Bathymetry Research Articles (Page 1)

Enhancing underwater topography estimation by integrating backpropagation networks with multivariate geophysical data.

On a trawled north Pacific seamount, reductions of benthic megafauna abundance, diversity, and ecosystem function are correlated with increased evidence of fishing.

Turbidity currents, gravity-driven sediment-laden flows, govern material transport and shape underwater landscapes across diverse environments. While extensively studied in marine settings, their dynamics in freshwater systems remain underexplored. We present multi-temporal, multi-scale observations from the Aare Delta of Lake Brienz (Switzerland), combining Acoustic Doppler Current Profiler measurements with high-resolution repeated bathymetric surveys to capture turbidity currents and resulting morphological changes. A single turbidity current reached near-bed velocities of 0.65 m/s and induced upslope migration of a cyclic step by at least 4 m within minutes. Characterisation of overall bedform migration across the channel network over five years highlights the cumulative imprint of turbidity currents and frames these short-term changes within the broader context of channel reworking. Together, our results show striking similarities in overall flow structure, bedform morphologies, and dynamics between freshwater and marine systems, underscoring the value of lacustrine settings as accessible, scaled-down environments for advancing turbidity current research.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-21833-6.

Preliminary results of bathymetric surveys undertaken northwest of Kyushu during cruises GS23 and GB23

To implement effective reservoir management practices, critical assessments of sediment deposition are important. In this study, we developed an automated approach using the Google Earth Engine to assess reservoir sedimentation and validated it on two reservoirs: Koka and Gefersa I/II, which are located in the upper Awash River Basin (ARB), Ethiopia. Landsat 8 Operational Land Imager (OLI) and Landsat 5 Thematic Mapper (TM) data from the study period, along with reservoir water level, pre-impoundment reservoir capacity and recent bathymetry survey data, were used. Statistical validation confirmed a strong association between the obtained results and the bathymetric survey results: Koka Reservoir (Pearson correlation coefficient (r) = 0.999, regression coefficient (R2) = 0.976, Nash-Sutcliffe efficiency (NSE) = 0.997) and Gefersa I/II Reservoir (r = 0.997, R2 = 0.992, NSE = 0.955). This study highlights that GEE effectively estimates reservoir sedimentation, providing valuable insight for the active management of reservoirs, especially in resource-limited regions.

Abstract. Advancements in geospatial technology have benefited the hydrographic and maritime professions in many ways. Yet, compared to hydrographic data collection and processing, chart compilation workflows remain relatively slow, mainly due to limited human resources and the availability of automated algorithms that respect nautical charting constraints and Electronic Navigational Chart (ENC) database requirements. This work presents our research efforts to streamline the nautical chart compilation process through the introduction of automated processes and improving the efficiency and accuracy of existing. Among these processes are fundamental generalization tasks such as those for soundings, islands, and depth contours; ENC product specific requirements, such as those for reducing file size through the removal of collinear vertices forming polylines and polygons; and the updating of dependent features in the ENC database after generalization of one of their shared geometries.

The Rupat Strait, a strategically crucial marine channel separating Sumatra Island from Rupat Island, exhibits complex hydrodynamic characteristics influenced by tidal propagation from the adjacent Malacca Strait. As a vital shipping corridor, the strait's navigational safety is fundamentally governed by its bathymetric profile and tidal regime. This study implements an integrated methodological framework combining in situ bathymetric surveys with MIKE 21 hydrodynamic modeling to assess morphological dynamics quantitatively. Systematic validation of model outputs against field measurements revealed significant spatial variations in seafloor topography, including pronounced shallowing (>6.6 m) and substantial deepening (≤17 m) at distinct locations. Concurrent analysis of tidal data demonstrated extreme water level fluctuations, ranging from -2.36 m during the lowest astronomical tides to +6.28 m during peak tidal surges. These geomorphological alterations appear correlated with anthropogenic pressures, particularly intensive shipping traffic and coastal zone modifications, suggesting a coupled natural-anthropogenic forcing mechanism governing the strait's evolving morphodynamics. The findings highlight the critical need for ongoing monitoring to ensure maritime safety and sustainable coastal management in this rapidly changing marine environment

Abstract: This study examines sediment dynamics at Kiri Dam, Nigeria (1982–2025), through a two-epoch bathymetric reassessment to measure hypsographic change and assess implications for water-supply reliability. In 2025, a high-resolution bathymetric survey was performed in accordance with IHO S-44 standards using Trimble RTK-GNSS and ADCP depth soundings, achieving a crossline mean absolute deviation of ≤0.12 m and a vertical RMSE of ≤0.05 m. Results were compared with the 1982 design dataset to evaluate elevation-banded losses. At NTWL (170.5 m A.M.S.L.), live storage capacity decreased from 615.00 to 344.15 MCM (−44.0%), while water spread contracted from 106.36 to 67.02 km² (−37.0%). Over 60% of storage loss occurred on depositional benches between 161 and 167 m, increasing the elevation–capacity gradient and intensifying volumetric penalties relative to areal shrinkage (elasticity ≈1.19). Multi-season analyses of particle-size distribution confirmed silty clays and clay loams dominate mid-bench and outflow zones, while sandy sediments at the right bank served as coarse-textured controls. Geochemical assays revealed moderate enrichment of Pb (16–27 mg/kg), Cu (12–19 mg/kg), and Zn (63–72 mg/kg) in fine-grained benches, with low hydrocarbon residues (ΣPAHs ≤0.8 mg/kg, ΣPCBs ≤0.04 mg/kg). A preliminary cost–benefit analysis indicated hydraulic sluicing ($0.5–1.5/m³) to be more feasible than mechanical dredging ($3–8/m³), with catchment stabilisation offering benefit–cost ratios of 1:1.3–2.0. Recommended monitoring includes resurveys every 5–10 years, event-triggered campaigns following ≥Q10 floods or >5% shoreline change, and seasonal PSD and geochemistry sampling.

Bathymetric surveys of two small lakes in Newfoundland, located in different environments and separated by hundreds of kilometres, were carried out using two different survey methods—ground penetrating radar (GPR) and sound navigation and ranging (sonar). The different structures of these two disparate ponds were found to be related to the differing geology and degrees of anthropogenic influence at the two locations. In addition, the study outlined the strengths and limitations of the two survey methods. Tipping’s Pond, on the outskirts of the town of Corner Brook in western Newfoundland, is a sinkhole in a popular recreation area. It is roughly square with an area of 1.6 km2 and is slightly salty, making it largely impenetrable by radar. Bathymetric surveys with a salinity-impervious fish-finder sonar system revealed Tipping’s Pond to be bowl-shaped and more than 25 m deep in the centre. Grassy Pond, 3 km inland from the Trans-Canada Highway in eastern Newfoundland, is within an undeveloped area accessible by snowmobile in the winter. It has an irregular, elongated shape 1.2 km2 in area and is very fresh. As well as determining the bathymetry, GPR was able to determine the depth of a soft sediment layer overlying till, and to image structures within the soft sediments. The top of the sediment layer is undulating and shallow (<2.9 m deep) whereas the base of the sediments overlies sub-basins about 8 m deep.

The volcanic lakes of Bali, such as Batur, Beratan, Buyan, and Tamblingan, play a critical role in water provision, ecosystem services, and socio-cultural values. In addition to serving as raw water sources for irrigation, domestic use, dan tourism, these lakes also carry important conservation and spiritual functions embedded in Balinese cultural life. However, land-use changes, agricultural intensification, and tourism development within their catchments have accelerated erosion and sediment transport into the lakes. This sediment accumulation has resulted in lakebed shallowing and reduced storage capacity, thereby threatening the long-term sustainability of their hydrological and ecological functions. This study aims to examine sedimentation processes and potential shallowing through a 2024 bathymetric survey of Bali’s four main volcanic lakes. The analysis indicates an increase in sediment deposition between 2023 and 2024, with average thicknesses of 0.12 m in Lake Batur, 0.24 m in Lake Beratan, 0.49 m in Lake Buyan, and 1.56 m in Lake Tamblingan. Among these, Lake Tamblingan recorded the greatest thickness of sediment accumulation. These findings highlight the importance of regular monitoring of lake conditions. Bathymetric analysis can serve as a scientific basis for technical conservation planning, including dredging, upstream erosion control, and zoning of lake areas according to their vulnerability to sedimentation.

The Poechos Reservoir, which began operations in 1976 with an initial water storage capacity of 885 hm3, has undergone severe sedimentation. By 2018, bathymetric surveys from the Chira–Piura Special Project (PEChP), the institution responsible for its operation and maintenance, reported an accumulated volume of 520 hm3, representing a 58.8% loss in storage. This situation raises concerns about long-term water security and sediment source dynamics. The present study aims to quantify the total mass and annual origin of sediment inflows to the reservoir. The study analyzed the Transboundary Catamayo–Chira Basin for the period 2001–2017, selected according to data availability: MODIS vegetation cover mosaics (available since February 2000), PISCOp precipitation datasets from SENAMHI (available until mid-2018), and annual reservoir bathymetries from PEChP (available until 2018). Sediment supply was estimated using the sediment delivery ratio (SDR) model implemented in the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST 3.13.0) software and validated against bathymetric measurements. Results show that the basin supplies an annual median of 6.91 × 106 t yr−1, a value consistent with 6.53 × 106 t yr−1, derived from bathymetric data for the same period. Eastern sub-basins dominated contributions, with Macará (2.34 × 106 t yr−1), Quiroz (1.98 × 10⁶ t yr⁻¹), and Catamayo (1.50 × 106 t yr−1) accounting for 84.3% of the load, while Alamor and La Solana contributed only 0.65 and 0.18 × 106 t yr−1, respectively. However, the 2017 El Niño–Southern Oscillation (ENSO) event altered this pattern: basin-wide supply surged to 34.92 × 106 t, with western sub-basins contributing more than half of the total, including a 57-fold increase from La Solana. These findings demonstrate that sediment supply is strongly controlled by climatic variability, with ENSO events shifting the spatial dominance of sediment sources. The predominance of eastern sub-basins under normal conditions contrasts with the episodic but extreme contributions from western sub-basins during El Niño. This highlights the need for adaptive management strategies that combine vegetation cover restoration with basin-wide monitoring, especially in semi-arid Andean systems where reservoir capacity is critical for water security.

Reconstruction of microtia remains a complex challenge in plastic surgery, particularly in achieving both aesthetic and functional outcomes. Since the introduction of costal cartilage grafting, various techniques have evolved, including the Nagata method. However, limitations such as rigidity of the framework, high cartilage volume requirement, and complications from temporoparietal fascia (TPF) flaps persist. The authors present our refined technique for lobule-type microtia reconstruction, now known in Japan as the Yotsuyanagi Method. This approach emphasizes a hybrid cartilage framework that combines costal cartilage with elastic remnant cartilage to improve flexibility, especially in the tragus and antitragus. Key surgical refinements include defined allocation of costal cartilage segments to auricular components, use of nylon sutures instead of stainless steel wire, and a two-step procedure allowing delayed trimming of excess skin. Auricular elevation is enhanced through the use of banked support cartilage and superficial mastoid fascia, avoiding the need for TPF flaps. This technique allows for the reconstruction of a symmetric, three-dimensional auricle with improved compatibility for earphones and hearing aids. The hybrid cartilage design maintains elasticity without compromising structural integrity. Operation time is reduced, long-term complications such as wire exposure are minimized, and secondary revisions are simplified. Aesthetic results, including sufficient conchal depth and natural contour, have been consistently favorable. Our evolved method for microtia reconstruction offers significant advantages over traditional approaches by reducing patient morbidity, enhancing postoperative outcomes, and achieving a more natural auricular form. Ongoing refinement and long-term evaluation will further optimize results for patients undergoing auricular reconstruction.

Dams and small reservoirs are important water infrastructures to conserve water, and protecting downstream areas from adverse impacts of floods and droughts. However, reservoir sedimentation has become an important issue all over the world as it reduces storage capacity and shortens the useful life. The present study was carried out on Saleran reservoir situated in Shivalik foot-hills of northwest India using 18 multi-spectral multi-date satellite imageries of Landsat 8 OLI (Operational Land Imager) sensor and geographic information system. Reservoir water surface areas and storage capacity at different water elevations were estimated for the year 2016-2020. The results of the study indicated that Saleran reservoir is losing its storage capacity at a rate of 0.72%, annually due to siltation at the rate of 23.39 Mg ha-1 y-1. The reservoir lost 35.81 ha m (17.9%) of live storage capacity over a period of 25 years (1995-2020) due to sedimentation. The elevation-area-capacity curves have been updated for future use in estimating correct volume of water available in the reservoir at different elevations. The results obtained using geospatial technique showed an agreement with those of bathymetric survey. The study indicated an urgent need to plan and execute suitable conservation measures in the catchment to reduce the amount of sediment inflow to the Saleran reservoir for having long trouble-free service life. The findings of the study would help the planners and managers involved in planning, design, and operation of small multi-purpose reservoirs under similar climatic and topographic conditions all over the world.

The accurate monitoring of short-term bathymetric changes in shallow waters is essential for effective coastal management and planning. Machine Learning (ML) applied to Unmanned Aerial Vehicle (UAV)-based multispectral imagery offers a rapid and cost-effective solution for bathymetric surveys. However, models based solely on multispectral imagery are inherently limited by confounding factors such as shadow effects, poor water quality, and complex seafloor textures, which obscure the spectral–depth relationship, particularly in heterogeneous coastal environments. To address these issues, we developed a hybrid bathymetric inversion model that integrates digital surface model (DSM) data—providing high-resolution topographic information—with ML applied to UAV-based multispectral imagery. The model training was supported by multibeam sonar measurements collected from an Unmanned Surface Vehicle (USV), ensuring high accuracy and adaptability to diverse underwater terrains. The study area, located around Lazarus Island, Singapore, encompasses a sandy beach slope transitioning into seagrass meadows, coral reef communities, and a fine-sediment seabed. Incorporating DSM-derived topographic information substantially improved prediction accuracy and correlation, particularly in complex environments. Compared with linear and bio-optical models, the proposed approach achieved accuracy improvements exceeding 20% in shallow-water regions, with performance reaching an R2 > 0.93. The results highlighted the effectiveness of DSM integration in disentangling spectral ambiguities caused by environmental variability and improving bathymetric prediction accuracy. By combining UAV-based remote sensing with the ML model, this study presents a scalable and high-precision approach for bathymetric mapping in complex shallow-water environments, thereby enhancing the reliability of UAV-based surveys and supporting the broader application of ML in coastal monitoring and management.

Accurate and up-to-date morphometric data on lakes are crucial for hydrological modeling, ecosystem monitoring, and sustainable water resource management. This study presents the first centimeter-scale, high-resolution bathymetric model of Lake Markakol (eastern Kazakhstan), generated using advanced hydroacoustic and geospatial techniques. The primary objective was to reassess key morphometric parameters—surface area, depth, volume, and shoreline configuration—more than six decades after the only existing survey from 1962. High-density depth data were acquired with a Lowrance HDS-12 Live echo sounder, achieving vertical precision of ±0.17 m, and processed using ReefMaster and ArcGIS to produce a three-dimensional, hydrologically correct model of the lake basin. Compared with archival data, results show that while the surface area (455.365 ± 0.005 km2), length (38.304 ± 0.002 km), and width (19.138 ± 0.002 km) have remained stable, the maximum depth is lower (24.14 ± 0.17 m vs. 27 m), and the total water volume is slightly higher (6.667 ± 0.025 km3 vs. 6.37 km3). These differences highlight both the limitations of historical lead-line surveys and the enhanced accuracy of modern hydroacoustic and GIS-based methods. The workflow developed here is transferable to other remote alpine lakes, providing an invaluable baseline for limnological research, ecological assessment, hydrodynamic modeling, and long-term water resource management strategies in data-scarce mountain regions.

Accurate forecasting of river siltation is essential for ensuring inland waterway navigability and guiding sustainable sediment management. This study investigates the downstream reach of the Shihutang navigation power hub along the Ganjiang River in Jiangxi Province, China, an area characterized by pronounced seasonal sedimentation and hydrological variability. To enable fine-scale prediction, we developed a data-driven framework using a random forest regression model that integrates high-resolution bathymetric surveys with hydrological and meteorological observations. Based on the field data from April to July 2024, the model was trained to forecast monthly siltation volumes at a 30 m grid scale over a six-month horizon (July–December 2024). The results revealed a marked increase in siltation from July to September, followed by a decline during the winter months. The accumulation of sediment, combined with falling water levels, was found to significantly reduce the channel depth and width, particularly in the upstream sections, posing a potential risk to navigation safety. This study presents an initial, yet promising attempt to apply machine learning for spatially explicit siltation prediction in data-constrained river systems. The proposed framework provides a practical tool for early warning, targeted dredging, and adaptive channel management.

This study introduces a novel methodology for assessing ice-jam flood hazards along river channels. It employs empirical equations that relate non-dimensional ice-jam stage to discharge, enabling the generation of an ensemble of longitudinal profiles of ice-jam backwater levels through Monte-Carlo simulations. These simulations produce non-exceedance probability profiles, which indicate the likelihood of various flood levels occurring due to ice jams. The flood levels associated with specific return periods were validated using historical gauge records. The empirical equations require input parameters such as channel width, slope, and thalweg elevation, which were obtained from bathymetric surveys. This approach is applied to assess ice-jam flood hazards by extrapolating data from a gauged reach at Fort Simpson to an ungauged reach at Jean Marie River along the Mackenzie River in Canada’s Northwest Territories. The analysis further suggests that climate change is likely to increase the severity of ice-jam flood hazards in both reaches by the end of the century. This methodology is applicable to other cold-region rivers in Canada and northern Europe, provided similar fluvial geomorphological and hydro-meteorological data are available, making it a valuable tool for ice-jam flood risk assessment in other ungauged areas.

Recent archaeological discoveries across the Aegean, Cyprus, and western Anatolia have renewed interest in pre-Neolithic seafaring and early island colonization. However, the environmental contexts that support such early coastal occupations remain poorly understood, largely due to the submergence of Pleistocene shorelines following post-glacial sea-level rise. This study addresses this gap through an integrated geoarchaeological investigation of the pre-Neolithic site of Ouriakos on Lemnos Island, northeastern Aegean (Greece), dated to the mid-11th millennium BCE. By reconstructing both the terrestrial and submerged paleolandscapes of the site, we examine ecological conditions, resource availability, and sedimentary processes that shaped human activity and site preservation. Employing a multiscale methodological approach—combining bathymetric survey, geomorphological mapping, soil micromorphology, geochemical analysis, and Optically Stimulated Luminescence (OSL) dating—we present a comprehensive framework for identifying and interpreting early coastal settlements. Stratigraphic evidence reveals phases of fluvial, aeolian, and colluvial deposition associated with an alternating coastline. The core findings reveal that Ouriakos was established during a phase of environmental stability marked by paleosol development, indicating sustained human presence. By bridging terrestrial and marine data, this research contributes significantly to the understanding of human coastal mobility during the Pleistocene–Holocene transition.

Abstract. The introduction of leaky wooden dams (or engineered log jams or LDs) into river corridors in low-order steams in upper catchments has recently become a popular form of natural flood management, particularly in NW Europe. LDs are designed to emulate processes such as those of naturally occurring large wood in river systems, aiming to reduce downstream flood risk through the attenuation of water during higher flows, decreasing in-channel velocities and increasing channel–floodplain connectivity. LDs effectively act as channel roughness agents that disrupt the fluvial and hydrological regime and attenuate the peaks in high river flows, thus mitigating downstream flood risk. Despite their widespread installation, there is a paucity of data and understanding concerning the longer-term fluvial geomorphological response to LD installation. Here we present a detailed quantification of both the geomorphic and sedimentary response to the installation of two LDs in a catchment in Dalby Forest (North Yorkshire, UK) using high-resolution terrestrial laser scanning and detailed bathymetric surveys over a 2.5-year period. This period included two major storms with a recurrence interval of 3.9 and 3.4 years, and a further four smaller storm events (1.22–2.3 years). Results show that when LDs are engaged by the river flow, local topographic complexity significantly increases as sediment transport pathways are perturbed. The flow field complexity additionally changes the channel bed grain-size distribution, with trends of fining upstream and coarsening downstream of the structure observed. The LD was also observed to generate scour pools downstream of the structure, and coarsen the armour layer through the winnowing of fines. Monthly observations reveal that channel topography and bed sediment patterns self-organise in response to sustained low flows and are perturbed by higher flow events. The findings highlight how frequent monitoring of different LD designs and structures under various flow conditions is vital to understand their longer-term impacts. Moreover, it is critical that such observations are extended over longer-term periods in order to fully assess the efficacy of the structures as the channels respond to installations and the evolution of the geomorphic response. Finally, additional work is also required to better consider how individual LDs influence local geomorphology and alter sediment transport connectivity throughout the catchment.

Extreme surface winds and wave heights of tropical cyclones (TCs)—pose serious threats to coastal community, infrastructure and environments. In recent decades, progress in numerical wave modeling has significantly enhanced the ability to reconstruct and predict wave behavior. This review offers an in-depth overview of TC-related wave modeling utilizing different computational schemes, with a special attention to WAVEWATCH III (WW3) and Simulating Waves Nearshore (SWAN). Due to the complex air–sea interactions during TCs, it is challenging to obtain accurate wind input data and optimize the parameterizations. Substantial spatial and temporal variations in water levels and current patterns occurs when coastal circulation is modulated by varying underwater topography. To explore their influence on waves, this study employs a coupled SWAN and Finite-Volume Community Ocean Model (FVCOM) modeling approach. Additionally, the interplay between wave and sea surface temperature (SST) is investigated by incorporating four key wave-induced forcing through breaking and non-breaking waves, radiation stress, and Stokes drift from WW3 into the Stony Brook Parallel Ocean Model (sbPOM). 20 TC events were analyzed to evaluate the performance of the selected parameterizations of external forcings in WW3 and SWAN. Among different nonlinear wave interaction schemes, Generalized Multiple Discrete Interaction Approximation (GMD) Discrete Interaction Approximation (DIA) and the computationally expensive Wave-Ray Tracing (WRT) A refined drag coefficient (Cd) equation, applied within an upgraded ST6 configuration, reduce significant wave height (SWH) prediction errors and the root mean square error (RMSE) for both SWAN and WW3 wave models. Surface currents and sea level variations notably altered the wave energy and wave height distributions, especially in the area with strong TC-induced oceanic current. Finally, coupling four wave-induced forcings into sbPOM enhanced SST simulation by refining heat flux estimates and promoting vertical mixing. Validation against Argo data showed that the updated sbPOM model achieved an RMSE as low as 1.39 m, with correlation coefficients nearing 0.9881.