Shallow Water Zone Research Articles

An Experimental Study on Dynamic Response of Geotextile Structures in Regular Waves

Flexible geotextile structures are widely used in coastal engineering, such as geotextile mattress used in bottom protection engineering and sand-filled geotextile tube used in reclamation project. This kind of structure can adapt to varying bathymetry condition quite well and has significant engineering effect, but when the sediment under the structure was eroded and cavity occurs, this geotextile material may be ripped at continuous wave action, especially in the shallow water zone. However, the failure mechanism is still not clear. The dynamic response of geotextile structure in regular waves was firstly studied. In order to study tensile stress in the geotextile structures caused by wave, a series of 2-D physical models were designed. Under a selected geotextile structure condition, numbers of tensile force sensor were addicted around the edge of the geotextile material, and then fixed at the bottom of the wave flume. By changing wave parameter and water depth, the relationship between tensile stress and wave parameters were obtained and discussed. It turns out that the tensile force detected in the experiment is much less than the upper limit of material's tensile strength, which means that the geotextile may not be easily damaged just by the tensile stress caused by waves. It is suggested that the structure may break out due to abrasion between the structure and the internal material. Details of the discussion on the experimental data will be presented.

Fish diversity and conservation of fishery resources of the river Pilasalunki, Phulbani district

The study of fish diversity of the river Pilasalunki situated in Phulbani distict, Odisha was attempted during 2012. A total of 23 fish species belonging to 9 families were recorded. Out of the recorded species, 35 per cent are enlisted as vulnerable, 52 per cent as lower risk near threatened category. Maximum number of fish species were collected from slow flow site (31.6%) followed by silty sand beds (17.6%), deep water zone (15.8%), gravel habitat (15.8%), fast flow zone(10.5%) and least in shallow water zone. Shannon diversity index (H') fluctuated from 0.29 to 0.93, Simpson dominance index ranged from 0.14 to 0.52 and Margalef richness fluctuated from 1.38 to 9.65. Bray Curtis cluster analysis recorded 100 per cent similarities within Wallago attu, Labeo dyochilusand Nemacheilus botia (sub cluster-I), Puntius sarana, P. Sophore,and Mystus cavasius (sub cluster-II), Glosogobius giurisand Mastacembalus armatus (sub cluster-III). Correspondence analysis indicated Nemacheilus botia, Labeo dyochilus, Heteropneustes fossilis, Wallago attu, Cirrhinus reba, Glosogobius giuris, Mastacembalus armatus and Mystus cavasius, Channa gachua, Puntius sophoreand Puntius sarana congregated distantly from origin suggesting their stock enhancement through conservation measures.

Petrographic Characteristics of the Proterozoic Vempalle Carbonates, Cuddapah Basin, India and their Implications

Abstract: The Vempalle Formation of the Proterozoic Cuddapah basin has a well developed sequence of carbonate rocks, which are interbedded with shales, siltstones and chert. The stromatolitic carbonates are conspicuous at many places but the oolitic carbonates are less prominent and are present only in some areas. All the carbonates are pervasively dolomitized. Petrographic examination of these carbonates revealed that they are predominantly made up of fine grained micrite with patchy development of sparite and chert/quartz. The stromatolitic carbonates show distinct banding of alternate carbonate and cherty layers. The latter are rich in organic matter indicating prevalence of profuse biogenic activity. The oolitic carbonates comprise of ooids showing both concentric and radial patterns and made up of carbonate/ chert and cemented by micro/mega quartz or carbonate itself. Diagenetic and post depositional features are reflected in cementation, recrystallization, compaction, stylolite formation and silicification processes. Various stages of cementing material are observed. Secondary vein fillings of carbonate or quartz traverse the carbonate/cherty groundmass. Intraclasts present suggest occasional erosional destruction of associated sediments, short lived transport and local redeposition. Accessory silicate minerals represent terrigenous influx during deposition. Dolomitization of the carbonates was fabric retentive and early diagenetic. The environmental conditions were characterised by low energy, within a shallow water zone, in occasional higher energy events and turbulence. The carbonates appear to have been deposited on a shallow water ramp within a tidal regime.

Epiphytic diatom communities onPhyllophora antarcticafrom the Ross Sea

AbstractAntarctic seaweeds play an important ecological role, but the vast macroalgal beds, typical of the shallow-water zone, are not efficiently grazed. However, macroalgal thalli are covered by epiphytic diatoms which represent a rich food source for higher trophic levels. We describe the abundances, growth form structure, species composition and distribution patterns in the diatom communities associated withPhyllophora antarcticafrom selected sites within the Ross Sea. The goal of this work was to learn more about the relationships between various components of the epiphytic community and its habitat. To examine diatoms at the microscale, four relatively well described sampling sites were chosen and analyses were performed on a large number of diatoms. All observations and counts were made with the scanning electron microscope. Samples collected in the same season but from different sites and under different sea and ice conditions differed significantly in terms of species composition, but all represented abundant and well-developed diatom communities. A list of species associated withP. antarcticafrom the investigated area is provided and the influence of the sampling effort on the observed diatom diversity is assessed.

Molecular diversity of coral reef-associated zoanthids off Qeshm Island, northern Persian Gulf

The Persian Gulf, a semi-enclosed sea in the subtropical northwest of the Indian Ocean, is noted for its unique biodiversity under its extreme ecological conditions. Despite high biodiversity levels, many groups of marine invertebrates in this area have remained uninvestigated. The order Zoantharia (zoanthids) is one of these taxonomically neglected groups. In this study, diversity of shallow water zoanthids off the Qeshm Island, the largest island in the Persian Gulf, was investigated for the first time. Using in situ field examination integrated with 16S rDNA sequencing and phylogenetic analysis, the presence of three zoanthid species in the inter-tidal and shallow water zone of Qeshm Island were demonstrated: Zoanthus sansibaricus (n = 12) with five morphotypes, Palythoa cf. mutuki (n = 10) with two morphotypes and Palythoa tuberculosa (n = 4) with just one morphotype. In addition to species identification, molecular examination determined phylogenetic relationships of specimens with other previously reported zoanthid species. While Zoanthus sansibaricus and Palythoa tuberculosa are two known zoanthid species, based on molecular data, Palythoa cf. mutuki is potentially a novel undescribed species. However, due to lack of data on zoanthid research and distribution for the entire Persian Gulf, further investigation is needed to clearly ascertain this matter.

Phytomass and Specific Diversity of Macrophyte Vegetation in the Middle Reach of the Yenisei River

Phytomass and specific diversity of macrophytes of the Yenisei River on the stretch from Krasnoyarsk to the mouth of the Angara River were estimated. The investigation showed that littoral macrophyte vegetation clearly differs in specific composition and biomass in the deep water (H>0,8 m) and shallow water (H<0,7 m) zones. Potamogeton lucens principally dominates in deep-water communities; several dominating species are noticed in the shallow-water zone (P.perfoliatus, P.pectinatus, Elodea canadensis and some other species). The average biomass of deep-water macrophytes on the stretch of the river (431±101 g/m2 D.W., n=15, SD) was 2.5 times higher (p<0,01) than the biomass of shallowwater vegetation (172±81 g/m2, n=15). Phytomass loss observed in the two dominating species of pondweed, P. lucens and P.perfoliatus, during the season of vegetation was 3.1±3.4 % (n=17) and 11.6±7.8 % (n=37), respectively. Biomass production of P.lucens ranged from 240 to 630 g/m2, biomass production of P.perfoliatus was 360 g/m2. The estimated Shannon-Margalef index (based on dry biomass) revealed higher specific diversity of the shallow-water macrophyte vegetation as compared to the deep-water one on the majority of sampling sites, but the mean values did not differ statistically (0,90±0,78 и 0,53±0,55, n=15). The biomass and diversity of macrophytes of the Yenisei River did not change considerably at different distances away from the sources of technogenic pollution of the river.

Comparative study of the reproductive performance and White Spot Syndrome Virus (WSSV) status of black tiger shrimp (Penaeus monodon) collected from the Bay of Bengal

A comparative study to assess length, weight, fecundity, hatching rate and White Spot Syndrome Virus (WSSV) prevalence in black tiger shrimp (Penaeus monodon) broods collected from shallow and deep water zones of the Bay of Bengal was carried out in Cox's Bazar, Bangladesh. Average size and reproductive performance of broods from the deep zone were significantly higher than those of broods caught from the shallow zone. The incidence of WSSV infection in shallow zone broods was much higher than that in deep zone broods. The association between depth zone and WSSV infection is independent of brood size. WSSV infection is negatively associated with hatching rate, irrespective of location. Exclusive use of tiger shrimp broods collected from the deep zone could reduce vertical transmission of WSSV by 46% without additional management measures. A variety of economic, social and ecological factors make this potential solution unworkable however. A better alternative could be to promote the use of domesticated P. monodon broods.

Sub-seafloor resistivity sensing using a vertical electrode configuration

There is growing interest in marine direct current (DC) resistivity methods for sub-seafloor exploration of a broad range of geophysical and geological targets. To address this, we have developed a new marine DC method with a vertical electrode configuration (VEC). Compared to conventional marine DC methods that use a horizontal electrode configuration, the shape and position of our VEC cable can be controlled relatively easily. Therefore, the VEC is suitable for operations in regions of steep bathymetry and for expeditious sub-seafloor resistivity exploration. In this study, we introduce a water-resistant electrode array cable and an onshore multichannel DC measurement system for stable and rapid data acquisition. To evaluate the performance and efficiency of the new system, we conducted field experiments in the shallow water zone at Shimizu Port, Suruga Bay, Japan. In order to quantitatively analyze the VEC-DC data, we adopt a 1-D numerical modeling code that computes the electric potential and apparent resistivity generated by a point and dipole current source used in the VEC-DC measurement. These can be placed at any position with an arbitrary electrode configuration in a multilayered space, including seawater and sub-seafloor layers. We also develop an inversion code for the VEC-DC data based on a simulated annealing (SA) optimization and applied this to the field data. The observed data is of sufficiently good quality to be used for inversion, and the SA result demonstrates that the proposed VEC-DC system is able to estimate the sub-seafloor resistivity structure.

Late Cretaceous and Paleogene stratigraphy and structure linking offshore with onshore north Westland, New Zealand

Revised stratigraphic interpretation of offshore seismic data west of Greymouth Coalfield links the onshore Taramakau-1 and offshore Haku-1 wells. Tracking the Eocene Rapahoe Group between the wells across a Cretaceous offshore (Takutai South) basin precludes a reflection at its base from being the Oligocene Cobden Limestone as previously supposed. A different seismic reflection is recognized as the Cobden Limestone, allowing inference of the offshore to onshore structure across a monocline cut by the Cape Foulwind Fault Zone and a near-shore shallow-water zone lacking seismic data. Sequences in and probably beyond local synclinal basins beneath the offshore Cenozoic strata are assigned to the Upper Cretaceous Paparoa Group coal measures. Some have been buried deeply enough that, at the estimated geothermal gradient of c. 42 °C/km, oil has been generated and expelled. The possibilities of stratigraphic and structural traps, including a possible minor dome southwest of Greymouth, should be investigated.

Peculiarities of evaporation regime of Lake Ladoga

The evaporation regime of Lake Ladoga is specified using the renewed meteorological data. The traditional approach is supplemented with a new method of estimating the impact of shallow-water zones on the evaporation intensification worked out by G.N. Panin. The obtained results corroborate that the level of precipitation minus evaporation varies in different zones of the lake that can influence the water mass redistribution in the lake in certain seasons.

Geostatistical approach for elucidating the potential titanium-zirconium placer areas: Evidence from the Transural placer district

Geostatistical analysis of the composition of mineral assemblages of Oligocene sediments in the Mansi and Severnaya Sosva areas of the Transural titanium-zirconium placer district was accomplished by the method of the principal components. High significance of the first principal component and its composition revealed by this analysis suggest the existence of an efficient placer-forming process that can produce commercial concentrations of ore minerals. Interpretation of statistical indicators is given. The results confirm the facies zoning of sediments revealed previously in the Oligocene basin. They show that the paleolittoral and shallow-water zones with a moderate hydrodynamic activity in the depositional environment have the highest potential of titanium-zirconium raw material. Analysis of the mineral potential revealed that the Mansi and Severnaya Sosva areas can accommodate a medium-scale placer deposit.

Constructed marginal shallow water zones along a navigable canal: possibilities and constraints for helophyte and aquatic vegetation

Banks of navigable canals are often stabilized with “hard” materials resulting in unsuitable conditions for marginal riparian vegetation. A constructed marginal shallow and sheltered water zone can favour riparian vegetation. In 1998, a new canal branch with shallow water zones was constructed along the canal Ghent-Bruges (Belgium). This study analysed plant vegetation development of these shallow zones, its spatial variation and its mid-way succession. For this purpose, riparian vegetation was investigated by plots in the middle of the shallow water zones, on the canal bank side and on the defence dam side in 2006 and 2009. The studied shallow water zones permitted the development of helophyte vegetation on the sides but hardly in the middle. Differences in number of taxa, diversity-index and Grime's competitiveness and ruderality were observed on the sides. The application of different construction materials is discussed as a possible cause. An increase of competitiveness and a decrease of ruderality indicated vegetation succession during the period 2006–2009. Rooted aquatic plant vegetation was poorly developed in the studied shallow water zones probably due to the deposition and accumulation of fine sediments. The results were interpreted in relation to possible design principles of shallow water zones and might be useful for waterway managers, policy-makers and technicians in future bank engineering projects along navigable canals. Moreover, the study contributes to the knowledge of mitigating negative ecological effects associated with navigation. Such bank rehabilitation measures may be necessary to achieve the ecological goals of the European Water Framework Directive.

The 1912 earthquake in South Baikal: traces in bottom sediments and gas release into the water column

Large earthquakes took place in southern Cisbaikalia in the first half of 1912. They might have caused a mass release of gas (methane?) into the water column of Lake Baikal and the atmosphere near Sharyzhalgai station of the Circum-Baikal Railroad. This phenomenon was observed in August 1912 by the residents as rising water columns several meters high and reported in the regional press.To find traces of this event, core was recovered from bottom sediments at a depth of 1300 m in winter 2010. The depth interval 1–8.7 cm is a homogeneous layer, no more than 100 years old (210Pb dating). The sediments here are poor in SiO2biog but richer in Corg than the underlying sediments. Also, they are marked by a considerable content of terrestrial plant remains, a lower content of planktonic diatoms, and higher contents of benthic and ancient diatoms. These data indicate that the layer under study formed as a result of the 1912 earthquake, with a considerable contribution from the littoral and shallow-water zones of Lake Baikal.

GPU Acceleration of Tsunami Propagation Model

Tsunami propagation in shallow water zone is often modeled by the shallow water equations (also called Saint-Venant equations) that are derived from conservation of mass and conservation of momentum equations. Adding friction slope to the conservation of momentum equations enables the system to simulate the propagation over the coastal area. This means the system is also able to estimate inundation zone caused by the tsunami. Applying Neumann boundary condition and Hansen numerical filter bring more interesting complexities into the system. We solve the system using the two-step finite-difference MacCormack scheme which is potentially parallelizable. In this paper, we discuss the parallel implementation of the MacCormack scheme for the shallow water equations in modern graphics processing unit (GPU) architecture using NVIDIA CUDA technology. On a single Fermi-generation NVIDIA GPU C2050, we achieved 223x speedup with the result output at each time step over the original C code compiled with -O3 optimization flag. If the experiment only outputs the final time step result to the host, our CUDA implementation achieved around 818x speedup over its single-threaded CPU counterpart.

파와 흐름에 노출된 관로 주변부 국부세굴에 영향을 미치는 매개변수

이 논문은 천해역에서 파와 흐름에 노출된 관로주변의 세굴을 다루고 있다. 해저관로주변의 세굴특성을 알아보기 위해, 관경, 주기, 파고 및 흐름속도를 달리해 가면서 실험을 수행하였다. 파와 흐름 발생장치가 사용되었고, 흐름은 파와 동일한 방향과 그 역방향으로 발생시켰다. 실험결과를 이용하여, 세굴심과 KC수, Froude 수, Ursell 수 및 속도비등과 같은 무차원 매개변수들과의 상관관계를 분석하였다. 상대세굴심은 속도비 함수가 0에 접근하면 파의 성분에 지배되고, 1에 접근하면 흐름성분에 지배되는 것을 명료히 보였다. 속도비 함수는 파와 흐름이 공존하는 영역에서 관로주변의 세굴변화를 표현할 수 있는 적절한 매개변수임이 입증되었다. 또한 Froude 수와 KC수에 각각 파의 수립자속도와 흐름속도를 고려한 매개변수들은 세굴심을 나타내는데 더 좋은 상관관계를 보여 주었다. This paper deals with the local scour around a pipeline exposed to combined waves and current in the shallow water zone. To investigate the characteristics of the scour around a pipeline on the sea bed, experiments were performed according to the various pipe diameters, wave periods, wave heights, and current velocities. Wave generator and current generator were used for the experiments. Two current directions were used ; co-direction and counter direction to the waves. With the experimental results, the correlations between the scour depths and non-dimensional parameters such as Keulegan-Carpenter number(KC), Froude number(Fr), Ursell number(Ur) and velocity ratio were analysed. The relative scour depths were found obviously to be dominated by the wave component when the velocity ratio function approaches zero and those are gorverned by the current component when the velocity ratio approaches unity. Velocity ratio function was approved to be a proper parameter which is able to express the change of the scour in the combined wave and current zone. Also considering the orbital velocity and the current velocity into Fr numer and KC number respectively, scour depths show more favorable correlationship with the parameters.

Occurrence and public perception of jellyfish along the German Baltic coastline

Jellyfish accumulations are often problematic for tourism and fisheries both along European coastlines and overseas. They damage the reputation of several seaside resorts and cause serious economic losses. On the German Baltic coast, jellyfish accumulations are well known, too. Besides population increase due to anthropogenic effects, normal hydrodynamic processes are notable key factors when it comes to jellyfish accumulations. Along German Baltic coastlines, moon jellyfish (Aurelia aurita) occur most frequently but also stinging lion’s mane jellyfish (Cyanea capillata) appear regularly, however not as abundant. The objectives of our study were a) to screen when, where, how many and which jellyfish species occur on German Baltic coasts, b) to find the causes for jellyfish accumulations and c) to evaluate how beach visitors perceive native medusae and whether information can influence their perception. Different methods where combined: systematic jellyfish observations in cooperation with lifeguards, investigations of jellyfish abundance in shallow water zones, and interviews with beach visitors. Our results suggest that jellyfish occurrence along the German Baltic coast correlates with offshore wind or shore-parallel wind, which cause upwelling events. In contrast, there is no evidence that frequency of jellyfish occurrence was dependent on water temperature in summer. In regard to tourism, we found that beach visitors who received information about jellyfish stated to feel significantly less bothered by medusae. Overall, this article addresses different methods to learn more about jellyfish accumulations and it shows information strategies in terms of improved beach management.

Blackened bioclasts and bituminous impregnations in the Koněprusy Limestone (Lower Devonian), the Barrandian area, Czech Republic: implications for basin analysis

Carbonate reef talus facies of the Koněprusy Limestone (Pragian, Lower Devonian, Barrandian) locally exhibit widespread impregnation by organic matter resulting in a partial to complete blackening of the limestones. Two contrasting types of impregnation are recognized: blackening of individual carbonate fossils and bioclastic layers within the limestone originated very early during diagenesis. The blackening is due to finely dispersed organic matter and possibly some iron sulphides and clay minerals that selectively adhered to the outer layers of corals, bryozoans, and crinoid fragments, leaving other fossils unaltered. These darkened fossils are similar to black pebbles—i.e., reworked, dark to black limestone clasts and bioclasts that are known to occur exclusively in shallow-water zones of both ancient and modern carbonates. The alteration of fossil fragments may have taken place in very shallow-water environments, possibly those of saline and reducing back-reef lagoons or supratidal-intertidal zones, with organic matter being derived from decayed algae and microbes, or early vascular terrestrial plant material. Following the coloration, the blackened fossils were removed from their original position by waves or storms and transported into relatively deeper-water reef slope settings to form graded, “salt-and-pepper”-colored bioclastic beds. The presence of blackened fossils in the carbonate succession may point to episodic emergence and indicates a vanished vegetated siliciclastic hinterland that may once have existed to the west or south from the present-day erosive edge of the Barrandian Devonian strata. Subvertical veins cutting the Koněprusy Limestone and filled with black solid bitumen and blackened calcite resulted from a subsequent but substantially later diagenetic event, which is a testament of aqueous and petroleum fluid migration through the succession during deeper burial. Microthermometric characteristics of the aqueous inclusions embedded in vein calcite indicate that the veins were precipitated by brines of low to moderate salinity (0.5–9.5 wt% NaCl equiv.) with temperatures in the range of 87–116°C. The bitumen in the veins is epi-impsonite (Rr = 0.70–1.90%), which is interpreted as degraded petroleum residuum that experienced thermal alteration at around 120°C. The AFT modeling combined with fluid inclusion microthermometry and wider geological considerations indicate that the veins originated during the Variscan orogeny, most probably upon deep burial of the Lower Paleozoic strata in Carboniferous time.

Experiments on excitation and receiving of coherent high-frequency acoustic signals in a shallow-water region of a marine shelf

Possibilities of formation of coherent high-frequency signals for underwater acoustic observations in shallow-water shelf zones of the ocean with an irregular bottom are experimentally investigated. The methods of medium-conjugate excitation and receiving of complex modulated pulses with the help of vertical and horizontal arrays are probated. It is shown that medium-conjugate spatial, frequency, and time filtering makes it possible to decrease reverberation interferences by more than 40 dB.

Development of integrated marine monitoring network on southern coastline of Caspian sea

Monitoring of water surfaces through permanent measurement of hydrodynamic and meteorological data is one of the main requirements in safe and sustainable water management. The Caspian Sea, the major surface water body in Iran, significantly affects more than 600 km of urban and industrial coastline. In the present work, an integrated marine monitoring network for the entire southern coastline of the Caspian Sea was developed. The main design concerns centered on the network measuring components and data recording, checking, filtering, gap recognition, and transferring systems. Four coastal monitoring stations were assigned, along with two regional collecting stations and one central data station for gathering, checking and delivering recorded data at different access levels. Applicable guidelines on selection of measuring devices for both shallow and deep water zones are presented herein.

Development of integrated marine monitoring network on southern coastline of Caspian sea

Monitoring of water surfaces through permanent measurement of hydrodynamic and meteorological data is one of the main requirements in safe and sustainable water management. The Caspian Sea, the major surface water body in Iran, significantly affects more than 600 km of urban and industrial coastline. In the present work, an integrated marine monitoring network for the entire southern coastline of the Caspian Sea was developed. The main design concerns centered on the network measuring components and data recording, checking, filtering, gap recognition, and transferring systems. Four coastal monitoring stations were assigned, along with two regional collecting stations and one central data station for gathering, checking and delivering recorded data at different access levels. Applicable guidelines on selection of measuring devices for both shallow and deep water zones are presented herein.