Low Tide Level Research Articles

Study of the effect of spur dikes on beach protection based on physical model experiment

The Qiantang River is a typical strong tide estuary, the world-famous tidal bore have huge turbulent energy and causes damage to the sea wall. Spur dike is an important engineering to prevent the seawall foundation from tidal bore. But the tidal bore occurs at the low tide level, strong turbulence, high flow velocity, water level rises sharply. The spur dike height, length, inclination angle need to be determined by physical model according to the specific bore dynamic conditions. In the tests, the fixed-bed model was used to study the tidal current velocity reduction rate and region, the falling current circulation characteristics in dike field. The movable-bed model test is used to study the effect of each test on protecting the beach. This physical model study reveals the rule of spur dike influence on tidal bore dynamics so the effect of spur dike on protecting the beach is clear.

The Responses of Storm Surges to Representative Typhoons under Wave–Current Interaction in the Yangtze River Estuary

Storm surge is one of the most remarkable natural calamities, which is shown as the abnormal sea level changes in the coastal waters during a typhoon event. To investigate the responses of storm surges to the typhoon paths, intensities and coastal dynamics, a coupled wave–current model is used to study the impacts of strong winds, considerable waves and complex currents on storm surges in the Yangtze River Estuary (YRE) during three representative typhoons of Fongwong (2014), Ampil (2018) and Lekima (2019) with different intensities and paths. The model is verified using the measured data on significant wave height and period, water level and current velocity and performs well in modeling real conditions. The numerical results demonstrate that (1) the maximum storm surge occurred in the South Channel (SC) during Fongwong and Lekima while in the North Branch (NB) during Ampil due to the typhoon path and the estuarine terrain. Among the three typhoons, Lekima presented the highest surge, with a maximum value of 1.17 m at SC2 (the inner point of the SC). There was a negative surge during Ampil, which reached −0.42 m at SC2, due to the representative path (SE to NW) and offshore wind action. (2) Tide is the main influencing factor of storm surge as the maximum or minimum value always occurs at the low or high tidal level, respectively. Meanwhile, typhoon intensity is important as it influences the variation rate of surge with higher intensity leading to a sudden increase in surge while the tidal intensity primarily affects the peak value. (3) The wave setup can counteract the wind-induced negative surge. The peak differences between storm surge isoline and wave setup isoline are 0.15, 0.2 and 0.2 m during Fongwong, Ampil and Lekima, respectively, which illustrates the impacts of the combined actions of the typhoon path and intensity on the wave setup. This research emphasizes the influences of wave–current interaction on estuarine storm surge during typhoon events and reveals the potential risks for oceanic disasters like coastal inundation.

Seasonal Water Level Variations and Predictive Modeling in Kampung Parit Hylam, Johor

This study aimed to assess seasonal water level variations and their impacts in Kampung Parit Hylam, located on the West Coast of Johor. The research focused on the distinct effects of the Southwest Monsoon (April-September) dry season and the Northeast Monsoon (October-March) wet season. The study quantified water level variations across seasons by analyzing historical tidal records, weather data, and earth-level measurements. Using Minitab software, the project predicted short-term water level changes over 3, 6, and 9 months, based on historical trends and future climate scenarios. The Winter Multiplicative Method model, with a MAPE of 6% for low tides and 0% for high tides, was selected for its accuracy and ability to capture seasonal patterns. For March, June, and September 2024, actual low tide levels were 0.60 m, 0.00 m, and 0.60 m, respectively, while forecasted levels were 0.67 m, 0.68 m, and 0.54 m, with a 95% PI ranging from 0.60 m to 0.80 m, closely matching the actual values. Similarly, actual high tide levels were 2.60 m, 2.30 m, and 2.60 m, with forecasted levels at 2.67 m, 2.72 m, and 2.68 m, with a 95% PI of 2.60 m to 2.70 m, accurately covering the actual levels. These levels were significantly below the minimum bund height of 4 m, indicating effective protection. Additionally, the study evaluated the effectiveness of existing bunds in mitigating water level rise and structural vulnerability. The findings aimed to provide accurate water level forecasts, support effective water resource management, and offer recommendations for enhancing bund design and maintenance. This comprehensive analysis was intended to aid local authorities and the community in planning and preparing for the impacts of seasonal water level fluctuations.

Growth, survival, and morphometric relationships of Crassostrea corteziensis cultivated during the nursery stage in oyster bags at different tidal levels, in Boca de Camichín, Nayarit, Mexico

The optimal tide height at which the intertidal oyster bed system (IOBS) should be installed to cultivate Crassostrea corteziensis in Boca de Camichín (BC), Nayarit, Mexico, during the intermediate grow-out stage (39.3–60.2 mm in shell length) was determined. Temperature, salinity, chlorophyll a (Chla), and turbidity were recorded 3 times a day. A trophic state index (TSI) was calculated with Chla and turbidity data. Three treatments corresponding to tide levels were tested: (1) high level (14 cm above mean sea level [MSL], emersion time [ET] = 56.4% of the total duration of the experiment), (2) intermediate level (MSL, ET = 48.6%), and (3) low level (41 cm below MSL, ET = 32.1%). Gross growth rates and absolute and relative monthly growth rates were calculated to identify periods with highest growth relative to environmental conditions. Finally, the effect of the treatments on the dimensions and weight of the oysters was studied. The results indicate that BC water was mesotrophic in April–June and eutrophic in July–August. The low tide level was the best for IOBS operation, with growth rates of 0.15, 0.10, and 0.07 mm·d–1 in shell length, width, and thickness, respectively, and 0.204 g·d–1 wet weight. Cumulative mortality was lower in the low (18.5%) and intermediate (16.4%) treatments. Shell thickness was significant reduced (P < 0.05) in the high treatment and total wet weight was reduced in the high and intermediate treatments. The results of this study offer a viable and different alternative to the cultivation of C. corteziensis in strings that is currently carried out in Boca de Camichín, Nayarit, Mexico.

Yesterday's High Tide Is Today's New Normal

AbstractThe daily rise and fall of the tides are intimately familiar to those living on the coast. However, due to sea‐level rise, what communities in the United States now experience as the highest, lowest, and average water levels on a typical day no longer corresponds to the official definitions of high tide, low tide, and mean sea level, respectively. Water levels now regularly exceed official high tide along parts of the Chesapeake Bay, Gulf Coast, and Puerto Rico. In other words, yesterday's high tide is becoming today's new normal. This demonstrates how sea‐level rise is radically redefining the American shore.

ANALISIS PENGARUH PERUBAHAN PERMENDAGRI NO. 76 TAHUN 2012 MENJADI PERMENDAGRI NO. 141 TAHUN 2017 PADA DATUM VERTIKAL DALAM PENETAPAN BATAS WILAYAH LAUT DAERAH

A boundary is a mark that separates adjacent geographical areas and serves as a separator for the authority to manage government administration between regions and can be found on land and sea areas. Various regulations have been made by the Indonesian government to regulate regional boundaries including maritime boundaries, including Permendagri No. 76/2012 which was later amended to Permendagri No. 141/2017. This change is motivated by the fact that Permendagri No. 76/2012 is considered not in accordance with the development of the situation, so it needs to be replaced with a new ministerial regulation. One of the differences in the two Ministerial Regulations is the difference in vertical datum or height reference at the base point used as a reference for drawing the shoreline. According to Permendagri No. 76/2012, the shoreline drawing reference uses the lowest low tide level, while Permendagri No. 141/2017 uses a reference at the highest tide level. This research aims to determine the effect of vertical datum on shoreline changes in the affirmation of marine boundaries through literature study and spatial analysis. The results of this study indicate that changes in vertical datum have an influence on shoreline shifts which are also influenced by the slope of the coastal slope, shoreline shifts that drift towards the mainland cause a reduction in the area and management of regional seas.Keywords: Analysis, Maritime Boundary, Regional Boundary, Slope, Vertical Datum

A Study on Spatial Distribution Extraction of Tidal Inundated Mangroves Based on High and Low Tide Level Images

A majority of mangroves are located in the coastal intertidal zone and are subject to tidal periodic inundation. However, the previous vegetation indices used for extracting the spatial distribution of mangroves were not able to effectively extract submerged mangroves, and the applicability of the vegetation indices used on different spatial resolution images obtained from different sensors was not verified. In this study, a new vegetation index, namely the intertidal mangrove identification indices (IMIIs), was proposed, based on GF-2 images of high and low tide levels. Meanwhile, other commonly used vegetation indices were also extracted. All the vegetation indices were used to extract the spatial distribution of mangroves under tidal inundation, and applicability tests of the vegetation indices were conducted on Sentinel-2 images in three different regions. It was found that the IMIIs proposed based on GF-2 images of high and low tide levels can extract submerged mangroves relatively well, and the spatial distribution extraction results of mangroves are better than those of other vegetation indices, with IMII2 outperforming IMII1. At the same time, IMIIs have good applicability in medium resolution Sentinel-2 images, and there are relatively large differences in the extraction results of mangrove spatial distribution among different vegetation indices in areas with significant impact of tidal inundation. Among all vegetation indices, the extraction results of IMIIs are relatively superior. In most cases, multi variables collaborative application can improve the accuracy of mangrove spatial distribution extraction results. Based on the results of this study, it was concluded that the IMIIs proposed in this study can accurately extract the spatial distribution of mangroves inundated by tides from both medium- and high-resolution images, providing accurate basic data for effective management and scientific protection of mangrove resources.

Effect of Tide Level Change on Typhoon Waves in the Taiwan Strait and Its Adjacent Waters

In recent years, most research on typhoons in the Taiwan Strait and its adjacent waters has focused on simulating typhoon waves under the influence of wind fields. In order to study the influence of tidal level changes on typhoon waves, a numerical model was established in the Taiwan Strait based on the third-generation ocean wave model SWAN. The simulation results of the tide level during the corresponding typhoon landing time were incorporated into the model to optimize its performance. Subsequently, the wave height of the typhoon landing at the lowest tide level was compared with that at the highest tide level. This comparison serves as a reference and warning for ocean engineering, highlighting the hazards of the typhoon landing at high tide. The simulation results were verified and analyzed using the measured data of significant wave heights and wind speeds when typhoons Mekkhala (2006) and Maria (0607) approached. The results show that after optimization, the relative error of the significant wave peak is reduced. Furthermore, there has been a decrease in the maximum wind speed, bringing it closer to the measured value. These improvements signify enhanced model accuracy. The tide level has a great influence on the typhoon wave, and the tide level height at the time of the typhoon landing is positively correlated with the significant wave height of the waves generated by the typhoon. When the typhoon’s landing time coincides with the high tide level, the resulting waves are significantly higher, reaching up to 0.71 m. This has a substantial impact on the safety of marine structures, particularly breakwaters.

Experimental Investigation of Infragravity Wave Propagation on a Porous Reef

A laboratory experiment is carried out to study the generation mechanism and the evolution process of an infragravity wave (IG wave) on a typical permeable fringing reef. Fifteen capacitance wave gauges are installed along the reef model to record the water surface elevation under irregular wave action. Based on the experimental data, both IG wave generation and strong IG wave interaction are systematically analyzed. The experimental results indicate that the IG waves are generated by the time-varying breakpoint mechanism at the reef edge, and the tidal modulations on the IG wave height are mainly influenced by wave breaking and wave dissipation. Around the reef edge, the tidal modulation is controlled by wave breaking and the IG wave height monotonously decreases with the increase of the tide level. At the shoreline, the tidal modulation is controlled by wave dissipation at the low tide level and wave breaking at the high tide level. Therefore, the IG wave height first increases and then decreases with the increase of the tide level, and the maximum IG wave height occurs at the middle tide level.

Spatio-Temporal Variability of Wrack Along the Northern Portuguese Sandy Beaches

Wrack accumulations are a source of nutrients on sandy beaches and host invertebrate species, increasing local biodiversity. The distribution of these important accumulations varies in space and time depending on the environmental conditions and the composition of species that are in the wrack. Species composition and spatiotemporal variability in wrack accumulations remain poorly understood in some regions. In this study, we evaluated the spatiotemporal variability in wrack biomass and diversity on four sandy beaches in northern Portugal over the course of 1 year. The results revealed that both the diversity and biomass of wrack varied temporally depending on the beach and tidal level where it was collected. Wrack biomass was about 20 to 35 times greater at higher than at the low tide level and was more abundant (87%) and twice as diverse at the two northernmost beaches of the study, probably due to a greater proximity to rocky shores. Large brown temperate and boreal macroalgae species such as fucoids (Fucus spp., Cystoseira spp., and Ascophyllum nodosum) and the kelp Saccorhiza polyschides were the most abundant taxa in the wrack. Fucoids were in the wrack throughout the year, while kelps predominated in the warmer months, generating 8% more biomass than that produced by fucoids throughout the year. However, since large brown macroalgae species are reducing their size and recruitment due to global warming in the north of the Iberian Peninsula, the biomass and diversity of wrack in northern Portugal could be limited in the future, compromising crucial functions of wrack in ecosystems.

Measures for mitigating the shrinking of the North Branch of Changjiang Estuary

The atrophy of the entrance channel in the North Branch of Changjiang Estuary and the sediment supplied by landward tidal flow from the sea to the branch, threaten the sustainable use of the numerous ports and wharves along the riversides. Four different plans of two groups to mitigate the shrinking of the North Branch were proposed and tested. The plans in the first group aimed to expand the entrance channel and the upper section of the North Branch through dredging. The purpose of the plans in the second group was to reduce the landward tidal volume in the lower section of the North Branch to reduce the sediment import from the sea. The effects of these plans were simulated by a 2D computational hydrodynamic model, and the results such as tidal volume at different sections, the portions of tidal volume in different branches, and the high and low tidal levels at the monitoring points, were obtained and compared. After that, one plan from each group was recommended. The measures of the recommended plans have been mostly adopted in the report of Revision of the Comprehensive Regulation and Development Plan of the Changjiang Estuary.

Water Quality Analysis and Pollution Load Capacity of The Central of Food Production Zones in Merauke Regency

The Maro River and the Kumbe River are the downstream of the drainage system of Semangga District, Tanah Miring District, and Kurik District, the central point of food production in Merauke Regency. The water quality of these rivers is related to the quantity and quality of water from the drainage system, therefore agricultural activities and other local ceremonial determine the water flow in the drainage system. This study aimed to evaluate the water pollution index, the pollution loads, and the pollution load capacity of seven sites at the Maro and Kumbe Rivers. Based on Total Suspend Solid (TSS), Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD) results which did not meet the quality standards, the water quality of these rivers displayed a degradation. The water quality status of these rivers from upstream to downstream is at low pollution level. The pollution load capacity of the Maro River is at site AS-2 (low tide level). Whereas the Kumbe River cannot accommodate pollution load capacity at both high and low tide levels anymore as the pollution load capacity of this river has exceed the quality standard limit in Regulation of Government of Republic of Indonesia No. 22 / 2021 for Class II.

Study on corrosion, hydrogen permeation, and stress corrosion cracking behaviours of AISI 4135 steel in the tidal zone

High-strength steels are widely used in marine engineering; however, they suffer from the risks of corrosion, hydrogen permeation, and stress corrosion cracking (SCC) in wet–dry cyclic marine environments. In this study, the corrosion, hydrogen permeation, and SCC behaviours of AISI 4135 steel in the tidal zone were investigated using electrochemical corrosion, electrochemical hydrogen permeation, and slow strain rate tests, respectively, via field exposure. The results showed that the AISI 4135 steel sample placed at the high tide level had high SCC susceptibility because of severe pitting corrosion and hydrogen permeation, whereas the steel samples placed at the middle and low tide levels had low SCC susceptibilities. The dry/wet time ratio was crucial in determining the SCC behaviour and mechanism of the steel in the tidal zone. With increasing time ratio, the SCC mechanism changed from micro-void coalescence control to localised anodic dissolution and hydrogen embrittlement in tandem.

Characteristics of river discharge and its indirect effect on the tidal bore in the Qiantang River, China

Based on field data of river discharge, tide, tidal bore, and riverbed topography, the characteristics of river discharge, the effect of river discharge on riverbed erosion and sedimentation, and the feedback effect of riverbed erosion and sedimentation on the tide and tidal bore in the Qiantang River are analyzed. The results show that the inter-annual and seasonal variation of river discharge in the Qiantang River is noticeable, while the seasonal distribution of river discharge tends to be uniform after the construction of Xin'anjiang Reservoir. River discharge has a major effect on the erosion and sedimentation in the reach from Zhakou to Yanguan. There are laws of riverbed erosion in wet seasons and years and sedimentation in dry seasons and years. Relations in the Zhakou to Yanguan reach among the riverbed volume after the flood season, the mean and maximum river discharge during the flood season, and riverbed volume before the flood season are established. With the riverbed erosion from Zhakou to Yanguan, the low tide level decreases and the tidal range is amplified, and thus, the tidal bore is enhanced. The relation among tidal range, river discharge, and riverbed volume, as well as the one between the tidal bore height and tidal range is established on the basis of the field data. Furthermore, the variation range of tidal bores after the flood season is analyzed in wet and dry years. The indirect effect of the Xin'anjiang Reservoir on the height of the tidal bore is predicted and the mean height of the tidal bore from Zhakou to Yanguan decreases by 0.1–0.2 m.

Amplification of regional tides in response to sea level

The study investigates the temporal change in tides under the background of rapid sea level rise, for a highly vulnerable coastal region. It highlights the existence of non-astronomic tidal variability at seasonal and secular time-scales in the Ganga-Brahmaputra-Meghna (GBM) delta, along with increasing low and high tidal levels. The observed variability in semi-diurnal tides was found to be coherent to the mean sea level changes. M2 tide can be a proxy for sea level changes as they show a direct relationship. Steric changes were introduced in the barotropic ADCIRC (ADvanced CIRCulation) model and the results proved that change in water depth modulates the energetics of the tidal wave thereby causing amplification. A regionally varying tidal response was noticed, such that the regions associated with the GBM delta showed maximum amplification. The factors that can cause tidal amplification are region-dependent and coastal geomorphology plays an important role in it. Tidal prediction based on changing sea level was able to capture the observed seasonal modulation of tides and increasing trend in low and high tidal levels. Incorporating the effect of changing tides can improve the accuracy of tidal predictions and will help advance studies regarding regional sea level change, coastal flooding and tide-surge interaction.

Adaptive management of estuarine resource utilization and wetland conservation based on multi-temporal remote sensing: A case study of Minjiang Estuary, China

Adaptive management of estuarine resource utilization and wetland conservation (ERU&WC) have both socioeconomic and ecological implications because estuaries involve plentiful navigation, aquaculture, wetland, and land-reclamation resources but are featured with complexity and vulnerability of hydrodynamics, morphodynamics, and ecological processes. To achieve positive synergistic effects and prevent disasters by optimizing the allocation of estuarine space to various activities and biological habitats, there is a need to track the estuarine evolutionary trajectories and demarcate the spatial function subareas. However, estuarine field data acquisition is time-consuming, spatially limited, expensive, and there are some areas not accessible due to shallowness or moving sand bars. This paper presents an exact estuarine morphodynamics acquisition and evolution analysis based on multi-temporal remote sensing images, with Minjiang Estuary, China as a case study. The imageries with high tide level (1995, 2017) and low tide level (1995, 2002, 2010, and 2017) were chosen to track the changes of coastline, tidal flat, channel, sand bar, sand island, wetland vegetation, and the spatial heterogeneity of Minjiang Estuary, and the results show visually the section of shoreline change, the pattern of TCSS change and the part of tidal flat vegetation change, which are the fundamental data for demarcating the spatial function subareas. Also, the adaptive management rule was explored, and the schematic diagram of the estuarine morphodynamic evolution process and the framework of ERU&WC adaptive management were outlined. The research result will provide technical support and theoretical guidance for the management of other estuarine environments.

Mitochondrial cytochrome c oxidase subunit I (COI) metabarcoding of Foraminifera communities using taxon-specific primers.

Foraminifera are a species-rich phylum of rhizarian protists that are highly abundant in most marine environments. Molecular methods such as metabarcoding have revealed a high, yet undescribed diversity of Foraminifera. However, so far only one molecular marker, the 18S ribosomal RNA, was available for metabarcoding studies on Foraminifera. Primers that allow amplification of foraminiferal mitochondrial cytochrome oxidase I (COI) and identification of Foraminifera species were recently published. Here we test the performance of these primers for the amplification of whole foraminiferal communities, and compare their performance to that of the highly degenerate LerayXT primers, which amplify the same COI region in a wide range of eukaryotes. We applied metabarcoding to 48 samples taken along three transects spanning a North Sea beach in the Netherlands from dunes to the low tide level, and analysed both sediment samples and meiofauna samples, which contained taxa between 42 µm and 1 mm in body size obtained by decantation from sand samples. We used single-cell metabarcoding (Girard et al., 2022) to generate a COI reference library containing 32 species of Foraminifera, and used this to taxonomically annotate our community metabarcoding data. Our analyses show that the highly degenerate LerayXT primers do not amplify Foraminifera, while the Foraminifera primers are highly Foraminifera- specific, with about 90% of reads assigned to Foraminifera and amplifying taxa from all major groups, i.e., monothalamids, Globothalamea, and Tubothalamea. We identified 176 Foraminifera ASVs and found a change in Foraminifera community composition along the beach transects from high tide to low tide level, and a dominance of single-chambered monothalamid Foraminifera. Our results highlight that COI metabarcoding can be a powerful tool for assessing Foraminiferal communities.

Quantifying the Effects of Sea Level Rise on Estuarine Drainage Systems

AbstractMuch of the development of the low elevation coastal zone has involved the reclamation of low‐lying floodplains and wetlands through the construction of flood mitigation and drainage systems. These systems function throughout the tidal range, protecting from high tides while draining excess catchment flows to the low tide. However, drainage can only be achieved under gravity when water levels in the catchment drains are higher than those in the estuary. Changes to the tidal range and to the duration of the rising and falling tides that occur throughout estuarine waters will result in dynamic variations in the window of opportunity for gravity discharge within and between different catchments and under sea level rise (SLR). Existing concerns regarding SLR impacts have focused on the acute effects of higher water levels, but SLR will affect the full tidal range, and drainage systems will be particularly vulnerable to changes in the low tide. This study introduces the concept of the drainage window to address this limitation by assessing how the present‐day and future SLR tidal regimes may influence the drainage of different estuarine floodplains. Applying the drainage window to two different estuaries indicated that SLR may substantially reduce the opportunity for discharging many estuarine floodplain drainage systems. Reduced drainage creates a host of chronic problems that may necessitate changes to existing land uses. A holistic assessment of future changes to all water levels (including low tide levels and extended flood recession periods) is required to inform strategic land use planning and estuarine management.

Wave-current interactions at the Tagus Estuary Mouth (Portugal) under storm wave conditions

This study investigates interactions between waves, water levels and currents at the mouth of the second largest estuary in Europe (the Tagus Estuary, Portugal) under storm waves, combining field observations and a three-dimensional fully coupled wave-current modelling system. Tidal-induced water depth variations substantially modulate waves over the ebb shoal. During energetic conditions, low tide levels promote depth-limited wave breaking and energy transfer towards higher harmonics (triad interactions), which reduces wave heights and periods. Furthermore, for a given water level, tidal currents also influence wave propagation and drive strong modulations over shallow regions characterized by cross-channel current gradients. Flood currents change the mean wave direction by about 10–15° and tend to focus the wave energy flux towards coastal regions of the southern margin compared to a run without currents (20 to 30% increase of wave heights), while ebb currents reduce the wave heights. In addition, model results suggest that the saturation level associated with wave and current conditions at shallow locations may be close to the threshold where waves start to dissipate by whitecapping. At the peak of the storm, waves become a main driver of the circulation at the mouth scale, even in the 45-m deep main channel. Wave breaking acceleration over the ebb-shoal locally increases flood currents by 50 to 300% and reduces ebb currents by 20 to 50%.

Invasive Vaucheria (Xanthophyceae) at the lower shore of the Wadden Sea

ABSTRACT Vaucheria species have previously been restricted to upper shore habitats in the Wadden Sea (eastern North Sea, European Atlantic). In contrast to these previous observations, we have now found Vaucheria longicaulis and a distinct plastid lineage of V. velutina spreading along the lower shores, forming extensive turfs at and below low tide level under fully marine conditions near the Island of Sylt. Species and populations were identified by morphological features and reconfirmed by sequencing the plastid-encoding gene rbcL and the psbA-rbcL spacer region. We needed to modify primer sequences to successfully amplify the rbcL region of marine and brackish Vaucheria species. Due to distinct phylogenetic grouping, we can reject the possibility of niche expansions from the upper shore and propose recent introductions as the cause of the newly formed populations at the lower shore.