akab site.     

Evolution of a Shallow Water Wave‐Dominated Shipwreck Site: Fougueux (1805), Gulf of Cadiz

The evolution of the shallow water wave‐dominated Fougueux wreck site in the Gulf of Cadiz was investigated through repeat bathymetric surveys, wave‐ and current‐velocity field measurements, and numerical modeling. This multidisciplinary approach was used to understand the relationships between scouring, morphodynamic change, and hydrodynamic forcing. Field experiments and numerical models indicate that wave processes dominate site evolution. Numerical model outputs indicate current velocity, bed shear stress, orbital velocity, and specially wave fraction breaking (with an increase of 45% and 135% for weak and significant storm conditions, respectively) are all amplified at the site. Scour pits 0.8 m depth inshore and 0.4 m depth offshore of the wreck are developed in response to hydrodynamic forcing. Time‐lapse bathymetric surveys quantify seasonal geomorphological change at the Fougueux. Up to 1.2 m of sediment is deposited and 0.7 m of sediment eroded in response to seasonal wave climate variation (an increase of 0.5 m for mean significant wave height, 0.9 m for significant wave height corresponding to 99% of nonexceedance probability, and 0.4 m·s⁻¹ for mean near‐bed orbital velocity during winter conditions). A two‐dimensional scour model reproduces observed seasonal scour changes. Results have direct applications at all stages of a wreck site investigation.     

Interaction of monsoonal wave, current and tide near Gopalpur, east coast of India, and their impact on beach profile: a case study

A 97-day-long record on waves and currents was obtained using wave rider buoy and current meter moored at 2.5 km off Gopalpur from 19 May to 23 August 2008 representing southwest monsoon months. A Valeport tide gauge was used to record water level at Gopalpur port. Simultaneously, beach profiles at 4 transects were monitored using real-time kinematic (RTK) global positioning system (GPS). A total of 636,167 waves were analyzed for the period; a range of 3,200–9,700 waves approach the coast in an individual day. During the study, unusual characteristics of wave were observed on July 29, 2008, with a magnitude of significant wave height, H_s = 2.85 m, maximum wave height, H_max = 5.22 m, and peak wave period, T_p = 10.2 s, and on August 11, 2008, with H_s = 2.28 m, H_max = 5.37 m, and T_p = 11.1 s. Significant beach loss was noticed during these periods, and severe erosion was recorded on August 1, 2008. Beach profile data indicates that 18–58 cu. m/m sediment was lost during the study period. The paper provides an overview of the statistical analysis of wave heights, periods, direction, and spectral energy density and explains the cause of coastal erosion and loss of sediment.     

Postglacial stratigraphic evolution of a current-influenced sandy shelf: offshore Kujukuri strandplain,central Japan

Sandy shelf sediments are important elements of clastic sedimentary systems because of their wide distribution in the geological record and their significance as hydrocarbon reservoirs. Although many studies have investigated shelf sediments influenced by waves or tidal currents, little is known about shelf sediments influenced by oceanic currents, particularly their lithofacies characteristics and stratigraphic evolution. This study investigated the stratigraphic evolution of shelf sediments off the Kujukuri strandplain facing the Pacific Ocean, which is influenced by the strong Kuroshio Current. Sediment cores were obtained from six locations on the Kujukuri shelf (34 to 124 m water depth) using a vibrocorer. The dominant lithofacies is mud-free sand with low-angle cross-lamination associated with alternating beds of finer and coarser sand with cross-lamination. These display depositional processes influenced by storm waves and the Kuroshio Current, respectively. This finding is consistent with the previously presented modern and historical observations of the Kuroshio Current and estimates of the storm-wave base. Radiocarbon dates show that the sediment succession formed during the last transgressive and highstand stages after 13·1 ka. The depositional processes during the stages represent a transition from storm waves with abundant sediment supply to both storm waves and the Kuroshio Current with sediment starvation mainly due to its trapping in the strandplain. Comparison to other Holocene–Modern shelf systems suggests that the sandy shelf successions are strongly influenced by oceanic currents under conditions of limited riverine input and open coastal geometry. The resultant sand-dominated succession is characterized by reversal of the proximal to distal grain-size trend compared to the fining for most other recognized wave/storm-dominated shelf successions. This is because of seaward increase in the influence of the Kuroshio Current. Thus, shelf deposits are naturally complex, and these may be further complicated by the additional influence of oceanic currents above the usual wave-dominated and tide-dominated end members.     

Short-term morphological change and sediment dynamics in the intertidal zone of a macrotidal beach

This paper describes the morphological and sedimentological evolution of a macrotidal beach over a 20 day period under varying hydrodynamic conditions (significant breaker heights of 0·3–2 m and tidal ranges of 2–5 m). During the field campaign, an intertidal bar developed around the mid‐tide level, migrated onshore, welded to the upper beach and was then flattened under energetic wave conditions. The bar had a wave breakpoint origin and its formation was triggered by a reduction in tidal range, causing more stationary water‐level conditions, rather than an increase in wave height. Most of the onshore bar migration took place while the bar was positioned in the inner to mid‐surf zone position, such that the bar moved away from the breakpoint and exhibited ‘divergent’ behaviour. The depth of disturbance over individual tidal cycles was 10–20% of the breaker height. Such values are more typical of steep reflective beaches, than gently sloping, dissipative beaches, and are considered to reflect the maximum height of wave‐generated ripples. The grain size distribution of surficial sediments did not vary consistently across the beach profile and temporal changes in the sedimentology were mostly unrelated to the morphological response. The lack of clear links between beach morphology and sedimentology may be in part due to shortcomings in the sampling methodology, which ignored the vertical variability in the sediment size characteristics across the active layer.     

Shoreline variability of an urban beach fronted by a beachrock reef from video imagery

This contribution presents the results of a study on the shoreline variability of a natural perched urban beach (Ammoudara, N. Crete, Greece). Shoreline variability was monitored in high spatio-temporal resolution using time series of coastal video images and a novel, fully automated 2-D shoreline detection algorithm. Ten-month video monitoring showed that cross-shore shoreline change was, in some areas, up to 8 m with adjacent sections of the shoreline showing contrasting patterns of beach loss or gain. Variability increased in spring/early summer and stabilized until the end of the summer when partial beach recovery commenced. Correlation of the patterns of beach change with wave forcing (as recorded at an offshore wave buoy) is not straightforward; the only discernible association was that particularly energetic waves from the northern sector can trigger changes in the patterns of shoreline variability and that increased variability might be sustained by increases in offshore wave steepness. It was also found that the fronting beachrock reef exerts significant geological control on beach hydrodynamics. Hydrodynamic modelling and observations during an energetic event showed that the reef can filter wave energy in a highly differential manner, depending on its local architecture. In some areas, the reef allows only low-energy waves to impinge on the shoreline, whereas elsewhere penetration of higher waves is facilitated by the low elevation and limited width of the reef or by the presence of an inlet. Wave/reef interaction can also generate complex circulation patterns, including rip currents that appeared to be also constrained by the reef architecture.     

Internal architecture of a raised beach ridge system (Anholt,Denmark) resolved by ground-penetrating radar investigations

The internal architecture of raised beach ridge and associated swale deposits on Anholt records an ancient sea level. The Holocene beach ridges form part of a progradational beach ridge plain, which has been interpreted to have formed during an isostatic uplift and a relative fall in the sea level over the past 7700 years. The ridges are covered by pebbles and cobbles and commonly show evidence of deflation. Material presumably removed from the beach ridges and adjacent swales form the present dune forms on Anholt. Ground-penetrating radar (GPR) reflection lines have been collected with 250 MHz shielded antennae across the fossil ridge and swale structures. The signals penetrate the subsurface to a maximum depth of ～ 10 m below the fossil features. The GPR data resolve the internal architecture of the beach ridges and swales with a vertical resolution of about 0.1 m. GPR mapping indicates that the Holocene beach ridges are composed of seaward-dipping beachface deposits as well as minor amounts of inland dipping deposits of wash-over origin. The beachface deposits downlap on underlying shoreface deposits, and we use these surfaces as markers of a relative palaeo-sea level. The new data indicate that the highest relative sea level at about 8.5 m was reached 6500 years ago; 700 years later the relative sea level had dropped 0.7 m indicating a change in the relative sea level around 1 mm/year. This fall in the relative sea level most likely records the influence of an isostatic rebound causing younger beach ridge deposits to indicate lower sea levels.     

Tidal currents and wind waves controlling sediment distribution in a subtidal point bar of the Venice Lagoon (Italy)

The present study aims to improve current understanding of the sedimentation of subtidal point bars, analyzing interaction between tidal currents and waves in shaping a submerged meander bend of the microtidal Venice Lagoon (Italy), and it is based on coupling of sedimentological studies, geophysical analyses and numerical modelling. The Venice Lagoon is characterized by an average depth of about 1·5 m over subtidal platforms and a mean tidal range of about 1·0 m. The morphodynamic evolution of the lagoon is strongly affected by intense seasonal windstorms, which promote the formation of wind waves triggering sediment resuspension and bottom erosion. The study channel is 70 to 100 m wide, it has a radius of curvature of about 260 m and cuts through a permanently submerged subtidal platform. Water depth ranges from 1·0 to 5·0 m below mean sea level on the subtidal platform and channel thalweg, respectively. Different from classical architectural models, the study point‐bar beds do not show sigmoidal geometries, but consist of horizontally‐bedded deposits abruptly overlying clinostratified beds. Sedimentation in the study bar is hypothesized to stem from the interaction between the in‐channel secondary helical flow, as for most meander bends, and wave winnowing of the subaqueous overbank areas. Laterally accreting point‐bar deposits point out that the curvature‐induced helical flow redistributed sediment from the channel thalweg to the bar top and contributed to the development of the ‘classical’ fining‐upward grain size trend. The marked truncation surface, separating clinostratified bar deposits from overlying horizontally‐bedded platform sediments is interpreted here as due to bar top wave‐winnowing, which also possibly promoted bank collapses. In the proposed model, sediments remobilized from bar top and subaqueous overbank areas were transported into the channel, forming peculiar ‘apron‐like’ accumulations, where sand accumulated through avalanching processes and mud settled down from suspension.     

Changes in beach water table elevation during neap and spring tides on a sandy estuarine beach, Delaware Bay, New Jersey

A field investigation of temporal and spatial changes in wind and wave characteristics, runup and beach water table elevation was conducted on the foreshore of an estuarine beach in Delaware Bay during neap (April 9, 1995) and spring (April 16, 1995) tides under low wave-energy conditions. The beach has a relatively steep, sandy foreshore and semi-diurnal tides with a mean range of 1.6 m and a mean spring range of 1.9 m. Data from a pressure transducer placed on the low tide terrace reveal a rate of rise and fall of the water level on April 16 of 0.09 mm s⁻¹ resulting in a steeper tidal curve than the neap tide on April 9. Data from three pressure transducers placed in wells in the intertidal foreshore reveal that the landward slope of the water table during the rising neap tide was lower than the slope during spring tide, and there was a slower rate of fall of the beach water table relative to the fall of the tide. Wave heights were lower on April 9 (significant height from 17.1 min records <0.16 m). The water table elevation was 0.08 m higher than the water in the bay at the time of high water, when maximum runup elevation was 0.29 m above high water and maximum runup width was 2.0 m. The elevation of the water table was 0.13 m higher than the maximum elevation of water level in the bay 74 min after high water, when wave height was 0.12 m and wave period was 2.7 s. The use of mean bay water level at high tide will underpredict the elevation of the water table in the beach, and demarcation of biological sampling stations across the intertidal profile based on mean tide conditions will not accurately reflect the water content of the sandy beach matrix.     

Beach and nearshore morphodynamic changes of the Tabarka coast,Northwest of Tunisia

Aerial photographs taken in the 1963 and 2001 and bathymetric charts, in conjunction with coastal processes are analyzed to assess changes in rate of shoreline position, seabed level, and seabed grain sizes along the Tabarka–Berkoukech beach at the north-western Tunisian coastline. The littoral cell of this beach, 12-km-long, is bounded by pronounced embayments and rocky headlands separated by sandy stretches. Although not yet very much undeveloped, this littoral is still experienced degradation and modification, especially along its shoreline, with significant coastal erosion at some places. Results obtained from analysis of shoreline position indicate that El Morjene Beach is experienced a landward retreat of more than −62 m, at a maximum rate of −1.64 m/year, whereas the El corniche beach is advanced about 16–144 m, at an average rate of 0.42 m–3.78 m/year. This beach accretion has been formed on the updrift side of the Tabarka port constructed between 1966 and 1970. Comparison of bottom contours deduced from bathymetric charts surveyed in 1881 and 1996 off the coastline between Tabarka Port and El Morjene Beach identifies erosional areas (sediment source) and accretionary zones (sediment sink). Erosion (0.87–4.35 cm/year) occurs between El kebir River Mouth and El Morjene beach, whereas accretion exists in the zone down wind of the port ranges between 0.87 and 5.21 cm/year. Morphological analyses of the shoreline and the seabed of the study nearshore area indicate that shoreline retreat corresponds to areas of seabed scour (sediment source) while shoreline accretion is associated with areas of seabed deposition (sediment sink). Furthermore, simulation of wave propagation using STWAVE model combined with grain size distributions of the seabed shows that fine sands are much dominated in depositional areas with low wave energy, whereas coarser sands in erosive zones with high wave energy. The results obtained suggest that the change of seabed morphology, wave height pattern and grain size sediment have a great influence on the modification of shoreline morphology and dynamics.     

On the use of linear stability model to characterize the morphological behaviour of a double bar system. Application to Truc Vert beach (France)

Sandy barred beaches are often characterized by the presence of rhythmic patterns such as crescentic bars. In this article, a linear stability analysis (LSA) model is used to characterize the morphological behaviour of the double bar system of Truc Vert beach. Using a limited number of combinations of representative bathymetries, wave classes and water levels, the morphodynamic response of the system is analysed, focussing on the geometrical characteristics of 3D patterns generated with the model. These characteristics are described and then compared with available observations. The shapes and the wavelengths of the instabilities predicted by the model compare well with field observations. Thus, the use of the linear stability model, with representative hydrodynamic conditions and bathymetries of the considered site, allows a characterization of the global morphodynamic behaviour of a double-barred system.     

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 Coruña 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 (M_z=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.     

波浪作用下砂质滩坝的沉积过程与沉积模式

受波浪及沿岸流影响,在滨岸地区形成的滩坝砂体是滨海（湖）带发育的主要砂体类型。目前国内外学者对滩坝沉积砂体的认识多来自于现代沉积和油气地质特征,对滩坝砂体的沉积机制和内部结构研究相对较弱。基于沉积水槽实验,采用规则波浪对沙质斜坡滨岸带进行模拟实验,观测波浪作用下滨岸带滩坝形成过程和波浪运动特征,记录波浪作用下滨岸带沙质滩坝在不同浪带平面时空演化规律。实验结果显示:波浪是改造湖岸原有沉积物的关键驱动力,波浪作用下沙质岸滩床面泥砂将发生输移运动,而滩坝是陆湖（海）泥沙在水动力驱动下搬运沉积的结果,水动力的强弱及水流结构引起泥沙在空间上的不均匀输运和分布,进而塑造不同的滩坝形态。与强波浪相关的高水位可以加速滩坝系统的形成并最终形成大规模的滩坝砂;相比之下,与较弱波浪相关的低水位只能略微改变初始沉积物形态。根据不同的沉积物特征可将实验中的滩坝系统分为三类:冲浪带和碎浪带滩坝系统近端部分的大规模厚层坝砂,破浪带和升浪带滩坝系统中部分布广泛的薄滩砂,以及位于滩坝系统中远端的弧形或平行排列的脊状、砂纹坝砂。建立了水槽实验模式下滩坝沉积模式,可用于指导油气勘探开发。     

有槽沙坝海岸交叉波浪作用下裂流特征

研究叠加波浪场作用下的裂流特征,有助于全面深入开展海岸裂流的致灾机理及风险评估。为分析水动力和水底地形共同作用下形成的裂流特征,开展了交叉叠加波浪作用下有槽沙坝海岸的裂流流动特征试验,即同时考虑沿岸地形变化（存在沟槽）和交叉波浪共同作用所形成裂流。通过对裂流槽附近ADV（Acoustic Doppler Velocimetry）流速测量结果,分析叠加波浪场和裂流沟槽同时存在时所产生的裂流分布特征。裂流中心位置和宽度受裂流槽和波浪节点共同控制,裂流长度依赖于波高和海岸坡度。无槽情况裂流的驱动力主要是由波浪沿岸不均匀所产生的平均水面沿岸压力梯度,有槽情况裂流的驱动力由平均水面沿岸压力梯度和辐射应力沿岸梯度共同决定,二者量值相对大小依赖于波浪周期。     

Relationships between hydrodynamic parameters and grain size in two contrasting transitional environments: The Lagoons of Venice and Cabras, Italy

A comparison was made of shallow water sediments from the Lagoon of Venice (LV) and the Lagoon of Cabras (LC), comparing depositional environments and exploring the relationships between hydrodynamics and sedimentological parameters. The two water bodies are very different in size (LV: 360 km²; LC: 22 km²), and the sediments predominantly consist of silty-clay (LV: Mz ≈ 26 μm; LC: Mz ≈ 6 μm). However, there are large differences between the two lagoons with respect to sand (LV: mean 19%; LC: mean ~ 3%) and clay (LV: mean 20%; LC: mean 45%) contents. The Lagoon of Venice (mean depth ~ 1 m) can be considered a tidal basin, whereas the Lagoon of Cabras (mean depth ~ 2 m) has the character of a coastal lake in which wind is the main hydrodynamic forcing factor. A comparison of sediment grain-size distributions with water circulation patterns in different parts of the lagoons highlighted some interesting differences. Grain-size analyses of samples reveal a deficiency of particles around 8 μm in the LC, which is interpreted as reflecting the transition between cohesive flocs/aggregates and non-cohesive coarser silt particles, while the transition limit in the LV is ~ 20 μm. Thus, particles are cohesive below 8 μm in the LC and below ~ 20 μm in the LV. This is probably because of the differences in the clay/silt ratio, which is much lower in the LV (~ 0.3) than in LC (~ 1), conferring a “silt-dominated network structure” on most of the LV sediments.The hydrographical data used were root mean square velocity (RMSV) and water residence time (WRT), computed under the main forcing conditions. The results show a general correlation between RMSV and sortable silt in the LC, and between RMSV and coarser sediments (63–105 μm) in the LV. Some significant differences between the lagoons were detected in the degree of correlation between WRT and grain size. Root mean square velocity (~ 7 cm s^− 1 in the LV and ~ 3 cm s^− 1 in the LC) was a greater forcing factor in the LC than in the LV. Conversely, WRT, which is on average ~ 16 days in the LV and ~ 19 days in the LC, has more influence in the LV. This study highlights the usefulness of comparing environments with different hydrodynamic energies, e.g., tidal and/or wind-driven currents, to elucidate and thereby improve our understanding of the processes governing the spatial distribution of sedimentological features, the transport mechanisms of sediments, and the relationship between them. The results demonstrate that the approach outlined in this study has the potential to provide a universal hydro-sedimentological classification scheme.     

Grain size and mineralogy of Al Batinah beach sediments,Sultanate of Oman

The nature of Al Batinah coast beach sediments in the Sultanate of Oman was investigated by the analysis of grain size and mineralogy. The beach sediments, mostly light-medium gray green, were predominantly fine sands, with the average grain size of all samples about 200 μm. Some of the particles were gravel (2–16 mm), and some were even larger pebble-size particles (16–256 mm). Some mud (sediment <63 μm) was present, mostly in the sub-tidal sediments. The majority of the samples were skewed to the coarse size with coarse tail partly due to the presence of shell fragments. Approximately 50 % of the beach sediments were quartz with different varieties based on shape and size. The second major component of beach sediment was calcium carbonate which varied from 10 to 65 %. The other components in decreasing order consisted of microbreccia, feldspar, pyroxene, igneous rock fragments, biotite flakes, and heavy minerals. The levels of carbonate were lower in NW Al Batinah coast from Harmul to Al Khaburah but were higher in the SE from Al Khaburah to Al Ghubrah. This could be attributed to either lower carbonate production or more sediment input by wadis along the north-western part of Al Batinah coast. The unique and complex nature of these sediments is largely due to the geology of the terrestrial source area in the Hajar Mountains which contains the famous Samail ophiolite complex and the weak sorting along the shoreline in these tide-modified beaches.     

Sedimentology and stratigraphy of a transgressive, muddy gravel beach: Waterside Beach, Bay of Fundy, Canada

Sediments exposed at low tide on the transgressive, hypertidal (>6 m tidal range) Waterside Beach, New Brunswick, Canada permit the scrutiny of sedimentary structures and textures that develop at water depths equivalent to the upper and lower shoreface. Waterside Beach sediments are grouped into eleven sedimentologically distinct deposits that represent three depositional environments: (1) sandy foreshore and shoreface; (2) tidal‐creek braid‐plain and delta; and, (3) wave‐formed gravel and sand bars, and associated deposits. The sandy foreshore and shoreface depositional environment encompasses the backshore; moderately dipping beachface; and a shallowly seaward‐dipping terrace of sandy middle and lower intertidal, and muddy sub‐tidal sediments. Intertidal sediments reworked and deposited by tidal creeks comprise the tidal‐creek braid plain and delta. Wave‐formed sand and gravel bars and associated deposits include: sediment sourced from low‐amplitude, unstable sand bars; gravel deposited from large (up to 5·5 m high, 800 m long), landward‐migrating gravel bars; and zones of mud deposition developed on the landward side of the gravel bars. The relationship between the gravel bars and mud deposits, and between mud‐laden sea water and beach gravels provides mechanisms for the deposition of mud beds, and muddy clast‐ and matrix‐supported conglomerates in ancient conglomeratic successions. Idealized sections are presented as analogues for ancient conglomerates deposited in transgressive systems. Where tidal creeks do not influence sedimentation on the beach, the preserved sequence consists of a gravel lag overlain by increasingly finer‐grained shoreface sediments. Conversely, where tidal creeks debouch onto the beach, erosion of the underlying salt marsh results in deposition of a thicker, more complex beach succession. The thickness of this package is controlled by tidal range, sedimentation rate, and rate of transgression. The tidal‐creek influenced succession comprises repeated sequences of: a thin mud bed overlain by muddy conglomerate, sandy conglomerate, a coarse lag, and capped by trough cross‐bedded sand and gravel.     

Analysis of sedimentary processes on the Las Canteras beach (Las Palmas, Spain) for its planning and management

The sedimentary dynamics of a sandy beach located on the North coast of the Island of Gran Canaria has been studied in relation to physical processes.

The morphodynamic behaviour of the beach has been established and interpreted. Special emphasis has been placed on the characterization of erosive and accretionary processes by means of sediment transport calculations. Two sedimentary indices have been used to define these processes qualitatively and quantitatively. These indices are of importance for management.     

Evaluation of criteria for predicting erosion and accretion on an estuarine sand beach, Delaware Bay, Jew Jersey

Predicting erosion and accretion of sand beaches in estuaries is important to managing shoreline development and identifying potential relationships between biological productivity and beach change. Wave, sediment and profile data, gathered over twenty-nine days on an estuarine sand beach in Delaware Bay, New Jersey, were used to evaluate the performance of four criteria that predict beach erosion and accretion due to wave-induced cross-shore sediment movement (Dean 1973; Sunamura and Horikawa 1974; Hattori and Kawamata 1980; Kraus et al. 1991). Each criterion defines a relation, between a wave and sediment parameter, and includes a coefficient that discriminates beach erosion and accretion events. Relations, based on small-scale laboratory and field data, were evaluated for predicting erosion or accretion at the study site. Significant wave heights at the study site, monitored near high water, ranged from 0.08 to 0.52 m with periods of 2.4 to 12.8 s. Median grain sizes of sediments on the beach foreshore, gathered at low water, ranged from 0.33 to 0.73 mm. All four criteria showed a clustering of erosion and accretion events. Relations derived from small-scale laboratory data were better predictors of erosion on the profile at the field site than those derived from field data gathered on exposed ocean environments. The planar profile and dominance of incident waves of low height and short period are similar to laboratory conditions characterized by initial planar beach slopes and monochromatic waves. Decreasing the value of the empirical coefficient to account for the differences in the magnitude of wave energy and grain size increases the performance of the criteria tested to predict erosion of the profile.     

Coarse‐sand beach ridges at Cowley Beach,north‐eastern Australia: Their formative processes and potential as records of tropical cyclone history

Storm surges generated by tropical cyclones have been considered a primary process for building coarse‐sand beach ridges along the north‐eastern Queensland coast, Australia. This interpretation has led to the development of palaeotempestology based on the beach ridges. To better identify the sedimentary processes responsible for these ridges, a high‐resolution chronostratigraphic analysis of a series of ridges was carried out at Cowley Beach, Queensland, a meso‐tidal beach system with a >3 m tide range. Optically stimulated luminescence ages indicate that 10 ridges accreted seaward over the last 2500 to 2700 years. The ridge crests sit +3·5 to 5·1 m above Australian Height Datum (ca mean sea‐level). A ground‐penetrating radar profile shows two distinct radar facies, both of which are dissected by truncation surfaces. Hummocky structures in the upper facies indicate that the nucleus of the beach ridge forms as a berm at +2·5 m Australian Height Datum, equivalent to the fair‐weather swash limit during high tide. The lower facies comprises a sequence of seaward‐dipping reflections. Beach progradation thus occurs via fair‐weather‐wave accretion of sand, with erosion by storm waves resulting in a sporadic sedimentary record. The ridge deposits above the fair‐weather swash limit are primarily composed of coarse and medium sands with pumice gravels and are largely emplaced during surge events. Inundation of the ridges is more likely to occur in relation to a cyclone passing during high tide. The ridges may also include an aeolian component as cyclonic winds can transport beach sand inland, especially during low tide, and some layers above +2·5 m Australian Height Datum are finer than aeolian ripples found on the backshore. Coarse‐sand ridges at Cowley Beach are thus products of fair‐weather swash and cyclone inundation modulated by tides. Knowledge of this composite depositional process can better inform the development of robust palaeoenvironmental reconstructions from the ridges.