Hydrodynamic performance of free surface semicircular breakwaters

Different types of breakwaters have been developed in the past for the protection of valuable coastal property, commercial activity and beach morphology. Among these, gravity-type breakwaters are the most common and provide good surface wave attenuation. However, these breakwaters are not always suitable due to their adverse impact on the coastal environment. To alleviate the problem, free surface breakwaters with a variety of caisson designs have been proposed and developed. The main advantages of such breakwaters are low capital cost, freedom from silting and scouring, short construction period, circulation of water beneath the breakwater and exertion of relatively low hydrodynamic forces on the structure as compared to conventional breakwaters. However, complete tranquillity on the lee side is not likely to occur due to wave energy transfer through the permeable parts of the breakwater. The degree of wave attenuation primarily depends on the configuration of the breakwater, the water depth and the incident wave conditions. The hydrodynamic performance of such free surface breakwaters is the subject of this thesis. Semicircular breakwaters mounted on a low-crested rubble mound structure were successfully built for harbour protection in Japan and China. However, the concept of having semicircular structures as free surface breakwaters has not yet been explored by the research community. As a result, this research is initiated with the aim of developing a free surface semicircular breakwater (SCB) that would serve as an anti-reflection barrier and provide reasonably good wave protection to coastal and marine infrastructures. To meet this research goal, a free surface SCB models were constructed and tested in a wave flume under various wave conditions. The experiments were conducted in three stages. For the first stage, the SCB model was initially tested without any perforations on the curved surface (i.e. a solid SCB) for different depths of immersion from the still water level in the wave flume. For the second stage, the front curved wall of the model was subsequently perforated with rectangular openings of different dimensions, producing front wall porosity of 9, 18 and 27%. Following this, two rows of rectangular openings near the crest of the rear curved wall were provided so as to facilitate water infiltration and escape of the run-up waves. For the third stage, additional effort was made to extend the draft of the breakwater by adding a wave screen at the front or/and rear. The screen porosity was 25, 40 and 50%. The hydrodynamic characteristics of the SCB models were investigated in both regular and irregular seas through a series of systematic experimental programme. The water surface elevations were measured at different locations upstream and downstream of the models to determine the coefficients of wave transmission (CT), reflection (CR) and energy dissipation (CL) as well as the wave climate coefficients in front and inside the breakwater chamber. The horizontal wave forces exerted on the SCB models and the wave screen(s) were also measured and subsequently normalised to yield the force coefficients in the analysis. These hydrodynamic coefficients for the respective test cases are presented and discussed in this thesis. The experimental results revealed that even though the solid SCB was a better wave attenuator than the perforated ones, it produced a considerable amount of wave reflection. The perforated SCB with 9% porosity of the front wall (denoted as SCB9) outperformed the other perforated breakwater models; however, it produced high wave transmission when the draft was limited and subjected to longer period waves. Hence, wave screens were added to further enhance the performance of the SCB9. The SCB9 with double screens of 25% porosity was found to provide the highest hydraulic performance. Empirical equations were developed using a multiple regression technique to provide design formulae for wave transmission, wave reflection and horizontal wave forces. The proposed empirical equations showed good agreement with the experimental data. These equations are intended to be of direct use to engineers in predicting the hydrodynamic performance of free surface SCBs. However, sensible engineering judgement must be taken while using these equations as they are based on small scale laboratory tests

Assessment of Wave Attenuation Performance of the Tanjung Piai Breakwater Using Spectral Wave Analysis

Tanjung Piai is one of Malaysian heritage sites situated at the southernmost tip of the Asian continent. Tanjung Piai provides a conducive coastal habitat for many mangrove species, including the rare species of Bruguiera hainesii and Bruguiera sexangula. Coastal erosion resulting in shoreline retreat that was detected dating back to the 1930s. Due to uncontrolled coastal development ij the vicinity of Tanjung Piai, the erosion rate at the mangrove site had accelerated since the recent decades. This led to significant land mass loss that threatens the eco-system. Various measures have been undertaken to mitigate the erosion problems. Some measures were adopted to permanently harden the shoreline preventing sea water from reaching the mangroves. However, this resulted in mangroves gradually dying along the coast.. A series of offshore breakwaters were subsequently planned to reduce wave energy, mitigate the erosion and protect the existing mangroves growing along the wave-exposed coastline. This study aims to assess the impact of offshore waves, squalls and wind-generated waves to the Tanjung Piai coastline (with and without the breakwaters) using a two-dimensional numerical model. A survey of the site and details of the breakwaters’ design were incorporated in the modelling. The numerical results show that the breakwaters are able to reduce offshore wave heights up to 66%. The breakwaters can attenuate offshore waves more effectively compared to squalls and wind-generated waves. The breakwaters were completed in 2019. They were proven to be able to provide protection to the mangroves along the coast of Tanjung Pia

Assessment of Wave Attenuation Performance of the Tanjung Piai Breakwater Using Spectral Wave Analysis

Tanjung Piai is one of Malaysian heritage sites situated at the southernmost tip of the Asian continent. Tanjung Piai provides a conducive coastal habitat for many mangrove species, including the rare species of Bruguiera hainesii and Bruguiera sexangula. Coastal erosion resulting in shoreline retreat that was detected dating back to the 1930s. Due to uncontrolled coastal development ij the vicinity of Tanjung Piai, the erosion rate at the mangrove site had accelerated since the recent decades. This led to significant land mass loss that threatens the eco-system. Various measures have been undertaken to mitigate the erosion problems. Some measures were adopted to permanently harden the shoreline preventing sea water from reaching the mangroves. However, this resulted in mangroves gradually dying along the coast.. A series of offshore breakwaters were subsequently planned to reduce wave energy, mitigate the erosion and protect the existing mangroves growing along the wave-exposed coastline. This study aims to assess the impact of offshore waves, squalls and wind-generated waves to the Tanjung Piai coastline (with and without the breakwaters) using a two-dimensional numerical model. A survey of the site and details of the breakwaters’ design were incorporated in the modelling. The numerical results show that the breakwaters are able to reduce offshore wave heights up to 66%. The breakwaters can attenuate offshore waves more effectively compared to squalls and wind-generated waves. The breakwaters were completed in 2019. They were proven to be able to provide protection to the mangroves along the coast of Tanjung Pia

A decade after the tsunami: preliminary exploration deposit layer of sediment at coast area of Kedah, Malaysia

Study on tsunami deposits is done after a decade of the incident happened at Kedah, Malaysia. This article discusses the characteristics, measurement and thickness of tsunami deposits. It also provides the latest remaining evidences of the tsunami incident including imbrication pattern of cobbles, types of coastal protection and plants at the affected area. Run-up heights and inundation distance were taken into account for field exploration and investigation. This study may provide opportunities to understand how remaining evidences of tsunami could be tracked and recorded

MORPHODYNAMICS OF THE TELUK NIPAH SHORELINES

The coastal retreat is one of the most common problems taking place at littoral zones, and it will only become an issue if the area is overwhelmed with commercial developments and anthropogenic activities. The coastal erosion experienced by the shoreline of Teluk Nipah, which is located at the west of Pangkor Island in Malaysia, has triggered some levels of attention among the local authorities and community. The root cause of the erosion and shoreline retreat rates remain uncertain, is due to the unavailability of records studies on beach morphodynamics in the past. Hence, this study aims to assess the decadal shoreline changes of Teluk Nipah by using remote sensing technology. Landsat satellite imageries, which ranges from 1990 to 2018, have been acquired for quantification of the shoreline change rate at Teluk Nipah using a GIS software - ArcGIS. The analysis results indicated that the shoreline is dynamic and unstable between the 1990s to 2010s. The most populated area of the shoreline experienced critical erosion that requires immediate attention by the stakeholders

SHORELINE MAPPING OF TELUK NIPAH USING DIGITAL SHORELINE ANALYSIS SYSTEM (DSAS) IN ARCGIS WITH TIDAL CORRECTION

Shoreline characterization using remote sensing technologies is a useful tool to determine the historical shoreline changes of a specific coast. Tidal variation is one of the important factors that should be considered in the shoreline mapping exercise. However, the tidal correction has often been neglected due to the need to access the historical tidal data series for the study site. As a result, the accuracy of the shoreline mapping without tidal correction is ambiguous. Hence, this study aims to establish the historical shoreline mapping of Pantai Teluk Nipah, Pangkor Island, Malaysia, with a tidal correction, using ArcGIS software. For 30 years of the study period, Landsat satellite imageries were processed via ArcGIS to quantify the shoreline change rate. Based on the previous shoreline mapping study without the tidal correction, transect 23 of Pantai Teluk Nipah has undergone severe erosion where the erosion rate is up to –6.83 m per year. With consideration of tidal correction, the shoreline erosion rate at the same transect has reduced to –3.87 m per year, which is consistent with the current beach condition at Pantai Teluk Nipah

Recent Advancement of Sustainable and Renewable Energy in Osmotic Power Generation

Investment in clean energy is demand in this century due to abundance of CO2 accumulation in the world to cause several environmental issues. Therefore, harvesting clean energy may assist in reducing carbon footprint in the world to create a green environment for sustainable living. The salinity gradient energy is one of the clean energies with the concept of mixing both salt concentration water from the ocean and fresh water from the river to create an osmotic pressure to power-up the generator for the production of electrical energy. Salinity different between the oceanic salt water and fresh water could produce an equilibrium osmotic pressure that achieve up to 27 bars equivalent from resulting pressure under the water for 200 to 300 meters. The potential of the power production through osmosis power generator is capture at the value of 2000 TWh per year, where in 2018 the world energy consumption was growing 2.3%, in which twice the number compare to the average rate of the growth. The major energy consumption is contributed from fossil fuel and consequently resulted from emissions of CO2 increased to 33.1 Gt to the atmosphere. This work explained the advantage of using salinity gradient energy and the fundamental principle of blue energy from pressure-retarded osmosis (PRO). Thus, the osmotic power by using different salinity gradient to create energy is widely known as blue energy, in which it is green and sustainable to produce electricity to the local communities

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació