Use of TanDEM-X and Sentinel Products to Derive Gully Activity Maps in Kunene Region (Namibia) Based on Automatic Iterative Random Forest Approach

Gullies are landforms with specific patterns of shape, topography, hydrology, vegetation, and soil characteristics. Remote sensing products (TanDEM-X, Sentinel-1, and Sentinel-2) serve as inputs into an iterative algorithm, initialized using a micromapping simulation as training data, to map gullies in the northwestern of Namibia. A Random Forest Classifier examines pixels with similar characteristics in a pool of unlabeled data, and gully objects are detected where high densities of gully pixels are enclosed by an alpha shape. Gully objects are used in subsequent iterations following a mechanism where the algorithm uses the most reliable pixels as gully training samples. The gully class continuously grows until an optimal scenario in terms of accuracy is achieved. Results are benchmarked with manually tagged gullies (initial gully labeled area <0.3% of the total study area) in two different watersheds (408 and 302 km2, respectively) yielding total accuracies of >98%, with 60% in the gully class, Cohen Kappa >0.5, Matthews Correlation Coefficient >0.5, and receiver operating characteristic Area Under the Curve >0.89. Hence, our method outlines gullies keeping low false-positive rates while the classification quality has a good balance for the two classes (gully/no gully). Results show the most significant gully descriptors as the high temporal radar signal coherence (22.4%) and the low temporal variability in Normalized Difference Vegetation Index (21.8%). This research builds on previous studies to face the challenge of identifying and outlining gully-affected areas with a shortage of training data using global datasets, which are then transferable to other large (semi-) arid regions.This research is part of the DEM_HYDR2024 project sup ported by TanDEM-X Science Team, therefore the authors would like to express thanks to the Deutsches Zentrum für Luft und Raumfahrt (DLR) as the donor for the used TanDEM-X datasets. They acknowledge the financial support provided by the Namibia University of Science and Technology (NUST) within the IRPC research funding programme and to ILMI for the sponsorship of field trips to identify suitable study areas. Finally, they would like to express gratitude toward Heidelberg University and the Kurt-Hiehle-Foundation for facilitating the suitable work conditions during this research

Heidelberger Geographiestudenten auf der Seidenstraße in China. Deutsch-chinesische Summerschool Geo-Archäologie: Niklas Schenck berichtet für Campus-TV

Auf alten Pfaden Neuland betreten haben jetzt Geographen der Universität Heidelberg. Bei einer deutsch-chinesischen Summerschool rund um das Thema „Geo-Archäologie“ gingen sie unter Leitung des Heidelberger Geographen Prof. Dr. Olaf Bubenzer an zwei archäologischen Grabungsstätten in der westchinesischen autonomen Republik Xinjiang der Frage nach, wie sich das Klima und die Landschaft in dieser Region am Rande der berühmten Seidenstraße über die Jahrtausende entwickelt haben. Dabei stand nicht nur der Technologietransfer in Form moderner Feldmethoden im Fokus. Auch der Austausch zwischen den Wissenschaftlern und den Studierenden aus beiden Ländern sollte gefördert werden. Für Campus-TV hatte der Geographiestudent und Journalist Niklas Schenck eine Kamera mitgenommen und schildert in einem farbigen Bericht die Erlebnisse des deutsch-chinesischen Teams. Damit Wissenschaft und Bildung Früchte tragen können, muss man vor Ort ins Gelände. Für diese Feldarbeit brachten sich 20 deutsche und 20 chinesische Teilnehmer in der Summerschool ein. Zwei Jahre Vorarbeit hat Professor Bubenzer in diese Summerschool gesteckt, seit Professor Cheng-Sen Li, ein Paläobotaniker von der Akademie der Wissenschaften aus Peking, bei einem Besuch in Heidelberg 2007 die Idee dazu hatte. Als lokale Partner wurden die Archäologen der Academia Turfanica gewonnen. Niklas Schenck kann von kleinen künstlichen Erdbeben berichten, von datierbaren Knochen, die man in sogenannten „Bodenhorizonten“ gefunden hat, von Bohrungen und Widerstandsmessungen, mit denen man die Sedimentschichten in der Tiefe untersuchte, und von der Plackerei mit rund einer Tonne Expeditionsgepäck. Aus China nehmen die Heidelberger Geographen nicht nur ihre Teilnahmeurkunden mit nach Hause, sondern gleich einen ganzen Koffer voller Freundschaften und Erfahrungen – eine Fortsetzung soll die Kooperation schon ab 2010 in einer internationalen Konferenz und einem groß angelegten Forschungsprojekt finden. (Campus-TV, Mannheim, 1. Oktober 2009

Geoinformatics application for assessing the potential of rainwater harvesting in arid regions. Case study: El Daba'a area, Northwestern Coast of Egypt

In the light of the current situation of water resources in Egypt, where it has a deficit in those resources, the rainwater harvesting and assessment of its potentialities became necessary. In the present study, an attempt is made to define a decision based on scientific approach for identifying the most appropriate sites for rainwater harvesting. This approach is based on GIS data layers which include DEM, landforms, geologic setting, watershed area, rainfall amounts, drainage lines, morphometric parameters, flow accumulation, flow direction, slope, and surface runoff. It also includes a verification of the site suitability through field investigations. El Daba'a area has been chosen because it has a lack of water for agriculture and drinking purposes. In addition, this area has special interest because of a planned nuclear power plant there. The obtained results reveal that the study area contains eight basins which have slightly intensive drainage network. The morphometric analyses of the studied basins reveal their opportunities for surface runoff. Three of them are showing high hazard degrees. These basins have actual runoff (Q) ranges between 16.5 and 25 mm annually resulted from average rainfall of 164 mm. Therefore, management of rainwater harvesting and protections from flash floods were recommended. Many rainwater harvesting structures, for example concert dams, alternative earth dikes, surface water reservoirs, and cisterns, should be established

Capturing complex star dune dynamics—repeated highly accurate surveys combining multitemporal 3D topographic measurements and local wind data

Morphologies of highly complex star dunes are the result of aeolian dynamics in past and present times. These dynamics reflect climatic conditions and associated forces like sediment availability and vegetation cover, as well as feedbacks with adjacent environments. However, an understanding of aeolian dynamics on star dune morphometries is still lacking sufficient detail, and their influence on formation and evolution remains unclear. We therefore investigate the dynamics of a complex star dune (Erg Chebbi, Morocco) by analysing wind measurements compared to morphometric changes derived from multitemporal high‐accuracy 3D observations during two surveys (October 2018 and February 2020). Using real‐time kinematic global navigation satellite system (RTK‐GNSS) measurements and terrestrial laser scanning (TLS), the reaction of a star dune surface to an observed constant unimodal sand‐moving wind is presented. TLS point clouds are used for morphometric analysis as well as direct surface change analysis, which relates to sand transport. RTK‐GNSS measurements enable the assessment of horizontal crest movement. Observed surface changes lead to the identification of an overall shielding effect, resulting in sand accumulation mainly on windward slopes. Our results point to a self‐sustained dune growth, which has not yet been described in such spatial detail. Steep slopes, often found on star dunes around the globe, seem to partly hinder upslope sand transport. Though a comparatively short observation period, we therefore hypothesize that, besides wind intensity alone, slope angles are more decisive for sand transport than previously assumed. Our methodological approach of combining meteorological data and high‐resolution multitemporal 3D elevation models can be used for monitoring all dune forms and contributes to a general understanding of dune dynamics and evolution.The accurate detection of altitudinal surface changes on a star dune compared to climatic data enables the identification of aeolian dynamics and new mechanisms where, besides wind intensity alone, slope angles are more decisive for sand transport than previously assumed. The methodological approach can be transferred to all dune forms, ranging from small barchans to complex and extensive star dunes.https://doi.org/10.11588/data/ZAMGC

Klimaforschung auf der Seidenstrasse : Studenten aus Heidelberg und China forschen gemeinsam am Thema Erderwärmung

"Campus-Report" heißt die Radiosendung der Universitäten Heidelberg, Mannheim, Karlsruhe und Freiburg. Die Reportagen über aktuelle Themen aus Forschung und Wissenschaft werden montags bis freitags jeweils um ca. 19.10h im Programm von Radio Regenbogen gesendet. (Empfang in Nordbaden: UKW 102,8. In Mittelbaden: 100,4 und in Südbaden: 101,1) Uni-Radio Baden: ein gemeinsames Projekt der Universitäten Freiburg, Heidelberg, Karlsruhe und Mannheim in Zusammenarbeit mit Radio Regenbogen – unterstützt von der Landesanstalt für Kommunikation. Sendung vom 25. November 200

Palaeohydrology and its impact on groundwater in arid environments: Gebel Duwi and its vicinities, Eastern Desert, Egypt

From ancient times, access to water in arid and hyper-arid regions has been crucial for life. Increased knowledge about groundwater conditions is therefore extremely important for the future development of desert areas. Gebel Duwi, a limestone ridge, sited in the today hyper-arid Eastern Desert of Egypt, was chosen for testing current hypotheses concerning the interdependence of palaeohydrologic features and geologic settings for groundwater investigations. Two sub-basins are identified in affecting Gebel Duwi: Wadi Nakheil and Wadi Sodmein. Both have extraordinary high stream order, indicating the reality of a very old drainage system. Several additional palaeohydrologic features such as wadi terraces, alluvial fans, and playa deposits are also recorded in these sub-basins. These features, as well as finds from an important archaeological site (Sodmein Cave), provide information about palaeoenvironmental changes and wetter climatic periods in the younger geologic past, mainly in the Late Pleistocene and Holocene, which have affected the occurrence of present day groundwater. This study combines new results of geological and geomorphological field studies, examinations of digital elevation models, as well as of rock and water analyses in an integrated approach. Resulting maps comprise landforms, lithology, elevation, drainage lines slope, structural lineaments and flow directions. The hydrogeologic condition indicates suitable locations for groundwater recharge and accumulation. The research presented is interdisciplinary in approach and is recommended for future studies with regard to groundwater exploration, sustainable groundwater use, and the protection of archaeological sites in arid lands