O atual estudo visa cooperar na compreensão dos efeitos da passagem de tempestades extremas sobre os sistemas litorâneos através do estudo de caso na Desembocadura de Cananéia, localizada na Ilha Comprida - SP. O trabalho contou com campanhas de campo para levantamento de dados topográficos e coletas de sedimentos, análises das condições ambientais atuantes durante o período dos campos, determinação da evolução da linha de costa através da análise de fotos aéreas e imagens de satélite e simulações numéricas para caracterizar o regime de ondas atuante na região. Foram produzidos mapas temáticos para representar as cotas de inundação associadas a ocorrência de marés meteorológicas .Os resultados indicaram que a ação das ondas de tempestade se da principalmente por meio do transporte onshore-offshore nas escalas temporais diária e mensal. A evolução da linha de costa obtida apontou para maior eficiência das correntes de deriva litorânea na escala decadal. A comparação entre os resultados topográficos/volumétricos e da evolução da linha de costa evidenciam uma tendência erosiva nas adjacências do Pontal de Fora associada à incidência de eventos atmosféricos extremos para o período entre 2001 e início de 2012. Os resultados das determinações das cotas de inundação apontam que os maiores impactos locais associados às mudanças climáticas serão provenientes das alterações na frequência de ocorrência e intensidade das tempestades / The current study aims to cooperate in the knowledge about the effects of the occurrence of extreme storms on coastal systems through the case study of the Desembocadura de Cananéia, located on Ilha Comprida - SP. The work included campaigns of field survey to collect topographic data and sediment samples, analysis of environmental conditions during the period of surveys, determination of the shoreline evolution through analysis of aerial photos and satellite images and numerical simulations to characterize the wave regime present in the region. Thematic maps were produced to represent the flood hazard associated with the occurrence of storm surges. Results indicated that the action of storm waves occurs primarily by means of the onshore-offshore transport on daily and monthly time scales. The evolution of the shoreline obtained pointed to greater efficiency of longshore currents on the decadal scale. The comparison between the topographic/volumetric results and the evolution of the coastline shows an erosive trend in the vicinity of the Pontal de Fora associated with the incidence of extreme weather events for the period between 2001 and early 2012. The results of the determinations of flood hazard areas points out that the major local impacts related to the global climate changes will come from variations in the frequency of occurrence and intensity of storms

Extreme storms are responsible for rapid changes to coastlines worldwide. During the 2013/14 winter, the west coast of Europe experienced a sequence of large, storm-induced wave events, representing the most energetic period of waves in the last 60 years. The southwest coast of England underwent significant geomorphological change during that period, but exhibited a range of spatially variable and complex morphological responses, despite being subjected to the same storm sequence. The 2013/14 storm response along the southwest coast of England was first used as a natural field laboratory to explain the variability in storm response through the introduction and evaluation of a new classification of how sandy and gravel beaches respond to extreme storms. Cluster analysis was conducted using an unique data set of pre- and post-storm airborne Light Detection and Ranging (LiDAR) data from 157 beach sites and the calculation of volumetric beach changes and a novel parameter, the longshore variation index which quantifies the alongshore morphological variability in beach response. The method used can be applied to any sandy and gravel beaches where topographic data with sufficient spatial resolution is available. Four main beach response types were identified that ranged from large and alongshore uniform offshore sediment losses up to 170 m3 m-1 (at exposed, cross-shore dominated sites) to considerable alongshore sediment redistribution but limited net sediment change (at more sheltered sites with oblique waves). The key factors in determining the type of beach response are: exposure to the storm waves, angle of storm wave approach and the degree to which the beach is embayed. These findings provide crucial information for the development of coastal studies at regional scale, especially along coastal areas where abrupt changes in coastline orientation can be observed. A 10-year time series (2007-2017) of supra- and intertidal beach volume from exposed and cross-shore transport-dominated sites was used to examine the extent to which beach behaviour is coherent over a relatively large region (100-km stretch of coast) and predictably coupled to incident wave forcing. Over the study period, 10 beaches, exposed to similar wave/tide conditions, but having different sediment characteristics, beach lengths and degrees of embaymentisation, showed coherent and synchronous variations in sediment volumes, albeit at different magnitudes. This result is crucial for studying coastal changes in remote coastal areas or in areas where only few topographic data are available. The sequence of extreme storms of the 2013/14 winter, which represents the most erosive event over at least a decade along most of the Atlantic coast of Europe, is included in the data set, and three years after this winter, beach recovery is still on-going for some of the 10 beaches. Post-storm beach recovery was shown to be mainly controlled by post-storm winter wave conditions, while summer conditions consistently contributed to modest beach recovery. Skilful hindcasts of regional changes in beach volume were obtained using an equilibrium-type shoreline model, demonstrating that beach changes are coherently linked to changes in the offshore wave climate and are sensitive to the antecedent conditions. Furthermore, a good correlation was found between the beach volume changes and the new climate index WEPA (West Europe Pressure Anomaly), which offers new perspectives for the role and the use of climatic variations proxies to forecast coastline evolution. A process based model, XBeach, was used to model storm response at one macrotidal beach characterized by the largest sediment losses during the 2013/14 sequence of extreme storms. Beach volume changes were modelled over hypothetical scenarios with varying hydrodynamics conditions and beach states to investigate the relative roles of hydrodynamic forcing (i.e., waves and tides), beach antecedent state and beach-dune morphology in beach response to extreme storms. This modelling approach is applicable to any beach system where process based models have been implemented. Beside significant wave height and peak wave period, the beach antecedent state was shown to be the dominant factor in controlling the volumes of sediment erosion and accretion along this cross-shore dominated beach. Modelled volumes of erosion were, on average, up to three times higher along an accreted beach compared to an eroded beach for the same wave conditions. The presence of a dune, being only significantly active during spring tides and storm conditions along this macrotidal beach, was shown to reduce erosion or even cause accretion along the intertidal beach. This work provides a detailed, quantitative insight of the hydrodynamic and morphological processes involved in storm response and beach recovery on a number of spatial and temporal scales. This improved understanding of the potential impact of extreme events will hopefully aid future research efforts and ensure effective management of sedimentary coastlines.

Shell Key and Mullet Key are two sandy barrier islands on the West Central Florida coast near the mouth of Tampa Bay. These islands are part of an interconnected barrier-inlet system that includes Pass-a-Grille (PAG) and Bunces Pass. Shell Key is a relatively new island about 40-years of age that formed in between the two inlets of Bunces Pass and PAG. Mullet Key is an island to the south of Shell Key situated between Bunces Pass and the main Tampa Bay channel that has demonstrated large scale upward shoaling events. Using numerical modeling, the wave and tidal conditions at the dual-inlet system were investigated in order to understand the hydrodynamic conditions that drive the morphology change. Historical aerial imagery and historical nautical charts were analyzed to determine the large scale accretionary and erosive changes that happened in the study area from 1873 to 2018. Four historical nautical charts, from 1873, 1928, 1966, and 1996 were digitized to create bathymetry maps of the two islands, their adjacent inlets, and the ebb shoals. These historical bathymetry maps were compared with the bathymetry survey by this study in 2016. The research goal of this thesis is to investigate the mechanism of origin and development of two barrier islands along the coast of West Central Florida through a time series of photos combined with numerical modeling. Based on aerial photos from 1984 to 2018, the overall shape and orientation of ebb shoals at both Bunces Pass and PAG were analyzed in order to examine the effect that the 30 year swash bar cycle at Bunces Pass has on a connected inlet system. The ebb shoal orientations were compared to see how swash bar initiation would affect the two ebb shoals; most notably Bunces Pass ebb shoal. A bending of the entire Bunces Pass ebb shoal was identified over the 2002-2018 time span corresponding to the development of a large sand feature located here. Further numerical modeling was conducted at PAG to determine the factors controlling the formation of Shell Key. Before the 1970s, the PAG inlet included two branches, the North PAG Channel and the South PAG Channel. A major dredging event took place at the North PAG Channel in 1966 causing significant widening and deepening of the channel. This dredging event was simulated to quantify the impact to the natural flow pattern. The 1966 dredging project had a significant impact to the overall flow pattern, increasing the ebb jet flow velocity by 0.8 m/s over the dredged area and significantly decreasing flow velocity by -0.4 m/s over a large area where the South PAG Channel was previously located. This artificially induced change of flow pattern resulted in the closure of South PAG Channel and the corresponding development of Shell Key.

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.

In an era of dawning anthropogenic climate change, people of atoll nations face grievous threats to their future. Rising sea levels, warming oceans, and changing weather patterns conspire with economic isolation, rapidly growing populations, and the loss of traditional livelihoods to perpetuate conditions of dependence and wardship which threaten the very existence of their island homes. This project examines an atoll nation of the equatorial Pacific, the Republic of the Marshall Islands, where the outward appearance of pristine tropical paradise belies a tragic history of nuclear weapons and ballistic missile testing at the hands of the US military. While the islands have been consistently framed in rhetoric which stresses vulnerability, smallness and unsustainability, this project contests the limited scope of the regimes of power in Oceania by considering how the independent, grassroots actions of local groups of islanders have achieved surprising and dramatic results in defiance of the policies and planners at the top. In developing a design proposal for the contemporary condition, this thesis examines the persistent ways in which the islands and people are framed by outsiders. This project engages with the social, political and natural history of the atolls: common tropes are challenged by the actions and agency of a people who have dealt with imperialist outsiders in sophisticated and conscious ways. It explores the traditional cultural practices which enabled the ancestors of the Marshallese people to flourish, and suggests that it is at the level of actions by ordinary people that the most fertile potentials lie, and are in fact already being played out. What forms of urbanism might be appropriate in this environment? How can islanders effectively manage their landscape and engage with the natural processes - as their ancestors once did to a remarkable degree? By pairing traditional techniques with modern technologies, a proposal is synthesized which could empower the contemporary Marshallese to transform their landscape and develop sustainable livelihoods in this extreme and dynamic environmental condition: to build a future which offers the best aspects of both traditional and contemporary ways of life.

Tropical Storm Debby affected the Gulf coast of Florida in late June, 2012. The storm's southerly approach temporarily reversed the annual net southward longshore sediment transport. The energetic conditions associated with Tropical Storm Debby can be seen in the wind, wave and tidal measurements taken from both onshore and offshore weather stations around the dual tidal inlets system of John's Pass and Blind Pass, approximately 25 kilometers north of the mouth of Tampa Bay. The energetic and persistent southerly forcing, in addition to higher storm induced water levels and wave heights, resulted in atypical beach erosion and sediment deposition on the ebb tidal deltas of the two inlets and the surrounding beaches. The John's Pass ebb delta gained 60,000 cubic meters of sediment and the Blind Pass ebb delta gained 9,000 cubic meters as a result of the storm. Shoreline position, beach profile and offshore bathymetric surveys conducted before and after Tropical Storm Debby illustrate the changes in the coastal morphology such as the development of an offshore bar south of Blind Pass and erosion of the dry beach north and south of John's Pass. The Coastal Modeling System (CMS) was used to simulate wave and tide-driven current fields during the passage of the storm. The modeled wave field qualitatively illustrated the shadowing effect of the Tampa Bay ebb delta in reducing the southerly approaching storm wave energy arriving at the study area during the storm. The tidal flow patterns through the inlets and over the ebb tidal deltas were considerably different during the storm, as compared to normal tidal cycles.

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.

The evolution of landscapes and seascapes in time is the result of the constant interaction between flows and topography. Flows change topography, which in turn change the flow. This feedback causes evolution processes to be highly non-linear and complex. When full analytical derivations of the co-evolution of topography and flow are not possible without oversimplifications, as is the case in river bends, recent large topographical datasets and modern computers allow for correlations between horizontal (planview) and cross-sectional geometry of channels. Numerical analysis in the Mississippi and Trinity rivers indicate that the type of correlation between river radius of curvature and bankfull channel width depends on the migration behavior of the river. In other cases, channel topography may only have a second-order effect on its own evolution, as is the case for fully depositional turbidity currents, and the evolution of aeolian field topography may only be a function of this topography. I show that in these situations, changes in topography may be decoupled from details of the flow field and modeled very easily with a good accuracy. / text

In an era of dawning anthropogenic climate change, people of atoll nations face grievous threats to their future. Rising sea levels, warming oceans, and changing weather patterns conspire with economic isolation, rapidly growing populations, and the loss of traditional livelihoods to perpetuate conditions of dependence and wardship which threaten the very existence of their island homes. This project examines an atoll nation of the equatorial Pacific, the Republic of the Marshall Islands, where the outward appearance of pristine tropical paradise belies a tragic history of nuclear weapons and ballistic missile testing at the hands of the US military. While the islands have been consistently framed in rhetoric which stresses vulnerability, smallness and unsustainability, this project contests the limited scope of the regimes of power in Oceania by considering how the independent, grassroots actions of local groups of islanders have achieved surprising and dramatic results in defiance of the policies and planners at the top. In developing a design proposal for the contemporary condition, this thesis examines the persistent ways in which the islands and people are framed by outsiders. This project engages with the social, political and natural history of the atolls: common tropes are challenged by the actions and agency of a people who have dealt with imperialist outsiders in sophisticated and conscious ways. It explores the traditional cultural practices which enabled the ancestors of the Marshallese people to flourish, and suggests that it is at the level of actions by ordinary people that the most fertile potentials lie, and are in fact already being played out. What forms of urbanism might be appropriate in this environment? How can islanders effectively manage their landscape and engage with the natural processes - as their ancestors once did to a remarkable degree? By pairing traditional techniques with modern technologies, a proposal is synthesized which could empower the contemporary Marshallese to transform their landscape and develop sustainable livelihoods in this extreme and dynamic environmental condition: to build a future which offers the best aspects of both traditional and contemporary ways of life.

There are only a few detailed measurements of the cross-shore variation in the net sediment transport and beach evolution for single or multiple swash events, and no data showing the influence of long waves and wave groups on swash zone morphology. Novel laboratory experiments and numerical modeling have been performed to study the influence of long waves and bichromatic wave groups on sediment transport and beach morphodynamics in the swash zone. Due to complex processes, difficulties in measuring, and very significant difficulties in isolating the morphodynamic processes induced by long waves and wave groups on natural beaches, a laboratory study was designed to measure in very high detail the bathymetric evolution of model sand beaches under monochromatic waves, long wave and short wave composites (free long waves), and bichromatic wave groups (forced long waves). Net sediment transport, Q(x), and beach morphology changes under the monochromatic waves were analyzed and compared to conditions with and without the free long waves, and then compared with the bichromatic wave groups. A range of wave conditions, e.g., high energy, moderate energy, and low energy waves, were used to obtain beach evolution ranging from accretionary to erosive, and including intermediate beach states. Hydrodynamics parameters, e.g., instantaneous water depths, wave amplitudes, run-up and rundown, were also measured to study and test a sediment transport model for the swash zone, based on modifying the energetic-bedload based sediment transport equations with suspended sediment. The experimental data clearly demonstrate that for the monochromatic wave conditions, beach evolution develops erosion for high steepness waves and accretion for lower steepness waves. The model beach profile evolutions are similar to natural beaches, and form and develop bars and berms over time. Adding a free long wave to the short wave in the composite wave results in changes to the overall trend of erosion/accretion of the beach profile, but the net transport pattern does not change significantly. The short wave strongly dominates beach behavior and the net transport rate, instead of the free long wave in the composite wave. The free long wave, however, carries more water and sediment onshore, leading to an increase in shoreline motion and wave run-up further landward. The long wave influences the structure and position of the swash bar/berm, which generally tends to move onshore and forms a larger swash bar/berm for higher long wave amplitudes. The free long wave also increases overall onshore sediment transport, and reduces offshore transport for erosive conditions. The long wave tends to protect the beach face and enhances onshore transport for accretive conditions, especially in the swash zone. In contrast, for bichromatic wave groups having the same mean energy flux as their corresponding monochromatic wave, the influence on sediment transports is generally offshore in both the surf and swash zone instead of onshore. The swash berm is, however, formed further landward compared with the berm of the corresponding monochromatic wave. The sediment transport patterns (erosion or accretion) generated by the bichromatic wave group or corresponding monochromatic wave are similar, but differ in magnitude. The numerical model, starting in the inner surf zone to reduce the effect of poor breaker description in the non-linear shallow water equations, can produce a good match between observed data and the modeled hydrodynamics parameters in the SZ. The sediment transport model shows the important role of suspended sediment in the swash zone. In contrast with the observed data, energetic-based bed-load models predict offshore sediment transport for most wave conditions because of negative skewness. The modified sediment transport model, with added suspended sediment terms and optimized coefficients, produces a good match between model results and observed data for each wave condition, especially for low frequency monochromatic waves. The optimized coefficient set corresponding to particular monochromatic wave conditions can be used to predict the net sediment transport quite well for some composite wave conditions. Overall, the same optimized coefficient sets can be applied to predict the correct overall trend of net transport for most composite wave conditions. However, the predicted net transport for the bichromatic wave groups does not match well with the overall net transport patterns. There is no set of single transport coefficients that can be used to predict sediment transport for all wave conditions. This suggests that the present sediment transport models cannot predict evolution correctly, even for conditions which represent only perturbation from those for which they were calibrated.