Multi-scale remote sensing observations of a palsa in degradation phase

<p>The Vissátvuopmi palsa complex (N 68°74′50′′, E 21°11′30”) is the largest coherent palsa complex in Sweden (ca 274 ha). Aerial photo-interpretation over an area covered by plateau palsas showed a 30% decline in lateral area -- from ca 70 to 49 ha -- that occurred between 1955 to 2016 (Olvmo et al., 2020). Within Vissátvuopmi, we have more closely studied two single palsas, one dome-shaped and one ridge-shaped, for changes in extent, height and vegetation composition. Manual interpretation of aerial photography between 1955 and 2016 show lateral degradation of 35% and 54% for the dome and ridge palsas, respectively. Since 2018 we have monitored the palsas using images from drones as well as analysis of Planet Dove and Sentinel-2 satellite imagery. Photogrammetry is used to produce orthophotos as well as digital surface models (DSMs) from the drone images, and compared to earlier LiDAR and aerial photo DSMs, to study lateral and vertical degradation.</p><p>The drone-generated DSMs from 2018, 2019 and 2020 show further lateral degradation of the two large palsas. In 2020 a rapid change in vegetation composition was seen on the dome-shaped palsa, where a 250 m<sup>2</sup> area of <em>Betula nana</em> and <em>Empetrum hermaphroditum</em> transitioned to lichen. This vegetation change could be seen in spectral data from both drone and satellite platforms. The future development of this palsa, monitored annually using both fine and medium spatial resolution data, will give insight into the timing and signs of the individual palsas in stages of degradation.</p>

Trees and Crops Arrangement in the Agroforestry System Based on Slope Units to Control Landslide Reactivation on Volcanic Foot Slopes in Java, Indonesia

Agroforestry, as the dominant land use at the volcanic foot slope in Java Island, is prone to landslide due to a combination of rough relief and thick soil layer. However, evaluations of specific vegetation patterns against landslide reactivation due to soil erosion, which relays on the existing slope units and geomorphological processes, are still limited. The research data were collected through aerial photo interpretation by delineating morphological units of old landslides, slope units, and the existing land use. This was followed by field surveys for two consecutive purposes, i.e., (1) verification of aerial photo interpretation and (2) identification and intensity assessment of existing geomorphological processes. The data were tabulated according to slope units, as a basis for tree and crop arrangement in controlling erosion and landslide, by considering economic, social, and ecological functions. The agroforestry would control the landslides reactivation if the tree and crop arrangement was based on the morphological units formed by the previous landslide. The slope units are classified into residual zones at the highest elevations with flat slopes, erosion zones with the steepest slope, and sedimentation zones at the lowest elevations with gentle slopes. Trees and crops at those three units of the former landslide have different functions in controlling processes of rill erosion, gully erosion, and soil creep.

H.T.U. Smith (1965) dune morphology and chronology in central and western Nebraska. The Journal of Geology 73(4): 557–578

Climatic geomorphologists, and eolian geomorphologists in particular, have always been interested in studying dunes to understand and construct past climatic conditions. Smith’s 1965 paper presents an excellent example of a reconnaissance piece of scientific work that set the foundation for (1) using aerial photo-interpretation to provide chronological information about dune fields; (2) the use of eolian processes and landforms as climate change indicators; and (3) extraterrestrial or planetary geomorphology. This article briefly describes Smith’s background, background on Nebraska Sand Hills, and the impact and legacy of Smith’s classic paper.

Geomorphological analysis of wetland distribution on various spatial scales

<p><strong>Abstract.</strong> This study introduces some case analyses of wetland distribution on various spatial scales, from nationwide to the area of a wetland group, with a focus on geomorphological feature. Then described the usefulness of GIS analysis in wetland research. The nationwide wetland distribution in Japan showed that wetland density was high at less than 200&amp;thinsp;m and around 1600&amp;ndash;2000&amp;thinsp;m. Wetlands in mountainous regions were concentrated in snowy Quaternary volcanic regions from the center to the northern part of Japan. This implied snow accumulation and topography of volcanic mountains are important for wetland formation. Secondly, we clarified that wetlands were mainly distributed on the gentle slope of original volcanic surfaces and in landslides in the Hachimantai volcanic groups, in the northern Japan, using 10-m grid DEM and aerial photo interpretation. With the higher-resolution data, it was clear that wetlands were arranged depending on the microtopography of landslides and volcanic surfaces and groundwater. Using data with resolution suitable for the target topographical size and combining the results of multiple spatial scales/resolutions, we can understand the origin of wetlands in more detail.</p>

Evaluating earthquake-related ground failure mapping by combined traditional and modern methods

<p><strong>Abstract.</strong> A wide range of ground failure such as earthquake faulting (surface rupture), landslides, and liquefaction occur after a large earthquake. In this study, in order to rapidly determine the distribution of failure over a wide area after an earthquake, we combined traditional methods such as aerial photo interpretation and modern methods such as unmanned aerial vehicle (UAV) or interferometric synthetic aperture radar (InSAR) techniques. Moreover, elevation variations obtained using DEMs and the structure from motion and multi-view stereo (SfM-MVS) technique were employed to understand local ground deformation factors, such as reclaimed valley deformation. Using ortho-mosaic images, surface fissures caused by the 2016 Kumamoto Earthquake in Japan were rapidly interpreted and mapped, which enabled early interpretation of the ground failure situation. Furthermore, surface displacement properties extracted from SAR interferograms allowed for more advanced earthquake fault detection; surface displacement associated with liquefaction was also identified from SAR interferograms. In addition, InSAR was used to detect reclaimed valley deformation. Comparing this with the reclaimed valley distribution map created by the SfM-MVS technique improved our understanding of this phenomenon. However, many of these techniques require large amounts of manpower and time and can be influenced by differences in analyst skill level. In future, the development of mechanically automated ground failure identification will improve earthquake disaster responses.</p>

From visual aerial photo interpretation and field soil survey to automated decoding and soil mapping by satellite imagery

Under consideration are the ways for the development and improvement of methods to compile soil maps in Russia as based upon the information on landforms and the earth surface obtained by different aerial and outer space devices. The ever increasing development of aviation, cosmonautics and modification of electronic engineering resulted in great changes taken place in the soil studies, thus affecting the quality and readability of soil maps. The ways for obtaining and decoding of the satellite imagery are described. The methods to study different characteristics of soil properties are considered as well. The automated methods of soil identification and mapping are realized now through the materials of remote sounding of the Earth’s surface.

Landform monitoring in active volcano by UAV and SfM-MVS technique

Nishinoshima volcano in Ogasawara Islands has erupted since November, 2013. This volcanic eruption formed and enlarged a new island, and fused the new island with the old Nishinoshima Island. We performed automated aerial photographing using an Unmanned Aerial Vehicle (UAV) over the joined Nishinoshima Island on March 22 and July 4, 2014. We produced ortho-mosaic photos and digital elevation model (DEM) data by new photogrammetry software with computer vision technique, i.e. Structure from Motion (SfM) for estimating the photographic position of the camera and Multi-view Stereo (MVS) for generating the 3-D model. We also estimated the area and volume of the new island via analysis of ortho-mosaic photo and DEM data. Transition of volume estimated from the UAV photographing and other photographing shows the volcanic activity still keeps from initial level. The ortho-mosaic photos and DEM data were utilized to create an aerial photo interpretation map and a 3-D map. These operations revealed new knowledge and problems to be solved on the photographing and analysis using UAV and new techniques as this was first case in some respects.