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Combining digital elevation data (SRTM/ASTER), high resolution satellite imagery (Quickbird) and GIS for geomorphological mapping: A multi-component case study on Mediterranean karst in Central Crete

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Abstract

Remote sensing data have become more and more popular for geomorphological investigations because their steadily increasing level of detail and accessibility opens up new potentials. In this context, this paper examines the application and quality of digital elevation models (SRTM and ASTER DEMs), high resolution satellite imagery (Quickbird) and GIS techniques for the detection and mapping of karst landforms (mainly enclosed depressions) at different scales in the Ida Mountains of Central Crete. Besides discussing methodological issues and evaluating suitability potentials, we conducted an exemplary case study based on spatial analysis of the regional karst morphology. Different input datasets and processing methods are applied (GIS-based analysis, land cover classification, raster calculations, etc.) in order to carry out an area-wide surveying and mapping of karst depressions. The findings are supported and validated by auxiliary field studies.

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... Ha sido gracias a los recientes avances tecnológicos, tales como los sistemas de información geográfica (SIG), los sistemas de posicionamiento global (GPS), los modelos digitales de elevaciones (MDE) y otros datos del amplio espectro electromagnético registrados de forma remota mediante diferentes técnicas de teledetección aerotransportada o satelital, que se ha permitido llevar a cabo estudios morfométricos de mayor detalle y uniformemente sobre zonas extensas, ayudando a profundizar nuestro conocimiento en el origen y la naturaleza de los terrenos kársticos, los principios que regulan la karstogénesis, así como de los factores medioambientales y antrópicos que influyen (Denizman y Randazo, 2000;Shofner et al., 2001;Hung et al., 2002;Florea, 2005;Lyew-Ayee et al., 2007;Huang, 2007;Gao y Zhou, 2008;Galve et al., 2009;Siart et al., 2009). Los trabajos cartográficos realizados sobre plataformas SIG en este tipo de terrenos son relativamente recientes, aunque se han mostrado muy versátiles y populares al permitir trabajar con información geográfica tanto de la superficie (endokarst) como del interior (endokarst), ayudando a establecer las relaciones y conexiones existentes entre superficie y profundidad (Szukalski, 2002;Gao, 2008;Siart et al., 2009). ...
... Ha sido gracias a los recientes avances tecnológicos, tales como los sistemas de información geográfica (SIG), los sistemas de posicionamiento global (GPS), los modelos digitales de elevaciones (MDE) y otros datos del amplio espectro electromagnético registrados de forma remota mediante diferentes técnicas de teledetección aerotransportada o satelital, que se ha permitido llevar a cabo estudios morfométricos de mayor detalle y uniformemente sobre zonas extensas, ayudando a profundizar nuestro conocimiento en el origen y la naturaleza de los terrenos kársticos, los principios que regulan la karstogénesis, así como de los factores medioambientales y antrópicos que influyen (Denizman y Randazo, 2000;Shofner et al., 2001;Hung et al., 2002;Florea, 2005;Lyew-Ayee et al., 2007;Huang, 2007;Gao y Zhou, 2008;Galve et al., 2009;Siart et al., 2009). Los trabajos cartográficos realizados sobre plataformas SIG en este tipo de terrenos son relativamente recientes, aunque se han mostrado muy versátiles y populares al permitir trabajar con información geográfica tanto de la superficie (endokarst) como del interior (endokarst), ayudando a establecer las relaciones y conexiones existentes entre superficie y profundidad (Szukalski, 2002;Gao, 2008;Siart et al., 2009). ...
... Entre los diferentes tipos de información manejada con los SIG, los MDE han demostrado, a través de múltiples estudios y resultados obtenidos, su enorme utilidad para el análisis morfológico de la superficie terrestre, principalmente en áreas abruptas e inaccesibles. Sin embargo, se puede constatar que el uso exclusivo de los MDE, modelos combinados con imágenes aéreas, resulta insuficiente para una caracterización automática de ciertos elementos superficiales propios de los sistemas kársticos, de distribución compleja e irregular y, a veces, enmascarada por los errores propios del MDE, como son las depresiones y hundimientos, principalmente dolinas, cenotes, uvalas y otros elementos de tamaño pequeño que necesitan de otras técnicas de mayor resolución para su detección (Shofner et al., 2001;Gutiérrez-Santolalla et al., 2005;Siart et al., 2009;Gutiérrez et al., 2014). En este sentido, por ejemplo, Siart et al., (2009) sugiere una aproximación alternativa mediante la combinación del análisis espacial de diferentes capas de información geográfica, apoyado y validado con campañas de campo que se contrasten con los resultados analíticamente obtenidos sobre el SIG. ...
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El libro Los Ojos de Yucatán. Una ventana al mundo subterráneo es resultado del trabajo colaborativo de la Facultad de Química de la UNAM y el Instituto Geológico y Minero de España (IGME). El libro incluye valiosa información de la naturaleza geológica de la península de Yucatán, con énfasis en sus cenotes y cuevas. Sus primeros capítulos incluyen una explicación detallada de las características geológicas de la península de Yucatán, su hidrología y el origen de sus cenotes. Los cenotes y cuevas son presentados como socioecosistemas importantes, dado su atractivo turístico y por ser el hábitat de numerosas especies, algunas de ellas únicas en su tipo. El libro incluye también registros sobre la contaminación del acuífero de la península de Yucatán, proporcionando evidencia de la cuantificación de contaminantes, tanto legendarios como emergentes, y sus efectos en las especies, incluyendo al hombre. En sus capítulos se resalta la fragilidad de estos ecosistemas y la importancia de tener una normativa federal y estatal para su protección. Se incluye también una descripción detallada de la importancia de los cenotes desde el punto de vista antropológico y su misticismo para los mayas, en los cuales los cenotes son sagrados y son la entrada al inframundo. Este libro constituye una lectura obligada para toda persona interesada en conocer el origen y la naturaleza de las cuevas y cenotes de Yucatán, lo especial de su biodiversidad, su vulnerabilidad a la contaminación y otros estresores, e incluye también información encaminada a la protección y uso sostenible de los mismos.
... Such DEMs are usually characterized by very high resolution (up to few centimetres) and they may be used in local scale studies, whereas airborne LiDAR data that cover larger area than UAV images may be used in regional scale approach. Moreover, sometimes, the finest scale of analysis is not the best (Siart et al., 2009;Thomas et al., 2017;Kariminejad et al., 2020) and it depends on the study scale, objectives and size of landforms analysed. ...
... The key question on how to distinguish real (i.e., process-related) depressions from artificial ones still remains open. In karst studies following data have been used to support the terrain information: size thresholds and geometry of depressions, geological structure, land cover, hydrologic conditions, soil type and depth (Siart et al., 2009;Alexander et al., 2013;Rahimi and Alexander, 2013;Zhu et al., 2014;Zhu and Pierskalla, 2016;Hofierka et al., 2018). In soil piping studies this question seems to be even more challenging as surface indicators of piping are of different sizes, shapes, depths, they occur in different landscape positions and under various land use, as well as almost all soil types may be prone to piping (Bernatek-Jakiel and Poesen, 2018;Bernatek-Jakiel et al., 2019). ...
... These data allowed to prepare the DEM of 1 m resolution, which nowadays, when the UAV data are more easily accessible, are not sufficient at local scale studies. Some small landforms may fall below the resolving power of the data as already stated in other research (e.g., Siart et al., 2009). ...
Article
The detection of soil piping features is still a challenging issue that requires further studies, especially at larger scale. It seems that field mapping as a time-consuming method can be supported by the new technologies. This study has exploited the freely available airborne LiDAR (Light Detection and Ranging) digital elevation model (DEM) to explore piping-related depressions. The aim was to test the possibility of digital detection of piping forms using sink-fill method and different derivatives of airborne LiDAR DEM (slope, Topographic Position Index, Topographic Ruggedness Index, Positive and Negative Openness Index) in order of its utility in regional scale studies. As geological structure, soils and climate are similar in the whole study area, the analysis was extended to include the changes in land use/land cover (LULC) in the last two centuries (1862–2017). The results were verified by the detailed geomorphological mapping in the field. The study was conducted in a small catchment in the Bieszczady Mts. (SE Poland) covered by forests and grasslands/pastures, where in the past transition from pastures to forests was observed. The findings have revealed the great impact of LULC changes on soil piping, thus also on the possibility of digital mapping which is often based only on topographic information. The success rate in recognition was satisfactory on grasslands/pastures (76% for individual forms and 80% for piping systems). Areas covered by forests since the mid-19th century are unlikely places to develop piping forms (just 2 forms found) in the study area, whereas places where transition from pastures to forest has been observed may be prone to soil piping. However, the digital identification of piping forms in areas with rough topography is difficult (a success rate of 45% for individual forms and 50% for piping systems). The digital mapping of piping forms cannot rely only on the topographic information but should be always accompanied by an analysis of factors controlling piping erosion.
... Meneses (2003) reinforces that computer tools facilitate complex analysis with the interaction of data from various sources and the creation of georeferenced data banks. This type of application has proven very useful for the geomorphological mapping of karst landscapes (Oliveira 2001;Sallun Filho and Karmann 2007;Siart et al. 2009;Silva et al. 2015). However, many of these investigations have been performed based on aerial photography interpretation and manual delineation, which leads to long execution periods and greater subjectivity (Williams 1972;IBAMA 1998;Telbisz et al. 2009;Uagoda et al. 2011;Zumpano et al. 2019). ...
... In this context, the size of the objects to be identified always represents the variable that predetermines the adequate image resolution to be used in the analysis. Automatic methods to identify surface features in karst environments found in the literature are mainly based on methods that use multi-spectral classification, digital elevation models, digital terrain models, and RGB satellite imagery, or a combination of one or more of these four resources (Slater and Brown 2000;Oliveira 2001;Denizman 2003;Lyew-Ayee et al. 2007;Kokalj and Ostir 2007;Siart et al. 2009;Basso et al. 2013;Doctor and Young 2013;de Carvalho et al. 2014;Liang et al. 2014;Bauer 2015;Al-Fugara et al. 2016;Jeanpert et al. 2016;Pardo-Igúzquiza et al. 2016;Wall et al. 2016;Wu et al., 2016;Hofierka et al. 2018;Šegina et al. 2018;Theilen-Willige et al. 2014;Verbovšek and Gabor 2019;Zumpano et al. 2019). ...
Article
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Satellite imaging combined with geoprocessing routines is a promising alternative to establish a viable mapping model of specific landscape features and soil use, with high precision, fast results, and low operational costs. The present study examines the employment of a digital elevation model (DEM) combined with geoprocessing techniques for identifying closed depressions in karst landscapes with the objective of mapping potential sinkholes and uvalas within the limits of the Carste Lagoa Santa Environmental Protection Unit, located in the state of Minas Gerais, Brazil. The proposed method consists of using geoprocessing routines combined with DEMs, topographic analysis, individual points of elevation, and mathematical operations between rasters. To accomplish that, SRTM (Shuttle Radar Topographic Mission) data/images were used to extract contour lines and individual elevation points to identify depressions, delimit their edges, and obtain morphometric data referring to the area, perimeter, and their circularity index. The results were satisfactory, allowing the detection of 1076 depressions within the study area. The results were also analyzed for special morphological cases and circularity patterns and compared with a previous study. Field campaigns allowed the partial validation of the method, which proved to be a viable alternative for preliminary and extensive scale mapping of these important karst recharge features.
... The use of Airborne Laser Swath Mapping (ALSM) has been shown to not be a useful way to map karst features unless a large amount of aerial photography was being used (Seale et al., 2008). Ground truthing sometimes produces features that must be incorporated into data sets from field mapping (Siart et al., 2009). Handheld (Global Positioning System) GPS unit are used in the field for navigation to field locations, recording exact coordinates for new features, and begin a preliminary analysis of the landscape features (Cornelius et al., 1994). ...
... Another method to separate sediment filled depressions from vegetation and bare rock would be to use the sink-fill tool (Siart et al., 2009). Using the Topographic Position Index (TPI) to calculate the elevation difference between a point on a DEM and the neighboring pixel is an emerging way to detect karst features (Doctor and Young, 2013). ...
Thesis
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This research consisted of two topics: 1) geographic predictive models of karst features and 2), a petrographic study examining the lithology of the study area. The study area is a privately owned ranch in the Gypsum Hills of Barber County, Kansas and is known to have karst features. Two predictive models for karst features were utilized. Previously identified features, Light Detection and Ranging (LiDAR), and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery aided in the creation of these predictive models. These predictability models also used the ESRI ArcMap software platform. The data for these models consists of slope, aspect, nearest neighbor elevation, Normalized Difference Vegetation Index (NDVI), land cover/land use, distance to geomorphic features, surface geology, and other attributes calculated in ArcMap. Other software platforms were also used in the creation of these models (Microcomputer Digital Elevation Models (MicroDEM), System for Automated Geoscientific Analyses (SAGA) GIS and Environment for Visualizing Images (ENVI) for imagery analysis). To test these models, features were identified using the sink-fill function in ArcMap on hillshade layers generated from LiDAR data. Field validation of these models successfully identified 52% of the validation points as having karst features, as well as 12 additional points in high probability areas that were visited. A total of 38 additional points (a 51% increase in the karst database) were added to the karst inventory for the property. Understanding the distribution and occurrence of karst features will help landowners mitigate risk such as collapse leading to structural damage and aquifer contamination. Although this model focused on Barber County, Kansas, the techniques and approaches used by these two models may be useful in creating future predictive models in other karst areas. The petrographic portion of this research identified two geologic sedimentary facies using petrographic thin sections from various karst features. The two facies were: 1) Algal Mat and 2) Peloidal. These facies are very close to one another spatially when plotted by sample location within the property. The relative elevation of these facies places the Algal Mat facies below the Peloidal facies. This suggests that there are multiple facies that control karst feature formation as opposed to only the basal carbonates suggested by previous studies.
... DEMs can be derived not only from scanned/vectorized contour lines of existing topographic sheets obtained by field measurement [9], but also from remote sensing techniques. While the accuracy of the field measurement method is quite high, it is also time consuming and costly, especially in hard-to-reach areas [10,11]. Remote sensing has become the primary means of obtaining DEMs due to its near ideal characteristics in terms of coverage, and spatial and temporal resolution [12]. ...
... Remote Sens. 2018,10, 1861 ...
Article
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The growing need to monitor changes in the surface of the Earth requires a high-quality, accessible Digital Elevation Model (DEM) dataset, whose development has become a challenge in the field of Earth-related research. The purpose of this paper is to improve the overall accuracy of public domain DEMs by data fusion. Multi-scale decomposition is an important analytical method in data fusion. Three multi-scale decomposition methods—the wavelet transform (WT), bidimensional empirical mode decomposition (BEMD), and nonlinear adaptive multi-scale decomposition (N-AMD)—are applied to the 1-arc-second Shuttle Radar Topography Mission Global digital elevation model (SRTM-1 DEM) and the Advanced Land Observing Satellite World 3D—30 m digital surface model (AW3D30 DSM) in China. Of these, the WT and BEMD are popular image fusion methods. A new approach for DEM fusion is developed using N-AMD (which is originally invented to remove the cycle from sunspots). Subsequently, a window-based rule is proposed for the fusion of corresponding frequency components obtained by these methods. Quantitative results show that N-AMD is more suitable for multi-scale fusion of multi-source DEMs, taking the Ice Cloud and Land Elevation Satellite (ICESat) global land surface altimetry data as a reference. The fused DEMs offer significant improvements of 29.6% and 19.3% in RMSE at a mountainous site, and 27.4% and 15.5% over a low-relief region, compared to the SRTM-1 and AW3D30, respectively. Furthermore, a slope position-based linear regression method is developed to calibrate the fused DEM for different slope position classes, by investigating the distribution of the fused DEM error with topography. The results indicate that the accuracy of the DEM calibrated by this method is improved by 16% and 13.6%, compared to the fused DEM in the mountainous region and low-relief region, respectively, proving that it is a practical and simple means of further increasing the accuracy of the fused DEM.
... The free availability of processed SRTM data by government agencies expands its use (Bias et al. 2010;Iorio et al. 2012). Therefore, SRTM data has been used in different applications such as flood areas (e.g., Suwandana et al. 2012), glacier inventories (e.g., Frey and Paul 2012), karst depression detection (e.g., Siart et al. 2009;de Carvalho Júnior et al. 2014), and geomorphological mapping (e.g., vasconcelos et al. 2014;Sena-Souza et al. 2016), among others. ...
Article
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This research aims to determine the vertical accuracy of the Interferometric Digital Elevation Model (DEM) obtained from the processed Shuttle Radar Topographic Mission (SRTM) data. The research compared the SRTM-GL1 (Shuttle Radar Topographic Mission-Global 1) with 30-meter resolution and the following 90-meter resolution models: (a) EMBRAPA; (b) Hydrological data and maps based on Shuttle Elevation Derivatives at multiple Scales (HydroSHEDS) (HydroSHEDS), provided by the United States Geological Survey (USGS); (c) Consultative Group for International Agricultural Research-Consortium for Spatial Information (CGIAR-CSI); and (d) Jonathan de Ferranti. The accuracy analysis considered the diverse Brazilian regions, adopting 1,087 field points from the Global Navigation Satellite System (GNSS) trackers or topography methods. The Jonathan de Ferranti model achieved the best accuracy with RMSE of 9.61m among the 90-meter resolution models. Most SRTM models at 1:100,000 scale reached Grade A of the Cartographic Accuracy Standard. However, the accuracy at the 1: 50,000 scale did not achieve the same performance. SRTM errors are linearly related to slope and the most significant errors always occur in forest areas. The 30-meter resolution SRTM showed an accuracy of around 10% better (RMSE of 8.52m) than the model of Jonathan de Ferranti with 90-meter resolution (RMSE of 9.61m).
... For hydrological modeling, GIS is used along with hydrologic and hydraulic models, to analyze multi-spatial and temporal data (Merwade et al. 2008;Gallegos et al. 2009). For developing any hydrologic model, digital elevation model (DEM) with GIS is used to extract essential geographical details of the basin (Tarboton and Ames 2001;Siart et al. 2009;Thirumurugan and Krishnaneni 2018). ...
Article
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Flooding in urban basins is a major natural catastrophe that leads to many causalities of life and property. The semi-urbanized Koraiyar River basin in Tamil Nadu has important cities like Tiruchirappalli and many towns located in it. The basin unfailingly experiences a flood event in almost every decade. It is anticipated that the basin will undergo rapid unplanned urbanization in the years to come. Such fast and erratic urban developments will only increase the risk of urban floods ultimately resulting in loss of human lives and extensive damages to property and infrastructure. The effects of urbanization can be quantified in the form of land use land cover (LULC) changes. The LULC change and its impacts on urban runoff are studied for the continuous 30-year present time period of (1986–2016) to reliably predict the anticipated impact in the future time period of (2026–2036). The analysis of land cover patterns over the years shows that urbanization is more prevalent in the northern part of the basin of the chosen study area when compared with the other regions. The extreme rainfall events that occurred in the past, and the probable future LULC changes, as well as their influence on urban runoff, are studied together in the current study. In order to minimize flood damages due to these changing land use conditions, certain preventive and protective measures have to be adopted at the earliest. There are some inevitable limitations while applying traditional measures in flood modeling studies. This investigative work considers a case study on the ungauged Koraiyar floodplains. The spatial scale risk assessment is assessed by coupling geographic information systems, remote sensing, hydrologic, and hydraulic modeling, to estimate the flood hazard probabilities in the Koraiyar basin. The maximum flood flow is generated from the Hydrologic Engineering Centre-Hydrologic Modeling System (HEC-HMS), the hydrologic model adopted in the present study. The maximum flood flow is given as input to the Hydrologic Engineering Centre-River Analysis System (HEC-RAS), an effective hydraulic model that generates water depth and flood spread area in the basin. The flood depth and hazard maps are derived for 2, 5, 10, 50, and 100-year return periods. From the analysis, it is observed that the minimum flood depth is less than 1.2 m to a maximum of 4.7 m for the 100-year return period of past to predicted future years. The simulated results show that the maximum flood depth of 4.7 m with flood hazard area of 4.32% is identified as high hazard zones from the years 1986–2036, located in the center of the basin in Tiruchirappalli city. The very high hazard flood-affected zone in the Koraiyar basin during this period is about 198.85 km². It is noticed that the very low hazard zone occupies more area in the basin for the present and future simulations of flood hazard maps. The results show that the increase in peak runoff and runoff volume is marginally varied.
... Siart et al. (2009) utilizaram o mesmo método para contabilizar as dolinas na Ilha de Creta, mas observaram que a baixa resolução das fontes utilizadas para gerar o modelo (SRTM e ASTER) implicou em detecção apenas de feições grandes a médias, necessitando adicionar análises visuais e campo para construção do mapa geomorfológico local. Nesse trabalho, observa-se uma das primeiras tentativas de aplicação de fi ltros morfométricos de dolinas para eliminar o grande número de falsos positivos, ou seja, feições depressivas similares a dolinas, mas de origem artifi cial (antrópica ou por defeito na geração do MDE).Telbisz et al. (2009) aplicaram a técnica em uma área cárstica croata com a utilização de um MDE construído a partir de mapa topográfi co (1:25.000). ...
Article
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As dolinas são feições indicadoras do sistema cárstico e além de atestarem processos evolutivos, também apresentam importância no contexto das dinâmicas hídricas e ambientais. O mapeamento dessas feições serve como base para diversas análises da paisagem e exige grande dispêndio de tempo e recursos, com significativa subjetividade inerente à técnica de aquisição ou à problemas de escala. A melhoria da resolução espacial nas bases de dados permitiu maior precisão nos mapeamentos de dolinas com o uso de modelos digitais de elevação e técnicas de geoprocessamento, automatizadas ou manuais. Entretanto, as dificuldades de detecção dos pontos de absorção que individualizam as dolinas, e os limites estabelecidos para seu perímetro dificultam a comparação entre estudos, agregando incertezas nos atributos espaciais como área, profundidade e eixo principal. Neste artigo são discutidas as principais metodologias de mapeamento de dolinas e sintetizadas as estratégias mais utilizadas para superar erros de omissão de feições verdadeiras, problemas com a detecção de falsos positivos e a delimitação mais precisa das depressões cársticas.
... Potentially unstable areas consist of localities with morphological changes. DEM change detection include different geomorphological studies, such as tectonic (e.g., Oskin et al. 2012;Ren et al. 2014), slope processes and mass movement (e.g., Hsieh et al. 2016;Mora et al. 2018;Xiong et al. 2018;Peppa et al. 2019), fluvial (e.g., Grove et al. 2013;Norman et al. 2017;Carrivick and Smith 2019;Kasprak et al. 2019), coastal dunes (e.g., Walker et al. 2013Duffy et al. 2018;Le Mauff et al. 2018;Guisado-Pintado et al. 2019), glacial (e.g., Nuth and Kääb 2011;Jones et al. 2013;Micheletti et al. 2017;Seier et al. 2017), and karst (e.g., Siart et al. 2009;Carvalho Junior et al. 2013;Kobal et al. 2015). ...
Article
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Urbanization processes have caused changes in the runoff behavior, especially by impervious surfaces produced by paving and buildings. Impermeable surfaces prevent the infiltration of rainwater, increasing the volume and speed of runoff. Besides, inadequate urban planning coupled with heavy rains promotes the evolution of erosion processes, especially in peri-urban areas. This research aims to identify spatial patterns of geomorphic change in the gully areas due to urbanization in the city of Jacareí (SP). The methodology has the following steps: (1) elaboration of the Digital Elevation Model (DEM) from stereophotogrammetric techniques; (2) elaboration of the pre- and post-urbanization DEM; (3) extraction of contributing area using the D-Infinity method and of the topographic indices (topographic wetness, stream power, and compound topographic); and (4) calculate the difference between the pre- and post-urbanization topographic attributes. The preparation of the pre- and post-urbanization DEM used the MATCH-T DSM and DTMaster modules, both belonging to the INPHO system. Photogrammetric techniques allow the generation of digital models suitable for hydrological studies. The urbanization exposed an evident influence on the triggering of erosion, evidencing an increase of all topographic indices in areas that develop gullies.
... Despite the accurate results produced from studies on karst cavities conducted using either geophysical [17][18][19][20] or remote sensing [21][22][23][24] methods, the fusion of the two techniques results in advantages in the acquisition, processing, and interpretation of geophysical data. Collecting spatial information on electrodes and surveyed points can particularly enhance sinkhole research. ...
Article
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The Causse of El Hajeb belongs to the Tabular Middle Atlas (TMA), in which thousands of karst landforms have been identified. Among them, collapse dolines and dissolution sinkholes have been highlighted as a source of environmental risks and geo-hazards. In particular, such sinkholes have been linked to the degradation of water quality in water springs located in the junction of the TMA and Saïss basin. Furthermore, the developments of collapse dolines in agricultural and inhabited areas enhance the risk of life loss, injury, and property damage. Here, the lack of research on newly formed cavities has exacerbated the situation. The limited studies using remote sensing or geophysical methods to determine the degree of karstification and vulnerability of this environment fail to provide the spatial extent and depth location of individual karst cavities. In order to contribute to the effort of sinkhole risk reduction in TMA, we employed remote sensing and geophysical surveys to integrate electrical resistivity tomography (ERT) and self-potential (SP) for subsurface characterization of four sinkholes identified in the Causse of El Hajeb. The results revealed the existence of sinkholes, both visible and non-accessible at the surface, in carbonate rocks. The sinkholes exhibited distinct morphologies, with depths reaching 35 m. Topography, geographic coordinates and land cover information extracted on remote sensing data demonstrated that these cavities were developed in depressions in which agricultural activities are regularly performed. The fusion of these methods benefits from remote sensing in geophysical surveys, particularly in acquisition, georeferencing, processing and interpretation of geophysical data. Furthermore, our proposed method allows identification of the protection perimeter required to minimize the risks posed by sinkholes.
... Mais recentemente, com o desenvolvimento de ferramentas de geoprocessamento e com a crescente disponibilidade de bases de dados com maior resolução, aumentaram as possibilidades de identificação de depressões cársticas de forma indireta, o que pode significar menos dispêndio de tempo e recursos. Nesse sentido, Siart et al. (2009) As possibilidades trazidas para as geociências com o desenvolvimento dos VANTs nos últimos anos são inúmeras, desde a viabilidade de levantamentos aerofotogramétricos de alta resolução temporal, espacial (centimétrica) e mesmo espectral (câmeras termais, NDVI, etc.), como também a possibilidade de recobrimento de áreas inacessíveis ou de alto risco. O conjunto de imagens adquiridas em sobreposição permitem a montagem de ortofotomosaicos e modelos digitais de elevação (MDE) de alta resolução por aplicativos especializados. ...
Conference Paper
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Indentification of dolines has usually been done through the analysis of aerial photographs, topographic map or fieldwork, which may demand a lot of time and financial resources. Studies of identification and classification of dolines are carried out to support environmental and evolutionary analyzes of karst. Recently, dolines have been detected by digital elevation models, but few studies have been devoted to mapping these features through collecting data by Unmanned Aerial Vehicles (UAV). The objective of this paper is assessing the use of such tecnology for digital models production and to compare its effectiveness to ALOS-PALSAR data and field surveys in the region of the Gruna da Tarimba, one of the largest caves in Brazil. The results show a great potentiality of UAV for mapping dolines and especially for guide prospecting. Additionally, preprocessing digital models and establishing ground control points can contribute to the reduction of spurious results that greatly increase the number of likely dolines.
... Topography is important for research and engineering in many fields, such as geosciences, geology and geomorphology, natural disasters, hydrology and water resources management and so on (Barbarella et al., 2017;Courty et al., 2019;Jarihani et al., 2015;Moore et al., 1991;Siart et al., 2009). It is preliminary measured by contour lines and ground control points in topographic maps. ...
Article
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This paper aims to compare the performance of typical open global DEM datasets by using the indexes of elevation error, relative error and hydrologic network. Taking Fenhe River Basin of China as the study area, this research made quantitative performance comparison among four typical open global DEM datasets including SRTM data with 1” (SRTM1) and 3” (SRTM3) resolutions, ASTER Global DEM data at the 2nd version (GDEM-v2) and ALOS World 3D-30 m (AW3D) data. Through process and selection, more than 80,000 ICESat/GLA14 points were used as the reference data, and the elevation error was computed and compared accordingly. Furthermore, relative error was analyzed using slope values, and false slope ratio index was computed and categorically compared. Finally, the hydrologic networks extracted from the four DEM datasets were compared to the reference hydrologic network acquired by visual interpretation from remote sensing images. The research results show that the AW3D has the best performance, which is approximate to but a little better than SRTM1. The performance of SRTM3 and GDEM-v2 is similar, which are much worse than that of AW3D and SRTM1, and the performance of GDEM-v2 is the worst of all.
... Individual landform units can be extracted on the basis of the nested structure of contours, but such a method wrongly regards the connected Fenglin pinnacles as Fengcong in most cases. The second method involves constructing a recognition model of Fenglin, Fengcong, and other karst landform units and extracting object-oriented texture features according to the morphological characteristics of objects [30][31][32][33][34]. This method mainly calculates the objects in the analysis windows by terrain factors, such as elevation, slope, curvature, and texture, then it differentiates karst landform types. ...
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In this paper, a method for extracting Fenglin and Fengcong landform units based on karst topographic feature points is proposed. First, the variable analysis window method is used to extract peaks, nadirs, and saddle points in the karst area based on digital elevation model (DEM) data. Thiessen polygons that cover the karst surface area are constructed according to the locations of the peaks and nadirs, and the attributes of the saddles are assigned to corresponding polygons. The polygons are automatically classified via grouping analysis according to the corresponding spatial combinations of peaks, saddles, and nadirs in the Fenglin and Fengcong landform units. Then, a detailed division of the surface morphology of the karst area is achieved by distinguishing various types of Fenglin or Fengcong landform units. Experiments in the Guilin research area show that the proposed method successfully distinguishes the Fenglin and Fengcong terrain areas and extracts Fengcong landform units, individual Fenglin units, and Fenglin chains. The Fengcong area covers approximately two-thirds of the whole area, the individual Fenglin area covers approximately one-fourth, and the Fenglin chain area covers approximately one-tenth. The development of Fenglin has different stages in the Guilin area. This study provides data support for the detailed morphological study of karst terrain, and proposes a new research idea for the division and extraction of karst landform units.
... Los datos altimétricos constituyen información indispensable para estudios medioambientales, hidrológicos, de planificación urbana, etc. Existen Modelos Digitales de Elevación (MDE), de libre acceso que muestran con buena aproximación el comportamiento de la topografía en áreas extensas y brindan herramientas para la ejecución de estudios que no requieren precisión centimétrica en el valor de la altura referida al nivel medio del mar (Racoviteanu et al., 2007;Siart et al., 2009;Burgos, 2012;Grosse et al., 2012;Kinsey-Henderson y Wilkinson, 2013). Entre ellos, se destaca por su calidad y extensión en su uso el SRTM90 y el SRTM30 (Shuttle Radar Topography Mission) de 90 y 30 m de resolución respectivamente. ...
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RESUMEN La información topográfica de alta precisión es primordial en diferentes estudios del medioambiente. Es por ello que el objetivo del trabajo fue generar una grilla de base para la elaboración de un MDT (Modelo Digital del Terreno) para la ciudad de Bahía Blanca a partir de puntos obtenidos con métodos directos. De esta manera, se planteó el relevamiento planialtimétrico de las vías de circulación mediante técnicas de medición por satélites. La altura de cada punto relevado fue llevada a altura ortométrica utilizando el modelo geoidal GEOIDEAr. Para la validación del modelo se emplearon 44 puntos de control, de distinto origen y calidad. Se utilizaron puntos de la red de nivelación de precisión y de alta precisión del IGN, puntos de la Dirección de Geodesia de la provincia de Buenos Aires y puntos propios. En promedio, las diferencias entre el modelo generado y los puntos de control de las distintas fuentes no superan los 35 cm. El mismo mejoró la confianza en el valor altimétrico comparando con modelos preexistentes, principalmente en la zona céntrica. Palabras clave: MDT; GNSS; Bahía Blanca. DIGITAL TERRAIN MODEL THROUGH GNSS MEASURINGS ABSTRACT High-precision topographic information is essential in many environmental studies. This is why the objective of the work was to generate a base grid for the elaboration of a DTM (Digital Terrain Model) for Bahía Blanca city from points obtained by direct methods. In this way, the plane altimetric survey of the roadways was proposed through satellite measurement techniques. The height of each measured point was taken to orthometric height using the GEOIDEAr geoid model. For the validation of
... The extraction of lineaments has been found essential for resource exploration in large and semi-arid areas (Solomon and Ghebreab 2006;Siart et al. 2009 Sedrette and Rebaï (2016). The SAE approach was also used by many authors (Mallast et al. 2011;Vaz et al. 2012;Vasuki et al. 2014) to show the possibility of identifying the most interesting geological features in arid and desert areas that are difficult to access. ...
Article
The use of satellite images for mapping and analyzing linear structures and fracture systems in subsoil regions is essential to understand the subsurface groundwater path ways and traps. In this study, we apply Optimal Index Factor (OIF), principal component analysis (PCA), and directional filtering (Sobel) of several Landsat 8 bands for the wooded Waddai area in NE Chad. The application of the Sobel directional filter to these bands showed a robust performance for enhancing the discontinuity features and allowed better identification of the fault/fracture systems by the automated lineament extraction techniques. The results indicate that the ENE and WSW structural trends control the distribution and migration of groundwater, in good agreement with previous hydrological studies and published hydrogeological maps. New highly potential areas for groundwater exploration are identified on a lineament density map and verified by ground truth urban distribution.
... Karst depressions are detected through detailed geomorphological mapping and, more recently, by using remote-sensing techniques in combination with high-resolution topographic data. For example, Siart et al. (2009a), de Carvalho et al. (2013 and Pardo-Igúzquiza et al. (2013) combined digital elevation models with highresolution satellite images and GIS software, to develop semiautomatic techniques that facilitate the identification of surface karst features and their morphometric characteristics. Moreover, in order to obtain a better view of the sediment/bedrock interface characteristics in highly heterogeneous karst settings, geophysical methods have been employed as the most efficient tool for high-resolution imaging (Siart et al., 2009b(Siart et al., , 2010. ...
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We present an integrated study of subsurface and surficial karst landforms to unravel the uplift history of karst landscape in a tectonically‐active area. To this end, we apply a multidisciplinary approach by combining cave geomorphology and Th/U dating of speleothems with remote sensing plus geophysical imaging of surface landforms. We use as an example Mt. Menikio in northern Greece where four caves share well‐defined epiphreatic/shallow phreatic characteristics that are related to the distribution of surface and buried doline fields and provide evidence for three distinct water table stillstands (e.g. expressed as cave levels) now lying at ~130 m, ~800 m and ~1600 m a.m.s.l. Our dating constraints delimit the age of the lower water table stillstand prior to 77 ka ago and imply a maximum rate of relative base level drop of 0.45 mma‐1, which is consistent with relative tectonic uplift rate estimates along currently active normal faults. We interpret the elevation of the higher water table stillstands to reflect earlier phases of uplift related to the regional tectonic events associated with the development of the North Anatolian Fault and the Northern Aegean area. Our analysis shows that the combined study of epiphreatic/shallow phreatic caves and surficial karst landforms together, is a robust way to investigate the uplift history of a karst landscape in a tectonically‐active setting.
... They construed that the hydrologic response to intense, surge delivering precipitation occasions bears the signatures of the geomorphic structure of the channel network and of the characteristic slope lengths defining the drainage density of the basin [8]. C. Siart, O. Bubenzer and B. Eitel examines the application and quality of SRTM and ASTER DEMs, high resolution Quickbird satellite imagery and GIS techniques for the detection and mapping of karst morphology [9]. G.Brierley, in his examination considered geomorphic perspectives on ecosystem approaches to river management [10]. ...
Article
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Geo-spatial advancements like Remote Sensing (RS) and Geographical Information Systems (GIS) play an essential job in developing thematic maps and integrating analysis for mapping, managing and monitoring the natural resources. RS and GIS technologies have advanced a new era in the field of applied geology and geomorphology. Geomorphology is the science of landforms present on the Earth’s surface and their systematic study is important and unique in order to interpret them as signatures of the past and ongoing geological processes. The present examination plans to delineate geomorphological features in the district of Visakhapatnam in view of visual image translation strategies. The study area mainly comprises Pediment slope(27.39%) followed by Structural hill(25.51%) and Pediplain shallow(18.06%).These maps would be useful in further analysis for natural Earth resources planning, management and decision making. Thematic maps of geomorphology have been generated on satellite data. Standard visual elucidation methods according to the standards given by NRSA have been followed and portrayed on-screen digitations of features.
... DEMs can be obtained by field measurement and remote sensing techniques. While the accuracy of the field measurement method is quite high, it is also time consuming and costly, especially in hard-to-reach areas [9,10]. Remote sensing has become the primary means of obtaining DEMs due to its near ideal characteristics in terms of coverage, and spatial and temporal resolution [11]. ...
Preprint
Digital Elevation Models (DEMs) are widely used in geographic and environmental studies. In the current work, the fusion of multi-source DEMs is investigated to improve the overall accuracy of public domain DEMs. Multi-scale decomposition is an important analytical method in data fusion. Three multi-scale decomposition methods – the wavelet transform (WT), bidimensional empirical mode decomposition (BEMD) and nonlinear adaptive multi-scale decomposition (N-AMD) - are applied to the 1-arc-second Shuttle Radar Topography Mission Global digital elevation model (SRTM-1 DEM) and the Advanced Land Observing Satellite World 3D – 30 m digital surface model (AW3D30 DSM) in China. Of these, the WT and BEMD are popular image fusion methods. A new approach for DEM fusion is developed using N-AMD (which is originally invented to remove the cycle from sunspots). Subsequently, a window-based rule is proposed for the fusion of corresponding frequency components obtained by these methods. Quantitative results show that N-AMD is more suitable for multi-scale fusion of multi-source DEMs, taking the ice cloud and land elevation satellite (ICESat) global land surface altimetry data as a reference. The vertical accuracy of the fused DEM shows significant improvements of 29.6% and 19.3% in a mountainous region and 27.4% and 15.5% in a low-relief region, compared to the SRTM-1 and AW3D30 respectively. Furthermore, a slope position-based linear regression method is developed to calibrate the fused DEM for different slope position classes, by investigating the distribution of the fused DEM error with topography. The results indicate that the accuracy of the DEM calibrated by this method is improved by 16% and 13.6%, compared to the fused DEM in the mountainous region and low-relief region respectively, proving that it is a practical and simple means of further increasing the accuracy of the fused DEM.
... V posledných desaťročiach významne narástla úloha geografických informačných systémov (GIS) v geomorfologickom výskume. GIS vytvorili veľké možnosti pri tvorbe a používaní digitálneho terénneho modelu (Mukherjee et al. 2013), použití štatistických metód v geomorfologickom výskume (Clerici 2002), leteckých či satelitných snímok v geomorfológii (Siart et al. 2009) a v mnohých ďalších oblastiach. ...
Article
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The Žiarska kotlina basin is one of the intramontane basins of the Western Carpathians. Geomorphological analysis of river terraces, thickness of Quaternary sediments , density of landslides and gullies, morpholineaments and faults was carried out using the Geographical Information Systems (GIS). The aim of the analysis was to understand the role of the neotectonics. The river terraces on the right bank of the River Hron are higher than those on the left bank showing the irregular neo-tectonic evolution of the area. The difference in height of the terraces on the left bank and right bank varies from 11 to 25 meters near Žiar nad Hronom and from 20 to 23 meters near Dolná Ždaňa. The interpolation of the Quaternary cover thickness shows three regions with a relatively thick quaternary cover, two of them in contact with the adjacent mountains and one along the alluvium of the Hron. The density of gullies on the right bank of the Hron is high. The density of landslides is biggest on the western margin of the basin. Analysis of the river terraces suggests that the Žiarska kotlina basin has not uniformly subsided, and the neotectonic activity is different in its individual parts.
... Opportunities exist to develop similar landscape classifications from other existing geomorphological maps (e.g. Jasiewicz et al., 2014; Rinaldi et al., 2013;Gawde et al., 2009;Siart et al., 2009;Johnson and Fecko, 2008;etc.). It should be noted that the methodology presented in this study is not limited to a land cover and land use application, but depending on user requirements, data availability and study regions, it could be repeated using different variables to incorporate, for example, species distributions, climatic, cultural or historical factors. ...
Article
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This study presents a novel landscape classification map of the Republic of Ireland and is the first to identify broad landscape classes by incorporating physiographic and land cover data. The landscape classification responds to commitments to identify and classify the Irish landscape as a signatory to the European Landscape Convention. The methodology applied a series of clustering iterations to determine an objective multivariate classification of physiographic landscape units and land cover datasets. The classification results determined nine statistically significant landscape classes and the development of a landscape classification map at a national scale. A statistical breakdown of land cover area and diversity of each class was interpreted, and a comparison was extended using independent descriptive variables including farmland use intensity, elevation, and dominant soil type. Each class depicts unique spatial and composition characteristics, from coastal, lowland and elevated, to distinct and dominating land cover types, further explained by the descriptive variables. The significance of individual classes and success of the classification is discussed with particular reference to the wider applicability of the map. The transferability of the methodology to other existing physiographic maps and environmental datasets to generate new landscape classifications is also considered. This novel work facilitates the development of a strategic framework to efficiently monitor, compare and analyse ecological and other land use data that is spatially representative of the distribution and extent of land cover in the Irish countryside.
... Hydrological modelling using LiDAR and GIS can allow flooding projection models to be developed in catchments ( Merwade et al., 2008, Gallegos et al., 2009. When developing complex hydrological models to assess flood risks in catchments, Digital Elevation Models (DEMs) are utilized in a GIS to obtain basic geographical factors -for example, stream systems, stream headings, catchment geometry in terms of distributed information on land use, soil, and climate information ( Siart et al., 2009 ). GIS is used to extend both subjective and quantitative effects of floods and runoff , and spatial-based hydrological models have been effectively used for flood investigation in shoreline areas ( Sarker andSivertun, 2011 , Zerger andWealands, 2004 ). ...
Thesis
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Coastal climate impact can affect coastal areas in a variety of ways, such as flooding, storm surges, reduction in beach sands and increased beach erosion. While each of these can have major impacts on the operation of coastal drainage systems, this thesis focuses on coastal and riverine
... o mapeamento e previsão de diferentes processos, tais como: inundação e dinâmica fluvial (KLEMAS, 2014;RAHMAN & DI, 2017), dinâmica de dunas (HERMAS et al. 2012;HUGENHOLTZ et al., 2012), erosões (MATA et al., 2007;LANE et al., 2003;VRIELING, 2006), movimento de massa (GUIMARÃES et al., 2008, METTERNICHT et al., 2005SCAIONI et al. 2014;TOFANI et al., 2013), detecção de feições cársticas (CARVALHO JUNIOR et al., 2008SIART et al., 2009), geomorfologia glacial (KÄAB et al., 2008), entre outros. Assim, informações geoespaciais derivados de sensoriamento remoto são cada vez mais usados em sistemas de apoio à decisão para a definição de políticas públicas, gestão territorial, monitoramento ambiental e sistemas de alertas de desastres em diversas escalas (TRALLI et al., 2005; VAN WESTEN, 2013). ...
Article
O sensoriamento remoto permite a obtenção de informações consistentes, atualizadas e relativamente precisas para o monitoramento de corpos hídricos, auxiliando nas atividades de conservação e manejo das áreas úmidas, análise de inundações, modelos de previsão de desastres, entre outros. O presente artigo apresenta uma revisão das inovações tecnológicas do sensoriamento remoto aplicadas ao monitoramento de áreas inundáveis. Recentemente, essa área do conhecimento atravessa por diversas transformações com expressivo impacto na aquisição e processamento de dados. Portanto, a revisão foca nos estudos desenvolvidos com sensoriamento remoto radar e óptico para a detecção da superfície d’água e discute as perspectivas do advento de novas tecnologias, tais como: processamento em nuvens, imagens com alta resolução temporal e novos algoritmos para o processamento dos dados. O processamento em nuvem permite um acesso a coleções volumosas de imagens orbitais de observação da Terra para um grande número usuários, o que era até pouco tempo inviável. O advento das constelações de nanossatélites transforma completamente o processo de aquisição das imagens, que resulta na diminuição significativa dos custos, obtenção de dados diários e com alta resolução espacial. A conjunção desses fatores proporciona a aceleração de troca de conhecimento e converge para uma observação global integrada.
... In the last two decades, various organizations have released different versions of GDEMs and tried to improve their spatial resolution from 1 arc-minute (ETOPO1) in the mid-1990s to 3 arc-seconds (Shuttle Radar Topography Mission GDEM (SRTM GDEM)) in 2007 and 1 arc-second (Advanced Spaceborne Thermal Emission and Reflection GDEM (ASTER GDEM)) in 2009 (Varga and Tomislav 2015). The aforementioned improvement, not only has enhanced our insight into the Earth's surface, but also has increased applications of these models in various earth science fields including modelling water flow (Singh and Jain 2003), geomorphology (Siart, Bubenzer, and Eitel 2009;Rebai and Moussi 2019), computing local geoid models (Rebaï et al. 2018), and disaster monitoring (Schumann et al. 2008). ...
Article
Global digital elevation models (GDEMs) are one of the most important sources of elevation data. Like other spatial datasets, GDEMs are inevitably affected by various types of errors in both vertical and horizontal dimensions. One of the main sources of horizontal errors is georeferencing error which in steep areas intensifies the vertical error. Since horizontal and vertical errors are interwoven with one another, any error introduced in horizontal dimension influences its vertical counterpart. In this paper, for the first time, we intend to answer this question: to what extent the impact of georeferencing error is really important in vertical accuracy of GDEMs and their vertical comparison. Hence, the main purposes of this study are evaluation of georeferencing effects on (i) the vertical accuracy of GDEMs and (ii) vertical comparison between GDEMs. In this regard, Advanced Spaceborne Thermal Emission and Reflection (ASTER), Shuttle Radar Topography Mission (SRTM), and Advanced Land Observing Satellite (ALOS) World 3D-30 m (AW3D30) GDEMs over three different study areas (BumeHen, TazehAbad and Sainte-Maxime regions) were used and assessed. In order to assess the effects of georeferencing error on GDEMs accuracy, studies were conducted in two general categories, namely Local to Global (LG) and Global to Global (GG). In the first category, these effects were studied on vertical and horizontal differences of ASTER, AW3D30, and SRTM GDEMs with their corresponding reference DEMs (REFDEMs). In the second category, these effects were assessed on vertical and horizontal differences of ASTER and SRTM GDEMs with AW3D30 GDEM. To this end, prior to making GDEMs georeferencing consistent, they were vertically assessed. For the sake of consistency of GDEMs georeferencing, a registration process was performed and then, the registered GDEMs were vertically and horizontally assessed. After the registration process, in the first category, 4.4%, 13%, and 3.3% and in the second category 2.3%, 5%, and 1.2% improvement occurred on average root mean square error (RMSE) over all GDEMs for BumeHen, TazehAbad and Sainte-Maxime regions, respectively. These results refer to the fact that GDEM registration always increases their vertical accuracy, which is in fact originated from the improvement in GDEM georeferencing consistency. Experimental results also indicate that the improvement rate of vertical errors after the DEM registration process is directly related to terrain slope angle. From another perspective, we illustrated that in general the amounts of achieved improvements in GDEMs vertical accuracy are much smaller than their nominal accuracies. Finally, our results show that the effect of horizontal error on vertical comparison between GDEMs is unavoidable, but this amount of error can be ignored because the ratio of improvements occurred in the GDEMs with respect to their nominal accuracies is very low.
... The geomorphology was studied with the help of aerial photographs, satellite images, and digital elevation model (DEM) data (Siart et al. 2009). Aerial photos captured in the years 1954 and 1972 were obtained from Nepal's Forest Research and Training Center and converted into mosaic images, which were analyzed in Geographic Information System Environment (ArcGIS Pro 2.7.0). High-resolution images for the years 2005 (Quickbird), 2010 (George-1), and 2020 (WorldView-2) were obtained from the Remote Sensing Technology Center of Japan. ...
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The Nepalese Himalayas is one of the world’s most active mountain belts, with widespread natural hazards of various types, including landslides, which claim numerous lives and properties in Nepal. Landslides occur due to the combined effects of seismic activity, monsoon rainfall, and improper land-use practices. The prevention and mitigation of landslides are challenging for countries like Nepal, however, low-cost techniques such as bioengineering with low-cost early warning systems have been implemented in recent decades. The Methum landslide near Lalitpur was selected as a case study to investigate the landscape dynamics along with triggering factors, and to evaluate the effectiveness of a landslide early warning system (LEWS). The study assessed aerial photos, satellite images, and precipitation records and conducted multiple field visits to analyze patterns of landslide evolution, landslide risk, and potential triggers. Heavy rainfall, sloped terrace farming, and earthquakes are identified as major landslide triggers. LEWS, installed, measures rainfall, soil moisture, and displacement activity and generates an alarm if any of these parameters exceed the threshold set. This monitoring system is a cost-effective technique and exemplifies the reduction of landslide risk at the community level in the landslide-prone mid-hills of Nepal.
... In current times, there has been an emphasis on various methods like Global Positioning System (GPS), Geo-Spatial Technology, Remote Sensing and Geographic Information System (RS and GIS), in taking care of the issues of land use, and making arrangements for water resource management during a morphometric analysis of the watershed (Abboud and Nofal 2017;Abdeta et al. 2020). GIS-based assessment utilizing SRTM and ASTER DEM data has given exact, quick and economical route of investigating hydrological frameworks (Start et al. 2009;Telfer et al. 2015;White et al. 2015). Previously morphometric parameters of a watershed were extracted from geographical maps or field reviews. ...
Article
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Geo-informatics techniques are viable being utilized in recent decades as a critical apparatus in deciding the quantitative portrayal of morphometry of a watershed. These procedures portray the high exactness of mapping and estimation of the morphometric analysis. The point of this study is, hence, to break down the GIS (Geographic information System)-based morphometric exercises of the River Ganga basin. This analysis requires depiction of every single existing stream. The estimation and investigation of the basin and its seventeen noteworthy sub-watersheds are carried on GIS stage. The parameters required as inputs are pour point, stream order map, and DEM (Digital Elevation Model). The results uncovered that the mean estimation of Form Factor (Ff) is 0.29 and Compactness coefficient (Cc) is 3.16, which demonstrates the shape of the watershed is not circular, it is elongated. The mean estimation of Stream Frequency (Sf) is 1.22 which be evidence for that the basin has reduced infiltration capacity. The value 2.87 of bifurcation Ratio (Rb) proposes that the watershed is steady. The distinctive estimations of Texture Ratio (T) recommend that the watershed has a fluctuating slope yet plain at the more significant part of the area. The prioritization of the sub-watersheds has been made using a novel approach Weighted Sum Priority Model (WSPM). Combined rank for each sub-watershed has been calculated using the WSPM model. Based on that model, it can likewise be reasoned that the sub-watersheds SW15 and SW16 are more soil erosion-prone sub-watersheds among all the seventeen sub-watersheds. Results of the study can be further utilized for prioritizing watershed for soil erosion-prone areas and also for watershed management planning zones.
... The high-resolution and LiDAR DEMs have been used to delineate the channel network and to calculate its main morphological properties (Lashermes et al., 2007;Lee & Kim, 2011;Passalacqua et al., 2010;Moussa et al., 2011). Many worldwide open DEM data sources such as SRTM DEMs and ASTER GDEM have been used in catchment morphological, hydrology, geomorphological mapping, and morphometric feature identification (Lefavour & Alsdorf, 2005;Hancock et al., 2006;Hayakawa et al., 2008;Siart et al., 2009;Sreedevi et al., 2009;Ehsani et al., 2010;Li & Wong, 2010). Determining reasonable DAT is the key step in applying DEM to hydrological analysis. ...
Article
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How and to which extent terrain factors affecting the drainage area threshold (DAT) are disputable. This paper uses principal component analysis (PCA) and correlation analysis to study the influence degree of terrain factors on DAT. Firstly, 22 watersheds, locating in the severe soil erosion region (SSER) of Loess Plateau of China, are picked out as the example areas. The purpose of the mean change point method (MCP) to detect the relationship between DAT and gully density (GD) is to get a reasonable DAT. Secondly, nine terrain factors are calculated, and their statistical values are compared and put in the matrix to clear the different effects on DAT. Finally, the effects of statistical eigenvalues of terrain factors on DAT are compared with PCA and the correlation analysis. According to the PCA, the nine terrain factors are summarized into three principal components, which are slope, height variation, and relief factor. By calculating the score weighted by each factor coefficient matrix and eigenvalue, the result states that slope (S), terrain curvatures (K), and surface roughness (SR) are the factors that have great influence on DAT. Meanwhile, the results of correlation analysis indicate that S, SR, and K have exerted a great influence on the DAT, and the significance level was above 0.05. Both the results of PCA and correlation analysis make clear that the slope is the most direct and influential factor affecting DAT, while other factors are more or less related to slope directly and indirectly. The result implies that the vertical variation of terrain has a strong correlation with the slope, and also has a great influence on DAT. This research not only would be of great significance to recognize the mechanism of gully development, but also able to provide a scientific reference for soil and water conservation in the Loess Plateau.
... Thus, it becomes a fundamental element in comprehensive environmental and geomorphological studies. Dems significantly contribute to solving geomorphological, agricultural, hydrological, geological, pedological, and ecological problems (Pulighe and Fava, 2017) and their modeling (Marzolff and Poesen, 2009;Schumann et al., 2008;Siart et al., 2009). DEMs could also be extracted from digital stereo imagery Pulighe and Fava, 2017). ...
Conference Paper
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As a quantitative and numerical representation of earth surface topography, Digital Elevation Models (DEMs) are widely used in several applications including geological, hydrological, and geographical Aspects. With the availability of several types of DEMs, various intrinsic errors may be incorporated due to sensor acquisition inconveniences, or processing techniques compared to the actual land surface measurements. Consequently, this study aims to analysis and test the vertical accuracy of NASADEM, Advanced Spaceborne Thermal Emission and Reflection Radiometer–Global Digital Elevation Model (ASTER GDEM) and Advanced Land Observing Satellite (ALOS) Phased Array L-type band Synthetic Aperture Radar (PALSAR) DEM compared to the actual ground control points (GCPs) derived from topographic maps through calculating Mean Absolute Percentage Error (MAPE) and Root Mean Square Error (RMSE). Our results revealed the sublimity of ALOS PALSAR DEM over NASADEM and ASTER GDEM. Thus, ALOS PALSAR DEM is recommended for further geomorphological studies.
... For a bare earth area such as a coastal or open riverbank, any geomorphological changes are easily detected using several image analyses, such as change detection, image classification, thresholding, and other remote-sensing related methods [21][22][23][24][25][26][27][28][29]. Both satellite imageries provided high-resolution elevation data at the global scale and were used by previous researchers to evaluate changes on the earth's surface over time [30][31][32][33][34][35][36][37]. Most of them used the digital elevation model (DEM) uncertainty process based on the Monte Carlo approach [38] with post-processing tools in SFM-georeferencing software [39]. ...
Article
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Estimating surface elevation changes in mangrove forests requires a technique to filterthe mangrove canopy and quantify the changes underneath. Hence, this study estimates surfaceelevation changes underneath the mangrove canopy through vegetation filtering and Difference ofDEM (DoD) techniques using two epochs of unmanned aerial vehicle (UAV) data carried out during2016 and 2017. A novel filtering algorithm named Surface estimation from Nearest Elevation andRepetitive Lowering (SNERL) is used to estimate the elevation height underneath the mangrovecanopy. Consequently, DoD technique is used to quantify the elevation change rates at the groundsurface, which comprise erosion, accretion, and sedimentation. The significant findings showed thatregion of interest (ROI) 5 experienced the highest volumetric accretion (surface raising) at 0.566 cm3.The most increased erosion (surface lowering) was identified at ROI 8 at−2.469 cm3. In contrast,for vertical change average rates, ROI 6 experienced the highest vertical accretion (surface raising)at 1.281 m. In comparison, the most increased vertical erosion (surface lowering) was spotted atROI 3 at−0.568 m. The change detection map and the rates of surface elevation changes at KilimRiver enabled authorities to understand the situation thoroughly and indicate the future situation,including its interaction with sea-level rise impacts.
... Among the reasons for this; It is low in cost, remains up-to-date because it can be obtained quickly, and images can be displayed as covering very large areas (Erbay, 2005). Since almost all satellite images are digital and contain location information, it forms a basis for analysis and queries for GIS and for almost every study in remote sensing (Erbay, 2005;Geymen, 2016;Siart et al, 2009). The Landsat-8 satellite was developed as a collaboration between NASA and the US Geological Survey (USGS) and was launched in California on February 11, 2013 (URL 1). ...
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The sustainable use of water and soil, which are indispensable for living things, is closely related to the concept of land use. While land use is becoming gradually modern as a necessity of the age, urbanization and industrialization are also gaining great importance. So much so that, in Turkey, where agriculture-based economy was emphasized until the 1980s, interest in exports of industrial products has increased in recent years and industrial investments especially in the Marmara region have increased considerably. This situation has increased job opportunities due to the industrialization developing in the region and has led to an increase in the population in parallel. The structure process has accelerated in order to meet the needs of the increasing population.Basin areas, which contain a wide variety of classes, are among the regions that are highly affected by these changes. Within the scope of the study, Elmalı Basin, which is used to supply potable and utility water to the province of Istanbul, was chosen as the study area. Within the scope of the research, the temporal change of the land use in Elmalı Basin has been investigated by using Landsat-8 satellite with a spatial resolution of 30 meters for the years 2013, 2015, 2018 and 2020 taking advantage of Geographical Information Systems (GIS) and Remote Sensing (RS) technologies. Classification was made with support vector machines, one of the controlled classification methods on satellite images, and the changes in land use were evaluated by comparing the images of working years.
... Remote sensing is applicable to many different types of geomorphological studies: fluvial, e.g., as in References [12,13], karst, e.g., as in References [14,15], glacial, e.g., as in Reference [16], and particularly in coastal geomorphology, e.g., as in References [17,18]. Figure 1 shows a number of Web of sciences core collection (WoSCC) research articles in last 20 years for topics of "Remote sensing" and topic of "Remote sensing" + "coastal geomorphology". The figure shows trends in research on the topics. ...
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This study investigates the quality and accuracy of remote sensing data in beach surveys based on three different data sources covering a 10-year period (2011–2021). Orthophotos from State Geodetic Administration Geoportal and satellite imagery from Google Earth were compared with orthophotos generated from UAV using ArcGIS Pro and Drone2Map. The beach area and length of 20 beaches on the island of Hvar were measured using each data source from different years. The average deviation for beach area (−2.3 to 5.6%) and length (−1 to 2.7%) was determined (without outliers). This study confirms that linear feature measurement is more accurate than polygon-based measurement. Hence, smaller beach areas were associated with higher errors. Furthermore, it was observed that morphological complexity of the beach may also affect the measurement accuracy. This work showed that different remote sensing sources could be used for relatively accurate beach surveys, as there is no statistically significant difference between the calculated errors. However, special care should always be addressed to the definition of errors.
... Fluvial erosion generally dictates a hydrologically connected landscape (Wang and Liu, 2006;Mark, 1988) suggesting that the majority of such features are erroneous and should be eliminated from the topographic profile (Mark, 1988;Senevirathne and Willgoose, 2013;Lindsay andCreed, 2005a, 2005b). However, larger features may in fact be natural regions of negative relief (e.g. de Carvalho Junior et al., 2014;Siart et al., 2009;Smith et al., 2013). In a fluvial context, negative relief formations may include: palaeochannels, riparian lagoons and pools, that will remain inundated following floodwater recession (Lewin and Ashworth, 2014;Smith et al., 2013). ...
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Medium-resolution DEMs have limited applicability to flood mapping in large river systems within data sparse regions such as Sub-Saharan Africa. We present a novel approach for the enhancement of the SRTM (30?m) Digital Elevation Model (DEM) in The Gambia, West Africa: A time-series analysis of flood frequency and land cover was used to delineate differences in the vertical limits between morphological units within an alluvial floodplain. Combined with supplementary river stage data and vegetation removal techniques, these methods were used to improve the estimation of bare-earth terrain in flood modelling applications for a region with no access to high-resolution alternatives. The results demonstrate an improvement in floodplain topography for the River Gambia. The technique allows the reestablishment of small-scale complex morphology, instrumental in the routing of floodwater within a noise-filled DEM. The technique will be beneficial to flood-risk modelling applications within data sparse regions
... Hydrological modelling using LiDAR and GIS can allow flooding projection models to be developed in catchments (Merwade et al., 2008, Gallegos et al., 2009. When developing complex hydrological models to assess flood risks in catchments, Digital Elevation Models (DEMs) are utilized in a GIS to obtain basic geographical factors -for example, stream systems, stream headings, catchment geometry in terms of distributed information on land use, soil, and climate information (Siart et al., 2009). GIS is used to extend both subjective and quantitative effects of floods and runoff , and spatial-based hydrological models have been effectively used for flood investigation in shoreline areas (Sarker andSivertun, 2011, Zerger andWealands, 2004). ...
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Coastal climate impact can affect coastal areas in a variety of ways, such as flooding, storm surges, reduction in beach sands and increased beach erosion. While each of these can have major impacts on the operation of coastal drainage systems, this thesis focuses on coastal and riverine flooding in coastal areas. Coastal flood risk varies within Australia, with the northern parts in the cyclone belt most affected and high levels of risk similar to other Asian countries. However, in Australia, the responsibility for managing coastal areas is shared between the Commonwealth government, Australian states and territories, and local governments. Strategies for floodplain management to reduce and control flooding are best implemented at the land use planning stage. Local governments make local decisions about coastal flood risk management through the assessment and approval of planning permit applications. Statutory planning by local government is informed by policies related to coastal flooding and coastal erosion, advice from government departments, agencies, experts and local community experts. The West Gippsland Catchment Management Authority (WGCMA) works with local communities, Victorian State Emergency Services (VCSES), local government authorities (LGAs), and other local organizations to prepare the West Gippsland Flood Management Strategy (WGFMS). The strategy aims at identifying significant flood risks, mitigating those risks, and establishing a set of priorities for implementation of the strategy over a ten-year period. The Bass Coast Shire Council (BCSC) region has experienced significant flooding over the last few decades, causing the closure of roads, landslides and erosion. Wonthaggi was particularly affected during this period with roads were flooded causing the northern part of the city of Wonthaggi to be closed in the worst cases. Climate change and increased exposure through the growth of urban population have dramatically increased the frequency and the severity of flood events on human populations. Traditionally, while GIS has provided spatial data management, it has had limitations in modelling capability to solve complex hydrology problems such as flood events. Therefore, it has not been relied upon by decision-makers in the coastal management sector. Functionality improvements are therefore required to improve the processing or analytical capabilities of GIS in hydrology to provide more certainty for decision-makers. This research shows how the spatial data (LiDAR, Road, building, aerial photo) can be primarily processed by GIS and how by adopting the spatial analysis routines associated with hydrology these problems can be overcome. The aim of this research is to refine GIS-embedded hydrological modelling so they can be used to help communities better understand their exposure to flood risk and give them more control about how to adapt and respond. The research develops a new Spatial Decision Support System (SDSS) to improve the implementation of coastal flooding risk assessment and management in Victoria, Australia. It is a solution integrating a range of approaches including, Light Detection and Ranging (Rata et al., 2014), GIS (Petroselli and sensing, 2012), hydrological models, numerical models, flood risk modelling, and multi-criteria techniques. Bass Coast Shire Council is an interesting study region for coastal flooding as it involves (i) a high rainfall area, (ii) and a major river meeting coastal area affected by storm surges, with frequent flooding of urban areas. Also, very high-quality Digital Elevation Model (DEM) data is available from the Victorian Government to support first-pass screening of coastal risks from flooding. The methods include using advanced GIS hydrology modelling and LiDAR digital elevation data to determine surface runoff to evaluate the flood risk for BCSC. This methodology addresses the limitations in flood hazard modelling mentioned above and gives a logical basis to estimate tidal impacts on flooding, and the impact and changes in atmospheric conditions, including precipitation and sea levels. This study examines how GIS hydrological modelling and LiDAR digital elevation data can be used to map and visualise flood risk in coastal built-up areas in BCSC. While this kind of visualisation is often used for the assessment of flood impacts to infrastructure risk, it has not been utilized in the BCSC. Previous research identified terrestrial areas at risk of flooding using a conceptual hydrological model (Pourali et al., 2014b) that models the flood-risk regions and provides flooding extent maps for the BCSC. It examined the consequences of various components influencing flooding for use in creating a framework to manage flood risk. The BCSC has recognised the benefits of combining these techniques that allow them to analyse data, deal with the problems, create intuitive visualization methods, and make decisions about addressing flood risk. The SDSS involves a GIS-embedded hydrological model that interlinks data integration and processing systems that interact through a linear cascade. Each stage of the cascade produces results which are input into the next model in a modelling chain hierarchy. The output involves GIS-based hydrological modelling to improve the implementation of coastal flood risk management plans developed by local governments. The SDSS also derives a set of Coastal Climate Change (CCC) flood risk assessment parameters (performance indicators), such as land use, settlement, infrastructure and other relevant indicators for coastal and bayside ecosystems. By adopting the SDSS, coastal managers will be able to systematically compare alternative coastal flood-risk management plans and make decisions about the most appropriate option. By integrating relevant models within a structured framework, the system will promote transparency of policy development and flood risk management. This thesis focuses on extending the spatial data handling capability of GIS to integrate climatic and other spatial data to help local governments with coastal exposure develop programs to adapt to climate change. The SDSS will assist planners to prepare for changing climate conditions. BCSC is a municipal government body with a coastal boundary and has assisted in the development and testing of the SDSS and derived many benefits from using the SDSS developed as a result of this research. Local governments at risk of coastal flooding that use the SDSS can use the Google Earth data sharing tool to determine appropriate land use controls to manage long-term flood risk to human settlement. The present research describes an attempt to develop a Spatial Decision Support System (SDSS) to aid decision-makers to identify the proper location of new settlements where additional land development could be located based on decision rules. Also presented is an online decision-support tool that all stakeholders can use to share the results.
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Modelagens geomorfológicas da superfície terrestre tem se beneficiado do aprimoramento das geotecnologias, a exemplo do Modelo Digital de Elevação (MDE) derivado dos dados remotos por proporcionarem uma disponibilidade de informações altimétricas com cobertura em nível global. Entretanto, tais vantagens são expressas pelo grau de qualidade dos dados. O objetivo deste estudo foi analisar a acurácia altimétrica dos MDEs derivados dos dados ALOS PALSAR (RTC) e o ASTER (GDEM) Versão 3 para o mapeamento de uso do solo do município de Recife-PE, por meio da normativa de Precisão Cartográfica para produtos digitais (PEC-PCD), nas escalas de 1:250.000; 1:50.000 e 1:100.000. A metodologia consistiu em analisar as discrepâncias entre os MDEs e as altitudes ortométricas fornecidas por pontos de referência do Sistema Geodésico Brasileiro. Os dados foram testados por meio do RMSE e regressões lineares baseadas no R² e RMS. Como resultado, o ALOS PALSAR apresentou menores valores de RMSE e desvio padrão, indicando que apresenta maior acurácia em relação ao ASTER. As áreas urbanas apresentaram variações de discrepância média entre 0,1 e 3m para os dados ALOS PALSAR enquanto o ASTER foram entre 6 e 8 m, porém em áreas de vegetação densa, ambos os dados apresentaram discrepâncias acima de 10 m.
Chapter
Remote data have frequently been used in fluvial geomorphology to observe landforms and derive geomorphological data such as water depth, grain size, and digital elevation models. This article reviews the types and historical development of remote data used in fluvial geomorphology and introduces examples of recent applications. The focus is on raw remote data and their derivatives, and both classic and recent techniques. Further consideration is given to current problems with the use of remote data in fluvial geomorphology and related future perspectives.
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Karst systems hide their main mechanisms of morphogenesis in the subsurface, where the interaction of slightly acidified waters with soluble rocks allows the creation of voids and the interconnection of flows, accelerating erosive processes that are not always visible. One of the most important superficial expressions of these mechanisms linked to speleogenesis are dolines, features considered elementary in these environments. The present research had as its main object karst depressions, from which concepts, genetic typologies and main morphologies were revisited in works carried out in Brazil and in the world. The mapping of these features has been carried out for a long time and allows for a series of interpretations of a geomorphological and environmental nature. However, the job of detecting and delimiting dolines comes up against the resolution of the available databases, difficulties in establishing limits in the field or through visual analysis in images, great consumption of time and work, in addition to carrying a strong bias of subjectivity. In this sense, several more recent works have been using modern techniques and high-resolution databases for the detection of dolines, many carried out with a certain level of automation, especially with the use of Digital Elevation Models-MDE's. Based on these experiences and aiming to identify the dolinas in the upper Rio Corrente region and the Environmental Protection Area of the Rio Vermelho Springs (APA-NRV), northeast of Goiás, the mapping of these features was carried out at three different scales. In a first approach, dolines were identified primarily through fieldwork in a small area close to Tarimba Cave, and the results were compared with the visual analysis of MDE's generated with ALOS-PALSAR data and Unmanned Aerial Vehicle (UAV) . Karst depressions for a comprehensive scale were also semi-automatically detected throughout the upper Corrente river basin with SRTM and ALOS-PALSAR data. Finally, a mapping of a significant area was carried out with the aid of the UAV and dolines were automatically detected in the central area of the APA-NRV, with several cave systems. The results showed the importance of choosing the appropriate database, resolution and size of the coverage area. Based on the results, it was possible to establish the most karstified areas, the most common types of dolines and the main processes acting in the configuration of the local relief, with an important role of the materials and the double erosive, superficial and underground dynamics.
Article
In watershed modeling, the traditional practice of arbitrarily filling topographic depressions in digital elevation models (DEMs) has raised concerns. Advanced high‐resolution remote sensing techniques, including airborne scanning laser altimetry (LiDAR), can identify naturally occurring depressions that impact overland flow. In this study, we used an ensemble physical and statistical modeling approach, i.e., a 2D hydraulic model and two‐point connectivity statistics, to quantify the effects of depressions on high‐resolution overland flow patterns across spatial scales and their temporal variations in single storm events. Computations for both models were implemented using graphic processing unit (GPU)‐accelerated computing. The changes in connectivity statistics for overland flow patterns between LiDAR‐derived DEMs with (original) and without (filled) depressions were used to represent the shifts of overland flow response to depressions. The results show that depressions can either decrease or increase (to a lesser degree and shorter duration) the probability that any two points (grid locations) are hydraulically connected by overland flow pathways. We used a watershed‐specific indicator, i.e., macro‐connectivity states (Φ), to describe the spatiotemporal thresholds of connectivity variability caused by depressions. Four states of Φ are identified in a studied watershed, and each state represents different magnitudes of connectivity and connectivity changes (caused by depressions). The magnitude of connectivity variability corresponds to the states of Φ, which depend on the topological relationship between depressions, the rising/recession limb, and the total rainfall amount in a storm event. In addition, spatial distributions of connectivity variability correlate with the density of depression locations and their physical structures, which cause changes in streamflow discharge magnitude. Therefore, this study suggests that depressions are “nontrivial” in watershed modeling, and their impacts on overland flow should not be neglected. Connectivity statistics at different spatial scales and time points within a watershed provide new insights for characterizing the distributed and accumulated effects of depressions on overland flow.
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Geomorphometry is the science of quantitative land surface analysis also known under names Digital Terrain Modelling, Digital Terrain Analysis and/or relief analysis. It has deep roots in geomorphology and finally oriented towards supervised and unsupervised landform classification. This volume is a contribution to the 4th bi-annual global meeting of the International Society for Geomorphometry (ISG). Every two years worldwide top specialists on geocomputation of digital elevation data meet to discuss existing and emerging trends of DEM acquisition, processing and application. Themes in this volume revolve around three main threads. Data acquisition concentrates on different methods of high resolution of new elevation data acquisition: from local through regional to world-wide scale. Geoprocessing thread focuses on novel method of computation of big elevation data as well as improvement of existing ones. Finally application path presents among others how different data and methods gives a new prompt to the various aspects of monitoring natural processes and natural hazards geomodelling. However the interdisciplinary nature of geomorphometry makes it a key science for natural hazards: from land observations which can serve as ground truth to mathematical models. Therefore the key theme of the Conference and workshops Geomorphometry 2015 is Geomorphometry for natural hazards geomodelling. Changes in appearance of land surface are either incremental or more abrupt if caused by catastrophic processes such as floods, earthquakes, landslides, tornadoes, storms, etc. The possibility of prediction of resultant hazards is one of the most important challenges for many disciplines of environmental sciences, geomorphological modelling had focused on incremental processes with catastrophic processes or natural hazards receiving less attention. Development of new technologies of data acquisition and new software as well as monitoring of Earth surface both on global and local scales provides a growing amount of worldwide-extend high resolution DEMs which require a new kind of geomorphometric tools capable of handling, analyzing, and visualizing large quantities of data in real time.
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Connectivity is a state-of-the-art concept that improves the current understanding of hydrological processes at multiple scales. Two-point connectivity statistics provide a promising approach to quantify hydrologic connectivity, which measures the probability of any two nodes in a hydrologically relevant pattern that are connected based on their separation distances. However, limited computational capacity has been the main constraint for implementations in large gridded patterns (>1 million nodes). Here, we propose a new algorithm based on array vectorization and convolutional neural network operators (convolution and pooling) that leverages parallel computational capacity of a GPU. Test results suggested that the new algorithm significantly increases the computational efficiency and is also sensitive to the variability of connectivity states and robust to complex topography. We envision that our algorithm can pave the way for investigating behaviors in large-scale (e.g., watershed) processes, based on quantifying the connectivity of gridded hydrological patterns and digital elevation models.
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Digital elevation models (DEM) are good digital representations of the relief structures, representing well the geomorphological environments of karst terrains where depressions are singular elements with dimensions varying from one meter to kilometers, which are of intrinsic interest. In this work, we applied a methodology to detect, classify and analyze the depressions based on data from the Advanced Land-observing Satellite (ALOS) phased-array L-type synthetic-aperture radar (PALSAR) digital elevation model (DEM) with a spatial resolution of 12.5 m. The delineated depressions were validated with depressions digitized from topographic maps, while to filter out spurious depressions, morphometric parameters characteristics were used. The resulted corrected depressions, were classified by the k-means algorithm into doline, uvalas type A, and uvalas type B. Beside morphometric parameters, circularity, eccentricity, depth, volume and major axes orientations of the three depressions types, the spatial distribution of the depressions was analyzed using a series of spatial parameters such as depressions density and Depressions relief. A correlation analysis between area and depth show that high uvalas A and uvalas B depth related to big depressions area, also uvalas A and uvalas B orientations are very similar to the geological faults ones, which conform in general to tectonic directions and the general aspect of mount Lebanon plateaus.
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Absence of reliable hydro-climatic information is among the bottlenecks for inadequate and improper management of stormwater runoff in rapidly-urbanizing catchments. This paper explores the influence of catchment heterogeneity in understanding the proneness of urban catchments to stormwater-borne hazards. Using GIS techniques, satellite images, and field surveys, geomorphological features and hydrologic characteristics of the Mbezi River catchment in Dar es Salaam-Tanzania were modeled to understand variations in their influence on flood hazards occurrence throughout the study catchment. The findings reveal that with GIS techniques public, domain Digital Elevation Models (DEMs) can provide preliminary but useful insights to inform stormwater management decisions in cities with limited hydrological data. Specifically, the heterogeneity characterization of the case study catchment indicates that Mbezi River is fern-leaf-shaped: it has a well-drained catchment (drainage density = 1.9 km/km2), with total relief and elongation ratios of 265 m and 0.25, respectively. Results further revealed that the catchment is comprised of many natural sinks (blue spots) that, upon enhancement, can retain about 18 percent of stormwater runoff that could otherwise contribute to downstream runoff challenges. About 68 percent of the major sinks (with potential volume > 2.4 m3) are located along the river flood plain where land is publicly owned. Additionally, more than 11.6 ha of land (as property) and 168 buildings are in areas that were mapped to have large natural sinks and they are at risk to flooding when the sinks get filled.
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The Remote Sensing and Geographic Information System - GIS are tools that assist in the planning, use and human occupation of sensitive areas like karst terrain. The region between the Guapiara Plateau and Paranapiacaba Range, south of the state of São Paulo presents this geological context that are under constant pressure of the anthropic advancement of several kind of natures, such as mining of carbonate rocks, forestry, agriculture and human occupation itself, inputting a risk to both human lives and preservation of karst systems. The preparation of the map of use and land cover of the area of study is one of the necessary databases themes to be used for land use planning. This work presents the association of remote sensing techniques and the use of GIS information analysis of the use and land cover during the years 2001, 2010 and 2014, through images Landsat 7. Thus, it was possible to map the main land uses in the area, highlighting a wide variability particularly in the Guapiara Plateau. The results demonstrate the advantages of the use of geotechnology in identifying environmental areas of high sensitivity and the possibility of regional planning or establishment of growth vectors towards areas of lower environmental impact.
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Oil palm cultivation in Ecuador is important for the agricultural sector. As a result of it, the country generates sources of employment in some of the most vulnerable zones; it contributes 0.89% of the gross domestic product and 4.35% of the agricultural gross domestic product. In 2017, a value of USD $252 million was generated by exports, and palm contributed 4.53% of the agricultural gross domestic product (GDP). It is estimated that 125,000 hectares of palm were lost in the Republic of Ecuador due to Red Ring Disease (RRD) and specifically Bud Rot (BR). The current study aimed to generate an early detection of BR and RRD in oil palm. Image acquisition has been performed using Remotely Piloted Aircraft System (RPAS) with Red, Green, and Blue (RGB) cannons, and multispectral cameras, in study areas with and without the presence of the given disease. Hereby, we proposed two phases. In phase A, a drone flight has been conducted for processing and georeferencing. This allowed to obtain an orthomosaic that serves as input for obtaining several vegetation indices of the healthy crop. The data and products obtained from this phase served as a baseline to perform comparisons with plantations affected by BR and RRD and to differentiate the palm varieties that are used by palm growers. In phase B, the same process has been applied three times with an interval of 15 days in an affected plot, in order to identify the symptoms and the progress of them. A validation for the diseases detection has been performed in the field, by taking Global Positioning System (GPS) points of the palms that presented symptoms of BR and RRD, through direct observation by field experts. The inputs obtained in each monitoring allowed to analyze the spatial behavior of the diseases. The values of the vegetation indices obtained from Phase A and B aimed to establish the differences between healthy and diseased palms, with the purpose of generating the baseline of early responses of BR and RRD conditions. However, the best vegetation index to detect the BR was the Visible Atmospherically Resistant Index (VARI).
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Evaporite rocks, mainly gypsum (or anhydrite) and salt (halite), are the most soluble of common rocks. Their dissolution produces caves, sinkholes, disappearing streams, collapse structures, breccia pipes, and other karst features that are also commonly associated with carbonate rocks (limestones and dolomites). Evaporites underlie a vast region of southwestern United States that is herein named the Greater Permian Evaporite Basin (GPEB), and both natural and human-induced evaporite karst (EK) features are present in much of the region. This evaporite basin extends far beyond the traditional Permian Basin of west Texas and southeast New Mexico, and embraces about 650,000 km2 in parts of Texas, New Mexico, Oklahoma, Kansas, and Colorado. Eight major evaporite sequences are present in Permian rocks in the GPEB, including: 1) Wellington/Hutchinson, 2) Lower Cimarron/Lower Clear Fork, 3) Upper Cimarron/Upper Clear Fork, 4) San Andres/Flowerpot/Blaine/Yelton, 5) Artesia, 6) Castile, 7) Salado, and 8) Rustler Formations or Groups. EK results from both natural processes and human activities. Natural EK occurs when precipitation or ground water circulates through, and dissolves, part or all of an evaporite deposit. Human activities that can produce EK include: 1) construction upon, or directing water into or above, outcropping or shallow evaporites; and 2) drilling boreholes, opening mines, or other excavations into subsurface evaporites, mainly salt deposits, followed by unsaturated water coming in contact with, and dissolving, the evaporite. The principal difference between karst in evaporite rocks and in carbonates is that EK features can form rapidly, in a matter of days, weeks, or years, whereas carbonate-karst features typically take years, decades, or centuries to form. Rapid development of EK can lead to engineering or environmental problems, including damage to, and/or collapse of, homes, buildings, civil projects (such as dams, bridges, and highways), and farmlands; and it can also result in injury or loss of life.
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According to investigation, the isolated metal particles with special dimension could trigger Localized Surface Plasmon Resonance (LSPR) effect, which would significantly promote the solar modulation ability of VO2 thermochromic films. Nevertheless, there are few research reports about these kinds of structure and derived LSPR effect in VO2 films fabricated by physical vapor deposition. In this work, we employed acid etching approach to modify the surface morphology of sputtered VO2 films, and successfully prepared karst landform-like VO2 films. Besides, LSPR effect was acquired through controllable etching process, which induced excellent optical performance of luminous transmittance (Tlum-L = 61.3%) and solar modulation ability (ΔTsol = 11.9%). Inspired by karst landform, the etching mechanism was speculated, and ideal models based on Maxwell-Garnett theory were proposed for optimal optical performance in nanothermochromics. This kind of facile method may provide a universal idea to modify the surface structure of sputtered films.
Article
Free share link https://authors.elsevier.com/a/1ah6T7qzSr6M8 The past two decades have been prolific in production of global or near-global Digital Elevation Models (DEMs) derived from satellite data. The most recent addition to the family of global DEMs is the TanDEM-X DEM with resolution of 0.4 arc sec. DEMs are essential for a wide range of environmental applications, many of which are related to mountains including studies on natural hazards, forestry or glacier mass changes. However, synthetic aperture radar interferometry used for acquisition of TanDEM-X DEM is especially challenging over steep and irregular mountain surfaces due to shadowing and foreshortening effects. In this study, we assessed the absolute vertical accuracy of TanDEM-X DEM in European mountains. We compared it with both a Digital Terrain Model (DTM) and a Digital Surface Model (DSM) derived from airborne laser scanning data. Our results indicate that the height error of TanDEM-X DEM expressed as absolute deviation at the 90% quantile is consistent with the 10m mission specification benchmark. We further concentrated on the absolute height error with respect to environmental characteristics (i.e. forested and non-forested areas, slope, and aspect). The comparison of TanDEM-X DEM with a reference DTM showed a positive vertical offset; however, the mean error differed greatly between forested and non-forested areas. When compared to reference DSM, our results showed a slight underestimation. We observed the highest underestimation in deciduous forests, followed by coniferous forests and non-forested areas. A significant decrease in accuracy was observed with increasing slope, especially for slopes above 10°. In mountains where the imagery was acquired only in one orbit direction (i.e. ascending for Northern hemisphere), the largest TanDEM-X DEM error when compared to DSM was recorded for the westfacing slopes (i.e. slopes facing the sensor); however, the association with terrain orientation diminished in mountains, the imagery of which was acquired from both the ascending and descending orbit. Finally, we evaluated the effect of data acquisition characteristics provided with TanDEM-X DEM as auxiliary data. Our results show that two coverages might not be sufficient in mountain environment. Additional acquisitions, especially those with different acquisition geometry, improved the absolute vertical accuracy of TanDEM-X DEM and eliminated areas of inconsistency. We discourage from using the Height Error Map (HEM) to estimate the error magnitude. On the other hand, auxiliary data (COM, COV) provide valuable information that should be always used in pre-analyses to identify possible problematic areas.
Conference Paper
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Remote Sensing and Geographical Information Systems (RS and GIS) technology play a major role in thematic map generation and integrated analysis for mapping, managing and monitoring the natural resources. RS and GIS technology have opened a new era in the field of applied geology. A remote sensing observation from space provides a synoptic view of terrain, thus provide ability in detecting lithology, landform and lineaments on the imagery. Remotely sensed satellite data have a benefit that is, the image data can be enhanced/manipulated for improving image interpretability with better accuracy. GIS has the capability to visualize, enhance, manipulate, generate, store, integrate and analyze the thematic data. This study aims to map the geomorphological features in the Janjhavathi river basin based on visual image interpretation techniques. These maps would be useful for further analysis for natural resource planning, management, and decision making.
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Such a diverse and sensitive eco-region as Karst needs to be managed with special attention and consideration of its natural and cultural resources. Land cover is an important indicator, which enables the analysis of their condition and development monitoring. Advanced satellite images classification represents an accurate and cost-effective alternative to the classical techniques of land cover mapping. The methods used to produce a reliable land cover map are presented in this paper. The complexity of the area requires a combination of various data such as Landsat satellite images, digital elevation model, digital orthophotos as well as existing topographic and thematic maps. The maximum likelihood algorithm was used as the main classifier and the accuracy of results was further improved by fuzzy classification, altitude and inclination filtering and auxiliary data integration.
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The limestone high moutains of the Crète island, and their margins present remarkable patterns and formations brought up during neotectonic and bioclimatic controls very active on erosion agents. Many old landscapes have been shaped again (tropical karst to nivo karst ...). Even monogenic landscapes exist : gorges, detritic fans ... For the first time also a tropical glacial relief is described at this latitude in the south of the mediterranean regions.
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Karst is a characteristic geological feature of areas comprised of limestone. Due to the solubility of these rocks in water, exhibit an extreme heterogeneity of hydraulic conductivities. The characterizing features of karst aquifers are the open conduits, which provide low resistance pathways for ground water flow. Overall cave orientation is largely controlled by hydraulic gradient, joint patterns and other tectonic features, such as faulting and folding. The karst depressions may form on the surface by subsurface actions (dissolution and collapse). Thus, the depressions often show regularity of pattern or alignments, frequently in association with structurally guided cave systems below. The present work aims at to detect depressions zone, as dolines and uvalas in the limestone of the Bambui Group (Central Brazil) using ASTER and ASTERDEM images. A photogeological study, carried out on aster image allowed us to elaborate geomorphological map of dolines. Some guidance to detect dolines can be associated with fracture permeability dominated by nearly vertical joints and joint swarm is provided by fracture trace mapping from remote sensing. Commonly, dolines can be identified on the image and DEM as topographic depressions, which very often contain water or moist vegetation. The methodology allowed determining a doline distribution pattern what is important to environmental planning.
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GIS analysis‐based drainage basin delineation has become an attractive alternative to traditional manual delineation methods since the availability and accuracy of Digital Elevation Models (DEMs) and topographic databases has been improved. To investigate the uncertainty in the automatic delineation process, the present study represents a process‐convolution‐based Monte Carlo simulation tool that offers a powerful framework for investigating DEM error propagation with thousands of GIS‐analysis repetitions. Monte Carlo‐based probable drainage basin delineations and manual delineations performed by five experts in hydrology or physical geography were also compared. The results showed that automatic drainage basin delineation is very sensitive to DEM uncertainty. The model of this uncertainty can be used to find out the lower bound for the size of drainage basins that can be delineated with sufficient accuracy.
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Based on this application, it is possible to say that changing climatic and tectonic conditions from Miocene to Pliocene have affected to the course of karstification. Slope and elevation maps extracted from DEM have been compared with macro karstic features in GIS environment. Macro karst features have mostly developed between 0–40° and in areas where slope is greater than 40° a clear macro karst hasn't become. Tectono-karstic depressions and uvalas have formed between 0–1,000 m, doline type karstic depressions have developed between 1,000–1,500 m and an evident macro karst form hasn't become at elevations higher than 1,500 m. Shaded relief image of the area originated from DEM has designated that the area has a rough relief being created by neotectonic movements. This uneven area dissected by rivers is a suitable environment for karstic process. According to the agents functioning on karstification, it has been described that Menteşe Region has a "structure-erosion-corrosion karst" type. German Das Menteşe Gebiet, das sich vom Bafa See bis zur Gökova Bucht erstreckt, wurde mit digitalisierten topographischen und geologischen Karten und Satellitendaten analysiert. Große Karstformen (Dolinen, Uvalas, tektonisch bedingte Karsthohlformen und Trockentäler) sowie Kleinformen sind in dolomitischen und feuersteinhaltigen Kalken (Perm–Pliozän) entwickelt. Tektonische NE-SE und NE-SW verlaufende Linien, die aus geologischen Karten und Satellitenbildern ermittelt wurden, haben einen großen Einfluss auf die Formenentwicklung. In Anlehnung an das TIN Netz (Triangulated Irregular Network) und die geomorphologische Karte der Türkei wurden drei Reliefgenerationszyklen bestimmt. Diese Grundlagen erlauben die Aussage, dass die Veränderungen der klimatischen und tektonischen Bedingungen vom Miozän zum Pliozän den Verlauf der Verkarstung beeinflusst haben. Aus dem digitalen Geländemodell entwickelte Hang- und Höhenkarten zeigten im Vergleich mit den Karstformen, dass sich die Makrokarstformen überwiegend in Gebieten mit Hangneigungen zwischen 0–40° entwickelten, während klare Makrokarstformen bei Hangneigungen über 40° fehlten. Tektonisch bedingte Karsthohlformen und Uvalas bestimmen den Formenschatz der Höhenlage zwischen 0 und 1,000 m, von 1,000 bis 1,500 m Höhe sind Dolinen dominant und oberhalb 1,500 m fehlen augenscheinlich große Karstformen. Schattierte Darstellungen aus dem digitalen Geländemodell zeigen ein schroffes Relief, das auf die neotektonischen Bewegungen zurückgeht. Das durch Flüsse gegliederte Menteşe Gebiet bietet günstige Faktoren für Verkarstungsvorgänge und wird nach den die Verkarstung bestimmenden Elementen als ein von Struktur, Erosion und Korrosion geprägter Karsttyp eingestuft. French Dans cette recherche, karstification dans Menteşe Région de sud-ouest de Turquie a été étudiée par les applications de GIS et télédétection. Les caractéristiques de karstic de macro (doline, uvala, la dépression de tectono-karstic et la vallée de fluvio-karstic) du domaine s'étendant de Bafa de Lac à la Baie de Gökova a été fait la carte d'avec la géologie digitalisée et les cartes de topographie et l'image de satellite. Micro et karstification de macro a développé dans les calcaire de dolomitic et cherty étant au Dogger-Createcous, le Campanian-Maestrihtien, Senonian, le Jurassique-Createcous, le Triassic-Liassic de Milieu, Permian et les calcaire terrestres de Pliocene. Les lignes de luxation (le défaut-trait) dans la direction de nord-ouest-sud-est et de nord-est-sud-ouest extrait des cartes de géologie et de l'image de satellite sont des agents importants dans l'évaluation de formes de karstic de macro. Les cycles de génération de soulagement à trois niveaux ont été définis selon la surface d'ETAIN (Triangulated le Réseau Irrégulier) et la carte de géomorphologie de Turquie. Basé sur cette application, c'est possible de dire que cela changeant climatique et les conditions de tectonic de Miocene à Pliocene ont affecté au cours de karstification. Les cartes de pente et élévation extraites de DEM comparé aux caractéristiques de karstic de macro dans l'environnement de GIS. Les caractéristiques de karst de macro ont développé surtout entre 0–40° et dans les domaines où la pente est plus grande que 40° un macro karst hasn clair't est devenu. Les dépressions de Tectono-karstic et uvalas ont formé entre 0–1.000 m, les dépressions de karstic de type de doline ont développé entre 1.000–1.500 m et un hasn de forme de karst de macro évident't est devenu aux élévations plus hautes que 1.500 m. L'image ombragée de soulagement du domaine provenu de DEM a désigné que le domaine a un soulagement rude étant créé par les mouvements de neotectonic. Ce domaine inégal disséqué par les rivières est un environnement convenable pour le procédé de karstic. Selon les agents fonctionnant sur karstification, il a été décrit que Menteşe Région a un «structure-erosion-corrosion karst» le type.
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