Flood Tide Research Articles

Vulnerability and risk assessment mapping of Bhitarkanika national park, Odisha, India using machine-based embedded decision support system

The vulnerability and flood risk assessment of Bhitarkanika National Park in Odisha, India, was conducted using a data-driven approach and a machine-based embedded decision support system. The park, located in the estuaries of the Brahmani, Baitarani, Dharma, and Mahanadi river systems, is home to India’s second-largest mangrove environment and the world’s most active and diverse saline wetland. To evaluate its vulnerability and risk, various threats were considered, with a focus on floods. Satellite imageries, such as Landsat 8 OLI, SRTM digital elevation model, open street map, Google pro image, reference map, field survey, and other ancillary data, were utilized to develop vulnerability and risk indicators. These indicators were then reclassified into ‘Cost’ and ‘Benefit’ categories for better understanding. The factors were standardized using the max-min standardization method before being fed into the vulnerability and risk model. Initially, an analytical hierarchy approach was used to develop the model, which was later compared with machine learning algorithms (e.g., SVM) and uncertainty analysis indices (e.g., overall accuracy, kappa, map quality, etc.). The results showed that the SVM-RBF machine learning algorithm outperformed the traditional geostatistical model (AHP), with an overall accuracy of 99.54% for flood risk mapping compared to AHP’s 91.12%. The final output reveals that a large area of Bhitarkanika National park falls under high flood risk zone. The Eastern coastal regions of Govindapur, Kanhupur, Chinchri, Gobardhanpur and Barunei fall under high risk zone of tidal floods, The Northern and western regions of Ramachandrapur, Jaganathpur, Kamalpur, Subarnapur, Paramanandapur, etc., Fall under high risk region of riverine floods. The study also revealed that the areas covered with mangroves have a higher elevation and hence are repellent to any kind of flood. In the event of a flood high priority conservation measures should be taken along all high flood risk areas. This study is helpful for decision-making and carrying out programs for the conservation of natural resources and flood management in the national park and reserve forest for ecological sustainability to support sustainable development goals (e.g., SDGs-14, 15).

Mapping Socio-Economic Vulnerability to Rob Flood Hazards in Coastal Cities, North Pekalongan District, Pekalongan City

Climate change brings danger to several areas, especially in coastal urban areas. One of them is the tidal flood which experienced inundation. Tidal floods pose a serious threat to the sustainability of social life and economic growth. Assessment of social and economic vulnerabilities is needed to overcome the risk of disaster hazards due to climate change in the form of coastal tidal floods in cities. This research is expected to be able to describe socio-economic vulnerability through the variables of population density, age, gender, occupation, and level of education to tidal floods that have occurred in 42% of the area. The research method used is quantitative analysis, scoring, and geographic information system modeling with village analysis units. The results showed that Panjang Baru Village was the most vulnerable area because of the high density and low-income levels of the people, most of whom were fishermen and farmers households. It also indicates the contribution of population density, level of education, and employment to the level of vulnerability. This study states that the socio-economic aspect is an important factor that must be considered for the sustainability of life and community adaptation to the threat of climate change, especially tidal floods.

Flood Disaster Risk Reduction Strategies in Urban Area, Bulukumba Regency

Flood is a disaster that often occurs in big cities in Indonesia, caused by the high density of buildings and the unpreparedness of infrastructure to adapt. Urban Areas of Bulukumba Regency (UABR) is one of the centers of urban areas that has experienced flooding in recent years. The urban area ofBulukumba Regency is a downstream area of the Bialo Watershed whose upstream area is also in the Bantaeng Regency area. Rapid urban development has resulted in a change in land cover to become built-up land so that catchment areas are narrower in the middle and downstream zones, as well as changes in vegetation in the upstream zone which has received land conversion from forest areas to plantation areas. In addition to the potential for flooding due to river flow, the urban area of Bulukumba also has the potential for flooding due to sea tides or tidal floods. The high level of hazard flood potential has not been followed up with sustainable flood management based on disaster risk reduction in the UABR. Based on this, it is necessary to study the level of risk of flooding in the Urban Area of Bulukumba Regency and an appropriate strategy to reduce the risk of flooding in the Urban Area ofBulukumba. The aim of this research is; (1) identify the level of risk of flooding in the UABR; and (2) formulate an appropriate strategy as an effort to reduce the risk of flood disaster in the UABR. The research approach used is the mixed method, with the analytical method used for data processing in the form of risk analysis, spatial analysis namely overlay analysis using GIS software and qualitative descriptive in formulating strategies. The results of this study are a map of the level of flood disaster risk and recommendations for flood risk reduction strategies in the UABR.

Sea level rise already delays coastal commuters

Although the most dire societal impacts of sea-level rise (SLR) typically manifest toward the end of the 21st century, many coastal communities face challenges in the present due to recurrent tidal flooding. Few studies have documented transportation disruptions due to tidal flooding in the recent past. Here, we address this issue by combining home and work locations for approximately 500 million commuters in coastal US counties from 2002 to 2017. We find tidal flooding delays coastal commuters by approximately 22 min per year in 2015–2017, increasing to between 200 and 650 min by 2060 under various SLR scenarios. Adjustments in residential and work locations reduce the growth in commuting delays for approximately 40% of US counties. For residents in coastal counties, SLR is not a distant threat—it is already lapping at their toes.

Investigation of physical properties and suspended particulate matter discharge in a macrotidal estuary at the Amazon-semiarid transition zone

This study evaluated the hydrodynamic circulation and discharge of Suspended Particulate Matter (SPM) in the Arraial-São José Estuarine Complex (ASJEC) located at the Amazon-semiarid interface, northeastern Brazil. Quasi-synoptic data were collected in the rainy and dry seasons of 2017 under spring tide conditions. For each sampling event, two mooring stations (one downstream [S-A] and one upstream [S-B]) were deployed during a complete tidal cycle. The physical characteristics in the rainy and dry seasons enabled dividing the estuarine complex into zones, with a mixing zone/coastal zone interface and a tidal river zone/mixing zone interface. The estuary is vertically quasi-homogeneous, indicating conditions of high vertical instability. The currents at the stations were more intense during the flood tide, demonstrating the importance of the marine component in the region. The estuarine system ranged from partially mixed to well mixed at both stations in the rainy season and was well mixed at both stations in the dry season. Total salt transport was towards the upstream portion of the estuary, suggesting the accumulation of matter in the ASJEC, most likely associated with the entrance of marine waters. The input of coastal water in the ASJEC intensifies the baroclinic pressure gradient, which creates a hydraulic barrier, indicating that SPM discharges from the continental drainage to the estuary and is interrupted from the estuary to the adjacent continental shelf.

Rising seas and roadway debris: Microplastic and low-density tire wear particles in street-associated tidal floodwater

Tidal flooding is increasingly common in low-lying coastal regions as sea levels rise. This type of flooding can occur on sunny days with no rainfall and may transport street-associated debris, such as microplastics (MPs) including tire wear particles (TWPs), to coastal systems. This research aimed to quantify MP abundance in tidal floodwater and investigate their fate. Three locations around Charleston, SC (USA) were sampled during 12 tidal floods, and their adjacent tidal creeks were sampled before and after 5 floods. Floodwater contained an average of 342 ± 60 MP/L. Most MPs in floodwater were low-density TWP (86.5 %). MP abundance in tidal creek surface water following flooding did not change, suggesting that MPs were not immediately transferred to coastal waterways but deposited in adjacent marsh sediment. Elucidating transport routes of MPs in coastal environments is critical to understanding and preventing this type of contamination in the face of a changing climate.

Exploring the relationship between flood insurance claims, crowdsourced rainfall, and tide levels for coastal urban communities: Case study for the mid-Atlantic United States

The Federal Emergency Management Agency (FEMA) recently released a large dataset (∼2.5 million records) of flood insurance claim transactions from the National Flood Insurance Program (NFIP) that are geolocated by census tract. In this study, we present a methodology for using these NFIP flood claims along with agency rainfall and tide level data, combined with high-resolution rainfall data collected from growing networks of crowdsourced Personal Weather Stations (PWSs), to investigate the characteristics of storm events that result in flood insurance claims. Using 25 cities/counties in five metropolitan areas in the Mid-Atlantic region as case studies for testing the methodology, we find that the majority of flood claim events in this region were associated with rainfall below a 1-year return period and a tide level below the NOAA minor flood risk tide level. When storm events exceeded these rainfall and tide thresholds, the probability of a flood claim occurring could reach 100% for rainfall only events and 33% for tidal only events, depending on the region. While compound events of both high rainfall and high tide were rare, when seen in Virginia Beach, the probability of insurance claims being made during these events far exceeded the probability that would be expected if rainfall and tide were independent, showing how compound events in this region exacerbate flood impacts. Additionally, analysis of 110 heavy rainfall events showed that crowdsourced PWSs, can better capture rainfall extremes associated with insurance claims due to their higher spatial density compared to federal agency rainfall networks. This suggests that the PWS networks, once quality controlled, can offer greater insights into which rainfall events are likely to contribute to insurance claims. These region-specific findings and the general methodology presented in this study can benefit multiple stakeholders including researchers, risk management officials, insurers as well as the general public in understanding the impacts of rainfall, tidal, and compound flooding, along with the value of crowdsourced data in assessing flood risk.

Coastal Vulnerability Classification of the North Coast of Java using K-Nearest Neighbor

Indonesia has many beaches that attract the attention of tourists, including the north coast of Java. In addition to visual appeal, there are also other potentials such as settlements, agriculture, fisheries, ports, ponds, and other resources. However, there is also a threat to coastal damage caused by, among other things, wave action, tides, abrasion, and tidal flooding. For this reason, in developing coastal areas on the north coast of Java, it is necessary to consider the potential for damage to the coast based on the physical condition of the coast and a system that can classify the vulnerability levels of coastal areas is also needed. The Coastal Vulnerability Index (CVI) can be determined and classified using for example the Gornitz formula, or using data driven model and machine learning based on the coastal parameter data. This study demonstrates how the K-Nearest Neighbor, also known as K-NN algorithm, can be used to classify the level of vulnerability of the coastal areas. This study uses 290 points (locations) along the northern coasts of Java. The parameters that determine the coastal vulnerability are mean sea level (MSL), mean significant wave height (MSWH), mean tidal range (MTR), shoreline changes, landforms and slopes. In this study, the classification of coastal vulnerability levels is classified into 4, namely “low, moderate, high and very high”. The K-NN system uses 80% of the data for training and 20% for testing, with the value of K = 1 to 10. The test results show that the K-NN method is capable of classifying the vulnerability levels of the North Coast of Java. From the test results for values of K = 1 to K = 10, and by randomizing the training data and test data gives an average accuracy rate of 86.21% to 97.13%, with the best K value obtained at K = 2.

Tidal effects on carbon dioxide emission dynamics in intertidal wetland sediments

Understanding the control mechanisms of carbon dioxide (CO2) emissions in intertidal wetland sediments is beneficial for the concern of global carbon biogeochemistry and climate change. Nevertheless, multiple controls on CO2 emissions from intertidal wetland sediments to the atmosphere still need to be clarified. This study investigated the effect of tidal action on CO2 emissions from salt marsh sediments covered by Spartina alterniflora in the Jiaozhou Bay wetland using the static chamber method combined with an infrared CO2 detector. The results showed that the CO2 emission fluxes from the sediment during ebb tides were higher than those during flood tides. The whole wetland sediment acted as a weak source of atmospheric CO2 (average flux: 24.44 ± 16.80 mg C m−2 h−1) compared to terrestrial soils and was affected by the cycle of seawater inundation and exposure. The tidal influence on vertical dissolved inorganic carbon (DIC) transport in the sediment was also quantitated using a two-end member mixing model. The surface sediment layer (5–15 cm) with maximum DIC concentration during ebb tides became the one with minimum DIC concentration during flood tides, indicating the DIC transport from the surface sediment to seawater. Furthermore, aerobic respiration by microorganisms was the primary process of CO2 production in the sediment according to 16 S rDNA sequencing analysis. This study revealed the strong impact of tidal action on CO2 emissions from the wetland sediment and provided insights into the source-sink pattern of CO2 and DIC at the land-ocean interface.

Analisis Optimalisasi Ketahanan Daerah Berbasis GIS, Remote Sensing dan Cloud untuk Manajemen Banjir dan Rob di Kota Semarang

Abstract. Floods and tidal floods are a topic of discussion every year in the city of Semarang because no proper solution has been created for mitigation. From January 2022-May 2023, most of the flood and rob events are located in flat and sloping areas. The disaster had an impact on human life, such as material, physical, economic, and psychological losses. Importance of innovation to create flood resilience is urgently needed to eliminate or minimize the adverse effects of floods and rob. Flood resilience analysis uses a spatial approach supported by GIS optimization, Remote Sensing, and the Cloud platform. Then the model builder is used to speed up and simplify the analysis process. The results of the analysis show that the highest level of flood sensitivity is in flat and gently sloping areas with high population density & buildings. Meanwhile, high capacity levels are in areas close to health facilities, have road accessibility, and have lots of economic activity. In addition, 93.37% of the area's resistance to flooding is still classified as low and medium. This should be of particular concern for areas with dense populations and buildings, such as Pedurungan District, Ngaliyan District, North Semarang District, West Semarang District, and Genuk District. Thus, through regional resilience mapping, it can become a basis for decision-making for local governments with the support of inclusive disaster management.

Return Level Estimation in Spatial Extreme Value Modeling of Bali Sea Currents Velocity using The Smith and Brown-Resnick Max-Stable Process Approach

Bali is the world's second most popular tourist destination in 2023. One of the best tourisms is the beauty of its coasts. Even though it is the best tourism destination, it is not uncommon for disasters to occur in the coastal areas of Bali. One important factor in the occurrence of coastal disasters from waters such as tidal flooding and abrasion is ocean currents. Spatial analysis of sea currents velocity was carried out using the Smith and Brown-Resnick Max-Stable Process Approach. The purpose of this study was to determine parameter estimation and comparison of the results of Spatial Extreme Value modeling with the Smith and Brown-Resnick Max-Stable Process approach, and to determine the Return Level of Bali Sea current velocity for the same period after data testing with the best model. The data used is daily data for the period March 2, 2017 to December 30, 2020. Extreme data selection with Block Maxima uses 14 daily blocks, so there are 100 blocks for each water location. The proportion of training and testing data is 80:20. The training data follows the Generalized Extreme Value distribution and has no pattern trend (stationary). The results of the extremal coefficient measurements ranged from 1.18604 to 1.59485 indicating a fairly strong dependency between locations. The best trend surface model is a model that only has longitude coordinates on the location parameter and latitude on the scale parameter. The estimated value of the spatial parameters of the Smith model tends to be greater than that of the Brown-Resnick model. The Root Mean Square Error and Mean Absolute Percentage Error for the Smith model are 0.15503 and 7.75076%. Meanwhile, the Brown-Resnick model is 0.29576 and 14.12131%. Return Level values for the same period after data testing are classified as strong currents and are respectively 1.20586 m/s, 1.63592 m/s, 1.51322 m/s and 2.13233 m/s for Serangan, Gianyar, Nusa Dua, and Nusa Lembongan Waters. Information on estimated Return Levels is expected to be a consideration that can be used by related agencies such as the Coastal and Marine Resources Management Agency (BPSPL) and the Bali Province Regional Disaster Management Agency (BPBD) as a coastal disaster mitigation effort to make it more effective, efficient and on target.

Sex-specific foraging behaviour in a long-lived seabird

Sex-specific foraging behaviour may lead to differences between the sexes in both resource acquisition and exposure to threats and thereby contribute to sex-specific reproductive roles or mortality. As such, it is important to identify in which species sex-specific foraging behaviour occurs. We deployed GPS devices to incubating common terns (Sterna hirundo) from a German breeding population to study how sex and spatial or temporal extrinsic factors influence the daily activity budget, foraging distribution, and trip characteristics of this slightly sexually size dimorphic seabird. Birds of both sexes only foraged during the day, showing peaks of activity after sunrise and before sunset, perhaps in response to temporal variation in prey availability and/or as a strategy to overcome or prepare for nocturnal fasting. Furthermore, foraging was more frequent around low tide and at the beginning of the flood tide and mainly occurred in shallow (< 5 m depth) and coastal waters (< 2 km from coastline) up to 20 km from the colony. Females rested less, foraged closer to the colony in more coastal waters, and showed a lower maximum flight speed than males. Males foraged more outside protected areas than females and showed higher variability in their foraging distribution throughout the tide cycle. As such, our study provides evidence for sex-specific aspects of foraging behaviour in common terns and underlines the importance of considering sex-specific foraging distributions when assessing the impact of at-sea threats on seabirds, knowledge of which should be incorporated when developing conservation management strategies.

Experimental flow conditions effects on a bottom-mounted ducted twin vertical axis tidal turbine compared to real sea conditions

From 2019 to 2021, HydroQuest tested its 1 MW-rated ducted twin vertical axis tidal turbine (2-VATT) at Paimpol-Bréhat test site, France. At this site, the turbulent intensity is evaluated about 15 % and extreme wave conditions up to 6 m significant wave height with 12 s peak period were observed during the two years of demonstration. In addition, the current vertical velocity profile is sheared with about 20 % velocity difference between the top and the bottom of the turbine, and the average directions of the ebb and flood tides are about 22° asymmetrical. The bottom mounted 2-VATT was instrumented for performance and loads assessment which allowed the certification of the power curve, both in flood and ebb tides, as well as the analysis of the sea state influence on the turbine behaviour. Based on that experience, the company wants to gain confidence in its design process by comparing those results to numerical and lab-scale experiments ones.&#x0D; Along the past three years, an important amount of work has been achieved to widely characterise the behaviour of the 1/20 scale 2-VATT similar to the 1MW-rated demonstrator. The turbine was tested in many different operating conditions in the Ifremer’s wave and current flume tank to try to reproduce full-scale conditions and turbine response. Those conditions include a wide range of operating points and incident velocities, facing aligned and misaligned currents, with and without vertical velocity shear, with and without bathymetry generated turbulence, with and without surface waves following and against the current. In this presentation, we propose to synthesise the effects of all these conditions on the 2-VATT response to highlight the most critical ones in the design process of such a device, in comparison to the results obtained at sea.&#x0D; To this date, we showed that the lab-scale model behaviour differs between ebb and flood tide current conditions due to the difference of relative counter-rotation of the two columns of rotors and to the base asymmetry. The wake is also significantly different as it recovers 30 % faster in the flood tide configuration compared to the ebb. We also found that the presence of a sheared and misaligned incident current barely affects the ducted 2-VATT average performance. However, it modifies the torque repartition between the rotors leading to an increase of the power fluctuations. Furthermore, when adding bathymetry obstacle upstream, the high flow shear and turbulence also generate strong power fluctuations on the 2-VATT. The load fluctuations are significantly increased, impacting the structure fatigue compared to a flat floor configuration, but the risks of device drifting or toppling are not affected. The waves impact the power and loads fluctuations too while barely affecting the average performance; and the average performance increases with the Reynolds number in the tank. Those two latter points still need investigations to better characterise their effect on the 2-VATT.

Measurements of the wake from a floating tidal energy platform

Wake measurements are critical for quantifying the hydrodynamic impacts of turbine presence and tidal energy extraction on the tidal flow. Turbine wakes are typically assessed using numerical models and controlled laboratory experiments, with only a few field studies available for the wakes of full-scale operating tidal turbines. In this investigation we present field observations of the combined wake generated by the four-turbine array mounted onboard Sustainable Marine Energy Canada PLAT-I 4.63. Measurements were conducted downstream of the platform in Grand Passage, a tidal channel in the southwest of the Bay of Fundy in eastern Canada in October 2020. Velocity data were obtained by a suite of mobile Acoustic Doppler Current Profilers (ADCP), both vessel-mounted and free-drifting. Data were collected during ebb and flood tides (and therefore with time-varying inflow velocity), and under different turbine operating conditions. The collected data were organized according to the turbine inflow velocity for ebb and flood tide. For each tide, the wake and undisturbed flow regions to the sides of the wake were identified. Vertical profiles of velocity in the wake were compared to inflow velocity measured by a current-meter onboard PLAT-I and with measurements in the undisturbed flow to the sides of PLAT-I wake. In all measurements the PLAT-I wake manifests as a reduction in flow speed at the depths spanned by the turbine rotors. The reduction is maximum near the platform for both ebb and flood. For flood, velocity profiles vertically mix less than 5 effective diameters downstream of the array, but velocities remain slower compared to the flow outside of the wake. Flow speed increases downstream, recovering approximately about 20 effective diameters from the platform. For ebb, the velocity reduction persists farther downstream compared to flood, there is less vertical mixing, and the wake shape is still present beyond 10 effective diameters downstream of the platform. Increased turbulence is also observed downstream of the platform, which recovers to levels similar to those of the surrounding undisturbed flow about 10 effective diameters downstream of the turbine for both ebb and flood. Comparisons of results between the two measurements approaches, and between the wake of clean and bio-fouled turbines are also explored.

High-fidelity modelling of a six-turbine tidal array in the Shetlands

Micro-siting tidal stream turbines in a confined seabed area requires a extensive understanding of the flow dynamics over the water column at turbine deployment locations so that operating conditions are assessed, wake effects can be estimated to infer the energy yield [1], or bathymetry effects can be quantified. Tidal currents have the advantage of being highly predictable and mostly bidirectional but the uneven bathymetry found at most of sites introduces a high variability to the flow conditions within relatively short distances. Considering future tidal turbine arrays will comprise dozens of devices, deploying ADCPs at each turbine position would be very expensive or very time consuming, outlining the need for accurate modelling tools to be used as digital twins in micro-siting. Shallow-water models are widely adopted in preliminary design of tidal arrays but fail to capture the three dimensional nature of the flow and predict deflected wakes whose streamwise length is also over-predicted [2]. Thus, eddy-resolving method are required to fully capture the turbulence from the free-stream flow, induced by turbines and from bathymetry. \\&#x0D; This study provides a real-project application of the state-of-the-art large-eddy simulation (LES) code DOFAS (Digital Offshore Farms Simulator) [3] to the six 100kW-turbine array deployed by NOVA Innovation Ltd. in the Shetlands, UK [4]. The bathymetry data has been obtained from EMODnet database with the velocity profiles set at the inlet condition of both ebb and flood tides imported from Macleod et al. (2019) [4]. The deployment site is characterised by steep slopes with a maximum depth of 45 m at the cross-section where turbines are located. The bathymetry has a downwards slope when the flow goes in the ebb tide direction whilst upstream during flood tide. The tidal rose indicated a slight deviation of about 20$^{\circ}$ between ebb and flood directions. The turbines have a diameter ($D$) of 9 m attached to a 10 m long hub whose diameter is 1 m. Three array configurations have been studied: (i) single row of three turbines, (ii) two rows of turbines spaced 8$D$, and (iii) two rows of turbines spaced 12$D$. The computational domain extends over 600 m by 300 m in the horizontal plane yielding 540 million cells, requiring 32,500 CPU hours to compute 30 min of physical time.\\&#x0D; Results show that bathymetry effects at this site play a larger role when designing the location of the secondary row of turbines compared to wake effects from upstream turbines. During the ebb tide, the increase in water depth reduces the wake recovery far downstream so that the array with 12$D$ row spacing has a lower performance than the 8$D$ one with approx. 30\% decrease in energy yield. Conversely, the uphill shape of the bathymetry during the flood enables a fast wake recovery so that the downstream row experiences almost no energy yield loss due to wakes.

Measurements of tidal flow variability in Ramsey Sound, Pembrokeshire

The nature of the flow at in-stream tidal energy sites is particularly important for predicting array and device performance, and also for operations and maintenance planning. Previous developers have reported issues such as the choice of vessel, cost of operations, and the limits of operation of deployment vessels. The dynamics of the flow around slack water has been of particular interest at Ramsey Sound in Pembrokeshire (UK) for planning the recovery of an existing turbine, the Tidal Energy Limited ‘Deltastream’.&#x0D; This research presents flow characteristics of Ramsey Sound, based on analysis of Acoustic Doppler Current Profiler (ADCP) measurements and tide gauge data from the nearby Standard Port of Milford Haven. The ADCP was located approximately 300 m across the channel, at the northern end of the channel, where the channel width was 1200 m and the mean depth was approximately 33 m. The flow dynamics were examined specifically to look at times potentially suitable for offshore operations Two weeks of data were used in the analysis, spanning a complete spring-neap cycle.&#x0D; Results demonstrate that flow velocities exhibited clear asymmetry, with stronger flows on the northerly directed flood tide than on the ebb. There was considerable variation in the measured current speed around the time of the maximum, suggesting large scale bed feature generated turbulence. The flood (northerly) current maximum was approximately in phase with high water at Milford Haven. Cross correlation indicated that the flow generally led the elevation by 20 minutes. In contrast to the expected theory, the current strength at mid-depth was stronger than at the surface on the maximum flood tide. The maximum flow speed in the tide was reasonably predictable from the tide range at Milford. A threshold-based analysis of the ADCP measurements allowed the duration of slow-moving water to be identified for operation planning.&#x0D; Operations and planning in light of sound understanding of hydrodynamics at tidal energy sites is critical for future economic success of the tidal energy sector. The results shown here from an ADCP deployment in Ramsey Sound have shown the capability to give useful tools for planning recovery operations.

High-fidelity modeling of a vertical axis tidal turbine model under realistic flow conditions

In the context of the global energy crisis, developing renewable energies is of primal importance. Among the renewable resources available are tidal currents. Tidal currents can be exploited with tidal turbines. Different concepts of tidal turbine exist, we here investigate a vertical axis tidal turbine or VATT prototype made by HydroQuest and CMN. More precisely, we carry on numerical investigations on a Hydroquest/CMN tidal turbine model. Experimental studies are limited to turbine models and thus suffer from scale effects. In situ measurement are still expensive and difficult to acquire. Computational Fluid Dynamics (CFD) is an interesting alternative in order to go beyond what experiments can offer. One major drawback of CFD is that it requires validation of the models used. A validation of our CFD tool is included in this paper. Because the hydrodynamic of vertical axis tidal turbines is highly unsteady, Large Eddy Simulation (LES) are well adapted here. Blade-resolved Computational Fluid Dynamics (CFD) approaches are appropriate to study vertical axis tidal turbines, but their cost is still prohibitive for real size tidal turbine. Simplified approaches are preferred solutions. Literature showed that Actuator Line Model (ALM) LES is well suited to model vertical axis turbine. Most tidal sites are characterized with strong turbulence intensities. The presence of turbulence in most tidal sites has led companies and academics to study the effects of ambient turbulence over tidal turbines. It has been shown that turbulence can have a non-negligible influence on the turbine performances and wake. To account for the effects of turbulence, synthetic turbulence is introduced at the inlet of the simulation. The LBM is an unsteady weakly-compressible CFD approach. It solves the Boltzmann equation using an explicit time discretization and a uniform Cartesian grid called lattice. It has been proven to be an efficient approach for modeling tidal turbines using LES and ALM, Grondeau et al. (2019). In this paper, we study a tidal turbine model of the Hydroquest/CMN VATT using an ALM-LBM-LES approach. This model was tested at the Ifremer Boulogne-sur-Mer testing facilities. We first compare our results with the experimental ones in a scenario without turbulence and for flood and ebb tide configurations. A numerical investigation of the influence of upstream turbulence on the turbine performances and wake is then realized. Prospects of this study include among others the effects of turbines interactions and waves.

Wake characterization of tidal turbines in the Pentland Firth using vessel-mounted ADCP measurements

Knowledge of the extension and velocity deficit induced by tidal turbine wakes is crucial for the optimization of tidal farm layouts, as the wake induced by an upstream turbine may substantially affect the power and loadings of a device located downstream. The MeyGen project is the largest planned tidal stream energy project in the world: it aims to develop up to 398 MW of installed power in the Pentland Firth, Scotland, a site with current velocities reaching up to 5 m/s. During Phase 1 of the project, four 1.5 MW turbines were installed, providing a valuable opportunity to investigate turbine wake dynamics in full scale. As part of Phase 2, site characterization campaigns were carried out to plan the deployment of additional turbines, representing 28 MW of tidal power capacity. Hence, the influence of the existing devices on the downstream flow was investigated.&#x0D; This work introduces the method used for studying wakes downstream tidal turbines using vessel-mounted Acoustic Doppler Current Profiles (ADCP) measurements. During two spring tides, the data was collected using an ADCP Teledyne Workhorse 600 kHz configured for along-beam velocities recording with 1 m resolution, as well as a GNSS Hemisphere Vector V102. The aim of this study was to map the flow downstream the turbines already installed on site, in order to identify and characterize the wake. Cross-flow transect measurements were conducted at various along-flow distances downstream from the devices, and repeated several times for improved accuracy. The cycles of repeated transects were performed both at flood and ebb tides, with the turbine running or switched off to spot potential differences introduced by device operation. Mean flow velocity estimates in the cross-section were obtained from raw data using the location-based velocity solver developed by Vermeulen et al. (2014). The method provides improved flow velocity estimates from vessel-mounted ADCP measurements because it strongly reduces the spatial extent over which flow homogeneity must be assumed, thus decreasing the chances that this assumption will fail. The reduction of the volume across which homogeneity must be achieved may represent a significant advantage for the investigation of tidal turbine wakes. To the authors’ knowledge, this is the first time that this method has been applied to wake characterization in a tidal stream energy site.&#x0D; Outputs of the analysis include mean velocity magnitude and direction, as well as velocity deficits associated with the wakes. The mean velocity estimates obtained in each cross-section are compared for cases when the turbine was running or switched off. Findings reveal that vessel-mounted ADCP transects, coupled with the location-based methodology for velocity estimation, provide a powerful tool for tidal turbine wake characterization. The final presentation and paper will provide the results of this study.&#x0D;

Reconstruction of digital teaching materials with Socio-Scientific Issues (SSI) context on newton’s gravity-tidal flood content

This research is motivated by the frequent emergence of news regarding the issue of tidal floods that occur due to a lunar eclipse, which is related to Newton’s law of gravity. On the other hand, it is known from the 2018 PISA results that, in general, students’ scientific literacy in Indonesia is low. One of the efforts to increase students’ scientific literacy is to provide teaching materials in the context of socio-scientific issues (SSI). This study aimed to determine the results of the reconstruction, assessment, and students’ responses to teaching materials with the SSI context on Newton’s Gravity-Tidal Flood content. This research was conducted by Research and Development (R&D) method, by design is ADDIE. This research has succeeded in reconstructing digital teaching materials with the SSI context on Newtonian gravity-tidal floods, which consists of four sub-chapters. Teaching materials are evaluated in 2 ways: validity based on general criteria and validity based on Badan Nasional Standarisasi Pendidikan (BNSP) criteria. The assessment score is 89.50%, showing that the material teaching materials are feasible and meet the requirements for the physics learning process. Student response score of 87.79% indicates that the teaching materials with the SSI context on Newton’s gravity-tidal flood material have been understood and meet student learning expectations. The book “Newton’s Gravity & Tidal Flood Based on Socioscitific Issue” can be accessed at https://online.fliphtml5.com/mcvyo/tvnu/#p=1.

Performance of Asphalt Wearing Course against the Immersion Effect of Tidal Flood (Rob) with Added Materials Polyethylene and Fine Aggregate Slag

Performance of Asphalt Wearing Course against the Immersion Effect of Tidal Flood (Rob) with Added Materials Polyethylene and Fine Aggregate Slag