Benthic Terrain Modeler Research Articles

A Comparative Crash-Test of Manual and Semi-Automated Methods for Detecting Complex Submarine Morphologies

Multibeam echosounders provide ideal data for the semi-automated seabed feature extraction and accurate morphometric measurements. In this study, bathymetric and raw backscatter data were initially used to manually delimit the reef morphologies found in an insular semi-enclosed gulf in the northern Aegean Sea (Gera Gulf, Lesvos Island, Greece). The complexity of this environment makes it an ideal area to “crash test” (test to the limit) and compare the results of the delineation methods. A large number of (more than 7000) small but prominent reefs were detected, which made manual mapping extremely time-consuming. Three semi-automated tools were also employed to map the reefs: the Benthic Terrain Modeler (BTM), Confined Morphologies Mapping (CoMMa), and eCognition Multiresolution Segmentation. BTM did not function properly with irregular reef footprints, but by modifying both the bathymetry and slope, the outcome was improved, producing accurate results that appeared to exceed the accuracy of manual mapping. CoMMa, a new GIS morphometric toolbox, was a “one-stop shop” that, besides generating satisfactory reef delineation results (i.e., detecting the same total reef area as the manual method), was also used to extract the morphometric characteristics of the polygons resulting from all the methods. Lastly, the Multiresolution Segmentation also gave satisfactory results with the highest precision. To compare the final maps with the distribution of the reefs, mapcurves were created to estimate the goodness-of-fit (GOF) with the Precision, Recall, and F1 Scores producing values higher than 0.78, suggesting a good detection accuracy for the semi-automated methods. The analysis reveals that the semi-automated methods provided more efficient results in comparison with the time-consuming manual mapping. Overall, for this case study, the modification of the bathymetry and slope enabled the results’ accuracy to be further enhanced. This study asserts that the use of semi-automated mapping is an effective method for delineating the geomorphometry of intricate relief and serves as a powerful tool for habitat mapping and decision-making.

Digital topographic analysis and lineament interpretation south of the Lena Delta, North Siberia: Landscape expression of its tectonic activity

This study applies semi-automated techniques to analyze the landforms, morphostructure, and geology of the Kharaulakh and Chekanovsky sectors, south of the Lena Delta, northern Siberia. High-resolution data, including TanDEM-X 30 m spatial resolution Digital Elevation Models (DEM), 2 m spatial resolution ArcticDEM Digital Surface Models (DSM), and Sentinel-2 satellite imagery, serve as the basis for the analysis. Digital terrain classification and identification of tectonic lineaments are performed using the Benthic Terrain Modeler (BTM) and Linear Extraction (LINE) algorithm, respectively. Additionally, a hypsometric analysis is conducted to assess areas of potential neotectonic activity. 873 lineaments are identified, primarily in NE-SW and E-W orientations. NW-SE lineaments perpendicular to the lithological and fold belt strikes in the Kharaulakh Ridge suggest inheritance from original depositional settings or later compressional tectonics, now appearing as valleys and weak zones facilitating erosion and river incision. Longer N-S or NNW-SSE lineaments in the Kharaulakh Sector are associated with thrust sheets of the Verkhoyansk fold-and-thrust belt and Cenozoic graben structures linked to the formation of the Laptev Sea Rift System and ongoing regional deformation. The Chekanovsky Sector, marked by epiplatform blocks and hills, presents a dissected plateau with steep valleys. Here, high hypsometric integral values are attributed to compression and uplift near the southwestern boundary of the Laptev Sea Microplate.

Deep-sea benthic structures and substrate types influence the distribution of functional groups in the Wallaby-Zenith Fracture Zone (East Indian Ocean)

Three-dimensional deep-sea structures enhance substrate complexity and can shape numerous ecological hotspots that play critical roles in the diversity and distribution of benthic faunal assemblages. The characteristics of these features are not fully understood due to the logistical challenges of exploring at great depths and remote locations. One such deep-sea feature, the Wallaby-Zenith Fracture Zone (WZFZ) located in the East Indian Ocean, was mapped using a full-ocean depth multibeam echosounder system. Additionally, twelve baited landers and five crewed submersible dives were conducted in water depths between 4709 and 6591 m. We use seafloor bathymetry, bathymetric derivatives and video footage from the submersible dives to characterise the benthic structures, substrate types, habitat diversity, and the distribution of associated functional groups of megafauna for the WZFZ. The Benthic Terrain Modeler toolbox was used as an initial semi-automated step to generate benthic structural classes, which were further characterized through the inclusion of bottom salinity and temperature data collected by the scientific landers and integrated with the observations of seafloor substrate from the submersible video footage. This resulted in identification of nine benthic habitat classes characterised by unique seafloor morphological structure and substrate texture. A polymetallic nodule field, a possible extension of the previously reported Cape Leeuwen nodule field, was also observed along submersible transects conducted on the slopes of the WZFZ. The distribution and diversity of the functional megafauna groups observed are influenced by the deep-sea benthic habitats, defined by seafloor structures and substrate heterogeneity, especially the presence of hard substrates such as outcropping bedrock and polymetallic nodules within the WZFZ.

High-resolution optical remote sensing geomorphological mapping of coral reef: Supporting conservation and management of marine protected áreas

Brazilian corals are unique ecosystems with high endemism and low functional redundancy. Hence, mapping its geomorphology is an important step to inferring analyzes on benthic habitats. We observe several difficulties during this mapping of coastal areas by remote sensing and a lack of fine-scale depth data for reef areas in Brazil. The present study aims to present the bathymetry extracted by satellite imagery in murky waters using a mosaic of Sentinel-2 images in Google Earth Engine (GEE) calibrated with field samples. We used the satellite extracted DBM to map the bottom geomorphology through BTM (Benthic Terrain Modeler). We then present the first detailed geomorphological map for the largest marine coastal protected area in Brazil- MPA Costa dos Corais. The geomorphological raster was differentiated into seven classes: Flat Plains, Depressions, Gentle Slopes, Slopes, Terrestrial Reef Flat, Reef Flat, and Crest. Altogether, we estimate >275 km2 of area representing reef structures (coral reef or beachrocks), or about 48% of the total MPA area. Mapping coral reefs can contribute to conservation, particularly in selecting areas for in situ monitoring activities and in prioritizing the application of remedial actions in the event of environmental disasters or threats to coral health, such as oil spills and bleaching episodes. Our findings encourage the applicability of these methodologies in other reef areas and collaborate for the management and monitoring of marine protected areas. In addition, all mapping is available online for any user.

Mapping reef terrain roughness and benthic habitat complexity in the Pamegaran Island, Kepulauan Seribu National Marine Park

The formation of coral cays in the Kepulauan Seribu Marine Parks, Jakarta Special Capital Region, is the result of patch reef evolution which linked to the geology of sediment accretion, including the ecology of coral growth and competition of benthic community. This study aims to map the level of reef complexity in Pamegaran Island using Benthic Terrain Modeler. Field observation to monitor benthic communities in four stations at 3- and 5- meter depth was combined with SPOT-7 image processing to evaluate in situ rugosity, 3-dimensional bathymetry and benthic habitat classification. The results of this study revealed low degree of terrain complexity as results of habitat degradation and dominant benthic class of sand. Classification of reef benthic habitat resulted in five classes, namely sand (Sd= 126.65 ha), seagrass (Sg= 35.29 ha), bare rubble (Rb= 32.68 ha), reefs dominated by dead corals (DC=3.16 ha) and dead coral with algae (DA= 20.50 ha); with 67.21% score of overall accuracy (OA). In situ rugosity at 5 m was higher than 3 m, as result of higher coverage of live corals particularly in the east site. Similar profile was shown for rugosity index, which reflects ratio between surface to planar area and seafloor gradient along the reef slope. Finally, positive correlation between reef surface and in situ rugosity implies the importance of live coral communities in supporting complex terrain and benthic habitat in the patch reef environment.

Habitat and benthic fauna of the Wallaby-Cuvier escarpment, SE Indian ocean

The Wallaby-Cuvier Escarpment is a 700 km long, NW-SE trending linear geological feature that marks the southern boundary of the Cuvier Plateau. The Plateau rises from the adjacent 5500 m deep abyssal plain to a topographical high of 3000 m, approximately 450 km off the coast of Western Australian. In 2021, a 50 km long segment of the escarpment, covering an area of 1700 km2, was mapped by a high-resolution full-ocean depth multibeam echosounder. The habitat of the study area was explored during two video surveys undertaken using the crewed submersible Limiting Factor. Using Benthic Terrain Modeler (BTM), we classified the seabed into five geomorphological classes; flat plains, depressions, broad slopes, steep slopes, and crest. Video footage was used to classify habitat types and to record benthic megafauna occurrences which revealed highly heterogeneous and rapidly changing habitats. Six habitats were proposed based on the nature of geomorphology, slope, and substrate textures. A total of 202 organisms comprising 52 morphotaxa were scored during 198 min of survey that included at least eight phyla and 29 families. Despite a high number of morphotaxa, the total abundance of organisms is considered low which we attribute to oligotrophic surface waters. However, the distribution of organisms and their feeding strategies were well-aligned with habitat type. This study documents faunal distribution and habitat diversity of a rarely explored type of deep-sea geomorphological feature, and in a largely unexplored area and depth of the Indian Ocean.

High resolution geomorphological classification of benthic structure on the Western Pacific Seamount

The benthic structure of seamounts is critical for understanding the ecological environment and for assessing the influence of resource exploitation. However, the characteristics of the benthic structure of the seamount, especially for guyot, are still far from being clearly understood. For the first time, we carried out detailed hydroacoustic mapping in conjunction with surficial sediment sampling and underwater video recording to investigate the geomorphical and biological characteristics of Pallada Guyot in the Western Pacific Ocean (WPO). We utilized the Benthic Terrain Modeler (BTM) as an initial step to describe the detailed benthic structures and then classify the textural seabed according to backscatter images and sediment samples. We further discussed the relationship between geomorphology and the occurrence of benthic megafauna from video images. The results revealed that 13 classes of benthic structural zones were differentiated, and the dominant zones were flat abyssal plains, where the number and size of megafauna were smaller than those on the flank and flat-topped areas. The second most notable feature is the flat top, where sea cucumbers, starfish, fish, and shrimp have higher biomass and diversity. In the flank region, which is characterized by complex and extensive current-scoured ridges and depressions, sponges and corals are distributed in high-relief bedrocks. We also found that the maximum water depth where cold-water corals develop is 2,250 m. The sponge grounds appear in a marked bathymetric belt (1,800–2,150 m), which is shallower than that on a tropical seamount (2,500–3,000 m) located in the northeastern Atlantic. The findings of this study contribute to understanding the geomorphological drivers and biogeography of WPO seamounts and provide a reference for identifying priority areas for improved marine mineral planning in WPO areas.

Geomorphological classification of benthic structures of Kaledupa Atoll Wakatobi National Park, Indonesia

Abstract. Setiawan A, Siregar VP, Susilo SB, Mardiastuti A, Agus SB. 2022. Geomorphological classification of benthic structures of Kaledupa Atoll Wakatobi National Park, Indonesia. Biodiversitas 23: 3784-3792. Geomorphological mapping is one solution to understanding the complexity of the seabed pattern. This research aims to map the benthic structure of Kaledupa Atoll using the Remote Sensing and Geographic Information System with the Benthic Terrain Modeler (BTM) extension. The data used is in situ bathymetry data using Mapsounder 585 and Sentinel 2A satellite image data downloaded for free. BTM is a technique for examining benthic habitat and shallow water geomorphology. BTM was used to analyze integrated depth data to determine the bathymetric position index (BPI), slope, and classification of reef geomorphological structures. Thirteen structural classes of habitat geomorphology resulting from this research are Flat plain with the largest area of ??17142.35 ha, and the class with the smallest area is Crevices class, with narrow gullies rock outcrops 1.64 ha. While the other classes in a row are Broad slope 9104.53 ha; Flat ridge tops, upper slopes 4262.67 ha; Current scoured depressions on a slope 3420.98 ha; Narrow depressions at the base of rock outcrops 2348.20 ha; Rock outcrop highs, narrow ridges 1792.45 ha; Local ridges, boulders, pinnacles on slopes 879.29 ha; Scarp, cliff or small local depressions on a slope 703.02 ha; Local ridges, boulders, pinnacles on broad flat 490.17 ha; Local depressions, current scoured on flat 416.39 ha; Local ridges, boulders, pinnacles on broad depressions 16.63 ha; and Steep slopes 2.88 ha.

Mapping of shallow water bathymetry and reef geomorphology using Sentinel-2 satellite imagery in Genteng Besar and Genteng Kecil Island, Kepulauan Seribu

Information on seafloor characteristics is one of the essential variables in coastal management and marine ecosystems. Application methods in remote sensing technology to study about characteristics of shallow waters have continuously been done. This research consists of two parts: an estimation of depth using Sentinel 2B satellite imagery with the Lyzenga algorithm and geomorphological classification of the benthic area using the Benthic Terrain Modeler (BTM) approach. BTM is a method to analyze benthic habitat and shallow water geomorphology. Integrated Depth data were analyzed using BTM to obtain bathymetric position index (BPI), slope, and classification of reef geomorphological structures. The resulting BPI value range is directly proportional to the given spatial area (scale factor). The slope is ranged between 0.01° – 19.24°, while optimum depth estimation is applicable until 10-meter. The values of BPI and slope were used as variables to classify the geomorphology of shallow water benthic areas based on the previous classification dictionary. Six geomorphological classes resulting from this study are Back Reef, Deep Depression, Depression, Lower Bank Shelf, Mid-Slope Ridges, and Reef Crest.

High-resolution optical remote sensing for coastal benthic habitat mapping: A case study of the Suape Estuarine-Bay, Pernambuco, Brazil

The benefits of high resolution remote sensing techniques and data for the mapping of coastal environments include their ability to capture the spatial variability of the rich and diverse sedimentary landforms and habitats of coastal systems as well as gather and manage different types of data and information using the same platform for multi-scale and multi-layer analysis. This work analyses the efficacy of high resolution satellite imagery for mapping benthic habitat and the seascape characteristics of a coastal lagoon (Suape Bay - 40 km south of Recife, Pernambuco, Brazil) subjected to high anthropogenic impact and exposed to different conditions of tides, suspended sediment regime, and wave dynamics, using different types of processing and classification methods. We analyzed two World View 2 images acquired in 2010 and 2015 in similar tidal conditions and low water turbidity. Preprocessing included the application of radiometric and atmospheric correction, sunglint removal, and land/sea areas masking. To extract the depth information, a Band Ratio and Simple Radiative Transfer Model were employed. The model was corrected and calibrated by using a set of 150 control points collected by echo sounding surveying. A benthic terrain model was developed to identify and map topographic features at broad and fine scales. Supervised Pixel and Object-Based classification methods were applied to visible bands of WV2 and bathymetric data to produce benthic habitat maps of the lagoon area. The analyses were validated by ground truthing based on bottom sediment sampling, underwater photographs, and side scan sonar surveys.

Geomorphometric Seabed Classification and Potential Megahabitat Distribution in the Amazon Continental Margin

The geomorphometry of the of the Amazon Continental Margin was analyzed using the Benthic Terrain Model, a spatial analysis technique that defines physical habitat classes based on seafloor relief heterogeneities. A compilation of available bathymetric and novel multibeam data was used to define the megahabitats, with emphasis on shelf-slope transitions and shelf-edge reefs. The analyses revealed a complex mosaic of benthic megahabitats associated to short and long-term geologic and sedimentary evolution of the margin. The continuous terrigenous sediment input is associated to a smooth muddy deposit along the inner and mid shelf (Regular Continental Shelf megahabitat). The portions of the shelf that are less influenced by riverine sediment accumulation are rougher and characterized by either sand (Irregular Sand Continental Shelf megahabitat) or carbonate-dominated bottom (Irregular Reef Continental Shelf megahabitat). The most notable difference in terms of morphometric analysis and megahabitats can be observed along the outer shelf and shelf-break. The Shelf-Slope Transition megahabitat is marked by ridges in the shelf break and by a more acute depth gradient that forms a distinct outer shelf edge. Three different alongshore sectors were explored in order describe the heterogeneous megahabitat mosaic in terms of slope and bottom morphology. The western-most sector (S3) is remarkable due to an indistinct separation between ridges and the outer shelf edge, as well as for presenting reefs with up to 20 m high, between 110 and 210 m water depths. The central sector (S2) presents no shelf-break and lacks ridges, a feature that is associated with the long-term sediment accumulation (Amazon Fan). The southern-most sector (S1) does not present an outer shelf edge, only ridges, and a number of shelf-incised channels, comprising a sediment bypass across the shelf, and carbonate sedimentation. The continental slope is divided into a Featured Slope megahabitat with numerous canyons and ravines, and areas that lack such features, including a Shallow Gentle Slope megahabitat, a Steep Slope megahabitat and a Deep Gentle Slope megahabitat. Our results confirm the usefulness of geomorphometric analyses to define benthic megahabitats and can be used as a starting point in a much-needed marine spatial planning process for the area.

The use of Benthic Terrain Modeler (BTM) in the characterization of continental shelf habitats

We applied a combined approach of benthic terrain modelling with sediment type distribution, using regional available data sets in order to map the distribution of seabed physical habitats along the Espirito Santo Continental Shelf, Brazil. The Benthic Terrain Modeler (BTM) was used to define benthic terrain classes, which were combined with ground truth data (sediment samples and seabed images) to produce physical habitats (seascapes). Eight BTM classes were defined: flat bottom, rough, depression, valley flank, valley bottom, shelf break, crests, and deep crests. The combination of the BTM classes with sediment distribution produced 17 types of physical habitats. Analysis showed that shelf morphology controls the pattern of habitat distribution, combined with two major sedimentary processes: riverine sediment input and carbonate sedimentation. Seven types of physical habitats area associated with the flat bottom morphometric class, and five types of physical habitats are associated with rough/irregular morphometric classes. These are the two main broad categories observed along the shelf, when combined with the presence of rhodoliths. Shelf-incised valleys, combined with rhodolith beds, are the most conspicuous seascape along the ESCS. These seascapes add slope and roughness to the shelf seabed, producing great morphological complexity and potentially supporting diverse benthic communities.

Reef Mapping Using Different Seabed Automatic Classification Tools

There is a great demand to develop new acoustic techniques to efficiently map the seabed and automate the interpretation of acoustic, sedimentological, and imaging data sets, eliminating subjectivity. Here, we evaluate the potential, limitations and complementariety of distinct supervised and automatic classification techniques in the mapping of reefs by comparing these results with a reference map. The study was carried out in the Abrolhos Continental Shelf (Eastern Brazilian Continental Margin) using a multibeam echosounder and side scan sonar (SSS) dataset. Two automatic supervised techniques were applied. A reference map was derived by detailed manual interpretation carried out by three experts. The two supervised classification techniques were: benthic terrain modeler (BTM), a morphometric classification with focus on spatial analyses of the bathymetric grid derivatives, and object-based image analysis (OBIA), a segmentation applied to the backscatter data from the SSS mosaic. Both automatic techniques obtained similar values of reef coverage area, but overestimated the reef area when compared with the reference map. The agreement between BTM and OBIA results and the reference map was 69% and 67%, respectively. Disagreement was mainly due to quantity of reef (both methods over-estimated reef), while the disagreement in spatial allocation was relatively low, it indicates that both methods are reasonable representation of the spatial patterns of reef. Efficient mapping of reef in the wider area of the Abrolhos Continental Shelf will be best achieved by a further development of automatic methods tested against reference maps obained from representative areas of the seabed. By combining the results of the two automatic methods, it was possible to create an ensemble map, which achieved better agreement with the reference dataset.

Geodiversity as an indicator to benthic habitat distribution: an integrative approach in a tropical continental shelf

Marine habitat mapping provides essential information for environmental management and design of marine reserves. In tropical regions, particularly along the Brazilian coast, the spatial variability of marine habitats is poorly known. The aim of this study is to evaluate the geodiversity of the region as an indicator to benthic habitat distribution, applying an integrative approach utilizing existing broad-scale bathymetric and seafloor geological data sets. A digital bathymetric model (DBM) of the Pernambuco Continental shelf (PCS) was generated at 80 m resolution from available bathymetric data. Through the benthic terrain model (BTM), DBM derivatives and the benthic structures were generated. These structures were combined with the textural seabed classification using tools in ArcGIS™ 10.5 Spatial Analyst to identify 22 seabed geomorphic features, including a submarine canyon confirmed around 8°20′S. These geomorphological features describe the surficial characteristics of the seafloor, providing the baseline for subsequent habitat-mapping studies, and can therefore be considered a potential habitat map. Three profiles taken to describe the cross-shelf seafloor environment (North, Center, and South) extracted from interpolated seabed geomorphological map revealed that sediment grain size becomes coarser from inshore to offshore, with predominantly sand and gravel sediment grain sizes. Overall, these results indicated a great potential for PCS due to the geodiversity present in the area, which leads to a higher biodiversity as well. Based on that, the central portion of PCS is suggested as a priority area for conservation because it was the most geomorphologically diverse. These terrain features influence the environmental conditions, such as currents, waves, nutrients, and other oceanographic parameters, which results in high diversity of benthic habitats in the region. This study presents a first step in characterizing the geomorphology of PCS by using reliable, standardized data.

A preliminary study on spatial assessment using conservation metrics for intertidal oyster reefs at the Hab River mouth in Pakistan

The oyster reefs in Pakistan are on the verge of extinction as a consequence of environmental and anthropogenic factors. A qualitative survey of oyster reef habitat was conducted from March-2017 to February-2018 in the Hab River Delta along the Balochistan coast (Arabian Sea), Pakistan. A combination of field survey and Geographical Information System (GIS) based approach (reef categorization, universal metrics and habitat suitability analysis), universal environmental variables, restoration goal-based metrics, sounding, condition indices, grain size composition and oyster spat-fall were determined for planning future oyster reef restoration efforts. The reefs were categorized into three main groups as dispersed, patch and continuous on the basis of fragmented spatial geometry. Dispersed reefs were more numerous than continuous and patch categories. The differences between morphometric measurements and density of oysters amongst reefs types were statistically insignificant. Habitat suitability analysis was done by ‘Benthic Terrain Modeler’ using ArcGIS software. The moderate, positive values of Bathymetric Position Index (BPI) of the oyster reef indicate an area of high or open slope with sea bottom (-2 to 6). The area of reef location shows high to moderate values of rugosity (0.7 to 0.9), indicates good to intermediate conditions; whereas, the aspect analysis showed slope orientation in the Northeast direction but mostly flat area. The environmental and restoration goal-based metrics were favorable for oyster growth and survival. The dispersed reefs showed lowest bathymetry points compared to patch and continuous reefs. The values of condition indices reveal not significant difference among reef types (continuous, dispersed and patch). Fine sand has the highest percentage (71%) followed by silt/clay fraction (18%). The higher density and spat size were recorded in monsoon (June to September) season. The current study suggests that the present reefs are viable and have potential for successful restoration and may be converted into a sizeable ecologic sanctuary.

Geomorphological Classification of the Benthic Structures on a Tropical Continental Shelf

Geomorphological research offers a valuable first step to understand the complexity of seafloor patterns that are likely to support particular fauna, thereby providing value for future targeted studies on benthic communities and habitats. The objective of this study is to perform a geomorphological classification for a tropical continental shelf, located in the north of the State of Pernambuco, Brazil, using Benthic Terrain Modeler (BTM), as a first step to characterize benthic habitats. The classification of the seabed is based on the bathymetry, broad-scale and fine-scale BPI (Benthic Positioning Index), seafloor slope, and a decision table containing definitions and thresholds appropriate to the data input. The relationships between morphology and the deposition of surface sediments were also investigated. Results from the BTM analysis revealed eight types of benthic structures: Flat Plains, Depressions, Gentle Slopes, Steep Slopes, Flat Ridge Tops, Rock Outcrop Highs, Local Pinnacles in Depressions and Local Pinnacles on Broad Flats. The results from this study may therefore assist in selecting priority areas to investigate, supporting to better marine spatial planning in the region, and, in the future, collaborate to determine biodiversity patterns in Brazilian waters.

OBIA AND BTM INTEGRATION FOR MAPPING HABITAT COMPLEXITY OF CORAL REEFS ON HARAPAN-KELAPA ISLANDS, KEPULAUAN SERIBU

The habitat complexity is indirectly closely related to reef fish abundance. This study aims to map reefs habitat complexity by integrating object-based image analysis (OBIA) and habitat complexity analysis using benthic terrain modeler (BTM). The datasets used were SPOT-7 imagery and water depth derived from satellite imagery. The ground check was conducted to collect field data used as reference for classification and accuracy assessment of classification results. Classification of SPOT-7 imagery was performed using support vector machines (SVM) algorithm, by grouping shallow waters habitats into 4 classes on level 2 and 3 classes on level 3. Accuracy assessment was done by confusion matrix and resulting overall accuracy (OA) 83.55% for level 2 and 79.66% for level 3. The habitat complexity was analyzed using rugosity analysis method (Arc-Chord Ratio) from benthic terrain modeler (BTM) to obtain rugosity index in reefs area. The substrate covers were obtained from OBIA and complexity of habitats were obtained from BTM, then the overlay result shows varying rugosity index on the reef area in Harapan-Kelapa Islands.
 Keywords: 
 coral reefs, OBIA, habitat complexity, rugosity

Geomorphology and Late Pleistocene–Holocene Sedimentary Processes of the Eastern Gulf of Finland

In 2017, a detailed study of the Eastern Gulf of Finland (the Baltic Sea) seafloor was performed to identify and map submerged glacial and postglacial geomorphologic features and collect data pertinent to the understanding of sedimentation in postglacial basins. Two key areas within the Gulf were investigate using a multibeam echosounder, SeaBat 8111 and an EdgeTech 3300-HM acoustic sub-bottom profiling system. High-resolution multibeam bathymetric data (3-m resolution) were used to calculate aspect, slope, terrain ruggedness and bathymetric position index using ArcGIS Spatial Analyst and the Benthic Terrain Modeler toolbox. These data and resultant thematic maps revealed, for the first time, such features as streamlined till ridges, end-moraine ridges, and De Geer moraines that are being used for the reconstruction of the deglaciation in the Eastern Gulf of Finland. This deglaciation occurred between 13.8 and 13.3 ka BP (Pandivere–Neva stage) and 12.25 ka BP (Salpausselkä I stage). Interpretations of the seismic-reflection profiles and 3D models showing the surfaces of till, and the identification of the Late Pleistocene sediment and modern bottom relief, indicate deep relative water-level fall in the Early Holocene and, most likely, several water-level fluctuations during this time.

Unified Geomorphological Analysis Workflows with Benthic Terrain Modeler

High resolution remotely sensed bathymetric data is rapidly increasing in volume, but analyzing this data requires a mastery of a complex toolchain of disparate software, including computing derived measurements of the environment. Bathymetric gradients play a fundamental role in energy transport through the seascape. Benthic Terrain Modeler (BTM) uses bathymetric data to enable simple characterization of benthic biotic communities and geologic types, and produces a collection of key geomorphological variables known to affect marine ecosystems and processes. BTM has received continual improvements since its 2008 release; here we describe the tools and morphometrics BTM can produce, the research context which this enables, and we conclude with an example application using data from a protected reef in St. Croix, US Virgin Islands.

Modelling Complex Terrain of Reef Geomorphological Structures in Harapan-kelapa Island, Kepulauan Seribu

Detail and accurate information on reef geomorphology structure feature as one significant factor for ecosystem based management of coastal and small islands resources. Most applications of remote sensing and GIS in coral reef studies were directed to map reef substratum and coverage of benthic habitats. The objective of this study was to analyze bathymetric dataset in order to classify reef geomorphology structure in Harapan-Kelapa Island, Kepulauan Seribu. Bathymetric data-set applied were, collated from WorldView-2 satellite and single-beam acoustic remote sensing using Mapsounder 585, examined using ArcGIS®, Benthic Terrain Modeler (BTM) to classify seabed environment into several geomorphology classes. Stepwise calculations of broad and fine Bathymetric Position Index (BPI) were applied into each grid, surficial characteristics of the seabed were analyzed according to several sets of scale-factor, and finally structures of the seabed were classified into 13 geomorphic classes.