Changes In Bottom Topography Research Articles

МОДЕЛЮВАННЯ ДИНАМІЧНИХ ПРОЦЕСІВ ДОВКІЛЛЯ ПІД ЧАС РУХУ СУДНА З ВИКОРИСТАННЯМ РІС ТЕХНОЛОГІЙ

Remote methods of Earth’s surface research have become widely used in the 21st century, as they allow for a larger and more comprehensive observation area. These methods can provide valuable information about various Earth objects and phenomena, such as the changes in bottom topography in shallow water under navigation conditions. This article presents a novel approach to forecasting these changes by using natural processes as indicators and developing programs that can track and display them on electronic devices. The article introduces the concept of “scale factor” to determine the significance of different dynamic processes for the research, depending on their spatial and temporal dimensions. The article also proposes a dynamic map modelling method that can predict the siltation of the sea/river bottom for a given period of time and improve the model by comparing the forecast with the actual result. The article suggests that research should take into account the changes in the object over time and under the influence of various factors in a dynamic way. Based on the research, we draw the following conclusions: 1. The “scale factor” should be applied in dynamic navigation map research and compilation using different-scale data of the water surface and bottom topography; 2. A dynamic component should be added to the information block of the navigation cartographic systems ECDIS and Inland ECDIS, enabling the navigator to see the position of the vessel, taking into account the wave height relative to the bottom in real time; 3. The methods of parallel bottom topography transferring rely only on the data of statistical observations using iterations. These methods usually work well on sandy and silty soils, where the relief has clear wave-like forms, as well as frequent external influences following the main general direction. Keywords: RIS, dynamic processes, "scale factor", "chart dynamic model", ECDIS.

Freak wave in a two-dimensional directional wavefield with bottom topography change. Part 1. Normal incidence wave

In the propagation and evolution of sea waves, previous studies pointed out that the occurrence of the freak wave height is significantly related to the quasi-resonant four-wave interaction in the modulated waves. From numerical--experimental study over an uneven bottom, the nonlinear effect caused by the bathymetry change also contributes to the occurrence of extreme events in unidirectional waves. To comprehensively analyse the two-dimensional wavefield, this study develops an evolution model for a directional random wavefield based on the depth-modified nonlinear Schrödinger equation, which considers the nonlinear resonant interactions and the wave shoaling the shallow water. Through Monte Carlo simulation, we discuss the directional effect on the four-wave interaction in the wave train and the maximum wave height distribution from deep to shallow water with a slow varying slope. The numerical result indicates that the directional spreading has a dispersion effect on the freak wave height. In a shallow-water environment, this effect becomes weak, and the bottom topography change is the main influencing factor in the wave evolution.

On the scattering and radiation of water waves by a finite dock floating over a rectangular trench

In this study, the scattering and radiation of surface water waves by a finite dock floating over an asymmetric rectangular trench-type bottom topography are analyzed. The boundary value problems are handled for solutions analytically using a matched eigenfunction expansion method and numerically using the boundary element method. Various physical quantities associated with the scattering and radiation problems are studied for various values of wave and structural parameters. The results demonstrate that the scattering coefficients are significantly influenced due to the variation in dock length and depth ratios of the bottom trench. In the case of radiation problems, the dock length plays a crucial role in analyzing the radiation coefficients and wave excitation forces associated with each mode of motion. On the other hand, the effect of depth ratios of the bottom trench is negligible on the radiation coefficients. The present study reveals that the scattering of water waves by a floating dock over an abrupt change in bottom topography plays an important role in the construction of floating structures having more durability to resist harsh wave environments and reduce the wave impact near the seashore.

Wave transformation due to finite floating elastic plate with abrupt change in bottom topography

ABSTRACT The propagation of surface gravity waves in the presence of finite floating elastic plate over varying sea bottom profile is investigated using the Timoshenko-Mindlin plate theory. The continuity of velocity and pressure at the interfaces along with the continuity of deflection, slope, bending moment and shear force is employed with the support conditions at the plate edges. The numerical computation is performed to obtain the hydroelastic behaviour of the floating elastic plate due to abrupt change in bottom topography. The validation of the present analytical model is performed with the known results available in the literatures. Further, a detailed comparison of the numerical results is presented for different step bottom topography on the hydroelastic characteristics of a floating elastic platform. The present study will provide an insight into the effect of the ocean bottom profile on wave propagation due to the presence of a large floating elastic plate.

Freak wave in high-order weakly nonlinear wave evolution with bottom topography change

In deep-water, quasi-resonant four-wave interaction gives rise to the occurrence probability of extreme wave height, which leads to freak wave as a natural disaster. As water wave enters shallow water, four-wave interaction becomes weak and wave shoaling makes this effect become complicated. This study conducts a Monte Carlo simulation in modified Nonlinear Schrödinger equation considering bottom topography change, and gives spatial evolution of high-order nonlinearity in wave train from statistical moment. The result indicates, slope angle plays an important role in a shallow water depth, and steep slope brings about a significant enhancement of extreme event in distribution of maximum wave height and surface elevation.

Sound propagation in shallow water with periodic rough bottom

The rough sea bottom has a large effect on underwater acoustic propagation and underwater acoustic detection applications. By using the typical shallow water environment from the Yellow Sea, the acoustic propagation characteristics under the condition of both periodic rough sea bottom and strong negative thermocline layer are systematically analyzed by using the parabolic equation model RAM (where RAM stands for range-dependent acoustic model) and ray theory. For a low-frequency and short-range acoustic source, the transmission loss (TL) increases up to about 5–30 dB due to the existence of the periodic rough bottom. Abnormal TLs and pulse arrival structures with different source depths, different periods and heights of the rough bottom are analyzed and summarized. Specifically, when the period of the rough bottom is constant, TL increases with the height of the rough bottom increasing. When the height of the rough bottom is constant, the effect of the rough bottom on the sound propagation becomes smaller with the increase of the period. The mechanism of the TL difference caused by rough bottom is explained by using the ray theory. The incidence and reflection angle of the sound ray on the sea bottom are changed due to the periodic rough bottom, which makes small grazing angles of some of the rays incident at sea bottom become large grazing angles, and the bottom loss increases. On the other hand, the change of the reflection angle increases the number of ray interaction with the sea bottom, causing the reversion propagation. Therefore, the energy of the sound field will attenuate with range increasing. The influence of the periodic rough bottom on the sound pulse propagation is mainly reflected in the energy conversion between sound rays (or normal modes) with different angles, the increasing of energy attenuation of some sound rays with large angles, and the decreasing of multipath structure. The change of the arrival time and relative amplitude of the multipath structure affect the frequency spectrum of the sound field, which will affect the performance of the method based on matching field localization. Most of existing studies focus on the influence of the change in large scale sea bottom topography on the sound field, but there are few studies on small scale periodic sea bottom fluctuations, and the relevant summary of the law of sound propagation is lacking. When sonar is used in the actual shallow water environment, more attention should be paid to the influence of the periodic rough bottom. In addition, the present research results also have important reference significance for the spatial accuracy of surveying and mapping of sea bottom topography.

Прогнозирование динамики морского дна и её отображение на электронных навигационных картах

n presented research, there are some explanations about mechanisms of using natural processes to make forecast of changes in bottom topography in shallow water under navigation conditions. The key factor is the development of programs that can track changes in natural processes with displaying and fixation on electronic devices. Any research should preferably be carried out considering changes of the object over time and under the influence of various factors simultaneously and dynamically. In the article dynamic processes are divided into "significant" and "insignificant".

УЧЕТ ДИНАМИКИ РЕЛЬЕФА ДНА ДЛЯ ТЕХНОЛОГИЙ, ПРИМЕНЯЕМЫХ В РЕЧНЫХ ИНФОРМАЦИОННЫХ СЕРВИСАХ

Science and technology achievements in the 21st century have qualitatively changed the traditional methods and techniques of Earth's surface research. Nowadays, remote methods have been used widely, when an observer or a measuring device is located at a certain distance from the study object in order to increase the observation area by several times. These materials can expand horizons of researchers, lead to increasing the flow of valuable information about already known objects and phenomena of the Earth.In presented research, there are some explanations about mechanisms of using natural processes to make forecast of changes in bottom topography in shallow water under navigation conditions. The key factor is the development of programs that can track changes in natural processes with displaying and fixation on electronic devices. Any research should preferably be carried out considering changes of the object over time and under the influence of various factors simultaneously and dynamically. In the article dynamic processes are divided into "significant" and "insignificant". This dependence is determined by the scale of space and time, where and when they occur. The concept of "scale factor" is introduced in order to determine significance of dynamic processes influence during research. Presented in the research dynamic map modelling method enables to make a forecast of siltation of the sea / river bottom for a given period of time. After comparing the forecast with the actual result, you can make corrections of the selected function, i.e. constantly improving the model. As a result of the research, we came to the following conclusions: 1. The “scale factor” should be entered in dynamic navigation map research and compilation with using different-scale data of the water surface and bottom topography; 2. It is recommended to enter a dynamic component into the information block of the navigation cartographic systems ECDIS and Inland ECDIS, allowing the skipper to see the position of the vessel, considering the wave height relative to the bottom in real time; 3. Above methods of parallel bottom topography transferring are based only on the data of statistical observations with using iterations. These methods usually give proper results on sandy and silty soils, where the relief has distinct wave-like forms, as well as relatively often repeated external influences with following the general main direction.

Anomalous Waves Triggered by Abrupt Depth Changes: Laboratory Experiments and Truncated KdV Statistical Mechanics

Recent laboratory experiments of Bolles et al. (Phys Rev Fluids 4(1):011801, 2019) demonstrate that an abrupt change in bottom topography can trigger anomalous statistics in randomized surface waves. Motivated by these observations, Majda et al. (Proc Natl Acad Sci 116(10):3982–3987, 2019) developed a theoretical framework, based on deterministic and statistical analysis of the truncated Korteweg-de Vries (TKdV) system that successfully captures key qualitative features of the experiments including the robust emergence of anomalous statistics and heightened skewness in the outgoing wavefield. Here, we extend these parallel experimental and modeling efforts with several new findings that have resulted from a synergetic interaction between the two. By precisely relating model parameters to physical ones, we calibrate the model inverse temperature to the specific conditions present in the experiments, thereby permitting a quantitative comparison. We find theoretically predicted distributions of surface displacement to match the experimental measurements with surprising detail. Prompted by the presence of surface slope in the TKdV Hamiltonian, we present new experimental measurements on surface slope statistics and compare them to model predictions. Analysis of some deterministic trajectories of TKdV elucidates the experimental length and time scales required for the statistical transition to a skewed state. Finally, the theory predicts a peculiar relationship between the outgoing displacement skewness and the change in slope variance, specifically how their ratio depends on the wave amplitude and depth ratio. New experimental measurements provide convincing evidence for this prediction.

Scientific cruise research 2019

The article provides information on the first results of the study of bottom material taken during geological works in the framework of complex research expeditions "Danube-2019" and "Black Sea-2019" in accordance with the Agreement on Scientific and Technical Cooperation between Scientific Hydrophysical Centre of the National Academy of Sciences of Ukraine and State Hydrography Service. The purpose of expeditionary geological research was to obtain relevant empirical data on general trends in changes in bottom topography and main features of floor surface and sedimentation.Comprehensive expeditions collected factual data on the hydrographic, hydroacoustic and hydrological status of the studied waters and in a test mode made geological sampling of the bottom of the North-Western shelf coastal part of the Black Sea and the Danube mouth (within Ukraine) using developed and prepared equipment. Information about the works was added to the oceanographic data bank of the National Academy of Sciences of Ukraine. The practical significance of the obtained results is to field test the technology of geological sampling and further cameral work.

Effects of sea-level rise on tides and sediment dynamics in a Dutch tidal bay

Abstract. Sea-level rise (SLR) not only increases the threat of coastal flooding, but may also change tidal regimes in estuaries and coastal bays. To investigate such nearshore tidal responses to SLR, a hydrodynamic model of the European Shelf is downscaled to a model of a Dutch coastal bay (the Oosterschelde, i.e., Eastern Scheldt) and forced by SLR scenarios ranging from 0 to 2 m. This way, the effect of SLR on tidal dynamics in the adjacent North Sea is taken into account as well. The model setup does not include meteorological forcing, gravitational circulation, and changes in bottom topography. Our results indicate that SLR up to 2 m induces larger increases in tidal amplitude and stronger nonlinear tidal distortion in the bay compared to the adjacent shelf sea. Under SLR up to 2 m, the bay shifts from a mixed flood- and ebb-dominant state to complete ebb dominance. We also find that tidal asymmetry affects an important component of sediment transport. Considering sand bed-load transport only, the changed tidal asymmetry may lead to enhanced export, with potential implications for shoreline management. In this case study, we find that local impacts of SLR can be highly spatially varying and nonlinear. The model coupling approach applied here is suggested as a useful tool for establishing local SLR projections in estuaries and coastal bays elsewhere. Future studies should include how SLR changes the bed morphology as well as the feedback effect on tides.

Evolution of High-Order Weakly Nonlinear Wave with Bottom Topography Change

Evolution of High-Order Weakly Nonlinear Wave with Bottom Topography Change

Assessing Hydrological and Sedimentation Effects from Bottom Topography Change in a Complex River–Lake System of Poyang Lake, China

In recent years, a dramatic decline in Poyang Lake water levels and a shrinking water surface have raised concerns about water security and the wetland ecosystem. Changes in bottom topography due to sand mining activities in the lake was supposed to be one of the influencing factors of these changes. In response to this issue, the current study analyzed the change of lake bottom topography from observed digital elevation model (DEM) data, and quantitatively assessed the spatial and temporal responses of lake hydrology based on the framework of the neural network and the sediment effect was examined afterward. Results showed a total volume of 11.54 × 108 m3/year (about 0.96 × 108 m3/year or 1.58 × 108 t/year sediment) in net change of lake bottom topography in recent years, among which 97% was directly exported by commercial sand mining. During the study period, 2000–2011, intensive sand mining extended the central part of Poyang Lake and widened and deepened the outflow channel of the northern lake. This great change of lake bottom topography caused an average annual increase of 182.74 m3/s of lake outflow and a decline of 0.23 m–0.61 m in water levels across the lake. However, lake water levels are not consistent and show remarkable spatial and seasonal differences. The effects of changes in lake bottom topography on lake hydrological processes continue to grow as sand mining activities in the lake continue. More research on the environmental impacts is required for sustainable management of the lake ecosystem.

Co-seismic change in ocean bottom topography: Implication to absolute global mean sea level change

Earthquakes perturb both the ocean bottom topography due to displacements of sea floor and the geoid due to mass redistribution, which induces the relative sea level (RSL) change. However, the relative global mean sea level (GMSL) change is zero in that sea water mass is conserved. But the absolute GMSL change is not zero because earthquakes displace total ocean mass with respect to the Earth's center of mass (CM) which remains unchanged after an earthquake. This displacement, i.e. the absolute GMSL change, may be detectable by altimetry since the satellites are orbiting around CM. In this paper, we proposed a method to estimate co-seismic absolute GMSL change caused by earthquakes based on the point dislocation theory for a spherically symmetric, non-rotating, elastic and isotropic (SNREI) Earth. This change can be directly connected to the perturbation of ocean bottom topography. We first computed co-seismic displacements as well as the change in geo-potential and solved the sea level equation to validate the insignificance of the oceans' feedback, i.e. the loading effect due to RSL change, to co-seismic displacements. The results imply that the loading effect due to RSL change is negligible on displacements while is considerable on geoid. We then computed the absolute GMSL change caused by co-seismic vertical and horizontal displacements by making use of the integrated Green's function method. The numerical results show that a large earthquake may raise the absolute GMSL by magnitude of sub-millimeter and the recent three large events cause GMSL to rise about one millimeter, in which the contribution from horizontal displacement is non-negligible.

Quantifying the Human Induced Water Level Decline of China’s Largest Freshwater Lake from the Changing Underlying Surface in the Lake Region

In recent years, dramatic decline in China’s largest freshwater lake, Poyang Lake, has raised wide concerns about water supply and ecological crises in the middle–lower Yangtze River reaches. To assist in resolving the debates regarding the low water regime of the lake, the current study quantitatively assessed the enhanced water level decline from the changing underlying surface in the Poyang Lake region. It is the first time that the magnitude, temporal–spatial difference, trend development and background mechanism of lake water level variation and its causes are studied comprehensively. The results revealed that the changing underlying surface in the lake region has caused an average decline of annual water level of 0.26 m ~ 0.75 m across the lake during 2000–2014, which shows great seasonal and spatial differences. The enlarged outflow cross–section due to extensive sand mining was the major reason for the effect on water level decline in the northern lake. While, increased water surface gradient should be attributed to water level decline in the southern lake. The long–term increasing trend of annual lake water level decline reflects the cumulative effects of lake bottom topography change caused by the continuous south movement of sand mining activities.

Methods for Investigating Sediment Flux under High-Energy Conditions on the Southeast Florida Continental Shelf using Laser Airborne Depth Sounding (LADS) in a Geographic Information System (GIS) Dataframe

ABSTRACT Finkl, C.W. and Vollmer, H.M., 2017. Methods for investigating sediment flux under high-energy conditions on the southeast Florida continental shelf using Laser Airborne Depth Sounding (LADS) in a Geographic Information System (GIS) dataframe. Laser Airborne Depth Sounding (LADS) bathymetric surveys conducted in 2001 and 2008 bracket two hurricane landfalls (Hurricane Ivan in 2004 and Hurricane Katrina in 2005) in Broward County, southeast Florida, thus providing an opportunity to investigate changes in bottom topography as a result of wave and current action. The seafloor in this region is characterized by a wide range of sedimentary features that are normally stabilized (held in place) by outcrops of carbonate bedrock and coral reefs. During high-energy events, however, the sedimentary deposits are partially mobilized by waves and currents. This methodological study used the two LADS bathymetric surveys to construct triangulated irregular networks (TINs, which are a digital means of representin...

Numerical Study on Change of Bottom Topography Data in a Closed Water Area

Techniques to investigate change of bottom topography in a closed water area are described. Numerical techniques are illustrated. Governing equations of flow were reduced to a system of ordinary differential equations with the collocation method, and a standard ODE solvers were applied. A governing equation of sediment transport was solved numerically. Numerical results were compared with measurement results.

Bottom topography change patterns of the Lake Poyang and their influence mechanisms in recent 30 years

利用鄱阳湖1980、1998和2010年3期湖盆水下地形数据,结合出、入湖泥沙输移数据以及流域水土流失、水库建设等资料,较为系统地研究鄱阳湖近30年来湖盆冲淤的时空变化特征及其影响因素.研究表明,19801998年,松门山以南主湖体位置淤积现象明显,平均淤高0.82m,该淤积主要是由这一阶段内流域水土流失加剧所引起的;19982010年,在大规模植树造林和水库建设等人类活动影响下,鄱阳湖淤积现象减缓.但是在入江水道上湖盆高程显著下降,平均下降速率高达30.75cm/a,这与入江水道处持续采砂和水流冲刷等因素有关;近30年来,“五河”入湖的洲滩区域冲淤变化及趋势有所差异,修水、抚河及赣江三角洲呈现逐渐降低的趋势,饶河入湖漫滩总体上以淤积为主,且地形坡度趋于变缓.研究结果对鄱阳湖水资源合理开发、水利工程建设及航运管理等均具有一定的实践和参考价值.;In this study, extensive investigation was done on the changes in bottom topography across the Lake Poyang through geographical information systems(GIS) techniques and comparison of underwater topography data of 1980, 1998 and 2010. Possible mechanisms behind the topographic changes were also discussed based on watershed hydrological data(e.g. sediment transport, soil erosion and reservoir construction). The results showed that (1) the main water body region was obviously deposited with an average deposition value of 0.82 m during 1980-1998. These alterations of bottom topography were frequently caused by the increased soil erosion in the upstream of the basin. (2) During 1998-2010, the deposition trend of the bottom topography among Lake Poyang was slowed down to some extent. This was probably caused by the afforestation and reservoir construction program. However, in this period, bottom topography in the channel entrance was decreased remarkably with the average declining rate of 30.75 cm/a. The increases in flow discharge and gravel extraction have been considered as the main causes of this topographic change in the region. (3) In recent 30 years, the changing trends of deposition/erosion among five rivers' alluvial cone were different. Bottom topography elevation in Xiushui, Fuhe and Ganjiang alluvial cone expressed gradually decreasing trend, while Raohe alluvial bay showed a rising tendency as a whole. The results of the study are of great theoretical and practical significance to water resources reasonable utilization, dam construction and shipping management across the Lake Poyang.

Rip Currents Generation by Geomorphological Change in Gyeongpo Beach, South Korea

ABSTRACT Cho, W.C.; Kim, J.H.; Hur, D.S., and Kim, I.H., 2014. Rip currents generation by geomorphological change in Gyeongpo Beach, South Korea. Most beaches in Gangwon-do, South Korea have topographic characteristics that are mainly influenced by waves and seabed conditions. Gyeongpo Beach is one of the most famous beaches as a tourist attraction in the east coast of South Korea, and many people have visited and enjoyed sea-bathing in this area during the summer holiday season. However, rip currents are often source of danger for the swimmers because rip currents drag the swimmers away from the beach and put them to death by drowning. As Gyeongpo Beach has a straight shoreline, it is directly exposed to high waves that induce a significant change of bottom topography. Sandbars are usually formed in the processes of topographical changes from the swash zone to the surf zone and increase the possibility of rip current occurrence. Therefore, the monitoring of the topographic changes in this region is impor...

Monthly variation of some parameters about internal solitary waves in the South China sea

In this paper, by non-dimensional analysis, it is found that finite-depth theory is more appropriate to the study of internal solitary waves (ISWs) in the South China Sea (SCS) than shallow-water theory. The 1-degree grid data of monthly mean temperature and salinity data at standard levels in the SCS are used to solve the linearized vertical eigenvalue problem. The nonlinear parameter and the wave phase speed are computed, then the nonlinear phase speed and the characteristic half-width of ISWs are calculated respectively by two different theories to investigate the difference between these two parameters in the SCS. The nonlinearity is the strongest near the continental slope of the SCS or islands where the bottom topography changes sharply, it is stronger in summer than that in winter; it increases (decreases) as pycnocline depth deepens (shallows), stratification strengthens (weakens) and pycnocline thickness thins (thickens). The nonlinear wave phase speed and the characteristic half-width are the largest in deep sea area, they then reduce peripherally in shallower water. The nonlinear wave phase speed in the SCS changes slightly with time, but the characteristic half-width changes somewhat larger with time. In most of the SCS basin, the nonlinear wave phase speed derived from shallow-water theory is very close to that derived from finite-depth theory, but the characteristic half-width derived from shallow-water theory is about 0.2–0.6 times larger than that derived from finite-depth theory. The ISW induced horizontal current velocity derived from shallow-water theory is larger than that derived from finite-depth theory. Some observed and numerical modeled ISW characteristic half-widths are compared with those derived from shallow-water and finite-depth theories, respectively. It is shown that, the characteristic half-widths derived from finite-depth theory agree better with observational and numerical modeled results than those derived from shallow-water theory in most cases, finite-depth theory is more applicable to the estimation of ISW characteristic half-widths in the northern SCS. It is also suggested that, to derive the precise ISW parameters in further study, the physical non-dimensional ratios which are related with ISW characteristic half-width, amplitude, thermocline and water depths should be calculated, so that an appropriate theory can be chosen for estimation.