@article{BaumhauerBuscheSponholz1989, author = {Baumhauer, Roland and Busche, Detlef and Sponholz, Barbara}, title = {Reliefgeschichte und Pal{\"a}oklima des saharischen Ost-Niger}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-55378}, year = {1989}, abstract = {Der gr{\"o}ßte Teil des zentralsaharischen Reliefs ist unter dem Einfluß nicht-arider Klimate gebildet worden. Andererseits gab es im Pleistoz{\"a}n {\"a}olisch gepr{\"a}gte aride Phasen, die extremer als heutige gewesen sind. Der Kenntnisstand zur Reliefgeschichte erlaubt es, daraus die Grundz{\"u}ge der Klimageschichte eines großen Teils der s{\"u}dlich-zentralen Sahara abzuleiten.}, subject = {Geographie}, language = {de} } @article{KanmegneTamgaLatifiUllmannetal.2023, author = {Kanmegne Tamga, Dan and Latifi, Hooman and Ullmann, Tobias and Baumhauer, Roland and Thiel, Michael and Bayala, Jules}, title = {Modelling the spatial distribution of the classification error of remote sensing data in cocoa agroforestry systems}, series = {Agroforestry Systems}, volume = {97}, journal = {Agroforestry Systems}, number = {1}, issn = {0167-4366}, doi = {10.1007/s10457-022-00791-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324139}, pages = {109-119}, year = {2023}, abstract = {Cocoa growing is one of the main activities in humid West Africa, which is mainly grown in pure stands. It is the main driver of deforestation and encroachment in protected areas. Cocoa agroforestry systems which have been promoted to mitigate deforestation, needs to be accurately delineated to support a valid monitoring system. Therefore, the aim of this research is to model the spatial distribution of uncertainties in the classification cocoa agroforestry. The study was carried out in C{\^o}te d'Ivoire, close to the Ta{\"i} National Park. The analysis followed three steps (i) image classification based on texture parameters and vegetation indices from Sentinel-1 and -2 data respectively, to train a random forest algorithm. A classified map with the associated probability maps was generated. (ii) Shannon entropy was calculated from the probability maps, to get the error maps at different thresholds (0.2, 0.3, 0.4 and 0.5). Then, (iii) the generated error maps were analysed using a Geographically Weighted Regression model to check for spatial autocorrelation. From the results, a producer accuracy (0.88) and a user's accuracy (0.91) were obtained. A small threshold value overestimates the classification error, while a larger threshold will underestimate it. The optimal value was found to be between 0.3 and 0.4. There was no evidence of spatial autocorrelation except for a smaller threshold (0.2). The approach differentiated cocoa from other landcover and detected encroachment in forest. Even though some information was lost in the process, the method is effective for mapping cocoa plantations in C{\^o}te d'Ivoire.}, language = {en} } @article{KuenzerKleinUllmannetal.2015, author = {Kuenzer, Claudia and Klein, Igor and Ullmann, Tobias and Georgiou, Efi Foufoula and Baumhauer, Roland and Dech, Stefan}, title = {Remote Sensing of River Delta Inundation: Exploiting the Potential of Coarse Spatial Resolution, Temporally-Dense MODIS Time Series}, series = {Remote Sensing}, volume = {7}, journal = {Remote Sensing}, doi = {10.3390/rs70708516}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-151552}, pages = {8516 -- 8542}, year = {2015}, abstract = {River deltas belong to the most densely settled places on earth. Although they only account for 5\% of the global land surface, over 550 million people live in deltas. These preferred livelihood locations, which feature flat terrain, fertile alluvial soils, access to fluvial and marine resources, a rich wetland biodiversity and other advantages are, however, threatened by numerous internal and external processes. Socio-economic development, urbanization, climate change induced sea level rise, as well as flood pulse changes due to upstream water diversion all lead to changes in these highly dynamic systems. A thorough understanding of a river delta's general setting and intra-annual as well as long-term dynamic is therefore crucial for an informed management of natural resources. Here, remote sensing can play a key role in analyzing and monitoring these vast areas at a global scale. The goal of this study is to demonstrate the potential of intra-annual time series analyses at dense temporal, but coarse spatial resolution for inundation characterization in five river deltas located in four different countries. Based on 250 m MODIS reflectance data we analyze inundation dynamics in four densely populated Asian river deltas-namely the Yellow River Delta (China), the Mekong Delta (Vietnam), the Irrawaddy Delta (Myanmar), and the Ganges-Brahmaputra (Bangladesh, India)-as well as one very contrasting delta: the nearly uninhabited polar Mackenzie Delta Region in northwestern Canada for the complete time span of one year (2013). A complex processing chain of water surface derivation on a daily basis allows the generation of intra-annual time series, which indicate inundation duration in each of the deltas. Our analyses depict distinct inundation patterns within each of the deltas, which can be attributed to processes such as overland flooding, irrigation agriculture, aquaculture, or snowmelt and thermokarst processes. Clear differences between mid-latitude, subtropical, and polar deltas are illustrated, and the advantages and limitations of the approach for inundation derivation are discussed.}, language = {en} } @article{MeisterGarbeTrappeetal.2021, author = {Meister, Julia and Garbe, Philipp and Trappe, Julian and Ullmann, Tobias and Es-Senussi, Ashraf and Baumhauer, Roland and Lange-Athinodorou, Eva and El-Raouf, Amr Abd}, title = {The Sacred Waterscape of the Temple of Bastet at Ancient Bubastis, Nile Delta (Egypt)}, series = {Geosciences}, volume = {11}, journal = {Geosciences}, number = {9}, issn = {2076-3263}, doi = {10.3390/geosciences11090385}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-246129}, year = {2021}, abstract = {Sacred water canals or lakes, which provided water for all kinds of purification rites and other activities, were very specific and important features of temples in ancient Egypt. In addition to the longer-known textual record, preliminary geoarchaeological surveys have recently provided evidence of a sacred canal at the Temple of Bastet at Bubastis. In order to further explore the location, shape, and course of this canal and to find evidence of the existence of a second waterway, also described by Herodotus, 34 drillings and five 2D geoelectrical measurements were carried out in 2019 and 2020 near the temple. The drillings and 2D ERT surveying revealed loamy to clayey deposits with a thickness of up to five meters, most likely deposited in a very low energy fluvial system (i.e., a canal), allowing the reconstruction of two separate sacred canals both north and south of the Temple of Bastet. In addition to the course of the canals, the width of about 30 m fits Herodotus' description of the sacred waterways. The presence of numerous artefacts proved the anthropogenic use of the ancient canals, which were presumably connected to the Nile via a tributary or canal located west or northwest of Bubastis.}, language = {en} } @article{NillUllmannKneiseletal.2019, author = {Nill, Leon and Ullmann, Tobias and Kneisel, Christof and Sobiech-Wolf, Jennifer and Baumhauer, Roland}, title = {Assessing Spatiotemporal Variations of Landsat Land Surface Temperature and Multispectral Indices in the Arctic Mackenzie Delta Region between 1985 and 2018}, series = {Remote Sensing}, volume = {11}, journal = {Remote Sensing}, number = {19}, issn = {2072-4292}, doi = {10.3390/rs11192329}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-193301}, year = {2019}, abstract = {Air temperatures in the Arctic have increased substantially over the last decades, which has extensively altered the properties of the land surface. Capturing the state and dynamics of Land Surface Temperatures (LSTs) at high spatial detail is of high interest as LST is dependent on a variety of surficial properties and characterizes the land-atmosphere exchange of energy. Accordingly, this study analyses the influence of different physical surface properties on the long-term mean of the summer LST in the Arctic Mackenzie Delta Region (MDR) using Landsat 30 m-resolution imagery between 1985 and 2018 by taking advantage of the cloud computing capabilities of the Google Earth Engine. Multispectral indices, including the Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI) and Tasseled Cap greenness (TCG), brightness (TCB), and wetness (TCW) as well as topographic features derived from the TanDEM-X digital elevation model are used in correlation and multiple linear regression analyses to reveal their influence on the LST. Furthermore, surface alteration trends of the LST, NDVI, and NDWI are revealed using the Theil-Sen (T-S) regression method. The results indicate that the mean summer LST appears to be mostly influenced by the topographic exposition as well as the prevalent moisture regime where higher evapotranspiration rates increase the latent heat flux and cause a cooling of the surface, as the variance is best explained by the TCW and northness of the terrain. However, fairly diverse model outcomes for different regions of the MDR (R2 from 0.31 to 0.74 and RMSE from 0.51 °C to 1.73 °C) highlight the heterogeneity of the landscape in terms of influential factors and suggests accounting for a broad spectrum of different factors when modeling mean LSTs. The T-S analysis revealed large-scale wetting and greening trends with a mean decadal increase of the NDVI/NDWI of approximately +0.03 between 1985 and 2018, which was mostly accompanied by a cooling of the land surface given the inverse relationship between mean LSTs and vegetation and moisture conditions. Disturbance through wildfires intensifies the surface alterations locally and lead to significantly cooler LSTs in the long-term compared to the undisturbed surroundings.}, language = {en} } @article{SchulzJosephBaumhaueretal.1990, author = {Schulz, Erhard and Joseph, Alain and Baumhauer, Roland and Schultze, Ekkerhard and Sponholz, Barbara}, title = {Upper Pleistocene and Holocene history of the Bilma region (Kawar, NE-Niger)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86828}, year = {1990}, abstract = {A 42 m drilling was pertormed in the depresalon of Bilma, Xawar, NE-Niger. The sediment and pollen records show that after an initial deposition of dune sands there were repeated lake phases which terminated by desiccation and consolidation of spring mounds. The pollen record indicates a continuous presence of savanna vegetation. The record probably covers the period between the Upper Pleistocene and the Late Holocene. The climate was characterised by a monssonal summer rain regime giving effective rain fall of about 450-500 mm per year. Groundwater recharge was possible but estimates of the amount of water resources are difficult because of the karstic system of the escarpment and the nearly unknown hydrogeological situation.}, subject = {Pleistoz{\"a}n}, language = {en} } @article{SponholzBaumhauerFelixHennignsen1993, author = {Sponholz, Barbara and Baumhauer, Roland and Felix-Hennignsen, P.}, title = {Fulgurites in the southern central Sahara, Republic of Niger and their palaeoenvironmental significance}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-63337}, year = {1993}, abstract = {The mineralogical and chemical characteristics of fulgurites ( = natural glasses forrned by lightning strikes to the ground) from the southern Centrat Sahara (Niger) are presented. The fulgurites are indicators of thunderstorms. The northernmost important fulgurite formation in the study area reached up to about l8°N, with decreasing fulgurite concentration from south to north. Their distribution pattern and the relative dating of their formation in relation to Iandscape history from the Late Pleistocene onwards (e.g., palaeolakes, palaeosols), and to Neolithic settlement reveals their value as palaeoenvironmental indicators. They indicate: (1) local palaeoenvironmental conditions depending on the topographical situation in a complex dune relief; (2) climatic change during the mid-Holocene from northerly rains to southerly rains; and (3) the northernmost Iimit of important thunderstorrns and rainfall activity since this time in the southern Centrat Sahara.}, subject = {Sahara}, language = {en} } @article{TrappeBuedelMeisteretal.2022, author = {Trappe, Julian and B{\"u}del, Christian and Meister, Julia and Baumhauer, Roland}, title = {Combining geophysical and geomorphological data to reconstruct the development of relief of a medieval castle site in the Spessart low mountain range, Germany}, series = {Earth Surface Processes and Landforms}, volume = {47}, journal = {Earth Surface Processes and Landforms}, number = {1}, doi = {10.1002/esp.5242}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257433}, pages = {228-241}, year = {2022}, abstract = {Within the Spessart low mountain range in central Germany, numerous castle ruins of the 13th century ce exist. Their construction and destruction were often determined by the struggle for political and economic supremacy in the region and for control over the Spessart's natural resources. Wahlmich Castle is located in a relatively uncommon strategic and geomorphological position, characterized by a fairly remote position and atypical rough relief. In order to reconstruct the local relief development and possible human impact, a multi-method approach was applied combining two-dimensional geoelectrical measurements, geomorphological mapping and stratigraphic-sedimentological investigations. This provides new insights into the influence of landscape characteristics on choices of castle locations. The combined geoelectrical, geomorphological and stratigraphic-sedimentological data show that the rough relief is of natural origin and influenced by regional faulting, which triggered sliding and slumping as well as weathering and dissection of the surface deposits. The rough relief and the lithology permitted intensive land use and building activities. However, the location of the castle offered access to and possibly control over important medieval traffic routes and also represented certain ownership claims in the Aschaff River valley. The economic situation combined with rivalry between different elites led to the castle being built in a geomorphological challenging and strategically less valuable location. Focusing on castles located in rare and challenging geomorphological positions may therefore lead to a better understanding of castle siting in the future.}, language = {en} } @article{UllmannBuedelBaumhaueretal.2016, author = {Ullmann, Tobias and B{\"u}del, Christian and Baumhauer, Roland and Padashi, Majid}, title = {Sentinel-1 SAR Data Revealing Fluvial Morphodynamics in Damghan (Iran): Amplitude and Coherence Change Detection}, series = {International Journal of Earth Science and Geophysics}, volume = {2}, journal = {International Journal of Earth Science and Geophysics}, number = {1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-147863}, pages = {007}, year = {2016}, abstract = {The Sentinel-1 Satellite (S-1) of ESA's Copernicus Mission delivers freely available C-Band Synthetic Aperture Radar (SAR) data that are suited for interferometric applications (InSAR). The high geometric resolution of less than fifteen meter and the large coverage offered by the Interferometric Wide Swath mode (IW) point to new perspectives on the comprehension and understanding of surface changes, the quantification and monitoring of dynamic processes, especially in arid regions. The contribution shows the application of S-1 intensities and InSAR coherences in time series analysis for the delineation of changes related to fluvial morphodynamics in Damghan, Iran. The investigations were carried out for the period from April to October 2015 and exhibit the potential of the S-1 data for the identification of surface disturbances, mass movements and fluvial channel activity in the surroundings of the Damghan Playa. The Amplitude Change Detection highlighted extensive material movement and accumulation - up to sizes of more than 4,000 m in width - in the east of the Playa via changes in intensity. Further, the Coherence Change Detection technique was capable to indicate small-scale channel activity of the drainage system that was neither recognizable in the S-1 intensity nor the multispectral Landsat-8 data. The run off caused a decorrelation of the SAR signals and a drop in coherence. Seen from a morphodynamic point of view, the results indicated a highly dynamic system and complex tempo-spatial patterns were observed that will be subject of future analysis. Additionally, the study revealed the necessity to collect independent reference data on fluvial activity in order to train and adjust the change detector.}, language = {en} } @article{UllmannMoellerBaumhaueretal.2022, author = {Ullmann, Tobias and M{\"o}ller, Eric and Baumhauer, Roland and Lange-Athinodorou, Eva and Meister, Julia}, title = {A new Google Earth Engine tool for spaceborne detection of buried palaeogeographical features - examples from the Nile Delta (Egypt)}, series = {E\&G Quaternary Science Journal}, volume = {71}, journal = {E\&G Quaternary Science Journal}, number = {2}, doi = {10.5194/egqsj-71-243-2022}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-300164}, pages = {243-247}, year = {2022}, abstract = {No abstract available.}, language = {en} }