Remote Sensing for Landslide Investigations: An Overview of Recent Achievements and Perspectives

Landslides represent major natural hazards, which cause every year significant loss of lives and damages to buildings, properties and lifelines. In the last decades, a significant increase in landslide frequency took place, in concomitance to climate change and the expansion of urbanized areas. Remote sensing techniques represent a powerful tool for landslide investigation: applications are traditionally divided into three main classes, although this subdivision has some limitations and borders are sometimes fuzzy. The first class comprehends techniques for landslide recognition, i.e., the mapping of past or active slope failures. The second regards landslide monitoring, which entails both ground deformation measurement and the analysis of any other changes along time (e.g., land use, vegetation cover). The third class groups methods for landslide hazard analysis and forecasting. The aim of this paper is to give an overview on the applications of remote-sensing techniques for the three categories of landslide investigations, focusing on the achievements of the last decade, being that previous studies have already been exhaustively reviewed in the existing literature. At the end of the paper, a new classification of remote-sensing techniques that may be pertinently adopted for investigating specific typologies of soil and rock slope failures is proposed

Application of Differential and Polarimetric Synthetic Aperture Radar (SAR) Interferometry for Studying Natural Hazards

In the following work, I address the problem of coherence loss in standard Differential Interferometric SAR (DInSAR) processing, which can result in incomplete or poor quality deformation measurements in some areas. I incorporate polarimetric information with DInSAR in a technique called Polarimetric SAR Interferometry (PolInSAR) in order to acquire more accurate and detailed maps of surface deformation. In Chapter 2, I present a standard DInSAR study of the Ahar double earthquakes (Mw=6.4 and 6.2) which occurred in northwest Iran, August 11, 2012. The DInSAR coseismic deformation map was affected by decorrelation noise. Despite this, I employed an advanced inversion technique, in combination with a Coulomb stress analysis, to find the geometry and the slip distribution on the ruptured fault plane. The analysis shows that the two earthquakes most likely occurred on a single fault, not on conjugate fault planes. This further implies that the minor strike-slip faults play more significant role in accommodating convergence stress accumulation in the northwest part of Iran. Chapter 3 presents results from the application of PolInSAR coherence optimization on quad-pol RADARSAT-2 images. The optimized solution results in the identification of a larger number of reliable measurement points, which otherwise are not recognized by the standard DInSAR technique. I further assess the quality of the optimized interferometric phase, which demonstrates an increased phase quality with respect to those phases recovered by applying standard DInSAR alone. Chapter 4 discusses results from the application of PolInSAR coherence optimization from different geometries to the study of creep on the Hayward fault and landslide motions near Berkeley, CA. The results show that the deformation rates resolved by PolInSAR are in agreement with those of standard DInSAR. I also infer that there is potential motion on a secondary fault, northeast and parallel to the Hayward fault, which may be creeping with a lower velocity

Improving Flood Detection and Monitoring through Remote Sensing

As climate-change- and human-induced floods inflict increasing costs upon the planet, both in terms of lives and environmental damage, flood monitoring tools derived from remote sensing platforms have undergone improvements in their performance and capabilities in terms of spectral, spatial and temporal extents and resolutions. Such improvements raise new challenges connected to data analysis and interpretation, in terms of, e.g., effectively discerning the presence of floodwaters in different land-cover types and environmental conditions or refining the accuracy of detection algorithms. In this sense, high expectations are placed on new methods that integrate information obtained from multiple techniques, platforms, sensors, bands and acquisition times. Moreover, the assessment of such techniques strongly benefits from collaboration with hydrological and/or hydraulic modeling of the evolution of flood events. The aim of this Special Issue is to provide an overview of recent advancements in the state of the art of flood monitoring methods and techniques derived from remotely sensed data

Assessment of Landscape Processes, Forms and Features in the Lake Manyara Region, East African Rift Valley

The rift valleys of the East African Rift Systems form two branches (Eastern and Western rift). Within the Eastern rift, there is a southward propagation in the onset of volcanism, and hence rifting that has led to the formation of a narrow graben commonly referred to as the Gregory rift (in Tanzania). The endorheic basin at its southern end where the present saline Lake Manyara was formed. The lakes largest tributary is the Makuyuni River that is providing fresh water from northwest volcanic highlands. Along the Makuyuni River, where first and second tributaries cut deep into the sediments, the landscape is dominated by erosion features. These sediments reveal exposed and outcropping artefacts and fossils, which have been found starting in the 1930s in archaeological and paleontological expeditions. In the close vicinity of Makuyuni town, two hominin bearing sites were discovered in 2008. As few is known about the landscape itself, this study has set its focus on the surrounding landscapes of Makuyuni and its geomorphic implications. Key drivers of landscape development in Northern Tanzania are the tectonics and tectonically induced processes. The thus disrupt drainage networks and analyses thereof can reveal the effects on the morphology of stream longitudinal profiles. These transformations in turn, have an impact on driving river incision, in general on linear erosion phenomena. The triggered rill and gully erosion features will eventually lead to soil loss. Gully erosion is a major threat concerning landscape degradation in semiarid ecosystems, as they remove fertile topsoil and as such prevent agricultural use. The study showed, that most of the gully systems are there for decades and in stable conditions. There are, however, areas of exposed risk for erosion. A detailed examination of soil loss areas, innovative automatic surface runoff detector (SRD) devices have been installed. They measure runoff height and duration. This data contribute to a better understanding of the water cycle as well as to soil functions in semiarid environments. The specific research questions have been considered in five different publications that describe the applied methodologies and results in detail. In order to understand the different geomorphic processes, different methods and scales have been used. Field surveying was an important factor and surface runoff, soil characteristics and erosion phenomena have been sampled and measured. Specifically, this study examined rill and gully erosion features and underwent a detailed mapping around Makuyuni in order to describe and understand the occurring landscape systems. Laboratory procedures involved soil parameter analysing and digital data analysis involved digital elevation model analysis, remote sensing imagery, sophisticated statistical models and in the end a detailed geomorphic map compiling of the greater area. Many studies have focused on partial aspects of geomorphic processes. The frame-work of this doctoral thesis seeks to answer a holistic approach, in order to understand, interpret and discuss related geomorphic processes, their spatial extents and locations. This work contributes to the knowledge of present geomorphic processes and features and the landscape evolution within the Lake Manyara area in Northern Tanzania. The above mentioned methods and analyses may be applicable to similar areas in the African rift.Der große Ostafrikanische Grabenbruch teilt sich im südlichen Äthiopien in zwei Hauptsysteme, den östlichen und den westlichen Graben. Im östlichen Graben nehmen die vulkanischen Aktivitäten und daher auch die aktive Grabenbildung nach Süden zu, was zu der heutigen Bildung einer engen Grabenschlucht geführt hat, das sogenannte Gregory Rift in Tansania. An dessen südlichem Ende hat sich ein endorheisches Becken gebildet, wo sich heute der flache Salzsee Manyara befindet. Sein größter Zubringer ist der Fluss Makuyuni, welcher Frischwasser aus den vulkanischen Hochlanden nordwestlich des Beckens mit sich führt. Entlang diesen Flusses haben sich weitere Verzweigungen tief in die Sedimente gegraben; die Landschaft wird von Erosionsformen dominiert. In diesen Sedimenten zeigen sich nun freigelegte Artefakte und Fossilien, welche seit den 1930er Jahren bei archäologischen wie paläontologischen Expeditionen entdeckt wurden. In der Nähe der Siedlung Makuyuni wurden 2008 zwei Knochenreste von frühen Hominiden gefunden. Wenig Forschung gibt es über die Landschaft selber, die vorliegende Arbeit beschäftigt sich daher mit der Umgebung Makuyunis und seinen geomorphologischen Eigenschaften. Wesentlich für die Formung der Landschaft Nordtansanias sind die tektonischen und tektonisch-getriebenen Prozesse. Die dadurch gestörten Abflussnetzwerke und deren Analysen können die Auswirkungen auf die Morphologie der Abflusslängsprofile aufzeigen. Diese Veränderungen wiederum wirken sich auf die Einschneidungsdynamiken der Flüsse und Bäche aus, generell also auf lineare Abflussprozesse. Die so entstehenden Rillen- und Gullyerosionsformen führen zu Bodenverlusten. Die Gullyerosion ist eine der größten Naturgefahren in semiariden Ökosystemen, da sie große Teile des Oberbodens abtragen und so die Landschaft einer agrarischen Nutzung entziehen. Die Arbeit konnte aufzeigen, dass viele der Gullysysteme seit mehreren Jahrzehnten bestehen und stabil sind. Es gibt jedoch Bereiche, die von potentiellen Abtragungsrisiken betroffen sind. Um diese Bodenabtragungen genauer zu untersuchen, wurde mit innovativen Oberflächenabflussdetektoren gearbeitet. Diese messen den Oberflächenabfluss in seiner Höhe und Dauer. Diese Daten tragen zu einem besseren Verständnis des Wasserkreislaufes sowie allgemein zu Bodenfunktionen semiarider Ökosysteme bei. Die jeweiligen Forschungsfragen wurden in fünf Artikeln abgehandelt, diese beschreiben die angewandten Methoden und Resultate im Detail. Um die verschiedenen geomorphologischen Prozesse zu untersuchen, wurde mit verschiedenen Methoden und verschiedenen Skalen gearbeitet. Die Feldarbeit nahm einen wichtigen Teil ein und es wurden u.a. Oberflächenabfluss, Bodenwerte und Erosionsformen beprobt und vermessen. Im Speziellen wurden auf die Rillen- und Gullyerosion eingegangen sowie auf eine detaillierte Kartierung der Umgebung Makuyunis um die verschiedenen Landschaftssysteme zu beschreiben und zu verstehen. Im Labor wurden die Bodenproben analysiert und mit den digitalen Geländemodellen, den Fernerkundungsdaten und statistischen Methoden wurden einzelne Studien durchgeführt und am Ende eine geomorphologische Karte des Gebiets erarbeitet. Viele Studien untersuchten Teilbereiche geomorphologischer Prozesse. Im Rahmen dieser Doktorarbeit wurde daher ein ganzheitlicher Ansatz verfolgt, um die geomorphologischen Prozesse, ihre räumliche Ausdehnung und Verortung zu verstehen, zu interpretieren und die wissenschaftlichen Erkenntnisse als Ganzes zu diskutieren. Diese Arbeit trägt daher zu neuem Wissen aktueller geomorphologischer Prozesse und Formen sowie der Landschaftsentwicklung als solche in der Umgebung des Manyarasees in Nordtansania bei. Die dabei verwandten Methoden und Analysen sind in ähnlichen Ökosystemen entlang des Ostafrikanischen Grabens anwendbar

Spatial variability of aircraft-measured surface energy fluxes in permafrost landscapes

Arctic ecosystems are undergoing a very rapid change due to global warming and their response to climate change has important implications for the global energy budget. Therefore, it is crucial to understand how energy fluxes in the Arctic will respond to any changes in climate related parameters. However, attribution of these responses is challenging because measured fluxes are the sum of multiple processes that respond differently to environmental factors. Here, we present the potential of environmental response functions for quantitatively linking energy flux observations over high latitude permafrost wetlands to environmental drivers in the flux footprints. We used the research aircraft POLAR 5 equipped with a turbulence probe and fast temperature and humidity sensors to measure turbulent energy fluxes along flight tracks across the Alaskan North Slope with the aim to extrapolate the airborne eddy covariance flux measurements from their specific footprint to the entire North Slope. After thorough data pre-processing, wavelet transforms are used to improve spatial discretization of flux observations in order to relate them to biophysically relevant surface properties in the flux footprint. Boosted regression trees are then employed to extract and quantify the functional relationships between the energy fluxes and environmental drivers. Finally, the resulting environmental response functions are used to extrapolate the sensible heat and water vapor exchange over spatio-temporally explicit grids of the Alaskan North Slope. Additionally, simulations from the Weather Research and Forecasting (WRF) model were used to explore the dynamics of the atmospheric boundary layer and to examine results of our extrapolation

Remote Sensing and Geosciences for Archaeology

This book collects more than 20 papers, written by renowned experts and scientists from across the globe, that showcase the state-of-the-art and forefront research in archaeological remote sensing and the use of geoscientific techniques to investigate archaeological records and cultural heritage. Very high resolution satellite images from optical and radar space-borne sensors, airborne multi-spectral images, ground penetrating radar, terrestrial laser scanning, 3D modelling, Geographyc Information Systems (GIS) are among the techniques used in the archaeological studies published in this book. The reader can learn how to use these instruments and sensors, also in combination, to investigate cultural landscapes, discover new sites, reconstruct paleo-landscapes, augment the knowledge of monuments, and assess the condition of heritage at risk. Case studies scattered across Europe, Asia and America are presented: from the World UNESCO World Heritage Site of Lines and Geoglyphs of Nasca and Palpa to heritage under threat in the Middle East and North Africa, from coastal heritage in the intertidal flats of the German North Sea to Early and Neolithic settlements in Thessaly. Beginners will learn robust research methodologies and take inspiration; mature scholars will for sure derive inputs for new research and applications

Cartography

The terrestrial space is the place of interaction of natural and social systems. The cartography is an essential tool to understand the complexity of these systems, their interaction and evolution. This brings the cartography to an important place in the modern world. The book presents several contributions at different areas and activities showing the importance of the cartography to the perception and organization of the territory. Learning with the past or understanding the present the use of cartography is presented as a way of looking to almost all themes of the knowledge