Beach nourishment provides an excellent opportunity for the study of intensified sediment transport gradients and associated morphological changes in a natural setting. The objectives of this study are to quantify and predict longshore and cross-shore transport gradients induced by 1) beach nourishment, 2) different storm wave conditions, and 3) the annual wave climate and long-term sediment supply. The details of sediment transport rates and gradients induced by gradual processes and high-energy events are analyzed on a macro-scale. Well-planned monitoring of the 2004 Upham Beach nourishment project in west-central Florida collected high-spatial and -temporal resolution field data. Three hurricanes passed by the project soon after nourishment was complete.Post-nourishment planform adjustment occurs immediately after nourishment via diffusion spit development at the end transitions. Thus, the initiation of planform adjustment may be abrupt, rather than gradual as pred icted by the typical diffusion models. Diffusion spit formation is dominant during relatively calm wave conditions on coasts with low wave heights and tidal ranges.Profile equilibration also may be an event-driven, rather than a gradual, process. Rapid profile equilibration following nourishment occurred not only due to hurricane passage, but also during a winter season. The duration between nourishment and the passage of the first high-energy event is an important factor controlling the time scale of profile equilibration.The passage of three hurricanes generated different wave conditions and induced different sediment transport directions, rates, and gradients due to their variable proximities to the project area. The direction of cross-shore transport was governed by wave steepness. Onshore sediment transport occurred during a storm event, in contrast with the concepts of gradual onshore transport during mild wave conditions and abrupt offshore transport during storm events, as cited in the literature.By formulating sediment budgets on various temporal and spatial scales, both event-driven and average transport rates and gradients can be resolved. Annual average transport rates for a region should not be arbitrarily applied to nourished beaches; rather, sediment budgets formulated with high-spatial and -temporal resolution field data should be formulated during the design phase of future nourishment projects.

Beaches and coastal environments are dynamic, constantly shaped and reshaped by natural processes and anthropogenic modifications. The morphodynamics and influence of natural and anthropogenic factors of two different coasts at various temporal and spatial scales are discussed. To quantify the performance of several beach nourishment projects at annual temporal and kilometer spatial scales on three adjacent microtidal low-wave energy barrier islands in west-central Florida, a total of 5,200 beach and nearshore-profiles spaced at 300 m were surveyed monthly to bi-monthly from 2006-2010. Beach nourishment performance is most significantly influenced by the interruption of longshore sediment transport by complex tidal-inlet processes. More specifically, the tidal-inlet processes influencing adjacent beach nourishment performance includes longshore transport interruption resulting from divergence induced by wave refraction over an ebb-tidal shoal, flood-tidal currents along the beach, and total littoral blockage by structured inlets. A morphologic indicator of a large longshore transport gradient within the study area is the absence of a nearshore sandbar. These non-barred beaches are characterized by persistent shoreline erosion and were almost exclusively located in areas with a large longshore transport gradient. The more typical beach state along the three barrier islands was one exhibiting a migratory bar and relatively stable shoreline. The presence of a sandbar indicates the dominance of cross-shore processes, with onshore migration during calm wave conditions and offshore migration during energetic wave conditions. The onshore and offshore migration of the sandbar is closely related to non-stormy summer and stormy winter seasonal beach changes, respectively. The morphodynamics of a mixed sand and gravel beach in Delaware were investigated based on 740 beach profiles surveyed almost monthly from 2009 to 2011, 60 sediment cores, and 550 surface sediment samples collected at various alongshore and cross-shore transects. Inter-seasonal temporal scales of storm-induced beach changes and post-storm recovery were examined based on a hurricane, a typical energetic winter storm, and an extremely energetic storm resulting from the rare collision of a hurricane and winter storm ("Nor'Ida") occurring within a 3-month period in 2009. The mixed sand and gravel beaches in Delaware are characterized by monotonically increasing water depths lacking a sandbar under all wave conditions. A distinctive beach cycle was identified consisting of a built-up berm profile and depleted nearly-planar storm profile, with a time-scale related to the frequency and intensity of storm impact and duration of intra-storm recovery instead of simple seasonality. The sedimentological characteristics of the storm deposit associated with Nor'Ida demonstrated substantial cross-shore variation ranging from sandy-gravel and gravelly-sand within the storm swash zone (near the pre-storm dune edge) to well-sorted medium to coarse sand seaward of the storm swash zone, suggesting that storm deposits along mixed beaches demonstrate a variety of sedimentological characteristics. A new dynamic beach cycle model is proposed for the non-barred mixed sand and gravel beach with temporal variability controlled by storm occurrence and inter-storm duration.

A dinâmica de praia constitui conhecimento elementar em obras de engenharia e na compreensão da evolução costeira ao longo do Quaternário recente. Buscou-se avaliar a variação temporal de curto período da morfologia e do volume de sedimento em um segmento na porção sul da praia da Ilha Comprida, litoral sul de São Paulo. Os resultados permitiram algumas interpretações, tanto em escala diária, como sazonal. As morfologias e os volumes do trecho estudado apresentaram maior similaridade entre as campanhas de maio de 2005 e janeiro de 2006, com estágio morfodinâmico de praia dissipativa, e entre agosto e novembro de 2005, com estágio de praia intermediária do tipo banco e calha. As ondas de sul com alturas de até 1 m e período médio entre 7 e 8 s atuaram no processo de engordamento da praia emersa, enquanto que as ondas desta mesma direção com alturas a partir de 1,5 m e período médio entre 8 e 10 s exerceram papel erosivo. De forma inversa, as ondas de leste com até 1 m de altura e período médio entre 6 e 8 s exerceram papel erosivo e com até 1,5 m e período médio entre 6 e 7 s, papel deposicional. / The knowledge of beach dynamics is fundamental in any coastal engineering projects as well as in the coastal evolution comprehension during the Late Quaternary. The aim of this study is to evaluate the short-term variations in morphology and sediment volume in a beach segment located in the southern portion of the Ilha Comprida, southern coast of the state of São Paulo, Brazil. The results allowed us to get important conclusions on daily and seasonal variations in beach morphology and behaviour. The morphology and volume data show similarity between may/2005 and jan/2006, with dissipative morphodynamic state characteristics, as well as between aug/2005 and nov/2005, characterized by an intermediate morphodynamic state. Southerly waves reaching 1m high and mean period between 7 and 8 s acts on the emerged part of the segment in a depositional way as well as southerly waves higher than 1,5 m and period between 8 and 10 s cause erosion in the same part of the beach profile. Easterly waves act in an opposite way, with lower heights causing erosion and higher causing deposition.

Cross-shore bathymetric evolution in the nearshore zone often leads to threatening consequences such as beach erosion and shoreline retreat that concern the coastal community. A new, comprehensive cross-shore morphodynamic model was developed that can be used to describe and predict these phenomena. The study included both physical and numerical models that were designed to focus on the influence of sediment size characteristics on the cross-shore sediment transport process. For a profile equilibrium timescale, three types of beach profiles with different sediment mixtures were simulated in a small-scale, random-wave flume laboratory using erosive, storm, and accretive wave conditions. Dynamic relationships between the sediment grain sorting and beach profile changes were found to be evident as size-graded sediment fractions tended to relocate to different energetic zones along the cross-shore profiles. Existing phase-averaged wave and circulation models were utilized together with several new intra-wave modules for predicting important hydrodynamic parameters that were validated using the experimental data. A novel, multi-size sediment transport model was formulated to compute individual transport rates of size-graded sediment fractions while accounting for their interaction and non-linear size dependencies. The model was coupled with a new grain sorting model that resolves cross-shore grain sorting and vertical grain lamination. Compared to a traditional modeling approach, the new comprehensive model proved to offer superior modeling accuracy for both profile evolution and sediment grain size change. The use of the model is most advantageous for a condition with intensive grain sorting, a common scenario on a natural beach profile. Equilibrium beach profile is also better simulated by the model as size-graded fractions are predicted to relocate to different zones where they could withstand local hydrodynamics. Other new components that also help improve the modeling capability include the terms for wave-breaking and bed-slope effects, wave-crest sediment flux, and acceleration-induced bottom-shear stress. Besides superior profile modeling accuracy, sediment size characteristics and their spatial and temporal variations are also a useful set of information provided by the new model.

A seasonal and long-term analysis of the vertical structure of currents in the nearshore is conducted to determine the role of the wind in driving currents and consequently affecting littoral transport processes. Approximately ten years (January, 2002 – October, 2011) of nearshore current profiles are examined using the data collected with an Acoustic Doppler Current Profiler (ADCP) installed off of Spessard Holland North Beach Park located in Melbourne Beach, Florida. Additionally, wind data collected with a directional anemometer from September, 2002, until October, 2008, are used to further characterize the long-term hydrodynamic forcing. With the shoreline oriented nominally 17o west of magnetic north, both the current profiles and the wind vectors have been rendered into longshore and cross-shore components. The water level record from a NOAA tide station located at the Trident Pier at nearby Port Canaveral is utilized in establishing the water depth and conditioning the data for statistical analysis. Monthly mean vertical profiles reveal that during the winter months the surface currents are usually toward the south, and toward the north in the summer. In spring and fall, they are mixed, demonstrating a clear seasonality in both direction and intensity of the longshore current. Subjecting the longshore and cross-shore current data to Empirical Orthogonal Function Analysis reveals that the first spatial Eigenfunction accounts for more than 98% of the variability in the vertical profile of the longshore current, and more than 86% of the variability in the profile of the cross-shore current. However, there is a rotation of the current to the right (clockwise) with the rotation angle increasing and the variance decreasing with depth below the surface. The spiral structure of the water column follows a surface Ekman veering, but for very shallow water. The upper layer of the current is almost aligned with the direction of the wind. Monthly correlations between 2-hour average time series of longshore current and 2-hour average time series of wind speed reveal the seasonal patterns of the wind and longshore current in which the upper layer of the water column is highly correlated with the longshore component of the wind speed for most of the year and slightly less correlated for the lower layer of the water column. Most importantly, on average, wave height (Hmo) is larger when the longshore current is heading to the south (Hmo=0.95 m) than when the current is going to the north (Hmo=0.73 m). Additionally, there is a stronger correlation between southerly directed currents and incident wave energy flux than northerly directed currents and wave energy flux. These results indicate that the net long-term north-to-south sediment transport known to characterize the region is heavily influenced by wind-driven currents.