Geomorphometric Mapping Research Articles

GIS and geomorphological mapping applied to landslide inventory and susceptibility mapping in the El Estado River basin, Pico de Ori-zaba, Mexico

With the purpose of strengthening the knowledge and prevention of landslide disasters, this work develops a methodology that integrates geomorphological mapping with the elaboration of landslide susceptibility maps using geographic information systems (GIS) and the multiple logistic regression method (MLR). In Mexico, some isolated works have been carried out with GIS to evaluate slope stability. However, to date, no practical and standardized method has been developed to integrate geomorphological maps with landslide inventories using GIS. This paper shows the analysis carried out to develop a multitemporal landslide inventory together with the morphometric analysis and mapping technique for the El Estado River basin where, selected as the study area, is located on the southwestern slope of the Citlaltepetl or Pico de Orizaba volcano. The geological and geomorphological factors in combination with the high seasonal precipitation, the high degree of weathering and the steep slopes predispose its surfaces to landslides. To assess landslide susceptibility, a landslide inventory map was prepared using aerial photographs, followed by geomorphometric mapping (altimetry, slopes and geomorphology) and field work. With this information, landslide susceptibility was modeled using multiple logistic regression (MLR) within a GIS platform and the landslide susceptibility map was obtained.

Delineation of main relief subdomains of central Amazonia for regional geomorphometric mapping with SRTM data

The geomorphometric characterization of central Amazonia reliefs is specially challenging because of its large dimension and rather uniform low topography of sedimentary units. In such conditions, usual techniques applied for general geomorphometry are ineffective and thus disabling direct bottom-up approaches for delimitations. Specific geomorphometry is a more promising approach for terrain analysis in this area, since procedures can be adapted to analyze the particular features of each geomorphological context. Therefore, delimitation of subdomains is a requirement for specific geomorphometry, to address proper approaches in the different strata. This paper presents a first level delimitation of major subdomains of Central Amazonia, carried out through combined techniques of geoprocessing guided by visual assessment. The three targeted subdomains, floodplains, plateau and highland, were mapped at the 1:2,000,000 scale using SRTM and derivative data as inputs. The relief of highland, as influenced by Precambrian to Cretaceous basement rocks, was firstly delimited using mostly height and relative relief combinations. The partition of the remaining lowland area into plateaus (Neogene) and floodplains (Quaternary sediments) was based on residual relief (subtraction of regional relief from full detail elevation data), with a regional relief modeled as the 9th order trend surface of elevations. Thresholds of negative residues were determined to create extents of visually assessed boundaries between plateau and floodplain areas. The continuous visual supervision of procedures and concerning interventions were based on interpretation of output displays of DEM and derived data prepared with image processing techniques. Delineation of subdomains was implemented through steps of supervised classifications and map algebra to operationally enable the task over the full area extension and corresponding data volume. Observation of data combined with knowledge and conceptual inputs were decisive to provide useful and unambiguous criteria to choose specific variables and analyses along this development.

Morphometry of glaciovolcanic edifices from Iceland: Types and evolution

The morphology of glaciovolcanoes is considered one of the distinctive characteristics of their ice-confining eruption environment. However, a thorough morphometric analysis of a large number of glaciovolcanic edifices has never been performed. Based on semi-automatic geomorphometric mapping, we present a morphometric database of 155 glaciovolcanic edifices within the Icelandic neovolcanic zones, formed during the last 0.78 Ma. This database enables a comprehensive analysis of the morphometric diversity of a large suite of glaciovolcanic edifices. Sheet-like formations, however, are not considered due to lack of data. Using three planimetric measurements (basal length, average basal width and average summit plateau width) and their ratios, three main morphometric groups can be distinguished in a ternary diagram: 1) conical edifices with no or small summit plateaus, 2) linear ridges and 3) flat-topped edifices (subdivided into equidimensional and elongated). All three groups contain edifices with and without lava caps. These morphometric groups can be fitted to the commonly accepted terminology for cone/mound, tindar and tuya. However, since lava caps occur in all morphometric groups, a grouping based on its existence is not practical. This suggests that by adding the descriptor “lava-capped” to any of the three classes may be a useful way to refine the classification. Based on the ternary diagram, ridges are the most morphometrically distinct glaciovolcanic edifice, because of their extreme elongation, followed by flat-topped edifices and finally conical edifices. However, morphometric parameters cannot be used singlehanded to identify glaciovolcanic edifices from other types of volcanic edifices such as composite volcanoes, shields or submarine volcanoes, and should always be complemented with other observations. The glaciovolcanic edifice volumes range from 0.15 · 10−2 km3 to 32 km3. Conical edifices are the smallest (<0.1 km3) and the group of flat-topped edifices has the largest edifices (>1 km3). Overall, with growth three morphological evolutions can be considered: (A) an initial eruptive fissure concentrates into one vent generating an equidimensional edifice, that either can be a conical or a flat-topped edifice; (B) the edifice maintains its elongation, suggesting that a fissure is the dominating vent structure, and during continued eruption develops significant summit plateaus, generating elongated flat-topped edifices; and (C) the edifice increases in elongation because the fissure lengthens during the eruption, and a plateau-building stage does not occur, producing increasingly elongated ridges.

Multi-resolution soil-landscape characterisation in KwaZulu Natal: Using geomorphons to classify local soilscapes for improved digital geomorphological modelling

Continual advances in quantitative modelling of surface processes, combined with new spatio-temporal and geo-computational algorithms, have revolutionised the auto-classification and mapping of landform components through the automated analysis of high-quality digital elevation models (DEMs). Digital geomorphic mapping (DGM) approaches that can simplify and translate the inclusion of “human knowledge” to automatic terrain classification across a broader spectrum of terrain morphological units as well as a range of spatial scales, therefore, offer great potential for improved topographic and landscape analysis. One such approach is the mapping of landform elements using the concept of the Geomorphon (geomorphological phonotypes). The output of the geomorphon approach is the stratification of the landscape into ten unique but recognisable landform elements: peak, ridge, shoulder, spur, and slope, hollow, foot slope, valley, depression and flat. Equally appealing is the way the model self-adapts to local topography using a line-of-sight principle enabling better matching of landform elements to computational spatial scale. The purpose of this paper is to observe the effects that different pixel resolution (grain size) and digital elevation model source (DEM) would have on the replication of observed geomorphic spatial patterns and representation of terrain selected parameters within the landscape. This paper provides a comprehensive exploratory assessment of digital terrain representation and relief classification using an automated geomorphometric mapping approach, by evaluating three different digital surface models (SUDEM, SRTM, ASTER GDEM2) and different spatial resolution (30 m & 90 m) for an 11,200 ha catchment in KwaZulu-Natal, South Africa. To test the self-adapting ability of the geomorphon approach under regional conditions, we use 4750 gridded terrain samples to quantitatively analyse how the choice of terrain model and scale influence the extraction, generalisation and representation of digitally-derived terrain attributes such as slope, elevation and terrain unit feature extent. We further show how the variation in resulting terrain unit representation is limited by spatial resolution discontinuities of selected elementary soil association distribution, soil texture and soil depth. We also introduce the results of a Similarity Index used to gauge the degree of recall and precision between the different geomorphic landscape features. Finally, the findings of the regional geomorphon-soil relationships are presented in a readily interpretable and qualitative manner, providing a “quasi-landscape signature” for potential localised geomorphons. The application of the study findings may be beneficial to practitioners looking to align or refine modelled terrain classification approaches with expert perception and formalised heuristic approaches.

Avaliação geomorfométrica de campo de murundus no Chapadão do Diamante, Serra da Canastra, Minas Gerais, Brasil

Os microrrelevos em formas arredondadas semi-elipsoidais são comuns dos campos de murundus, sobretudo no Cerrado. Na Serra da Canastra, localizada a Oeste do estado de Minas Gerais, estas feições são observadas na paisagem, cuja predominância se dá em áreas com má condição de drenagem, sobretudo na época das chuvas. Propôs-se neste estudo o mapeamento geomorfométrico de uma área de 1 hectare, para quantificar cada microrrelevo, com base em aerofotogrametria realizada por RPA ou VANT e seus subprodutos (MDE e ortomosaico). Inicialmente, foram individualizadas automaticamente 158 formas, sendo que, deste montante, 135 foram confirmadas como murundu, as demais eram formas que representam arbustos. Isso implica num índice de acertos de 88,8%. O conhecimento prévio da área e o ortomosaico com alta resolução (4cm/pix) foram indispensáveis para a averiguação dos dados obtidos automaticamente. Ressalta-se que a metodologia teve bom índice de acertos e merece novos testes, pois é um instrumental pouco oneroso e de resultado rápido.

Classificação geomorfométrica da bacia hidrográfica do rio Ijuí, RS

O presente estudo realizado na bacia hidrográfica do rio Ijuí, localizada na região norte/noroeste do Rio Grande do Sul, teve o objetivo de definir as unidades geomorfométricas na área em estudo por meio de técnicas de geoprocessamento associadas à análise digital do relevo. As unidades geomorfométricas foram compartimentadas a partir do emprego de atributos topográficos obtidos de um Modelo Digital de Elevação (MDE) em uma proposta de mapeamento geomorfométrico automatizado que é realizada através do cruzamento de informações e atributos topográficos, gerados por meio de um SIG e hierarquizados através de uma árvore de decisão. Foram empregadas quatro variáveis geomorfométricas: altimetria, declividade, perfil de curvatura e plano de curvatura que resultaram na definição de doze unidades de relevo, que a partir de amostragens realizadas no alto, médio e baixo cursos da bacia, nos quais se observou que as unidades se distribuem de forma distinta ao longo da bacia, com predominância das primeiras seis unidades do alto curso, no médio curso todas as doze unidades têm ocorrência. Já no baixo curso apenas as ultimas seis unidades se apresentam, porém, demostrando estreita relação com a hierarquia fluvial, embora os formatos de perfil e plano de encosta variam em todos os setores analisados, o que significa a possibilidade de diferentes processos superficiais ao longo de toda a bacia.

A multi-method approach for benthic habitat mapping of shallow coastal areas with high-resolution multibeam data

The coastal waters of the Maltese Islands, central Mediterranean Sea, sustain a diversity of marine habitats and support a wide range of human activities. The islands’ shallow waters are characterised by a paucity of hydrographic and marine geo-environmental data, which is problematic in view of the requirements of the Maltese Islands to assess the state of their coastal waters by 2012 as part of the EU Marine Strategy Directive. Multibeam echosounder (MBES) systems are today recognised as one of the most effective tools to map the seafloor, although the quantitative characterisation of MBES data for seafloor and habitat mapping is still an underdeveloped field. The purpose of this study is to outline a semi-automated, Geographic Information System-based methodology to map the distribution of habitats in shallow coastal waters using high-resolution MBES data. What distinguishes our methodology from those proposed in previous studies is the combination of a suite of geomorphometric and textural analytical techniques to map specific types of seafloor morphologies and compositions; the selection of the techniques is based on identifying which geophysical parameter would be influenced by the seabed type under consideration.We tested our approach in a 28km2 area of Maltese coastal waters. Three data sets were collected from this study area: (i) MBES bathymetry and backscatter data; (ii) Remotely Operated Vehicle imagery and (iii) photographs and sediment samples from dive surveys. The seabed was classified into five elementary morphological zones and features – flat and sloping zones, crests, depressions and breaks of slope – using morphometric derivatives, the Bathymetric Position Index and geomorphometric mapping. Segmentation of the study area into seagrass-covered and unvegetated seafloor was based on roughness estimation. Further subdivision of these classes into the four predominant types of composition – medium sand, maërl associated with sand and gravel, seagrass settled on sand and gravel, and seagrass settled on bedrock – was carried out through supervised classifications of morphometric derivatives of the bathymetry and textural indices of backscatter, based on information from training stations. The resulting morphologic and seabed composition maps were combined to plot the distribution of the predominant habitats in the coastal waters offshore NE Malta, some of which are of high conservation value. Ground-truthing of the habitat map using ROV imagery and dive observations confirms that our approach produces a simplified and accurate representation of seafloor habitats while using all the information available within the MBES data sets.

Size distribution of submarine landslides along the middle continental slope of the East China Sea

This paper investigates the size distribution of submarine landslides on the middle continental slope of the East China Sea (ECS) using the size of the landslide source regions. Geomorphometric mapping is used to identify 102 mass movements from multibeam bathymetric data and to extract morphological information about the head scarps and side walls. These mass movements have areas ranging between 0.06 km2 and 15.51 km2 and volumes between 0.002 km3 and 2 km3. The area vs volume relationship of these failure scarps is approximately linear, suggesting a fairly uniform failure thickness in each event with scarce deep excavating landslides. The cumulative area distribution of the slope failures can be described by an inverse power law. The submarine landslides on the mid-ECS continental slope could be considered as a large-scale self-organizing system because they have the characteristics of a dissipative system in a critical state.

Scale invariant characteristics of the Storegga Slide and implications for large-scale submarine mass movements

This study documents the fractal characteristics of submarine mass movement statistics and morphology within the Storegga Slide. Geomorphometric mapping is used to identify one hundred and fifteen mass movements from within the Storegga Slide scar and to extract morphological information about their headwalls. Analyses of this morphological information reveal the occurrence of spatial scale invariance within the Storegga Slide. Non-cumulative frequency-area distribution of mass movements within the Storegga Slide satisfies an inverse power law with an exponent of 1.52. The headwalls exhibit geometric similarity at a wide range of scales and the lengths of headwalls scale with mass movement areas. Composite headwalls are self-similar. One of the explanations of the observed spatial scale invariance is that the Storegga Slide is a geomorphological system that may exhibit self-organized criticality. In such a system, the input of sediment is in the form of hemipelagic sedimentation and glacial sediment deposition, and the output is represented by mass movements that are spatially scale invariant. In comparison to subaerial mass movements, the aggregate behavior of the Storegga Slide mass movements is more comparable to that of the theoretical ‘sandpile’ model. The origin of spatial scale invariance may also be linked to the retrogressive nature of the Storegga Slide. The geometric similarity in headwall morphology implies that the slope failure processes are active on a range of scales, and that modeling of slope failures and geohazard assessment can extrapolate the properties of small landslides to those of larger landslides, within the limits of power law behavior. The results also have implications for the morphological classification of submarine mass movements, because headwall shape can be used as a proxy for the type of mass movement, which can otherwise only be detected with very high resolution acoustic data that are not commonly available.

Geomorphometric mapping of asia minor from globe digital elevation model

ABSTRACT. The paper focuses on the characterization of the Earth's relief in Asia Minor based upon a regional‐scale GLOBE digital elevation model representation. At first, general geomorphometric parameters and frequency distributions are computed and the resulting descriptive statistics are studied in an attempt to characterize the landscape. The mountain terrain class was identified from the digital elevation model by a region‐growing segmentation procedure and 702 distinct mountain features were extracted. The mountains were parametrically represented on the basis of the local relief mean gradient, mean elevation, and hypsometric integral. The statistical modelling indicated clusters of mountain features that are spatially arranged in specific zones providing a framework for comparing regions located in different tectonic regimes and subdividing the landscape of Asia Minor into regions with different geomorphometric behaviour. Finally, the classification of mountains identified that the highest in gradient, the biggest in size and the most complex ones are spatially arranged in the east along a northern and a southern branch. In between the branches a transition zone is developed that contains a minor peneplain (east plateau) and a major peneplain (central Anatolia) occupied by more dissected and eroded mountains oriented in a SE to NW direction.

Geomorphometric mapping of Zagros Ranges at regional scale

A method for regional-scale geomorphometric mapping that is useful for morphotectonic studies is presented for the Zagros Ranges in Iran. The DEM-to-Mount transformation, a region-growing algorithm for terrain segmentation is implemented. To cope with the specific conditions in that compressional-morphotectonic context, the transformation was modified: region growing was not allowed for valley pixels; ridge pixels were used as seeds; and the growing criterion was based on gradient. The landscape was decomposed to two terrain classes (mount and non-mount) and to isolated mountain objects that were numerically represented on the basis of appropriate attributes (mean and maximum elevation, gradient, hypsometric integral, size). The domain of the attributes was sliced to intervals on the basis of geomorphometric criteria and their spatial occurrence. Finally, the landscape was characterized on the basis of mountain morphometry from the spatial distribution of the classes. The objects greatest in size were observed in the NW. Three distinct regions with respect to the mean elevation were spatially distributed in increasing mean elevation from SE to NW, producing stair-step topography at a regional scale. In the NW, the degree of dissection was less and objects with the highest gradient were observed. These observations suggest that at a regional scale the main NW topographic units have not been significantly downcut towards sea level, for a pattern of small isolated objects with lower mean elevation, gradient and hypsometric integral to be formed as those observed in the SE.