Shallow Water Areas Research Articles

Geological Structure and Oil and Gas Exploration of the Eastern Mediterranean

Qian, X., 2020. Geological structure and oil and gas exploration of the Eastern Mediterranean. In: Hu, C. and Cai, M. (eds.), Geo-informatics and Oceanography. Journal of Coastal Research, Special Issue No. 105, pp. 119–123. Coconut Creek (Florida), ISSN 0749-0208.The continental shelf of the Eastern Mediterranean contains abundant hydrocarbon resources. With the continuous development of exploration technology, many large and superlarge oil and gas fields have been discovered in the Levant Basin and the Nile Delta Basin. The hydrocarbon reservoirs in the Levant Basin are mainly distributed in the Oligocene–Lower Miocene Tamar sandstone and Miocene shale caprock. The shallow-water area of the Nile Delta Basin has a high degree of exploration and complete production facilities, making it the best area for rolling exploration; the mid- to deep-water Oligocene section will be the main potential area for the future discovery of large- and medium-sized natural gas fields; the ultra-deep-water area has the exploration potential of large-scale Miocene and Pliocene biogas reservoirs. The discovery of offshore gas fields may quickly change the situation of long-term energy shortages and is potentially of great significance to changing the energy supply pattern in the region.

Impact of hydrological conditions on the radiocarbon reservoir effect in lake sediment 14C dating: the case of Kusai Lake on the northern Qinghai-Tibet Plateau

Abstract The hydrological conditions of a lake system strongly influence the reservoir effect in the radiocarbon dating of endogenic organic and inorganic carbon in lake sediments. In this paper, we compare 14C dating with varve counting results for cores from Kusai Lake to determine the temporal changes in 14C reservoir ages during the last 2000 years. Based on the 14C budget equation for a lake system, the characteristics of geomorphology, topography, and river systems in the catchment, and the physical and chemical properties of modern water in Kusai Lake, the hydrological conditions and the reservoir effect age are discussed. The reservoir age of the sediment core from northwestern Kusai Lake (i.e., deep water area) fluctuates slightly between 2980 and 3310 years, while that from southeastern Kusai Lake (i.e., shallow water area) fluctuates greatly between 3130 and 4010 years. Under the relatively steady conditions of atmospheric 14C levels for the past 2000 years, the 14C level in the dissolved inorganic carbon (DIC) of Kusai Lake is mainly related to carbon influxes from river and glacial meltwater and carbon outfluxes in lake water. The water in the shallow water area is more affected by the Kusai River, glacier meltwater, and lake outflow than the water in the deep water area, which has caused larger temporal changes in the radiocarbon reservoir ages in the shallow water area than in the deep water area during the last 2000 years.

A numerical modeling‐based predictive methodology for the assessment of the impacts of ship waves on YOY fish

AbstractThe effects of inland navigation on the aquatic ecosystem are numerous. One of the most relevant impacts from the ecohydraulic point of view is ship‐induced waves, resulting in the local and temporary alteration of the hydrodynamic regime, especially in shallow water areas. In this paper, a novel hydrodynamic modeling‐based evaluation framework is presented and tested for the prediction of habitat use and drift risk of juvenile fish during wave events of different intensities. A vertically resolved numerical wave tank was built up using field measurements of a real vessel‐generated wave event from the Hungarian Danube. High‐frequency pressure time series were utilized to numerically reproduce the phase accurate wave trains, while acoustic Doppler velocity time series were exploited for the verification of the model. Results of the spatiotemporally resolved hydrodynamic model were combined with data from the literature to explore a case study of juvenile Nase (Chondrostoma nasus). Results highlighted the significant horizontal extension (10–15 m) of the area exposed to decreased habitat suitability and increased drift risk. Moreover, the model revealed significant vertical variabilities in the investigated near‐bank area as well, emphasizing the relevance of depth resolved hydrodynamic modeling in ecohydraulic investigations.

Multi-channel observation experiments of audio-frequency magnetotelluric technology in shallow water

Geophysical electromagnetic (EM) surveys for imaging the subsurface structure under lakes, rivers, or other water bodies have attracted increasing attention. Based on forward modeling and field experiments, a boat-towed audio-frequency magnetotelluric (AMT) multi-channel observation system for shallow fresh water was developed preliminarily. Through the development of water electrodes and the streamer cable, a boat-towed multi-channel data acquisition cable was developed. We carried out a variety of different comparative experiments, such as water- and land-AMT experiments, different polar-distances, and acquisition time-length experiments, and observation experiments at different time, in ditches or rivers around the Qilihai Wetland, Tianjin, China. We also carried out profile detection experiments using this system in southern Baiyang Lake, Xiongan New Area, China. The experimental results demonstrate that the proposed water–AMT system can be utilized to characterize subsurface structure underneath shallow water areas, advancing the potential of geophysical surveys on rivers or lakes.

Underwater Topography Inversion in Liaodong Shoal Based on GRU Deep Learning Model

The Liaodong Shoal in the east of the Bohai Sea has obvious water depth variation. The clear shallow water area and deep turbid area coexist, which is characterized by complex submarine topography. The traditional semi-theoretical and semi-empirical models are often difficult to provide optimal inversion results. In this paper, based on the traditional principle of water depth inversion in shallow areas, a new framework is proposed in combination with the deep turbid sea area. This new framework extends the application of traditional optical water depth inversion methods, can meet the needs of the depth inversion work in the composite sea environment. Moreover, the gate recurrent unit (GRU) deep-learning model is introduced to approximate the unified inversion model by numerical calculation. In this paper, based on the above-mentioned inversion framework, the water depth inversion work is processed by using the wide range images of GF-1 satellite, then the relevant analysis and accuracy evaluation are carried out. The results show that: (1) for the overall water depth inversion, the determination coefficient R2 is higher than 0.9 and the MRE is lower than 20% are obtained, and the evaluation index shows that the GRU model can better retrieve the underwater topography of this region. (2) Compared with the traditional log-linear model, Stumpf model, and multi-layer feedforward neural network, the GRU model was significantly improved in various evaluation indices. (3) The model has the best inversion performance in the 24–32 m-depth section, with a MRE of about 4% and a MAE of about 1.42 m, which is more suitable for the inversion work in the comparative section area. (4) The inversion diagram indicates that this model can well reflect the regional seabed characteristics of multiple radial sand ridges, and the overall inversion result is excellent and practical.

Accuracy assessment of global ocean tide models in the South China Sea using satellite altimeter and tide gauge data

In this study, to meet the need for accurate tidal prediction, the accuracy of global ocean tide models was assessed in the South China Sea (0°–26°N, 99°–121°E). Seven tide models, namely, DTU10, EOT11a, FES2014, GOT4.8, HAMTIDE12, OSU12 and TPXO8, were considered. The accuracy of eight major tidal constituents (i.e., Q1, O1, P1, K1, N2, M2, S2 and K2) were assessed for the shallow water and coastal areas based on the tidal constants derived from multi-mission satellite altimetry (TOPEX and Jason series) and tide gauge observations. The root mean square values of each constituent between satellite-derived tidal constants and tide models were found in the range of 0.72–1.90 cm in the deep ocean (depth>200 m) and 1.18–5.63 cm in shallow water area (depth<200 m). Large inter-model discrepancies were noted in the Strait of Malacca and the Taiwan Strait, which could be attributable to the complicated hydrodynamic systems and the paucity of high-quality satellite altimetry data. In coastal regions, an accuracy performance was investigated using tidal results from 37 tide gauge stations. The root sum square values were in the range of 9.35–19.11 cm, with the FES2014 model exhibiting slightly superior performance.

Integration of Satellite-Derived Bathymetry and Sounding Data in Providing Continuous and Detailed Bathymetric Information

A hydrographic survey can be a cumbersome sometimes. The data can be sparse, providing it can be costly, and it took a lot of manpower and time. Space-borne data like multispectral images can be a helpful tool towards hydrographic survey, especially in the shallow water area. The company like EOMAP and TCARTA make use of Satellite-Derived Bathymetry (SDB) as a tool and product. Would it be great if it also can be applied in Malaysia, especially on the low-risk job or survey planning? Enlarging the survey area and providing a continuous and detailed water depth information is the main objective in this research. In order to complement with convenience and cost reduction, the author used Landsat 8 “(free downloadable images)” in this research. Structuring the procedure is the central part of the process involving pre-processing and processing step until the final product obtained. In this research, the author used various kind of bathymetry algorithms such as Single-Band Algorithm (SBA), Green-Band Algorithm (GBA), and Stumpf. Moreover, the author also uses Principal Component Analysis (PCA) tool from ArcMap and Spear Relative Water Depth: Log-Ratio Transform tool from ENVI to derived bathymetry. All of this bathymetry algorithm gives out a different concept with a different statistical approach. The final result then will be compared and evaluated with Single-Beam Echosounder data (ground truth).

Ограничительные факторы в оценке энергоэффективности судов-толкачей большегрузных составов во внутреннем плавании

The issues of energy efficiency assessment for inland navigation vessels and focus on the need to implement different approaches in this context in relation to single vessels against pushers with heavy convoys are considered. This is due to transportation technologies, which have a number of significant differences when pushing a heavy caravan. The analyses were made for the data of systematic testing of ships and the values of energy efficiency indicators obtained for them according to the methodology applied by IMO for ships in international maritime shipping. Fluctuations in water levels on inland waterways and on river sections, in particular, especially when moving pushers with caravans of barges, have a significant impact on the performance of the hydrodynamic propulsive complex. Using the example of the data from the Danube river gauging stations, the assuring enough depth both when performing one voyage at different sections of movement, and during a calendar year were considered. The ratios of the fairway depth and the draft of the vessel are determined, which are boundary for a decrease in the speed of movement in connection with a change in resistance with a tangible negative effect of shallow water. In this regard, issues of increasing fuel consumption in shallow water areas and related factors affecting energy efficiency are also considered. At the same time, the interrelation of energy efficiency and eco-friendliness dictates the use of integrated approaches not only from the standpoint of quantitative indicators of fuel consumption, but also from the standpoint of the use of modern technologies for cleaning exhaust gases. The factors contributing to the development of energy efficiency management are considered as separate categories. These include the work of the River Information Services (RIS), the training of river boatmasters and the instability factors in the shipping and bunker markets. The conclusions about the inseparability of the considered factors, as well as the need for their further comprehensive consideration in order to create a common algorithm for managing energy efficiency in the inland navigation were made.

A Comparative Analysis to Model Bathymetry using Multi-sensor Satellite Imageries

Accurate and high-resolution water depth information are important for wide range of coastal research and monitoring. In this case, providing an accurate bathymetric map is a major challenge for remote sensing. This study developed and evaluated a semi-parametric regression to extract depth information using various image datasets (Landsat 8, Sentinel 2A and Worldview 2). We compared the ability of these imageries to map depth information using generalized additive model (GAM). GAM is a semi-parametric generalized linear model which allow for nonlinear relationships between covariates and the target variable. We used the Morotai shallow water area in Indonesia to apply GAM in deriving depth information. We found that higher image spatial resolution results in higher mapping accuracies. This study highlights the potential of selected images and mapping techniques for deriving bathymetric data.

Greenhouse Gas Emissions Dynamics in Restored Fens After In-Situ Oil Sands Well Pad Disturbances of Canadian Boreal Peatlands

In-situ oil extraction activities impact the vast mosaic of boreal wetlands and uplands. Peatland restoration in these regions aims at reestablishing crucial peatland functions, such as peat accumulation and carbon (C) sequestration. In order to assess the success of fen restoration, we evaluated the biogeochemical conditions, the seasonal carbon balances via carbon dioxide (CO2) fluxes and methane (CH4) emissions, and addressed the global warming potential following different restoration techniques at two restored in-situ oil sands well pads, during two consecutive growing seasons. Restoration work involved: 1) the partial or complete removal of introduced well pad construction materials, and spontaneous revegetation, or 2) the partial removal of foreign clay, in addition to reintroduction of typical fen plant species such as Larix laricina, Salix lutea and Carex aquatilis. Comparisons were done with regional reference ecosystems (REF) consisting of three peatlands: a wooded bog, a wooded rich fen and a wooded extreme-rich fen. While the average electric conductivity of restored sectors (946 μS cm−1) was higher compared to REF (360 μS cm−1), the pH was quite similar (pH 5.8 REF, pH 6 restored). Dissolved organic carbon concentration was lower in all restored sectors (5–11 mg L-1 restored sectors, 15–35 mg L-1 REF), presumably due to the still incomplete recovery of vegetation and lower organic matter content associated with remnant well pad material. Re-establishment of shrub and brown moss species improved significantly the C uptake. However, the active introduction of plant species was no crucial restoration step, in order to return species beneficial for C uptake. Restoration treatments that were leveled closest to the surrounding REF showed the most similar seasonal C balance to REF. In shallow open water areas resulting from the complete removal of all construction materials, we measured the highest methane emissions making these flooded sites net C sources to the atmosphere with elevated global warming potential. The partial removal of the well pad’s mineral soil to near the water table level and the surface elevation of the surrounding ecosystem seems to be the most effective site management method to sequester carbon efficiently. However, further research is needed to evaluate the suitability of this restoration method for the recovery of biodiversity and possible impacts of residual foreign materials on fen ecosystems.

Organic geochemistry of source rocks in the Baiyun Sag of the Pearl River Mouth Basin, South China Sea

Source rock samples (i.e., drill cuttings) of the Wenchang, Enping, and Zhuhai formations from the Baiyun sag in the deep-water area of the Pearl River Mouth Basin (PRMB) in the South China Sea were collected and subjected to organic geochemical analysis. The three sets of potential source rocks were further divided into six types, based on biomarkers and carbon isotopic compositions: shallow lacustrine and semideep–deep lacustrine source rocks of Wenchang Formation, shallow lacustrine and marine transgression-related source rocks of Enping Formation, and littoral and neritic source rocks of Zhuhai Formation. The Wenchang Formation semideep–deep lacustrine source rocks developed in the Baiyun Sag are characterized by low ratio of C30 4-methylsteranes to C29 steranes (4-Me/C29 < 0.25) and relatively 13C-depleted isotopic compositions (δ13Ckerogen < −27.5‰), which are obviously different from those from shallow-water area in the PRMB. Rock–Eval analysis shows the Wenchang Formation develops good source rocks, which are better than those in the Enping Formation. The Zhuhai Formation does not contain effective source rocks because of its low maturity. According to the distribution of bicadinanes and oleanane, it is speculated that shallow lacustrine source rocks of Wenchang Formation in the northern Baiyun Sag have similar high bicadinanes to C30 hopane ((W + T)/C30H) and low oleanane to C30 hopane (OL/C30H) ratios to those of the Enping Formation, indicating their possible contribution to the discovered hydrocarbon accumulations. In summary, hydrocarbons generated by the Wenchang Formation source rocks should become the next key exploration target in the Baiyun Sag.

Future projections of offshore wind energy resources in China using CMIP6 simulations and a deep learning-based downscaling method

Good knowledge of future wind energy resources is crucial for sitting and planning studies of wind farms. The simulation results from the Coupled Model Intercomparison Project Phase 6 (CMIP6) and a proposed new downscaling method based on the bidirectional gated recurrent unit (BiGRU) are both used in this paper to study future offshore wind energy resources in China. The proposed new downscaling method is validated and compared to two traditional methods. It is found that the spatial patterns of downscaled wind speed are highly consistent with the reference data, and biases are significantly reduced by the new method, especially in coastal and shallow water areas. Using the new method, we downscale the CMIP6 future projected simulation results and generate a new dataset of offshore wind speeds in China for the period of 2021–2100 with a resolution of 0.25°. Multi-model ensemble (MME) results project small decreases in the offshore wind speed and wind power density over the East China Sea and increases in those parameters over the South China Sea, for the middle and end of the 21st Century (2041–2060 and 2081–2100) under two representative scenarios (SSP2-4.5 and SSP5-8.5).

Tracking and Localization based on Multi-angle Vision for Underwater Target

With the cost reduction of underwater sensor network nodes and the increasing demand for underwater detection and monitoring, near-land areas, shallow water areas, lakes and rivers have gradually tended to densely arranged sensor nodes. In order to achieve real-time monitoring, most nodes now have visual sensors instead of acoustic sensors to collect and analyze optical images, mainly because cameras might be more advantageous when it comes to dense underwater sensor networks. In this article, image enhancement, saliency detection, calibration and refraction model calculation are performed on the video streams collected by multiple optical cameras to obtain the track of the dynamic target. This study not only innovatively combines the application of AOD-Net’s (all-in-one network) image defogging algorithm with underwater image enhancement, but also refers to the BASNet (Boundary-Aware Salient network) network architecture, introducing frame difference results in the input to reduce the interference of static targets. Based on the aforementioned technologies, this paper designs a dynamic target tracking system centered on video stream processing in dense underwater networks. As part of the process, most nodes carried underwater cameras. When the dynamic target could be captured by at least two nodes in the network at the same time, the target position could then be calculated and tracked.

Bathymetry Mapping of Hikkaduwa Coral Reef Using Multispectral Satellite Imagery

In previous era, bathymetry was determined by using conventional methods which retrieved the depth at a single point at one time. Later it was developed to many kinds developed systems which can determine water depth more accurately, but high in cost. In recent years, with remote sensing data it can be easily map at shallow water areas up to 25m. The idea behind this method is to use the reflection intensity of the various wavelengths captured by the satellite sensors. The ENVI Suite Relative Water Depth Tool empowers to create an item with relative water depths rapidly. As they do not appear actual depths (the relative depths are scaled from zero to one), the water depth comes about are relative, and the purpose is to deliver a large feel to the area's bathymetry. The yield must still be calibrated to field information to assess real depth. While coral reefs are found in Sri Lanka, the reefs around Hikkaduwa are among the most diverse and accessible which has a typical fringing coral reef with a shallow crest. The reef has suffered high degradation due to both natural and human activities. According to analysis, due to the relative significance changes of bathymetry comes about from the today, the coral reef has, by comparison, changed around 48.5% over the past 25 a long time (1995 to 2020) due to both natural and human exercises. By summarizing the real values for each bathymetry outline, it can be analyzed that between 2002 and 2019, the coral reef debased by roughly 5%, depending on the increasing of average depth within the study area. This has led to the creation of a new tool for the use of multispectral satellite image data to map shallow water bathymetry, referred to as satellite derivatives bathymetry. And there is no data available for evaluation to be used to assess the performance of the satellite-derived models. And with the lack of high resolution and undisturbed (i.e. without cloud disturbances) multispectral satellite imageries, it limits the derivation of bathymetry data.

SWAMP, an Autonomous Surface Vehicle expressly designed for extremely shallow waters

Wetlands, the geographic areas where water meets the earth, are ecosystems essential for life and an increasing number of conventions, directives and research projects recognise the necessity of protecting them. Nevertheless the number, quality and spacial resolution of surveys is modest due to the absence of expressly addressed tools. In this paper the design, construction and testing of the first prototype of an innovative class of Autonomous Surface Vehicles (ASVs) for the extremely shallow water and remote areas of wetlands is presented. SWAMP (Shallow Water Autonomous Multipurpose Platform) is a full y electric, modular, portable, lightweight, and highly-controllable ASV. It is a catamaran, equipped with four thrusters azimuth Pump-Jet thrusters that are flush with the hull and specifically designed for this vehicle. SWAMP is also characterised by small draft soft-foam, unsinkable hull structure with high modularity and a flexible hardware/software architecture. Each hull can be considered as a single vehicle, being equipped with a full navigation, guidance and control package, as well as propulsion, power and communication systems. The extreme modularity is also guaranteed thanks to the adoption of on-board Wi-Fi communication architecture: the two mono-hull vehicles are connected via Wi-Fi as well as all the modules aboard each of them.

A Study on Vessel Motion Control with Towing Ropes and Dampers for Berthing

The vessel maneuvering problem in the harbour area is generating considerable interests in terms of marine cybernetics. The vessel is operated by the pilot and moves at ultimately low or zero speed in shallow water area. In this case, the vessel is usually assisted by the cooperation of thrusters, main propulsion system, tugboats and pilots, etc. In this paper, we suggest a new vessel berthing technique using dampers and winches as a solution for complex and dangerous berthing work. In the proposed berthing method, we design the controller to counteract the waves and other effects for guaranteeing the safety during the berthing process. Also, in this paper, experiments are conducted to verify the proposed vessel berthing method and the effectiveness of the designed control system in which unpredictable external force is applied. Finally, the experiment results show that the vessel could approach the defined position in time with effective control action made from designed controller.

Critical Water Depth and Installation Curves for Submarine Cable Deployment Process

The purpose of the present paper is to propose installation curves for submarine cable deployment process for different water depths and tension deployment, emphasizing on the importance of modelling the “out of water” cable segment and the friction force between cable and overboard chute of the installation vessel. A custom-made analysis tool has been further expanded and used for the calculation of the cable hydraulic critical responses. Moreover, the concept of the critical water depth is proposed analytically for first time to define the cases in which the “out of water” cable segment can be ignored without denoting the accuracy of the minimum bending radius calculation. In addition, correction factors are proposed in relation to water depth and bottom tension values in order to eliminate the error of the safety factor calculation. Numerical formulation of the friction has been incorporated in the custom-made analysis tool as a further development. The analysis of various cable deployment cases proves that the inclusion of the “out of water” segment in the analysis is critical in shallow water areas. In contradiction, the modelling of the friction force is critical in deep water areas. However, both parameters are potential causes of important analysis errors.

Phytodiversity of the "Samara plavni" regional landscape park

Рresented the results of floroecological, hydrobotanical and geobotanical researches of the Regional Landscape Park "Samara Plavni". Regional Landscape Park (RLP) "Samara Plavni" is located in the waters of the Samara Bay, which was formed as a result of flooding of the floodplain of the Samara River during the creation of the Zaporozhye (Dnieper) Reservoir and the surrounding area. Conducted a systematic and bioecological analysis of the flora of vascular plants. Studied the composition of the rare fraction of flora and associated flora element. The research was carried out according to the generally accepted methods of floristic, geobotanical and hydrobotanical research. Bioecomorphic characteristics of species (selection of ecomorphs) are compiled according by A. L. Belgard ecomorph system using the following ecomorphs: biomorphs (one-, two-, perennials); heliomorphs (relation to light); hygromorphs (relation to the aquatic environment); tropomorphs (relation to nutrition); cenomorphs (growth in certain phytocenoses). Ecological characteristics of species were given from literature sources and according to the results of many years of own research. The analysis of the adventitious fraction was carried out at the time of drift – archaeophytes, neophytes. Advent status was determined on the basis of literature data. Vegetation of the regional landscape park "Samara Plavni" is represented by natural and semi-natural groups. The main area of shallow water is occupied by massifs of Phragmites australis (Cav.) Trin. ex Steud and groups of submerged vegetation. The tree and shrub vegetation of the park is represented by natural forest complexes, semi-natural groups and artificial plantations. Meadow and meadow-swamp vegetation of the landscape park is represented by complexes of associations of mesophytes and hygrophytes. The floristic list of vascular plant flora is 617 species. Hemicryptophytes, perennials, sciogeliophytes and heliophytes, mesotrophs, mesophytes, hygrophytes predominate here. Among cenomorphs, most species are represented by meadow (139) and forest (108) species. The rare fraction of flora is 73 species. There are 128 species of ruderal flora and 140 species of adventive flora, including 6 invasive species. At the time of entry into the study area allochthonous element of flora is divided into two groups: archaeophytes – 63 species (45%) and neophytes – 77 species (55%).

Combined geometric-radiometric and neural network approach to shallow bathymetric mapping with UAS imagery

There is a pressing need for shallow bathymetry in regions around the world, including in fragile marine ecosystems, such as coral reefs. Unfortunately, mapping these shallow-water areas using in situ or boat-based methods is expensive, time consuming, and potentially dangerous, due to the need to put personnel and/or boats in high-energy nearshore areas, which may contain rocks, reefs, and other submerged hazards. For this reason, passive remote sensing methods of shallow bathymetric mapping have been rapidly growing in interest and usage. Two general categories of approaches using passive imaging can be distinguished as: (1) those based on geometry (stereo-photogrammetry); (2) those based on radiometry (attenuation of light in the water column). These two broad categories of approaches have been tested on imagery collected using aircraft and satellites in numerous previous studies. Recent work within the geometric category includes processing unmanned aircraft system (UAS) imagery using Structure from Motion and Multi-View Stereo (SfM-MVS) photogrammetry, while radiometric methods encompass the broad range of spectral bathymetry retrieval algorithms. Each broad approach category has advantages and disadvantages. Fortunately, the geometric and radiometric approaches are highly complementary. The geometric approaches tend to work best in areas of high bottom texture, which facilitates feature matching in the SfM-MVS software. Meanwhile, the radiometric approaches work best in relatively homogeneous bottom types. To leverage the strengths of each type of approach and overcome their respective weaknesses, this work develops and tests a combined geometric-radiometric bathymetric mapping approach designed for shallow-water mapping from UAS imagery. Four radiometric models of varying complexity are tested, ranging from a color-based lookup table approach to neural networks. Two UAS flights on Buck Island, off St Croix in the U.S. Virgin Islands (USVI), are used to assess the accuracy of the methodology when compared to aerial bathymetric lidar data. The results show that the combined geometric-radiometric approach provides an increase in spatial coverage of up to 61% and improvement (i.e. decrease) in 95th percentile error of up to 49% when compared to traditional refraction-corrected SfM-MVS bathymetry.

Distribution pattern simulation of multiple emergent plants in river riparian zones

AbstractEmergent plants in river riparian zones (RRZs) are an important part of the river ecosystem, and the evolution of their spatial distribution patterns is a direct indicator of the health of river ecosystems. In previous studies, the simulation of the spatiotemporal pattern evolution process for emergent plants mainly focused on the overall pattern change of emergent plant communities. However, they did not distinguish the types of emergent plants and ignored the differences in response of different emergent plants to environmental changes. The difference in the competitiveness of different emergent plants will affect the distribution of emergent plants. In this research, the transformation rules of five emergent plants under different water levels were determined, and the Cellular Automata model was constructed to dynamically simulate the proliferation of emergent plants in RRZs. The results showed that when the water level was 11.5 m, the total area of emergent plants reached the maximum, and among the five emergent plants, Phragmites australis was the dominant species. When the water level dropped to 12.5 m, the shallow water area in the east of the riverside zone increased, and P. australis expanded rapidly in the east. By dynamically simulating the distribution of emergent plants in RRZs, the distribution status of the emergent plants in RRZs in the future can be obtained. It is of great significance for biodiversity conservation and resource management in riparian zones.