This article describes the setup and first results of a landslide monitoring system near the vill... more This article describes the setup and first results of a landslide monitoring system near the village of Malinao, municipality of St. Bernard on the Philippine Island of Leyte. The monitoring system combines wireless sensor network (WSN) technology with low-cost but precise micro sensors (MEMS). The system was developed in the framework of the joint project “SLEWS—A Sensor-based Landslide Early Warning System” that deals with the development of a prototype Alarm- and Early Warning System (EWS) for different types of landslides. The sensors integrated in the WSN are acceleration sensors, tilt sensors and barometric pressure sensors. The system was installed in November 2010 in a landslide prone area near the village of Malinao. For longer data transmission of about 15 km the SLEWS-System was combined with the already existing WLAN-based monitoring system for Flood Early Warning (FEWS) from the Deutsche Gesellschaft fur Internationale Zusammenarbeit (GIZ).
Flood related scientific and community-based data are rarely systematically collected and analyse... more Flood related scientific and community-based data are rarely systematically collected and analysed in the Philippines. Over the last decades the Pagsangaan River Basin, Leyte, has experienced several flood events. However, documentation describing flood characteristics such as extent, duration or height of these floods are close to non-existing. To address this issue, computerized flood modelling was used to reproduce past events where there was data available for at least partial calibration and validation. The model was also used to provide scenario-based predictions based on A1B climate change assumptions for the area. The most important input for flood modelling is a Digital Elevation Model (DEM) of the river basin. No accurate topographic maps or Light Detection And Ranging (LIDAR)-generated data are available for the Pagsangaan River. Therefore, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Map (GDEM), Version 1, was chosen...
Recent advances in early warning have been observed in science and technology as well as the over... more Recent advances in early warning have been observed in science and technology as well as the overall effectiveness of end-to-end early warning systems. The accuracy in predicting earthquakes is slowly increasing, but it is still far from being applicable to routine early warning systems. Tests of landslide warning systems based on motion sensors of slopes are progressing and might be used more widespread in the coming years. Fast communication is not a real issue for today’s technology, but spreading alert information quickly to large communities without access to modern communication equipment remains a problem. However, some experiences of locally anchored early warning systems point to higher effectiveness if they are managed decentralized within communities. Though EWS have to be adjusted to local circumstances the growing number of temporary visitors (e.g. migrants, tourists) in the world, require some type of international standard easily understood by everyone. While the wo...
Abstract. Total subsidence in deltaic areas is the cumulative effect of a range of driving mechan... more Abstract. Total subsidence in deltaic areas is the cumulative effect of a range of driving mechanisms, both natural and anthropogenic. The populous and low-lying Vietnamese Mekong delta is facing accelerating subsidence rates and effective mitigation strategies are urgently needed to save-guard the future sustainability of the delta. This paper gathers results from existing measurements and estimates of subsidence in the Mekong delta and presents new, delta-wide datasets of PSI observations of vertical velocity from 2014–2019. We describe the practical application of this new data in ongoing projects in Vietnam and outline a planned approach to determine depth-dependent subsidence rates, using this new dataset in combination with field surveys and physics-based numerical models, to advance towards improved quantitation of the contributions of individual subsidence mechanisms.
The Mekong delta, like many deltas around the world, is subsiding at a relatively high rate, pred... more The Mekong delta, like many deltas around the world, is subsiding at a relatively high rate, predominately due to natural compaction and groundwater overexploitation. Land subsidence influences many urbanized areas in the delta. Loading, differences in infrastructural foundation depths, land-use history, and subsurface heterogeneity cause a high spatial variability in subsidence rates. While overall subsidence of a city increases its exposure to flooding and reduces the ability to drain excess surface water, differential subsidence results in damage to buildings and above-ground and underground infrastructure. However, the exact contribution of different processes driving differential subsidence within cities in the Mekong delta has not been quantified yet. In this study we aim to identify and quantify drivers of processes causing differential subsidence within three major cities in the Vietnamese Mekong delta: Can Tho, Ca Mau and Long Xuyen. Satellite-based PS-InSAR (Persistent Sca...
<p&amp... more <p>Coastal subsidence increases the vulnerability to flooding risk, salinization of water resources and permanent inundation. For the Mekong Delta, whose mean elevation is less than 2 m above sea level, subsidence rates of up to several centimeters per year have been reported recently. This leads to a growing risk for the resident population, infrastructure and economy, increased by the accelerating sea level rise. Land subsidence in Mekong Delta has different causes, most prominently natural compaction of young deltaic sediments, but also overexploitation of groundwater aquifers with accompanying head decline. Precise monitoring of the subsidence rate is necessary for analyses of cause and hazard as well as planning and assessment of countermeasures. Here, we present and discuss recent land subsidence rates in the Mekong Delta derived from satellite-based SAR-Interferometry.</p><p>We use Sentinel-1 scenes acquired between 2015 and 2019 to analyze recent land subsidence in the lower Mekong Delta. The Persistent Scatterer Interferometry technique (PS-InSAR) is applied, which allows for the estimation of displacement rates of coherent backscatter targets with mm-accuracy. Separate analyses of time series from ascending and descending observations and comparison with other studies based on data of the same sensor give insight into the accuracy of the parameter estimation and the error budget.</p><p>The observed subsidence rates of up to 6 cm/yr feature mainly three different spatial characteristics: (i) interconnected areas of little to no subsidence, (ii) isolated urban hot-spots with high subsidence rates and (iii) larger regions with increased subsidence rates covering urban as well as rural areas. Points on deeply founded infrastructure frequently exhibit lower subsidence rates than adjacent ground surface points. We study this phenomenon at different buildings since subsidence rates with respect to different foundation depths can be used as a proxy to constrain the effective depths of sediment compaction. Further, the correlation of observed subsidence rates and spatial distribution of lithostratigraphic units from quaternary sedimentary depositions is investigated. Finally, we show changes and commons in the spatial distribution of the subsidence rates compared to a previously published study on subsidence in the Mekong Delta covering data from 2006 to 2010.</p>
Local Flood Early Warning Systems (LFEWS) in developing countries did not utilize satellite gener... more Local Flood Early Warning Systems (LFEWS) in developing countries did not utilize satellite generated geo information much in the past. The Binahaan River in Leyte, Philippines, inundates an area of 50sqkm in average more than once per year. This causes considerable damage to crops, some households and occasionally infrastructure. In the Binahaan river basin data from SPOT5 and other satellites
This article describes the setup and first results of a landslide monitoring system near the vill... more This article describes the setup and first results of a landslide monitoring system near the village of Malinao, municipality of St. Bernard on the Philippine Island of Leyte. The monitoring system combines wireless sensor network (WSN) technology with low-cost but precise micro sensors (MEMS). The system was developed in the framework of the joint project “SLEWS—A Sensor-based Landslide Early Warning System” that deals with the development of a prototype Alarm- and Early Warning System (EWS) for different types of landslides. The sensors integrated in the WSN are acceleration sensors, tilt sensors and barometric pressure sensors. The system was installed in November 2010 in a landslide prone area near the village of Malinao. For longer data transmission of about 15 km the SLEWS-System was combined with the already existing WLAN-based monitoring system for Flood Early Warning (FEWS) from the Deutsche Gesellschaft fur Internationale Zusammenarbeit (GIZ).
Flood related scientific and community-based data are rarely systematically collected and analyse... more Flood related scientific and community-based data are rarely systematically collected and analysed in the Philippines. Over the last decades the Pagsangaan River Basin, Leyte, has experienced several flood events. However, documentation describing flood characteristics such as extent, duration or height of these floods are close to non-existing. To address this issue, computerized flood modelling was used to reproduce past events where there was data available for at least partial calibration and validation. The model was also used to provide scenario-based predictions based on A1B climate change assumptions for the area. The most important input for flood modelling is a Digital Elevation Model (DEM) of the river basin. No accurate topographic maps or Light Detection And Ranging (LIDAR)-generated data are available for the Pagsangaan River. Therefore, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Map (GDEM), Version 1, was chosen...
Recent advances in early warning have been observed in science and technology as well as the over... more Recent advances in early warning have been observed in science and technology as well as the overall effectiveness of end-to-end early warning systems. The accuracy in predicting earthquakes is slowly increasing, but it is still far from being applicable to routine early warning systems. Tests of landslide warning systems based on motion sensors of slopes are progressing and might be used more widespread in the coming years. Fast communication is not a real issue for today’s technology, but spreading alert information quickly to large communities without access to modern communication equipment remains a problem. However, some experiences of locally anchored early warning systems point to higher effectiveness if they are managed decentralized within communities. Though EWS have to be adjusted to local circumstances the growing number of temporary visitors (e.g. migrants, tourists) in the world, require some type of international standard easily understood by everyone. While the wo...
Abstract. Total subsidence in deltaic areas is the cumulative effect of a range of driving mechan... more Abstract. Total subsidence in deltaic areas is the cumulative effect of a range of driving mechanisms, both natural and anthropogenic. The populous and low-lying Vietnamese Mekong delta is facing accelerating subsidence rates and effective mitigation strategies are urgently needed to save-guard the future sustainability of the delta. This paper gathers results from existing measurements and estimates of subsidence in the Mekong delta and presents new, delta-wide datasets of PSI observations of vertical velocity from 2014–2019. We describe the practical application of this new data in ongoing projects in Vietnam and outline a planned approach to determine depth-dependent subsidence rates, using this new dataset in combination with field surveys and physics-based numerical models, to advance towards improved quantitation of the contributions of individual subsidence mechanisms.
The Mekong delta, like many deltas around the world, is subsiding at a relatively high rate, pred... more The Mekong delta, like many deltas around the world, is subsiding at a relatively high rate, predominately due to natural compaction and groundwater overexploitation. Land subsidence influences many urbanized areas in the delta. Loading, differences in infrastructural foundation depths, land-use history, and subsurface heterogeneity cause a high spatial variability in subsidence rates. While overall subsidence of a city increases its exposure to flooding and reduces the ability to drain excess surface water, differential subsidence results in damage to buildings and above-ground and underground infrastructure. However, the exact contribution of different processes driving differential subsidence within cities in the Mekong delta has not been quantified yet. In this study we aim to identify and quantify drivers of processes causing differential subsidence within three major cities in the Vietnamese Mekong delta: Can Tho, Ca Mau and Long Xuyen. Satellite-based PS-InSAR (Persistent Sca...
<p&amp... more <p>Coastal subsidence increases the vulnerability to flooding risk, salinization of water resources and permanent inundation. For the Mekong Delta, whose mean elevation is less than 2 m above sea level, subsidence rates of up to several centimeters per year have been reported recently. This leads to a growing risk for the resident population, infrastructure and economy, increased by the accelerating sea level rise. Land subsidence in Mekong Delta has different causes, most prominently natural compaction of young deltaic sediments, but also overexploitation of groundwater aquifers with accompanying head decline. Precise monitoring of the subsidence rate is necessary for analyses of cause and hazard as well as planning and assessment of countermeasures. Here, we present and discuss recent land subsidence rates in the Mekong Delta derived from satellite-based SAR-Interferometry.</p><p>We use Sentinel-1 scenes acquired between 2015 and 2019 to analyze recent land subsidence in the lower Mekong Delta. The Persistent Scatterer Interferometry technique (PS-InSAR) is applied, which allows for the estimation of displacement rates of coherent backscatter targets with mm-accuracy. Separate analyses of time series from ascending and descending observations and comparison with other studies based on data of the same sensor give insight into the accuracy of the parameter estimation and the error budget.</p><p>The observed subsidence rates of up to 6 cm/yr feature mainly three different spatial characteristics: (i) interconnected areas of little to no subsidence, (ii) isolated urban hot-spots with high subsidence rates and (iii) larger regions with increased subsidence rates covering urban as well as rural areas. Points on deeply founded infrastructure frequently exhibit lower subsidence rates than adjacent ground surface points. We study this phenomenon at different buildings since subsidence rates with respect to different foundation depths can be used as a proxy to constrain the effective depths of sediment compaction. Further, the correlation of observed subsidence rates and spatial distribution of lithostratigraphic units from quaternary sedimentary depositions is investigated. Finally, we show changes and commons in the spatial distribution of the subsidence rates compared to a previously published study on subsidence in the Mekong Delta covering data from 2006 to 2010.</p>
Local Flood Early Warning Systems (LFEWS) in developing countries did not utilize satellite gener... more Local Flood Early Warning Systems (LFEWS) in developing countries did not utilize satellite generated geo information much in the past. The Binahaan River in Leyte, Philippines, inundates an area of 50sqkm in average more than once per year. This causes considerable damage to crops, some households and occasionally infrastructure. In the Binahaan river basin data from SPOT5 and other satellites
Uploads
Papers by Olaf Neussner