APRÈN. Portal de la producció docent del professorat de la UPC

This study presents an analytical model aiming to forecast the evolution of barrier beachesaround one hundred years upfront. The general goal is to create a tool for policy supportthat can help a proper coastal management of the particular environment formed bybarrier beaches.The model takes into account storms' impact and geotechnical settlement, trying toreproduce the complexity of forcings applied to barrier beaches. The model developmentis mainly based on the model developed by Rosatiet al.(Rosati et al. 2009). Erosion andoverwash are the two storms' impacts considered. The geotechnical settlement is focusedon primary consolidation. The results are discussed in terms of model development, butalso in terms of policy support with a tipping point approach. The model is tested withdata from the Trabucador bar, at the Ebro Delta, in Spain.

This thesis aims to provide a general overview of the present state of the coast of Liberia, carrying out an integral characterization (that will include weather, geology, litoral cells, etc.). This characterization will be used to assess its present vulnerability to present conditions a,d to determine the possible impacts due to climate change.

Flic and Flac beach is one of the most touristic beaches in Mauritius. It has a coral reef that at present provides shelter to the coast. The main objective of the study is to evaluate the effects of the sea level rise due to climate change on the beach to determine possible management policies.

Natural and man made embayment beaches are a common feature along the Catalan coast. Many of these embayment beaches have experience changes in shoreline position jeopardizing the protective and recreational functions of the beach. Therefore, an understanding of the morphological variability of this system is needed in order to facilitate an effective and sustainable coastal zone management. The present study was undertaken with the objectives of: 1) study the shoreline evolution of the Catalan coast, 2) determine medium term oscillation and the forcing mechanisms governing this process by means of a theoretical model and 3) evaluate the frequency of the theoretical model using the last 7 years of wave data. Data from nine sandy beaches along the Catalan coast consisted on previously define digitalized coastlines from the Environmental Ministry, the Cartographic Institute of Catalonia and satellite images from Google Earth. Results from the shoreline evolution showed that the embayed beaches of Catalonia presented a stable behavior, beaches with the same morphology followed a same trend in the stability test propose by Hsu, 1989. The results of beach mobility showed a non-uniform behavior of the sub-aerial beach width within a beach and along the Catalonian coast. The mayor difference between beaches was due to the orientation of the shoreline, the beach type and the exposure to wave conditions. Embayed beaches also exhibited a wide degree of beach rotation. Beaches with similar morphology show similar degrees of rotation. A theoretical model of the main configurations observed during the study period has been developed for each beach. Results showed that exposed beaches presented an anticlockwise, quasi-uniform and clockwise configuration, while semi-exposed beaches only show a higher anticlockwise and a lower anticlockwise configuration. In the analysis of wave forces on the embayment, it has been observed that wave direction was the primary forcing mechanism that generated changes in beach configuration (e.g. beach rotation), however the combination of wave height, period and direction where the responsible of the response time of the beach to a new configuration. The percentage of occurrence of the wave climate during 2001 to 2007 suggested that some beaches have tendency towards one configuration, in most cases to a higher anticlockwise rotation. Differences between beaches can be attributed to the shelter nature of the beach, the orientation and the effect of the natural or man made headland.

Real coastal waves measured at 4 different locations in the world were analyzed in detail. Long travelled swell measured in the Pacific coast of Costa Rica, wind swell from the Atlantic coast of Costa Rica, short period wind waves from the Ebro Delta in Mediterranean coast of Spain, and waves measured during the passing of Hurricane Wilma near Cancun, Mexico were analyzed. A total of 5795 wave records from the sites above were analyzed. A statistical stability analysis of the wave data was done. The measured wave height distribution was compared with the Raleigh distribution. The corresponding significant wave height and period distribution based on the zero down crossing method was obtained for all the records. The joint individual wave height-period distribution was obtained and the characteristic statistic wave heights and periods were obtained. The time variation of these parameters, including the skewness and kurtosis of the time series were obtained to determine the statistical stability of the data. A detailed spectral analysis using the Fourier transform was done on all the records. The whole record for each location was represented as time variant frequency energy spectrogram. The highest measured record's spectra for each site were examined in detail. The peakedness, band width, grouping, regularity spectral parameters, and the six principal moments of all the wave records were obtained. The spectra were then compared to the JONSWAP spectrum. Special attention was taken into the non-linear components present in the spectra. Temporal and energetic wave grouping parameters were analyzed using the run length theory. Low frequency modulation was examined against grouping observation. The capability of the variance spectra based on the Fourier transform to describe the measured wave grouping was analyzed and confirmed through the spectral grouping parameter Ka. The long waves present in the records were analyzed using a low pass filter. Spectral analysis was carried out on the filtered time series. The results between the different sites were compared and Longuet-Higgins set down equation under wave groups was calibrated and validated to predict the long wave spectral significant wave height, given the wave spectral significant height, the peak spectral period and the water depth outside the breaker zone. A spectral analysis using the Hilbert Huang method was done to the most energetic measured events of each record. A detail comparison was done between the result of the Fourier transform variance spectral analysis and the Hilbert Huang method. The limitations of the Fourier based spectra and the new Hilbert Huang transform spectra were examined in detail.

The concept of a twin storm refers to two sequential storm wave heights that are separated by a short period of calm water. In the past, these have often been regards as one storm with a ‘double peak' or as two independent events. This thesis will focus on determining a pattern of occurrence by analyzing the characteristics of the first storm and observing if these characteristics may have an influence on the occurrence of the second storm. Data has been taken from four areas along the Catalan coast and used to calculate probabilities of twin storm events based on maximum storm significant wave height, storm duration, and time of year of occurrence. Using these calculated probabilities, a risk analysis has been performed in order to decide if preventive action should be taken during the period of calm water in hopes of reducing the damage caused by the second storm. This thesis presents the results as well as conclusions that can be drawn from the analysis.

Coastal engineering deals with complex systems that involve processes that are not fully understood. Physical modeling has become an important tool in the study of these processes. It allows researchers to control the conditions that are being studied, and simplify the system to include only what is desired. In a coastal system waves are often one of the main driving forces of these processes. Because of this it is of great importance to have the ability to reproduce the natural wave conditions in the laboratory settings. When generating waves with a low relative water depth, and/or a high wave steepness using first order wavemaker theory the resulting waves are contaminated with an unwanted secondary wave, which causes the generated wave profile to change as the wave travels along the wave flume. The aim of this study is to find under which conditions this issue takes place in the CIEMito wave flume of the Laboratori d'Enginyeria Marítima (LIM), and to implement a second order wavemaker theory capable of suppressing it. Several wavemaker theories were studied, the first order wavemaker theory, and several second order wavemaker theories. Due to issues arising with the implementation of most of the second order theories, only the first order wavemaker theory and the second order wavemaker theory given by Madsen (1971) were applied to the CIEMito wave flume. Thirty-seven different wave conditions were tested in the CIEMito wave flume using first order wavemaker theory. From this the issues with first order wave generation were studied. Due to issues with the physical wave flume the second order theory could not be tested there. Instead, a numerical wave flume based on PFEM (particle finite element method) was validated so that the CIEMito wave flume could be simulated with this numerical model. Four of the wave conditions tested in the physical wave flume were simulated using both first order and second order Madsen wavemaker theory. From this the capability of Madsen's second order wavemaker theory of suppressing the unwanted secondary waves was assessed.

The aim of this research project was to increase the knowledge about the hydrodynamic processes that take place around a permeable Low-Crested Structure (LCS) when this structure is under wave attack. Further, the intention is to place the hydrodynamic data garnered here within the context of the current state of scientific research related to permeable LCS so as to build on previous literature and works associated to the hydrodynamics of LCS. In order to carry out the research, physical modelling experiments were conducted in the wave flume at the Laboratori d'Enginyeria Marítima (LIM). These experiments were sponsored by the larger research project of related to Composite Modelling of the Interactions Between Beaches and Structures (CoMIBBS). It is hoped that the work here will be able to contribute in some way to the goals of the larger CoMIBBS project. It was indispensable to conduct the experiments related to permeable LCS making use of various wave attack scenarios including varied wave heights and wave slopes. Two types of structures were tested in these experiments, emerged and submerged. All of the information about the research project and the facility specifics, as well as the structure details, the wave scenarios, the recorder locations and data collection methods are detailed within Chapter 2. The results acquired from the experiments conducted were analysed in terms of the following aspects: • wave transmission characteristics • wave reflection characteristics • spectral changes • current velocities – magnitude variation and vertical distribution Trend analysis revealed aspects of the hydrodynamics which were considered more significant than others; it also aided in distinguishing the effects of certain parameters on other data. The results garnered were compared to existing formulas and categorizations relating to the hydrodynamic indicators considered paramount, which were (1) the transmission coefficient, (2) the reflection coefficient, and (3) the spectral energy distribution. The relationships between the results of the physical modelling and the calculated results of the formulas were established and examined for connective trends. This process ascertained the relevance of the formulas to the LCS under examination and the hydrodynamic patterns noted. 3 Another part of the thesis was to numerically simulate the water movement through the permeable LCS. This was done with the use of the LIMWAVE model developed at the Universitat Politècnica de Catalunya (UPC). With this model, it was attempted to determine the correlation between the physical modelling results and numerical modelling results. From these simulations, it was noted that the numerical model represented the water level on the leeside of the structure fairly well, save for slight differences resulting from the piling up effect. The relation between the models of the water level on the seaward side of the structure was dependent on whether or not reflection was activated, in which case, a standing wave was produced. The most important conclusions found from the works are as follows: 1. The coefficients Kt and Kr as well as the shape of the frequency spectra are linked to the wave steepness, which seems to be a very important yet often underestimated parameter. 2. The inclusion of the structure's permeability into the existing formulae for the prediction of the coefficients Kt and Kr will greatly increase the accuracy of the formula. This work has opened up many more aspects of the application of hydrodynamic observation and modelling. A set of research exercises should be carried out in order to complement this report and relate the findings in more practical applications. Additional tests related to highly permeable low-crested structures both as offshore breakwaters and as submerged offshore reefs are required to gain a better understanding of the effect of permeability on the transmission and reflection of waves. Further, these tests should be conducted on selected sites in order to truly understand the effects of permeable LCS in the field. From these test results it is recommended that a review of the existing formulas for the transmission coefficients should be made to include the permeability of the structures. Also, an attempt should be made to examine in detail the relationship between the wave steepness and the various parameters under examination. The results of these findings can have several practical applications: the design of an improved structure with less scouring which is more environmentally friendly, as well as the probably use of wave energy as a power source.

Found on the NW Mediterranean, the Catalan coast is not only subjected to morphological changes driven by physical natural processes but also by significant changes in local dynamics that result from the numerous coastal structures that are found on its realm. The armoring of coastal stretches is a common selected option for protecting valuable infrastructure and the hinterland. Nonetheless, the induced effects of these kinds of structures are still an open question that can be only answered by local means and remain unrevised for the area. In the present study an inventory of all the armored structures found along the Catalan coast was carried out. An approximate estimation of 110km of total armoured coast that accounts for 19% of the total Catalan coast was found and synthesized into eight associative structure-beach pattern groups by considering: morphological classification of beach and seawall characteristics. Los Vascos at the northern Ebro hemi delta and Sant Pol de Mar in the Maresme region were selected as representative sites of two of the associative structure-beach proposed groups for in depth analysis. A review of the reported effects accrued to structures on the adjacent beach found on literature was updated and tested at each representative site. The effects of found structures at each site were analyzed in the longshore and crosshore dimension through numerical simulations. For the longshore dimension, GENESIS (Generalized Model for Shoreline Changes) was used to simulate the changes in the plan shape due to longshore transport accounted for wave angle of approach and longshore gradient in wave height at both sites. Seasonal, yearly and long term analysis were performed, exhibiting differences in magnitudes of sediment transport rates and dominant mechanisms between sites as denoted by the different parameter values found during calibration .At Los Vascos the average net sediment transport was estimated in 37095.16m3/year where finer sediments are distributed by an almost unidirectional longshore current towards the northern part of the hemi delta. While for the case of Sant Pol de Mar, the sediments are redistributed in both north and south directions along the year, producing a relatively lower net average transport rate obtained in 14785.47m3. Through simulations with and without the presence of structures, the effects in the longshore transport and shoreline response accrued to the structures only were found. Maximum beach erosion and areas of influence were obtained. Expected effects in the long term were found through 10 years simulations. Furthermore, variations in 0.25m and 0.5m water level increments, 5% and 10% Hs and Tp increments, and 5% and 10% storm frequency increments were tested individually and in combination for the year 2057 as possible future conditions. An additional sensitive analysis was gained during the future condition simulations. Increments in storm frequency as the main driver for shoreline change resulted in higher shoreline variability than water level increments. As expected, combinations in 10% increments of wave parameters (i.e., 10% Hs and 10% Tp ) simulations produced larger shoreline responses and it was proved that the Hs plays a dominant role in the longshore sediment transport. Furthermore, it was found that in places as Sant Pol de Mar where significant diffraction effects governs wave transformation, increments in wave period result in higher shoreline variability than increments in wave heights. iv As for the cross-shore dimension, the SBEACH model (Storm Induced Beach Change Numerical Model) was used to analyze the effects in the beach in front of the structures at each site. Formation of scour and beach width diminishing were successfully obtained in a qualitatively basis and proved to be the cross-shore induced effects when comparing theoretical non walled final profiles obtained through simulation. Moreover, higher insight was achieved regarding the obtained GENESIS responses by setup performing tests of the two available solutions of the one line analytical model developed by Hanson and Krauss (1987) fed by the most representative wave for Los Vascos site in morphological terms. The solution for a semi infinite wall where no flanking effect possible resembled in higher accurate manner the obtained GENESIS responses proving that this was the solution offered by the model. Finally, it was proven that if the erosion behind the structure and downdrift erosion are subjects to be quantitatively analyzed the solution for a semi infinite wall where flaking effect is possible can is very useful aid in addition with GENESIS simulations.

The objective of this thesis is to introduce Floating Wave Filters (FWF), which are floating structures anchored to the sea bottom that aim to block short-period waves and transmit long-period waves in order to improve surfing conditions. Short-period waves are generated by local winds, their periods do not exceed 4 seconds and wave heights are less than half a meter. Long-period waves refer to swell waves, with periods longer than 8-10 seconds and variable heights.