Rozprawy doktorskie na temat „Beach nourishment”

This thesis investigated the effects of photographic and text information on respondents' attitudes and willingness-to-pay for a proposed beach protection scheme in the erosion prone Gold Coast region on the east coast of Australia. The research developed two alternative expectancy-value attitude-behaviour models to test residents' attitudes toward relevant targets and behavioural intention, expressed through stated willingness-to-pay, and compared the proposed models with one established attitude-behaviour model. The thesis set out to investigate three central research questions; one question relating to the effects of information on attitudes and willingness-to-pay, and two questions relating to the relationships between attitudes and willingness-to-pay. It was hypothesised that photographs that depicted severe erosion damage would result in more positive attitudes toward, and greater willingness-to-pay for, beach protection than photographs that showed only mild levels of erosion damage. Positive relationships were hypothesised between variables representing attitudes toward beach erosion, attitude toward beach protection, attitude toward paying for beach protection, and willingness-to-pay. Finally, it was hypothesised that the relationships between attitudes and willingness-to-pay could be adequately explained by the proposed attitude-behaviour models. The thesis describes how seven information treatments and eight attitude measurement scales were developed and tested in a pilot experiment before use in a survey of homeowners in the region of interest. Analysis of variance showed that, while respondent's attitude toward beach protection was affected by the information treatments, their willingness-to-pay for the proposed program was insensitive to information. There were no significant effects that could be attributed exclusively to text descriptions of the good but there were significant effects that could be attributed to photographic information treatments. However, none of the effects on attitudes resulted in significant effects on the behavioural intention expressed in stated willingness-to-pay. Analysis of respondents with low previous knowledge of the proposed good revealed more extensive information effects on attitudes, but still not on willingness-to-pay, and this suggests that high levels of previous knowledge in a large proportion of the sample had a moderating effect on attitude change caused by the information treatments. Regression analysis showed that seven of the eight attitude and behaviour variables in the proposed attitude-behaviour model were significant predictors of willingness-to-pay. In the final phase of the analysis, goodness-of-fit indices, estimated using Structural Equation Modelling, indicated a good fit between the data and the attitude-behaviour models tested. Standardised coefficients on the model indicated that perceived behavioural control, expected utility of outcomes, and subjective norms all had strong direct relationships with stated willingness-to-pay, and strong indirect relationships on willingness-to-pay via attitudes toward payment. These results are consistent with the relationships proposed in attitude-behaviour models and the moderating effects of these variables explain why significant information treatment effects were observed on attitude to beach protection but not on willingness-to-pay. This research showed that respondent's willingness-to-pay in a contingent valuation experiment is quite insensitive to photographic treatments when previous knowledge is high and that costly and time consuming testing procedures, recommended by authorities, may not be necessary under these conditions. It also demonstrated that measures of attitude, consistent with an attitude-behaviour model, can be collected easily in a contingent valuation study and can contribute to understanding of participant responses and to identification of protest responses.

This thesis investigated the effects of photographic and text information on respondents' attitudes and willingness-to-pay for a proposed beach protection scheme in the erosion prone Gold Coast region on the east coast of Australia. The research developed two alternative expectancy-value attitude-behaviour models to test residents' attitudes toward relevant targets and behavioural intention, expressed through stated willingness-to-pay, and compared the proposed models with one established attitude-behaviour model. The thesis set out to investigate three central research questions; one question relating to the effects of information on attitudes and willingness-to-pay, and two questions relating to the relationships between attitudes and willingness-to-pay. It was hypothesised that photographs that depicted severe erosion damage would result in more positive attitudes toward, and greater willingness-to-pay for, beach protection than photographs that showed only mild levels of erosion damage. Positive relationships were hypothesised between variables representing attitudes toward beach erosion, attitude toward beach protection, attitude toward paying for beach protection, and willingness-to-pay. Finally, it was hypothesised that the relationships between attitudes and willingness-to-pay could be adequately explained by the proposed attitude-behaviour models. The thesis describes how seven information treatments and eight attitude measurement scales were developed and tested in a pilot experiment before use in a survey of homeowners in the region of interest. Analysis of variance showed that, while respondent's attitude toward beach protection was affected by the information treatments, their willingness-to-pay for the proposed program was insensitive to information. There were no significant effects that could be attributed exclusively to text descriptions of the good but there were significant effects that could be attributed to photographic information treatments. However, none of the effects on attitudes resulted in significant effects on the behavioural intention expressed in stated willingness-to-pay. Analysis of respondents with low previous knowledge of the proposed good revealed more extensive information effects on attitudes, but still not on willingness-to-pay, and this suggests that high levels of previous knowledge in a large proportion of the sample had a moderating effect on attitude change caused by the information treatments. Regression analysis showed that seven of the eight attitude and behaviour variables in the proposed attitude-behaviour model were significant predictors of willingness-to-pay. In the final phase of the analysis, goodness-of-fit indices, estimated using Structural Equation Modelling, indicated a good fit between the data and the attitude-behaviour models tested. Standardised coefficients on the model indicated that perceived behavioural control, expected utility of outcomes, and subjective norms all had strong direct relationships with stated willingness-to-pay, and strong indirect relationships on willingness-to-pay via attitudes toward payment. These results are consistent with the relationships proposed in attitude-behaviour models and the moderating effects of these variables explain why significant information treatment effects were observed on attitude to beach protection but not on willingness-to-pay. This research showed that respondent's willingness-to-pay in a contingent valuation experiment is quite insensitive to photographic treatments when previous knowledge is high and that costly and time consuming testing procedures, recommended by authorities, may not be necessary under these conditions. It also demonstrated that measures of attitude, consistent with an attitude-behaviour model, can be collected easily in a contingent valuation study and can contribute to understanding of participant responses and to identification of protest responses.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Full Text

The health of Florida's beaches are vital to the survival of loggerhead sea turtles (Caretta caretta), as nearly half of the world's loggerheads nest on the states beaches. Many of the beaches utilized by the turtles have undergone nourishment projects in hopes of combating erosion of the shoreline, protecting beachfront property, and creating more suitable beaches for tourism. Although it is argued that beach nourishment benefits sea turtles by providing more nesting habitat, the effects of the Pinellas County nourishment projects on loggerhead nesting are unknown. Beach nourishment can alter the compaction, moisture content, and temperature of the sand, all of which are variables that can affect nest site selection and the proper development of eggs. This research has four objectives: (1) to create a GIS dataset using historic loggerhead sea turtle data collected at the individual nest level along the West coast of Florida, (2) to examine the densities of loggerhead nests, the densities of false crawls (i.e. unsuccessful nesting attempts), and the nest-to-false crawl ratio on natural and nourished beaches for the 2006-2010 nesting seasons; (3) to determine the effects of beach nourishment projects on the hatchling success rates and emergence success rates; and (4) to determine areas preferred or avoided by turtles for nesting. The study found that nesting and false crawl densities significantly differed between natural and nourished beaches during three of the five nesting seasons. Nesting densities increased directly following nourishment and false crawl densities were higher in nourishment areas during every nesting season. False crawl densities were higher than statistically expected on nourished beaches and lower than expected on natural beaches. No significant differences were found between hatchling and emergence success rates between natural and nourished beaches. However, when the rates were analyzed by nesting season, the average hatching and emergence success rates were always lower on nourished beaches than on natural beaches. A hotspot analysis on nests and false crawls revealed that turtles preferred natural beaches that border nourished areas for nesting while false crawls were more evenly distributed through the study area. Although this study documents the negative effects of beach nourishment on loggerhead sea turtle nesting, nourishment projects are likely to continue because of their benefits to human populations. Further examining of the impacts that humans have on nesting and developing loggerheads will ultimately aid policy formation as we continue to manage and protect the future of the species.

Inlets and channels are dredged often to maintain navigation safety. It is beneficial to reintroduce the dredged material back into the littoral system, in the form of beach or nearshore nourishments. Nourishment in the nearshore is becoming an increasingly utilized method, particularly for dredged material that contains more fine sediment than the native beach. This research examines the morphologic evolution of two different nearshore nourishments. A nearshore berm was constructed at Fort Myers Beach, Florida using mixed-sized sediment dredged from a nearby channel. The nearshore berm was placed in water depths between 1.2 and 2.4 m with the berm crest just below MLLW in the shape of a bar. The nearshore berm migrated onshore while the system was approaching a dynamic equilibrium. Near the end of the fourth year, the beach profiles had returned to the equilibrium shape characteristic of the study area. Gaps in the berm allowed water circulation and should be considered as a design parameter. The fine sediment fractions in the original placed material was selectively transported and deposited offshore, while the coarser component moved onshore. The dry beach maintained the same sediment properties throughout the study period and was not influenced by the fine sediment in the initial construction of the berm. Another nearshore nourishment was placed along eastern Perdido Key, Florida in 2011-2012 using maintenance dredged material from nearby Pensacola Pass. Different from the Fort Myers Beach berm, the material was placed within the swash-zone, with a maximum elevation of +0.91 m NAVD88 (or 0.62 m above MHHW). The low constructed berm elevation allowed natural overwash processes to occur frequently, which resulted in net onshore sediment transport and growth of the active beach berm. Sediment volume gain west of the project area due to longshore spreading of the nourishment occurred mostly in the trough between the shoreline and the bar, rather than on the dry beach. The swash-zone berm evolved back to the natural equilibrium profile shape maintained in the study area within 8 months. The performance of the swash-zone nourishment was compared to two previous beach nourishments at the same location in 1985 and 1989-1991, with higher berm elevations, at +3 m and +1.2 m NAVD88, respectively. The 1.2-km 1985 nourishment performed the poorest with a shoreline retreat rate of 40 m/year. The 7.3-km 1989-1991 nourishment performed the best with a retreat rate of 11 m/year. This suggests that high berm elevations do not necessarily lead to better nourishment performance. Longshore extent of a nourishment may play an essential role. The distant passage of two tropical storms (Tropical Storm Debby and Hurricane Isaac) generated high waves for the study areas. The two berm nourishments responded differently to the storm. Response was also compared to a beach nourishment in Sand Key. The bar-shaped Fort Myers Beach berm was split into two smaller bars, while a storm berm developed for the swash-zone nourishment at Perdido Key. In both cases, the energetic storm conditions accelerated the evolution of the berm profiles toward equilibrium. As compared to the measured nearshore waves by this study, CMS-Wave accurately propagated the WIS Hindcast waves. SBEACH accurately captured the maximum water elevation, consistent with measured upper limit of morphology change. The model correctly predicted beach and nearshore erosion during the storms. The growth of the storm berm at the Perdido Key swash-zone nourishment was predicted reasonably well by the SBEACH model. However, the magnitudes of the storm-induced erosion and the locations of the offshore bar were not accurately predicted consistently.

The heavily developed Long Key is located in Pinellas County in west-central Florida. The structured Blind Pass at the north end of the barrier island interrupts the southward longshore sediment transport, resulting in severe and chronic beach erosion along the northern portion of the island. Frequent beach nourishments were conducted to mitigate the erosion. In this study, the performance of the most recent beach nourishment in 2010 is quantified through time-series beach profile surveys. Over the 34-month period, the nourished northern portion of the island, Upham Beach, lost up to 330 m3/m of sand, with a landward shoreline retreat of up to 100 m. The middle portion of the island gained up to 25 m3/m of sand, benefiting from the sand lost from Upham Beach. The southern portion of Long Key lost a modest amount of sediment, largely due to Tropical Storm Debby, which approached from the south in June 2012. The severe erosion along Upham Beach is induced by a large negative longshore transport gradient. The beach here has no sand bar and retreated landward persistently over the 34-month study period. In contrast the profiles in the central section of the island generally have a sand bar which moved landward and seaward in response to seasonal and storm-induced wave-energy changes. The sand volume across the entire profile in the central portion of the island is mostly conserved. Two typical example beach profiles, LK3A and R157, were selected to examine the ability of the commonly used principal component analysis (PCA), also commonly known as empirical orthogonal function analysis (EOF), to identify beach profile ix changes induced by longshore and cross-shore sediment transport gradients. For the longshore-transport driven changes at the non-barred profile LK3A, the principal eigenvector accounted for over 91% of the total variance, with a dominant broad peak in the cross-shore distribution. At the barred R157, the profile changes were caused mainly by cross-shore transport gradients with modest contribution from longshore transport gradient; eigenvalue one only accounted for less than 51% of the total variance, and eigenvalues two and three still contributed considerably to the overall variance. In order to verify the uniqueness of the PCA results from LK3A and R157, five numerical experiments were conducted, simulating changes at a barred and non-barred beach driven by longshore, cross-shore, and combined sediment transport gradients. Results from LK3A and R157 compare well with simulated beach erosion (or accretion) due to variable longshore sediment transport gradients and due to both cross-shore and longshore sediment transport gradients, respectively. Different PCA results were obtained from different profile change patterns.

To combat the rapid degradation of the Louisiana coast, the Louisiana Coastal Protection and Restoration Authority has planned strategic land building initiatives throughout the Louisiana Gulf coast, including beach nourishment and marsh creation projects. It is commonly agreed that the state lacks sufficient renewable sediment resources to maintain the planned CPRA land building program. However, Louisiana, the state that commonly ranks last in state recycling percentage, recycles an estimated 0.6% of the waste glass consumed in the state. Glass is predominantly silica sand. This thesis evaluates laboratory‑determined characteristics of recycled crushed glass cullet to assess its suitability as a renewable aggregate for beach nourishment and marsh creation projects. Specifically, the research herein evaluates geotechnical and settling characteristics of recycled crushed glass cullet produced in Pearl River, Louisiana. Additionally, this research evaluates the effects on beach nourishment and marsh creation design parameters of blending this material with Gulf coastal sediments.

O mapeamento da Plataforma Continental Interna visando localização, qualificação e quantificação das reservas de material litoclásticos marinho possui poucos trabalhos relacionados. O Estado de Pernambuco sofre com erosões ao longo de todo seu litoral, e principalmente junto às cidades de Recife e Olinda. Assim, este estudo contribui tanto para o conhecimento da sedimentologia da plataforma continental interna adjacente ao Porto do Recife e à Praia dos Milagres em Olinda, quanto para a execução de futuras intervenções na recuperação das praias da região. Portanto, com objetivo de identificar áreas com concentrações de granulados litoclásticos marinhos compatíveis com especificações necessárias à regeneração de praias, foram analisadas 36 amostras, que foram coletadas ao longo de seis perfis equidistantes em 1 km, perpendiculares à linha de costa na plataforma interna do Porto do Recife. Em laboratório foram realizadas análises granulométricas e o estudo composicional de todas as amostras. Os resultados granulométricos mostram a predominância de sedimentos mal selecionados, ocorrendo classes variadas de tamanho entre seixo pequeno (8 mm) e lama (< que 0,062 mm), com predominância da fração areia grossa. A análise composicional revelou uma hegemonia de carbonatos marinhos. Os dados obtidos apresentam uma redução do suprimento sedimentar terrígeno local. Também de acordo com os resultados obtidos no presente estudo, a plataforma continental interna adjacente ao Porto do Recife e à praia dos Milagres em Olinda-PE, é essencialmente recoberta por areias biogênicas mal selecionadas, oriundas da morte e fragmentação dos organismos componentes dos recifes coralíneos e algálicos que ocorrem na plataforma continental interna. Dessa forma, esta área não possui material siliciclástico suficiente para ser utilizado na exploração mineral para recuperação artificial de praias no Estado de Pernambuco.
There are few studies that map the Internal Continental Platform referring to localization, qualification and quantification of reserves of litoclastic marine material. The Brazilian state Pernambuco suffers from erosions along the whole coast and particularly in areas close to the cities of Recife and Olinda. This study offers new knowledge about the sedimentology of the internal continental platform adjacent to the harbor of Recife and the Beach Milagres in Olinda. Furthermore, it points out measures that can be used to recover regional beaches. Along 6 profiles with a distance of 1km and perpendicular to the coast line at the internal platform of the harbor of Recife, 36 samples were collected and analyzed. Thus, areas with concentrations of litoclastic marine aggregates with the necessary characteristics for the recovery of the beaches were identified. A laboratory was used for granulometry and a compositional study of all samples. The granulometric results show mainly badly selected sediments. There are different sizes from small pebbles (8 mm) to mud (< than 0,062 mm), predominantly coarse sand fraction. The compositional analysis reveals hegemony of marine carbonates. Thus the obtained data indicates a reduction of local terrigenous sedimentary supply. This is probably due to the fact that the selected area is undergoing an initial transgressive process. Also in accordance with the obtained results of this study, the internal continental platform adjacent to the harbor of Recife and the Beach Milagres in Olinda, Pernambuco, is mainly covered by badly selected biogenic sand which has its origin in the death and fragmentation of components of the coral reef of the internal continental platform. As a result the area is not indicated to mineral exploration for the artificial recovery of the beaches in the state of Pernambuco.

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.

Broward County, Florida is a popular tourism destination. Due to its popularity, much of the shoreline has been modified and natural habitats were replaced with infrastructure such as houses, condominiums, resorts, and restaurants. The same Broward County beaches utilized by tourists and residents are important for three species of nesting sea turtles, including the Leatherback, Dermochelys coriacea, Loggerhead, Caretta caretta, and Green, Chelonia mydas, Turtles. The Broward County Sea Turtle Conservation Program (BCSTCP) collects yearly data in order to study these endangered reptiles. Increased anthropogenic effects including further coastal development (public & private), public beach events, public beach access, as well as natural events, have caused these important nesting beaches to erode and narrow. In an effort to control this erosion damage, Broward County has performed a number of beach nourishment projects. This study found yearly fluctuations in sea turtle hatching and emergence success rates, and years of beach nourishment projects significantly decreased these rates. Yearly hatching data available from Broward County concludes that beach nourishment, as well as hurricanes and tropical storms cause decreases in sea turtle hatching and emergence success rates in Broward County. Additionally, nest depth and sea turtle size increases the hatching and emergence success rates from females that are not too large or too small that nest in Broward County.

This dissertation studies three aspects of the economics of climate change: how rising sea levels will affect coastal homeowners in Florida; how changes in weather will affect the prevalence of crime in the United States; and why skepticism about climate change is so common among the general public. Chapter 1 uses housing market data to estimate the welfare costs of shoreline loss along coastal beaches in Florida. I develop a structural housing market model and use it to provide a welfare interpretation for the coefficients from a new “discontinuity matching” hedonic research design. Using housing sales data, beach width surveys, and historical beach nourishment records, I then estimate Florida homeowners’ willingness to pay for an extra foot of sand. I find that changes in beach width have little impact on housing prices, except possibly at very eroded beaches. Chapter 2 estimates the impact of climate change on the prevalence of criminal activity in the United States. The analysis is based on monthly crime and weather data for 2,972 U.S. counties from 1960 to 2009. The results show that temperature has a strong positive effect on criminal behavior, and that between 2010 and 2099, climate change will cause an additional 35,000 murders, 216,000 cases of rape, 1.6 million aggravated assaults, 2.4 million simple assaults, 409,000 robberies, 3.1 million burglaries, 3.8 million cases of larceny, and 1.4 million cases of vehicle theft. The social cost of these climate-related crimes is between 20 and 68 billion dollars. Chapter 3 develops a model of rational skepticism about policy-relevant scientific questions. Many policy debates have three features: first, individuals initially disagree about some scientific question; second, new evidence about the question becomes available; and third, the evidence may be systematically biased. Under these conditions, Bayesian disagreements persist even in the face of an infinite quantity of new evidence. Furthermore, Bayesian updating based on the new evidence produces “skeptics”, in the sense that individuals whose prior beliefs conflict most with the observable evidence end up with the most extreme posterior beliefs about the degree of bias. These results provide insight into the phenomenon of climate skepticism.

Dredging is often conducted to maintain authorized depths in coastal navigation channels. Placement of dredged sediment in the form of nearshore berms is becoming an increasingly popular option for disposal. Compared to direct beach placement, nearshore berms have fewer environmental impacts such as shore birds and turtle nesting, and have more lenient sediment compatibility restrictions. Understanding the potential morphological and sedimentological evolution is crucial to the design of a nearshore berm. Furthermore, the artificial perturbation generated by the berm installation provides a unique opportunity to understand the equilibrium process of coastal morphodynamics. Matanzas Pass and Bowditch Point, located on the northern tip of Estero Island in west-central Florida were dredged in October 2009. The dredged material was placed approximately 600 ft offshore of Fort Myers Beach and 1.5 miles southeast of Matanzas Pass, in the form of an artificial berm. Time-series surveys and sediment sampling were conducted semi-annually in order to quantify sedimentological characteristics and morphological changes within the first year after construction of the berm. The artificial berm at Fort Myers Beach is composed mainly of fine sand. Patches of mud were found throughout the study area, with the highest concentrations being in the trough landward of the berm, and offshore southeast of the berm area. The highest concentration of carbonates was found in the swash zone, as well as at the landward toe of the berm, which coincides with the coarsest sediment. The overall mud content of the berm is lower than that of the dredged sediment, thus indicating a coarsening of the berm over time. The reduction in fines as compared to the original dredged sedimet could also indicate a selective transport mechanism that moves finer material offshore, and coarser material landward, a desirable trend for artificial berm nourishment. During the course of the first year, the berm migrated landward and increased in elevation. Onshore migration occurred mostly within the first 6 months. Along with onshore migration, the shape of the berm changed from a symmetrical bell curve to an asymmetrical shape with a steep landward slope. There is no clear spatial trend of volume change alongshore within the berm area, indicating that sediment transport is mostly cross-shore dominated. A salient was formed landward of the northern portion of the berm. Several gaps were created during berm construction due to dredging and placement techniques. These dynamic gaps are likely maintained by rip currents through them. This study showed that the Fort Myers Beach berm is active, due to its landward migration during the first year after construction.

Marine turtle reproductive success is strongly correlated with the stability and quality of the nesting environment. Because females show fidelity to key nesting beaches, the management and physical characteristics of these beaches directly affect future generations of marine turtles and may be essential for the recovery of these threatened and endangered species. The impacts of beach restoration on loggerhead turtles (Caretta caretta) and on green turtles (Chelonia mydas) were investigated. Previous studies concerning beach nourishment projects have focused on loggerhead turtles. I compared data between nourished and non-nourished areas and between loggerhead and green turtles. I found, at one season post-nourishment, negative effects on nesting success and no significant effect on reproductive success for both loggerheads and established the same relationships with green turtles. Physical attributes of the fill sand, which did not facilitate acute scarp formation or severe compaction, did not physically impede turtles in their attempts to nest. Instead, the decrease in nesting success was attributed to an absence of abiotic and or biotic factors that cue nesting behavior. The increase in loggerhead nesting success rates during the second season post-nourishment was attributed to the equilibration process of the seaward crest of the berm. After the beach was restored, both species of turtles placed nests significantly farther from the water in the nourished area than in the non-nourished area. Green turtles nested on or near the dune and loggerheads nested on the seaward crest of the berm. The tendency of loggerheads to nest closer to the water resulted in more loggerhead than green turtle nests being "washed out" by erosion during the equilibration process. There was a significant increase in hatching success only for loggerheads when wash outs were excluded, thus illustrating the importance of nest placement and the detrimental effects of the equilibration process to the reproductive success of loggerheads. A decrease in reproductive output occurred during the first season post-nourishment. The reduction in the estimated total number of hatchlings produced (reproductive output) was a consequence of decreased nesting success lowering nest numbers. This reduction demonstrates that, regardless of similar reproductive success rates, marine turtles incurred net losses during the first season following nourishment. These results further reveal the impacts of decreased nesting success and the importance of minimizing excessive non-nesting emergences associated with beach nourishment.
M.S.
Department of Biology
Arts and Sciences
Biology

A faixa urbanizada da orla na costa sul – oriental e leste do Estado do Rio de Janeiro sofre constantemente com a destruição de calçadões, ruas, muros e casas em eventos oceanográficos extremos. Essas construções, na maior parte dos casos estão localizadas muito próximas ao limite com a praia, dentro da faixa de não edificação prevista no Projeto Orla do Ministério do Meio Ambiente. A região apresenta forte crescimento populacional com principais atividades econômicas associadas à exploração de petróleo nas cidades de Macaé e Rio das Ostras, ao turismo da Região dos Lagos, além do centro urbano de Niterói já consolidado. A identificação de jazidas de material semelhante ao original para recuperação de praias como opção de mitigação, representa uma alternativa para manter a função de proteção exercida pelas mesmas e de seu uso para o lazer. Nesse sentido, este estudo tem como objetivo analisar a compatibilidade de sedimentos superficiais da plataforma continental interna com as areias de praias urbanas, situadas entre as cidades de Niterói e Macaé – RJ, através da comparação de parâmetros estatísticos da distribuição granulométrica das areias desses dois ambientes. Para a caracterização sedimentar das praias alvo, foram coletadas amostras da face praial de 16 praias situadas nos principais núcleos urbanos deste segmento do litoral fluminense. Os dados granulométricos dos sedimentos superficiais da antepraia e plataforma continental interna entre Niterói e Macaé são secundários, de campanhas oceanográficas pretéritas. Tais dados foram filtrados e digitalizados, somando um total de aproximadamente 1200 pontos de coleta que vão desde a barra leste da Baia da Guanabara até a Restinga de Jurubatiba. Onze áreas granulometricamente compatível com as diferentes praias da região de estudo foram identificadas próximo à isóbata de -20 m ao largo da costa de Niterói e Maricá, de Cabo Frio e Búzios e entre Rio das Ostras e Macaé, representando potenciais estoques de sedimento para utilização em projetos de recuperação dessas praias.
The urbanized coastline of east and south-east littoral of the state of Rio de Janeiro suffers constantly with the destruction of houses, walls and streets in extreme oceanographic events. These constructions, in most cases are located very close to the limit with the beach, inside of the range of no building suggest by Projeto Orla – Ministry of Environment. This region has strong population growth with major economic activities associated with oil exploration in the city of Macae and Rio das Ostras, industry of tourism in Lakes Region and the urban center of Niteroi already consolidated. The identification of sand deposits with similar granulometric characteristics to the native material to nourishment project as a mitigation option, represented an alternative to maintain the protective function of the beach and use for recreation. The objective of this study is analyze the compatibility of surface sediments of the inner continental shelf and sands of urban beaches, located between the cities of Niteroi and Macae – RJ, through of comparison the statistical parameters of size distribution of the sands of these two environments. For the characterization of sedimentary beaches were sampled from the beach face of 16 beaches located in the major urban centers of this segment of the coastline of Rio de Janeiro’s state. The granulometric data of surface sediments of the inner continental shelf between Niteroi an Macae are secondary from preterits oceanographic campaigns. These datas were filtered and digitized with a total of approximately 1200 collection points ranging from east bar of Guanabara Bay to the Restinga de Jurubatiba. Eleven areas granulometrically compatible with the different beaches were identified near the -20 meters isobaths near the coast of Niteroi and Marica, Cabo Frio and Buzios and between Rio das Ostras and Macae, representing a potential borrow areas for use in nourishment projects in this region.

Artificial beach nourishment, the most common method to mitigate coastal erosion in the United States, is also considered the most ecologically friendly alternative for shoreline stabilization. However, this habitat alteration has the potential to impact nesting marine turtles and developing hatchlings. The first objective of this study was to determine how nourishing beaches with two different design templates affects loggerhead (Caretta caretta) and green turtle (Chelonia mydas) nesting success, the ratio of nests to the total number of nests and non-nesting emergences, and reproductive success, the ratio of hatched and emerged hatchlings to the total number of eggs deposited. Two types of restoration designs exist along the southern Brevard County, FL coastline, which supports some of the highest density loggerhead and green turtle nesting worldwide. Since 2005, approximately 35 kilometers of beach have undergone 1) full-scale restoration (typically called nourishment), where sand was added above and below the mean high tide line (2005, 2010) or 2) dune restoration, where sand was placed on the dune (2005, 2006, 2008, 2009). To quantify the effects of these restoration types, we used a Before-After-Control-Impact-Paired Series (BACIPS) model, which tests for significance between the difference in nesting success rates at the impact (engineered) and control sites (natural beach) before and after restoration ([delta]). For loggerheads, there was a significant difference in [delta] after dune restoration during the years of construction (2005, 2006, 2008, and 2009; p<0.001) and one year post-construction (2007; p<0.05 and 2010; p<0.001). After full-scale restoration, there was a significant difference in [delta] during the years of construction (2005 and 2010; p <0.001) and one year post-construction (2006; p<0.001). For green turtles, there was a significant difference in [delta] after dune restoration during two of the four years of construction (2006; p<0.05 and 2008; p<0.01) and one of the two one-year post-construction years (2010; p<0.05). After full-scale restoration, the significant difference in [delta] lasted every season (2005-2010; p<0.001). There were no significant differences in [delta] for loggerhead or green turtle reproductive success rates after either type of restoration. The second objective was to use the different restoration designs to study what beach characteristics function as loggerhead nesting cues to explain why altering the beach decreases nesting success rates. We examined beach elevation and slope, sand moisture content, sand grain size, beach width, and distance traveled. Logistic regression model selection found all variables were important (R2=0.75). Further examination of trends, with each crawl divided into quarters, found beach slope served as a nesting cue. In all study sites except one, when turtles false crawled, the beach flattened out in the final quarter of the crawl. Conversely, in nesting emergences, the final quarter rose at a steeper slope than the previous quarter. Additionally, model selection found variables important in nest site selection were also important in hatching (R2=0.44) and emergence (R2=0.45) success. These results offer new insight into how and why marine turtle nesting patterns change after artificial nourishment, providing information necessary to nourish beaches in a more “turtle-friendly” manner.
ID: 031001543; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: John Weishampel.; Co-adviser: Llewellyn Ehrhart.; Title from PDF title page (viewed August 22, 2013).; Thesis (M.S.)--University of Central Florida, 2012.; Includes bibliographical references (p. 84-90).
M.S.
Masters
Biology
Sciences
Biology

L’objectif de cette thèse est la détermination des causes du phénomène d'érosion marine, et la production de propositions d'orientation pour la protection de la plage de l’Almanarre. L'étude commence par la collecte et l'analyse de toutes les données disponibles, pour trouver des règles d’évolution du tombolo de Giens. Puis, le logiciel de modélisation MIKE a été appliqué pour confirmer l'hypothèse et à obtenir une meilleure connaissance de la dynamique à l’œuvre au tombolo Ouest. Ensuite, nous avons couplé des facteurs simultanément : les houles, les courants côtiers, et les transports des sédiments pour les différents régimes de houle et de vent dans MIKE 21. Enfin, la possibilité de stabiliser le tombolo Ouest est discutée pour donner des suggestions sur les choix de solutions adaptées
The objective of this thesis is the determination of the causes of sea erosion phenomenon, and the production of policy proposals for the protection of the beach. The study begins with the collection and analysis of all available data, to find evolution rules of tombolo of Giens. Which aims to explain how the hydrodynamic processes and sediment transport occur. Then MIKE modeling software was applied to confirm the hypothesis and get a better understanding of the dynamics at work in the Western tombolo. Then, we coupled factors simultaneously: waves, coastal currents and sediment transport for different regimes of wave and wind in MIKE 21. Finally, the possibility of stabilizing the Western tombolo is discussed to give suggestions on the choice of solutions

Grunts (Haemulidae: Percoidei) represent one of the most abundant and speciose families on western North Atlantic coral reefs including 15 diverse species from the genus Haemulon. For this dissertation focusing on Haemulon, three studies were conducted to examine 1) spatio-temporal distributions of early-life stage (newly settled and early juvenile) individuals throughout the southeast mainland Florida reefscape, 2) species-specific, depth-variable distributional patterns of newly settled individuals and the potential influence of predation on the observed patterns, and 3) the effects of burying nearshore hardbottom settlement habitat and the efficacy of mitigating for the lost habitat using limestone boulder reefs. The combined results of the studies suggest that newly settled Haemulon spp. utilize shallow reef habitats (highest densities on nearshore hardbottom) with peak abundances in summer months. While newly settled individuals were never observed on natural reef habitats below 12 m depth, studies using artificial reefs (ARs) showed that new settlers were commonly recorded at depths of 21 m. Species-specific patterns of new settler depth utilization were found when replicate ARs at three sites (8 m, 12 m, and 21 m depth) were examined. Of the three most abundant species collected during fortnightly sampling of ARs, newly settled H. flavolineatum and H. aurolineatum were found at all three sites while H. striatum was found almost exclusively at the 21-m site. Comparison of caged and noncaged ARs allowed for inferences to be made regarding depth-variable predation pressure on newly settled Haemulon spp. Results (based on delta density differences between caged and noncaged ARs at each site) suggest lower predation pressure at the 8-m site, relative to the 12-m and 21-m sites. Depth-variable predation pressure may, in part, explain the distributional patterns exhibited by newly settled Haemulon spp. on the natural reef. I examined annual change in early-stage Haemulon spp. populations on nearshore hardbottom (NHB) to assess the impact of habitat burial caused by a large-scale beach nourishment. Newly settled Haemulon spp. represented the most abundant fish taxa on NHB. Populations of this life-history stage exhibited high variability among annual surveys and no direct effect of NHB burial was detected. In contrast, early juvenile individuals showed a significant decline during the annual survey corresponding with the timing of the beach construction (burial of NHB habitat). Furthermore, the beach-nourishment activities altered the entire fish assemblage structure of the NHB adjacent to the beach fill area. This change in the NHB fish assemblage structure had not returned to pre-impact conditions three years after the conclusion of the nourishment. Limestone boulder reefs deployed to mitigate for buried habitat exhibited lower newly settled Haemulon spp. abundance than NHB. Contrastingly, early juvenile abundance was higher on the boulder reefs than on the NHB. Fish assemblage structure on the boulder reefs differed substantially from the NHB for which it was intended to resemble; with more mid- and large-bodied predators present on the boulder reefs. The results suggest mitigation boulder reefs did not provide equitable settlement habitat for Haemulon spp. Based on the combined results of this dissertation, it appears that shallow reef habitats (especially NHB) represent important settlement habitat for Haemulon spp. by providing spatial refuge from predators, which were more prevalent at deeper sites. Although burial did not appear to directly cause changes to newly settled Haemulon spp. populations on the NHB, fish assemblage structure was altered. Changes in species composition and abundance can have unforeseen ecological consequences for future Haemulon spp. populations. Relative to other reef habitats, the high densities of new settlers supported by the NHB suggests this unique habitat deserves protection from future nthropogenic impacts.

碩士
國立成功大學
水利及海洋工程學系專班
91
This study is intended to probe the behaviour of sand dispersion in beach nourishment; the results may be useful for design and construction of marine works. A composite model of tidal current and concentration dispersion is employed to simulate beach nourishment with various placing locations, quantities, times and particle diameters of sand. To point placing case, the study outlines that the sand concentratuon is dispersed forward to offshore becoming stable after 24 hours of continue dumping, but varied with the distance and the difference of ebb or flood current. Nevertheless, the dispersion continues to growth along the long shore direction. If the sand placing quantity was designed to be a constant value, the instant placing disperses to far area than continuous placing. 　　While the sand is dumped in the near-shore area between breakwaters of An-ping Fishing Port and An-ping Commercial Port, the sand concentration could affect wider areas when the placing location gets farther away from the coastal line. Secondly, the closer to the shore the placing location is, the faster the dispersion occurs after sand placing is stopped, and the high sand concentration is bonded within these two breakwaters and will not pass through the southern breakwater line of An-ping Commercial Port even in flood. However, if sand is placed near the outside of southern breakwater of An-ping Commercial Port, wider areas of dispersion would appear and sand concentration would disperse offshore because of the sheltering of the breakwater. Moreover, when the sand placing location gets farther away from the southern breakwater, sand concentration disperses more widely along the long shore direction, but the variation in the cross direction approaches to a constant value. Finally, the particle size also affects dispersion clearly. The finer the sand particle is, the wider the dispersion area is; and high concentration influences longer because the sedimentation of fine sand particles takes a longer time. In this study the medium diameter is taken as 0.25 mm, and the concentration at the center of sand placing area is reduced to 1,000PPM after 4 days of sand placed. It is concluded that the successful design of beach nourishment project depends on the placing location, the coastal facilities such as groins, detached breakwaters and submerged breakwaters as well as sea climate for the shortage of sediments resources.

碩士
國立臺灣海洋大學
河海工程學系
99
Yan-Liao beach in Northeast Coast National Scenic Area is a hot spot. In recent years, beach erosion and beach restoration issues, by the attention of many visitors. The goals of this study is to assess the effects of Yan-Liao beach nourishment after storm damage of Typhoon KROSA(2007). The selection of shore protection method was based on the consideration of effective sand dune protection, beach recreation function and water quality protection. To achieve the effective disaster prevention function, associated seaward dune nourishment and nourishment of subaerial beach were performed at Yen-Liao beach. According to the monitoring of beach nourishment project, the beach profile and beach width is steadily being restored. It is demonstrated that this kind of beach nourishment has a valuable reference for shore protection.

碩士
國立成功大學
土木工程學系碩博士班
101
The Tseng-Wen River is the highest utilization water system of water resources in Taiwan. With plenty of earth volume, the Tseng-Wen River has the best opportunity to achieve improved sand particle size to enhance coastal sediment transport. This study consists of laboratory and field tests in two stages: The laboratory test contains the basic physical properties test and the tumbling granulation test. The tumbling granulation test is divided into two method, and for the improvement of river sand operate the slake durability test, sieve analysis test and unit weight test. In situ test part The results of this study are as follows: tumbling granulation tests can achieve the effect of particle size increases, the oyster-shell particle size increased more significantly, but the instrument is still not mass-produced particles, as well as the high cost of production materials; The particles’ durability above medium high. In the initial period after completion of the Stone Weir, elevation in the front of the test area is rising; and loss of coastal sands are less, show that the Stone Weir slows down coastal erosion. But by waves, tides and other factors, and the lack of material strength, the Stone Weir is easily dragged by waves and led to deformation and loss.

Tese de mestrado, Geologia (Estratigrafia, Sedimentologia e Paleontologia) Universidade de Lisboa, Faculdade de Ciências, 2020
Nowadays we witness numerous problems associated with climate change, one of which is the intensification of coastal erosion. This is a process which is widely known in the Portuguese coast, being responsible for sediment remobilization specially in the low and sandy littoral. Not only does this contribute to the destruction of ecosystems and impacts liveability of the population in these areas but it also affects the tourism which is so important for the growth of a countries’ economy. To reduce the harmful impacts of coastal erosion, characterization of loan areas assumes a fundamental role for subsequent beach artificial nourishment – the most frequent implemented measure in other European countries to mitigate these effects. These operations use natural resources extracted from a feeder (by dredging) that are deposited on the troublesome coastal segments identified – it ensures protection and adaptation of coastal environments in a more natural way. For a loan area to become a possible source of sediment for beach artificial nourishment it must be in relatively close proximity and present specific characteristics, such as, the grain size (granulometry), mineralogic composition, fine and coarse percentages, carbonate percentage and a reduced contamination degree. Aside from knowing these characteristics locally it is necessary to overview how the different seismostratigraphic units are distributed, their relationship and geometry, quantification of unit’s volumes and for that seismic data is crucial. Once that characterization is complete it is important to make an economic viability study (if they are viable to be extracted and used to mitigate the erosional effects. With this in mind the CHIMERA project was delineated and financed by the Programa Operacional Sustentabilidade e Eficiência no Uso de Recursos (POSEUR-09-2016-48). This was applied to areas that had previously been identified as highly susceptible to coastal erosion: Costa da Caparica (CC), Espinho-Torreira (ET), Barra-Mira (BM) and Figueira da Foz-Leirosa (FFL). This thesis is based on the work developed during the Chimera project, starting with the acquisition of bathymetric, magnetic and single and multichannel seismic data until their interpretation, followed by the processing and interpretation of all the data. It is important to understand if this multidisciplinary methodology allow for a recount of geological history and if they complement each other for results and conclusions. The main motivation was to understand the coastal erosions impacts and how to proceed to mitigate them. In order to present a concrete study, I opted to focus in only one of the study areas – Barra-Mira (BM) as it showed a richer geological story. This work comprises the main steps of acquisition, processing, and interpretation of ultra-high resolution seismic data (UHRS) in more detail. This corroborated with other geophysical techniques (hydrographic and sedimentological data) led to: (a) definition and mapping of seven seismostratigraphic units; (b) volumetric quantification for each sedimentary class; (c) determination of usable sediment (only fraction described as medium to coarse sand) percentage. The total sediment thickness above the rocky substrate can reach to 104.26x106m3 (or 0.1 km3 ) but if we account the fact that for the sediment to be viable for beach nourishment it has to have a carbonate content of < 30%...

Beach nourishment is a soft engineering intervention that supplies sand to the shore, to increase the beach recreational area and to decrease coastal vulnerability to erosion. This study presents the preliminary evaluation of nourishment works performed at the high-energy wave-dominated Portuguese coast. The shoreline was adopted as a proxy to study beach evolution in response to nourishment and to wave forcing. To achieve this aim, images collected by a video monitoring system were used. A nourishment calendar was drawn up based on video screening, highlighting the different zones and phases where the works took place. Over the six-month monitoring period, a total amount of 25 video-derived shorelines were detected by both manual and automated procedures on video imagery. Nourishment works, realized in summer, enlarged the emerged beach extension by about 90 m on average. During winter, the shoreline retreated about 50 m due to wave forcing. Spatial analysis showed that the northern beach sector was more vulnerable and subject to erosion, as it is the downdrift side of the groin.

Scientists expect temperatures on Earth to get substantially warmer over the course of the 21st century, causing storm systems to intensify and sea-level rise to accelerate--these changes will likely have dramatic impacts on how the coastlines of tomorrow will evolve. Humans are also playing an increasingly important role in shaping Earth's coastal systems. Coastal scientists have only a general understanding of how these three factors--humans, storms, and sea-level rise--will alter the evolution of coastlines over the coming century, however. I conduct numerical modeling experiments to shed light on the relative importance of these factors on the evolution of coastline geomorphology.

In a series of experiments using a numerical model of large-scale (1 to 100's km) and long-term (years to centuries) coastline evolution that results from gradients in alongshore sediment transport, I explore how the patterns and rates of shoreline erosion and accretion are affected by shifts in 'wave climate' (the mix of influences on alongshore sediment transport of waves approaching from different directions) induced by intensified storm systems and the direct manipulation of the shoreline system by humans through beach nourishment (periodically placing sand on an eroding beach). I use a cuspate-cape coastline, similar to the Outer Banks, North and South Carolina, USA, as an important case study in my experiments. I observe that moderate shifts in the wave climate can alter the patterns of shoreline erosion and accretion, potentially increasing migration rates by several times that which we see today, and nearly an order-of-magnitude larger than sea-level rise-related erosion alone. I also find that under possible wave climate futures, beach nourishment may also induce shoreline change on the same order of magnitude as does sea-level rise.

The decision humans make whether or not to nourish their beach often depends upon a favorable economic outcome in the endeavor. In further experiments, I couple a cost-benefit economic model of human decision making to the numerical model of coastline evolution and test a hypothetical scenario where two communities (one 'rich' and one 'poor') nourish their beaches in tandem, under different sets of economic and wave climate parameters. I observe that two adjacent communities can benefit substantially from each other's nourishment activity, and these effects persist even if the two communities are separated by several tens of kilometers.

In a separate effort, I employ techniques from dynamic capital theory coupled to a physically-realistic model of coastline evolution to find the optimum time a community should wait between beach nourishment episodes ('rotation length') to maximize the utility to beach-front property owners. In a series of experiments, I explore the sensitivity of the rotation length to economic parameters, including the discount rate, the fixed and variable costs of beach nourishment, and the benefits from beach nourishment, and physical parameters including the background erosion rate and the exponential rate at which both the cross-shore profile and the plan-view coastline shape re-adjusts following a beach nourishment episode ('decay rate' of nourishment sand). Some results I obtained were expected: if property values, the hedonic value of beach width, the baseline retreat rate, the fixed cost of beach nourishment, and the discount rate increase, then the rotation length of nourishment decreases. Some results I obtained, however, were unexpected: the rotation length of nourishment can either increase or decrease when the decay rate of nourishment sand varies versus the discount rate and when the variable costs of beach nourishment increase.

Dissertation

A growing-interest for sustainable environmental engineering solutions able to combat erosion, enhance coastal safety and increase beach width is currently undergoing worldwide. Portugal is one of the countries that follow this pattern. Over the past few decades, a paradigm shift from “fighting” the forces of nature via hard engineering structures to “working with nature” solutions has emerged. Artificial sand nourishments have been in focus and regarded as a preferred method to mitigate erosion and maintain the coastline. This dissertation starts with a literature review about the past vs present evolution of the Portuguese littoral, giving emphasis to relevant aspects concerning its management (legal status and policy making), as well as to the coastal adaptation strategies that have been under discussion in the context of the future proposals for coastal protection, serving also to highlight the main problems and challenges currently faced by many coastal regions in Portugal. As an attempt to disseminate knowledge regarding the behavior of artificial nourishment operations, this study was further directed to assess a set of monitoring data, originally established to meet the Portuguese legislation and national policy on coastal management for controlling of the environmental impacts associated to the combined use of dredging and disposal activities, in the vicinity of harbors. Considering the improvement of the numerical modelling capacity, an equally important goal for achieving good predictability of the nourished beaches evolution, in this dissertation special focus was also given to the study of the beach profile change, as the beach fill responses are intrinsically related to the natural beach sediment dynamics. A recent and innovative numerical model with a simplified long-term description of the beach profile evolution, accounting for dune erosion and recovery, overwash/breaching, and the exchange of material between the bar and the berm has been herein applied for the Aveiro coast and targeted for a sensitivity test in the context of hypothetical nourishment interventions undertaken on an open sandy beach. This model was later explored via one of its integrated modules – the bar-berm material exchange sub-routine – yielding to an improved CS-model. Emphasis was given to the numerical modelling of subaqueous beach profile behavior in order to realistically describe the effects of the sediment release from longshore bars towards the beach and vice-versa, encompassing bar evolution, response of feeder mounds and the coupling between the subaerial and subaqueous changes. The theoretical developments were tested and validated against existing high-quality data from different field sites in USA. Overall, outputs of the application of the model to these three US case studies, look promising, demonstrating the potential for using rather simple models to quantitatively reproduce the main trends in the cross-shore sediment exchange taking place for longer timescales. This thesis constitutes a step forward the increase of knowledge in the topic of artificial nourishments, serving to support coastal engineers and managers at the decision-making.
Atualmente verifica-se um crescente interesse internacional por soluções de engenharia ambientalmente sustentáveis, capazes de combater a erosão, aumentar a largura da praia e manter a segurança das zonas costeiras. Ao longo das últimas décadas, tem-se assistido a uma mudança de paradigma no que toca à política de proteção da costa, que tem cada vez mais privilegiado o recurso às alimentações artificiais em detrimento das tradicionais estruturas de defesa costeira pesada. Esta dissertação começa com uma revisão da literatura sobre a passada vs presente evolução do litoral português, dando ênfase a aspetos relevantes da gestão costeira (estruturação e processo de tomada de decisões politicas), bem como as principais estratégias de proteção que têm sido discutidas no contexto das futuras propostas de adaptação para as zonas costeiras, servindo para destacar os principais desafios e problemas de algumas regiões do litoral português. Como tentativa de disseminação do conhecimento científico acumulado sobre o comportamento das alimentações artificiais, este estudo foi direcionado para análise de um conjunto de dados de campo recolhidos no âmbito de um programa de monitorização estabelecido para cumprir com a legislação portuguesa e a política nacional de gestão para controlo dos impactos ambientais associados ao uso combinado de operações de dragagem e deposição na vizinhança de portos marítimos. Considerando o melhoramento da capacidade de modelação numérica, um objetivo igualmente importante para se garantir uma boa previsibilidade da evolução de praias alimentadas, nesta dissertação, um foco especial é também dado ao estudo da evolução do perfil transversal de praia, uma vez que a resposta das alimentações estão intrinsecamente relacionadas com a dinâmica sedimentar natural. Foi apresentado e aplicado um modelo numérico recente e inovador, que segue uma descrição simplificada da evolução do perfil transversal de praia (incluindo a erosão/recuperação da duna, galgamento e troca de material entre a porção emersa/submersa) ao caso de estudo da costa de Aveiro e para uma análise de sensibilidades no contexto de múltiplos cenários hipotéticos de alimentações artificiais. Este modelo foi posteriormente explorado via um dos módulos que o integra – a sub-rotina da troca de material entre a berma e a porção submersa – conduzindo a uma versão melhorada do modelo. Atenção foi dada à modelação numérica do comportamento submerso do perfil, a fim de realisticamente descrever os efeitos do transporte dos sedimentos das barras em direção à praia e vice-versa, envolvendo evolução de barras naturais e artificiais (de alimentação). Os desenvolvimentos teóricos foram testados e validados através de dados de campo disponíveis para três casos de estudo nos EUA. No geral, resultados desta aplicação mostraram-se prometedores, demonstrando o potencial de modelos simples e robustos para reproduzir as principais tendências no transporte transversal de sedimentos a longo-prazo. Esta tese constitui um contributo no sentido do aumento do conhecimento sobre as alimentações artificiais de praia, servindo como suporte aos órgãos gestores do litoral na tomada de decisão.
Programa Doutoral em Engenharia Civil