Search

Sediment transported from debris‐flow initiation zones is typically stored in a topographic feature called a debris‐flow fan, the formation process of which governs secondary sediment transport further downstream. Although sediment transport from debris‐flow fans can impact sediment regimes and change landforms, the determinants of progressive fan formation are not well constrained. To identify such determinants, this study monitored debris flows and performed topographic surveys of debris‐flow fans in the Ichino‐sawa torrent (Japan) during 2016–2017. In this period, eight debris flows occurred, two of which eroded the existing fan and formed a new channel with a short recurrence interval (~40 days). Consequently, these two cases induced substantial sediment transport further downstream from the fan. The examined rainfall indices did not provide a threshold for diagnosing the occurrence of such sediment transport. Debris flows with a large flow depth and a long duration led to changes in the runout direction and subsequently formed new channels. Before these processes, the existing channel was backfilled and plugged by previous debris flows, forming a steep fan surface around the fan apex. The results suggest that increasing the magnitude and the duration of debris flows potentially triggers sediment transport from fans coupled with channel plugging. The annual sediment transport from the fan exceeded almost all sediment yields of the world rivers and was found comparable with that linked with volcanic eruptions and their aftermath. Thus, the fan‐formation process can induce substantial sediment transport, independent of volcanic perturbations and extreme climatic events, and is dependent on the sediment supply from repeated occurrence of debris flows in the initiation zones. [ABSTRACT FROM AUTHOR]

Earth hummocks are periglacial landforms that are widely distributed in arctic and alpine regions. This study employed an uncrewed aerial vehicle (UAV) and a structure from motion (SfM) framework to map and analyze the spatial distribution and morphological characteristics of earth hummocks across an extensive area in Daisetsuzan National Park, Japan. The UAV-captured images were processed using SfM photogrammetry to create orthomosaic images and high-resolution DEMs. We identified the distribution and morphological characteristics of earth hummocks using orthoimages, hillshade maps, and DEMs and analyzed how their morphological parameters relate to topographical conditions. A total of 18,838 individual earth hummocks in an area of approximately 82,599 m² were mapped and analyzed across the two study areas, surpassing the scale of existing studies. The average length, width, and height of these earth hummocks are 1.22 m, 1.03 m, and 0.15 m, respectively, and topographical features such as slope, aspect, and landforms are demonstrated to have an essential influence on the morphology of the earth hummocks. These findings enhance our understanding of topographical features. Furthermore, this study demonstrates the efficacy of utilizing the UAV-SfM framework with multi-directional hillshade mapping as an alternative to manual field measurements in studying periglacial landforms in mountainous regions. [ABSTRACT FROM AUTHOR]

Extraction of knickpoints or knickzones from a Digital Elevation Model (DEM) has gained immense significance owing to the increasing implications of knickzones on landform development. However, existing methods for knickzone extraction tend to be subjective or require time-intensive data processing. This paper describes the proposed Knickzone Extraction Tool (KET), a new raster-based Python script deployed in the form of an ArcGIS toolset that automates the process of knickzone extraction and is both fast and more user-friendly. The KET is based on multi-scale analysis of slope gradients along a river course, where any locally steep segment (knickzone) can be extracted as an anomalously high local gradient. We also conducted a comparative analysis of the KET and other contemporary knickzone identification techniques. The relationship between knickzone distribution and its morphometric characteristics are also examined through a case study of a mountainous watershed in Japan.

An unexpected new source of tin was recently located at Hisarcik, in the foothills of the Mount Erciyes volcano in the Kayseri Plain, close to the Bronze Age town of Kultepe, ancient Kanesh and home to a colony of Assyrian traders. Volcanoes in Turkey have always been associated with obsidian sources but were not known to be a major source of heavy metals, much less tin. X-ray fluorescence analyses of the Hisarcik ores revealed the presence of minerals suitable for the production of complex copper alloys, and sufficient tin and arsenic content to produce tin-bronze. These findings revise our understanding of bronze production in Anatolia in the third millennium BC and demand a re-evaluation of Assyrian trade routes and the position of the Early Bronze Age societies of Anatolia within that network. Keywords: Kultepe Kanesh, Bolkardag, Kestel, Anatolia, Bronze Age, pXRF, tin, trade networks, Introduction Prior to the identification of Anatolian tin, scholars argued that tin was necessarily traded into the region from Central Asia, Afghanistan or Europe for consumption in the Near East [...]

Topographical changes in riverine floodplains need to be measured for assessing geomorphological dynamics and protecting floodplain areas, although topographic evaluation in disaster-prone floodplain in South Asia has been limited due to the lack of multitemporal, high-definition digital elevation models (DEMs) derived from modern techniques including airborne laser scanning, structure-from-motion (SfM) photogrammetry accompanied with Unmanned Aerial Vehicle (UAV, often referred as drone), and field-based mapping approaches. Here we conducted a preliminary study at two locations of Teesta River (Brahmaputra's tributary) in Bangladesh using the UAV-SfM techniques and generated high-resolution DEMs. The selected locations represent dynamic changes of sediment and water on the floodplain over the years, and the UAV-SfM approach can be an effective method for monitoring those changes, but an archive of the past data has been unavailable. Here we evaluated the topographic changes by comparing the UAV-SfM-derived DEMs of 2022 with global DEM products (NASADEM of 1999), which are often the only available choice of DEMs in this river floodplain. The elevation differences of these two sets of DEMs were in the range of −5.23 to −84.66 m, and volumetric changes of −4.11 ± 0.15 to −86.25 ± 0.20 million m3, likely dominated by erosional processes towards the left side bank where the elevation errors are supposed to be several meters for UAV-DEM and ca. 5–12 m for NASADEM. Although it is not easy to accurately evaluate the absolute values of the changes, these changes may be associated with the upper basin's morphodynamics. [ABSTRACT FROM AUTHOR]

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1745-5871.2007.00431.x Byline: YUICHI S. HAYAKAWA (1), TAKASHI OGUCHI (2), JUNKO KOMATSUBARA (3), KAORI ITO (4), KAZUAKI HORI (5), YOSHIHIRO NISHIAKI (6) Keywords: laser measurement system; field survey; GIS; kriging; landforms; archaeology Abstract: Abstract A digital elevation model and a topographic map of an archaeological site in Syria were created from a field topographic survey with a handheld laser range finder and data post-processing using a notebook personal computer with Geographical Information System software. The method enabled rapid on-site topographical mapping even under technical and political restrictions in the country. In an area of about 1 km.sup.2, coordinates of random points on the land surface were measured, and a DEM with a 10 m interval grid was generated from the point cloud using Kriging interpolation. The DEM enables various topographic representations to be constructed, such as contour lines, cross sections and slope distribution maps. The DEM-derived contour lines with a 1 m interval were combined with vector data showing roads and buildings to provide a topographic map. Topographic cross sections created from the DEM generally agree with sections surveyed with a hand level and a measurement tape. The obtained DEM and map are useful for preliminary field research. Author Affiliation: (1)Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan. (2)Center for Spatial Information Science, The University of Tokyo, Chiba 277-8568, Japan. (3)Active Fault Research Center, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8561, Japan. (4)Department of Architecture, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan. (5)Department of Environmental Science and Technology, Faculty of Science and Technology, Meijo University, Aichi 468-8502, Japan. (6)The University Museum, The University of Tokyo, Tokyo 113-0033, Japan. Article History: Received 30 January 2006; Revised 21 June 2006; Accepted 27 July 2006 Article note: (*) Corresponding author. Email: hayakawa@csis.u-tokyo.ac.jp