Daniel Hoelbling | University of Salzburg (original) (raw)

Papers by Daniel Hoelbling

Global and Planetary Change, Sep 1, 2023

Science of The Total Environment, Oct 1, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Lava flows can threaten populated areas, cause casualties and considerable economic damage. There... more Lava flows can threaten populated areas, cause casualties and considerable economic damage. Therefore, understanding lava flows and their evolution is important because they can be linked to lava transport systems and eruption parameters. However, timely and accurate lava flow mapping in the field can be time-consuming and dangerous. Earth observation (EO) data plays an important role in improving lava flow mapping and monitoring. Synthetic Aperture Radar (SAR) data provide a unique opportunity to study lava flows, especially in areas with high cloud coverage during the year. Moreover, smoke and ash clouds can be partially penetrated by SAR. The freely available Sentinel-1 SAR data (C-band), with its high temporal and spatial resolution, opens new opportunities for studying lava flow evolution and lava morphology. However, Sentinel-1 data have mainly been used to study surface deformation using Differential Interferometric SAR (DInSAR) techniques, and the utilisation of SAR backscatter information for lava flow characterisation has not been thoroughly exploited. The Fagradalsfjall volcanic system is located on the Reykjanes Peninsula in southwest Iceland. The eruption began on the 19th of March and lasted until the 18th of September 2021. The resulting lava flows cover an area of 4.8 km2 (Pedersen et al., 2022). Another eruption occurred in August 2022. We used time series of dual-polarisation, including VH (antenna sends vertical pulses and receives horizontal backscatter) and VV (antenna sends vertical pulses and receives horizontal backscatter), Sentinel-1 data to study the changes in lava flow extent and morphology during the 2021 and 2022 Fagradalsfjall eruption phases. The pre-processing of Sentinel-1 data included orbit state vector correction, radiometric calibration to reduce the radiometric biases caused by topographic variations, co-registration, and range doppler terrain correction. In addition to backscatter polarisations, we calculated the image texture using the grey-level co-occurrence matrix (GLCM) algorithm, including several measures such as contrast, homogeneity, and entropy. We used object-based segmentation and classification algorithms to delineate the lava extent and evaluated the applicability of different polarisations. To validate the mapping results, we used reference layers derived from high-resolution optical images available from Pedersen et al. (2022). The results showed that cross-polarisation was the most suitable for mapping the extent of lava. Additionally, the integration of texture information allowed us to distinguish lava types to some extent. The results demonstrate the potential and challenges of utilising SAR backscatter information from Sentinel-1 data for studying the spatio-temporal lava flow evolution and mapping lava flow morphology, especially when the applicability of optical EO data is limited. Pedersen, G. B. M., Belart, J. M. C., Óskarsson, B. V., Gudmundsson, M. T., Gies, N., Högnadóttir, T., et al. (2022). Volume, Effusion Rate, and Lava Transport During the 2021 Fagradalsfjall Eruption: Results From Near Real-Time Photogrammetric Monitoring. Geophysical Research Letters, 49, 13, e2021GL097125. https://doi.org/10.1029/2021GL097125

Abstracts of the ICA, Jul 15, 2019

Landslide erosion is a serious land management problem in many parts of the world. In New Zealand... more Landslide erosion is a serious land management problem in many parts of the world. In New Zealand, a combination of steep erodible hill country, frequent and intense rainstorms, and recent forest clearance for pastoral farming has led to extensive landslide erosion in many parts of the country. Effective mitigation measures against landslide erosion and its consequences require a detailed understanding of the history, location, extent, and severity of landsliding. Consequently, the preparation and availability of comprehensive and meaningful landslide inventories and spatial representation using advanced cartographic techniques can support mitigation of landslide erosion, risk communication, decision making and land management.

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Sep 12, 2017

Landslide mapping benefits from the ever increasing availability of Earth Observation (EO) data r... more Landslide mapping benefits from the ever increasing availability of Earth Observation (EO) data resulting from programmes like the Copernicus Sentinel missions and improved infrastructure for data access. However, there arises the need for improved automated landslide information extraction processes from EO data while the dominant method is still manual delineation. Object-based image analysis (OBIA) provides the means for the fast and efficient extraction of landslide information. To prove its quality, automated results are often compared to manually delineated landslide maps. Although there is awareness of the uncertainties inherent in manual delineations, there is a lack of understanding how they affect the levels of agreement in a direct comparison of OBIA-derived landslide maps and manually derived landslide maps. In order to provide an improved reference, we present a fuzzy approach for the manual delineation of landslides on optical satellite images, thereby making the inherent uncertainties of the delineation explicit. The fuzzy manual delineation and the OBIA classification are compared by accuracy metrics accepted in the remote sensing community. We have tested this approach for high resolution (HR) satellite images of three large landslides in Austria and Italy. We were able to show that the deviation of the OBIA result from the manual delineation can mainly be attributed to the uncertainty inherent in the manual delineation process, a relevant issue for the design of validation processes for OBIA-derived landslide maps.

Shallow landslides are one of the most frequent mass movements in Brazil. Methods to study this k... more Shallow landslides are one of the most frequent mass movements in Brazil. Methods to study this kind of process and for construction of shallow landslide inventories are heterogeneous, since there are no standardized mapping guidelines in Brazil. The aim of this paper is to review the methodologies mostly used for shallow landslide inventories construction in Brazil based on articles published on this subject. The procedures adopted were: (I) searching publications about landslide inventory construction in Brazil within five scientific online databases (ScienceDirect, Periódicos CAPES, Google Scholar, Scopus, and Web of Science), (II) quantification and comparison of publications found on the databases, and (III) bibliometric analysis of the specific topic. The results indicate that only a small amount of publications is directly related to inventories of landslides. Visual interpretation is the most applied method and data used for inventory creation is diverse. The results confirm the hypothesis that landslide mapping in Brazil is very heterogenous and that there is a need for common mapping guidelines.

<p>Shallow landslide mapping is an important procedure for landslide assessment and is the ... more <p>Shallow landslide mapping is an important procedure for landslide assessment and is the first step to susceptibility, vulnerability, and risk analysis. Knowing the exact location of occurrence of this kind of natural hazard makes it possible to trace spatio-temporal patters and evaluate topographic influences. Landslides are very frequent along the Brazilian south and southeastern coast, where mass movements are triggered by heavy rainfall almost every year in the summer season (Dec-Mar), causing harm to society, such as the destruction of buildings, other infrastructure, and economic and human losses. Landslide recognition and mapping are poorly developed in Brazil, since no mapping guidelines exist, as well as due to low investments in mass movement prevention and mitigation actions. Thus, this research aimed to evaluate the use of freely accessible Google Earth Pro images for shallow landslides recognition and mapping. The study area is located in Ita&#243;ca and Apia&#237; counties, S&#227;o Paulo state, in Ribeira Valley region, Brazil. Ita&#243;ca and Apia&#237; were affected by mass movements in January 2014, resulting in several economic and infrastructure damages, and 25 fatalities. The most recent post-event images available in Google Earth Pro were used, dated as of 08/10/2014. The visual criteria for landslide scars recognition and mapping were the absence of vegetation, shape and size, drainage network distance, slope position, planar rupture surface, and altimetric variation. As a reference for manual mapping contour and hydrography curves of 1:10.000 scale from the Geographic and Cartographic Institute of the State of S&#227;o Paulo (for areas belonging to the municipality of Ita&#243;ca) and contour and hydrography curves of 1: 50.000 scale from the Brazilian Institute of Geography and Statistics (for the sectors belonging to the municipality of Apia&#237;) were used. The results showed that Google Earth Pro images are suitable for landslide recognition and mapping in a tropical environment. A total of 1,850 shallow landslides scars from the 2014 event with different sizes were mapped, where the smallest has 14 m&#178; and the largest 9,539 m&#178;. They occurred under different morphological and lithological conditions, where most landslides are concentrated at slopes between 20 and 30&#176;, south and southeast orientation, elevations of 600 to 800 m, concave curvatures, and in Quartz-Monzonite and Biotite Monzogranite rocks. The advantage of Google Earth images is that they are very high resolution data and free to access and use for everybody. However, the periods available on the software are limited. The event occurred in January of 2014 but it was only possible to access study area images of October of 2014, nine months after the event. In this way, it is important to verify if the mapping process is influenced by environmental changes, for example, vegetation recovery, that may cause interference for the visual interpretation. The inventory can be used as a basis for further analysis, such as for creating susceptibility and hotspot maps. Such products help to better understand shallow landslide dynamics in the study area, allowing comparison with other environments, and can support spatial planning and decision making of government authorities.</p>

The EGU General Assembly, Apr 23, 2017

Perennial landslide dams interrupt the sediment connectivity of rivers. Although most landslide d... more Perennial landslide dams interrupt the sediment connectivity of rivers. Although most landslide dams do not persist for more than a few days, those that do can exhibit significant sediment trapping capacity. While water can pass through or over the dam, the sediment load is trapped upstream of the dam until the dam breaks or gradually erodes, or is completely filled with deposits. The volume of sediment stored in this way can reach up to three times the volume of impounded water, as we find by back-analyzing the lake Hintersee in southeastern Germany. In this work, we reconstruct the pre-landslide topography using Petrel and then use the Gerris shallow-water flow solver with a Voellmy rheology to back-analyze this landslide-dammed lake in the Bavarian Alps. We test several landslide release scenarios and different landslide rheologies to obtain the best-fitting reconstruction of the dam topography. We then fill the landslide dam with water and sediment using simple slope algorithms and validate the results against the current topography. Finally, we compare the landslide deposit thicknesses, water depths, and trapped sediment thicknesses of our different scenarios in order to provide new insight into the damming and sediment trapping capacity of landslides.

AGIT Journal Angew. Geoinformatik, 2018

Zusammenfassung: Durch das Städtewachstum gehen vielfach öffentliche und private Grünräume verlor... more Zusammenfassung: Durch das Städtewachstum gehen vielfach öffentliche und private Grünräume verloren. Grünräume bieten Vorteile für Stadtklima und-ökologie und haben einen Mehrwert für die Freizeitgestaltung der Bevölkerung. Dem Erhalt bestehender und der Schaffung neuer Grün-und Freiflächen kommt in der Stadtplanung eine hohe Bedeutung zu. Das Forschungsprojekt "grünOase" entwickelte ein Konzept zur Bewertung von städtischen Grünräumen, das am Beispiel von zwei Parkanlagen in der Stadt Salzburg (dem Lehener Park und dem Preuschen Park) getestet wurde.

Permafrost and Periglacial Processes, Oct 9, 2022

International Journal of Disaster Risk Reduction

Global and Planetary Change, Sep 1, 2023

Science of The Total Environment, Oct 1, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Lava flows can threaten populated areas, cause casualties and considerable economic damage. There... more Lava flows can threaten populated areas, cause casualties and considerable economic damage. Therefore, understanding lava flows and their evolution is important because they can be linked to lava transport systems and eruption parameters. However, timely and accurate lava flow mapping in the field can be time-consuming and dangerous. Earth observation (EO) data plays an important role in improving lava flow mapping and monitoring. Synthetic Aperture Radar (SAR) data provide a unique opportunity to study lava flows, especially in areas with high cloud coverage during the year. Moreover, smoke and ash clouds can be partially penetrated by SAR. The freely available Sentinel-1 SAR data (C-band), with its high temporal and spatial resolution, opens new opportunities for studying lava flow evolution and lava morphology. However, Sentinel-1 data have mainly been used to study surface deformation using Differential Interferometric SAR (DInSAR) techniques, and the utilisation of SAR backscatter information for lava flow characterisation has not been thoroughly exploited. The Fagradalsfjall volcanic system is located on the Reykjanes Peninsula in southwest Iceland. The eruption began on the 19th of March and lasted until the 18th of September 2021. The resulting lava flows cover an area of 4.8 km2 (Pedersen et al., 2022). Another eruption occurred in August 2022. We used time series of dual-polarisation, including VH (antenna sends vertical pulses and receives horizontal backscatter) and VV (antenna sends vertical pulses and receives horizontal backscatter), Sentinel-1 data to study the changes in lava flow extent and morphology during the 2021 and 2022 Fagradalsfjall eruption phases. The pre-processing of Sentinel-1 data included orbit state vector correction, radiometric calibration to reduce the radiometric biases caused by topographic variations, co-registration, and range doppler terrain correction. In addition to backscatter polarisations, we calculated the image texture using the grey-level co-occurrence matrix (GLCM) algorithm, including several measures such as contrast, homogeneity, and entropy. We used object-based segmentation and classification algorithms to delineate the lava extent and evaluated the applicability of different polarisations. To validate the mapping results, we used reference layers derived from high-resolution optical images available from Pedersen et al. (2022). The results showed that cross-polarisation was the most suitable for mapping the extent of lava. Additionally, the integration of texture information allowed us to distinguish lava types to some extent. The results demonstrate the potential and challenges of utilising SAR backscatter information from Sentinel-1 data for studying the spatio-temporal lava flow evolution and mapping lava flow morphology, especially when the applicability of optical EO data is limited. Pedersen, G. B. M., Belart, J. M. C., Óskarsson, B. V., Gudmundsson, M. T., Gies, N., Högnadóttir, T., et al. (2022). Volume, Effusion Rate, and Lava Transport During the 2021 Fagradalsfjall Eruption: Results From Near Real-Time Photogrammetric Monitoring. Geophysical Research Letters, 49, 13, e2021GL097125. https://doi.org/10.1029/2021GL097125

Abstracts of the ICA, Jul 15, 2019

Landslide erosion is a serious land management problem in many parts of the world. In New Zealand... more Landslide erosion is a serious land management problem in many parts of the world. In New Zealand, a combination of steep erodible hill country, frequent and intense rainstorms, and recent forest clearance for pastoral farming has led to extensive landslide erosion in many parts of the country. Effective mitigation measures against landslide erosion and its consequences require a detailed understanding of the history, location, extent, and severity of landsliding. Consequently, the preparation and availability of comprehensive and meaningful landslide inventories and spatial representation using advanced cartographic techniques can support mitigation of landslide erosion, risk communication, decision making and land management.

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Sep 12, 2017

Landslide mapping benefits from the ever increasing availability of Earth Observation (EO) data r... more Landslide mapping benefits from the ever increasing availability of Earth Observation (EO) data resulting from programmes like the Copernicus Sentinel missions and improved infrastructure for data access. However, there arises the need for improved automated landslide information extraction processes from EO data while the dominant method is still manual delineation. Object-based image analysis (OBIA) provides the means for the fast and efficient extraction of landslide information. To prove its quality, automated results are often compared to manually delineated landslide maps. Although there is awareness of the uncertainties inherent in manual delineations, there is a lack of understanding how they affect the levels of agreement in a direct comparison of OBIA-derived landslide maps and manually derived landslide maps. In order to provide an improved reference, we present a fuzzy approach for the manual delineation of landslides on optical satellite images, thereby making the inherent uncertainties of the delineation explicit. The fuzzy manual delineation and the OBIA classification are compared by accuracy metrics accepted in the remote sensing community. We have tested this approach for high resolution (HR) satellite images of three large landslides in Austria and Italy. We were able to show that the deviation of the OBIA result from the manual delineation can mainly be attributed to the uncertainty inherent in the manual delineation process, a relevant issue for the design of validation processes for OBIA-derived landslide maps.

Shallow landslides are one of the most frequent mass movements in Brazil. Methods to study this k... more Shallow landslides are one of the most frequent mass movements in Brazil. Methods to study this kind of process and for construction of shallow landslide inventories are heterogeneous, since there are no standardized mapping guidelines in Brazil. The aim of this paper is to review the methodologies mostly used for shallow landslide inventories construction in Brazil based on articles published on this subject. The procedures adopted were: (I) searching publications about landslide inventory construction in Brazil within five scientific online databases (ScienceDirect, Periódicos CAPES, Google Scholar, Scopus, and Web of Science), (II) quantification and comparison of publications found on the databases, and (III) bibliometric analysis of the specific topic. The results indicate that only a small amount of publications is directly related to inventories of landslides. Visual interpretation is the most applied method and data used for inventory creation is diverse. The results confirm the hypothesis that landslide mapping in Brazil is very heterogenous and that there is a need for common mapping guidelines.

<p>Shallow landslide mapping is an important procedure for landslide assessment and is the ... more <p>Shallow landslide mapping is an important procedure for landslide assessment and is the first step to susceptibility, vulnerability, and risk analysis. Knowing the exact location of occurrence of this kind of natural hazard makes it possible to trace spatio-temporal patters and evaluate topographic influences. Landslides are very frequent along the Brazilian south and southeastern coast, where mass movements are triggered by heavy rainfall almost every year in the summer season (Dec-Mar), causing harm to society, such as the destruction of buildings, other infrastructure, and economic and human losses. Landslide recognition and mapping are poorly developed in Brazil, since no mapping guidelines exist, as well as due to low investments in mass movement prevention and mitigation actions. Thus, this research aimed to evaluate the use of freely accessible Google Earth Pro images for shallow landslides recognition and mapping. The study area is located in Ita&#243;ca and Apia&#237; counties, S&#227;o Paulo state, in Ribeira Valley region, Brazil. Ita&#243;ca and Apia&#237; were affected by mass movements in January 2014, resulting in several economic and infrastructure damages, and 25 fatalities. The most recent post-event images available in Google Earth Pro were used, dated as of 08/10/2014. The visual criteria for landslide scars recognition and mapping were the absence of vegetation, shape and size, drainage network distance, slope position, planar rupture surface, and altimetric variation. As a reference for manual mapping contour and hydrography curves of 1:10.000 scale from the Geographic and Cartographic Institute of the State of S&#227;o Paulo (for areas belonging to the municipality of Ita&#243;ca) and contour and hydrography curves of 1: 50.000 scale from the Brazilian Institute of Geography and Statistics (for the sectors belonging to the municipality of Apia&#237;) were used. The results showed that Google Earth Pro images are suitable for landslide recognition and mapping in a tropical environment. A total of 1,850 shallow landslides scars from the 2014 event with different sizes were mapped, where the smallest has 14 m&#178; and the largest 9,539 m&#178;. They occurred under different morphological and lithological conditions, where most landslides are concentrated at slopes between 20 and 30&#176;, south and southeast orientation, elevations of 600 to 800 m, concave curvatures, and in Quartz-Monzonite and Biotite Monzogranite rocks. The advantage of Google Earth images is that they are very high resolution data and free to access and use for everybody. However, the periods available on the software are limited. The event occurred in January of 2014 but it was only possible to access study area images of October of 2014, nine months after the event. In this way, it is important to verify if the mapping process is influenced by environmental changes, for example, vegetation recovery, that may cause interference for the visual interpretation. The inventory can be used as a basis for further analysis, such as for creating susceptibility and hotspot maps. Such products help to better understand shallow landslide dynamics in the study area, allowing comparison with other environments, and can support spatial planning and decision making of government authorities.</p>

The EGU General Assembly, Apr 23, 2017

Perennial landslide dams interrupt the sediment connectivity of rivers. Although most landslide d... more Perennial landslide dams interrupt the sediment connectivity of rivers. Although most landslide dams do not persist for more than a few days, those that do can exhibit significant sediment trapping capacity. While water can pass through or over the dam, the sediment load is trapped upstream of the dam until the dam breaks or gradually erodes, or is completely filled with deposits. The volume of sediment stored in this way can reach up to three times the volume of impounded water, as we find by back-analyzing the lake Hintersee in southeastern Germany. In this work, we reconstruct the pre-landslide topography using Petrel and then use the Gerris shallow-water flow solver with a Voellmy rheology to back-analyze this landslide-dammed lake in the Bavarian Alps. We test several landslide release scenarios and different landslide rheologies to obtain the best-fitting reconstruction of the dam topography. We then fill the landslide dam with water and sediment using simple slope algorithms and validate the results against the current topography. Finally, we compare the landslide deposit thicknesses, water depths, and trapped sediment thicknesses of our different scenarios in order to provide new insight into the damming and sediment trapping capacity of landslides.

AGIT Journal Angew. Geoinformatik, 2018

Zusammenfassung: Durch das Städtewachstum gehen vielfach öffentliche und private Grünräume verlor... more Zusammenfassung: Durch das Städtewachstum gehen vielfach öffentliche und private Grünräume verloren. Grünräume bieten Vorteile für Stadtklima und-ökologie und haben einen Mehrwert für die Freizeitgestaltung der Bevölkerung. Dem Erhalt bestehender und der Schaffung neuer Grün-und Freiflächen kommt in der Stadtplanung eine hohe Bedeutung zu. Das Forschungsprojekt "grünOase" entwickelte ein Konzept zur Bewertung von städtischen Grünräumen, das am Beispiel von zwei Parkanlagen in der Stadt Salzburg (dem Lehener Park und dem Preuschen Park) getestet wurde.

Permafrost and Periglacial Processes, Oct 9, 2022

International Journal of Disaster Risk Reduction